Searching for Variability of NV Intrinsic Narrow Absorption Line Systems

NASA Astrophysics Data System (ADS)

Rodruck, Michael; Charlton, Jane; Ganguly, Rajib

2018-01-01

The majority of quasar absorption line systems with NV detected are found within the associated region (within 5000 km/s of the quasar redshift) and many/most are believed to be related to the quasar accretion disk wind or outflows. The most definite evidence that these NV absorbers are "intrinsic" is partial covering of the quasar continuum source and/or broad line region. Over 75 quasars containing NV narrow absorption lines have observations obtained at different times with the Keck/HIRES and the VLT/UVES spectrographs at high resolution. The interval between these observations range from months to a decade in the quasar rest frame. While variability is common for intrinsic broad and mini-broad absorption lines, intrinsic narrow absorption lines have been found to be less likely to vary, though systematic studies with large, high quality datasets have been limited. The variability timescales are useful for deriving gas densities and thus the distances from the central engines. This is important in mapping the quasar surroundings, understanding the accretion disk wind mechanism, and assessing the effect the wind has on the galaxy surroundings. We report on the results of a systematic study of variability of NV NALs, exploiting the overlap of targets for observations in the archives of Keck and VLT, and discuss the consequences for interpretation of the origin of intrinsic narrow absorption lines.

Method of LSD profile asymmetry for estimating the center of mass velocities of pulsating stars

NASA Astrophysics Data System (ADS)

Britavskiy, Nikolay; Pancino, Elena; Romano, Donatella; Tsymbal, Vadim

2015-08-01

We present radial velocity analysis for 20 solar neighborhood RR Lyrae and 3 Population II Cepheids. High-resolution spectra were observed with either TNG/SARG or VLT/UVES over varying phases. To estimate the center of mass (barycentric) velocities of the program stars, we utilized two independent methods. First, the 'classic' method was employed, which is based on RR Lyrae radial velocity curve templates. Second, we provide the new method that used absorption line profile asymmetry to determine both the pulsation and the barycentric velocities even with a low number of high-resolution spectra and in cases where the phase of the observations is uncertain. This new method is based on a Least Squares Deconvolution (LSD) of the line profiles in order to analyze line asymmetry that occurs in the spectra of pulsating stars. By applying this method to our sample stars we attain accurate measurements (± 1 km/s) of the pulsation component of the radial velocity. This results in determination of the barycentric velocity to within 5 km/s even with a low number of high-resolution spectra. A detailed investigation of LSD profile asymmetry shows the variable nature of the project factor at different pulsation phases, which should be taken into account in the detailed spectroscopic analysis of pulsating stars.

Method of LSD profile asymmetry for estimating the center of mass velocities of pulsating stars

NASA Astrophysics Data System (ADS)

Britavskiy, N.; Pancino, E.; Tsymbal, V.; Romano, D.; Cacciari, C.; Clementini, C.

2016-05-01

We present radial velocity analysis for 20 solar neighborhood RR Lyrae and 3 Population II Cepheids. High-resolution spectra were observed with either TNG/SARG or VLT/UVES over varying phases. To estimate the center of mass (barycentric) velocities of the program stars, we utilized two independent methods. First, the 'classic' method was employed, which is based on RR Lyrae radial velocity curve templates. Second, we provide the new method that used absorption line profile asymmetry to determine both the pulsation and the barycentric velocities even with a low number of high-resolution spectra and in cases where the phase of the observations is uncertain. This new method is based on a least squares deconvolution (LSD) of the line profiles in order to an- alyze line asymmetry that occurs in the spectra of pulsating stars. By applying this method to our sample stars we attain accurate measurements (+- 2 kms^-1) of the pulsation component of the radial velocity. This results in determination of the barycentric velocity to within 5 kms^-1 even with a low number of high- resolution spectra. A detailed investigation of LSD profile asymmetry shows the variable nature of the project factor at different pulsation phases, which should be taken into account in the detailed spectroscopic analysis of pulsating stars.

Successful "First Light" for VLT High-Resolution Spectrograph

NASA Astrophysics Data System (ADS)

1999-10-01

Great Research Prospects with UVES at KUEYEN A major new astronomical instrument for the ESO Very Large Telescope at Paranal (Chile), the UVES high-resolution spectrograph, has just made its first observations of astronomical objects. The astronomers are delighted with the quality of the spectra obtained at this moment of "First Light". Although much fine-tuning still has to be done, this early success promises well for new and exciting science projects with this large European research facility. Astronomical instruments at VLT KUEYEN The second VLT 8.2-m Unit Telescope, KUEYEN ("The Moon" in the Mapuche language), is in the process of being tuned to perfection before it will be "handed" over to the astronomers on April 1, 2000. The testing of the new giant telescope has been successfully completed. The latest pointing tests were very positive and, from real performance measurements covering the entire operating range of the telescope, the overall accuracy on the sky was found to be 0.85 arcsec (the RMS-value). This is an excellent result for any telescope and implies that KUEYEN (as is already the case for ANTU) will be able to acquire its future target objects securely and efficiently, thus saving precious observing time. This work has paved the way for the installation of large astronomical instruments at its three focal positions, all prototype facilities that are capable of catching the light from even very faint and distant celestial objects. The three instruments at KUEYEN are referred to by their acronyms UVES , FORS2 and FLAMES. They are all dedicated to the investigation of the spectroscopic properties of faint stars and galaxies in the Universe. The UVES instrument The first to be installed is the Ultraviolet Visual Echelle Spectrograph (UVES) that was built by ESO, with the collaboration of the Trieste Observatory (Italy) for the control software. Complete tests of its optical and mechanical components, as well as of its CCD detectors and of the complex control system, cf. ESO PR Photos 44/98 , were made in the laboratories of the ESO Headquarters in Garching (Germany) before it was fully dismounted and shipped (some parts by air, others by ship) to the ESO Paranal Observatory, 130 km south of Antofagasta (Chile). Here, the different pieces of UVES (with a total weight of 8 tons) were carefully reassembled on the Nasmyth platform of KUEYEN and made ready for real observations (see ESO PR Photos 36p-t/99 ). UVES is a complex two-channel spectrograph that has been built around two giant optical (echelle diffraction) gratings, each ruled on a 84 cm x 21 cm x 12 cm block of the ceramic material Zerodur (the same that is used for the VLT 8.2-m main mirrors) and weighing more than 60 kg. These echelle gratings finely disperse the light from celestial objects collected by the telescope into its constituent wavelengths (colours). UVES' resolving power (an optical term that indicates the ratio between a given wavelength and the smallest wavelength difference between two spectral lines that are clearly separated by the spectrograph) may reach 110,000, a very high value for an astronomical instrument of such a large size. This means for instance that even comparatively small changes in radial velocity (a few km/sec only) can be accurately measured and also that it is possible to detect the faint spectral signatures of very rare elements in celestial objects. One UVES channel is optimized for the ultraviolet and blue, the other for visual and red light. The spectra are digitally recorded by two highly efficient CCD detectors for subsequent analysis and astrophysical interpretation. By optimizing the transmission of the various optical components in its two channels, UVES has a very high efficiency all the way from the UV (wavelength about 300 nm) to the near-infrared (1000 nm or 1 µm). This guarantees that only a minimum of the precious light that is collected by KUEYEN is lost and that detailed spectra can be obtained of even quite faint objects, down to about magnitude 20 (corresponding to nearly one million times fainter than what can be perceived with the unaided eye). The possibility of doing simultaneous observations in the two channels (with a dichroic mirror) ensures a further gain in data gathering efficiency. First Observations with UVES In the evening of September 27, 1999, the ESO astronomers turned the KUEYEN telescope and - for the first time - focussed the light of stars and galaxies on the entrance aperture of the UVES instrument. This is the crucial moment of "First Light" for a new astronomical facility. The following test period will last about three weeks. Much of the time during the first observing nights was spent by functional tests of the various observation modes and by targeting "standard stars" with well-known properties in order to measure the performance of the new instrument. They showed that it is behaving very well. This marks the beginning of a period of progressive fine-tuning that will ultimately bring UVES to peak performance. The astronomers also did a few "scientific" observations during these nights, aimed at exploring the capabilities of their new spectrograph. They were eager to do so, also because UVES is the first spectrograph of this type installed at a telescope of large diameter in the southern hemisphere . Many exciting research possibilities are now opening with UVES . They include a study of the chemical history of many galaxies in the Local Group, e.g. by observing the most metal-poor (oldest) stars in the Milky Way Galaxy and by obtaining the first, extremely detailed spectra of their brightest stars in the Magellanic Clouds. Quasars and distant compact galaxies will also be among the most favoured targets of the first UVES observers, not least because their spectra carry crucial information about the density, physical state and chemical composition of the early Universe. UVES First Light: SN 1987A One of the first spectral test exposures with UVES at KUEYEN was of SN 1987A , the famous supernova that exploded in the Large Magellanic Cloud (LMC) in February 1987, and the brightest supernova of the last 400 years. ESO PR Photo 37a/99 ESO PR Photo 37a/99 [Preview - JPEG: 400 x 455 pix - 87k] [Normal - JPEG: 645 x 733 pix - 166k] Caption to ESO PR Photo 37a/99 : This is a direct image of SN1987A, flanked by two nearby stars. The distance between these two is 4.5 arcsec. The slit (2.0 arcsec wide) through which the echelle spectrum shown in PR Photo 37b/99 was obtained, is outlined. This reproduction is from a 2-min exposure through a R(ed) filter with the FORS1 multi-mode instrument at VLT ANTU, obtained in 0.55 arcsec seeing on September 20, 1998. North is up and East is left. ESO PR Photo 37b/99 ESO PR Photo 37b/99 [Preview - JPEG: 400 x 459 pix - 130k] [Normal - JPEG: 800 x 917 pix - 470k] [High-Res - JPEG: 3000 x 3439 pix - 6.5M] Caption to ESO PR Photo 37b/99 : This shows the raw image, as read from the CCD, with the recorded echelle spectrum of SN1987A. With this technique, the supernova spectrum is divided into many individual parts ( spectral orders , each of which appears as a narrow horizontal line) that together cover the wavelength interval from 479 to 682 nm (from the bottom to the top), i.e. from blue to red light. Many bright emission lines from different elements are visible, e.g. the strong H-alpha line from hydrogen near the centre of the fourth order from the top. Emission lines from the terrestrial atmosphere are seen as vertical bright lines that cover the full width of the individual horizontal bands. Since this exposure was done with the nearly Full Moon above the horizon, an underlying, faint absorption-line spectrum of reflected sunlight is also visible. The exposure time was 30 min and the seeing conditions were excellent (0.5 arcsec). ESO PR Photo 37c/99 ESO PR Photo 37c/99 [Preview - JPEG: 400 x 355 pix - 156k] [Normal - JPEG: 800 x 709 pix - 498k] [High-Res - JPEG: 1074 x 952 pix - 766k] Caption to ESO PR Photo 37c/99 : This false-colour image has been extracted from another UVES echelle spectrum of SN 1987A, similar to the one shown in PR Photo 37b/99 , but with a slit width of 1 arcsec only. The upper part shows the emission lines of nitrogen, sulfur and hydrogen, as recorded in some of the spectral orders. The pixel coordinates (X,Y) in the original frame are indicated; the red colour indicates the highest intensities. Below is a more detailed view of the complex H-alpha emission line, with the corresponding velocities and the position along the spectrograph slit indicated. Several components of this line can be distinguished. The bulk of the emission (here shown in red colour) comes from the ring surrounding the supernova; the elongated shape here is due to the differential velocity exhibited by the near (to us) and far sides of the ring. The two bright spots on either side are emission from two outer rings (not immediately visible in PR Photo 37a/99 ). The extended emission in the velocity direction originates from material inside the ring upon which the fastest moving ejecta from the supernova have impacted (As seen in VLT data obtained previously with the ANTU/ISAAC combination (cf. PR Photo 11/99 ), exciting times now lie ahead for SN 1987A. The ejecta moving at 30,000 km/s (1/10th the speed of light) have now, 12 years after the explosion, reached the ring of material and the predicted "fireworks" are about to be ignited.) Finally, there is a broad emission extending all along the spectrograph slit (here mostly yellow) upon which the ring emission is superimposed. This is not associated with the supernova itself, but is H-alpha emission by diffuse gas in the Large Magellanic Cloud (LMC) in which SN 1987A is located. UVES First Light: QSO HE2217-2818 The power of UVES is demonstrated by this two-hour test exposure of the southern quasar QSO HE2217-2818 with U-magnitude = 16.5 and a redshift of z = 2.4. It was discovered a few years ago during the Hamburg-ESO Quasar Survey , by means of photographic plates taken with the 1-m ESO Schmidt Telescope at La Silla, the other ESO astronomical site in Chile. ESO PR Photo 37d/99 ESO PR Photo 37d/99 [Preview - JPEG: 400 x 309 pix - 92k] [Normal - JPEG: 800x 618 pix - 311k] [High-Res - JPEG: 3000 x 2316 pix - 5.0M] ESO PR Photo 37e/99 ESO PR Photo 37e/99 [Preview - JPEG: 400 x 310 pix - 43k] [Normal - JPEG: 800 x 619 pix - 100k] [High-Res - JPEG: 3003 x 2324 pix - 436k] Caption to ESO PR Photo 37d/99 : This UVES echelle spectrum QSO HE2217-2818 (U-magnitude = 16.5) is recorded in different orders (the individual horizontal lines) and altogether covers the wavelength interval between 330 - 450 nm (from the bottom to the top). It illustrates the excellent capability of UVES to work in the UV-band on even faint targets. Simultaneously with this observation, UVES also recorded the adjacent spectral region 465 - 660 nm in its other channel. The broad Lyman-alpha emission from ionized hydrogen associated with the powerful energy source of the QSO is seen in the upper half of the spectrum at wavelength 413 nm. At shorter wavelengths, the dark regions in the spectrum are Lyman-alpha absorption lines from intervening, neutral hydrogen gas located along the line-of-sight at different redshifts (the so-called Lyman-alpha forest ) in the redshift interval z = 1.7 - 2.4. Note that since this exposure was done with the nearly Full Moon above the horizon, an underlying, faint absorption-line spectrum of reflected sunlight is also visible. Caption to ESO PR Photo 37e/99 : A tracing of one spectral order, corresponding to one horizontal line in the echelle spectrum displayed in PR Photo 37d/99 . It shows part of the Lyman-alpha forest in the ultraviolet spectrum of the southern quasar QSO HE2217-2818 . The absorption lines are caused by intervening, neutral hydrogen gas located at different distances along the line-of-sight towards this quasar. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

On the origin of [Ne II] emission in young stars: mid-infrared and optical observations with the Very Large Telescope

NASA Astrophysics Data System (ADS)

Baldovin-Saavedra, C.; Audard, M.; Carmona, A.; Güdel, M.; Briggs, K.; Rebull, L. M.; Skinner, S. L.; Ercolano, B.

2012-07-01

Context. The [Ne II] line 12.81 μm was proposed to be a good tracer of gas in the environments of proto-planetary disks; its origin is explained by different mechanisms: jets in outflows, photo-evaporative disk winds driven by stellar X-rays/EUV or by the X-ray irradiated proto-planetary disk atmosphere. Previous Spitzer studies gave hints toward the neon emitting mechanism by exploring correlations between the line luminosity and properties of the star-disk system. These studies concluded that the origin of the emission is likely related to accretion and outflows, with some influence from X-rays. Aims: We provide direct constraints on the origin of the [Ne II] emission using high-spatial and spectral resolution observations that allow us to study the kinematics of the emitting gas. In addition we compare the [Ne II] line with optical forbidden lines. Methods: We obtained high-resolution ground-based observations with VISIR-VLT for 15 stars and UVES-VLT for three of them. The stars were chosen for having bright neon emission lines detected with Spitzer/IRS. The velocity shifts and profiles are used to disentangle the different emitting mechanisms producing the [Ne II] line. A comparison between results from this study and previous high-resolution studies is also presented. Results: The [Ne II] line was detected in seven stars, among them the first confirmed detection of [Ne II] in a Herbig Be star, V892 Tau. In four cases, the large blueshifted lines indicate an origin in a jet. In two stars, the small shifts and asymmetric profiles indicate an origin in a photo-evaporative wind. CoKu Tau 1, seen close to edge-on, shows a spatially unresolved line centered at the stellar rest velocity, although cross-dispersion centroids move within 10 AU from one side of the star to the other as a function of wavelength. The line profile is symmetric with wings extending up to ~±80 km s-1. The origin of the [Ne II] line is unclear and could either be due to the bipolar jet or to the disk. For the stars with VLT-UVES observations, in several cases, the optical forbidden line profiles and shifts are very similar to the profile of the [Ne II] line, suggesting that the lines are emitted in the same region. A general trend observed with VISIR is a lower line flux when compared with the fluxes obtained with Spitzer. We found no correlation between the line full-width at half maximum and the line peak velocity. The [Ne II] line remains undetected in a large part of the sample, an indication that the emission detected with Spitzer in those stars is likely extended. Based on observations made with ESO Telescopes Kueyen/UT2 and Melipal/UT3 at the Paranal Observatory under programs ID 083.C-0471, 084.C-1062, 086.C-0911, and 286.C-5038.Appendix A is available in electronic form at http://www.aanda.org

16 years of airglow measurement with astronomical facilities

NASA Astrophysics Data System (ADS)

Kausch, Wolfgang; Noll, Stefan; Kimeswenger, Stefan; Unterguggenberger, Stefanie; Jones, Amy; Proxauf, Bastian

2017-04-01

Observations taken with ground-based astronomical telescopes are affected by various airglow emission processes in the Earth's upper atmosphere. This chemiluminescent emission can be used to investigate the physical state of the meso- and the thermosphere. By applying a modified approach of techniques originally developed to characterise and remove these features from the astronomical spectra, which are not primarily taken for airglow studies, these spectra are suitable for airglow research. For our studies, we currently use data from two observing sites on both hemispheres for our studies: The European Southern Observatory operates four 8m telescopes at the Very Large Telescope (VLT) in the Chilean Atacama desert (24.6°S, 70.4°W). The 2.5m Sloan Digital Sky Survey telescope (SDSS) located in New Mexico/USA (32.8°N, 105.8°W) provides observations from the northern hemisphere. Each of these telescopes is equipped with several astronomical instruments. Among them are several spectrographs operating in the optical and near-IR regime with medium to high spectral resolution. Currently, we work on data from the following three spectrographs (1) UVES@VLT (Ultraviolet and Visual Echelle Spectrograph): This instrument provides spectra in the wavelength regime from 0.3 to 1.1μm in small spectral ranges. Its high resolving power (up to R˜110 000) allows a detailed study of oxygen (OI@557nm, OI@630nm), sodium (NaD@589nm), nitrogen (NI@520nm), and many OH bands. UVES has been in operation since 1999 providing the longest time series. (2) X-Shooter@VLT: This spectrograph is unique as it provides the whole wavelength range from 0.3 to 2.5μm at once with medium resolving power (R˜3 300 to 18 000, depending on the setup). This enables us to study the dependency of optical and near-IR airglow processes simultaneously, e.g. the OH bands. In addition, weak airglow continuum emission, e.g. arising from FeO and NiO can be studied. In operation since 2009, the data cover half a solar cycle. (3) MaNGA spectrograph@SDSS: This instrument combines two spectrographs covering the wavelength range from 0.36 to 1.03μm with a resolving power of R˜2 000. It is equipped with a multi-fibre device and is used for this specific survey that started in 2014 (aimed to finish in 2020). In this poster we give an overview on the status of the project, some first results, and an outlook.

VizieR Online Data Catalog: Faint emission lines in M16, M20, NGC 3603 (Garcia-Rojas+, 2006)

NASA Astrophysics Data System (ADS)

Garcia-Rojas, J.; Esteban, C.; Peimbert, M.; Costado, M. T.; Rodriguez, M.; Peimbert, A.; Ruiz, M. T.

2006-10-01

The observations were made on 2003 March 29, 30 and 31 with UVES, at the VLT Kueyen Telescope in Cerro Paranal Observatory (Chile). We used the standard settings in both the red and blue arms of the spectrograph, covering the spectral region from 3100 to 10400{AA}. (1 data file).

Chemical characterisation of the globular cluster NGC 5634 associated to the Sagittarius dwarf spheroidal galaxy

NASA Astrophysics Data System (ADS)

Carretta, E.; Bragaglia, A.; Lucatello, S.; D'Orazi, V.; Gratton, R. G.; Donati, P.; Sollima, A.; Sneden, C.

2017-04-01

As part of our on-going project on the homogeneous chemical characterisation of multiple stellar populations in globular clusters (GCs), we studied NGC 5634, associated to the Sagittarius dwarf spheroidal galaxy, using high-resolution spectroscopy of red giant stars collected with VLT/FLAMES. We present here the radial velocity distribution of the 45 observed stars, 43 of which are cluster members, the detailed chemical abundance of 22 species for the seven stars observed with UVES-FLAMES, and the abundance of six elements for stars observed with GIRAFFE. On our homogeneous UVES metallicity scale, we derived a low-metallicity [Fe/H] =-1.867 ± 0.019 ± 0.065 dex (±statistical ±systematic error) with σ = 0.050 dex (7 stars). We found the normal anticorrelations between light elements (Na and O, Mg and Al), a signature of multiple populations typical of massive and old GCs. We confirm the associations of NGC 5634 to the Sgr dSph, from which the cluster was lost a few Gyr ago, on the basis of its velocity and position, and the abundance ratios of α and neutron capture elements. Based on observations collected at ESO telescopes under programme 093.B-0583.Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A118

VizieR Online Data Catalog: Abundances of metal-poor star HD 94028 (Roederer+, 2016)

NASA Astrophysics Data System (ADS)

Roederer, I. U.; Karakas, A. I.; Pignatari, M.; Herwig, F.

2016-06-01

We use two NUV spectroscopic data sets of HD 94028 available in the Mikulski Archive for Space Telescopes. These observations were made using STIS on board the HST. One spectrum (data sets O5CN01-03, GO-8197, PI. Duncan) has very high spectral resolution (R~110000). This spectrum covers ~1885-2147Å with signal-to-noise ratios (S/N)35/1 per pixel near 2140Å. The other spectrum (data sets O56D06-07, GO-7402, PI. Peterson) has high spectral resolution (R~30000). This spectrum covers 2280-3117Å with S/N ranging from ~20 near 2300Å to ~40 near 3100Å. Roederer et al. (2014, J/AJ/147/136) derived abundances from an optical spectrum of HD 94028 taken using the Robert G. Tull Coude Spectrograph on the Harlan J. Smith Telescope at McDonald Observatory, Texas. We rederive abundances from this spectrum. We also use an optical spectrum taken with the Ultraviolet and Visual Echelle Spectrograph (UVES) on the Very Large Telescope (VLT) Kueyen at Cerro Paranal, Chile. We obtained this spectrum from the ESO Science Archive. This spectrum covers 3050-3860Å at R~37000 with S/N ranging from ~40 near 3200Å to ~130 near 3800Å. (3 data files).

Isotopic ratios in outbursting comet C/2015 ER61

NASA Astrophysics Data System (ADS)

Yang, Bin; Hutsemékers, Damien; Shinnaka, Yoshiharu; Opitom, Cyrielle; Manfroid, Jean; Jehin, Emmanuël; Meech, Karen J.; Hainaut, Olivier R.; Keane, Jacqueline V.; Gillon, Michaël

2018-02-01

Isotopic ratios in comets are critical to understanding the origin of cometary material and the physical and chemical conditions in the early solar nebula. Comet C/2015 ER61 (PANSTARRS) underwent an outburst with a total brightness increase of 2 magnitudes on the night of 2017 April 4. The sharp increase in brightness offered a rare opportunity to measure the isotopic ratios of the light elements in the coma of this comet. We obtained two high-resolution spectra of C/2015 ER61 with UVES/VLT on the nights of 2017 April 13 and 17. At the time of our observations, the comet was fading gradually following the outburst. We measured the nitrogen and carbon isotopic ratios from the CN violet (0, 0) band and found that 12C/13C = 100 ± 15, 14N/15N = 130 ± 15. In addition, we determined the 14N/15N ratio from four pairs of NH2 isotopolog lines and measured 14N/15N = 140 ± 28. The measured isotopic ratios of C/2015 ER61 do not deviate significantly from those of other comets.

Controlled by Distant Explosions

NASA Astrophysics Data System (ADS)

2007-03-01

VLT Automatically Takes Detailed Spectra of Gamma-Ray Burst Afterglows Only Minutes After Discovery A time-series of high-resolution spectra in the optical and ultraviolet has twice been obtained just a few minutes after the detection of a gamma-ray bust explosion in a distant galaxy. The international team of astronomers responsible for these observations derived new conclusive evidence about the nature of the surroundings of these powerful explosions linked to the death of massive stars. At 11:08 pm on 17 April 2006, an alarm rang in the Control Room of ESO's Very Large Telescope on Paranal, Chile. Fortunately, it did not announce any catastrophe on the mountain, nor with one of the world's largest telescopes. Instead, it signalled the doom of a massive star, 9.3 billion light-years away, whose final scream of agony - a powerful burst of gamma rays - had been recorded by the Swift satellite only two minutes earlier. The alarm was triggered by the activation of the VLT Rapid Response Mode, a novel system that allows for robotic observations without any human intervention, except for the alignment of the spectrograph slit. ESO PR Photo 17a/07 ESO PR Photo 17a/07 Triggered by an Explosion Starting less than 10 minutes after the Swift detection, a series of spectra of increasing integration times (3, 5, 10, 20, 40 and 80 minutes) were taken with the Ultraviolet and Visual Echelle Spectrograph (UVES), mounted on Kueyen, the second Unit Telescope of the VLT. "With the Rapid Response Mode, the VLT is directly controlled by a distant explosion," said ESO astronomer Paul Vreeswijk, who requested the observations and is lead-author of the paper reporting the results. "All I really had to do, once I was informed of the gamma-ray burst detection, was to phone the staff astronomers at the Paranal Observatory, Stefano Bagnulo and Stan Stefl, to check that everything was fine." The first spectrum of this time series was the quickest ever taken of a gamma-ray burst afterglow, let alone with an instrument such as UVES, which is capable of splitting the afterglow light with uttermost precision. What is more, this amazing record was broken less than two months later by the same team. On 7 June 2006, the Rapid-Response Mode triggered UVES observations of the afterglow of an even more distant gamma-ray source a mere 7.5 minutes after its detection by the Swift satellite. Gamma-ray bursts are the most intense explosions in the Universe. They are also very brief. They randomly occur in galaxies in the distant Universe and, after the energetic gamma-ray emission has ceased, they radiate an afterglow flux at longer wavelengths (i.e. lower energies). They are classified as long and short bursts according to their duration and burst energetics, but hybrid bursts have also been discovered (see ESO PR 49/06). The scientific community agrees that gamma-ray bursts are associated with the formation of black holes, but the exact nature of the bursts remains enigmatic. ESO PR Photo 17b/07 ESO PR Photo 17b/07 Kueyen at Night Because a gamma-ray burst typically occurs at very large distances, its optical afterglow is faint. In addition, it fades very rapidly: in only a few hours the optical afterglow brightness can fade by as much as a factor of 500. This makes detailed spectral analysis possible only for a few hours after the gamma-ray detection, even with large telescopes. During the first minutes and hours after the explosion, there is also the important opportunity to observe time-dependent phenomena related to the influence of the explosion on its surroundings. The technical challenge therefore consists of obtaining high-resolution spectroscopy with 8-10 m class telescopes as quickly as possible. "The afterglow spectra provide a wealth of information about the composition of the interstellar medium of the galaxy in which the star exploded. Some of us even hoped to characterize the gas in the vicinity of the explosion," said team member Cédric Ledoux (ESO). ESO PR Photo 17c/07 ESO PR Photo 17c/07 The Kueyen Control Room The Rapid Response Mode UVES observations of 17 April 2006 allowed the astronomers to discover variable spectral features associated with a huge gas cloud in the host galaxy of the gamma-ray burst. The cloud was found to be neutral but excited by the radiation from the UV afterglow light. From detailed modelling of these observations, the astronomers were able - for the first time - to not only pinpoint the physical mechanism responsible for the excitation of the atoms, but also determine the distance of the cloud to the GRB. This distance was found to be 5,500 light-years, which is much further out than was previously thought. Either this is a special case, or the common picture that the features seen in optical spectra originate very close to the explosion has to be revised. As a comparison, this distance of 5,500 light-years is more than one fifth of that between the Sun and the centre of our Galaxy. "All the material in this region of space must have been ionised, that is, the atoms have been stripped of most if not all of their electrons," said co-author Alain Smette (ESO). "Were there any life in this region of the Universe, it would most probably have been eradicated." "With the Rapid-Response Mode of the VLT, we are really looking at gamma-ray bursts as quickly as possible," said team member Andreas Jaunsen from the University of Oslo (Norway). "This is crucial if we are to unravel the mysteries of these gigantic explosions and their links with black holes!" More Information The two gamma-ray bursts were discovered with the NASA/ASI/PPARC Swift satellite, which is dedicated to the discovery of these powerful cosmic explosions. Preliminary reports on these observations have been presented in GCN GRB Observation Reports 4974 and 5237. A paper is also in press in the journal Astronomy & Astrophysics ("Rapid-Response Mode VLT/UVES spectroscopy of GRB 060418 - Conclusive evidence for UV pumping from the time evolution of Fe II and Ni II excited- and metastable-level populations" by P. M. Vreeswijk et al.). DOI: 10.1051/0004-6361:20066780 The team is composed of Paul Vreeswijk, Cédric Ledoux, Alain Smette, Andreas Kaufer and Palle Møller (ESO), Sara Ellison (University of Victoria, Canada), Andreas Jaunsen (University of Oslo, Norway), Morten Andersen (AIP, Potsdam, Germany), Andrew Fruchter (STScI, Baltimore, USA), Johan Fynbo and Jens Hjorth (Dark Cosmology Centre, Copenhagen, Denmark), Patrick Petitjean (IAP, Paris, France), Sandra Savaglio (MPE, Garching, Germany), and Ralph Wijers (Astronomical Institute, University of Amsterdam, The Netherlands). Paul Vreeswijk was at the time of this study also associated with the Universidad de Chile, Santiago.

Happy Anniversary, VLT !

NASA Astrophysics Data System (ADS)

2004-04-01

Five years at the service of Europe's astronomers VLT 5 Years One of the world's most advanced astronomical research facilities, the ESO Very Large Telescope (VLT) at the Paranal Observatory in the Chilean Atacama desert, celebrates an important anniversary today. On April 1, 1999, and following almost one year of extensive tests and careful trimming of its numerous high-tech parts, the first 8.2-m VLT Unit Telescope, Antu (UT1), was "handed over" to the astronomers. Since that date, science operations with this marvellous research tool have been continuous and intensive. Kueyen (UT2) started normal operations exactly one year later. Yepun (UT4) was offered to the scientific community in June 2001, while Melipal (UT3) followed in August 2001 [1]. Ever since, all four VLT Unit Telescopes, with an ever-growing suite of highly specialised, extremely powerful astronomical instruments have been in full operation, 365 nights a year. And this with unequalled success, as demonstrated by a long list of important scientific results, including a substantial number of exciting discoveries that are now opening new horizons in astrophysics. Moreover, thanks to heroic and persistent efforts by the dedicated teams of ESO scientists and engineers, the "downtime" due to technical problems has been very small, about 3 per cent, a number that is unequalled among the world's large telescope facilities. In addition, the weather conditions at the Paranal site in the dry Atacama desert in Northern Chile are truly excellent - this is indeed one of the best locations for astronomical observations on the surface of the Earth - and the corresponding "weather downtime" has only been around 10 per cent. This has resulted in an unbelievably low value of total downtime, most likely a new world record for ground-based 8-10 m class telescopes. VLT strong points The Very Large Telescope (VLT) is the world's largest and most advanced optical telescope. It comprises four 8.2-m reflecting Unit Telescopes (UTs) and will in due time also include four moving 1.8-m Auxiliary Telescopes (ATs), the first one of which successfully passed its first tests in January of this year (see ESO PR 01/04). With unprecedented optical resolution and unsurpassed surface area, the VLT produces extremely sharp images and can record light from the faintest and most remote objects in the Universe. It works at the limit of modern technology, regularly allowing the scientists to peer into new and unknown territories in the immense Universe. Contrary to other large astronomical telescopes, the VLT was designed from the beginning with the use of interferometry as a major goal. For this reason, the four 8.2-m Unit Telescopes were positioned in a quasi-trapezoidal configuration. The light beams from these telescopes, at this moment two-by-two, can be combined in the VLT Interferometer (VLTI). It provides the European scientific community with a ground-based telescope array with collecting power significantly greater than any other facilities available at present or being planned, offering imaging and spectroscopy capabilities at visible and infrared wavelengths. Seven of the planned ten first-generation astronomical instruments are now in operation at the VLT. They cover all major observing modes required to tackle current "hot", front-line research topics: * the multi-mode instrument FORS1 (FOcal Reducer and Spectrograph) and its twin, FORS2, * the Infrared Spectrometer And Array Camera (ISAAC) cryogenic infrared imager and spectrometer, * the UVES (Ultra-violet and Visible Echelle Spectrograph) high-dispersion spectrograph, * the NAOS-CONICA Adaptive Optics facility producing images as sharp as if taken in space [2], * the VIsible Multi-Object Spectrograph (VIMOS) four-channel multiobject spectrograph and imager - allowing to obtain low-resolution spectra of up to 1000 galaxies at a time * the Fibre Large Array Multi-Element Spectrograph (FLAMES) that offers the unique capability to study simultaneously and at high spectral resolution 100 individual stars in nearby galaxies. The remaining instruments - the high-resolution infrared spectrograph CRIRES, the Mid Infrared Spectrometer/Imager VISIR and the integral field spectrograph SINFONI - will be installed in 2004-2005. The observational statistics prove that these instruments are extremely efficient - they have some of the highest "shutter-open times" (i.e. percentage of the maximum possible observing time during which the instruments are collecting light from the astronomical objects) ever achieved. The astronomers are well served in this respect: the ISAAC instrument, for example, continues to be in the highest demand and has now performed smoothly during more than 1000 nights and two others, UVES and FORS, are now approaching the same number. Working together with astronomers and engineers at many research institutes in the ten ESO member countries, ESO is now in the process of defining second generation instruments and feasibility studies are well under way. Among the prime projects in this direction are a cryogenic multi-object spectrometer in the near-infrared 1 to 2.4 μm range ("KMOS"), a medium-resolution wide-band (0.32 to 2.4 μm) spectrometer ("X-shooter"), as well as a wide-field 3D optical spectrometer ("3D deep-field surveyor") and a high-contrast, adaptive optics assisted, imager ("planet finder"). In addition to these highly innovative instruments for the VLT UTs, specific instruments that will work with the combined light from several of the telescopes have also been conceived. The interferometric instrument MIDI will be offered to the astronomical community from today (April 1, 2004), fulfilling the VLTI promise. Great efforts have indeed gone into making observations with this very complex science machine as user-friendly as possible. Contrary to what is normally the case in this technically demanding branch of astronomy, scientists will find interferometric work at the VLTI quite similar to that of using the many other, more conventional VLT instruments. Science with the VLT The impressive battery of top-ranking instruments, coupled with the enormous light-collecting power of the VLT, has already provided a real research bonanza with many outstanding scientific results, some of which have been true breakthroughs. They include the amazing new knowledge about the Black Hole at the Galactic Centre, the farthest galaxy known, the most metal-poor and hence, oldest stars, accurate cosmochronological dating by means of Uranium and Thorium spectral lines, high-redshift galaxy rotation curves, micro-quasars, properties of the optical counterparts of gamma-ray bursts, high-redshift supernovae, etc. [3]. All of these advances attest to the power of the VLT and its mode of operational. Not to be forgotten is also the beauty of many of the stunning images obtained with this telescope, one of which was voted amongst the 10 most inspirational astronomical images of the past century [4]. Look at the numerous and detailed ESO Press Releases for more examples of research achievements from the VLT. This trend is also apparent in the productivity of the telescopes. The number of research publications resulting from VLT work in top ranking astronomical journals is steadily increasing with a total close to 700, hereof 250 in 2003 alone. Moreover, research articles based on VLT data are in the mean quoted twice as often as the average. The very high efficiency of the VLT "science machine" now generates huge amounts of data at a very high rate. These are stored in a permanent Science Archive Facility at ESO headquarters, which is jointly operated by ESO and the Space Telescope European Coordinating Facility (ST-ECF). From here, data are distributed daily to astronomers on DVDs and over the World Wide Web. The archive facility has been conceived and developed to enable astronomers to "mine" very efficiently the enormous volumes of data that is collected from the VLT. The archive now contains more than 1 million images or spectra taken by the four UTs with a total volume of about 50 Terabytes (50,000,000,000,000 bytes) of data. This corresponds to the content of about 25 million books of 1000 pages each; they would occupy more than 1000 kilometres of bookshelves! Looking towards the future Says Catherine Cesarsky, ESO Director General since 1999: " The Paranal Observatory has already given rise to an impressive number of scientific results, many of which could not have been obtained elsewhere. Overall, the VLT has been a most remarkable success, and will contribute to science at the highest level for years to come - a fantastic achievement of which we can all be justifiably proud." The work is now underway at full power to provide second-generation instruments for the VLT, to add three more Auxiliary Telescopes to the VLTI and to complement this unique research facility with the two wide-field survey ("pathfinding") telescopes - one to work in the visible part of the spectrum (the 2.5-m VST), the other in the infrared (the 4-m VISTA) - now being constructed at Paranal. Roberto Gilmozzi, director of Paranal Observatory, looks forward: " Ever more exciting times lie ahead for Paranal with new instruments like VISIR and SINFONI and the laser guide star, all of them coming this year. Five years after the start of operations on UT1, the observatory operates its telescopes with very little time set aside for engineering (less than 10%) and very low technical down time. Combined with excellent weather and great image quality, we provide the European community with unsurpassed observing capabilities. As director of this observatory since 1999, I have been privileged to be part of this adventure." The VLT is a fine example of the vast benefits of pooling resources from several countries and it is a flagship of contemporary European research. There is little doubt that for many years to come, ESO's Paranal Observatory with its powerful and efficient facilities will continue to play a leading role in astronomical research. Information for the media Associated material can be found on the corresponding Press Events webpage.

Optical Detection of Anomalous Nitrogen in Comets

NASA Astrophysics Data System (ADS)

2003-12-01

VLT Opens New Window towards Our Origins Summary A team of European astronomers [1] has used the UVES spectrograph on the 8.2-m VLT KUEYEN telescope to perform a uniquely detailed study of Comet LINEAR (C/2000 WM1) . This is the first time that this powerful instrument has been employed to obtain high-resolution spectra of a comet. At the time of the observations in mid-March 2002, Comet LINEAR was about 180 million km from the Sun, moving outwards after its perihelion passage in January. As comets are believed to carry "pristine" material - left-overs from the formation of the solar system, about 4,600 million years ago - studies of these objects are important to obtain clues about the origins of the solar system and the Earth in particular. The high quality of the data obtained of this moving 9th-magnitude object has permitted a determination of the cometary abundance of various elements and their isotopes [2]. Of particular interest is the unambiguous detection and measurement of the nitrogen-15 isotope. The only other comet in which this isotope has been observed is famous Comet Hale-Bopp - this was during the passage in 1997, when it was much brighter than Comet LINEAR. Most interestingly, Comet LINEAR and Comet Hale-Bopp display the same isotopic abundance ratio, about 1 nitrogen-15 atom for each 140 nitrogen-14 atoms ( 14 N/ 15 N = 140 ± 30) . That is about half of the terrestrial value (272). It is also very different from the result obtained by means of radio measurements of Comet Hale-Bopp ( 14 N/ 15 N = 330 ± 75). Optical and radio measurements concern different molecules (CN and HCN, respectively), and this isotopic anomaly must be explained by some differentiation mechanism. The astronomers conclude that part of the cometary nitrogen is trapped in macromolecules attached to dust particles . The successful entry of UVES into cometary research now opens eagerly awaited opportunities for similiar observations in other, comparatively faint comets. These studies will provide crucial information about the detailed composition of a much larger number of comets than hitherto possible and hence, more information about the primordial matter from which the solar system formed. A better understanding of the origins of the cometary material (in particular the HCN and CN molecules [3]) and the connection with heavier organic molecules is highly desirable. This is especially so in view of the probable rôle of comets in bringing to the young Earth materials essential for the subsequent formation of life on our planet . PR Photo 28a/03 : Comet LINEAR (C/2000 WM1) - direct image and UVES slit position. PR Photo 28b/03 : Part of the UVES spectrum of Comet LINEAR (C/2000 WM1) with CN-band. PR Photo 28c/03 : Identification of nitrogen-15 in the spectrum. Cometary material Knowledge of the abundance of the stable isotopes [2] of the light elements in different solar system objects provides critical clues to the origin and early evolution of these objects and of the system as a whole. In order to gain the best possible insight into the origins and formation of the niche in which we live, it is therefore important to determine such isotopic abundance ratios in as many members of the solar family as possible. This is particularly true for comets, believed to be carriers of well-preserved specimens of the pristine material from which the solar system was made, some 4,600 million years ago. However, the detailed study of cometary material is a difficult task. Measurements of isotopic ratios is an especially daunting undertaking, mainly because of the extreme weakness of the spectral signatures (emissions) of the less abundant species like carbon-13, nitrogen-15, etc.. Measurements of microwave emission from those atoms suffer from additional, inherent uncertainties connected to the much stronger emission of the more abundant species. Measurements in the optical spectral region thus take on particular importance in this context. However, it is exceedingly difficult to procure the high-quality, high-resolution spectra needed to show the very faint emissions of the rare species. So far, they were only possible when a very bright comet happened to pass by, perhaps once a decade, thereby significantly limiting such studies. And there has always been some doubt whether the brightest comets are also truly representative of this class of objects. Observations of fainter, more typical comets had to await the advent of powerful instruments and telescopes. First UVES spectrum of a comet ESO PR Photo 28a/03 ESO PR Photo 28a/03 [Preview - JPEG: 495 x 400 pix - 183k [Normal - JPEG: 990 x 800 pix - 450k] ESO PR Photo 28b/03 ESO PR Photo 28b/03 [Preview - JPEG: 502 x 400 pix - 115k [Normal - JPEG: 1004 x 800 pix - 290K] Captions : PR Photo 28a/03 displays an image of Comet LINEAR (C/2000 WM1) with the UVES slit viewer image. The colour composite in the large frame (sky field: 16 x 16 arcmin 2 ) was obtained by Gordon Garradd (Loomberah, NSW, Australia). [Image Copyright (c) 2002 Gordon Garradd (loomberah@ozemail.com.au]. The UVES slit viewer photo (small frame; 40 x 40 arcsec 2 ) is a false-colour image taken in the (red) R-band with UVES+KUEYEN on March 22, 2002; it shows the position of the narrow spectrograph slit (0.45 arcsec wide and 8 arcsec long) crossing the inner coma and through which the comet's light was captured to produce the high-resolution spectra. The slit has been offset from the center of light to reduce contamination from solar light reflected off dust particles in the comet's coma - there is most dust near the nucleus. PR Photo 28b/03 shows a small part of the UVES spectrum with an emission band (ultraviolet light at wavelength 390 nm) from CN molecules [3] in the comet's atmosphere. The emission lines are produced by absorption of the solar light by these molecules, followed by re-emission of lines of specific wavelengths. This physical process is known as "resonance-fluorescence" - it is the same process that causes glowing teeth and shirts in a Disco. The upper panel displays the "raw" spectrum; the lower is the "extracted" spectrum, now clearly displaying the individual emission lines. Observations of Comet LINEAR (C/2000 WM1) were carried out with the UV-Visual Echelle Spectrograph (UVES) mounted on the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile) on four occasions during March 2002. At that time, the comet had moved past its perihelion and was by far the faintest comet for which such a detailed spectral analysis had ever been attempted. A number of 25-min exposures were secured, resulting in a total observing time of about 4 hours. The final spectrum covers the entire visual region (330 - 670 nm) and is one of the most detailed and information-rich cometary spectra ever obtained. PR Photo 28b/03 displays a small part of this spectrum. These observations are the first high resolution spectra of a comet taken with the VLT. Identification of nitrogen-15 ESO PR Photo 28c/03 ESO PR Photo 28c/03 [Preview - JPEG: 400 x 524 pix - 109k [Normal - JPEG: 800 x 1047 pix - 285k] Captions : PR Photo 28c/03 is an enlarged view of a small section of the high-resolution UVES spectrum of Comet LINEAR ( PR Photo 28b/03 ) with emission lines from CN-molecules (blue line), compared to the "synthetic" spectrum based on theoretical calculations and laboratory measurements (black line ; some of the lines are labeled with quantum numbers). In the upper panel, the synthetic spectrum has been produced on the basis of the most abundant isotopic species ( 12 C 14 N). The lower panel shows that the observed spectrum is in nearly perfect agreement with a synthetic spectrum which includes contributions from two other isotopic species, 13 C 14 N (emission lines at wavelengths indicated by red ticks) and 12 C 15 N (blue ticks); they are added in proportions of 1/115 and 1/140, respectively. The isotopic abundances of carbon-13 and nitrogen-15 are measured accordingly. Introducing instead the terrestrial ratio for nitrogen-15 (1/272) significantly degrades the fit and thus that ratio can clearly be ruled out in Comet LINEAR. At the time of the VLT observations, the comet was of 9th magnitude, i.e. about 15 times fainter than what can be perceived with the unaided eye. The distance from the Sun was about 180 million km; the distance from the Earth was 186 million km. The observations included calibration spectra of sunlight reflected from the lunar surface; they were used to "subtract" the solar signatures in the comet's spectrum, caused by reflection of sunlight from the dust particles around the comet. As expected, in addition to emission from "normal" CN-molecules ( 12 C 14 N), the UVES data also show emission lines of the 13 C 14 N-molecule that contains the rare isotope carbon-13. The derived 12 C/ 13 C isotopic ratio is 115 ± 20, quite similar to the "standard" solar system value of 89. However, there is also a series of weak features that are positioned exactly at the theoretical wavelengths of emission lines from 12 C 15 N-molecules, cf. PR Photo 28c/03 . The excellent fit that is evident in this diagram proves beyond any doubt the presence of nitrogen-15 in Comet LINEAR and allows a quite accurate determination of the isotopic ratio. The "anomalous" nitrogen isotope ratio in comets In 1997, the same group of astronomers obtained spectra of the (at that time) much brighter Comet Hale-Bopp with the 2.6-m NOT telescope (Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain) in order to investigate the isotopic ratio of carbon-12 to carbon-13. Claude Arpigny remembers: " Interestingly, our spectra of Hale-Bopp showed a number of weak and unidentified emission lines. We later realised that they were positioned close to the theoretical wavelengths of some lines from the 12 C 15 N-molecule. This was a pleasant surprise, as lines from that molecular species were previously believed to be so faint that they would not be observable." He continues: "This identification is now fully confirmed with the UVES observations of Comet LINEAR. Our detections in these two comets are the first ever of those emission lines in comets ". The estimates of the 14 N/ 15 N isotopic ratios are very similar, 140 ± 35 for Hale-Bopp and 140 ± 30 for LINEAR. These ratios are remarkably low and different from the terrestrial value of 272. This means that these comets have comparatively more nitrogen-15 than has the Earth. No measurement has yet been made of the abundance of nitrogen-15 in the Sun. So which of the values corresponds to the composition of the material from which the solar system was made? Different origins? To date, only four cometary values of the 14 N/ 15 N isotopic ratio have been reported: two in the radio wavelength range and the two now measured by means of optical spectra. The radio measurements concern the HCN-molecule (hydrocyanic acid) in Comet Hale-Bopp, a "parent" molecule for the CN-molecules present in comets. Contrary to the optical measurements, the radio values (about 330 ± 75) are compatible with the terrestrial value (272). But radio measurements of carbon and nitrogen isotopic ratios are only possible on extraordinarily bright comets like Hale-Bopp, and even then, the achievable accuracy is very limited. This emphasizes the importance of performing this kind of research by means of optical observations. The origin of the isotopic discrepancy between different CN parents is likely due to fractionation mechanisms in the forming presolar nebula, e.g. when oxygen- and carbon-bearing molecules in high-density nebulae stick to cold (10K) dust grains. Macromolecules in space The astronomers think that the new results indicate that the HCN-molecule cannot be the only "parent" of the CN-molecule; the latter must also be produced by some as yet unknown parent(s) in which the nitrogen-15 isotope is even more abundant. In this connection, it is very interesting that an "excess" of nitrogen-15 is also known to exist in interplanetary dust particles (IDPs), captured by high-flying aircraft in the Earth's atmosphere. They represent the oldest material in the solar system that can be subjected to detailed laboratory analysis. Many of these particles are thought to originate from passing comets - this possibility is obviously supported by the new measurements. The nitrogen-15 carriers in IDPs have not been securely identified but are possibly organic macromolecules or polycyclic aromatic hydrocarbons (PAHs). It is thus possible that the additional parent(s) of cometary CN may belong to this ensemble of organic substances. Whatever the case, the longstanding question of nitrogen and its isotopic ratio(s) in the solar system, whether present and primordial, is notoriously enigmatic in several respects. However, the present results demonstrate that a detailed study of comets may deliver very useful clues. The team has now been granted more observing time with UVES and KUEYEN in order to pursue this important study by observing more comets.

Chemical evolution and stellar populations in the Sagittarius dwarf Spheroidal Galaxy

NASA Astrophysics Data System (ADS)

Sbordone, L.; Bonifacio, P.; Giuffrida, G.; Marconi, G.; Monaco, L.; Zaggia, S.

2007-05-01

The closest neighbour of the Milky Way (MW), the Sagittarius dwarf Spheroidal Galaxy (Sgr dSph) is being tidally destroyed by the interaction with our Galaxy, losing its stellar content along a huge stream clearly detectable within the Halo. This makes the Sgr dSph an ideal laboratory to study at the same time the chemical evolution of dwarf galaxies and their role in building bigger structures such as the MW. Since some years we are studying the stellar populations of the Sgr main body and stream, with particular attention to their detailed chemical composition. We collected detailed abundances (up to 22 elements, O to Eu) for 27 stars in the Sgr dSph main body, 5 in the associated globular cluster Terzan 7, and 12 more in the trailing Sgr tidal arm (UVES@VLT and SARG@TNG data). We are also conducting a large FLAMES@VLT chemical and dynamical analysis aimed at obtaining metallicities, alpha-elements content and radial velocities from automated analysis of the spectra. Finally, we just completed the first large scale photometric and spectroscopic survey of the stellar populations across all the dSph main body extension with VIMOS@VLT, aimed at exploring the variations in stellar populations and at deriving radial velocity memberships for future high resolution spectroscopic analysis. The picture emerging from all these studies portraits a large and extremely complex object, with signs of a long and still unclear evolution. Metallicity varies across three orders of magnitude ([Fe/H] from -3 to 0), CMDs change surprisingly from the core to the outskirts of the galaxy, and the chemical composition of the most metal rich objects show a very characteristic signature, with underabundant alpha elements, deficient Na, underabundant Fe-peak Mn, Co, Ni, Cu and Zn, and strongly enhanced n-capture elements La and Nd. This highly peculiar "signature" can also be effectively used to recognized stripped populations lost by Sgr in favour of the MW system, as clearly showed by the globular Palomar 12, which shows the same chemical anomalies detected in Sgr dSph.

The rebirth of Supernova 1987A : a study of the ejecta-ring collision

NASA Astrophysics Data System (ADS)

Gröningsson, Per

Supernovae are some of the most energetic phenomena in the Universe and they have throughout history fascinated people as they appeared as new stars in the sky. Supernova (SN) 1987A exploded in the nearby satellite galaxy, the Large Magellanic Cloud (LMC), at a distance of only 168,000 light years. The proximity of SN 1987A offers a unique opportunity to study the medium surrounding the supernova in great detail. Powered by the dynamical interaction of the ejecta with the inner circumstellar ring, SN 1987A is dramatically evolving at all wavelengths on time scales less than a year. This makes SN 1987A a great ``laboratory'' for studies of shock physics. Repeated observations of the ejecta-ring collision have been carried out using the UVES echelle spectrograph at VLT. This thesis covers seven epochs of high resolution spectra taken between October 1999 and November 2007. Three different emission line components are identified from the spectra. A narrow (~10 km/s) velocity component emerges from the unshocked ring. An intermediate (~250 km/s) component arises in the shocked ring, and a broad component extending to ~15,000 km/s comes from the reverse shock. Thanks to the high spectral resolution of UVES, it has been possible to separate the shocked from the unshocked ring emission. For the unshocked gas, ionization stages from neutral up to Ne V and Fe VII were found. The line fluxes of the low-ionization lines decline during the period of the observations. However, the fluxes of the [O III] and [Ne III] lines appear to increase and this is found to be consistent with the heating of the pre-shock gas by X-rays from the shock interactions. The line emission from the ejecta-ring collision increases rapidly as more gas is swept up by the shocks. This emission comes from ions with a range of ionization stages (e.g., Fe II-XIV). The low-ionization lines show an increase in their line widths which is consistent with that these lines originate from radiative shocks. The high-ionization line profiles (Fe X-XIV) initially show larger spectral widths, which indicates that at least a fraction of the emission comes from non-radiative shocks.

A Brown Dwarf Joins the Jet-Set

NASA Astrophysics Data System (ADS)

2007-05-01

Jets of matter have been discovered around a very low mass 'failed star', mimicking a process seen in young stars. This suggests that these 'brown dwarfs' form in a similar manner to normal stars but also that outflows are driven out by objects as massive as hundreds of millions of solar masses down to Jupiter-sized objects. The brown dwarf with the name 2MASS1207-3932 is full of surprises [1]. Its companion, a 5 Jupiter-mass giant, was the first confirmed exoplanet for which astronomers could obtain an image (see ESO 23/04 and 12/05), thereby opening a new field of research - the direct detection of alien worlds. It was then later found (see ESO 19/06) that the brown dwarf has a disc surrounding it, not unlike very young stars. ESO PR Photo 24/07 ESO PR Photo 24/07 Jets from a Brown Dwarf (Artist's Impression) Now, astronomers using ESO's Very Large Telescope (VLT) have found that the young brown dwarf is also spewing jets, a behaviour again quite similar to young stars. The mass of the brown dwarf is only 24 Jupiter-masses. Hence, it is by far the smallest object known to drive an outflow. "This leads us to the tantalizing prospect that young giant planets could also be associated with outflows," says Emma Whelan, the lead-author of the paper reporting the results. The outflows were discovered using an amazing technique known as spectro-astrometry, based on high resolution spectra taken with UVES on the VLT. Such a technique was required due to the difficulty of the task. While in normal young stars - known as T-Tauri stars for the prototype of their class - the jets are large and bright enough to be seen directly, this is not the case around brown dwarfs: the length scale of the jets, recovered with spectro-astrometry is only about 0.1 arcsecond long, that is, the size of a two Euro coin seen from 40 km away. The jets stretch about 1 billion kilometres and the material is rushing away from the brown dwarf with a speed of a few kilometres per second. The astronomers had to rely on the power of the VLT because the observed emission is extremely faint and only UVES on the VLT could provide both the sensitivity and the spectral resolution they required. "Discoveries like these are purely reliant on excellent telescopes and instruments, such as the VLT," says Whelan. "Our result also highlights the incredible level of quality which is available today to astronomers: the first telescopes built by Galileo were used to observe the moons of Jupiter. Today, the largest ground-based telescopes can be used to observe a Jupiter size object at a distance of 200 light-years and find it has outflows!" Using the same technique and the same telescope, the team had previously discovered outflows in another young brown dwarf. The new discovery sets a record for the lowest mass object in which jets are seen [2]. Outflows are ubiquitous in the Universe, as they are observed rushing away from the active nuclei of galaxies - AGNs - but also emerging from young stars. The present observations show they even arise in still lower mass objects. The outflow mechanism is thus very robust over an enormous range of masses, from several tens of millions of solar mass (for AGNs) down to a few tens of Jupiter masses (for brown dwarfs). More Information These results were reported in a Letter to the Editor in the Astrophysical Journal (vol. 659, p. L45): "Discovery of a Bipolar Outflow from 2MASSW J1207334-393254 a 24 MJup Brown Dwarf", by E.T. Whelan et al. The team is composed of Emma Whelan and Tom Ray (Dublin Institute for Advanced Studies, Ireland), Ray Jayawardhana (University of Toronto, Canada), Francesca Bacciotti, Antonella Natta and Sofia Randich (Osservatorio Astrofisico di Arcetri, Italy), Leonardo Testi (ESO), and Subu Mohanty (Harvard-Smithsonian CfA, USA).

Ground-based detections of sodium in HD 209458b's atmosphere in two data sets

NASA Astrophysics Data System (ADS)

Albrecht, S.; Snellen, I.; de Mooij, E.; Le Poole, R.

2009-02-01

We present two separate ground-based detections of sodium in the transmission spectrum of HD 209458b. First we reanalyzed an archival data set from the HDS spectrograph on Subaru, which shows sodium at a >5σ level. Secondly, our preliminary results of a UVES/VLT data set indicate sodium absorption at a similar level, although the data cover the eclipse only partially. Both results are fully consistent with the HST results of Charbonneau et al. (2002). The Na D absorption feature seems to be resolved in the narrowest passband.

Search for spectroscopical signatures of transiting HD 209458b's exosphere

NASA Astrophysics Data System (ADS)

Moutou, C.; Coustenis, A.; Schneider, J.; St Gilles, R.; Mayor, M.; Queloz, D.; Kaufer, A.

2001-05-01

Following recent attempts to detect the exosphere of the extra-solar planet 51 Pegb in the infrared (Coustenis et al. \\cite{cou97}, \\cite{cou98}; Rauer et al. \\cite{rau00a}), we discuss here a search for optical spectroscopic signatures from a gaseous extended envelope (called exosphere) surrounding the planet HD 209458b. This planet has a demonstrated photometric transit (Charbonneau et al. \\cite{cha00a}; Henry et al. \\cite{hen00}), thus offering an increased probability for the spectroscopic detection of such an envelope. Therefore it is the best known candidate for probing the exospheric composition of a giant planet, orbiting a Sun-like star at a short distance. The observations were performed with UVES at the VLT and cover most of the 328-669 nm range. We did not detect HD 209458b's exosphere at a level of 1%, a value close to the predictions. We discuss here the first results obtained and their limitations, as well as future prospective. Based on public data from the UVES Commissioning at the ESO 8.2~m Kueyen telescope operated on Paranal Observatory, Chile.

A New Precision Measurement of the Small-scale Line-of-sight Power Spectrum of the Lyα Forest

NASA Astrophysics Data System (ADS)

Walther, Michael; Hennawi, Joseph F.; Hiss, Hector; Oñorbe, Jose; Lee, Khee-Gan; Rorai, Alberto; O’Meara, John

2018-01-01

We present a new measurement of the Lyα forest power spectrum at 1.8 < z < 3.4 using 74 Keck/HIRES and VLT/UVES high-resolution, high-signal-to-noise-ratio quasar spectra. We developed a custom pipeline to measure the power spectrum and its uncertainty, which fully accounts for finite resolution and noise and corrects for the bias induced by masking missing data, damped Lyα absorption systems, and metal absorption lines. Our measurement results in unprecedented precision on the small-scale modes k> 0.02 {{s}} {{km}}-1, inaccessible to previous SDSS/BOSS analyses. It is well known that these high-k modes are highly sensitive to the thermal state of the intergalactic medium, but contamination by narrow metal lines is a significant concern. We quantify the effect of metals on the small-scale power and find a modest effect on modes with k< 0.1 {{s}} {{km}}-1. As a result, by masking metals and restricting to k< 0.1 {{s}} {{km}}-1, their impact is completely mitigated. We present an end-to-end Bayesian forward-modeling framework whereby mock spectra with the same noise, resolution, and masking as our data are generated from Lyα forest simulations. These mock spectra are used to build a custom emulator, enabling us to interpolate between a sparse grid of models and perform Markov chain Monte Carlo fits. Our results agree well with BOSS on scales k< 0.02 {{s}} {{km}}-1, where the measurements overlap. The combination of the percent-level low-k precision of BOSS with our 5%–15% high-k measurements results in a powerful new data set for precisely constraining the thermal history of the intergalactic medium, cosmological parameters, and the nature of dark matter. The power spectra and their covariance matrices are provided as electronic tables.

VizieR Online Data Catalog: Abundances in the local region. I. G and K giants (Luck, 2015)

NASA Astrophysics Data System (ADS)

Luck, R. E.

2015-10-01

At the start of this program, the observation list for giants was set to sample the G/K giants of the local region out to about 100pc from the Sun in all directions. The region was subdivided into cubes that were 25pc on a side; from each sub-volume, appropriate stars were selected north of declination -30°. This sample yielded the 286 G/K giants found in Luck et al. 2007 (cat. J/AJ/133/2464). This data set was also augmented by the addition of numerous G/K giants, increasing the number in the 100pc volume to 594 stars. Because the volume selection criteria used in Luck et al. 2007 (cat. J/AJ/133/2464) formally extended out to 115pc, a more precise comparison is that the current sample has 740 stars out to the older limit. Additional stars from the Bright Star Catalog (Hoffleit & Jaschek, 1991bsc..book.....H) were added, driving the sample out to about 200pc. The spectral database was supplemented using the ELODIE and ESO Archives. The ESO addition adds the southern sky. The bulk of the northern stars were observed using the McDonald Observatory Struve Telescope and Sandiford Cassegrain Echelle Spectrograph. For the ELODIE and ESO data archives, a list of all stars available was obtained and spectral type for each from SIMBAD was retrieved. Stars having a spectral type of F, G, or K III were then processed. The ESO data derives from the HARPS and UVES spectrographs. Basic observational data for the program stars can be found in Table1, along with some derived quantities, such as distance. The primary source of observational data for this study is a set of high signal-to-noise ratio (S/N) spectra obtained during numerous observing runs between 1997 and 2010 at McDonald Observatory using the 2.1m Struve Telescope and the Sandiford Cassegrain Echelle Spectrograph. The spectra continuously cover a wavelength range from about 484 to 700nm, with a resolving power of about 60000. Typical S/N values for the spectra are in excess of 150. To enable cancellation of telluric lines, broad-lined B stars were regularly observed with S/N exceeding that of the program stars. The 726 stars observed with the Sandiford spectrograph are marked with an "S" in column "Sce" of Table1. A further 120 spectra were obtained from the ELODIE Archive. These echelle spectra are fully processed through order co-addition with a continuous wavelength span from about 400 to 680 nm and a resolution of 42000. Only spectra with S/N>50 were utilized in this analysis. An "E" in Table1, column "Sce", marks these stars. The ESO Archive was used to obtain spectra from the ESO 3.6m telescope and HARPS spectrograph. The HARPS spectra cover a continuous wavelength range from about 400 to 680nm with a native resolving power of 120000. To match the resolution of the Sandiford data and to increase the S/N of the data, these spectra were co-added to a resolution of 60000. Typical maximum S/N values (per pixel) for the spectra are in excess of 150. In Table1, column "Sce", these stars are marked with an "H." Spectra from the UVES spectrograph and VLT/UT2 were also utilized. These spectra are rather heterogeneous, having resolutions of 40000-80000 and non-continuous spectral coverages in the range 400-700nm. A number of the spectra from UVES stop at about 625nm, meaning that [O I] 630nm and Li I 670nm were not observed. In Table 1, "U" denotes the stars observed with UVES spectrograph. (5 data files).

Variations in VLT/UVES-based OH rotational temperatures for time scales from hours to 15 years

NASA Astrophysics Data System (ADS)

Noll, Stefan; Kimeswenger, Stefan; Proxauf, Bastian; Kausch, Wolfgang; Unterguggenberger, Stefanie; Jones, Amy M.

2017-04-01

Hydroxyl (OH) emission is an important tracer of the climate, chemistry, and dynamics of the Earth's mesopause region. However, the relation of intensity variations in different OH lines is not well understood yet. This is critical for the most popular use of OH lines: the estimate of ambient temperatures based on transitions at low rotational levels of the same band. It is possible that the measured variability of the derived rotational temperature does not coincide with changes in the ambient temperature. Such differences can be caused by varying deviations from the local thermodynamic equilibrium (LTE) for the population distribution over the considered rotational levels. The non-LTE effects depend on the ratio of the thermalising collisions (mostly related to molecular oxygen) and competing radiative transitions or collisions without thermalisation of the rotational level distribution. Therefore, significant changes in the vertical structure of excited OH and its main quenchers can affect the temperature measurements. We have investigated the variability of OH rotational temperatures and the corresponding contributions of non-LTE effects for different OH bands and time scales up to 15 years based on data of the high-resolution echelle spectrograph UVES at the Very Large Telescope at Cerro Paranal in Chile. In order to link the measured rotational temperatures with the structure of the OH emission layer, we have also studied OH emission and kinetic temperature profiles from the multi-channel radiometer SABER on the TIMED satellite taken between 2002 and 2015. The results show that non-LTE contributions can significantly affect the OH rotational temperatures. Their variations can be especially strong during the night and for high upper vibrational levels of the transitions, where amplitudes of several Kelvins can be measured. They appear to be weak if long-term variations such as those caused by the solar cycle are investigated. These differences in the response correlate with changes in the effective height of the OH emission layer and the effective air density in the layer. The latter confirms the expected important role of molecular oxygen for the thermalisation of the OH rotational level populations.

LS IV — 14°116 : A Time-Resolved Spectroscopic Study

NASA Astrophysics Data System (ADS)

Martin, Pamela; Jeffery, C. Simon

2017-12-01

LSIV-14 116 is a very unusual subdwarf B star. It pulsates non-radially with high-order g-modes, these pulsations are unexpected and unexplained, as the effective temperature is 6 000K hotter than the blue edge of the hot subdwarf g-mode instability strip. Its spectrum is enriched in helium which is not seen in either the V361 Hya (p-mode pulsators) or the V1093 Her stars (g-mode pulsators). Even more unusual is the 4 dex overabundance of zirconium, yttrium, and strontium. It is proposed that these over-abundances are a result of extreme chemical stratification driven by radiative levitation. We have over 20hrs of VLT/UVES spectroscopy from which we have obtained radial velocity curves for individual absorption lines. We are currently exploring ways in which to resolve the photospheric motion as a function of optical depth.

"First Light" Approaches for VLT MELIPAL

NASA Astrophysics Data System (ADS)

2000-01-01

The year 1999 was a very busy one at ESO's Paranal Observatory , the site of the Very Large Telescope (VLT). Soon after the official Inauguration on March 5, 1999, regular observations started with the first 8.2-m VLT Unit Telescope ANTU . During the first nine months of operation (April - December 1999), about 79,000 exposures were made with the FORS1 and ISAAC astronomical instruments at this telescope. Altogether, more than 68 Gigabytes of unique data were gathered during this period for about 200 individual research programmes and stored in the VLT Data Archive. "First Light" was successfully achieved early in the year for the second 8.2-m VLT Unit telescope, KUEYEN . It has since been equipped with two powerful instruments, UVES and FORS2. Science observations with this telescope will start on April 1, 2000. Already in early December 1999, ahead of the schedule, the third 8.2-m Zerodur mirror in its cell was attached to the third 8.2-m VLT Unit Telescope, MELIPAL , cf. ESO PR Photos 42a-ad/99. The moment of "First Light" is approaching for this telescope. Originally planned for mid-February 2000, this significant event is now expected to take place about two weeks ahead of schedule, in late January 2000. From then on, the VLT will possess nearly 160 square metres of extremely accurate, highly reflecting mirror surface. While the observations for "First Light" and the subsequent commissioning period will be carried out with the VLT Test Camera, MELIPAL will receive its first special astronomical instrument, the VIsible MultiObject Spectrograph (VIMOS) towards the middle of the year. It is optimized for large field imaging and spectroscopic surveys and will become a real workhorse of the VLT for this type of research projects, together with the Near InfraRed MultiObject Spectrograph (NIRMOS) , to be installed later at the fourth 8.2-m Unit Telescope, YEPUN . YEPUN will have "First Light" later this year and the work on this telescope also progresses well. The "M1 Dummy" that was mounted on the telescope frame for balance during the mechanical assembly was removed on January 4. The next day, it was transported down to the Base Camp storage area where it was lifted off the Carriage using a combination of two cranes. The empty M1 Carriage was then moved to the Mirror Maintenance Building (MMB) where the fourth M1 Cell with a dummy concrete mirror was loaded. Later that day it was transported up to YEPUN and the next morning (January 6), the Mirror Cell was moved inside the enclosure. Over the next weeks, it will be fitted to the back of the telescope structure. In parallel, the "M2 Unit" on which the 1.1-m secondary mirror of beryllium will later be mounted, is now being assembled in the Integration Laboratory in the MMB. The following digital photos were obtained during the past days and illustrate the recent work.

Atmospheric Sciences Meet Astronomy: Mutual Benefits from two Different Approaches

NASA Astrophysics Data System (ADS)

Kausch, Wolfgang; Noll, Stefan; Kimeswenger, Stefan; Kondrak, Matthias; Unterguggenberger, Stefanie; Przybilla, Norbert; Lakićević, Maša; Zeilinger, Werner

2016-04-01

Light from astronomical targets has to pass the Earth's atmosphere when being observed by ground-based telescope facilities. The signal detected by modern astronomical spectrographs is significantly influenced by molecular absorption and airglow emission. The first mainly arises from various species in the lower, thus denser atmosphere, whereas the latter is caused by chemiluminescence in the mesopause region and above. As ground-based astronomical spectrographs are optimised from the near-UV to the mid-infrared regime (0.3....25μm), a number of absorption features from numerous species are directly visible (e.g. H2O, CO2, CH4, O2, O3,...). The same is true for the airglow emission arising e.g. from the hydroxyl radical and oxygen. The high resolution provided by some spectrographs and their frequent usage allows a detailed investigation of atmospheric lines. Usually being a source of noise for astronomers, which needs to be corrected for, this influence can be used to precisely analyse the composition and the state of the Earth's atmosphere above an observatory. On the other hand, a good knowledge of this allows astronomers to better correct for this influence. Thus, both, atmospheric and astronomical sciences highly benefit from a good understanding of the atmospheric state above an observatory. During the past years we conducted several studies to link astronomical and atmospheric data. For this purpose we use data taken with the Very Large Telescope (VLT) operated by the European Southern Observatory, and the Cerro Armazones Observatory (OCA, University of Bochum, Germany; Universidad Católica del Norte, Chile), both located in the Chilean Atacama desert. The three spectrographs used in our studies are X-Shooter@VLT (resolving power R˜3300...18000, wavelength range λ=0.3...2.5μm), UVES@VLT (R˜20.000....110.000, λ=0.3....1.1μm), and BESO@OCA (R=50000@Hα=0.656μm, λ=0.38 - 0.84μm). In addition, we use atmospheric data obtained with the satellites ENVISAT (MIPAS instrument), Aura (MLS), and TIMED (SABER), and modelled data from the Global Data Assimilation System (GDAS), and the ERA/MACC reanalysis from the European Centre for Medium-Range Weather Forecasts (ECMWF). In this presentation we give an overview on our methods to link these various data, the impact/application of these data on atmospheric sciences and observations with classical and future astro-particle Cherenkov telescopes, and present recent results.

THE ORIGIN OF ENHANCED ACTIVITY IN THE SUNS OF M67

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reiners, A.; Giampapa, M. S., E-mail: Ansgar.Reiners@phys.uni-goettingen.d, E-mail: giampapa@noao.ed

2009-12-10

We report the results of the analysis of high-resolution photospheric line spectra obtained with the UVES instrument on the VLT for a sample of 15 solar-type stars selected from a recent survey of the distribution of H and K chromospheric line strengths in the solar-age open cluster M67. We find upper limits to the projected rotation velocities that are consistent with solar-like rotation (i.e., v sin iapprox< 2-3 km s{sup -1}) for objects with Ca II chromospheric activity within the range of the contemporary solar cycle. Two solar-type stars in our sample exhibit chromospheric emission well in excess of evenmore » solar maximum values. In one case, Sanders 1452, we measure a minimum rotational velocity of v sin i = 4 +- 0.5 km s{sup -1}, or over twice the solar equatorial rotational velocity. The other star with enhanced activity, Sanders 747, is a spectroscopic binary. We conclude that high activity in solar-type stars in M67 that exceeds solar levels is likely due to more rapid rotation rather than an excursion in solar-like activity cycles to unusually high levels. We estimate an upper limit of 0.2% for the range of brightness changes occurring as a result of chromospheric activity in solar-type stars and, by inference, in the Sun itself. We discuss possible implications for our understanding of angular momentum evolution in solar-type stars, and we tentatively attribute the rapid rotation in Sanders 1452 to a reduced braking efficiency.« less

HIP 10725: The first solar twin/analogue field blue straggler

NASA Astrophysics Data System (ADS)

Schirbel, Lucas; Meléndez, Jorge; Karakas, Amanda I.; Ramírez, Iván; Castro, Matthieu; Faria, Marcos A.; Lugaro, Maria; Asplund, Martin; Tucci Maia, Marcelo; Yong, David; Howes, Louise; do Nascimento, José D.

2015-12-01

Context. Blue stragglers are easy to identify in globular clusters, but are much harder to identify in the field. Here we present the serendipitous discovery of one field blue straggler, HIP 10725, that closely matches the Sun in mass and age, but with a metallicity slightly lower than solar. Aims: We characterise the solar twin/analogue HIP 10725 to assess whether this star is a blue straggler. Methods: We employed spectra with high resolution (R ~ 105) and high signal-to-noise ratio (330) obtained with UVES at the VLT to perform a differential abundance analysis of the solar analogue HIP 10725. Radial velocities obtained by other instruments were also used to check for binarity. We also studied its chromospheric activity, age, and rotational velocity. Results: HIP 10725 is severely depleted in beryllium ([ Be/H ] ≤ -1.2 dex) for its stellar parameters and age. The abundances relative to solar of the elements with Z ≤ 30 show a correlation with condensation temperature, and the neutron capture elements produced by the s-process are greatly enhanced, while the r-process elements seem normal. We found its projected rotational velocity (vsini = 3.3 ± 0.1 km s-1) to be significantly higher than solar and incompatible with its isochrone-derived age. Radial velocity monitoring shows that the star has a binary companion. Conclusions: Based on the high s-process element enhancements and low beryllium abundance, we suggest that HIP 10725 has been polluted by mass transfer from an AGB star that probably had an initial mass of about 2 M⊙. The radial velocity variations suggest the presence of an unseen binary companion, probably the remnant of a former AGB star. Isochrones predict a solar-age star, but this disagrees with the high projected rotational velocity and high chromospheric activity. We conclude that HIP 10725 is a field blue straggler, rejuvenated by the mass-transfer process of its former AGB companion. Based on observations obtained at the European Southern Observatory (ESO) Very Large Telescope (VLT) at Paranal Observatory, Chile (observing programs 083.D-0871, 082.C-0446, 093.D-0807), and complemented with observations taken at the Observatório Pico dos Dias (OPD), Brazil (program OP2014A-011).Appendix A is available in electronic form at http://www.aanda.org

First Large-scale Herbig-Haro Jet Driven by a Proto-brown Dwarf

NASA Astrophysics Data System (ADS)

Riaz, B.; Briceño, C.; Whelan, E. T.; Heathcote, S.

2017-07-01

We report the discovery of a new Herbig-Haro jet, HH 1165, in SOAR narrow-band imaging of the vicinity of the σ Orionis cluster. HH 1165 shows a spectacular extended and collimated spatial structure, with a projected length of 0.26 pc, a bent C-shaped morphology, multiple knots, and fragmented bow shocks at the apparent ends of the flow. The Hα image shows a bright halo with a clumpy distribution of material seen around the driving source, and curved reflection nebulosity tracing the outflow cavities. The driving source of HH 1165 is a Class I proto-brown dwarf, Mayrit 1701117 (M1701117), with a total (dust+gas) mass of ˜36 M Jup and a bolometric luminosity of ˜0.1 L ⊙. High-resolution VLT/UVES spectra of M1701117 show a wealth of emission lines indicative of strong outflow and accretion activity. SOAR/Goodman low-resolution spectra along the jet axis show an asymmetrical morphology for HH 1165. We find a puzzling picture wherein the northwest part exhibits a classical HH jet running into a pre-dominantly neutral medium, while the southern part resembles an externally irradiated jet. The C-shaped bending in HH 1165 may be produced by the combined effects from the massive stars in the ionization front to the east, the σ Orionis core to the west, and the close proximity to the B2-type star HR 1950. HH 1165 shows all of the signatures to be considered as a scaled-down version of parsec-length HH jets, and can be termed as the first sub-stellar analog of a protostellar HH jet system.

First Large-scale Herbig–Haro Jet Driven by a Proto-brown Dwarf

DOE Office of Scientific and Technical Information (OSTI.GOV)

Riaz, B.; Briceño, C.; Heathcote, S.

2017-07-20

We report the discovery of a new Herbig–Haro jet, HH 1165, in SOAR narrow-band imaging of the vicinity of the σ Orionis cluster. HH 1165 shows a spectacular extended and collimated spatial structure, with a projected length of 0.26 pc, a bent C-shaped morphology, multiple knots, and fragmented bow shocks at the apparent ends of the flow. The H α image shows a bright halo with a clumpy distribution of material seen around the driving source, and curved reflection nebulosity tracing the outflow cavities. The driving source of HH 1165 is a Class I proto-brown dwarf, Mayrit 1701117 (M1701117), withmore » a total (dust+gas) mass of ∼36 M {sub Jup} and a bolometric luminosity of ∼0.1 L {sub ⊙}. High-resolution VLT/UVES spectra of M1701117 show a wealth of emission lines indicative of strong outflow and accretion activity. SOAR/Goodman low-resolution spectra along the jet axis show an asymmetrical morphology for HH 1165. We find a puzzling picture wherein the northwest part exhibits a classical HH jet running into a pre-dominantly neutral medium, while the southern part resembles an externally irradiated jet. The C-shaped bending in HH 1165 may be produced by the combined effects from the massive stars in the ionization front to the east, the σ Orionis core to the west, and the close proximity to the B2-type star HR 1950. HH 1165 shows all of the signatures to be considered as a scaled-down version of parsec-length HH jets, and can be termed as the first sub-stellar analog of a protostellar HH jet system.« less

Eta Carinae: At the Crossroads of becoming a Supernova

NASA Technical Reports Server (NTRS)

Gull, Theodore

2007-01-01

Since the 1840's, when Eta Carinae's visual magnitude rivaled Sirius, the brightest star in the night sky, astronomers have wondered what major event took place. Today with the Hubble Space Telescope Imaging Spectrograph, with CHANDRA X-ray spectroscopy and the Very Large Telescope spectrographs and interferometers, we have learned that over 12 solar masses of material was ejected at 500 to 700 km/s into interstellar space. This ejecta is quite different from the normal interstellar medium. It is rich in nitrogen, poor in oxygen and carbon. The dust properties are quite peculiar and many metals such as vanadium, strontium, cadmium are seen in both absorption against the central source, plus a number of molecules. The chemical and dust formation is likely dominated by nitrogen as we see H_2, CH, CH+, OH, NH, HCl and NH-3, but no CO. Other metals and molecules are being searched out in the FUSE, HST/STIS, VLT/UVES and VLT/CRIRES spectra. I will describe what we know about the massive binary stellar system, how it changes every 5.54 year in UV and X-ray output and how the massive ejecta responds in this astrophysical laboratory.

Eta Carinae: Viewed from Multiple Vantage Points

NASA Technical Reports Server (NTRS)

Gull, Theodore

2007-01-01

The central source of Eta Carinae and its ejecta is a massive binary system buried within a massive interacting wind structure which envelops the two stars. However the hot, less massive companion blows a small cavity in the very massive primary wind, plus ionizes a portion of the massive wind just beyond the wind-wind boundary. We gain insight on this complex structure by examining the spatially-resolved Space Telescope Imaging Spectrograph (STIS) spectra of the central source (0.1") with the wind structure which extends out to nearly an arcsecond (2300AU) and the wind-blown boundaries, plus the ejecta of the Little Homunculus. Moreover, the spatially resolved Very Large Telescope/UltraViolet Echelle Spectrograph (VLT/UVES) stellar spectrum (one arcsecond) and spatially sampled spectra across the foreground lobe of the Homunculus provide us vantage points from different angles relative to line of sight. Examples of wind line profiles of Fe II, and the.highly excited [Fe III], [Ne III], [Ar III] and [S III)], plus other lines will be presented.

A new estimation of HD/2H2 at high redshift using the spectrum of the quasar J 2123-0050

NASA Astrophysics Data System (ADS)

Klimenko, V. V.; Balashev, S. A.; Ivanchik, A. V.; Varshalovich, D. A.

2015-12-01

We present a new analysis of the quasar spectrum J 2123-0050 obtained using VLT/UVES. The H2/HD absorption system at z = 2.059 was analysed. This system consists of two subsystems with zA = 2.05933 and zB = 2.05955. The HD lines have been detected only in subsystem A with the column density of log N = 13.87 ± 0.06. We have determined the column density of H2 in this subsystem, log N = 17.93 ± 0.01, which is about three times larger than estimation derived early from analyses of quasar spectrum obtained using KECK/HIRES [1]. The derived ratio HD/2H2 = (4.28 ± 0.60) × 10-5 is the largest in quasar spectra, nevertheless it coincides with the primordial deuterium abundance within 2σ error. Additionally, we have found some evidence in the partial covering effect for the H2 system.

VizieR Online Data Catalog: Equivalent width of 21 RR Lyrae stars (Pancino+, 2015)

NASA Astrophysics Data System (ADS)

Pancino, E.; Britavskiy, N.; Romano, D.; Cacciari, C.; Mucciarelli, A.; Clementini, G.

2015-02-01

Equivalent widths and atomic data of the absorption lines used in the abundance analysis, for each separate exposure at different phases. Observations of 15 RR Lyrae stars (DR And, X Ari, TW Boo, RZ Cam, RX Cet, U Com, RV CrB, SW CVn, UZ CVn, AE Dra, SZ Gem, VX Her, DH Hya, TU UMa, and RV UMa) and one BL Her star (UY Eri) were carried out with SARG@TNG, operated on the island of La Palma, Spain, during two separate runs in 2009 March and between September and November. Eight stars (SW Aqr, TW Cap, DH Hya, V Ind, SS Leo, V716 Oph, BK Tuc, and UV Vir) were observed with UVES@VLT, between 2009 April and August in service mode. (3 data files).

VizieR Online Data Catalog: Spectroscopy of globular clusters (Larsen+, 2018)

NASA Astrophysics Data System (ADS)

Larsen, S. S.; Brodie, J. P.; Wasserman, A.; Strader, J.

2018-01-01

New observations of globular clusters in NGC 147 and NGC 6822 were obtained with the HIRES spectrograph on the Keck I telescope on 5 Oct 2015 and 25 Sep 2016. We also include older HIRES observations of four GCs in M33. The spectra are the same as those used by Larsen et al. (2002AJ....124.2615L). In addition to the HIRES observations, we include our previously published VLT/UVES spectra of GCs in the Fornax and WLM galaxies (Larsen et al. 2012A&A...546A..53L, 2014A&A...565A..98L) and we refer to our previous papers for details on the observational strategy and data reduction. These tables contain the individual abundance measurements for each cluster. (16 data files).

Physical conditions in the neutral interstellar medium at z = 2.43 toward Q 2348-011

NASA Astrophysics Data System (ADS)

Noterdaeme, P.; Petitjean, P.; Srianand, R.; Ledoux, C.; Le Petit, F.

2007-07-01

Aims:We aim at deriving the physical conditions in the neutral gas associated with damped Lyman-α systems using observation and analysis of H2 and C i absorptions. Methods: We obtained a high-resolution VLT-UVES spectrum of the quasar Q 2348-011 over a wavelength range that covers most of the prominent metal and molecular absorption lines from the log N(H i) = 20.50 ± 0.10 damped Lyman-α system at z_abs=2.4263. We detected H2 in this system and measured column densities of H2, C i, C i^*, C i**, Si ii, P ii, S ii, Fe ii, and Ni ii. From the column density ratios and, in particular, the relative populations of H2 rotational and C i fine-structure levels, we derived the physical conditions in the gas (relative abundances, dust-depletion, particle density, kinetic temperature, and ionising flux) and discuss physical conditions in the neutral phase. Results: Molecular hydrogen was detected in seven components in the first four rotational levels (J = 0-3) of the vibrational ground state. Absorption lines of H2 J=4 (resp. J = 5) rotational levels are detected in six (resp. two) of these components. This leads to a total molecular fraction of log f ≃ -1.69+0.37-0.58. Fourteen components are needed to reproduce the metal-line profiles. The overall metallicity is found to be -0.80, -0.62, -1.17 ± 0.10 for, respectively, [Si/H], [S/H] and [Fe/H]. We confirm the earlier findings that there is a correlation between log N(Fe ii)/N(S ii) and log N(Si ii)/N(S ii) from different components indicative of a dust-depletion pattern. Surprisingly, however, the depletion of metals onto dust in the H2 components is not large in this system: [Fe/S] = -0.8 to -0.1. The gas in H2-bearing components is found to be cold but still hotter than similar gas in our Galaxy (T > 130 K, instead of typically 80 K) and dense (n ˜ 100-200 cm-3). There is an anti-correlation (R=-0.97) between the logarithm of the photo-absorption rate, log β_0, and log N(H2)/N(C i) derived for each H2 component. We show that this is mostly due to shielding effects and imply that the photo-absorption rate β0 is a good indicator of the physical conditions in the gas. We find that the gas is immersed in an intense UV field, about one order of magnitude higher than in the solar vicinity. These results suggest that the gas in H2-bearing DLAs is clumpy, and star-formation occurs in the associated object. Based on observations carried out at the European Southern Observatory (ESO) under prog. ID No. 072.A-0346 with the UVES spectrograph installed at the Very Large Telescope (VLT) Unit 2, Kueyen, on Cerro Paranal, Chile.

Is the Ejecta of ETA Carinae Overabundant or Overexcited

NASA Technical Reports Server (NTRS)

Gull, Theodore; Davidson, Kris; Johansson, Sveneric; Damineli, Augusto; Ishibashi, Kaxunori; Corcoran, Michael; Hartman, Henrick; Viera, Gladys; Nielsen, Krister

2003-01-01

The ejecta of Eta Carinae, revealed by HST/STIS, are in a large range of physical conditions. As Eta Carinae undergoes a 5.52 period, changes occur in nebular emission and nebular absorption. "Warm" neutral regions, partially ionized regions, and fully ionized regions undergo significant changes. Over 2000 emission lines, most of Fe-like elements, have been indentified in the Weigelt blobs B and D. Over 500 emission lines have been indentified in the Strontium Filament. An ionized Little Homunculus is nestled within the neutral-shelled Homunculus. In line of sight, over 500 nebular absorption lines have been identified with up to twenty velocity components. STIS is following changes in many nebular emission and absorption lines as Eta Carinae approaches the minimum, predicted to be in June/July 2003, during the General Assembly. Coordinated observations with HST, CHANDRA, RXTE, FUSE, UVES/VLT, Gemini and other observatories are following this minimum.

Scientific planning for the VLT and VLTI

NASA Astrophysics Data System (ADS)

Leibundgut, B.; Berger, J.-P.

2016-07-01

An observatory system like the VLT/I requires careful scientific planning for operations and future instruments. Currently the ESO optical/near-infrared facilities include four 8m telescopes, four (movable) 1.8m telescopes used exclusively for interferometry, two 4m telescopes and two survey telescopes. This system offers a large range of scientific capabilities and setting the corresponding priorities depends good community interactions. Coordinating the existing and planned instrumentation is an important aspect for strong scientific return. The current scientific priorities for the VLT and VLTI are pushing for the development of the highest angular resolution imaging and astrometry, integral field spectroscopy and multi-object spectroscopy. The ESO 4m telescopes on La Silla will be dedicated to time domain spectroscopy and exo-planet searches with highly specialized instruments. The next decade will also see a significant rise in the scientific importance of massive ground and space-based surveys. We discuss how future developments in astronomical research could shape the VLT/I evolution.

Opto-mechanical design of a new cross dispersion unit for the CRIRES+ high resolution spectrograph for the VLT

NASA Astrophysics Data System (ADS)

Lizon, Jean Louis; Klein, Barbara; Oliva, Ernesto; Löwinger, Tom; Anglada Escude, Guillem; Baade, Dietrich; Bristow, Paul; Dorn, Reinhold J.; Follert, Roman; Grunhut, Jason; Hatzes, Artie; Heiter, Ulrike; Ives, Derek; Jung, Yves; Kerber, Florian; Lockhart, Matt; Marquart, Thomas; Origlia, Livia; Pasquini, Luca; Paufique, Jerome; Piskunov, N.; Pozna, Eszter; Reiners, Ansgar; Smette, Alain; Smoker, Jonathan; Seemann, Ulf; Stempels, Eric; Valenti, Elena

2014-07-01

CRIRES is one of the few IR (0.92-5.2 μm) high-resolution spectrographs in operation at the VLT since 2006. Despite good performance it suffers a limitation that significantly hampers its ability: a small spectral coverage per exposure. The CRIRES upgrade (CRIRES+) proposes to transform CRIRES into a cross-dispersed spectrograph while maintaining the high resolution (100000) and increasing the wavelength coverage by a factor 10 compared to the current capabilities. A major part of the upgrade is the exchange of the actual cryogenic pre-disperser module by a new cross disperser unit. In addition to a completely new optical design, a number of important changes are required on key components and functions like the slit unit and detectors units. We will outline the design of these new units fitting inside a predefined and restricted space. The mechanical design of the new functions including a description and analysis will be presented. Finally we will present the strategy for the implementation of the changes.

Recovering the colour-dependent albedo of exoplanets with high-resolution spectroscopy: from ESPRESSO to the ELT.

NASA Astrophysics Data System (ADS)

Martins, J. H. C.; Figueira, P.; Santos, N. C.; Melo, C.; Garcia Muñoz, A.; Faria, J.; Pepe, F.; Lovis, C.

2018-05-01

The characterization of planetary atmospheres is a daunting task, pushing current observing facilities to their limits. The next generation of high-resolution spectrographs mounted on large telescopes - such as ESPRESSO@VLT and HIRES@ELT - will allow us to probe and characterize exoplanetary atmospheres in greater detail than possible to this point. We present a method that permits the recovery of the colour-dependent reflectivity of exoplanets from high-resolution spectroscopic observations. Determining the wavelength-dependent albedo will provide insight into the chemical properties and weather of the exoplanet atmospheres. For this work, we simulated ESPRESSO@VLT and HIRES@ELT high-resolution observations of known planetary systems with several albedo configurations. We demonstrate how the cross correlation technique applied to theses simulated observations can be used to successfully recover the geometric albedo of exoplanets over a range of wavelengths. In all cases, we were able to recover the wavelength dependent albedo of the simulated exoplanets and distinguish between several atmospheric models representing different atmospheric configurations. In brief, we demonstrate that the cross correlation technique allows for the recovery of exoplanetary albedo functions from optical observations with the next generation of high-resolution spectrographs that will be mounted on large telescopes with reasonable exposure times. Its recovery will permit the characterization of exoplanetary atmospheres in terms of composition and dynamics and consolidates the cross correlation technique as a powerful tool for exoplanet characterization.

Ages and Heavy Element Abundances from Very Metal-poor Stars in the Sagittarius Dwarf Galaxy

NASA Astrophysics Data System (ADS)

Hansen, Camilla Juul; El-Souri, Mariam; Monaco, Lorenzo; Villanova, Sandro; Bonifacio, Piercarlo; Caffau, Elisabetta; Sbordone, Luca

2018-03-01

Sagittarius (Sgr) is a massive disrupted dwarf spheroidal galaxy in the Milky Way halo that has undergone several stripping events. Previous chemical studies were restricted mainly to a few, metal-rich ([Fe/H] \\gtrapprox -1) stars that suggested a top-light initial mass function (IMF). Here we present the first high-resolution, very metal-poor ([Fe/H] =‑1 to ‑3) sample of 13 giant stars in the main body of Sgr. We derive abundances of 13 elements, namely C, Ca, Co, Fe, Sr, Ba, La, Ce, Nd, Eu, Dy, Pb, and Th, that challenge the interpretation based on previous studies. Our abundances from Sgr mimic those of the metal-poor halo, and our most metal-poor star ([Fe/H] ∼ -3) indicates a pure r-process pollution. Abundances of Sr, Pb, and Th are presented for the first time in Sgr, allowing for age determination using nuclear cosmochronology. We calculate ages of 9+/- 2.5 {Gyr}. Most of the sample stars have been enriched by a range of asymptotic giant branch (AGB) stars with masses between 1.3 and 5 M ⊙. Sgr J190651.47–320147.23 shows a large overabundance of Pb (2.05 dex) and a peculiar abundance pattern best fit by a 3 M ⊙ AGB star. Based on star-to-star scatter and observed abundance patterns, a mixture of low- and high-mass AGB stars and supernovae (15–25 M ⊙) is necessary to explain these patterns. The high level (0.29 ± 0.05 dex) of Ca indicates that massive supernovae must have existed and polluted the early ISM of Sgr before it lost its gas. This result is in contrast with a top-light IMF with no massive stars polluting Sgr. Based on data obtained UVES/VLT ID: 083.B-0774, 075.B-0127.

Main High-Resolution Near-IR Spectrometer for the VLT

NASA Astrophysics Data System (ADS)

Piskunov, N.

2017-06-01

We present the ongoing CRISES+ project on the development of a cross-dispersed high resolution near-infrared spectrometer for the ESO Very Large Telescope. The presentation highlights the relation between science objectives, technical solutions, and the structure of the project. We also share some of the insights on the implementation and management of the project that are crucial for keeping the tight time-line through efficient interaction between consortium members.

Glowing Hot Transiting Exoplanet Discovered

NASA Astrophysics Data System (ADS)

2003-04-01

VLT Spectra Indicate Shortest-Known-Period Planet Orbiting OGLE-TR-3 Summary More than 100 exoplanets in orbit around stars other than the Sun have been found so far. But while their orbital periods and distances from their central stars are well known, their true masses cannot be determined with certainty, only lower limits. This fundamental limitation is inherent in the common observational method to discover exoplanets - the measurements of small and regular changes in the central star's velocity, caused by the planet's gravitational pull as it orbits the star. However, in two cases so far, it has been found that the exoplanet's orbit happens to be positioned in such a way that the planet moves in front of the stellar disk, as seen from the Earth. This "transit" event causes a small and temporary dip in the star's brightness, as the planet covers a small part of its surface, which can be observed. The additional knowledge of the spatial orientation of the planetary orbit then permits a direct determination of the planet's true mass. Now, a group of German astronomers [1] have found a third star in which a planet, somewhat larger than Jupiter, but only half as massive, moves in front of the central star every 28.5 hours . The crucial observation of this solar-type star, designated OGLE-TR-3 [2] was made with the high-dispersion UVES spectrograph on the Very Large Telescope (VLT) at the ESO Paranal Observatory (Chile). It is the exoplanet with the shortest period found so far and it is very close to the star, only 3.5 million km away. The hemisphere that faces the star must be extremely hot, about 2000 °C and the planet is obviously losing its atmosphere at high rate . PR Photo 10a/03 : The star OGLE-TR-3 . PR Photo 10b/03 : VLT UVES spectrum of OGLE-TR-3. PR Photo 10c/03 : Relation between stellar brightness and velocity (diagram). PR Photo 10d/03 : Observed velocity variation of OGLE-TR-3. PR Photo 10e/03 : Observed brightness variation of OGLE-TR-3. The search for exoplanets More than 100 planets in orbit around stars other than the Sun have been found so far. These "exoplanets" come in many different sizes and they move in a great variety of orbits at different distances from their central star, some nearly round and others quite elongated. Some planets are five to ten times more massive than the largest one in the solar system, Jupiter - the lightest exoplanets known at this moment are about half as massive as Saturn, i.e. about 50 times more massive than the Earth. Astronomers are hunting exoplanets not just to discover more such objects, but also to learn more about the apparent diversity of planetary systems. The current main research goal is to eventually discover an Earth-like exoplanet, but the available telescopes and instrumentation are still not "sensitive" enough for this daunting task. However, also in this context, it is highly desirable to know not only the orbits of the observable exoplanets, but also their true masses . But this is not an easy task. Masses of exoplanets Virtually all exoplanets detected so far have been found by an indirect method - the measurement of stellar velocity variations . It is based on the gravitational pull of the orbiting planet that causes the central star to move a little back and forth; the heavier the planet, the greater is the associated change in the star's velocity. This technique is rapidly improving: the new HARPS spectrograph (High Accuracy Radial Velocity Planet Searcher) , now being tested on the 3.6-m telescope at the ESO La Silla Observatory , can measure such stellar motions with an unrivalled accuracy of about 1 metre per second (m/s), cf. ESO PR 06/03 . It will shortly be able to search for exoplanets only a few times more massive than the Earth. However, velocity measurements alone do not allow to determine the true mass of the orbiting planet. Because of the unknown inclination of the planetary orbit (to the line-of-sight), they only provide a lower limit to this mass . Additional information about this orbital inclination is therefore needed to derive the true mass of an exoplanet. The transit method Fortunately, this information becomes available if the exoplanet is known to move across ("transit") the star's disk, as seen from the Earth; the orbital plane must then necessarily be very near the line-of-sight. This phenomenon is exactly the same that happens in our own solar system, when the inner planets Mercury and Venus pass in front of the solar disk, as seen from the Earth [3]. A solar eclipse (caused by the Moon moving in front of the Sun) is a more extreme case of the same type of event. During such an exoplanet transit, the observed brightness of the star will decrease slightly because the planet blocks a part of the stellar light. The larger the planet, the more of the light is blocked and the more the brightness of the star will decrease. A study of the way this brightness changes with time (astronomers refer to the "light curve"), when combined with radial velocity measurements, allows a complete determination of the planetary orbit, including the exact inclination. It also provides accurate information about the planet's size, true mass and hence, density. The chances that a particular exoplanet passes in front of the disk of its central star as seen from the Earth are small. However, because of the crucial importance of such events in order to characterize exoplanets fully, astronomers have for some time been actively searching for stars that experience small regularly occurring "brightness dips" that might possibly be caused by exoplanetary transits. The OGLE list Last year, a first list of 59 such possible cases of stars with transiting planets was announced by the Optical Gravitational Lensing Experiment (OGLE) [2]. These stars were found - within a sample of about 5 million stars observed during a 32-day period - to exhibit small and regular brightness dips that might possibly be caused by transits of an exoplanet. For one of these stars, OGLE-TR-56 , a team of American astronomers soon thereafter observed slight variations of the velocity , strongly indicating the presence of an exoplanet around that star. UVES spectra of OGLE-TR-3 ESO PR Photo 10a/03 ESO PR Photo 10a/03 [Preview - JPEG: 400 x 466 pix - 41k [Normal - JPEG: 800 x 931 pix - 280k] ESO PR Photo 10b/03 ESO PR Photo 10b/03 [Preview - JPEG: 492 x 400 pix - 52k [Normal - JPEG: 984 x 800 pix - 224k] Captions : PR Photo 10a/03 shows the 16.5-mag star OGLE-TR-3 , a solar-like star in the direction of the Galactic Center, discovered during an extensive photometric search for planetary and low-luminosity object transits [2]. The image is reproduced from an I-band CCD frame of a 1 x 1 arcmin 2 sky field. North is up and East is left. PR Photo 10b/03 displays a small portion of a high-dispersion spectrum of OGLE-TR-3 , obtained with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope at the Paranal Observatory (Chile). It is divided into five adjacent wavelength intervals and represents the mean of ten 1-hour spectral exposures. The fully drawn curve shows the spectrum of the "best fitting" stellar model from which the composition, temperature, mass, age of OGLE-TR-3 were deduced. Now, a team of German and ESO astronomers [1] have used the UVES High-Dispersion Spectrograph on the 8.2-m VLT KUEYEN telescope at the Paranal Observatory (Chile) to obtain very detailed spectra of another star on that list, OGLE-TR-3 , cf. PR Photos 10a-b/03 . Over a period of one month, a total of ten high-resolution spectra - each with an exposure time of about one hour - were obtained of the 16.5-mag object, i.e. its brightness is about 16,000 fainter that what can be perceived with the unaided eye. A careful evaluation shows that OGLE-TR-3 is very similar to the Sun, with a temperature of about 5800 °C (6100 K). And most interestingly, it undergoes velocity variations of the order of 120 m/s . The exoplanet at OGLE-TR-3 ESO PR Photo 10c/03 ESO PR Photo 10c/03 [Preview - JPEG: 400 x 507 pix - 24k [Normal - JPEG: 800 x 1014 pix - 95k] ESO PR Photo 10d/03 ESO PR Photo 10d/03 [Preview - JPEG: 466 x 400 pix - 20k [Normal - JPEG: 932 x 800 pix - 120k] ESO PR Photo 10e/03 ESO PR Photo 10e/03 [Preview - JPEG: 510 x 200 pix - 21k [Normal - JPEG: 1024 x 400 pix - 120k] Captions : PR Photo 10c/03 illustrates the relationship between the variations in stellar brightness and velocity, caused by an orbiting exoplanet that transits the disk of its central star. Consecutive positions of the planet in its (circular) orbit are marked by black dots, with the motion from left to right. The figure has been drawn to scale, i.e. the dots actually represent the size of the planet itself. At the top is the view of the planetary orbit from above - below a view from the Earth with the planetary transit. Further down, the lightcurve with a brightness (intensity) dip when the planet blocks a small part of the star's light is shown, and at the bottom the corresponding change in the star's velocity. Before the transit, when the planet moves towards us, the star moves in the opposite direction, i.e. away from us and the velocity is positive; during the transit, the relative velocity is zero and later is becomes negative as the star moves towards us. PR Photo 10d/03 displays the velocity variation of the star OGLE-TR-3 , as measured from ten VLT-UVES spectra (each with 1-hour exposure time) and plotted according to the "photometric phase". This means that the planetary transit occurs at phase 0 (left) and again at phase 1 (right). The observed variation is in agreement with the expected one, cf. PR Photo 10c/03 . The fully drawn curve represents the best fit to the observations (velocity variation about 120 m/s) - the mass of the planet is derived from this. PR Photo 10e/03 shows the brightness variation ("light-curve") of the star OGLE-TR-3 obtained during the OGLE observations [2]. The crosses correspond to the observations and the fully drawn curve represents a model fit, with the stellar parameters from the analysis of the UVES spectra (1 solar radius and 1 solar mass) and the planetary parameters from the velocity analysis (0.6 Jupiter mass). The best fit allows determination of the planet's size as about 200,000 km (1.4 times the size of Jupiter). The 2 per cent dip in the brightness of OGLE-TR-3 , as observed during the OGLE programme, occurs every 28 hours 33 minutes (1.1899 days), cf. PR Photo 10e/03 . The UVES velocity measurements ( PR Photo 10d/03 ) fit this period well and reveal, with high probability, the presence of an exoplanet orbiting OGLE-TR-3 with this period. In any case, the observations firmly exclude that the well observed brightness variations could be due to a small stellar companion. A red dwarf star would have caused velocity variations of 15 km/s and a brown dwarf star 2.5 km/s; both would have been easy to observe with UVES, and it is clear that such variations can be excluded. Although the available observations are still insufficient to allow an accurate determination of the planetary properties, the astronomers provisionally deduce a true mass of the planet of the order of one half of that of Jupiter . The density is found to be about 250 kg/m 3 , only one-quarter of that of water or one-fifth of that of Jupiter, so the planet is quite big for this mass - a bit "blown up". It is obviously a planet of the gaseous type . A very hot planet The orbital period, 28 hours 33 minutes (1.1899 days), is the shortest known for any exoplanet and the distance between the star and the planet is correspondingly small, only 3.5 million kilometres . The temperature of the side of the planet facing the star must therefore be very high, of the order of 2000 °C . Clearly, the planet must be losing its atmosphere by evaporation. The astronomers also conclude that it might in fact be possible to observe this exoplanet directly because of its comparatively strong infrared radiation. An attempt to do so will soon be made. As only the third exoplanet found this way (after those at the stars HD209458 and OGLE-TR-56 ), the new object confirms the current impression that a considerable number of stars may possess giant planets in close orbits. Since such planets cannot form so close to their parent star, they must have migrated inwards to the current orbit from a much larger, initial distance. It is not known at this time with certainty how this might happen. Future prospects It is expected that more observational campaigns will be made to search for transiting planets around other stars. There is good hope that OGLE-TR-3 and OGLE-TR-56 are just the first two of a substantial number of exoplanets to be discovered this way. Some years from now, searches will also begin from dedicated space observatories, e.g. ESA's Eddington and Darwin , and NASA's Kepler .

High Redshift Radio Galaxies: Laboratories for Massive Galaxy and Cluster Formation in the Early Universe

DTIC Science & Technology

2010-01-01

Lyα (blue, resolution ∼1”) obtained with ESO’s very Large Telescope (VLT), delineating the gaseous nebula and radio 8 GHz contours (red, resolution...0.3”) obtained with NRAO’s VLA, delineating the non-thermal radio emission. The gaseous nebula extends for >200 kpc and is comparable in size with the

Molecular hydrogen in the zabs = 2.66 damped Lyman-α absorber towards Q J 0643-5041. Physical conditions and limits on the cosmological variation of the proton-to-electron mass ratio

NASA Astrophysics Data System (ADS)

Albornoz Vásquez, D.; Rahmani, H.; Noterdaeme, P.; Petitjean, P.; Srianand, R.; Ledoux, C.

2014-02-01

Context. Molecular hydrogen in the interstellar medium (ISM) of high-redshift galaxies can be detected directly from its UV absorption imprinted in the spectrum of background quasars. Associated absorption from H i and metals allow for the study of the chemical enrichment of the gas, while the analysis of excited species and molecules make it possible to infer the physical state of the ISM gas. In addition, given the numerous H2 lines usually detected, these absorption systems are unique tools to constrain the cosmological variation of the proton-to-electron mass ratio, μ. Aims: We intend to study the chemical and physical state of the gas in the H2-bearing cloud at zabs = 2.658601 towards the quasar Q J 0643-5041 (zem = 3.09) and to derive a useful constraint on the variation of μ. Methods: We use high signal-to-noise ratio, high-resolution VLT-UVES data of Q J 0643-5041 amounting to a total of more than 23 h exposure time and fit the H i, metals, and H2 absorption features with multiple-component Voigt profiles. We study the relative populations of H2 rotational levels and the fine-structure excitation of neutral carbon to determine the physical conditions in the H2-bearing cloud. Results: We find some evidence for part of the quasar broad-line emission region not being fully covered by the H2-bearing cloud. We measure a total neutral hydrogen column density of log N(H i)(cm-2) = 21.03 ± 0.08. Molecular hydrogen is detected in several rotational levels, possibly up to J = 7, in a single component. The corresponding molecular fraction is log f = -2.19+0.07-0.08, where f = 2N(H2)/(2N(H2)+ N(H i)). The H2 Doppler parameter is of the order of 1.5 km s-1 for J = 0, 1, and 2 and larger for J> 2. The molecular component has a kinetic temperature of Tkin ≃ 80 K, which yields a mean thermal velocity of ~1 km s-1, consistent with the Doppler broadening of the lines. The UV ambient flux is of the order of the mean ISM Galactic flux. We discuss the possible detection of HD and derive an upper limit of log N(HD) ≲ 13.65 ± 0.07 leading to log HD/(2 × H2) ≲ - 5.19 ± 0.07, which is consistently lower than the primordial D/H ratio. Metals span ~210 km s-1 with [Zn/H] = -0.91 ± 0.09 relative to solar, with iron depleted relative to zinc [Zn/Fe] = 0.45 ± 0.06, and with the rare detection of copper. We follow the procedures used in our previous works to derive a constraint on the cosmological variation of μ, Δμ/μ = (7.4 ± 4.3stat ± 5.1syst) × 10-6. Based on data obtained with the Ultraviolet and Visual Echelle Spectrograph (UVES) at the European Southern Observatory Very Large Telescope (ESO-VLT), under program ID 080.A-0288(A) and archival data.Appendices are available in electronic form at http://www.aanda.orgReduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A88

Survey for Ortho-to-Para Abundance Ratios (OPRs) of NH2 in Comets: Revisit to the Meaning of OPRs of Cometary Volatiles

NASA Astrophysics Data System (ADS)

Kawakita, Hideyo; Shinnaka, Yoshiharu; Jehin, Emmanuel; Decock, Alice; Hutsemekers, Damien; Manfroid, Jean

2016-10-01

Since molecules having identical protons can be classified into nuclear-spin isomers (e.g., ortho-H2O and para-H2O for water) and their inter-conversions by radiative and non-destructive collisional processes are believed to be very slow, the ortho-to-para abundance ratios (OPRs) of cometary volatiles such as H2O, NH3 and CH4 in coma have been considered as primordial characters of cometary molecules [1]. Those ratios are usually interpreted as nuclear-spin temperatures although the real meaning of OPRs is in strong debate. Recent progress in laboratory studies about nuclear-spin conversion in gas- and solid-phases [2,3] revealed short-time nuclear-spin conversions for water, and we have to reconsider the interpretation for observed OPRs of cometary volatiles. We have already performed the survey for OPRs of NH2 in more than 20 comets by large aperture telescopes with high-resolution spectrographs (UVES/VLT, HDS/Subaru, etc.) in the optical wavelength region [4]. The observed OPRs of ammonia estimated from OPRs of NH2, cluster around ~1.1 (cf. 1.0 as a high-temperature limit), indicative of ~30 K as nuclear-spin temperatures. We present our latest results for OPRs of cometary NH2 and discuss about the real meaning of OPRs of cometary ammonia, in relation to OPRs of water in cometary coma. Chemical processes in the inner coma may play an important role to achieve un-equilibrated OPRs of cometary volatiles in coma.This work was financially supported by MEXT Supported Program for the Strategic Research Foundation at Private Universities, 2014-2018 (No. S1411028) (HK) and by Graint-in-Aid for JSPS Fellows, 15J10864 (YS).References:[1] Mumma & Charnley, 2011, Annu. Rev. Astro. Astrophys. 49, 471.[2] Hama & Watanabe, 2013, Chem. Rev. 113, 8783.[3] Hama et al., 2008, Science 351, 6268.[4] Shinnaka et al., 2011, ApJ 729, 81.

Spotting high-z molecular absorbers using neutral carbon. Results from a complete spectroscopic survey with the VLT

NASA Astrophysics Data System (ADS)

Noterdaeme, P.; Ledoux, C.; Zou, S.; Petitjean, P.; Srianand, R.; Balashev, S.; López, S.

2018-04-01

While molecular quasar absorption systems provide unique probes of the physical and chemical properties of the gas as well as original constraints on fundamental physics and cosmology, their detection remains challenging. Here we present the results from a complete survey for molecular gas in thirty-nine absorption systems selected solely upon the detection of neutral carbon lines in Sloan Digital Sky Survey (SDSS) spectra, without any prior knowledge of the atomic or molecular gas content. H2 is found in all twelve systems (including seven new detections) where the corresponding lines are covered by the instrument setups and measured to have logN(H2) ≳ 18, indicating a self-shielded regime. We also report seven CO detections (7/39) down to logN(CO) 13.5, including a new one, and put stringent constraints on N(CO) for the remaining 32 systems. N(CO) and N(C I) are found to be strongly correlated with N(CO)/N(C I) 1/10. This suggests that the C I-selected absorber population is probing gas deeper than the H I–H2 transition in which a substantial fraction of the total hydrogen in the cloud is in the form of H2. We conclude that targeting C I-bearing absorbers is a very efficient way to find high-metallicity molecular absorbers. However, probing the molecular content in lower-metallicity regimes as well as high-column-density neutral gas remains to be undertaken to unravel the processes of gas conversion in normal high-z galaxies. Based on observations and archival data from the European Southern Observatory (ESO) prog. IDs 060.A-9024, 072.A-0346, 278.A-5062, 080.A-0482, 080.A-0795, 081.A-0242, 081.A-0334, 082.A-0544, 082.A-0569, 083.A-0454, 084.A-0699, 086.A-0074 and 086.A-0643 using the Ultraviolet and Visual Echelle Spectrograph (UVES) and X-shooter at the Very Large Telescope (VLT), on Cerro Paranal, Chile.

Precise strong lensing mass profile of the CLASH galaxy cluster MACS 2129

NASA Astrophysics Data System (ADS)

Monna, A.; Seitz, S.; Balestra, I.; Rosati, P.; Grillo, C.; Halkola, A.; Suyu, S. H.; Coe, D.; Caminha, G. B.; Frye, B.; Koekemoer, A.; Mercurio, A.; Nonino, M.; Postman, M.; Zitrin, A.

2017-04-01

We present a detailed strong lensing (SL) mass reconstruction of the core of the galaxy cluster MACS J2129.4-0741 (zcl = 0.589) obtained by combining high-resolution Hubble Space Telescope photometry from the CLASH (Cluster Lensing And Supernovae survey with Hubble) survey with new spectroscopic observations from the CLASH-VLT (Very Large Telescope) survey. A background bright red passive galaxy at zsp = 1.36, sextuply lensed in the cluster core, has four radial lensed images located over the three central cluster members. Further 19 background lensed galaxies are spectroscopically confirmed by our VLT survey, including 3 additional multiple systems. A total of 31 multiple images are used in the lensing analysis. This allows us to trace with high precision the total mass profile of the cluster in its very inner region (R < 100 kpc). Our final lensing mass model reproduces the multiple images systems identified in the cluster core with high accuracy of 0.4 arcsec. This translates to a high-precision mass reconstruction of MACS 2129, which is constrained at a level of 2 per cent. The cluster has Einstein parameter ΘE = (29 ± 4) arcsec and a projected total mass of Mtot(<ΘE) = (1.35 ± 0.03) × 1014 M⊙ within such radius. Together with the cluster mass profile, we provide here also the complete spectroscopic data set for the cluster members and lensed images measured with VLT/Visible Multi-Object Spectrograph within the CLASH-VLT survey.

The Perfect Science Machine

NASA Astrophysics Data System (ADS)

2008-05-01

ESO celebrates 10 years since First Light of the VLT Today marks the 10th anniversary since First Light with ESO's Very Large Telescope (VLT), the most advanced optical telescope in the world. Since then, the VLT has evolved into a unique suite of four 8.2-m Unit Telescopes (UTs) equipped with no fewer than 13 state-of-the-art instruments, and four 1.8-m moveable Auxiliary Telescopes (ATs). The telescopes can work individually, and they can also be linked together in groups of two or three to form a giant 'interferometer' (VLTI), allowing astronomers to see details corresponding to those from a much larger telescope. Green Flash at Paranal ESO PR Photo 16a/08 The VLT 10th anniversary poster "The Very Large Telescope array is a flagship facility for astronomy, a perfect science machine of which Europe can be very proud," says Tim de Zeeuw, ESO's Director General. "We have built the most advanced ground-based optical observatory in the world, thanks to the combination of a long-term adequately-funded instrument and technology development plan with an approach where most of the instruments were built in collaboration with institutions in the member states, with in-kind contributions in labour compensated by guaranteed observing time." Sitting atop the 2600m high Paranal Mountain in the Chilean Atacama Desert, the VLT's design, suite of instruments, and operating principles set the standard for ground-based astronomy. It provides the European scientific community with a telescope array with collecting power significantly greater than any other facilities available at present, offering imaging and spectroscopy capabilities at visible and infrared wavelengths. Blue Flash at Paranal ESO PR Photo 16b/08 A Universe of Discoveries The first scientifically useful images, marking the official 'First Light' of the VLT, were obtained on the night of 25 to 26 May 1998, with a test camera attached to "Antu", Unit Telescope number 1. They were officially presented to the press on the 27 May, exactly ten years ago. Since then, all four Unit Telescopes and four Auxiliary Telescopes went into routine operations and the number of instruments has continued to grow, to fill all the possible positions in the telescopes where instruments can be attached. In 2007, about 500 peer-reviewed papers using data collected with VLT and VLTI instruments at Paranal were published in scientific journals. Since the start of science operations, in April 1999, the VLT has led to the publication of more than 2200 refereed papers, an average of about one paper published every single working day. "The combination of high operational efficiency, system reliability and uptime for scientific observations results in very high scientific productivity," says Andreas Kaufer, director of the La Silla Paranal Observatory. The VLT and VLTI have contributed to all areas of astronomy, including the nature of dark matter and dark energy; the extreme physics of gamma-ray bursts and supernovae; the formation, structure and evolution of galaxies; the properties of exoplanets, Solar System objects, star clusters and stellar populations, the interstellar and intergalactic medium, and of super-massive black holes in galactic nuclei, in particular the one in the Galactic Centre; and the formation of stars and planets. The stunning scientific success of the VLT has attracted new member states to ESO. In the past decade Portugal joined (in 2001, after a ten-year associate status), followed by the United Kingdom (2002), Finland (2004), Spain (2006) and the Czech Republic (2007). Austria also announced its intent to join later this year. Another measure of success is the number of observing proposals made every year for the use of the VLT, which is now above the 1900 mark. On average, the amount of time requested to use the VLT is 6 times higher than what is available. The VLT will continue to increase in power over the next decade. The first of the second-generation VLT instruments, X-Shooter, will come online this year, with KMOS, SPHERE and MUSE to follow, together with multiple laser guide stars, an adaptive secondary mirror on Yepun (UT4), and one or more third-generation instruments, including an ultra-stable high-resolution spectrograph at the combined focus. The VLTI will also be equipped with second-generation instruments. Clearly, the VLT's story has only begun. More Information The VLT was designed from the start as an integrated system of four 8.2m telescopes, including the possibility to combine the light from individual telescopes for optical interferometry, enabling stupendous spatial resolution. First light on Antu occurred in May 1998, with Kueyen, Melipal and Yepun following soon after. Most of the VLT and VLTI instruments were built in close collaboration with institutes in the member states. The first-generation instrument suite was completed in 2007 with the commissioning of CRIRES. The Paranal arsenal includes turnkey adaptive optics systems and a rapid-response mode to react to fast transient events. Recently, the near-infrared imager HAWK-I was added as a 'generation-1.5' instrument.

Does the chemical signature of TYC 8442-1036-1 originate from a rotating massive star that died in a faint explosion?

NASA Astrophysics Data System (ADS)

Cescutti, G.; Valentini, M.; François, P.; Chiappini, C.; Depagne, E.; Christlieb, N.; Cortés, C.

2016-11-01

Context. We have recently investigated the origin of chemical signatures observed in Galactic halo stars by means of a stochastic chemical evolution model. We found that rotating massive stars are a promising way to explain several signatures observed in these fossil stars. Aims: We discuss how the extremely metal-poor halo star TYC 8442-1036-1, for which we have now obtained detailed abundances from VLT-UVES spectra, fits into the framework of our previous work. Methods: We applied a standard one-dimensional (1D) LTE analysis to the spectrum of this star. We measured the abundances of 14 chemical elements; we computed the abundances for Na, Mg, Ca, Sc, Ti, V, Cr, Mn, Fe, Ni, and Zn using equivalent widths; we obtained the abundances for C, Sr, and Ba by means of synthetic spectra generated by MOOG. Results: We find an abundance of [Fe/H] = -3.5 ±0.13 dex based on our high-resolution spectrum; this points to an iron content that is lower by a factor of three (0.5 dex) compared to that obtained by a low-resolution spectrum. The star has a [C/Fe] = 0.4 dex, and it is not carbon enhanced like most of the stars at this metallicity. Moreover, this star lies in the plane [Ba/Fe] versus [Fe/H] in a relatively unusual position, shared by a few other Galactic halo stars, which is only marginally explained by our past results. Conclusions: The comparison of the model results with the chemical abundance characteristics of this group of stars can be improved if we consider in our model the presence of faint supernovae coupled with rotating massive stars. These results seem to imply that rotating massive stars and faint supernovae scenarios are complementary to each other, and are both required in order to match the observed chemistry of the earliest phases of the chemical enrichment of the Universe. Based on observations made with the ESO Very Large Telescope at Paranal Observatory, Chile (ID 094.B-0781(A); P.I. G. Cescutti).

The "+" for CRIRES: enabling better science at infrared wavelength and high spectral resolution at the ESO VLT

NASA Astrophysics Data System (ADS)

Dorn, Reinhold J.; Follert, Roman; Bristow, Paul; Cumani, Claudio; Eschbaumer, Siegfried; Grunhut, Jason; Haimerl, Andreas; Hatzes, Artie; Heiter, Ulrike; Hinterschuster, Renate; Ives, Derek J.; Jung, Yves; Kerber, Florian; Klein, Barbara; Lavaila, Alexis; Lizon, Jean Louis; Löwinger, Tom; Molina-Conde, Ignacio; Nicholson, Belinda; Marquart, Thomas; Oliva, Ernesto; Origlia, Livia; Pasquini, Luca; Paufique, Jérôme; Piskunov, Nikolai; Reiners, Ansgar; Seemann, Ulf; Stegmeier, Jörg; Stempels, Eric; Tordo, Sebastien

2016-08-01

The adaptive optics (AO) assisted CRIRES instrument is an IR (0.92 - 5.2 μm) high-resolution spectrograph was in operation from 2006 to 2014 at the Very Large Telescope (VLT) observatory. CRIRES was a unique instrument, accessing a parameter space (wavelength range and spectral resolution) up to now largely uncharted. It consisted of a single-order spectrograph providing long-slit (40 arcsecond) spectroscopy with a resolving power up to R=100 000. However the setup was limited to a narrow, single-shot, spectral range of about 1/70 of the central wavelength, resulting in low observing efficiency for many scientific programmes requiring a broad spectral coverage. The CRIRES upgrade project, CRIRES+, transforms this VLT instrument into a cross-dispersed spectrograph to increase the simultaneously covered wavelength range by a factor of ten. A new and larger detector focal plane array of three Hawaii 2RG detectors with 5.3 μm cut-off wavelength will replace the existing detectors. For advanced wavelength calibration, custom-made absorption gas cells and an etalon system will be added. A spectro-polarimetric unit will allow the recording of circular and linear polarized spectra. This upgrade will be supported by dedicated data reduction software allowing the community to take full advantage of the new capabilities offered by CRIRES+. CRIRES+ has now entered its assembly and integration phase and will return with all new capabilities by the beginning of 2018 to the Very Large Telescope in Chile. This article will provide the reader with an update of the current status of the instrument as well as the remaining steps until final installation at the Paranal Observatory.

Masses and activity of AB Doradus B a/b. The age of the AB Dor quadruple system revisited

NASA Astrophysics Data System (ADS)

Wolter, U.; Czesla, S.; Fuhrmeister, B.; Robrade, J.; Engels, D.; Wieringa, M.; Schmitt, J. H. M. M.

2014-10-01

We present a multiwavelength study of the close binary AB Dor Ba/b (Rst137B). Our study comprises astrometric orbit measurements, optical spectroscopy, X-ray and radio observations. Using all available adaptive optics images of AB Dor B taken with VLT/NACO from 2004 to 2009, we tightly constrain its orbital period to 360.6 ± 1.5 days. We present the first orbital solution of Rst 137B and estimate the combined mass of AB Dor Ba+b as 0.69+0.02-0.24 M⊙, slightly exceeding previous estimates based on IR photometry. Our determined orbital inclination of Rst 137B is close to the axial inclination of AB Dor A inferred from Doppler imaging. Our VLT/UVES spectra yield high rotational velocities of ≥30 km s-1 for both components Ba and Bb, in accord with previous measurements, which corresponds to rotation periods significantly shorter than one day. Our combined spectral model, using PHOENIX spectra, yields an effective temperature of 3310 ± 50 K for the primary and approximately 60 K less for the secondary. The optical spectra presumably cover a chromospheric flare and show that at least one component of Rst 137B is significantly active. Activity and weak variations are also found in our simultaneous XMM-Newton observations, while our ATCA radio data yield constant fluxes at the level of previous measurements. Using evolutionary models, our newly determined stellar parameters confirm that the age of Rst 137B is between 50 and 100 Myr. Based on observations collected at the European Southern Observatory, Paranal, Chile, 383.D-1002(A) and the ESO Science Archive Facility. Using data obtained with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member states and NASA. Using data obtained with the Australia Telescope Compact Array (ATCA) operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO).

Second Announcement - ESO/ST-ECF Workshop on NICMOS and the VLT: A New Era of High-Resolution Near-Infrared Imaging and Spectroscopy - May 26-27, 1998 - Hotel Baia di Nora, Pula, Sardinia, Italy

NASA Astrophysics Data System (ADS)

1998-03-01

ST-ECF and ESO are organising in collaboration with the NICMOS IDT and STScI a workshop on near infrared imaging from space and ground. The purpose of the workshop is to review what has been achieved with the Near Infrared and Multi Object Spectrograph (NICMOS) on board of HST, what can be achieved in the remaining lifetime of the instrument, and how NICMOS observations can be optimised taking into account the availability of IR imaging and spectroscopy on ESO's Very large Telescope (VLT) in the near future. The meeting will be held in May 1998, about one year after science observations started with NICMOS, and about half a year before the Infrared Spectrometer and Array Camera (ISAAC) starts to operate on the VLT. Currently, it is expected that NICMOS will operate until the end of 1998.

UVES Investigates the Environment of a Very Remote Galaxy

NASA Astrophysics Data System (ADS)

2002-03-01

Surplus of Intergalactic Material May Be Young Supercluster Summary Observations with ESO's Very Large Telescope (VLT) have enabled an international group of astronomers [1] to study in unprecedented detail the surroundings of a very remote galaxy, almost 12 billion light-years distant [2]. The corresponding light travel time means that it is seen at a moment only about 3 billion years after the Big Bang. This galaxy is designated MS 1512-cB58 and is the brightest known at such a large distance and such an early time. This is due to a lucky circumstance: a massive cluster of galaxies ( MS 1512+36 ) is located about halfway along the line-of-sight, at a distance of about 7 billion light-years, and acts as a gravitational "magnifying glass". Thanks to this lensing effect, the image of MS1512-cB58 appears 50 times brighter . Nevertheless, the apparent brightness is still as faint as magnitude 20.6 (i.e., nearly 1 million times fainter than what can be perceived with the unaided eye). Moreover, MS 1512-cB58 is located 36° north of the celestial equator and never rises more than 29° above the horizon at Paranal. It was therefore a great challenge to secure the present observational data with the UVES high-dispersion spectrograph on the 8.2-m VLT KUEYEN telescope . The extremely detailed UVES-spectrum of MS 1512-cB58 displays numerous signatures (absorption lines) of intergalactic gas clouds along the line-of-sight . Some of the clouds are quite close to the galaxy and the astronomers have therefore been able to investigate the distribution of matter in its immediate surroundings. They found an excess of material near MS 1512-cB58, possible evidence of a young supercluster of galaxies , already at this very early epoch. The new observations thus provide an invaluable contribution to current studies of the birth and evolution of structures in the early Universe. This is the first time this kind of observation has ever been done of a galaxy at such a large distance . All previous studies were based on much more luminous quasars (QSOs - extremely active galaxy nuclei). However, any investigation of the intergalactic matter around a quasar is complicated by the strong radiation and consequently, high ionization of the gas by the QSO itself, rendering an unbiased assessment of the gas distribution impossible. PR Photo 08a/02 : HST photo of MS 1512-cB58 . PR Photo 08b/02 : UVES spectrum of MS 1512-cB58. PR Photo 08c/02 : UVES spectrum of MS 1512-cB58 ( detail ). Clustering in the Early Universe ESO PR Photo 08a/02 ESO PR Photo 08a/02 [Preview - JPEG: 400 x 614 pix - 304k] [Normal - JPEG: 1200 x 1843 pix - 1.8M] Caption : PR Photo 08a/02 shows the gravitationally amplified, elongated image of the very distant, 20.6-mag galaxy MS 1512-cB58 (indicated with an arrow), as seen in the field of the distant cluster of galaxies MS 1512+36 . The photo is based on exposures with the NASA/ESA Hubble Space Telescope (HST). Technical information about the photo is available below. With new and powerful astronomical telescopes, the exploration of the young Universe is progressing rapidly . By means of highly efficient instruments, scientists are now probing the objects seen at these early times in ever greater detail, painstakingly gaining precious new knowledge about these crucial evolutionary stages. They form an integral part of the long chain of events that has ultimately led to our own existence - no wonder that we would like to know more about those remote times! One of the key questions now asked by cosmologists is how the matter in the early Universe assembled into larger structures . With plenty of gaseous material available, it appears that contraction set in rather soon after the Big Bang, perhaps only a few hundred million years after this initial explosion. Stars and proto-galaxies formed, a web-like structure emerged (cf. ESO PR 11/01 ) and at some moment, these larger building blocks began to gather into "clusters" and "clusters of clusters" (superclusters) . This process took time and it is not yet known when the first major clusters of galaxies formed. However, recent results from the ESO Very Large Telescope at Paranal are casting new light on those early events and may actually provide evidence of an extensive cluster of clouds, perhaps a real supercluster , as early as only 3 billion years after the Big Bang. The lighthouse and the forest In order to investigate the large-scale structure of the Universe, astronomers have since some time employed the powerful technique of spectral analysis of the light from remote "lighthouses" (or "beacons") . One of the strongest spectral lines seen in astronomical objects is the Lyman-alpha line of atomic hydrogen . It is normally seen as a bright spectral peak (an "emission line") in the "lighthouse" object. The rest wavelength is 121.6 nm in the far-ultraviolet part of the spectrum. That spectral region is not accessible to ground-based telescopes - UV-light does not pass through the Earth's atmosphere. However, in very distant objects, the Lyman-alpha line is redshifted towards longer wavelengths and becomes observable from the ground [2]. On its way to us, the light beam from a bright and distant object traverses a long path , mostly through (nearly) empty space. However, once in a while, it passes through a cloud of matter, for instance in the outskirts of a remote galaxy. Each time, specific signatures from the atoms and molecules in that cloud are imprinted on the passing light in the form of spectral absorption lines at particular wavelengths. Such clouds contain hydrogen and thus produce a specific Lyman-alpha signature in the spectrum of the "lighthouse" object [3] Because of the different distances of the individual clouds, their Lyman-alpha spectral lines have different "redshifts" and are therefore observed at different wavelengths. In practice, the Lyman-alpha absorption lines from the intervening clouds are located on the blueward side (i.e., at shorter wavelengths because of their smaller redshifts) of the main emission peak, giving rise to the concept of a "Lyman-alpha forest" of spectral absorption lines. In some cases, over one thousand absorption lines have been seen, showing the presence of as many individual hydrogen-rich gas clouds along the line-of-sight towards the background "lighthouse", cf. ESO PR 15/99 and ESO PR 08/00. MS 1512-cB58 : a bright and remote galaxy MS 1512-cB58 is a remote, very bright galaxy, located at a distance of approximately 12 billion light-years in the northern constellation of Boötes. Its light has travelled 12 billion years to reach us and we therefore observe it as it was when the Universe was about 3 billion years old. Because of the extremely large distance, this galaxy would normally only be seen as a very faint object in the sky, so faint indeed that it could not be observed in any detail by existing telescopes. However, we are lucky, thanks to the fortuitious effect of gravitational lensing . About halfway on its way to us, the light from MS 1512-cB58 happens to pass through the strong gravitational field of a cluster of galaxies known as MS 1512+36 and this produces an amazingly efficient focussing effect: the light from MS 1512-cB58 that finally reaches us has been amplified no less than some 50 times! This beneficial effect makes all the difference. At the observed magnitude of 20.6 - though still nearly 1 million times fainter than what can be perceived with the unaided eye - MS 1512-cB58 is the best suited remote object of its type for the above mentioned kind of investigation. Thus, a detailed study of its spectrum, in particular the spectral region on the shortward side of the Lyman-alpha line (seen in absorption in this comparatively "normal" galaxy), provides very useful information about the many clouds of hydrogen that are located along the line-of-sight towards this object. The UVES spectrum ESO PR Photo 08b/02 ESO PR Photo 08b/02 [Preview - JPEG: 512 x 400 pix - 184k] [Normal - JPEG: 1023 x 800 pix - 448k] ESO PR Photo 08c/02 ESO PR Photo 08c/02 [Preview - JPEG: 750 x 400 pix - 136k] [Normal - JPEG: 1500 x 800 pix - 288k] Caption : PR Photo 08b/02 shows a section of the UVES spectrum of the very distant, 20.6-mag galaxy MS 1512-cB58 , obtained with the UVES high-dispersion spectrograph at the VLT KUEYEN telescope. The Lyman-alpha absorption line from the galaxy itself is seen as the broad depression at about 4530 Å (453 nm; lower panel). The absorption lines at shorter wavelengths are the signatures of individual intergalactic clouds along the line-of-sight; they are indicated by red vertical lines. Blue arrows point at absorption lines associated with heavy elements present in the gas inside the MS 1512-cB58 galaxy. PR Photo 08c/02 is an enlargement of a small wavelength region that shows the full resolution and extreme wealth of information contained in the spectrum of this faint object. Also here, Lyman-alpha absorption lines arising in intervening intergalactic clouds are indicated by red vertical lines. Technical information about the photos is available below. Using one of the most efficient astronomical spectrographs available, the Ultraviolet-Visual Echelle Spectrograph (UVES) at the ESO Very Large Telescope (VLT) at the Paranal Observatory , an international group of astronomers [1] succeeded in obtaining a very detailed (high-dispersion) spectrum of MS 1512-cB58 . Despite the fact that this object is located some 36° north of the celestial equator and can therefore only be observed for about 90 min each night from Paranal (at geographical latitude 25° south), the superposition of several exposures obtained between March and August 2000 has produced the most detailed and informative spectrum ever obtained of a distant galaxy, cf. PR Photos 08b-c/02 . At the same time, it provides a very comprehensive map of the Universe to such a large distance along a line-of-sight , as this can be read from the numerous Lyman-alpha absorption lines from intervening clouds, seen in this spectrum. The surroundings of MS 1512-cB58 The astronomers were particularly interested in the distribution of clouds in the region of space near MS 1512-cB58 . Thanks to the excellent quality of the UVES data, it was possible to identify and measure a substantial number of Lyman-alpha lines blueward of the broad Lyman-alpha absorption line from the galaxy itself, present in the lower panel of PR Photo 08b/01 . They correspond to intergalactic hydrogen clouds comparatively near the "lighthouse" object MS 1512-cB58 . Most interestingly, it turned out that there are exceptionally many such clouds rather near this remote galaxy (the corresponding absorption lines are seen in the middle panel of PR Photo 08b/01 of which a small part has been enlarged for clarity in PR Photo 08c/01 . Comparing with the mean density along the line-of-sight, a surplus of about 200% was evident. An effect of this dimension has never been seen before near such a remote object, i.e., at such an early epoch, only 3 billion years after the Big Bang. A young supercluster? What does this tell us? The astronomers have two explanations: either we are seeing a very large cluster of clouds (proto-galaxies) at some distance from MS 1512-cB58 , or the clouds are in some way directly connected to the environment of that galaxy. A rich distribution of gas clouds is indeed expected around star-forming galaxies like MS 1512-cB58 at this early epoch. For various reasons, however, including the actual distribution of the observed clouds, the astronomers do not favour the second hypothesis. It appears more likely that these clouds are separate objects not related to MS 1512-cB58 . In that case, this would imply the presence of large-scale structure at this early time , only 3 billion years after the Big Bang. MS 1512-cB58 might then be the largest (heaviest) single object in the neigbourhood, a likely progenitor of the local massive galaxies observed at the present time. More information The results described in this Press Release are presented in a research paper "The Lyman-alpha forest of a Lyman-Break Galaxy: VLT Spectra of MS 1512-cB58 at z = 2.724" by Sandra Savaglio, Nino Panagia and Paolo Padovani, appearing in the research journal "Astrophysical Journal" this month. Notes [1]: The team consists of Sandra Savaglio (Johns Hopkins University, Baltimore, MD, USA, and Rome Observatory, Italy), Nino Panagia and Paolo Padovani (both European Space Agency and Space Telescope Science Institute, Baltimore) [2]: The measured redshift of MS 1512-cB58 is z = 2.724. In astronomy, the redshift denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a distant cloud or galaxy gives a direct estimate of the apparent recession velocity as caused by the universal expansion. Since the expansion rate increases with distance, the velocity is itself a function (the Hubble relation) of the distance to the object. The distances indicated in the text are based on an age of the Universe of 15 billion years. At the indicated redshift, the Lyman-alpha line of atomic hydrogen (rest wavelength 121.6 nm) is observed at 452.8 nm, i.e. in the blue spectral region. The Lyman-alpha absorption lines from intergalactic clouds along the line-of-sight (and at lower redshifts) are observed at shorter wavelengths. The lower limit of the UVES spectrum of MS 1512-cB58 (415 nm) corresponds to a Lyman-alpha redshift of 2.41, i.e. a distance of about 7.5 billion light-years. [3]: The importance of the Lyman-alpha line in absorption is that it is exquisitely sensitive to the presence of neutral hydrogen which only constitutes a small fraction of the total amount of hydrogen in the intergalactic medium (about 1/10,000). Still, the observed Ly-alpha forest is extremely rich. What we see is most likely the "tip of the iceberg" only and hydrogen in the intergalactic medium at high redshift is probably the dominant component of baryonic matter in the early Universe. Contact Sandra Savaglio Johns Hopkins University Baltimore, MD, USA Tel.: +1 410 516 8583 email: savaglio@pha.jhu.edu Technical information about the photos PR Photo 08a/02 is a reproduction of a composite image of the field around the distant cluster of galaxies MS 1512+36 (redshift 0.37), obtained with the WFPC2 camera at the NASA/ESA Hubble Space Telescope. It is based on exposures in two filters (F555 + F675). The observations are described in a research paper by Seitz et al. (Monthly Notices of the RAS, August 1998, Vol. 298, p. 945 ff). The lensed image of the galaxy MS 1512-cB58 is seen at an angular distance of about 5 arcsec from the centre of the cluster. The north direction is at about 1 o'clock and east is at 10 o'clock. The field measures approx. 45 x 60 arcsec 2. PR Photo 08b/02 shows the composite spectrum of MS 1512-cB58 in the spectral region of interest (415.0 - 459.5 nm), as obtained with the red and blue arms of UVES. Long and short red vertical lines ("ticks") indicate larger and smaller intergalactic hydrogen clouds, respectively. The overlying, continuous red line is the "best-fit" model to the observed spectrum. Due to the low altitude of the object, the exposures never lasted more than 90 min around the northern meridian. The full spectral coverage is 415 - 500 nm (blue arm) and 524 - 621 nm (red arm). The velocity resolution varies from 29 km/s at the blue end to 19 km/sec at the red limit. The S/N-ratio increases from about 3 (415 nm) to 10 (610 nm). PR Photo 08c/02 reproduces a smaller part of the observed spectral region observed at full resolution (434.8 - 443.0 nm), with two dozen detected clouds indicated.

The Spatial Distribution and Kinematics of the Circumgalactic Medium

NASA Astrophysics Data System (ADS)

Churchill, Christopher W.; Nielsen, Nikole M.; Kacprzak, Glenn; Charlton, Jane C.; Muzahid, Sowgat

2017-01-01

We have examined the spatial distribution and kinematics of the circumgalactic medium (CGM) within 200 kpc of galaxies in the redshift range 0.1 to 1.0. The galaxies are resolved in HST images and are selected to have background quasars with sightlines that probe their CGM. We measured the cool/warm CGM in MgII absorption and the warm/hot CGM in OVI absorption using Keck/HIRES, VLT/UVES, and HST/COS. We have found that the CGM gas is highly organized such that: (1) gas is concentrated along the galaxy polar axes with high velocity dispersion, and (2) gas is concentrated along the galaxy major axes with smaller velocity dispersion. We constrain the geometry of the gas to reside between 20-40 degrees of the projected major axis and within 60 degrees of the projected minor axis, with little-to-no gas found in between. Furthermore, strongest absorption and largest velocity spreads are found for highly inclined (face on) galaxies with the bluest colors, suggesting outflows along the minor axes of star-forming galaxies. The major axis of bluer galaxies have similar velocity spreads to those of the gas surrouncding redder galaxies, which show little spatial preference in the distribution of the gas dynamics. Our results are consistent with the current view of the CGM originating from major axis (co-planer) inflows/recycled gas and from minor axis wind-driven outflows. We address how our results place strong contraints on the baryon cycle.

SWEET-Cat update and FASMA. A new minimization procedure for stellar parameters using high-quality spectra

NASA Astrophysics Data System (ADS)

Andreasen, D. T.; Sousa, S. G.; Tsantaki, M.; Teixeira, G. D. C.; Mortier, A.; Santos, N. C.; Suárez-Andrés, L.; Delgado-Mena, E.; Ferreira, A. C. S.

2017-04-01

Context. Thanks to the importance that the star-planet relation has to our understanding of the planet formation process, the precise determination of stellar parameters for the ever increasing number of discovered extrasolar planets is of great relevance. Furthermore, precise stellar parameters are needed to fully characterize the planet properties. It is thus important to continue the efforts to determine, in the most uniform way possible, the parameters for stars with planets as new discoveries are announced. Aims: In this paper we present new precise atmospheric parameters for a sample of 50 stars with planets. The results are presented in the catalogue: SWEET-Cat. Methods: Stellar atmospheric parameters and masses for the 50 stars were derived assuming local thermodynamic equilibrium and using high-resolution and high signal-to-noise spectra. The methodology used is based on the measurement of equivalent widths with ARES2 for a list of iron lines. The line abundances were derived using MOOG. We then used the curve of growth analysis to determine the parameters. We implemented a new minimization procedure which significantly improves the computational time. Results: The stellar parameters for the 50 stars are presented and compared with previously determined literature values. For SWEET-Cat, we compile values for the effective temperature, surface gravity, metallicity, and stellar mass for almost all the planet host stars listed in the Extrasolar Planets Encyclopaedia. This data will be updated on a continuous basis. The data can be used for statistical studies of the star-planet correlation, and for the derivation of consistent properties for known planets. Based on observations collected at the La Silla Observatory, ESO (Chile), with FEROS/2.2 m (run 2014B/020), with UVES/VLT at the Cerro Paranal Observatory (runs ID 092.C-0695, 093.C-0219, 094.C-0367, 095.C-0324, and 096.C-0092), and with FIES/NOT at Roque de los Muchachos (Spain; runs ID 14AF14 and 53-202).The compiled SWEET-Cat is available online, http://https://www.astro.up.pt/resources/sweet-cat/

VizieR Online Data Catalog: FGK dwarfs atmospheric parameters (Ryabchikova+, 2016)

NASA Astrophysics Data System (ADS)

Ryabchikova, T.; Piskunov, N.; Pakhomov, Y.; Tsymbal, V.; Titarenko, A.; Sitnova, T.; Alexeeva, S.; Fossati, L.; Mashonkina, L.

2016-08-01

For the spectroscopic analysis, we choose the 13 MS stars including the Sun (Table 1) in the 4900-6600K temperature range and with metallicity between [Fe/H]=-1.5 and +0.3dex. All the stars, except HD 149026, have, at least, one interferometric determination of radius and effective temperature. Spectra of the programme stars were obtained with different spectrographs. Most data were extracted from the following archives: the UVES/VLT and HARPS/3.6m spectrographs at ESO,2 the ELODIE/1.93-m spectrograph3 at the Observatoire de Haute Provence, and the ESPaDONs spectrograph at the Canada-France-Hawaii Telescope (CFHT). Spectra of beta Vir and HD 103095 were obtained with the FOCES spectrograph at 2.2-m telescope of the Calar Alto Observatory. One of the spectra of 61 Vir was obtained with the Hamilton Echelle Spectrograph attached to the Shane 3-m telescope of the Lick Observatory. Spectra of few stars, including that of the Sun reflected from Ganymede, were obtained with the HiReS/Keck spectrograph. (3 data files).

CARMENES. Mining public archives for stellar parameters and spectra of M dwarfs with master thesis students

NASA Astrophysics Data System (ADS)

Caballero, J. A.; Montes, D.; Alonso-Floriano, F. J.; Cortés-Contreras, M.; González-Álvarez, E.; Hidalgo, D.; Holgado, G.; Martínez-Rodríguez, H.; Sanz-Forcada, J.; López-Santiago, J.

2015-05-01

We are compiling the most comprehensive database of M dwarfs ever built, CARMENCITA, the CARMENES Cool dwarf Information and daTa Archive, which will be the CARMENES 'input catalogue'. In addition to the science preparation with low- and high-resolution spectrographs and lucky imagers, we compile a huge pile of public data on over 2200 M dwarfs, and analyse them, mostly using virtual-observatory tools. Here we describe four specific actions carried out by master students. They mine public archives for additional high-resolution spectroscopy (UVES, FEROS and HARPS), multi-band photometry (FUV-NUV-u-B-g-V-r-R-i-J-H-Ks-W1-W2-W3-W4), X-ray data (ROSAT, XMM-Newton and Chandra), and periods, rotational velocities and Hα pseudo-equivalent widths. As described, there are many interdependences between all these data.

Spectroscopy and Photometry of Multiple Populations along the Asymptotic Giant Branch of NGC 2808 and NGC 6121 (M4)

NASA Astrophysics Data System (ADS)

Marino, A. F.; Milone, A. P.; Yong, D.; Da Costa, G.; Asplund, M.; Bedin, L. R.; Jerjen, H.; Nardiello, D.; Piotto, G.; Renzini, A.; Shetrone, M.

2017-07-01

We present a photometric and spectroscopic study of multiple populations along the asymptotic giant branch (AGB) of the intermediate-metallicity globular clusters (GCs) NGC 2808 and NGC 6121 (M4). Chemical abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Co, Ni, Zn, Y, and Ce in AGB stars from high-resolution FLAMES+UVES@VLT spectra are reported for both clusters. Our spectroscopic results have been combined with multiwavelength photometry from the Hubble Space Telescope UV survey of Galactic GCs and ground-based photometry, as well as proper motions derived by combining stellar positions from ground-based images and Gaia DR1. Our analysis reveals that the AGBs of both clusters host multiple populations with different chemical compositions. In M4, we have identified two main populations of stars with different Na/O content lying on distinct AGBs in the {m}{{F}438{{W}}} versus {C}{{F}275{{W}},{{F}}336{{W}},{{F}}438{{W}}} and the V versus {C}{{U},{{B}},{{I}}} pseudo-color-magnitude diagrams. In the more massive and complex GC NGC 2808, three groups of stars with different chemical abundances occupy different locations on the so-called “chromosome map” photometric diagram constructed for AGB stars. The spectroscopic + photometric comparison of stellar populations along the AGB and the red giants of this GC suggests that the AGB hosts stellar populations with a range in helium abundances from primordial to high contents of Y˜ 0.32. By contrast, from our data set, there is no evidence for stars with extreme helium abundance (Y˜ 0.38) on the AGB, suggesting that the most He-rich stars of NGC 2808 do not reach this phase. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programs 093.D-0789 and 094.D-0455 and on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS 5-26555.

Stellar abundances and ages for metal-rich Milky Way globular clusters. Stellar parameters and elemental abundances for 9 HB stars in NGC 6352

NASA Astrophysics Data System (ADS)

Feltzing, S.; Primas, F.; Johnson, R. A.

2009-01-01

Context: Metal-rich globular clusters provide important tracers of the formation of our Galaxy. Moreover, and not less important, they are very important calibrators for the derivation of properties of extra-galactic metal-rich stellar populations. Nonetheless, only a few of the metal-rich globular clusters in the Milky Way have been studied using high-resolution stellar spectra to derive elemental abundances. Additionally, Rosenberg et al. identified a small group of metal-rich globular clusters that appeared to be about 2 billion years younger than the bulk of the Milky Way globular clusters. However, it is unclear if like is compared with like in this dataset as we do not know the enhancement of α-elements in the clusters and the amount of α-elements is well known to influence the derivation of ages for globular clusters. Aims: We derive elemental abundances for the metal-rich globular cluster NGC 6352 and we present our methods to be used in up-coming studies of other metal-rich globular clusters. Methods: We present a study of elemental abundances for α- and iron-peak elements for nine HB stars in the metal-rich globular cluster NGC 6352. The elemental abundances are based on high-resolution, high signal-to-noise spectra obtained with the UVES spectrograph on VLT. The elemental abundances have been derived using standard LTE calculations and stellar parameters have been derived from the spectra themselves by requiring ionizational as well as excitational equilibrium. Results: We find that NGC 6352 has [Fe/H] = -0.55, is enhanced in the α-elements to about +0.2 dex for Ca, Si, and Ti relative to Fe. For the iron-peak elements we find solar values. Based on the spectroscopically derived stellar parameters we find that an E(B-V) = 0.24 and (m-M) ≃ 14.05 better fits the data than the nominal values. An investigation of log gf-values for suitable Fe i lines lead us to the conclusion that the commonly used correction to the May et al. (1974) data should not be employed. Full Table [see full text] are also only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/493/913 Based on observations collected at the European Southern Observatory, Chile, ESO No. 69.B-0467.

What is the Milky Way outer halo made of?. High resolution spectroscopy of distant red giants

NASA Astrophysics Data System (ADS)

Battaglia, G.; North, P.; Jablonka, P.; Shetrone, M.; Minniti, D.; Díaz, M.; Starkenburg, E.; Savoy, M.

2017-12-01

In a framework where galaxies form hierarchically, extended stellar haloes are predicted to be an ubiquitous feature around Milky Way-like galaxies and to consist mainly of the shredded stellar component of smaller galactic systems. The type of accreted stellar systems are expected to vary according to the specific accretion and merging history of a given galaxy, and so is the fraction of stars formed in situ versus accreted. Analysis of the chemical properties of Milky Way halo stars out to large Galactocentric radii can provide important insights into the properties of the environment in which the stars that contributed to the build-up of different regions of the Milky Way stellar halo formed. In this work we focus on the outer regions of the Milky Way stellar halo, by determining chemical abundances of halo stars with large present-day Galactocentric distances, >15 kpc. The data-set we acquired consists of high resolution HET/HRS, Magellan/MIKE and VLT/UVES spectra for 28 red giant branch stars covering a wide metallicity range, -3.1 ≲ [Fe/H] ≲-0.6. We show that the ratio of α-elements over Fe as a function of [Fe/H] for our sample of outer halo stars is not dissimilar from the pattern shown by MW halo stars from solar neighborhood samples. On the other hand, significant differences appear at [Fe/H] ≳-1.5 when considering chemical abundance ratios such as [Ba/Fe], [Na/Fe], [Ni/Fe], [Eu/Fe], [Ba/Y]. Qualitatively, this type of chemical abundance trends are observed in massive dwarf galaxies, such as Sagittarius and the Large Magellanic Cloud. This appears to suggest a larger contribution in the outer halo of stars formed in an environment with high initial star formation rate and already polluted by asymptotic giant branch stars with respect to inner halo samples. Based on ESO program 093.B-0615(A).Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.This paper presents data gathered with the Magellan Telescopes at Las Campanas Observatory, Chile.Tables A.5-A.11 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/608/A145

Binary Studies with the Navy Precision Optical Interferometer

DTIC Science & Technology

2013-01-01

the O9.7 supergiant primary. Meanwhile, another high-precision measurement was taken with the UVES 128 Cent. Eur.Astrophys. Bull. 37 (2013) 1, 127–135...spectrometers used for the measurements are labeled as follows: UVES (diamond), HEROS/FEROS (triangle down), ELODIE (squares), FOCES (circle), BESO (triangles up...collaborators report spectro - Cent. Eur.Astrophys. Bull. 37 (2013) 1, 127–135 131 C.A. HUMMEL, R.T. ZAVALA AND J. SANBORN Figure 4: Orbit of ξ Tauri. Figure 5

High-Resolution Infrared Imaging and Polarimetry plus Spectroscopy of Evolved Red and Yellow Supergiants

NASA Astrophysics Data System (ADS)

Gordon, Michael Scott; Humphreys, Roberta; Jones, Terry J.; Gehrz, Robert D.

2018-01-01

To what extent mass loss and periods of enhanced stellar outflow can influence the terminal state of the most massive stars remains an outstanding question in the fields of stellar physics, chemical enrichment of the Local Universe, andsupernova research. For my dissertation, I focus on characterizing the stellar ejecta around supergiants through a combination of observing techniques. Using the LBT, MMT, IRTF, VLT, and SOFIA observatories, I have performed high-resolution imaging, spectroscopy, and polarimetry—methods that provide us with keen insight on mass-loss histories and 3D morphology of the Local Group's most fascinating stars.Based on spectroscopic evidence for mass loss in the optical and the presence ofcircumstellar (CS) dust in infrared SEDs, we find that 30%–40% of observed yellow supergiants in M31 and M33 are likely in a post-RSG state. We also presentnear-IR spectra from IRTF/SPeX of optically-obscured RSGs in M33. These IR-bright sources likely have some of the highest mass-loss rates and are self-obscured in the optical by their own CS ejecta. For Galactic red supergiants (RSGs), we are able to observe the gas and CS dust ejecta both close in to the central star and at larger distances. The resulting radial profiles are valuable probes on timescale for the ejecta when combined with radiative-transfer models. We find evidence for both variable/high mass-loss events and constant mass loss over the last few thousand years. Finally, we discuss the use of high-resolution imaging polarimetry with VLT/NACO of two co-eval RSG clusters toward the Galactic center. The resulting polarized intensity images in the near-infrared provide unprecedented spatial and contrast resolution of the scattered light from extended nebular material.

Circling Around the Uncanny Valley: Design Principles for Research Into the Relation Between Human Likeness and Eeriness

PubMed Central

Brace, Nicola; Pike, Graham; Pollick, Frank

2016-01-01

The uncanny valley effect (UVE) is a negative emotional response experienced when encountering entities that appear almost human. Research on the UVE typically investigates individual, or collections of, near human entities but may be prone to methodological circularity unless the properties that give rise to the emotional response are appropriately defined and quantified. In addition, many studies do not sufficiently control the variation in human likeness portrayed in stimulus images, meaning that the nature of stimuli that elicit the UVE is also not well defined or quantified. This article describes design criteria for UVE research to overcome the above problems by measuring three variables (human likeness, eeriness, and emotional response) and by using stimuli spanning the artificial to human continuum. These criteria allow results to be plotted and compared with the hypothesized uncanny valley curve and any effect observed can be quantified. The above criteria were applied to the methods used in a subset of existing UVE studies. Although many studies made use of some of the necessary measurements and controls, few used them all. The UVE is discussed in relation to this result and research methodology more broadly. PMID:27994844

The Hamburg/ESO R-process Enhanced Star survey (HERES). XI. The highly r-process-enhanced star CS 29497-004

NASA Astrophysics Data System (ADS)

Hill, V.; Christlieb, N.; Beers, T. C.; Barklem, P. S.; Kratz, K.-L.; Nordström, B.; Pfeiffer, B.; Farouqi, K.

2017-11-01

We report an abundance analysis for the highly r-process-enhanced (r-II) star CS 29497-004, a very metal-poor giant with solar system Teff = 5013 K and [Fe/H] = -2.85, whose nature was initially discovered in the course of the HERES project. Our analysis is based on high signal-to-noise ratio, high-resolution (R 75 000) VLT/UVES spectra and MARCS model atmospheres under the assumption of local thermodynamic equilibrium, and obtains abundance measurements for a total of 46 elements, 31 of which are neutron-capture elements. As is the case for the other 25 r-II stars currently known, the heavy-element abundance pattern of CS 29497-004 well-matches a scaled solar system second peak r-process-element abundance pattern. We confirm our previous detection of Th, and demonstrate that this star does not exhibit an "actinide boost". Uranium is also detected (log ɛ(U) = -2.20 ± 0.30), albeit with a large measurement error that hampers its use as a precision cosmo-chronometer. Combining the various elemental chronometer pairs that are available for this star, we derive a mean age of 12.2 ± 3.7 Gyr using the theoretical production ratios from published waiting-point approximation models. We further explore the high-entropy wind model (Farouqi et al. 2010, ApJ, 712, 1359) production ratios arising from different neutron richness of the ejecta (Ye), and derive an age of 13.7 ± 4.4 Gyr for a best-fitting Ye = 0.447. The U/Th nuclei-chronometer is confirmed to be the most resilient to theoretical production ratios and yields an age of 16.5 ± 6.6 Gyr. Lead (Pb) is also tentatively detected in CS 29497-004, at a level compatible with a scaled solar r-process, or with the theoretical expectations for a pure r-process in this star. Based on observations collected at the European Southern Observatory, Paranal, Chile (Proposal Number 170.D-0010).Table B.1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/607/A91

VLT FORS2 comparative transmission spectral survey of clear and cloudy exoplanet atmospheres

NASA Astrophysics Data System (ADS)

Nikolov, Nikolay; Sing, David; Gibson, Neale; Evans, Thomas; Barstow, Joanna Katy; Kataria, Tiffany; Wilson, Paul A.

2016-10-01

Transmission spectroscopy is a key to unlocking the secrets of close-in exoplanet atmospheres. Observations have started to unveil a vast diversity of irradiated giant planet atmospheres with clouds and hazes playing a definitive role across the entire mass and temperature regime. We have initiated a ground-based, multi-object transmission spectroscopy of a hand full of hot Jupiters, covering the wavelength range 360-850nm using the recently upgraded FOcal Reducer and Spectrograph (FORS2) mounted on the Very Large Telescope (VLT) at the European Southern Observatory (ESO). These targets were selected for comparative follow-up as their transmission spectra showed evidence for alkali metal absorption, based on the results of Hubble Space Telescope (HST) observations. This talk will discuss the first results from the programme, demonstrating excellent agreement between the transmission spectra measured from VLT and HST and further reinforce the findings of clear, cloudy and hazy atmospheres. More details will be discussed on the narrow alkali features obtained with FORS2 at higher resolution, revealing its high potential in securing optical transmission spectra. These FORS2 observations are the first ground-based detections of clear, cloudy and hazy hot-Jupiter atmosphere with a simultaneous detections of Na, K, and H2 Rayleigh scattering. Our program demonstrates the large potential of the instrument for optical transmission spectroscopy, capable of obtaining HST-quality light curves from the ground. Compared to HST, the larger aperture of VLT will allow for fainter targets to be observed and higher spectral resolution, which can greatly aid comparative exoplanet studies. This is important for further exploring the diversity of exoplanet atmospheres and is particularly complementary to the near- and mid-IR regime, to be covered by the upcoming James-Webb Space Telescope (JWST) and is readily applicable to less massive planets down to super-Earths.

The 2004 Opposition of Ceres Observed with Adaptive Optics on the VLT

NASA Technical Reports Server (NTRS)

Erard, S.; Frorni, O.; Ollivier, M.; Dotto, E.; Roush, T.; Poulet, F.; Mueller, T.

2005-01-01

The close opposition of Ceres in January 2004 has been observed with the NACO adaptive optics system on the VLT. Both imaging and spectroscopy were performed in the 1.1-4.1 m range. Extensive longitudinal coverage was acquired during a three days run, with spatial resolution up to 50 km in imaging mode. The scientific objectives are 1) to provide the first IR map of Ceres; 2) to map possible compositional variations at the surface. Only imaging results are presented here.

[Analyzing and modeling methods of near infrared spectroscopy for in-situ prediction of oil yield from oil shale].

PubMed

Liu, Jie; Zhang, Fu-Dong; Teng, Fei; Li, Jun; Wang, Zhi-Hong

2014-10-01

In order to in-situ detect the oil yield of oil shale, based on portable near infrared spectroscopy analytical technology, with 66 rock core samples from No. 2 well drilling of Fuyu oil shale base in Jilin, the modeling and analyzing methods for in-situ detection were researched. By the developed portable spectrometer, 3 data formats (reflectance, absorbance and K-M function) spectra were acquired. With 4 different modeling data optimization methods: principal component-mahalanobis distance (PCA-MD) for eliminating abnormal samples, uninformative variables elimination (UVE) for wavelength selection and their combina- tions: PCA-MD + UVE and UVE + PCA-MD, 2 modeling methods: partial least square (PLS) and back propagation artificial neural network (BPANN), and the same data pre-processing, the modeling and analyzing experiment were performed to determine the optimum analysis model and method. The results show that the data format, modeling data optimization method and modeling method all affect the analysis precision of model. Results show that whether or not using the optimization method, reflectance or K-M function is the proper spectrum format of the modeling database for two modeling methods. Using two different modeling methods and four different data optimization methods, the model precisions of the same modeling database are different. For PLS modeling method, the PCA-MD and UVE + PCA-MD data optimization methods can improve the modeling precision of database using K-M function spectrum data format. For BPANN modeling method, UVE, UVE + PCA-MD and PCA- MD + UVE data optimization methods can improve the modeling precision of database using any of the 3 spectrum data formats. In addition to using the reflectance spectra and PCA-MD data optimization method, modeling precision by BPANN method is better than that by PLS method. And modeling with reflectance spectra, UVE optimization method and BPANN modeling method, the model gets the highest analysis precision, its correlation coefficient (Rp) is 0.92, and its standard error of prediction (SEP) is 0.69%.

Exoplanetary System HD 189733 - Chromosphere, Transit, Activity

NASA Astrophysics Data System (ADS)

Krejcova, T.; Czesla, S.; Wolter, U.; Schmitt, J. H. M. M.

2015-01-01

We present a study of the temporal evolution of the chromospherically sensitive lines in the transiting exoplanetary system HD 189733 using high-resolution UVES spectra. With its fast temporal cadence of only 45 s and its wide spectral coverage, our time series is ideal to study the influence of the transiting planetary disk on chromospheric lines . We measured the equivalent width and central line depression of the Ca II H and K lines, Hα, and the Ca II infrared triplet. While all these lines show temporal evolution on a scale potentially induced by the occulting planetary disk, strong intrinsic stellar variability prevents us from uniquely ascribing the observed variation to the planetary transit.

Preparation of the CARMENES Input Catalogue: Mining Public Archives for Stellar Parameters and Spectra of M Dwarfs with Master Thesis Students

NASA Astrophysics Data System (ADS)

Montes, D.; Caballero, J. A.; Alonso-Floriano, F. J.; Cortes Contreras, M.; Gonzalez-Alvarez, E.; Hidalgo, D.; Holgado, G.; Llamas, M.; Martinez-Rodriguez, H.; Sanz-Forcada, J.

2015-01-01

We help compiling the most comprehensive database of M dwarfs ever built, CARMENCITA, the CARMENES Cool dwarf Information and daTa Archive, which will be the CARMENES `input catalogue'. In addition to the science preparation with low- and high-resolution spectrographs and lucky imagers (see the other contributions in this volume), we compile a huge pile of public data on over 2100 M dwarfs, and analyze them, mostly using virtual-observatory tools. Here we describe four specific actions carried out by master and grade students. They mine public archives for additional high-resolution spectroscopy (UVES, FEROS and HARPS), multi-band photometry (FUV-NUV-u-B-g-V-r-R-i-J-H-Ks-W1-W2-W3-W4), X-ray data (ROSAT, XMM-Newton and Chandra), periods, rotational velocities and Hα pseudo-equivalent widths. As described, there are many interdependences between all these data.

Some (Little) Thing(s) about VISIR

NASA Astrophysics Data System (ADS)

Pantin, E.; Vanzi, L.; Weilenmann, U.

VISIR is the VLT mid-infrared Imager and Spectrometer. It offers a comprehensive set of observing modes, imaging in N and Q bands, at the limits of the telescope diffraction, as well as spectroscopy in the same bands. In particular, VISIR provides a very high-resolution spectroscopy mode with an achieved resolution up to 30000 in N band; this mode is so far unique in the southern hemisphere. VISIR calibration is quite specific when compared to standard visible/near-infrared ones. Various dedicated methods have to be developed to remove the instrumental signatures and obtain the best scientific return.

The AMBRE Project: Stellar parameterisation of the ESO:UVES archived spectra

NASA Astrophysics Data System (ADS)

Worley, C. C.; de Laverny, P.; Recio-Blanco, A.; Hill, V.; Bijaoui, A.

2016-06-01

Context. The AMBRE Project is a collaboration between the European Southern Observatory (ESO) and the Observatoire de la Côte d'Azur (OCA) that has been established to determine the stellar atmospheric parameters for the archived spectra of four ESO spectrographs. Aims: The analysis of the UVES archived spectra for their stellar parameters was completed in the third phase of the AMBRE Project. From the complete ESO:UVES archive dataset that was received covering the period 2000 to 2010, 51 921 spectra for the six standard setups were analysed. These correspond to approximately 8014 distinct targets (that comprise stellar and non-stellar objects) by radial coordinate search. Methods: The AMBRE analysis pipeline integrates spectral normalisation, cleaning and radial velocity correction procedures in order that the UVES spectra can then be analysed automatically with the stellar parameterisation algorithm MATISSE to obtain the stellar atmospheric parameters. The synthetic grid against which the MATISSE analysis is carried out is currently constrained to parameters of FGKM stars only. Results: Stellar atmospheric parameters are reported for 12 403 of the 51 921 UVES archived spectra analysed in AMBRE:UVES. This equates to ~23.9% of the sample and ~3708 stars. Effective temperature, surface gravity, metallicity, and alpha element to iron ratio abundances are provided for 10 212 spectra (~19.7%), while effective temperature at least is provided for the remaining 2191 spectra. Radial velocities are reported for 36 881 (~71.0%) of the analysed archive spectra. While parameters were determined for 32 306 (62.2%) spectra these parameters were not considered reliable (and thus not reported to ESO) for reasons such as very low S/N, too poor radial velocity determination, spectral features too broad for analysis, and technical issues from the reduction. Similarly the parameters of a further 7212 spectra (13.9%) were also not reported to ESO based on quality criteria and error analysis which were determined within the automated parameterisation process. Those tests lead us to expect that multi-component stellar systems will return high errors in radial velocity and fitting to the synthetic spectra and therefore will not have parameters reported to ESO. Typical external errors of σTeff ~ 110 dex, σlog g ~ 0.18 dex, σ[ M/H ] ~ 0.13 dex, and σ[ α/ Fe ] ~ 0.05 dex with some variation between giants and dwarfs and between setups are reported. Conclusions: UVES is used to observe an extensive collection of stellar and non-stellar objects all of which have been included in the archived dataset provided to OCA by ESO. The AMBRE analysis extracts those objects that lie within the FGKM parameter space of the AMBRE slow-rotating synthetic spectra grid. Thus by homogeneous blind analysis AMBRE has successfully extracted and parameterised the targeted FGK stars (23.9% of the analysed sample) from within the ESO:UVES archive.

INTRIGOSS: A new Library of High Resolution Synthetic Spectra

NASA Astrophysics Data System (ADS)

Franchini, Mariagrazia; Morossi, Carlo; Di Marcancantonio, Paolo; Chavez, Miguel; GES-Builders

2018-01-01

INTRIGOSS (INaf Trieste Grid Of Synthetic Spectra) is a new High Resolution (HiRes) synthetic spectral library designed for studying F, G, and K stars. The library is based on atmosphere models computed with specified individual element abundances via ATLAS12 code. Normalized SPectra (NSP) and surface Flux SPectra (FSP), in the 4800-5400 Å wavelength range, were computed by means of the SPECTRUM code. The synthetic spectra are computed with an atomic and bi-atomic molecular line list including "bona fide" Predicted Lines (PLs) built by tuning loggf to reproduce very high SNR Solar spectrum and the UVES-U580 spectra of five cool giants extracted from the Gaia-ESO survey (GES). The astrophysical gf-values were then assessed by using more than 2000 stars with homogenous and accurate atmosphere parameters and detailed chemical composition from GES. The validity and greater accuracy of INTRIGOSS NSPs and FSPs with respect to other available spectral libraries is discussed. INTRIGOSS will be available on the web and will be a valuable tool for both stellar atmospheric parameters and stellar population studies.

HIGH PRECISION ABUNDANCES OF THE OLD SOLAR TWIN HIP 102152: INSIGHTS ON Li DEPLETION FROM THE OLDEST SUN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Monroe, TalaWanda R.; Melendez, Jorge; Tucci Maia, Marcelo

2013-09-10

We present the first detailed chemical abundance analysis of the old 8.2 Gyr solar twin, HIP 102152. We derive differential abundances of 21 elements relative to the Sun with precisions as high as 0.004 dex ({approx}<1%), using ultra high-resolution (R = 110,000), high S/N UVES spectra obtained on the 8.2 m Very Large Telescope. Our determined metallicity of HIP 102152 is [Fe/H] = -0.013 {+-} 0.004. The atmospheric parameters of the star were determined to be 54 K cooler than the Sun, 0.09 dex lower in surface gravity, and a microturbulence identical to our derived solar value. Elemental abundance ratiosmore » examined versus dust condensation temperature reveal a solar abundance pattern for this star, in contrast to most solar twins. The abundance pattern of HIP 102152 appears to be the most similar to solar of any known solar twin. Abundances of the younger, 2.9 Gyr solar twin, 18 Sco, were also determined from UVES spectra to serve as a comparison for HIP 102152. The solar chemical pattern of HIP 102152 makes it a potential candidate to host terrestrial planets, which is reinforced by the lack of giant planets in its terrestrial planet region. The following non-local thermodynamic equilibrium Li abundances were obtained for HIP 102152, 18 Sco, and the Sun: log {epsilon} (Li) = 0.48 {+-} 0.07, 1.62 {+-} 0.02, and 1.07 {+-} 0.02, respectively. The Li abundance of HIP 102152 is the lowest reported to date for a solar twin, and allows us to consider an emerging, tightly constrained Li-age trend for solar twin stars.« less

Neutron-capture element abundances in the planetary nebula NGC 5315 from deep high-resolution optical and near-IR spectrophotometry

NASA Astrophysics Data System (ADS)

Madonna, S.; García-Rojas, J.; Sterling, N. C.; Luridiana, V.

2017-03-01

We have done a spectroscopical analysis of the type I planetary nebula (PN) NGC 5315, through high-resolution (R ˜ 40000) optical spectroscopy with UVES at the 8.2m Very Large Telescope, and medium-resolution (R ˜ 4800) near-IR spectroscopy with FIRE at the 6.5m Magellan Baade telescope, covering a wide spectral range from 0.31 μm to 2.50μm. The main aim of this work is to investigate the slow neutron(n)-capture process (the s-process) in the Asymptotic Giant Branch (AGB) star progenitor of a type I PNe. We detected and identified about 700 features, including lines from the n-capture elements Kr, Se, and possibly Br and Xe. We compute physical conditions using line ratios of common ions. Ionic abundances are computed for the species with available atomic data. We calculate total abundances using recent ionization correction factors (ICFs) or by summing ionic abundances. Our results for common elements are in good agreement with previous works on the same object. We do not find a substantial s-process enrichment in NGC 5315, which is typical for type I PNe.

Metallicity determination of M dwarfs. Expanded parameter range in metallicity and effective temperature

NASA Astrophysics Data System (ADS)

Lindgren, Sara; Heiter, Ulrike

2017-08-01

Context. Reliable metallicity values for late K and M dwarfs are important for studies of the chemical evolution of the Galaxy and advancement of planet formation theory in low-mass environments. Historically it has been challenging to determine the stellar parameters of low-mass stars because of their low surface temperature, which causes several molecules to form in the photospheric layers. In our work we use the fact that infrared high-resolution spectrographs have opened up a new window for investigating M dwarfs. This enables us to use similar methods as for warmer solar-like stars. Aims: Metallicity determination with high-resolution spectra is more accurate than with low-resolution spectra, but it is rather time consuming. In this paper we expand our sample analyzed with this precise method both in metallicity and effective temperature to build a calibration sample for a future revised empirical calibration. Methods: Because of the relatively few molecular lines in the J band, continuum rectification is possible for high-resolution spectra, allowing the stellar parameters to be determined with greater accuracy than with optical spectra. We obtained high-resolution spectra with the CRIRES spectrograph at the Very Large Telescope (VLT). The metallicity was determined using synthetic spectral fitting of several atomic species. For M dwarfs that are cooler than 3575 K, the line strengths of FeH lines were used to determine the effective temperatures, while for warmer stars a photometric calibration was used. Results: We analyzed 16 targets with a range of effective temperature from 3350-4550 K. The resulting metallicities lie between -0.5< [M/H] < +0.4. A few targets have previously been analyzed using low-resolution spectra and we find a rather good agreement with our values. A comparison with available photometric calibrations shows varying agreement and the spread within all empirical calibrations is large. Conclusions: Including the targets from our previous paper, we analyzed 28 M dwarfs with high-resolution infrared spectra. The targets spread approximately one dex in metallicity and 1400 K in effective temperature. For individual M dwarfs we achieve uncertainties of 0.05 dex and 100 K on average. Based on data obtained at ESO-VLT, Paranal Observatory, Chile, Program ID 090.D-0796(A).

Direct detection of scattered light gaps in the transitional disk around HD 97048 with VLT/SPHERE

NASA Astrophysics Data System (ADS)

Ginski, C.; Stolker, T.; Pinilla, P.; Dominik, C.; Boccaletti, A.; de Boer, J.; Benisty, M.; Biller, B.; Feldt, M.; Garufi, A.; Keller, C. U.; Kenworthy, M.; Maire, A. L.; Ménard, F.; Mesa, D.; Milli, J.; Min, M.; Pinte, C.; Quanz, S. P.; van Boekel, R.; Bonnefoy, M.; Chauvin, G.; Desidera, S.; Gratton, R.; Girard, J. H. V.; Keppler, M.; Kopytova, T.; Lagrange, A.-M.; Langlois, M.; Rouan, D.; Vigan, A.

2016-11-01

Aims: We studied the well-known circumstellar disk around the Herbig Ae/Be star HD 97048 with high angular resolution to reveal undetected structures in the disk which may be indicative of disk evolutionary processes such as planet formation. Methods: We used the IRDIS near-IR subsystem of the extreme adaptive optics imager SPHERE at the ESO/VLT to study the scattered light from the circumstellar disk via high resolution polarimetry and angular differential imaging. Results: We imaged the disk in unprecedented detail and revealed four ring-like brightness enhancements and corresponding gaps in the scattered light from the disk surface with radii between 39 au and 341 au. We derived the inclination and position angle as well as the height of the scattering surface of the disk from our observational data. We found that the surface height profile can be described by a single power law up to a separation 270 au. Using the surface height profile we measured the scattering phase function of the disk and found that it is consistent with theoretical models of compact dust aggregates. We discuss the origin of the detected features and find that low mass (≤1 MJup) nascent planets are a possible explanation. Based on data collected at the European Southern Observatory, Chile (ESO Programs 096.C-0248, 096.C-0241, 077.C-0106).

Thermal Evolution and Composition of the July 2009 Jupiter Impact Site from 7-25 Micron Imaging and Spectroscopy

NASA Astrophysics Data System (ADS)

Fletcher, L. N.; Orton, G. S.; Mousis, O.; de Pater, I.; Hammel, H. B.; Golisch, W.; Edwards, M.; Yanamandra-Fisher, P. A.; Fisher, B.; Greene, Z.; Lai, S.; Otto, E.; Reshetnikov, N.; Sanchez-Lavega, A.; Simon-Miller, A. A.; Hueso, R.; Perez-Hoyos, S.

2009-12-01

We present analysis of thermal-infrared imaging and spectroscopy of the impact site near the south polar region of Jupiter (see Orton et al., AGU 2009). Enhanced thermal emission was first detected on July 20 2009 in 7-25 micron imaging from the MIRSI instrument on NASA’s IRTF. These observations, just two rotations after the impact, indicated the localised, high-temperature thermal signature of the ejecta field, coincident with the location of high-altitude particulate debris observed in the near-IR and visible. The impact feature was most visible in the 9-11 micron range, suggestive of enhanced emission from hydrocarbons and ammonia gas in the lower stratosphere. Subsequent thermal imaging of the impact region reveals the radiative cooling of the impact site and the changing morphology due to the redistribution of material by Jupiter’s zonal and meridional wind field. We acquired Gemini-N/Michelle imaging on July 22, Gemini-S/TReCS imaging on July 24 and August 5 and 9, and an extensive campaign of VLT/VISIR imaging on July 24, 26 and August 5, 10, 15, 16, at which point (4 weeks after the impact) the thermal signature could no longer be reliably distinguished, even with sub-arcsecond diffraction-limited angular resolution. Tropospheric and stratospheric temperatures and aerosol opacity are derived via optimal estimation retrievals (Fletcher et al. 2009, Icarus, 200, p154). Enhancement of hydrocarbons and gaseous ammonia are determined via iterative forward modelling, aided by spectral observations obtained with the slit aligned east-west through the impact feature from Gemini-S/TReCS (July 24) and VLT/VISIR (July 26, August 12-13). Low-resolution N-band (8-13 microns) Gemini-S/TReCS spectra confirm the enhanced emission over a broad range of wavelengths; Q-band (17-25 micron) spectra are used to study upper tropospheric temperatures in the aftermath of the collision and the rate of radiative cooling. VLT/VISIR spectra provide higher spectral resolutions in narrow wavelength ranges near 8.02, 10.49, 11.31, 11.60, 12.24 and 13.36 microns, sensitive to NH3, CH4 and hydrocarbon emission features. Iterative forward modelling of these spectra will be used to deduce the unique chemical composition and the three-dimensional thermal structure of the impact site, compared with the ‘unperturbed’ atmosphere at the same latitude. * Fletcher is supported by an appointment to the NASA Postdoctoral Program at the Jet Propulsion Laboratory/California Institute of Technology, administered by Oak Ridge Associated Universities through a contract with NASA. We wish to acknowledge the invaluable contributions of the support staff at IRTF, VLT and Gemini.

Beryllium abundances along the evolutionary sequence of the open cluster IC 4651 - A new test for hydrodynamical stellar models

NASA Astrophysics Data System (ADS)

Smiljanic, R.; Pasquini, L.; Charbonnel, C.; Lagarde, N.

2010-02-01

Context. Previous analyses of lithium abundances in main sequence and red giant stars have revealed the action of mixing mechanisms other than convection in stellar interiors. Beryllium abundances in stars with Li abundance determinations can offer valuable complementary information on the nature of these mechanisms. Aims: Our aim is to derive Be abundances along the whole evolutionary sequence of an open cluster. We focus on the well-studied open cluster IC 4651. These Be abundances are used with previously determined Li abundances, in the same sample stars, to investigate the mixing mechanisms in a range of stellar masses and evolutionary stages. Methods: Atmospheric parameters were adopted from a previous abundance analysis by the same authors. New Be abundances have been determined from high-resolution, high signal-to-noise UVES spectra using spectrum synthesis and model atmospheres. The careful synthetic modeling of the Be lines region is used to calculate reliable abundances in rapidly rotating stars. The observed behavior of Be and Li is compared to theoretical predictions from stellar models including rotation-induced mixing, internal gravity waves, atomic diffusion, and thermohaline mixing. Results: Beryllium is detected in all the main sequence and turn-off sample stars, both slow- and fast-rotating stars, including the Li-dip stars, but is not detected in the red giants. Confirming previous results, we find that the Li dip is also a Be dip, although the depletion of Be is more modest than for Li in the corresponding effective temperature range. For post-main-sequence stars, the Be dilution starts earlier within the Hertzsprung gap than expected from classical predictions, as does the Li dilution. A clear dispersion in the Be abundances is also observed. Theoretical stellar models including the hydrodynamical transport processes mentioned above are able to reproduce all the observed features well. These results show a good theoretical understanding of the Li and Be behavior along the color-magnitude diagram of this intermediate-age cluster for stars more massive than 1.2 M⊙. Based on observations made with the ESO VLT, at Paranal Observatory, under programs 065.L-0427 and 067.D-0126.Current address: European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany.

TOPoS. IV. Chemical abundances from high-resolution observations of seven extremely metal-poor stars

NASA Astrophysics Data System (ADS)

Bonifacio, P.; Caffau, E.; Spite, M.; Spite, F.; Sbordone, L.; Monaco, L.; François, P.; Plez, B.; Molaro, P.; Gallagher, A. J.; Cayrel, R.; Christlieb, N.; Klessen, R. S.; Koch, A.; Ludwig, H.-G.; Steffen, M.; Zaggia, S.; Abate, C.

2018-04-01

Context. Extremely metal-poor (EMP) stars provide us with indirect information on the first generations of massive stars. The TOPoS survey has been designed to increase the census of these stars and to provide a chemical inventory that is as detailed as possible. Aims: Seven of the most iron-poor stars have been observed with the UVES spectrograph at the ESO VLT Kueyen 8.2 m telescope to refine their chemical composition. Methods: We analysed the spectra based on 1D LTE model atmospheres, but also used 3D hydrodynamical simulations of stellar atmospheres. Results: We measured carbon in six of the seven stars: all are carbon-enhanced and belong to the low-carbon band, defined in the TOPoS II paper. We measured lithium (A(Li) = 1.9) in the most iron-poor star (SDSS J1035+0641, [Fe/H] <-5.2). We were also able to measure Li in three stars at [Fe/H] -4.0, two of which lie on the Spite plateau. We confirm that SDSS J1349+1407 is extremely rich in Mg, but not in Ca. It is also very rich in Na. Several of our stars are characterised by low α-to-iron ratios. Conclusions: The lack of high-carbon band stars at low metallicity can be understood in terms of evolutionary timescales of binary systems. The detection of Li in SDSS J1035+0641 places a strong constraint on theories that aim at solving the cosmological lithium problem. The Li abundance of the two warmer stars at [Fe/H] -4.0 places them on the Spite plateau, while the third, cooler star, lies below. We argue that this suggests that the temperature at which Li depletion begins increases with decreasing [Fe/H]. SDSS J1349+1407 may belong to a class of Mg-rich EMP stars. We cannot assess if there is a scatter in α-to-iron ratios among the EMP stars or if there are several discrete populations. However, the existence of stars with low α-to-iron ratios is supported by our observations. Based on observations obtained at ESO Paranal Observatory, Programmes 189.D-0165,090.D-0306, 093.D-0136, and 096.D-0468.

The VLT-FLAMES Tarantula Survey

NASA Astrophysics Data System (ADS)

Vink, Jorick S.; Evans, C. J.; Bestenlehner, J.; McEvoy, C.; Ramírez-Agudelo, O.; Sana, H.; Schneider, F.; VFTS Collaboration

2017-11-01

We present a number of notable results from the VLT-FLAMES Tarantula Survey (VFTS), an ESO Large Program during which we obtained multi-epoch medium-resolution optical spectroscopy of a very large sample of over 800 massive stars in the 30 Doradus region of the Large Magellanic Cloud (LMC). This unprecedented data-set has enabled us to address some key questions regarding atmospheres and winds, as well as the evolution of (very) massive stars. Here we focus on O-type runaways, the width of the main sequence, and the mass-loss rates for (very) massive stars. We also provide indications for the presence of a top-heavy initial mass function (IMF) in 30 Dor.

SBS 0335-052E+W: deep VLT/FORS+UVES spectroscopy of the pair of the lowest-metallicity blue compact dwarf galaxies

NASA Astrophysics Data System (ADS)

Izotov, Y. I.; Guseva, N. G.; Fricke, K. J.; Papaderos, P.

2009-08-01

Context: We present deep archival VLT/FORS1+UVES spectroscopic observations of the system of two blue compact dwarf (BCD) galaxies SBS 0335-052E and SBS 0335-052W. Aims: Our aim is to derive element abundances in different H ii regions of this unique system of galaxies and to study spatial abundance variations. Methods: The electron temperature Te (O iii) in all H ii regions, except for one, is derived from the [O iii] λ4363/(λ4959+λ5007) flux ratio. We determine ionic abundances of helium, nitrogen, oxygen, neon, sulfur, chlorine, argon and iron. The empirical relations for ionization correction factors are used to derive total abundances of these elements. Results: The oxygen abundance in the brighter eastern galaxy varies in the range 7.11 to 7.32 in different H ii regions supporting previous findings and suggesting the presence of oxygen abundance variations on spatial scales of ~1-2 kpc. Good seeing during FORS observations allowed us to extract spectra of four H ii regions in SBS 0335-052W. The oxygen abundance in the brightest region No. 1 of SBS 0335-052W is 7.22 ± 0.07, consistent with previous determinations. Three other H ii regions are much more metal-poor with an unprecedently low oxygen abundance of 12 + log O/H = 7.01 ± 0.07 (region No. 2), 6.98 ± 0.06 (region No. 3), and 6.86 ± 0.14 (region No. 4). These are the lowest oxygen abundances ever derived in emission-line galaxies, supporting earlier conclusions that SBS 0335-052W is the lowest-metallicity emission-line galaxy known. Helium abundances derived for the brightest H ii regions of both galaxies are mutually consistent. We derive weighted mean He mass fractions of 0.2485 ± 0.0012 and 0.2514 ± 0.0012 for two different sets of He i emissivities. The ratios of neon and sulfur to oxygen abundance are similar to the respective ratios obtained for other emission-line galaxies. On the other hand, the chlorine-to-oxygen abundance ratio in SBS 0335-052E is lower, while the argon-to-oxygen abundance ratio is higher than those in other low-metallicity galaxies. The Fe/O abundance ratios in different regions of SBS 0335-052E are among the highest for emission-line galaxies implying that iron is almost entirely not depleted onto dust grains despite dust being detected in this galaxy in earlier ISO and Spitzer observations. The N/O abundance ratio in both galaxies is slightly higher than that derived for other BCDs with 12 + log O/H < 7.6. This implies that the N/O in extremely metal-deficient galaxies could increase with decreasing metallicity. Based on observations collected at the European Southern Observatory, Chile, ESO program 69.C-0203(A), 71.B-0055(A)), 70.B-0717(A) and 68.B-0310(A). Tables [see full textsee full text]-[see full textsee full text] are only available in electronic form at http://www.aanda.org

Are beryllium abundances anomalous in stars with giant planets?

NASA Astrophysics Data System (ADS)

Santos, N. C.; Israelian, G.; García López, R. J.; Mayor, M.; Rebolo, R.; Randich, S.; Ecuvillon, A.; Domínguez Cerdeña, C.

2004-12-01

In this paper we present beryllium (Be) abundances in a large sample of 41 extra-solar planet host stars, and for 29 stars without any known planetary-mass companion, spanning a large range of effective temperatures. The Be abundances were derived through spectral synthesis done in standard Local Thermodynamic Equilibrium, using spectra obtained with various instruments. The results seem to confirm that overall, planet-host stars have ``normal'' Be abundances, although a small, but not significant, difference might be present. This result is discussed, and we show that this difference is probably not due to any stellar ``pollution'' events. In other words, our results support the idea that the high-metal content of planet-host stars has, overall, a ``primordial'' origin. However, we also find a small subset of planet-host late-F and early-G dwarfs that might have higher than average Be abundances. The reason for the offset is not clear, and might be related either to the engulfment of planetary material, to galactic chemical evolution effects, or to stellar-mass differences for stars of similar temperature. Based on observations collected with the VLT/UT2 Kueyen telescope (Paranal Observatory, ESO, Chile) using the UVES spectrograph (Observing runs 66.C-0116 A, 66.D-0284 A, and 68.C-0058 A), and with the William Herschel and Nordic Optical Telescopes, operated on the island of La Palma by the Isaac Newton Group and jointly by Denmark, Finland, Iceland, and Norway, respectively, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

Abundance analysis of the supergiant stars HD 80057 and HD 80404 based on their UVES Spectra

NASA Astrophysics Data System (ADS)

Tanrıverdi, T.; Baştürk, Ö.

2016-08-01

This study presents elemental abundances of the early A-type supergiant HD 80057 and the late A-type supergiant HD 80404. High resolution and high signal-to-noise ratio spectra published by the UVES Paranal Observatory Project (Bagnulo et al., 2003) were analyzed to compute their elemental abundances using ATLAS9 (Kurucz, 1993; 2005; Sbordone et al., 2004). In our analysis we assumed local thermodynamic equilibrium. The atmospheric parameters of HD 80057 used in this study are from Firnstein and Przybilla (2012), and that of HD 80404 are derived from spectral energy distribution, ionization equilibria of Cr I/II and Fe I/II, the fits to the wings of Balmer and Paschen lines as Teff = 7700 ± 150 K and log g = 1.60 ± 0.15 (in cgs). The microturbulent velocities of HD 80057 and HD 80404 have been determined as 4.3 ± 0.1 and 2.2 ± 0.0 km s^-1, respectively. The rotational velocities are 15 ± 1 and 7 ± 2 km s^-1 and their macroturbulence velocities are 24 ± 2 and 2 ± 1 km s^1. We have given the abundances of 25 ions of 19 elements for HD 80057 and 36 ions of 25 elements for HD 80404. The abundances are close to solar values, except for some elements (Na, Sc, Ti, V, Ba, and Sr). We have found the metallicities [M/H] for HD 80057 and HD 80404 as -0.16 ± 0.24 and -0.04 ± 0.16 dex, respectively. The evolutionary status of these stars are discussed and their nitrogen-to-carbon (N/C) and nitrogen-to-oxygen (N/O) ratios show that they are in their blue supergiant phase before the red supergiant region.

A water vapour monitor at Paranal Observatory

NASA Astrophysics Data System (ADS)

Kerber, Florian; Rose, Thomas; Chacón, Arlette; Cuevas, Omar; Czekala, Harald; Hanuschik, Reinhard; Momany, Yazan; Navarrete, Julio; Querel, Richard R.; Smette, Alain; van den Ancker, Mario E.; Cure, Michel; Naylor, David A.

2012-09-01

We present the performance characteristics of a water vapour monitor that has been permanently deployed at ESO's Paranal observatory as a part of the VISIR upgrade project. After a careful analysis of the requirements and an open call for tender, the Low Humidity and Temperature Profiling microwave radiometer (LHATPRO), manufactured by Radiometer Physics GmbH (RPG), has been selected. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ~2.5 mm). The unit comprises the above humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared radiometer (~10 μm) for cloud detection. The instrument has been commissioned during a 2.5 week period in Oct/Nov 2011, by comparing its measurements of PWV and atmospheric profiles with the ones obtained by 22 radiosonde balloons. In parallel an IR radiometer (Univ. Lethbridge) has been operated, and various observations with ESO facility spectrographs have been taken. The RPG radiometer has been validated across the range 0.5 - 9 mm demonstrating an accuracy of better than 0.1 mm. The saturation limit of the radiometer is about 20 mm. Currently, the radiometer is being integrated into the Paranal infrastructure to serve as a high time-resolution monitor in support of VLT science operations. The water vapour radiometer's ability to provide high precision, high time resolution information on this important aspect of the atmosphere will be most useful for conducting IR observations with the VLT under optimal conditions.

The Harsh Destiny of a Planet?

NASA Astrophysics Data System (ADS)

2001-05-01

The VLT Uncovers Traces of Stellar Cannibalism Summary Did the star HD 82943 swallow one of its planets? What may at a first glance look like the recipe for a dramatic science-fiction story is in fact the well-considered conclusion of a serious scientific study, to be published by a group of astronomers in Switzerland and Spain [1] in tomorrow's issue of the international research journal "Nature". Using the very efficient UVES high-resolution spectrograph at the ESO VLT 8.2-m KUEYEN telescope , they have convincingly detected the presence of the rare isotope Lithium-6 ( 6 Li; [2]) in this metal-rich, solar-type dwarf star that is also known to possess a planetary system, cf. ESO Press Release 13/00. Unlike the Lithium-7 ( 7 Li) isotope of this light element, any primordial Lithium-6 would not survive the early evolutionary stages of a metal-rich solar-type star. The Lithium-6 now seen in HD 82943 must therefore have been added later, but from where? The astronomers believe that this observation strongly suggests that the star has at some moment engulfed one of its planets, whose Lithium-6 was then deposited in the star's atmosphere. This surprising discovery represents important observational evidence that planets may fall into their host stars. PR Photo 17/01 : The spectrum of HD 82943 with the Lithium absorption lines . Artist's impression (drawing and video) of the engulfment of a planet. HD 82943 and its planetary system The last few years have seen the discovery of more than 60 new planetary systems. One of the most prolific planet search programmes is being carried out by the Geneva Extra-Solar Planet Search Group , by means of the CORALIE spectrograph at the 1.2-m Leonard Euler Swiss Telescope at the ESO La Silla Observatory (Chile). One of the stars included in this programme is the dwarf star HD 82943 in the constellation Hydra (The Water Snake). It is slightly hotter and larger than the Sun and was recently found to harbour a planetary system with (at least) two giant planets, cf. ESO Press Release 07/01. Like most extra-solar planets ("exoplanets") found to date, the orbits of the objects orbiting HD 82943 are quite unlike those expected from traditional theories of the formation and evolution of such systems [3]. Contrary to the giant planets in the Solar System, those at HD 82943 have rather elongated orbits, and they are unsually close to the central star. Astronomers believe that giant planets must form in comparatively cool environments, as this was the case in the solar system. The existence of systems in which the giant planets are much closer to the central star can only be explained by certain dynamical processes, e.g. significant orbital changes with time ("orbital migration") or the effects of strong gravitational interaction between several planets. These processes can explain the short-period planetary systems found to date, in which planets are very close to the central star, and also the very elongated orbits found in some cases. These theories also predict that it may be the fate of some planets to fall into their host star. The significance of Lithium Unlike most other elements lighter than Iron, the light nuclei of Lithium (both the Lithium-6 and Lithium-7 isotopes [2]), Beryllium and Boron are not produced in significant amounts in the stellar spheres of fire. In fact, Lithium-6 is extremely "fragile", being easily destroyed by proton collisions at a temperature of "only" 1.5 million degrees - by comparison, the fusion of Hydrogen to Helium takes place at about 10 million degrees. In the case of solar-like stars , any Lithium-6 atoms present in a newborn star will be ``burnt'' during the early evolutionary stages. Strong internal motions will thoroughly mix the outer (cooler) and inner (hotter) stellar layers, and Lithium-6 will completely disappear in just a few million years. We would therefore not expect to find any Lithium-6 in a developed solar-type star. However, during the later evolutionary stages the outer layers of a solar-type star remain better "separated" from the hotter central parts. Thus, if some Lithium-6 is now picked up from the outside, it is therefore possible that it will be preserved in the upper, cooler regions for some time, possibly billions of years. Unlike stars, planets never reach temperatures that are high enough to burn their initial content of Lithium-6. Consequently, planets will retain their Lithium-6. So, if a planet happens to fall into a solar-type star like HD 82943, we may then be able to detect this isotope in the stellar spectrum. In the case of "metal-poor" stars - that are less rich in metals than the Sun - the mixing process in the early phase is less efficient and some original Lithium-6 may actually survive. Detection of Lithium-6 in HD 82943 with UVES ESO PR Photo 17/01 ESO PR Photo 17/01 [Preview - JPEG: 370 x 400 pix - 74k] [Normal - JPEG: 740 x 800 pix - 200k] [Hi-Res - JPEG: 2775 x 3000 pix - 1.2Mb] Caption : The spectrum of HD 82943 , showing the region around the Lithium absorption line. The general shape of this spectral line is caused by Lithium-7 atoms in the atmosphere of the star, while the presence of Lithium-6 causes a certain asymmetry. Model computations have been used to calculate the amount of the two Lithium isotopes; the two fully drawn curves correspond to 6 Li/ 7 Li = 0.12 (red) and no Lithium-6 (0.00; blue), respectively. The difference (O-C = Observed - Calculated) is shown below and demonstrates the very good fit for an isotopic ratio of 0.12 (red dots). Technical information about this photo is available below. The possible presence of Lithium-6 in a stellar atmosphere can be checked by means of a detailed analysis of the star's spectrum. For this, the astronomers search for a very small asymmetry in the "stronger" absorption line in the red spectral region that is caused by Lithium-7 atoms in the stellar atmosphere. However, this type of investigation is critically dependent on the availability of very detailed and "clean" spectra (i.e., very high spectral resolution and excellent signal-to-noise ratio). This is a great observational challenge and to date, only about five stars are known to display the signatures of Lithium-6 in their spectra, cf. ESO PR 08/00. In all cases, the measured isotopic abundance ratio is very small, with 6 Li/ 7 Li less than about 0.05. All of these stars are metal-poor and may have retained some of their initial Lithium-6, see above. Until now, no convincing detection of Lithium-6 has ever been made in a metal-rich , solar-type star. The UVES spectrograph at the 8.2-m VLT KUEYEN telescope is perfectly suited for this kind of study. Three high-resolution spectra of HD 82943 were obtained in June 2000 that show a significant asymmetry in the Lithium-7 absorption line, cf. PR Photo 17/01 . After a careful analysis, this asymmetry is confirmed as the spectral signature of Lithium-6 atoms. The observed abundance ratio is 6 Li/ 7 Li = 0.12. This is unusually high when compared to the detections in metal-poor stars and is in fact more compatible with the value of 0.08, observed in solar-system meteorites! HD 82943 has swallowed a planet The astronomers believe they know the answer: " The simplest and most convincing way to explain this observation is that one or more planets, or at least planetary material, have fallen into the star, sometime after it passed through its early evolutionary stage ", says Nuno Santos of the Geneva Observatory. Garik Israelian of Instituto de Astrofísica de Canarias adds: " One may also try to determine the quantity of material needed to explain the observed isotopic ratio of 0.12. Based on the mass estimate of the star HD 82943 and the known Lithium-6 content of meteorites, it appears that the star has swallowed the equivalent of a giant planet with twice the mass of Jupiter" . If the unlucky planet were of the terrestrial type, in which the relative Lithium-6 content is higher, it would have had a mass of about three times the mass of the Earth. The observational search for Lithium-6 in other stars with planetary systems now continues. In due time, it will permit to better understand the formation and evolution of the newly discovered exoplanets. In particular, it will demonstrate whether the fall of planets into their host stars is a common process or not. More information Further detailed information is available in the research article ("Evidence for planet engulfment by the star HD 82943", by G. Israelian, N.C. Santos, M. Mayor and R. Rebolo), published in the May 10, 2001, issue of the international research journal Nature. Notes [1] The team consists of Garik Israelian and Rafael Rebolo (Instituto de Astrofísica de Canarias, Spain), Nuno C. Santos and Michel Mayor (Geneva Observatory, Switzerland). [2] The nuclei of Lithium-6 ( 6 Li) atoms consist of three protons and three neutrons; those of Lithium-7 ( 7 Li) have three protons and four neutrons. Both isotopes were produced during the Big Bang and in spallation reactions in the interstellar medium. [3] According to the "traditional" view, giant planets like Jupiter would be formed by rapidly accelerating ("runaway") accretion of gas around an initial, icy "planetesimal" with a mass of about 10 Earth masses. An associated prediction was that giant planets would only be found at a distance of at least 750 million kilometres (5 Astronomical Units; or five times the distance between the Earth and the Sun) from their host stars and that their orbits would be circular, like the orbits of the planets in the Solar System. Technical information about the photo PR Photo 17/01 shows the spectrum of the V = 6.5 mag star HD 82943 , as obtained on June 7, 2000, with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope. It is based on three exposures made with Image Slicer 3 in Director's Discretionary Time in Service Mode, and each lasting 120 sec. The spectral resolution is 110,000 and the final S/N-ratio is about 500.

Implementation of the control electronics for KMOS instrument

NASA Astrophysics Data System (ADS)

Hess, Hans-Joachim; Ilijevski, Ivica; Kravcar, Helmut; Richter, Josef; Rühfel, Josef; Schwab, Christoph

2010-07-01

The KMOS Instrument is built to be one of the second generation VLT instruments. It is a highly complex multi-object spectrograph for the near infrared. Nearly 60 cryogenic mechanisms have to be controlled. This includes 24 deployable Pick-Off arms, three filter and grating wheels as well as three focus stages and four lamps with an attenuator wheel. These mechanisms and a calibration unit are supervised by three control cabinets based on the VLT standards. To follow the rotation of the Nasmyth adaptor the cabinets are mounted into a Co-rotating structure. The presentation will highlight the requirements on the electronics control and how these are met by new technologies applying a compact and reliable signal distribution. To enable high density wiring within the given space envelope flex-rigid printed circuit board designs have been installed. In addition an electronic system that detects collisions between the moving Pick-Off arms will be presented for safe operations. The control system is designed to achieve two micron resolution as required by optomechanical and flexure constraints. Dedicated LVDT sensors are capable to identify the absolute positions of the Pick- Off arms. These contribute to a safe recovery procedure after power failure or accidental collision.

A Mini-BAL Outflow at 900 pc from the Central Source: VLT/X-shooter Observations

NASA Astrophysics Data System (ADS)

Xu, Xinfeng; Arav, Nahum; Miller, Timothy; Benn, Chris

2018-05-01

We determine the physical conditions and location of the outflow material seen in the mini-BAL quasar SDSS J1111+1437 (z = 2.138). These results are based on the analysis of a high S/N, medium-resolution VLT/X-shooter spectrum. The main outflow component spans the velocity range ‑1500 to ‑3000 km s‑1 and has detected absorption troughs from both high-ionization species: C IV, N V, O VI, Si IV, P V, and S IV; and low-ionization species: H I, C II, Mg II, Al II, Al III, Si II, and Si III. Measurements of these troughs allow us to derive an accurate photoionization solution for this absorption component: a hydrogen column density, {log}({N}{{H}})={21.47}-0.27+0.21 cm‑2 and ionization parameter, {log}({U}{{H}})=-{1.23}-0.25+0.20. Troughs produced from the ground and excited states of S IV combined with the derived {U}{{H}} value allow us to determine an electron number density of {log}({n}{{e}})={3.62}-0.11+0.09 cm‑3 and to obtain the distance of the ionized gas from the central source: R={880}-260+210 pc.

Adsorption of Atoms of 3 d Metals on the Surfaces of Aluminum and Magnesium Oxide Films

NASA Astrophysics Data System (ADS)

Ramonova, A. G.; Kibizov, D. D.; Kozyrev, E. N.; Zaalishvili, V. B.; Grigorkina, G. S.; Fukutani, K.; Magkoev, T. T.

2018-01-01

The adsorption and formation of submonolayer structures of Ti, Cr, Fe, Ni, Cu on the surfaces of aluminum and magnesium oxide films formed on Mo(110) under ultrahigh vacuum conditions are studied via X-ray, ultraviolet photo-, and Auger electron spectroscopy (XPS, UVES, AES); spectroscopy of energy losses of high-resolution electrons (SELHRE); spectroscopy of the backscattering of low-energy ions (SBSLEI); infrared absorption spectroscopy (IAS); and the diffraction of slow electrons (DSE). Individual atoms and small clusters of all the investigated metals deposited on oxides acquire a positive charge, due presumably to interaction with surface defects. As the concentration of adatoms increases when the adsorption centers caused by defects are filled, charge transfer from adatoms to substrates is reduced. This is accompanied by further depolarization caused by the lateral interaction of adatoms.

The GTC exoplanet transit spectroscopy survey. V. A spectrally-resolved Rayleigh scattering slope in GJ 3470b

NASA Astrophysics Data System (ADS)

Chen, G.; Guenther, E. W.; Pallé, E.; Nortmann, L.; Nowak, G.; Kunz, S.; Parviainen, H.; Murgas, F.

2017-04-01

Aims: As a sub-Uranus-mass low-density planet, GJ 3470b has been found to show a flat featureless transmission spectrum in the infrared and a tentative Rayleigh scattering slope in the optical. We conducted an optical transmission spectroscopy project to assess the impacts of stellar activity and to determine whether or not GJ 3470b hosts a hydrogen-rich gas envelop. Methods: We observed three transits with the low-resolution Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) at the 10.4 m Gran Telescopio Canarias, and one transit with the high-resolution Ultraviolet and Visual Echelle Spectrograph (UVES) at the 8.2 m Very Large Telescope. Results: From the high-resolution data, we find that the difference of the Ca II H+K lines in- and out-of-transit is only 0.67 ± 0.22%, and determine a magnetic filling factor of about 10-15%. From the low-resolution data, we present the first optical transmission spectrum in the 435-755 nm band, which shows a slope consistent with Rayleigh scattering. Conclusions: After exploring the potential impacts of stellar activity in our observations, we confirm that Rayleigh scattering in an extended hydrogen-helium atmosphere is currently the best explanation. Further high-precision observations that simultaneously cover optical and infrared bands are required to answer whether or not clouds and hazes exist at high-altitude. Based on observations made with the Gran Telescopio Canarias (GTC), at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, on the island of La Palma, as well as observations obtained at the European Southern Observatory at Paranal, Chile in program 096.C-0258(A).

The origin and evolution of the odd-Z iron-peak elements Sc, V, Mn, and Co in the Milky Way stellar disk

NASA Astrophysics Data System (ADS)

Battistini, Chiara; Bensby, Thomas

2015-05-01

Context. Elements heavier than Li are produced in the interiors of stars. However, for many elements the exact production sites and the timescales on which they are dispersed into the interstellar medium are unknown. Having a clear picture on the origins of the elements is important for our ability to trace and understand the formation and chemical evolution of the Milky Way and its stellar populations. Aims: The aim of this study is to investigate the origin and evolution of Sc, V, Mn, and Co for a homogeneous and statistically significant sample of stars probing the different populations of the Milky Way, in particular the thin and thick disks. Methods: Using high-resolution spectra obtained with the MIKE, FEROS, SOFIN, FIES, UVES, and HARPS spectrographs, we determine Sc, V, Mn, and Co abundances for a large sample of F and G dwarfs in the solar neighborhood. The method is based on spectral synthesis and using one-dimensional, plane-parallel, local thermodynamic equilibrium (LTE) model stellar atmospheres calculated with the MARCS 2012 code. The non-LTE (NLTE) corrections from the literature were applied to Mn and Co. Results: We find that the abundance trends derived for Sc (594 stars), V (466 stars), and Co (567 stars) are very similar to what has been observed for the α-elements in the thin and thick disks. On the contrary, Mn (569 stars) is generally underabundant relative to the Sun (i.e., [ Mn/Fe ] < 0) for [ Fe/H ] < 0. In addition, for Mn, when NLTE corrections are applied, the trend changes and is almost flat over the entire metallicity range of the stars in our sample (-2 ≲ [ Fe/H ] ≲ + 0.4). The [Sc/Fe]-[Fe/H] abundance trends show a small separation between the thin and thick disks, while for V and Co they completely overlap. For Mn there is a small difference in [Mn/Fe], but only when NLTE corrections are used. Comparisons with Ti as a reference element show flat trends for all the elements except for Mn that show well separated [Mn/Ti]-[Ti/H] trends for the thin and thick disks. Conclusions: The elements Sc and V present trends compatible with production from type II supernovae (SNII) events. In addition, Sc clearly shows a metallicity dependence for [ Fe/H ] < -1. Instead, Mn is produced in SNII events for [ Fe/H ] ≲ -0.4 and then type Ia supernovae start to produce Mn. Finally, Co appears to be produced mainly in SNII with suggestion of enrichment from hypernovae at low metallicities. This paper includes data gathered with the 6.5 m Magellan Telescopes located at the Las Campanas Observatory, Chile; the Nordic Optical Telescope (NOT) on La Palma, Spain; the Very Large Telescope (VLT) at the European Southern Observatory (ESO) on Paranal, Chile (ESO Proposal ID 69.B-0277 and 72.B-0179); the ESO 1.5-m, 2.2-m. and 3.6-m telescopes on La Silla, Chile (ESO Proposal ID 65.L-0019, 67.B-0108, 76.B-0416, 82.B-0610); and data from UVES Paranal Observatory Project (ESO DDT Program ID 266.D-5655).Full versions of Tables 2 and 5 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A9Appendices are available in electronic form at http://www.aanda.org

Tracking Advanced Planetary Systems (TAPAS) with HARPS-N. VI. HD 238914 and TYC 3318-01333-1: two more Li-rich giants with planets

NASA Astrophysics Data System (ADS)

Adamów, M.; Niedzielski, A.; Kowalik, K.; Villaver, E.; Wolszczan, A.; Maciejewski, G.; Gromadzki, M.

2018-05-01

Context. We present the latest results of our search for planets with HARPS-N at the 3.6 m Telescopio Nazionale Galileo under the Tracking Advanced Planetary Systems project: an in-depth study of the 15 most Li abundant giants from the PennState - Toruń Planet Search sample. Aims: Our goals are first, to obtain radial velocities of the most Li-rich giants we identified in our sample to search for possible low-mass substellar companions, and second, to perform an extended spectral analysis to define the evolutionary status of these stars. Methods: This work is based on high-resolution spectra obtained with the Hobby-Eberly Telescope and its High Resolution Spectrograph, and with the HARPS-N spectrograph at the Telescopio Nazionale Galileo. Two stars, HD 181368 and HD 188214, were also observed with UVES at the VLT to determine beryllium abundances. Results: We report i) the discovery of two new planetary systems around the Li-rich giant stars: HD 238914 and TYC 3318-01333-1 (a binary system); ii) reveal a binary Li-rich giant, HD 181368; iii) although our current phase coverage is not complete, we suggest the presence of planetary mass companions around TYC 3663-01966-1 and TYC 3105-00152-1; iv) we confirm the previous result for BD+48 740 and present updated orbital parameters, and v) we find a lack of a relation between the Li enhancement and the Be abundance for the stars HD 181368 and HD 188214, for which we acquired blue spectra. Conclusions: We found seven stars with stellar or potential planetary companions among the 15 Li-rich giant stars. The binary star frequency of the Li-rich giants in our sample appears to be normal, but the planet frequency is twice that of the general sample, which suggests a possible connection between hosting a companion and enhanced Li abundance in giant stars. We also found most of the companions orbits to be highly eccentric. Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de CanariasRV data are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/613/A47

Li depletion in solar analogues with exoplanets. Extending the sample

NASA Astrophysics Data System (ADS)

Delgado Mena, E.; Israelian, G.; González Hernández, J. I.; Sousa, S. G.; Mortier, A.; Santos, N. C.; Adibekyan, V. Zh.; Fernandes, J.; Rebolo, R.; Udry, S.; Mayor, M.

2014-02-01

Aims: We want to study the effects of the formation of planets and planetary systems on the atmospheric Li abundance of planet host stars. Methods: In this work we present new determinations of lithium abundances for 326 main sequence stars with and without planets in the Teff range 5600-5900 K. The 277 stars come from the HARPS sample, the remaining targets were observed with a variety of high-resolution spectrographs. Results: We confirm significant differences in the Li distribution of solar twins (Teff = T⊙ ± 80 K, log g = log g⊙ ± 0.2 and [Fe/H] = [Fe/H]⊙ ± 0.2): the full sample of planet host stars (22) shows Li average values lower than "single" stars with no detected planets (60). If we focus on subsamples with narrower ranges in metallicity and age, we observe indications of a similar result though it is not so clear for some of the subsamples. Furthermore, we compare the observed spectra of several couples of stars with very similar parameters that show differences in Li abundances up to 1.6 dex. Therefore we show that neither age, mass, nor metallicity of a parent star is the only cause for enhanced Li depletion in solar analogues. Conclusions: We conclude that another variable must account for that difference and suggest that this could be the presence of planets that causes additional rotationally induced mixing in the external layers of planet host stars. Moreover, we find indications that the amount of depletion of Li in planet-host solar-type stars is higher when the planets are more massive than Jupiter. Based on observations collected at the La Silla Observatory, ESO (Chile), with the HARPS spectrograph at the 3.6 m ESO telescope, with CORALIE spectrograph at the 1.2 m Euler Swiss telescope and with the FEROS spectrograph at the 1.52 m ESO telescope; at the Paranal Observatory, ESO (Chile), using the UVES spectrograph at the VLT/UT2 Kueyen telescope, and with the FIES, SARG, and UES spectrographs at the 2.5 m NOT, the 3.6 m TNG and the 4.2 WHT, respectively, operated on the island of La Palma in the Spanish Observatorio del Roque de los Muchachos.Table 6 is available in electronic form at http://www.aanda.org

First light of the VLT planet finder SPHERE. II. The physical properties and the architecture of the young systems PZ Telescopii and HD 1160 revisited

NASA Astrophysics Data System (ADS)

Maire, A.-L.; Bonnefoy, M.; Ginski, C.; Vigan, A.; Messina, S.; Mesa, D.; Galicher, R.; Gratton, R.; Desidera, S.; Kopytova, T. G.; Millward, M.; Thalmann, C.; Claudi, R. U.; Ehrenreich, D.; Zurlo, A.; Chauvin, G.; Antichi, J.; Baruffolo, A.; Bazzon, A.; Beuzit, J.-L.; Blanchard, P.; Boccaletti, A.; de Boer, J.; Carle, M.; Cascone, E.; Costille, A.; De Caprio, V.; Delboulbé, A.; Dohlen, K.; Dominik, C.; Feldt, M.; Fusco, T.; Girard, J. H.; Giro, E.; Gisler, D.; Gluck, L.; Gry, C.; Henning, T.; Hubin, N.; Hugot, E.; Jaquet, M.; Kasper, M.; Lagrange, A.-M.; Langlois, M.; Le Mignant, D.; Llored, M.; Madec, F.; Martinez, P.; Mawet, D.; Milli, J.; Möller-Nilsson, O.; Mouillet, D.; Moulin, T.; Moutou, C.; Origné, A.; Pavlov, A.; Petit, C.; Pragt, J.; Puget, P.; Ramos, J.; Rochat, S.; Roelfsema, R.; Salasnich, B.; Sauvage, J.-F.; Schmid, H. M.; Turatto, M.; Udry, S.; Vakili, F.; Wahhaj, Z.; Weber, L.; Wildi, F.

2016-03-01

Context. The young systemsPZ Tel and HD 1160, hosting known low-mass companions, were observed during the commissioning of the new planet finder of the Very Large Telescope (VLT) SPHERE with several imaging and spectroscopic modes. Aims: We aim to refine the physical properties and architecture of both systems. Methods: We use SPHERE commissioning data and dedicated Rapid Eye Mount (REM) observations, as well as literature and unpublished data from VLT/SINFONI, VLT/NaCo, Gemini/NICI, and Keck/NIRC2. Results: We derive new photometry and confirm the short-term (P = 0.94 d) photometric variability of the star PZ Tel A with values of 0.14 and 0.06 mag at optical and near-infrared wavelengths, respectively. We note from the comparison to literature data spanning 38 yr that the star also exhibits a long-term variability trend with a brightening of ~0.25 mag. The 0.63-3.8 μm spectral energy distribution of PZ Tel B (separation ~25 AU) allows us to revise its physical characteristics: spectral type M7 ± 1, Teff = 2700 ± 100 K, log(g) < 4.5 dex, luminosity log(L/L⊙) = -2.51 ± 0.10 dex, and mass 38-72 MJ from "hot-start" evolutionary models combining the ranges of the temperature and luminosity estimates. The 1-3.8 μm SED of HD 1160 B (~85 au) suggests a massive brown dwarf or a low-mass star with spectral type M6.0, Teff = 3000 ± 100 K, subsolar metallicity [M/H] = -0.5-0.0 dex, luminosity log(L/L⊙) = -2.81 ± 0.10 dex, and mass 39-166 MJ. The physical properties derived for HD 1160 C (~560 au) from KsL'-band photometry are consistent with the discovery study. The orbital study of PZ Tel B confirms its deceleration and the high eccentricity of its orbit (e > 0.66). For eccentricities below 0.9, the inclination, longitude of the ascending node, and time of periastron passage are well constrained. In particular, both star and companion inclinations are compatible with a system seen edge-on. Based on "hot-start" evolutionary models, we reject other brown dwarf candidates outside 0.25'' for both systems, and giant planet companions outside 0.5'' that are more massive than 3 MJ for the PZ Tel system. We also show that K1-K2 color can be used along with YJH low-resolution spectra to identify young L-type companions, provided high photometric accuracy (≤0.05 mag) is achieved. Conclusions: SPHERE opens new horizons in the study of young brown dwarfs and giant exoplanets using direct imaging thanks to high-contrast imaging capabilities at optical (0.5-0.9 μm) and near-infrared (0.95-2.3 μm) wavelengths, as well as high signal-to-noise spectroscopy in the near-infrared domain (0.95-2.3 μm) from low resolutions (R ~ 30-50) to medium resolutions (R ~ 350). Based on data collected at the European Southern Observatory, Chile, during the commissioning of the SPHERE instrument and ESO programs 085.C-0277, 087.C-0109, 087.C-0535, and 060.A-9026.

Time-resolved High Spectral Resolution Observation of 2MASSW J0746425+200032AB

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ji; Mawet, Dimitri; Prato, Lisa, E-mail: ji.wang@caltech.edu

Many brown dwarfs (BDs) exhibit photometric variability at levels from tenths to tens of percents. The photometric variability is related to magnetic activity or patchy cloud coverage, characteristic of BDs near the L–T transition. Time-resolved spectral monitoring of BDs provides diagnostics of cloud distribution and condensate properties. However, current time-resolved spectral studies of BDs are limited to low spectral resolution ( R ∼ 100) with the exception of the study of Luhman 16 AB at a resolution of 100,000 using the VLT+CRIRES. This work yielded the first map of BD surface inhomogeneity, highlighting the importance and unique contribution of highmore » spectral resolution observations. Here, we report on the time-resolved high spectral resolution observations of a nearby BD binary, 2MASSW J0746425+200032AB. We find no coherent spectral variability that is modulated with rotation. Based on simulations, we conclude that the coverage of a single spot on 2MASSW J0746425+200032AB is smaller than 1% or 6.25% if spot contrast is 50% or 80% of its surrounding flux, respectively. Future high spectral resolution observations aided by adaptive optics systems can put tighter constraints on the spectral variability of 2MASSW J0746425+200032AB and other nearby BDs.« less

The warm-hot intergalactic medium at z ~ 2.2: Metal enrichment and ionization source

NASA Astrophysics Data System (ADS)

Bergeron, J.; Aracil, B.; Petitjean, P.; Pichon, C.

2002-12-01

Results are presented for our search for warm-hot gas towards the quasar Q 0329-385. We identify ten O VI systems of which two are within 5000 km s-1 of zem and a third one should be of intrinsic origin. The seven remaining systems have H I column densities 1013.7<=N (H I)<=1015.6 cm-2. At least ~ 1/3 of the individual O VI sub-systems have temperatures T < 1 x 105 K and cannot originate in collisionally ionized gas. Photoionization by a hard UV background field reproduces well the ionic ratios for metallicities in the range 10-2.5-10-0.5 solar, with possibly sub-solar N/C relative abundance. For [O/C]=0, the sizes inferred for the O VI clouds are in some cases larger than the maximum extent implied by the Hubble flow. This constraint is fulfilled assuming a moderate overabundance of oxygen relative to carbon. For a soft UV ionizing spectrum, an overabundance of O/C is required, [O/C]~ 0.0-1.3. For a hard(soft) U spectrum and [O/C]=0(1), the O VI regions have overdensities rho //lineρ ~ 10-40. Based on observations made at the European Southern Observatory (ESO), under prog. ID No. 166.A-0106(A), with the UVES spectrograph at the VLT, Paranal, Chile.

Exploring the Milky Way stellar disk. A detailed elemental abundance study of 714 F and G dwarf stars in the solar neighbourhood

NASA Astrophysics Data System (ADS)

Bensby, T.; Feltzing, S.; Oey, M. S.

2014-02-01

Aims: The aim of this paper is to explore and map the age and abundance structure of the stars in the nearby Galactic disk. Methods: We have conducted a high-resolution spectroscopic study of 714 F and G dwarf and subgiant stars in the Solar neighbourhood. The star sample has been kinematically selected to trace the Galactic thin and thick disks to their extremes, the metal-rich stellar halo, sub-structures in velocity space such as the Hercules stream and the Arcturus moving group, as well as stars that cannot (kinematically) be associated with either the thin disk or the thick disk. The determination of stellar parameters and elemental abundances is based on a standard analysis using equivalent widths and one-dimensional, plane-parallel model atmospheres calculated under the assumption of local thermodynamical equilibrium (LTE). The spectra have high resolution (R = 40 000-110 000) and high signal-to-noise (S/N = 150-300) and were obtained with the FEROS spectrograph on the ESO 1.5 m and 2.2 m telescopes, the SOFIN and FIES spectrographs on the Nordic Optical Telescope, the UVES spectrograph on the ESO Very Large Telescope, the HARPS spectrograph on the ESO 3.6 m telescope, and the MIKE spectrograph on the Magellan Clay telescope. The abundances from individual Fe i lines were were corrected for non-LTE effects in every step of the analysis. Results: We present stellar parameters, stellar ages, kinematical parameters, orbital parameters, and detailed elemental abundances for O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba for 714 nearby F and G dwarf stars. Our data show that there is an old and α-enhanced disk population, and a younger and less α-enhanced disk population. While they overlap greatly in metallicity between -0.7 < [Fe/H] ≲ +0.1, they show a bimodal distribution in [α/Fe]. This bimodality becomes even clearer if stars where stellar parameters and abundances show larger uncertainties (Teff ≲ 5400 K) are discarded, showing that it is important to constrain the data set to a narrow range in the stellar parameters if small differences between stellar populations are to be revealed. In addition, we find that the α-enhanced population has orbital parameters placing the stellar birthplaces in the inner Galactic disk while the low-α stars mainly come from the outer Galactic disk, fully consistent with the recent claims of a short scale-length for the α-enhanced Galactic thick disk. We have also investigated the properties of the Hercules stream and the Arcturus moving group and find that neither of them presents chemical or age signatures that could suggest that they are disrupted clusters or extragalactic accretion remnants from ancient merger events. Instead, they are most likely dynamical features originating within the Galaxy. We have also discovered that a standard 1D, LTE analysis, utilising ionisation and excitation balance of Fe i and Fe ii lines produces a flat lower main sequence. As the exact cause for this effect is unclear we chose to apply an empirical correction. Turn-off stars and more evolved stars appear to be unaffected. This paper includes data gathered with the 6.5 m Magellan Telescopes located at the Las Campanas Observatory, Chile; the Nordic Optical Telescope (NOT) on La Palma, Spain; the Very Large Telescope (VLT) at the European Southern Observatory (ESO) on Paranal, Chile (ESO Proposal ID 69.B-0277 and 72.B-0179); the ESO 1.5 m, 2.2 m, and 3.6 m telescopes on La Silla, Chile (ESO Proposal ID 65.L-0019, 67.B-0108, 76.B-0416, 82.B-0610); and data from the UVES Paranal Observatory Project (ESO DDT Program ID 266.D-5655).Full Tables C.1-C.3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/562/A71Appendices are available in electronic form at http://www.aanda.org

Imaging Red Supergiants with VLT/SPHERE/ZIMPOL

NASA Astrophysics Data System (ADS)

Cannon, Emily

2018-04-01

In the red supergiant (RSG) phase of evolution massive stars show powerful stellar winds, which strongly influence the supernova (progenitor) properties and control the nature of the compact object that is left behind. Material that is lost in the stellar wind, together with that ejected in the final core collapse, contributes to the chemical enrichment of the local interstellar medium. The mass-loss properties of RSGs are however poorly constrained. Moreover, little is known about the wind driving mechanism. To provide better constraints on both mass-loss rates and physics, high angular resolution observations are needed to unveil the inner regions of the circumstellar environment, where the mass loss is triggered. Using the VLT-SPHERE/ZIMPOL adaptive optics imaging polarimeter, spatially resolved images of four nearby RSGs were obtained in four filters. From these data, we obtain information on geometrical structures in the inner wind, the onset radius and spatial distribution of dust grains, and dust properties such as grain size. As dust grains may play a role in initiating and/or driving the outflow, this could provide us with clues as to the wind driving mechanism.

THE COS/UVES ABSORPTION SURVEY OF THE MAGELLANIC STREAM. I. ONE-TENTH SOLAR ABUNDANCES ALONG THE BODY OF THE STREAM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fox, Andrew J.; Richter, Philipp; Wakker, Bart P.

2013-08-01

The Magellanic Stream (MS) is a massive and extended tail of multi-phase gas stripped out of the Magellanic Clouds and interacting with the Galactic halo. In this first paper of an ongoing program to study the Stream in absorption, we present a chemical abundance analysis based on HST/COS and VLT/UVES spectra of four active galactic nuclei (RBS 144, NGC 7714, PHL 2525, and HE 0056-3622) lying behind the MS. Two of these sightlines yield good MS metallicity measurements: toward RBS 144 we measure a low MS metallicity of [S/H] = [S II/H I] = -1.13 {+-} 0.16 while toward NGCmore » 7714 we measure [O/H] = [O I/H I] = -1.24 {+-} 0.20. Taken together with the published MS metallicity toward NGC 7469, these measurements indicate a uniform abundance of Almost-Equal-To 0.1 solar along the main body of the Stream. This provides strong support to a scenario in which most of the Stream was tidally stripped from the SMC Almost-Equal-To 1.5-2.5 Gyr ago (a time at which the SMC had a metallicity of Almost-Equal-To 0.1 solar), as predicted by several N-body simulations. However, in Paper II of this series, we report a much higher metallicity (S/H = 0.5 solar) in the inner Stream toward Fairall 9, a direction sampling a filament of the MS that Nidever et al. claim can be traced kinematically to the Large Magellanic Cloud, not the Small Magellanic Cloud. This shows that the bifurcation of the Stream is evident in its metal enrichment, as well as its spatial extent and kinematics. Finally we measure a similar low metallicity [O/H] = [O I/H I] = -1.03 {+-} 0.18 in the v{sub LSR} = 150 km s{sup -1} cloud toward HE 0056-3622, which belongs to a population of anomalous velocity clouds near the south Galactic pole. This suggests these clouds are associated with the Stream or more distant structures (possibly the Sculptor Group, which lies in this direction at the same velocity), rather than tracing foreground Galactic material.« less

Fundamental constants and high-resolution spectroscopy

NASA Astrophysics Data System (ADS)

Bonifacio, P.; Rahmani, H.; Whitmore, J. B.; Wendt, M.; Centurion, M.; Molaro, P.; Srianand, R.; Murphy, M. T.; Petitjean, P.; Agafonova, I. I.; D'Odorico, S.; Evans, T. M.; Levshakov, S. A.; Lopez, S.; Martins, C. J. A. P.; Reimers, D.; Vladilo, G.

2014-01-01

Absorption-line systems detected in high resolution quasar spectra can be used to compare the value of dimensionless fundamental constants such as the fine-structure constant, α, and the proton-to-electron mass ratio, μ = m_p/m_e, as measured in remote regions of the Universe to their value today on Earth. In recent years, some evidence has emerged of small temporal and also spatial variations in α on cosmological scales which may reach a fractional level of ≈ 10 ppm (parts per million). We are conducting a Large Programme of observations with the Very Large Telescope's Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high-resolution ({R ≈ 60 000}) and high signal-to-noise ratio (S/N ≈ 100) spectra calibrated specifically to study the variations of the fundamental constants. We here provide a general overview of the Large Programme and report on the first results for these two constants, discussed in detail in Molaro et al. (2013) and Rahmani et al. (2013). A stringent bound for Δα/α is obtained for the absorber at z_abs = 1.6919 towards HE 2217-2818. The absorption profile is complex with several very narrow features, and is modeled with 32 velocity components. The relative variation in α in this system is +1.3± 2.4_stat ± 1.0_sys ppm if Al II λ 1670 Å and three Fe II transitions are used, and +1.1 ± 2.6_stat ppm in a slightly different analysis with only Fe II transitions used. This is one of the tightest bounds on α-variation from an individual absorber and reveals no evidence for variation in α at the 3-ppm precision level (1σ confidence). The expectation at this sky position of the recently-reported dipolar variation of α is (3.2-5.4)±1.7 ppm depending on dipole model used and this constraint of Δα/α at face value is not supporting this expectation but not inconsistent with it at the 3σ level. For the proton-to-electron mass ratio the analysis of the H_2 absorption lines of the z_abs ≈ 2.4018 damped Lyα system towards HE 0027-1836 provides Δμ/μ = (-7.6 ± 8.1_stat ± 6.3_sys) ppm which is also consistent with a null variation. The cross-correlation analysis between individual exposures taken over three years and comparison with almost simultaneous asteroid observations revealed the presence of a possible wavelength dependent velocity drift as well as of inter-order distortions which probably dominate the systematic error and are a significant obstacle to achieve more accurate measurements. Based on observations obtained with UVES at the the 8.2 m Kueyen ESO telescope programme L185.A-0745.

Looking on the bright side: The story of AA Doradus as revealed by its cool companion

NASA Astrophysics Data System (ADS)

Vučković, M.; Østensen, R. H.; Németh, P.; Bloemen, S.; Pápics, P. I.

2016-02-01

The effects of irradiation on the secondary stars of close binary systems are crucial for reliably determining the system parameters and for understanding the close binary evolution. They affect the stellar structure of the irradiated star and are reflected in the appearance of characteristic features in the spectroscopic and photometric data of these systems. We aim to study the light that originates from the irradiated side of the low-mass component of a close binary eclipsing system, which comprises a hot subdwarf primary and a low mass companion, to precisely interpret their high precision photometric and spectroscopic data, and accurately determine their system and surface parameters. We reanalyse the archival high-resolution time-resolved VLT/UVES spectra of AA Dor system, where irradiation features have already been detected. After removing the predominant contribution of the hot subdwarf primary, the residual spectra reveal more than 100 emission lines from the heated side of the secondary, which show maximum intensity close to the phases around the secondary eclipse. We analyse the residual spectrum to model the irradiation of the low-mass secondary. We perform a detailed analysis of 22 narrow emission lines of the irradiated secondary, mainly of O II, with a few significant C II lines. Their phase profiles constrain the emission region of the heated side to a radius ≥95% of the radius of the secondary, while the shape of their velocity profiles reveals two distinct asymmetry features, one at the quadrature and the other at the secondary eclipse. In addition, we identify weaker emission signatures originating from more than 70 lines, including lines from He I, N II, Si III, Ca II, and Mg II. From the emission lines of the heated side of the secondary star, we determine the radial velocity semi-amplitude of the centre-of-light and correct it to the centre-of-mass of the secondary which, in turn, gives accurate masses of both components of the AA Dor system. The resulting masses M1 = 0.46 ± 0.01 M⊙ and M2 = 0.079 ± 0.002 M⊙ are in perfect accordance with those of a canonical hot subdwarf primary and a low mass that is just at the substellar limit for the companion. We also compute a first generation atmosphere model of the low mass secondary, which includes irradiation effects and matches the observed spectrum well. We find an indication of an extended atmosphere of the irradiated secondary star. Based on observations collected at the European Southern Observatory, Chile. Program ID: 066.D-1800.

[Determination of soluble solids content in Nanfeng Mandarin by Vis/NIR spectroscopy and UVE-ICA-LS-SVM].

PubMed

Sun, Tong; Xu, Wen-Li; Hu, Tian; Liu, Mu-Hua

2013-12-01

The objective of the present research was to assess soluble solids content (SSC) of Nanfeng mandarin by visible/near infrared (Vis/NIR) spectroscopy combined with new variable selection method, simplify prediction model and improve the performance of prediction model for SSC of Nanfeng mandarin. A total of 300 Nanfeng mandarin samples were used, the numbers of Nanfeng mandarin samples in calibration, validation and prediction sets were 150, 75 and 75, respectively. Vis/NIR spectra of Nanfeng mandarin samples were acquired by a QualitySpec spectrometer in the wavelength range of 350-1000 nm. Uninformative variables elimination (UVE) was used to eliminate wavelength variables that had few information of SSC, then independent component analysis (ICA) was used to extract independent components (ICs) from spectra that eliminated uninformative wavelength variables. At last, least squares support vector machine (LS-SVM) was used to develop calibration models for SSC of Nanfeng mandarin using extracted ICs, and 75 prediction samples that had not been used for model development were used to evaluate the performance of SSC model of Nanfeng mandarin. The results indicate t hat Vis/NIR spectroscopy combinedwith UVE-ICA-LS-SVM is suitable for assessing SSC o f Nanfeng mandarin, and t he precision o f prediction ishigh. UVE--ICA is an effective method to eliminate uninformative wavelength variables, extract important spectral information, simplify prediction model and improve the performance of prediction model. The SSC model developed by UVE-ICA-LS-SVM is superior to that developed by PLS, PCA-LS-SVM or ICA-LS-SVM, and the coefficient of determination and root mean square error in calibration, validation and prediction sets were 0.978, 0.230%, 0.965, 0.301% and 0.967, 0.292%, respectively.

Tracing the Chemical Evolution of Metal-rich Galactic Bulge Globular Clusters

NASA Astrophysics Data System (ADS)

Munoz Gonzalez, Cesar; Saviane, Ivo; Geisler, Doug; Villanova, Sandro

2018-01-01

We present in this poster the metallicity characterization of the four metal rich Bulge Galactic Gobular Clusters, which have controversial metallicities. We analyzed our high-resolution spectra (using UVES-580nm and GIRAFFE-HR13 setups) for a large sample of RGB/AGB targets in each cluster in order to measure their metallicity and prove or discard the iron spread hypothesis. We have also characterized chemically stars with potentially different iron content by measuring light (O, Na, Mg, Al), alpha (Si, Ca, Ti), iron–peak (V, Cr, Ni, Mn) and s and r process (Y, Zr, Ba, Eu) elements. We have identified possible channels responsible for the chemical heterogeneity of the cluster populations, like AGB or massive fast-rotating stars contamination, or SN explosion. Also, we have analyzed the origin and evolution of these bulge GCs and their connection with the bulge itself.

The magnetic variability of the β cep star ξ1 CMa

NASA Astrophysics Data System (ADS)

Järvinen, S. P.; Hubrig, S.; Schöller, M.; Ilyin, I.

2018-07-01

ξ1 CMa is a known magnetic star showing rotationally modulated magnetic variability with a period of 2.17937 d. However, recent work based on high-resolution spectropolarimetry suggests that the rotation period is longer than 30 years. We compare our new spectropolarimetric measurements with FORS 2 at the VLT acquired on three consecutive nights in 2017 to previous FORS 1/2 measurements of the longitudinal magnetic field strength. The new longitudinal magnetic field values are in the range from 115 to 240 G and do not support the presence of a long period.

VizieR Online Data Catalog: Abundances of Population II stars in NGC 6397 (Lind+, 2008)

NASA Astrophysics Data System (ADS)

Lind, K.; Korn, A. J.; Barklem, P. S.; Grundahl, F.

2010-03-01

The target selection for the spectroscopic study is based on Stroemgren uvby photometry. The photometric observations were collected with the DFOSC instrument on the 1.5m telescope on La Silla, Chile, in 1997. Additional BVI photometric data were obtained in 2005. All spectroscopic data were collected in Service Mode, with the fibre-fed, multi-object, medium-high resolution spectrograph FLAMES/GIRAFFE at ESO-VLT. FLAMES allows for 132 objects to be observed simultaneously, with GIRAFFE in MEDUSA mode, between 2005 Mar 23 and Apr 04. (2 data files).

Titan's ground-based observations in the near-infrared.

NASA Astrophysics Data System (ADS)

Negrao, A.; Coustenis, A.; Hirtzig, M.; Lellouch, E.; Maillard, J.-P.; Rannou, P.; Gendron, E.; Drossart, P.; Combes, M.; Schmitt, B.

We have observed Titan from 1991 to 2005 between 0.8 and 2.5 microns with the Fourier Transform Spectrometer (FTS) at the Canada France Hawaii Telescope (CFHT) and the NACO adaptive optics system, at the ESO Very Large Telescope (VLT). The CFHT dataset allows us (by applying a microphysical and radiative transfer model) to explore five methane windows at 0.94, 1.08, 1.28, 1.58 and 2 microns at different longitudes and resolutions for a disk average. We will also present a selected sample of the spectra we acquired with VLT/NACO on January 16, 2005, in the K band between 2.03 and 2.40 micron (Negrão et al., 2006b). Our spectra, taken with adaptive optics, include the Huygens landing site and surrounding dark and bright areas. A comparative study of the methane absorption coefficients currently available from different sources was also performed demonstrating the great sensitivity of surface inferences to this model parameter. Based on our results, we recommend the methane absorption coefficients produced by Boudon et al. (2006) and Irwin et al. (2006) for future studies of Titan. The analysis of the data yields information on the atmosphere and surface properties. We find our data to be compatible with mixtures of water ice and tholin but have strong indication for the presence of an additional as yet unidentified component (or components) for which we offer a spectral description. The analysis of the VLT/NACO data seem to indicate a strong decrease of Titan's surface albedo between 2.03 and 2.12 microns in the Huygens landing site area. This is compatible with the presence of ices such as CH4 and H2 O at the surface. References: Negrão, A., et al. 2006a. Titan's surface albedo variations over a Titan season from near-infrared CFHT/FTS spectra Plan. Space Sci., in press; 1 Negrão, A., et al. 2006b. 2 micron spectroscopy of Huygens probe landing site on Titan with VLT/NACO. J. Geophys. Res. Planets, in press; Boudon, V., et al., 2006. The Vibrational Levels of Methane Obtained from Analyses of High-Resolution Spectra. J. Quant Spectrosc., in press; Irwin, P. G. J., et al, 2006. Improved near-infrared methane band models and k-distribution parameters from 2000 to 9500 cm-1 and implications for interpretation of outer planet spectra. Icarus, 181, 309-319. 2

Precise weak lensing constraints from deep high-resolution Ks images: VLT/HAWK-I analysis of the super-massive galaxy cluster RCS2 J 232727.7-020437 at z = 0.70

NASA Astrophysics Data System (ADS)

Schrabback, Tim; Schirmer, Mischa; van der Burg, Remco F. J.; Hoekstra, Henk; Buddendiek, Axel; Applegate, Douglas; Bradač, Maruša; Eifler, Tim; Erben, Thomas; Gladders, Michael D.; Hernández-Martín, Beatriz; Hildebrandt, Hendrik; Hoag, Austin; Klaes, Dominik; von der Linden, Anja; Marchesini, Danilo; Muzzin, Adam; Sharon, Keren; Stefanon, Mauro

2018-03-01

We demonstrate that deep good-seeing VLT/HAWK-I Ks images complemented with g + z-band photometry can yield a sensitivity for weak lensing studies of massive galaxy clusters at redshifts 0.7 ≲ z ≲ 1.1, which is almost identical to the sensitivity of HST/ACS mosaics of single-orbit depth. Key reasons for this good performance are the excellent image quality frequently achievable for Ks imaging from the ground, a highly effective photometric selection of background galaxies, and a galaxy ellipticity dispersion that is noticeably lower than for optically observed high-redshift galaxy samples. Incorporating results from the 3D-HST and UltraVISTA surveys we also obtained a more accurate calibration of the source redshift distribution than previously achieved for similar optical weak lensing data sets. Here we studied the extremely massive galaxy cluster RCS2 J232727.7-020437 (z = 0.699), combining deep VLT/HAWK-I Ks images (point spread function with a 0.''35 full width at half maximum) with LBT/LBC photometry. The resulting weak lensing mass reconstruction suggests that the cluster consists of a single overdensity, which is detected with a peak significance of 10.1σ. We constrained the cluster mass to M200c/(1015 M⊙) = 2.06-0.26+0.28(stat.) ± 0.12(sys.) assuming a spherical Navarro, Frenk & White model and simulation-based priors on the concentration, making it one of the most massive galaxy clusters known in the z ≳ 0.7 Universe. We also cross-checked the HAWK-I measurements through an analysis of overlapping HST/ACS images, yielding fully consistent estimates of the lensing signal. Based on observations conducted with the ESO Very Large Telescope, the Large Binocular Telescope, and the NASA/ESA Hubble Space Telescope, as detailed in the acknowledgements.

VLT Commissioning Data Now Publicly Available

NASA Astrophysics Data System (ADS)

1999-11-01

"First Light" was achieved in May 1998 for VLT ANTU , the first 8.2-m Unit Telescope at the Paranal Observatory ( ESO PR 06/98 ). Since then, thousands of detailed images and spectra of a great variety of celestial objects have been recorded with this major new research facility. While some of these were obtained for scientific programmes and were therefore directed towards specific research needs, others were made during the "Commissioning Phases" in 1998/99 for the two major astronomical instruments, FORS1 ( FO cal R educer and S pectrograph) and ISAAC ( I nfrared S pectrometer A nd A rray C amera). They were carried out in order to test thoroughly the performance of the telescope and its instruments before the new facility was handed over to the astronomers on April 1, 1999. The Commissioning data are accordingly of variable quality and, contrarily to the science data, normally not intensity calibrated. However, while some of these frames are short test exposures that mainly served to ascertain the image quality under various observing conditions, a substantial fraction still contains scientifically valuable data. 10 Gigabytes released As planned, and in order to facilitate the exploitation of this useful material, ESO has today released over 10 Gigabytes of ANTU Commissioning data (and some additional test data from before April 1, 1999), obtained in the various observing modes of FORS1 and ISAAC . They encompass a total of 2235 files and are now available to astronomers and other interested parties in the ESO Member States. Information about this release and on how to obtain the data on CD-ROM or in electronic form is now available via the Science Archive Facility website. A special page with the list of raw science data frames included in this release has been set up. Searches for specific data (e.g., by object, sky field, filter, time of observation; calibration files, etc.) can be made from the ESO Science Archive Data Products page. These Commissioning data are "raw" in the sense that they come directly from the instrument. The original files are recorded in standard FITS-format and in order to save space, they have been compressed by a factor of about 2. Before they can be used, they must therefore first be decompressed and subjected to image processing, e.g. with the ESO MIDAS system , available on a special MIDAS CD-ROM from ESO. The above image of a well-known spiral galaxy, Messier 83 , was prepared by superposing three CCD frames from this data release that are now available in the archive. This galaxy is located in the southern constellation Hydra (The Water-Snake) and is also known as NGC 5236 ; the distance is about 15 million light-years. The spiral structure resembles that of the Milky Way Galaxy in which we live, but Messier 83 also possesses a bar-like structure at the centre. Corresponding frames of many other interesting objects are included among the data now released. A small part of these have served to produce some of the VLT Astronomical Images that have been released at the ESO Outreach website during the past year. Current VLT observations Observations continue with the first two VLT Unit Telescopes, ANTU and KUEYEN ; the latter is still in the Commissioning Phase with the UVES and FORS2 instruments until it will be made available to the astronomers on April 1, 2000. The current VLT data production rate is about 2200 files/week, corresponding to about 10 Gigabytes or 16 CD-ROMs. Efficient data handling procedures developed by ESO ensure a rapid and secure transfer from the telescopes at the Paranal Observatory to the data archive at the Garching Headquarters, and from here to the receiving astronomers. A description of the main features of this "VLT Data Flow System" is available in PR 10/99. The amount of data will increase as more instruments enter into operation and will ultimately reach about 40,000 Gigabytes/year. The next major event will be the "First Light" for the third Unit Telescope, MELIPAL , now expected in February 2000. The preparations are proceeding well, with the 8.2-m main mirror of Zerodur about to be coated during the next days. The fourth telescope, YEPUN , will follow later next year. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Observing multiple populations in globular clusters with the ESO archive: NGC 6388 reloaded

NASA Astrophysics Data System (ADS)

Carretta, Eugenio; Bragaglia, Angela

2018-06-01

The metal-rich and old bulge globular cluster (GC) NGC 6388 is one of the most massive Galactic GCs (M 106 M⊙). However, the spectroscopic properties of its multiple stellar populations rested only on 32 red giants (only 7 of which observed with UVES, the others with GIRAFFE), given the difficulties in observing a rather distant cluster, heavily contaminated by bulge and disc field stars. We bypassed the problem using the resources of the largest telescope facility ever: the European Southern Observatory (ESO) archive. By selecting member stars identified by other programmes, we derive atmospheric parameters and the full set of abundances for 15 species from high-resolution UVES spectra of another 17 red giant branch stars in NGC 6388. We confirm that no metallicity dispersion is detectable in this GC. About 30% of the stars show the primordial composition of first-generation stars, about 20% present an extremely modified second-generation composition, and 50% have an intermediate composition. The stars are clearly distributed in the Al-O and Na-O planes in three discrete groups. We find substantial hints that more than a single class of polluters is required to reproduce the composition of the intermediate component in NGC 6388. In the heavily polluted component the sum Mg+Al increases as Al increases. The sum Mg+Al+Si is constant, and is the fossil record of hot H-burning at temperatures higher than about 70 MK in the first-generation polluters that contributed to form multiple populations in this cluster. Based on observations collected at ESO telescopes under programmes 073.D-0211 (propr ietary), and 073.D-0760, 381.D-0329, 095.D-0834 (archival).

New Quasar Studies Keep Fundamental Physical Constant Constant

NASA Astrophysics Data System (ADS)

2004-03-01

Very Large Telescope sets stringent limit on possible variation of the fine-structure constant over cosmological time Summary Detecting or constraining the possible time variations of fundamental physical constants is an important step toward a complete understanding of basic physics and hence the world in which we live. A step in which astrophysics proves most useful. Previous astronomical measurements of the fine structure constant - the dimensionless number that determines the strength of interactions between charged particles and electromagnetic fields - suggested that this particular constant is increasing very slightly with time. If confirmed, this would have very profound implications for our understanding of fundamental physics. New studies, conducted using the UVES spectrograph on Kueyen, one of the 8.2-m telescopes of ESO's Very Large Telescope array at Paranal (Chile), secured new data with unprecedented quality. These data, combined with a very careful analysis, have provided the strongest astronomical constraints to date on the possible variation of the fine structure constant. They show that, contrary to previous claims, no evidence exist for assuming a time variation of this fundamental constant. PR Photo 07/04: Relative Changes with Redshift of the Fine Structure Constant (VLT/UVES) A fine constant To explain the Universe and to represent it mathematically, scientists rely on so-called fundamental constants or fixed numbers. The fundamental laws of physics, as we presently understand them, depend on about 25 such constants. Well-known examples are the gravitational constant, which defines the strength of the force acting between two bodies, such as the Earth and the Moon, and the speed of light. One of these constants is the so-called "fine structure constant", alpha = 1/137.03599958, a combination of electrical charge of the electron, the Planck constant and the speed of light. The fine structure constant describes how electromagnetic forces hold atoms together and the way light interacts with atoms. But are these fundamental physical constants really constant? Are those numbers always the same, everywhere in the Universe and at all times? This is not as naive a question as it may seem. Contemporary theories of fundamental interactions, such as the Grand Unification Theory or super-string theories that treat gravity and quantum mechanics in a consistent way, not only predict a dependence of fundamental physical constants with energy - particle physics experiments have shown the fine structure constant to grow to a value of about 1/128 at high collision energies - but allow for their cosmological time and space variations. A time dependence of the fundamental constants could also easily arise if, besides the three space dimensions, there exist more hidden dimensions. Already in 1955, the Russian physicist Lev Landau considered the possibility of a time dependence of alpha. In the late 1960s, George Gamow in the United States suggested that the charge of the electron, and therefore also alpha, may vary. It is clear however that such changes, if any, cannot be large or they would already have been detected in comparatively simple experiments. Tracking these possible changes thus requires the most sophisticated and precise techniques. Looking back in time In fact, quite strong constraints are already known to exist for the possible variation of the fine structure constant alpha. One such constraint is of geological nature. It is based on measures taken in the ancient natural fission reactor located near Oklo (Gabon, West Africa) and which was active roughly 2,000 million years ago. By studying the distribution of a given set of elements - isotopes of the rare earths, for example of samarium - which were produced by the fission of uranium, one can estimate whether the physical process happened at a faster or slower pace than we would expect it nowadays. Thus we can measure a possible change of the value of the fundamental constant at play here, alpha. However, the observed distribution of the elements is consistent with calculations assuming that the value of alpha at that time was precisely the same as the value today. Over the 2 billion years, the change of alpha has therefore to be smaller than about 2 parts per 100 millions. If present at all, this is a rather small change indeed. But what about changes much earlier in the history of the Universe? To measure this we must find means to probe still further into the past. And this is where astronomy can help. Because, even though astronomers can't generally do experiments, the Universe itself is a huge atomic physics laboratory. By studying very remote objects, astronomers can look back over a long time span. In this way it becomes possible to test the values of the physical constants when the Universe had only 25% of is present age, that is, about 10,000 million years ago. Very far beacons To do so, astronomers rely on spectroscopy - the measurement of the properties of light emitted or absorbed by matter. When the light from a flame is observed through a prism, a rainbow is visible. When sprinkling salt on the flame, distinct yellow lines are superimposed on the usual colours of the rainbow, so-called emission lines. Putting a gas cell between the flame and the prism, one sees however dark lines onto the rainbow: these are absorption lines. The wavelength of these emission and absorption lines is directly related to the energy levels of the atoms in the salt or in the gas. Spectroscopy thus allows us to study atomic structure. The fine structure of atoms can be observed spectroscopically as the splitting of certain energy levels in those atoms. So if alpha were to change over time, the emission and absorption spectra of these atoms would change as well. One way to look for any changes in the value of alpha over the history of the Universe is therefore to measure the spectra of distant quasars, and compare the wavelengths of certain spectral lines with present-day values. Quasars are here only used as a beacon - the flame - in the very distant Universe. Interstellar clouds of gas in galaxies, located between the quasars and us on the same line of sight and at distances varying from six to eleven thousand of million light years, absorb parts of the light emitted by the quasars. The resulting spectrum consequently presents dark "valleys" that can be attributed to well-known elements. If the fine-structure constant happens to change over the duration of the light's journey, the energy levels in the atoms would be affected and the wavelengths of the absorption lines would be shifted by different amounts. By comparing the relative gaps between the valleys with the laboratory values, it is possible to calculate alpha as a function of distance from us, that is, as a function of the age of the Universe. These measures are however extremely delicate and require a very good modelling of the absorption lines. They also put exceedingly strong requirements on the quality of the astronomical spectra. They must have enough resolution to allow very precise measurement of minuscule shifts in the spectra. And a sufficient number of photons must be captured in order to provide a statistically unambiguous result. For this, astronomers have to turn to the most advanced spectral instruments on the largest telescopes. This is where the Ultra-violet and Visible Echelle Spectrograph (UVES) and ESO's Kueyen 8.2-m telescope at the Paranal Observatory is unbeatable, thanks to the unequalled spectral quality and large collecting mirror area of this combination. Constant or not? ESO PR Photo 07/04 ESO PR Photo 07/04 Relative Changes with Redshift of the Fine Structure Constant [Preview - JPEG: 496 x 400 pix - 36k] [Normal - JPEG: 991 x 800 pix - 320k] Captions: ESO PR Photo 07/04 shows measured values of the relative change of alpha from the sample of absorption systems studied by Hum Chand and his colleagues, plotted as a function of the redshift and the corresponding look-back time. The open circle is the measurement from the Oklo natural reactor. The horizontal long dashed lines show the area of the previous claim of variation of the fine structure constant. Clearly, the new UVES data are inconsistent with this range. A team of astronomers [1], led by Patrick Petitjean (Institut d'Astrophysique de Paris and Observatoire de Paris, France) and Raghunathan Srianand (IUCAA Pune, India) very carefully studied a homogeneous sample of 50 absorption systems observed with UVES and Kueyen along 18 distant quasars lines of sight. They recorded the spectra of quasars over a total of 34 nights to achieve the highest possible spectral resolution and the best signal-to-noise ratio. Sophisticated automatic procedures specially designed for this programme were applied. In addition, the astronomers used extensive simulations to show that they can correctly model the line profiles to recover a possible variation of alpha. The result of this extensive study is that over the last 10,000 million years, the relative variation of alpha must be less than 0.6 part per million. This is the strongest constraint from quasar absorption lines studies to date. More importantly, this new result does not support previous claims of a statistically significant change of alpha with time. Interestingly, this result is supported by another - less extensive - analysis, also conducted with the UVES spectrometer on the VLT [2]. Even though those observations were only concerned with one of the brightest known quasar HE 0515-4414, this independent study lends further support to the hypothesis of no variation of alpha. Even though these new results represent a significant improvement in our knowledge of the possible (non-) variation of one of the fundamental physical constants, the present set of data would in principle still allow variations that are comparatively large compared to those resulting from the measurements from the Oklo natural reactor. Nevertheless, further progress in this field is expected with the new very-high-accuracy radial velocity spectrometer HARPS on ESO's 3.6-m telescope at the La Silla Observatory (Chile). This spectrograph works at the limit of modern technology and is mostly used to detect new planets around stars other than the Sun - it may provide an order of magnitude improvement on the determination of the variation of alpha. Other fundamental constants can be probed using quasars. In particular, by studying the wavelengths of molecular hydrogen in the remote Universe, one can probe the variations of the ratio between the masses of the proton and the electron. The same team is now engaged in such a large survey with the Very Large Telescope that should lead to unprecedented constraints on this ratio. More Information The research presented in this Press Release is based on papers published in Physical Review Letters ("Limits on the time variation of the electromagnetic fine-structure constant in the low energy limit from absorption lines in the spectra of distant quasars" by Raghunathan Srianand, Hum Chand, Patrick Petitjean, and Bastien Aracil) and in the leading European astronomy journal Astronomy & Astrophysics ("Probing the cosmological variation of the fine-structure constant: Results based on VLT-UVES sample" by Hum Chand, Raghunathan Srianand, Patrick Petitjean, and Bastien Aracil).

CUBES: cassegrain U-band Brazil-ESO spectrograph

NASA Astrophysics Data System (ADS)

Barbuy, B.; Bawden Macanhan, V.; Bristow, P.; Castilho, B.; Dekker, H.; Delabre, B.; Diaz, M.; Gneiding, C.; Kerber, F.; Kuntschner, H.; La Mura, G.; Maciel, W.; Meléndez, J.; Pasquini, L.; Pereira, C. B.; Petitjean, P.; Reiss, R.; Siqueira-Mello, C.; Smiljanic, R.; Vernet, J.

2014-11-01

CUBES is a high-efficiency, medium-resolution ( R˜20,000) ground based UV (300-400 nm) spectrograph, to be installed in the cassegrain focus of one of ESO's VLT unit telescopes in 2017/18. The CUBES project is a joint venture between ESO and IAG/USP, and LNA/MCTI. CUBES will provide access to a wealth of new and relevant information for stellar as well as extragalactic sources. Main science cases include the study of beryllium and heavy elements in metal-poor stars, the direct determination of carbon, nitrogen and oxygen abundances by study of molecular bands in the UV range, as well as the study of active galactic nuclei and the quasar absorption lines. With a streamlined modern instrument design, high efficiency dispersing elements and UV-sensitive detectors, it will give a significant gain in sensitivity over existing ground based medium-high resolution spectrographs, enabling vastly increased sample sizes accessible to the astronomical community. We present here a brief overview of the project including the status, science cases and a discussion of the design options.

Speckle interferometry. Data acquisition and control for the SPID instrument.

NASA Astrophysics Data System (ADS)

Altarac, S.; Tallon, M.; Thiebaut, E.; Foy, R.

1998-08-01

SPID (SPeckle Imaging by Deconvolution) is a new speckle camera currently under construction at CRAL-Observatoire de Lyon. Its high spectral resolution and high image restoration capabilities open new astrophysical programs. The instrument SPID is composed of four main optical modules which are fully automated and computer controlled by a software written in Tcl/Tk/Tix and C. This software provides an intelligent assistance to the user by choosing observational parameters as a function of atmospheric parameters, computed in real time, and the desired restored image quality. Data acquisition is made by a photon-counting detector (CP40). A VME-based computer under OS9 controls the detector and stocks the data. The intelligent system runs under Linux on a PC. A slave PC under DOS commands the motors. These 3 computers communicate through an Ethernet network. SPID can be considered as a precursor for VLT's (Very Large Telescope, four 8-meter telescopes currently built in Chile by European Southern Observatory) very high spatial resolution camera.

Low-mass Stellar and Substellar Companions to sdB Stars

NASA Astrophysics Data System (ADS)

Geier, S.; Classen, L.; Brünner, P.; Nagel, K.; Schaffenroth, V.; Heuser, C.; Heber, U.; Drechsel, H.; Edelmann, H.; Koen, C.; O'Toole, S. J.; Morales-Rueda, L.

2012-03-01

It has been suggested that besides stellar companions, substellar objects in close orbits may be able to trigger mass loss in a common envelope phase and form hot subdwarfs. In an ongoing project we search for close substellar companions combining time resolved high resolution spectroscopy with photometry. We determine the fraction of as yet undetected radial velocity variable systems from a sample of 27 apparently single sdB stars to be ˜eq16%. We discovered low-mass stellar companions to the He-sdB CPD-20circ 1123 and the pulsator KPD 0629-0016. The brown dwarf reported to orbit the eclipsing binary SDSS J0820+0008 could be confirmed by an analysis of high resolution spectra taken with UVES. Reflection effects have been detected in the light curves of the known sdB binaries CPD -64circ 481 and BPS CS 22169-0001. The inclinations of these systems must be much higher than expected and the most likely companion masses are in the substellar regime. Finally, we determined the orbit of the sdB binary PHL 457, which has a very small radial velocity amplitude and may host the lowest mass substellar companion known. The implications of these new results for the open question of sdB formation are discussed.

New Method for Data Treatment Developed at ESO

NASA Astrophysics Data System (ADS)

1996-08-01

How Future Astronomical Observations Will be Done The past four centuries have seen dramatic improvements in astronomical equipment, in terms of better and larger telescopes, more accurate and sensitive detectors and, not the least, by advanced space instruments with access to new spectral regions. However, until recently there has been little progress on another equally important front, that of quantifying the unavoidable influence of this equipment on the astronomical data they produce . For a long time, astronomers have desired to remove efficiently these `instrumental effects' from their data, in order to give them a clearer understanding of the objects in the Universe and their properties. But it is only now that this fundamental problem can finally be tackled efficiently, with the advent of digital imaging techniques and powerful computers. Two researchers at the ESO Headquarters, Michael R. Rosa of the Space Telescope European Co-ordinating Facility (ST/ECF [1]) and Pascal Ballester of the Data Management Division (DMD) are now developing a new approach to this age-old problem. These results are important for the future use of the ESO Very Large Telescope (VLT) , the Hubble Space Telescope (HST) and other large facilities as well [2]. The observational process Observations are crucial to the progress of all natural sciences, including astronomy. Nevertheless, the properties of the observed objects are rarely revealed directly. First, observational data are gathered at the telescopes with instruments such as cameras and spectrophotometers. Then these `raw' data are processed with advanced computer programmes to produce scientifically meaningful data which are finally scrutinized by the astronomers in order to learn more about the observed celestial objects. A basic problem in this chain is the influence of the telescopes and instruments on the data they produce. The `raw' observational data carries the marks, not only of the celestial objects that are observed, but also of the `recording equipment' and, in the case of ground-based observations, of the atmospheric conditions as well. These disturbing effects, for example straylight in the telescope and light absorption in the atmosphere, are referred to as the instrumental and atmospheric `signatures'. Only when they have been `removed' from the data, can these be properly interpreted. In fact, unless these effects are completely known, an observation may not result in any new knowledge at all or, even worse, may lead to erroneous results. The history of astronomy contains many examples of the battle with instrumental effects; see also the Appendix. With the advent of new and advanced astronomical facilities like the VLT and HST, the need for an efficient solution of this fundamental problem has become particularly acute. The calibration challenge Until now, the usual procedure to tackle this common problem has been to observe socalled `reference sources' (celestial objects with well-known properties [3]) with exactly the same instrument and observational mode and under same atmospheric conditions as the celestial object under study, referred to as the `target'. A comparison between the `raw' observational data recorded for the reference sources and their known properties then allows to determine, more or less accurately, the instrumental and atmospheric signatures. Subsequently, these effects can be removed during the data processing from the raw data obtained for the programme targets. This leaves behind - at least in theory - `clean data' which only contain the desired information about the celestial object under investigation. This fundamental, observational procedure is known as `calibration'. Nevertheless, serious limitations are inherent in such a calibration procedure. In principle, it is only logically valid if the reference source has the same properties as the target and both are observed under identical instrumental and atmospheric conditions. These requirements, however, are never fulfilled in practice. One way around this obstacle is to observe a sufficient number of reference sources, the properties of which are supposed to bracket the properties of the targets. Likewise, repeated observations must be made whenever the observing conditions change. This way one hopes to obtain estimates of the instrumental and atmospheric signatures at the time of the observation of the target by means of interpolation. Until now, this empirical calibration process was the only one available. Unfortunately, it demands a lot of the valuable telescope time just for repeated observations of the reference sources, significantly diminishing the time available for observations of the scientifically important objects. Moreover, every time the instrument is even slightly changed or some condition is altered, a new calibration procedure must be carried through. Maximizing observational efficiency In just over one year from now, ESO will begin to operate the largest optical telescope ever built, the Very Large Telescope (VLT) at the new Paranal Observatory in Chile. Because of its enormous light-collecting area and superior optical quality, the VLT is destined to make a break-through in ground-based observational astronomy. The demand by astronomers for observing time at this unique facility is overwhelming. Even with the unsurpassed number of clear nights at Paranal, each available minute will be extremely precious and everything must be done to ensure that no time will be lost to unnecessary actions. This is a major challenge to the scientists. For instance, how long a time should an exposure last to ensure an optimum of new knowledge about the object observed? In addition, how much time should be spent to define in sufficient detail the `signatures' of the atmosphere, the telescope and the instruments which must be removed from the `raw' data before the resulting `clean' data can be interpreted in a trustworthy way? In short, how can the scientific return from the VLT and other telescopes such as the HST best be optimised? It is exactly for this reason that astronomers and engineers at ESO are now busy developing new methods of telescope operation and data analysis alongside with the VLT instrumental hardware itself. The new solution by means of models The appropriate strategy to make progress in the inherent conflict between calibration demand and time available for scientific observations is to obtain a physically correct understanding of the effects exerted on the data by different instruments . In this way, it is possible to decide which calibration data are actually required and on which timescale they have to be updated. One can then use computer models of these instruments to predict calibration solutions which are now valid for the full range of target properties and which handle environmental conditions properly. Such computer models can also be used to simulate observations. This brings a lot of benefits for the entire observational process. First, the astronomer can prepare observations and select instrumental modes and exposure times suited for optimal information return. Secondly, it provides confidence in the validity of the calibration process, and therefore in the cleanliness of the corrected data. Finally, once a theory about the target and its properties has been developed, one may simulate observations of a set of theoretical targets for which the properties are slightly modified in order to study their influence on the raw data. For the observatory there are also advantages. Optimization from the point of view of data analysis can now take place already during instrument design, calibration and data analysis procedures for any observational mode can be tested before real observations are obtained, and the maintenance staff can make sure that the instrument performs as expected and designed. How far have we come along this road? The present project consists of a close collaboration between the ESO Data Management Division (DMD) and Space Telescope European Co-ordinating Facility (ST/ECF). The VLT and the HST facilities have quite similar demands, because both astronomical observatories are committed to make data from a variety of instruments rapidly available to the world-wide community at a large scale. Once the basic concept had been defined, several groups at ESO started to develop models for particular instruments in order to study its general validity. One of the VLT instruments under construction is the high resolution echelle spectrograph UVES; first light is planned for 1999. The DMD model for this instrument now succeeds in predicting the geometrical aspects of observational data to better than one resolution element (pixel) of the detector. In parallel, the ST/ECF has produced a computer model for the low-resolution Faint Object Spectrograph (FOS) on HST. This software is tuned in particular to simulate the aspects of internally scattered light, which is a serious nuisance for observations of faint targets. A direct derivative of such models are accurate exposure time calculators , which the observer can use to estimate the length of each exposure when preparing his/her observing program. This is the time an electronic detector is exposed to the light of the astronomical object under study. If it is too short, the resulting image of the object will not contain enough information. On the other hand, if the exposure time is too long, the image may be degraded by too many artefacts from cosmic rays that hit the detector during the exposure, or it may saturate the detector completely. Clearly, this time may better be used to observe other objects. In order to correctly plan the length of the exposure time for each astronomical target during an observing program, it is necessary to estimate the total effect of the instrument and the atmosphere on the light produced by the target. For this it is necessary to take into account the effects of the colour-dependent atmospheric absorption and the spreading of light by turbulence (seeing), the complete propagation of the light by the telescope mirrors and by the different optical components of the instrumentation (reflection, diffusion, absorption), as well as the properties of the electronic detector. In order to allow a wide access of the scientific community to such tools, the software for these calculators is being made available on the Internet. In co-operation with a contractor, ESO has developed a complete computer model for each of the 8.2-m telescopes. This simulation model includes a large number of effects, for instance from atmospheric disturbances, wind shaking of the telescope and structural vibrations. Using this model, it is possible from simulations to predict the quality achievable, i.e. the signature of the telescope. Furthermore, the model can be used to study the effect of changes before they are implemented in practice. The success of these first modelling experiments has led to the definition of a common framework for the development of such models and the creation of a versatile software package and associated database. Within this environment, a slight modification of the UVES software was efficiently re-used to model an existing high-resolution spectrograph, CASPEC at the ESO 3.6-metre telescope, and is currently being transformed into a model for the STIS spectrograph on HST. The next steps will be to provide models for all those instruments that will become operational on the VLT and the HST in the coming years, and to study further the impact of the improved calibrations on new data analysis techniques. Appendix: Limits of observations Ever since the beginning of astronomical observations with instruments, the problem of the instrumental influence has played a significant role. Indeed, a key challenge for past and present astronomers has always been to convince critical colleagues that they have been able to achieve a clear separation in their data between the intrinsic properties of the celestial object observed on one side, and disturbing instrumental and atmospheric effects on the other side. Through the ages, many learned disputes have centered on this basic problem. For instance, the famous astronomer Tycho Brahe spent a major part of his time at the Uraniborg observatory (1576 - 1597) in trying to describe and understand the `errors' (i.e. `signatures') of his pointing instruments. This was a new approach among observers of his day which greatly contributed to his successful studies. Another early historical example is the first detection of a structure around the planet Saturn by Galileo in 1610. He was the first ever to point an optical telescope - albeit of very small size and rather bad optical quality by today's standards - towards celestial objects. To his great surprise, the disk of Saturn appeared to have two `handles' [4]. He had no means to know whether they were artifacts from light reflections inside the telescope or real objects, and in the latter case what kind of natural object this might be. In fact, it was only 50 years later that improved optical equipment which produced sharper images (`higher optical resolution') finally revealed the true nature, i.e. the well-known Saturnian rings of small particles. In this case, the issue could only be solved by awaiting the technical progress of the optical telescope. Today digital imaging and computer processing allows the astronomers to reach beyond the limits of the raw observations. But even though the equipment available to astronomers has recently made tremendous progress - the HST and VLT are prime examples - the basic problem of verifying the reality of results and correcting the `raw' data for instrumental and atmospheric signatures remains. Notes: [1] The ST/ECF is a joint undertaking of the European Space Agency (ESA) and the European Southern Observatory (ESO). [2] A presentation of the ideas and results described in this Press Release was made at the recent international workshop on `High Precision Data Analysis', held at the National Astronomical Observatory, Tokyo, Japan. [3] There exist, for instance, many `photometric standard stars' in the sky. The apparent brightness of these stars has been repeatedly measured with different instruments and is assumed known to a high degree of accuracy. [4] See also ESO Press Release 03/96 of 19 January 1996. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

VizieR Online Data Catalog: XQ-100 targets equivalent widths (Perrotta+, 2016)

NASA Astrophysics Data System (ADS)

Perrotta, S.; D'Odorico, V.; Prochaska, J. X.; Cristiani, S.; Cupani, G.; Ellison, S.; Lopez, S.; Becker, G. D.; Berg, T. A. M.; Christensen, L.; Denney, K. D.; Hamann, F.; Paris, I.; Vestergaard, M.; Worseck, G.

2018-03-01

The quasars in our sample have been originally selected and observed in a new Legacy Survey, hereafter 'XQ-100', of 100 quasars at emission redshift zem=3.5-4.5 (ESO Large Programme 189.A-0424). The observations have been carried out with X-shooter/VLT (Vernet et al., 2011A&A...536A.105V). The released spectra provide a complete coverage from the atmospheric cut-off to the NIR with a spectral resolution R~6000-9000 depending on wavelength, and a median S/N~30 at the continuum level. XQ-100 provides the first large intermediate-resolution sample of high-redshift quasars with simultaneous rest-frame UV/optical coverage. A full description of the target selection, observations, and data reduction process is presented by Lopez et al. (2016A&A...594A..91L). (2 data files).

Petroleomics by electrospray ionization FT-ICR mass spectrometry coupled to partial least squares with variable selection methods: prediction of the total acid number of crude oils.

PubMed

Terra, Luciana A; Filgueiras, Paulo R; Tose, Lílian V; Romão, Wanderson; de Souza, Douglas D; de Castro, Eustáquio V R; de Oliveira, Mirela S L; Dias, Júlio C M; Poppi, Ronei J

2014-10-07

Negative-ion mode electrospray ionization, ESI(-), with Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was coupled to a Partial Least Squares (PLS) regression and variable selection methods to estimate the total acid number (TAN) of Brazilian crude oil samples. Generally, ESI(-)-FT-ICR mass spectra present a power of resolution of ca. 500,000 and a mass accuracy less than 1 ppm, producing a data matrix containing over 5700 variables per sample. These variables correspond to heteroatom-containing species detected as deprotonated molecules, [M - H](-) ions, which are identified primarily as naphthenic acids, phenols and carbazole analog species. The TAN values for all samples ranged from 0.06 to 3.61 mg of KOH g(-1). To facilitate the spectral interpretation, three methods of variable selection were studied: variable importance in the projection (VIP), interval partial least squares (iPLS) and elimination of uninformative variables (UVE). The UVE method seems to be more appropriate for selecting important variables, reducing the dimension of the variables to 183 and producing a root mean square error of prediction of 0.32 mg of KOH g(-1). By reducing the size of the data, it was possible to relate the selected variables with their corresponding molecular formulas, thus identifying the main chemical species responsible for the TAN values.

VizieR Online Data Catalog: VLT/SINFONI observations of MIPSGAL "bubbles" (Silva+, 2017)

NASA Astrophysics Data System (ADS)

Silva, K. M.; Flagey, N.; Noriega-Crespo, A.; Carey, S.; Ingallinera, A.

2018-04-01

Data were acquired in service mode during UT 2014 May 23-June 7 using VLT/SINFONI observations. We used two of SINFONI's four gratings providing spectral resolutions R=3000 and 4000 in the H and K bands, respectively, with the field of view of 8" by 8" (without adaptive optics). The targets are 55 MIPSGAL "bubbles" (MBs) that have not been previously classified as PNe, whose central sources were unidentified at the time of the Period 93 Call for Proposals (UT 2013 October 01), and appeared to contain at least one potential central source detected in the near-IR images of the Two Micron All-Sky Survey (2MASS, Skrutskie et al. 2006, Cat. VII/233) or the UKIRT Infrared Deep Sky Survey (UKIDSS, Warren et al. 2007MNRAS.381.1400W). (5 data files).

n-capture elements in the Sculptor dwarf spheroidal galaxy

NASA Astrophysics Data System (ADS)

Skúladóttir, Ása

2018-06-01

Sculptor is a well studied dwarf galaxy in the Local Group, which is dominated by an old stellar population (>10 Gyr) and is therefore an ideal system to study early chemical evolution. With high-resolution VLT/FLAMES spectra, R~20,000, we are able to get accurate abundances of several n-capture elements in ~100 stars, from both the lighter n-capture elements (Y) as well as the heavier ones, both tracers of the s-process (e.g. Ba) and the r-process (e.g. Eu). I will discuss the similarities and differences in the n-capture elements in Sculptor and the Milky Way, as well as other dwarf galaxies.

Properties of O dwarf stars in 30 Doradus

NASA Astrophysics Data System (ADS)

Sabín-Sanjulián, Carolina; VFTS Collaboration

2017-11-01

We perform a quantitative spectroscopic analysis of 105 presumably single O dwarf stars in 30 Doradus, located within the Large Magellanic Cloud. We use mid-to-high resolution multi-epoch optical spectroscopic data obtained within the VLT-FLAMES Tarantula Survey. Stellar and wind parameters are derived by means of the automatic tool iacob-gbat, which is based on a large grid of fastwind models. We also benefit from the Bayesian tool bonnsai to estimate evolutionary masses. We provide a spectral calibration for the effective temperature of O dwarf stars in the LMC, deal with the mass discrepancy problem and investigate the wind properties of the sample.

A Deep Search for Biomarker Gases on Mars in 2009 - 2010: The Campaign and a Few Preliminary Results

NASA Astrophysics Data System (ADS)

Mumma, M. J.; Villanueva, G. L.; Novak, R.; Radeva, Y. L.; Kaufl, H.; Smette, A.; Hartogh, P.; Encrenaz, T.

2010-12-01

We searched for possible biomarker gases on Mars in the 2009-2010 observing season, emphasizing nine molecules (H2_O, CH_4_, C2_H_6_, C2_H_4_, CH3_OH, H_2_CO, H2_S, and N_2_O) of fundamental astrobiological importance along with HDO and CO2_. Our search utilized Earth’s most advanced ground-based infrared spectroscopic facilities in a campaign of several dozen observing runs spanning the period 19 August 2009 to 10 June 2010. Over this interval (L_s_ = 324 - 103 degrees), the season in Mars’ Northern hemisphere progressed from mid-winter, through vernal equinox and spring, and into early summer. We used long-slit high-resolution infrared spectrometers at the Keck and NASA-IRTF observatories in Hawaii, and the European Southern Observatory in Chile (VLT, Paranal). The spectral resolving powers ranged from ~ 35,000 (NIRSPEC/Keck and CSHELL/IRTF) to ~ 90,000 (CRIRES, VLT). At the sub-Earth point, the spatial resolution in non-AO mode ranged from ~600 km (FWHM) to ~ 400 km at Keck and IRTF. Using the adaptive optics (AO) mode at Keck and at VLT, we achieved an improved resolution of ~250 km (FWHM). We mapped the planet over the Earth-facing hemisphere by orienting the slit North-South in longitude and stepping it East-West across the planet, and we acquired deep searches over restricted longitude ranges by holding the slit fixed in position and taking sequential spectra as Mars rotated under it. Spectral lines of CO2_, H_2_O, HDO, and O2_ (a^1^Δg_) are obvious, even in the raw data. In the methane region near 3.3µm, removal of terrestrial and solar spectral lines revealed multiple lines of Mars H_2_O and CO2_, from which we extracted 2-D (lat-long) maps of Martian water vapor, atmospheric surface pressure and temperature. Subtraction of these features provided highly sensitive searches for trace gases. Preliminary results of searches for CH_4_, C2_H_4_, and C2_H_6_ will be presented in this paper. Radeva et al. (this meeting) will present preliminary results for ozone (derived from O2_ (^1^Δg_) near 1.27 µm). Villanueva et al. (this meeting) will present results for HDO (near 3.7 µm) and H_2_O (near 3.3 µm). Acknowledgements: This work was funded by NASA’s R&A Programs in Astrobiology (344-53-51), Planetary Astronomy (344-32-51-96), and Planetary Atmospheres (NNX09AB65G). We gratefully acknowledge the Director and staff of the European Southern Observatory, the Keck observatory and the NASA-IRTF observatory for supporting these observations.

An analysis of the accessibility of video lottery terminals: the case of Montréal.

PubMed

Robitaille, Eric; Herjean, Patrick

2008-01-18

Researchers and public health officials in Canada, the United States and Australia have for some time noted broader geographic accessibility to gambling establishments, above all in socioeconomically underprivileged communities. This increase in availability could lead to more and more gambling problems. This article focuses, in an ecological perspective, in particular on a spatial analysis of the geographic accessibility of sites possessing a VLT permit in the Montréal area, i.e. Montréal Island, the South Shore and Laval, from the standpoint of the development of an indicator of the vulnerability (socioeconomic components and demographic components) to gambling of populations at the level of certain neighbourhood units (dissemination areas). With the recent development of geographic information systems (GIS), it is now possible to ascertain accessibility to services much more accurately, for example by taking into account the configuration of the road network. The findings of our analysis reveal widespread geographic accessibility to sites possessing a VLT permit in the downtown area and in pericentral districts. In some neighbourhood units, a site possessing a VLT permit may be within a three-minute walk. In the region studied overall, average walking time to a VLT site is nine minutes. Access to this type of service on foot is usually limited in the outskirts. However, a number of groups of sites possessing VLT permits are found along certain axial highways. According to local spatial self-correlation analyses, the findings suggest a significant link between walking accessibility to sites possessing VLT permits and the vulnerability of the communities. In a number of neighbourhood units with ready access to VLT's the populations display high vulnerability. These findings reveal that accessibility to sites possessing a VLT permit is often linked to the vulnerability (socioeconomic and demographic components) of communities. Reliance in our analyses on neighbourhood units with fairly small areas enabled us to emphasize the rectilinear dimension of the spatial distribution of sites possessing VLT permits. This is a significant link that public health officials must consider when elaborating programs to combat pathological gambling.

Deficit of Wide Binaries in the η Chamaeleontis Young Cluster

NASA Astrophysics Data System (ADS)

Brandeker, Alexis; Jayawardhana, Ray; Khavari, Parandis; Haisch, Karl E., Jr.; Mardones, Diego

2006-12-01

We have carried out a sensitive high-resolution imaging survey of stars in the young (6-8 Myr), nearby (97 pc) compact cluster around η Chamaeleontis to search for stellar and substellar companions. Our data were obtained using the NACO adaptive optics system on the ESO Very Large Telescope (VLT). Given its youth and proximity, any substellar companions are expected to be luminous, especially in the near-infrared, and thus easier to detect next to their parent stars. Here, we present VLT NACO adaptive optics imaging with companion detection limits for 17 η Cha cluster members, and follow-up VLT ISAAC near-infrared spectroscopy for companion candidates. The widest binary detected is ~0.2", corresponding to the projected separation 20 AU, despite our survey being sensitive down to substellar companions outside 0.3", and planetary-mass objects outside 0.5". This implies that the stellar companion probability outside 0.3" and the brown dwarf companion probability outside 0.5" are less than 0.16 with 95% confidence. We compare the wide binary frequency of η Cha to that of the similarly aged TW Hydrae association and estimate the statistical likelihood that the wide binary probability is equal in both groups to be less than 2×10-4. Even though the η Cha cluster is relatively dense, stellar encounters in its present configuration cannot account for the relative deficit of wide binaries. We thus conclude that the difference in wide binary probability in these two groups provides strong evidence for multiplicity properties being dependent on environment. In two appendices we derive the projected separation probability distribution for binaries, used to constrain physical separations from observed projected separations, and summarize statistical tools useful for multiplicity studies.

VizieR Online Data Catalog: Li enrichment histories of the thick/thin disc (Fu+, 2018)

NASA Astrophysics Data System (ADS)

Fu, X.; Romano, D.; Bragaglia, A.; Mucciarelli, A.; Lind, K.; Delgado Mena, E.; Sousa, S. G.; Randich, S.; Bressan, A.; Sbordone, L.; Martell, S.; Korn, A. J.; Abia, C.; Smiljanic, R.; Jofre, P.; Pancino, E.; Tautvaisiene, G.; Tang, B.; Lanzafame, A. C.; Magrini, L.; Carraro, G.; Bensby, T.; Damiani, F.; Alfaro, E. J.; Flaccomio, E.; Morbidelli, L.; Zaggia, S.; Lardo, C.; Monaco, L.; Frasca, A.; Donati, P.; Drazdauskas, A.; Chorniy, Y.; Bayo, A.; Kordopatis, G.

2017-11-01

To investigate the Galactic lithium enrichment history we se- lect well-measured main sequence field stars with UVES spectra from the GES iDR4 catalogue. In our selection, 1884 UVES stars are marked as field stars, including those of the Galactic disc and halo designated as MW (GEMW) fields, standard CoRoT (GES D_CR) field, standard radial velocity (GES DRV) field, and stars to the Galactic Bulge direction (GEMWBL). (1 data file).

A test field for Gaia. Radial velocity catalogue of stars in the South Ecliptic Pole

NASA Astrophysics Data System (ADS)

Frémat, Y.; Altmann, M.; Pancino, E.; Soubiran, C.; Jofré, P.; Damerdji, Y.; Heiter, U.; Royer, F.; Seabroke, G.; Sordo, R.; Blanco-Cuaresma, S.; Jasniewicz, G.; Martayan, C.; Thévenin, F.; Vallenari, A.; Blomme, R.; David, M.; Gosset, E.; Katz, D.; Viala, Y.; Boudreault, S.; Cantat-Gaudin, T.; Lobel, A.; Meisenheimer, K.; Nordlander, T.; Raskin, G.; Royer, P.; Zorec, J.

2017-01-01

Context. Gaia is a space mission that is currently measuring the five astrometric parameters, as well as spectrophotometry of at least 1 billion stars to G = 20.7 mag with unprecedented precision. The sixth parameter in phase space (I.e., radial velocity) is also measured thanks to medium-resolution spectroscopy that is being obtained for the 150 million brightest stars. During the commissioning phase, two fields, one around each ecliptic pole, have been repeatedly observed to assess and to improve the overall satellite performances, as well as the associated reduction and analysis software. A ground-based photometric and spectroscopic survey was therefore initiated in 2007, and is still running to gather as much information as possible about the stars in these fields. This work is of particular interest to the validation of the radial velocity spectrometer outputs. Aims: The paper presents the radial velocity measurements performed for the Southern targets in the 12-17 R magnitude range on high- to mid-resolution spectra obtained with the GIRAFFE and UVES spectrographs. Methods: Comparison of the South Ecliptic Pole (SEP) GIRAFFE data to spectroscopic templates observed with the HERMES (Mercator in La Palma, Spain) spectrograph enabled a first coarse characterisation of the 747 SEP targets. Radial velocities were then obtained by comparing the results of three different methods. Results: In this paper, we present an initial overview of the targets to be found in the 1 sq. deg SEP region that was observed repeatedly by Gaia ever since its commissioning. In our representative sample, we identified one galaxy, six LMC S-stars, nine candidate chromospherically active stars, and confirmed the status of 18 LMC Carbon stars. A careful study of the 3471 epoch radial velocity measurements led us to identify 145 RV constant stars with radial velocities varying by less than 1 km s-1. Seventy-eight stars show significant RV scatter, while nine stars show a composite spectrum. As expected, the distribution of the RVs exhibits two main peaks that correspond to Galactic and LMC stars. By combining [Fe/H] and log g estimates, and RV determinations, we identified 203 members of the LMC, while 51 more stars are candidate members. Conclusions: This is the first systematic spectroscopic characterisation of faint stars located in the SEP field. During the coming years, we plan to continue our survey and gather additional high- and mid-resolution data to better constrain our knowledge on key reference targets for Gaia. Tables 1-3, 5, 7, and 8 are only available at the CDS via anonym- ous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/597/A10Based on data taken with the VLT-UT2 of the European Southern Observatory, programmes 084.D-0427(A), 086.D-0295(A), and 088.D-0305(A).Based on data obtained from the ESO Science Archive Facility under request number 84886.Based on data obtained with the HERMES spectrograph, installed at the Mercator Telescope, operated on the island of La Palma by the Flemish Community, at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias and supported by the Fund for Scientific Research of Flanders (FWO), Belgium, the Research Council of KU Leuven, Belgium, the Fonds National de la Recherche Scientifique (F.R.S.-FNRS), Belgium, the Royal Observatory of Belgium, the Observatoire de Genève, Switzerland and the Thüringer Landessternwarte Tautenburg, Germany.

Nitrogen line spectroscopy of O-stars. II. Surface nitrogen abundances for O-stars in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Rivero González, J. G.; Puls, J.; Najarro, F.; Brott, I.

2012-01-01

Context. Nitrogen is a key element for testing the impact of rotational mixing on evolutionary models of massive stars. Recent studies of the nitrogen surface abundance in B-type stars within the VLT-FLAMES survey of massive stars have challenged part of the corresponding predictions. To obtain a more complete picture of massive star evolution, and to allow for additional constraints, these studies need to be extended to O-stars. Aims: This is the second paper in a series aiming at the analysis of nitrogen abundances in O-type stars, to establish tighter constraints on the early evolution of massive stars. In this paper, we investigate the N ivλ4058 emission line formation, provide nitrogen abundances for a substantial O-star sample in the Large Magellanic Cloud, and compare our (preliminary) findings with recent predictions from stellar evolutionary models. Methods: Stellar and wind parameters of our sample stars were determined by line profile fitting of hydrogen, helium and nitrogen lines, exploiting the corresponding ionization equilibria. Synthetic spectra were calculated by means of the NLTE atmosphere/spectrum synthesis code fastwind, using a new nitrogen model atom. We derived nitrogen abundances for 20 O- and 5 B-stars by analyzing all nitrogen lines (from different ionization stages) present in the available optical spectra. Results: The dominating process responsible for emission at N ivλ4058 in O-stars is the strong depopulation of the lower level of the transition, which increases as a function of Ṁ. Unlike the N iii triplet emission, resonance lines do not play a role for typical mass-loss rates and below. We find (almost) no problem in fitting the nitrogen lines, in particular the "f" features. Only for some objects, where lines from N iii/N iv/N v are visible in parallel, we need to opt for a compromise solution. For five objects in the early B-/late O-star domain that have been previously analyzed by different methods and model atmospheres, we derive consistent nitrogen abundances. The bulk of our sample O-stars seems to be strongly nitrogen-enriched, and a clear correlation of nitrogen and helium enrichment is found. By comparing the nitrogen abundances as a function of v sin i ("Hunter-plot") with tailored evolutionary calculations, we identify a considerable number of highly enriched objects at low rotation. Conclusions: Our findings seem to support the basic outcome of previous B-star studies within the VLT-FLAMES survey. Owing to the low initial abundance, the detection of strong nitrogen enrichment in the bulk of O-stars indicates that efficient mixing takes place already during the very early phases of stellar evolution of LMC O-stars. For tighter constraints, however, upcoming results from the VLT-FLAMES Tarantula survey need to be waited for, which will comprise a much higher number of O-stars that will be analyzed based on similar methods as presented here. Based on observations collected at the European Southern Observatory Very Large Telescope, under programmes 68.D-0369, 171.D-0237 (FLAMES) and 67.D-0238, 70.D-0164, 074.D-0109 (UVES).Appendices A-C are available in electronic form at http://www.aanda.org

The Glory of a Nearby Star

NASA Astrophysics Data System (ADS)

2001-08-01

Optical Light from a Hot Stellar Corona Detected with the VLT Summary The solar corona is a beautiful sight during total solar eclipses . It is the uppermost region of the extended solar atmosphere and consists of a very hot (over 1 million degrees), tenuous plasma of highly ionised elements that emit strong X-ray radiation. There is also a much weaker coronal emission in the optical part of the spectrum . The Sun is a normal star and X-ray observations from rockets and orbiting X-ray telescopes have shown that many other stars also possess coronae . But due to observational limits of the telescopes available so far, the much fainter optical emission from stellar coronae had never been detected. Now, however, an optical coronal line from iron ions that have lost 12 electrons (Fe XIII) has for the first time been observed in a star other than the Sun . The object, a cool star named CN Leonis , is located at a distance of 8 light-years. This impressive observational feat was performed with the UV-Visual Echelle Spectrograph (UVES) on the VLT 8.2-m KUEYEN telescope at the ESO Paranal Observatory , within a programme by German astronomer Jürgen Schmitt and his collaborators at the University of Hamburg Observatory. The possibility to observe stellar coronae with ground-based telescopes opens up new and exciting research opportunities, including the detailed study of stellar cycles , similar to the 11-year solar period. PR Photo 24a/01 : The solar corona during the August 11, 1999, solar eclipse. PR Photo 24b/01 : The nearby star CN Leonis . PR Photo 24c/01 : Ultraviolet spectrum of CN Leonis , obtained with UVES at VLT KUEYEN. PR Photo 24d/01 : The coronal Fe XIII emission line at 3388 Ångstrom in CN Leonis . The 'coronium' mystery ESO PR Photo 24a/01 ESO PR Photo 24a/01 [Preview - JPEG: 450 x 400 pix - 26k] [Normal - JPEG: 899 x 800 pix - 328k] [HiRes - JPEG: 3000 x 2669 pix - 3.1Mk] Caption : Photo of the solar corona, obtained by Philippe Duhoux (ESO) on August 11, 1999. Two years ago, on August 11, 1999, the shadow of the Moon moved rapidly across Europe and millions of eager observers experienced a total solar eclipse , many for the first time in their lives. Those who had a clear view during the 2-min phase of totality were able to see the glorious solar corona , a shimmering halo of light around the eclipsed solar disk, cf. PR Photo 24a/01 . Some 130 years earlier, during a total solar eclipse on August, 7, 1869, American astronomers William Harkness and Charles Young observed a weak spectral emission line from the solar corona in the green region of the spectrum; it was visible for a couple of minutes. However, despite an enormous amount of work, both at the telescope during subsequent eclipses and in the laboratory, this emission line could not be attributed to any known chemical element. As the years passed, the mystery of the origin of this emission line deepened and some astronomers went as far as introducing an entirely new element named 'coronium' [1]. As better instruments became available, more coronal lines were seen during later solar eclipses. A hot corona It was only after 70 years that the coronium mystery was finally solved by two astrophysicists, Walter Grotrian from Germany and Bengt Edlén from Sweden. They showed that two observed emission lines arise from iron atoms which have lost about half their 26 electrons . By 1941, all of the coronal lines had been found to originate from such highly 'ionized atoms' . The successful identification created, however, another puzzle: in order to strip iron atoms of half of their electrons, temperatures of more than one million degrees are required, yet the temperature of the surface of the Sun is only of the order of 5500 °C! The astronomers in the 1940's were well aware that the Sun's energy is produced in the interior and that heat flows outwards from hotter to cooler regions. So how could there be a much hotter corona above the cooler photosphere? Since then, much research effort has been aimed at understanding the transport of energy in the solar atmosphere and it appears that several mechanisms play a role, including magnetic and other effects. Nevertheless, a full and detailed explanation of the high temperature of the solar corona is still outstanding. X-rays from the solar and stellar coronae An ionized gas (a 'plasma' ) at temperatures of a million or more degrees emits most of its energy at short X-ray wavelengths. X-rays do not penetrate the Earth's atmosphere and can therefore only be studied from space. Soon after World War II, the predicted X-ray emission from the solar corona was detected by American astrophysicist Herbert Friedman and his colleagues, using an X-ray detector onboard a German V-2 rocket, and hereby inaugurating the rich field of solar X-ray astronomy [1]. The Sun is a quite normal star and other stars therefore ought to possess coronae as well. Still, it took nearly 30 years until X-ray emission from other normal stars was finally detected. While X-rays from several distant objects (including the Crab Nebula, the Galactic Centre and the quasar 3C273) were discovered during the 1960's, it was only in 1975 that X-rays were registered from the bright, normal star Capella (Alpha Aurigae) during a rocket flight to study other X-ray sources. In fact, this discovery was accidental, as Capella happened to be used as a 'guide star' while the pointing direction of the rocket was ''hopping'' from one object to the next. Quite surprisingly, Capella was found to be a very strong emitter of X-rays, corresponding to an intrinsic level of more than 1000 times that of the solar corona. This discovery laid the foundation for the subsequent detection of X-ray emission from tens of thousand of stars by means of X-ray satellites, e.g., by the Einstein Observatory and especially by ROSAT. All these observations showed that stellar coronae must be a very common phenomenon . Observation of stellar coronal lines Given this widespread occurrence of stellar coronae, Jürgen Schmitt and his collaborators at the University of Hamburg (Germany) asked themselves the natural question: "What about coronal line emission from other stars in the optical (visible) region of the spectrum ? Wouldn't it be a good idea to observe coronal emission from other stars with ground-based telescopes ? In any case, observations from the ground are easier to perform and are also more economical than from space" . This may be easy to say, but it is much harder to do. The main problem is the same as when observing the solar corona. The solar coronal emission lines in the visible region of the spectrum are always observed above the solar limb. If one were to try to detect these weak lines in front of the solar disk, they would "drown" in the strong background light from the solar 'surface' (the photosphere). The original discovery of coronal emission in 1869 was indeed obtained during a solar eclipse, when this strong light is completely blocked out by the Moon. However, current telescopes are unfortunately unable to block out the light from a stellar disk in a similar way in order to make its corona visible; the angular size of the disk is too small and the positional accuracy needed for such an observation is too high for it to be feasible with present techniques. The only way forward is then a direct attempt to detect the faint coronal emission against the much higher background of the stellar disk - and that is exactly why a very large telescope is needed for such an observational feat. Selecting the target star: CN Leonis ESO PR Photo 24b/01 ESO PR Photo 24b/01 [Preview - JPEG: 681 x 400 pix - 73k] [Normal - JPEG: 1362 x 800 pix - 616k] Caption : Images of the nearby, variable star CN Leonis , in which a coronal emission line has been observed with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope. This star is relatively nearby (8 light-years) and moves about 5 arcsec/yr in the sky, approximately towards south-west (the 4 o'clock direction). The motion is clearly visible on these two images obtained with the UK Schmidt telescope and reproduced from the Second Digized Sky Survey (DSS-2); the blue image (left) was taken several years before the red one (right). Moreover, the red colour of the star is obvious; the red image is clearly brighter than the blue one. The field measures 5 x 5 arcmin 2 ; North is up and East is left. These DSS-2 images are copyright by the UK SERC/PPARC (Particle Physics and Astronomy Research Council, formerly Science and Engineering Research Council), the Anglo-Australian Telescope Board and the Association of Universities for Research in Astronomy (AURA). In order to increase the chances of success, Jürgen Schmitt and his colleagues decided to focus on optically faint, red dwarf stars . Such stars may have the same X-ray output (or even larger) than the Sun, and hence presumably possess pronounced coronae, yet their disks emit over one thousand times less visible light than does that of the Sun. They first turned their attention towards an optically faint (visual magnitude 14) and nearby (distance 8 light-years) red dwarf star (of type M5.5) known as CN Leonis , cf. PR Photo 24b/01 . It is located slightly north of the celestial equator in the constellation Leo (the Lion) and the two-letter name indicates that it is a variable star. It has been found to undergo sudden brightenings (it is a 'flare star' ), and exhibits strong magnetic activity. It is also a source of strong X-rays which the German astronomers had previously studied with the ROSAT satellite observatory and they therefore considered this star as an excellent first choice for a coronal study with the VLT. UVES detects a coronal line in the visible spectral region ESO PR Photo 24c/01 ESO PR Photo 24c/01 [Preview - JPEG: 400 x 471 pix - 31k] [Normal - JPEG: 800 x 942 pix - 81k] [Hi-Res - JPEG: 2549 x 3000 pix - 496k] ESO PR Photo 24d/01 ESO PR Photo 24d/01 [Preview - JPEG: 400 x 489 pix - 43k] [Normal - JPEG: 800 x 978 pix - 168k] Caption : Left: A small part of the near-ultraviolet spectrum of CN Leonis , obtained with UVES at the 8.2-m VLT KUEYEN telescope in January 2001, showing many emission lines from nickel atoms (Ni I) and titanium ions (Ti II). Right: "Decomposition" of an emission line at wavelength 3388.1 Ångstrom (338.81 nm) into two components. The observed spectral intensity is indicated by the 'step'-curve (in blue). As will be seen, the sum (fully drawn red line) of a strong and narrow line from titanium ions (Ti II) in the stellar chromosphere (dashed, in red) and an underlying, much broader, coronal line from 12 times ionised iron (Fe XIII; dashed, in red, slightly to the right of the titanium line) fits the observed spectral intensity curve perfectly, cf. the text. A spectrum of CN Leonis was obtained with the VLT UV-Visual Echelle Spectrograph on January 6, 2001. The spectrum covers a wide spectral region and is extremely rich in emission lines, but the team was mainly interested in one particular emission line, seen in the ultraviolet part of the spectrum at wavelength 3388.1 Ångstrom (338.81 nm). This is the wavelength at which a coronal emission line arising from 12 times ionised iron (denoted as Fe 12+ or Fe XIII ) is seen in the solar spectrum. Would the same line be visible in the spectrum of CN Leo as well ? When first inspecting the spectrum of CN Leonis ( PR Photo 24c/01 ), Jürgen Schmitt was hopeful: "We saw a strong line, right at the proper location!" But then, he explains, "we soon learned that life is never as easy as expected... that line had a rather strange appearance and something seemed to be wrong". Indeed, the early investigation showed that this line feature might be attributed to emission by singly ionised titanium atoms ( Ti + or Ti II ), located in a lower atmospheric layer (the 'chromosphere' ) and not in the corona of CN Leo . However, a subsequent, very careful study definitively proved the presence of the hoped-for coronal emission line . The titanium line is produced at lower temperatures than those that reign in the corona, and the individual velocities of the titanium ions are thus much slower than those of the iron ions in the corona. The broadening of the titanium line, introduced by the Doppler effect (the combined lineshifts by all ions), must therefore be much less. The titanium line must accordingly be much more narrow than any coronal line. Many other titanium emission lines are visible in the UVES spectrum, and the common width of these lines can be determined with high accuracy. It turns out to be much less than the observed width of the line seen at 3388 Ångstrom, and that line can therefore not be due to titanium alone. And indeed, when 'subtracting' the contribution from the narrow titanium line, an underlying, much broader line emerges and becomes well visible - cf. PR Photo 24d/01 - it is indeed the coronal emission line from 12 times ionised iron (Fe XIII). This is the first time a stellar coronal line has been unambiguously observed in the optical part of the spectrum. Prospects This KUEYEN/UVES detection of a coronal line closes the historical loop to the discovery of the solar corona as a tenuous, hot envelope around the Sun. It now opens up a new window for the study of stellar coronae and allows thermal emission from these hot regions to be studied from the ground and not only from space, as this was the case until now. Thus, it is now feasible to use the superb capabilities of ground-based instrumentation which has much higher spectral resolving power than currently available X-ray spectrometers. With the new tools at large telescopes like the VLT, the astronomers may embark on detailed studies of the dynamics of stellar coronae. They will then also be able to watch the expected changes in the emission levels of other stars, similar to the well-known 11-year cycle of the Sun. Eventually, they may also obtain images of stellar chromospheres and coronae. More information The research reported in this Press Release is described in a scientific article ("Light from Stellar Coronae: Ground-based Discovery of Emission Lines" by Jürgen Schmitt and Reiner Wichmann ) that appears in the August 2, 2001, issue of the scientific journal "Nature". Jürgen Schmitt has written a popular account on stellar X-ray emission in the German language journal "Sterne und Weltraum" (July 2001, page 544). Note [1]: A report on the observations of the 1869 solar eclipse appeared in the first Nature issue (November 4, 1869) and the interesting story about the identification of the solar coronal lines is described in a popular article ( John Talbot ). A talk by Herbert Friedman about the evolution of X-Ray Astronomy includes a description of the 1949 detection of solar emission in this waveband. More details about the solar-stellar connection and X-rays may be found in the article by Berhard Haisch and Jürgen Schmitt in the October 1999 issue of the journal "Sky & Telescope" (page 46).

Physical Properties and Seasonal Behavior of H2O, HDO, CO2 and Trace Gases on Mars: Quantitative Mapping from Earth-Based Observatories

NASA Technical Reports Server (NTRS)

Novak, Robert E.; Mumma, Michael J.

2011-01-01

Since 1997, we have used high-resolution (R greater than 40000) spectrometers on ground based-telescopes to study molecules that have astrobiological significance in Mars' atmosphere. We have used the NASA-IRTF, Keck II, and VLT telescopes in the 1.0-5.0 micron range. The spectrometer is set at a wavelength to detect specific molecules. Spectral/spatial images are produced. Extracts from these images provide column densities centered at latitude/longitude locations (resolution 400km at sub-Earth point). We have mapped the O2 singlet-Delta emission (a proxy for ozone), HDO, and H2O for seasonal dates throughout the Martian year. Previously undiscovered isotopic bands of CO2 have been identified along with isotopic forms of CO. We are searching for other molecules that have astrobiological importance and have successfully measured methane in Mars' atmosphere.

A Great Moment for Astronomy

NASA Astrophysics Data System (ADS)

1998-05-01

VLT First Light Successfully Achieved The European Southern Observatory announces that First Light has been achieved with the first VLT 8.2-m Unit Telescope at the Paranal Observatory. Scientifically useful images have been obtained as scheduled, on May 25 - 26, 1998. A first analysis of these images convincingly demonstrates the exceptional potential of the ESO Very Large Telescope. Just one month after the installation and provisional adjustment of the optics, the performance of this giant telescope meets or surpasses the design goals, in particular as concerns the achievable image quality. Exposures lasting up to 10 minutes confirm that the tracking, crucial for following the diurnal rotation of the sky, is very accurate and stable. It appears that the concept developed by ESO for the construction of the VLT, namely an actively controlled, single thin mirror, yields a very superior performance. In fact, the angular resolution achieved even at this early stage is unequalled by any large ground-based telescope . The combination of large area and fine angular resolution will ultimately result in a sensitivity for point sources (e.g. stars), which is superior to any yet achieved by existing telescopes on Earth. The present series of images demonstrate these qualities and include some impressive first views with Europe's new giant telescope. After further optimization of the optical, mechanical and electronic systems, and with increasing operational streamlining, this telescope will be able to deliver unique astronomical data of the highest quality. The commissioning and science verification phases of the complex facility including instruments will last until April 1, 1999, at which time the first visiting astronomers will be received. The full significance of this achievement for astronomy will take time to assess. For Europe, this is a triumph of the collaboration between nations, institutions and industries. For the first time in almost a century, European astronomers will have at their disposal the best optical/infrared telescope in the world. We can now look forward with great expectations to the realization of many exciting research projects. The First Light Images Images of various celestial objects were obtained with the VLT CCD Test Camera, some of which are included in a new series, First Astronomical Images from the VLT UT1. None have been subjected to image processing beyond flat-fielding (to remove variations of the digital detector sensitivity over the field) and cosmetic cleaning. They all display the recorded image structure, pixel by pixel. A detailed evaluation with accompanying explanations is presented in the figure captions. 1. Omega Centauri Tracking Tests This 10-minute image demonstrates that the telescope is able to track continuously with a very high precision and thus is able to take full advantage of the frequent, very good atmospheric conditions at Paranal. The images of the stars in this southern globular cluster are very sharp (0.43 arcsec) and are perfectly round, everywhere in the field. 2. The Quadruple Clover Leaf Quasar This 2-minute exposure of the well-known Clover Leaf quasar, a quadruple gravitational lens in which the largest distance between two components is only 1.3 arcsec, was obtained during a period of excellent seeing (0.32 arcsec) measured with a seeing monitor at the top of Paranal. The recorded angular resolution of just 0.38 arcsec demonstrates near-perfect optical quality of the telescope . 3. The Central Area of Globular Cluster M4 This is a colour composite of a field near the centre of the nearest globular cluster. At a seeing of 0.53 arcsec, the blue exposure reaches magnitude B = 24 in only 2 minutes (at signal-to-noise ratio = 5) in a bright sky. A simple extrapolation shows that B ~ 28 would be reached in a 1-hour exposure in a dark sky. The large mirror surface of the VLT UT1 and its ability to produce very sharp images, ensures that faint objects may be observed extremely efficiently. 4. Fine Structure of the Butterfly Nebula This beautiful colour picture is a composite of three exposures through broad-band blue, green and red filters, lasting a total of 25 minutes. It shows the great complexity of this planetary nebula. It also demonstrates the exceptional efficiency with which features of faint surface brightness can be recorded with the VLT . Strong radiation from a dying star in a binary system at the centre impacts on the surrounding material that has been thrown out earlier from the system. 5) High-velocity Ejecta in Eta Carinae This fine picture was obtained during an exposure lasting only 10 seconds. It shows fine structures around this very active object in a detail never before achieved with any ground-based telescope . In the lower insert, a short exposure of the central Homunculus Nebula (seeing 0.38 arcsec) provides a clear view of the three-dimensional structure of this bipolar object. 6. The Dust Band in Centaurus A An amazing amount of faint details is shown in this high-resolution exposure (0.49 arcsec) of the central dust band in the nearby, southern galaxy Centaurus A, obtained through a broad-band red filter and lasting only 10 seconds. The VLT Unit Telescopes will be able to image many other galaxies in similar detail. 7. The Energetic Jet in Messier 87 The First Light took place during the night of May 25 - 26, 1998. Following a short interval of reasonable observing conditions, less optimal atmospheric conditions were encountered. The present photo, a three-colour composite (ultraviolet, blue, green) of the central region of the giant elliptical galaxy Messier 87 in the Virgo Cluster, was obtained during this night. 8. Total Optical Control The 8.2-m main and the 1.1-m secondary mirrors of the VLT Unit Telescopes are completely computer-controlled by means of an Active Optics system. In this way, the shape of the mirror can be optimized very quickly for a given observational purpose. This sequence of 9 images illustrates how the appearance of a stellar image at the focal plane is fully controllable. Fast and thorough optical adjustment ensures the best possible optical quality at all times . 9. Image Quality of the VLT This diagram demonstrates that First Light specifications have been fully met and, more impressively, that the actual VLT performance is sometimes already within the more stringent specifications that were expected to be fulfilled only three years from now. The final steps before "First Light" The final, critical testing phase commenced with the installation of the 8.2-m primary (at that time still uncoated) Zerodur mirror and 1.1-m secondary Beryllium mirror during the second half of April. The optics were then gradually brought into position during carefully planned, successive adjustments. Due to the full integration of an advanced, active control system into the VLT concept, this delicate process went amazingly fast, especially when compared to other ground-based telescopes. It included a number of short test exposures in early May, first with the Guide Camera that is used to steer the telescope. Later, some exposures were made with the Test Camera mounted just below the main mirror at the Cassegrain Focus, in a central space inside the mirror cell. It will continue to be used during the upcoming Commissioning Phase, until the first major instruments (FORS and ISAAC) are attached to the UT1, later in 1998. The 8.2-m mirror was successfully aluminized at the Paranal Mirror Coating facility on May 20 and was reattached to the telescope tube the day thereafter, cf. ESO PR Photos 13a-e/98 and ESO PR Photos 14a-i/98. Further test exposures were then made to check the proper functioning of the telescope mechanics, optics and electronics. This has lead up to the moment of First Light , i.e. the time when the telescope is considered able to produce the first, astronomically useful images. Despite an intervening spell of bad atmospheric conditions, this important event took place during the night of May 25 - 26, 1998, right on the established schedule. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Preliminary results from the Stereo-SCIDAR at the VLT Observatory: extraction of reference atmospheric turbulence profiles for E-ELT adaptive optics instrument performance simulations

NASA Astrophysics Data System (ADS)

Sarazin, Marc S.; Osborn, James; Chacon-Oelckers, Arlette; Dérie, Frédéric J.; Le Louarn, Miska; Milli, Julien; Navarrete, Julio; Wilson, Richard R. W.

2017-09-01

The Stereo-SCIDAR (Scintillation Detection and Ranging) atmospheric turbulence profiler, built for ESO by Durham University, observes the scintillation patterns of binary elements with one of the four VLT-Interferometer 1.8m auxiliary telescopes at the ESO Paranal Observatory. The primary products are the vertical profiles of the index of refraction structure coefficient and of the wind velocity which allow to compute the wavefront coherence time and the isoplanatic angle with a vertical resolution of 250m. The several thousands of profiles collected during more than 30 nights of operation are grouped following criteria based on the altitude distribution or on principal component analysis. A set of reference profiles representative of the site is proposed as input for the various simulation models developed by the E-ELT (European Extremely Large Telescope) instruments Consortia.

Using fear appeals in warning labels to promote responsible gambling among VLT players: the key role of depth of information processing.

PubMed

Munoz, Yaromir; Chebat, Jean-Charles; Suissa, Jacob Amnon

2010-12-01

Video lottery terminals (VLT) are a highly lucrative gambling format, but at the same time they are among the most hazardous. Previous research has shown that threatening warnings may be an appropriate approach for promoting protective behavior. The present study explores the potential benefits of threatening warnings in the fight against compulsive gambling. A 4 × 2 factorial design experiment was used to test our model based on both Elaboration Likelihood Model and Protection Motivation Theory. 258 VLT adult players (58% males, 42% females) with various degrees of problem gambling were exposed to three threat levels (plus a control condition) from two different sources (i.e., either a medical source or a source related to the provider of VLT's). Our results show that both higher threat warnings and the medical source of warnings enhance Depth of Information Processing. It was also found that Depth of Information Processing affects positively attitude change and compliance intentions. The theoretical and managerial implications are discussed.

Europe Agrees on Common Strategy to Initiate Study of LSA/MMA

NASA Astrophysics Data System (ADS)

1998-09-01

Council Specifies ESO's Role in Planning In an extraordinary meeting at the ESO Headquarters, the ESO Council today endorsed ESO's involvement in the planning of a major new astronomical facility in the southern hemisphere. Some years from now, the Large Southern Array/Millimetre Array (LSA/MMA) may become the world's prime sub-mm/mm radio observatory [1] at a pristine site at 5000 m altitude in the Chilean Andes, not very far from the VLT Paranal Observatory. Background One of the highest-priority items in astronomy today is a large millimetre-wavelength array. This would be a millimetre counterpart to the ESO VLT and the NASA/ESA Hubble Space Telescope (HST), with similar scientific objectives and comparable high angular resolution and sensitivity. An antenna array with about 10,000 m 2 area would provide very high sensitivity and angular resolution, compatible with that of the VLT and HST. Such a large collecting area implies an array with many antennas and baselines, which give the added advantage of fast, high-quality images. The site must be high, dry, large, and flat - a high plateau in the Atacama desert is ideal, and has the great advantage of being in the southern hemisphere, important for compatibility with the VLT. Thus, discussions in Europe have focussed on a "Large Southern Array" (LSA) . The scientific case for such a telescope is overwhelming. It would be able to study the origins of galaxies and stars: the epoch of first galaxy formation and the evolution of galaxies at later stages, including the dust-obscured star-forming galaxies that the HST and VLT cannot see, and all phases of star formation hidden away in dusty molecular clouds. But the LSA will go far beyond these main science drivers - it will have a major impact on virtually all areas of astronomy, and make millimetre astronomy accessible to all astronomers. It may well have as big a user community as the VLT itself. European involvement in millimetre astronomy Europe already has a strong involvement in millimetre astronomy: the 5 x 15-m IRAM array on Plateau de Bure (France), the 30-m IRAM antenna (Spain), the 20-m at Onsala (Sweden), the 15-m Swedish-ESO Submillimetre Telescope (SEST, La Silla), the 15-m JCMT (Mauna Kea, Hawaii), the 10-m HHT (Arizona), and others. Over 60 research institutes around Europe use these facilities. Many of them have developed technical expertise and leadership in this area together with European industry, so it is natural that a European collaboration should be looking to the future. The idea of a large European southern millimetre array has been discussed since 1991. In 1995, an LSA Project collaboration was established between ESO, the Institut de Radio Astronomie Millimetrique (IRAM), the Onsala Space Observatory, and the Netherlands Foundation for Research in Astronomy (NFRA). This consortium of observatories agreed to pool resources to study critical technical areas and conduct site surveys in Chile. Details are available in a Messenger article (March 98). Possibilities of intercontinental collaboration An important step was taken in June 1997. A similar project is under study in the United States of America (the "Millimeter Array", MMA ). An agreement was entered into between ESO and the U.S. National Radio Astronomy Observatory (NRAO) to explore the possibility of merging the two projects into one. Until then the emphasis in Europe had been on the large collecting area provided by 16-m antennas operating at purely millimetre wavelengths, while in the U.S. the concept was a smaller array of 8-m antennas with good submillimetre performance. However, as there is also considerable interest in Europe in submillimetre observations, and in the U.S. in a larger collecting area, a compromise seemed feasible. Several joint working groups formed under the ESO-NRAO agreement were set up to explore the possibility of a collaborative project. It was concluded that a homogeneous array of 64 x 12-m antennas, providing submillimetre performance with a total collecting area of 7,000 m 2 , could be built at the high (5000 m) Chajnantor site , an hour from the array control center at the town of San Pedro de Atacama. It is this collaborative facility that is presently referred to as the Large Southern Array/Millimetre Array (LSA/MMA) . The decision by the ESO Council The ESO Council today passed a resolution that emphasizes the great potential of this proposed astronomical facility for scientific discoveries. It will operate in a relatively unexplored waveband region and with imaging and spectral resolution vastly better than anything now available. The ESO Council requests the ESO Executive to develop a proposal for ESO's role in the design and development phase of the new facility to be submitted to Council in its December 1998 meeting. This phase (Phase I) will cover the technical, financial, human resources, scheduling and organizational aspects for the development, construction, commissioning and operation of the LSA/MMA. The ESO Council supports the intention to create a European Coordinating Committee with participation of ESO that will discuss related policy and technical matters. A European Negotiating Team will then be established that will discuss with the U.S. and other interested nations the conditions of the union of the LSA and MMA as a single common enterprise. Note: [1] The corresponding wavelength interval is about 0.3 to 10 mm. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

VizieR Online Data Catalog: The populations of Carina. II. Abundances (Norris+, 2017)

NASA Astrophysics Data System (ADS)

Norris, J. E.; Yong, D.; Venn, K. A.; Gilmore, G.; Casagrande, L.; Dotter, A.

2017-08-01

Our selection of objects is based on unpublished CCD V, I observations that we have made of the Carina galaxy. High-resolution, moderate-S/N spectra were obtained of 39 Carina red giants, during 2007 November-2008 March, with the FLAMES system at the 8.2m Kueyen (VLT/UT2) telescope at Cerro Paranal. The spectra cover the wavelength ranges 4800-5750Å and 5840-6800Å. The resolving power was R=47000. Photometry has been obtained from several sources: P. B. Stetson provided us with homogenized BVI, M. J. Irwin furnished JHK from ESO VISTA survey photometry, and M. Gullieuszik supplied BVIJHKs. (12 data files).

Searching for the signatures of terrestrial planets in F-, G-type main-sequence stars

NASA Astrophysics Data System (ADS)

González Hernández, J. I.; Delgado-Mena, E.; Sousa, S. G.; Israelian, G.; Santos, N. C.; Adibekyan, V. Zh.; Udry, S.

2013-04-01

Context. Detailed chemical abundances of volatile and refractory elements have been discussed in the context of terrestrial-planet formation during in past years. Aims: The HARPS-GTO high-precision planet-search program has provided an extensive database of stellar spectra, which we have inspected in order to select the best-quality spectra available for late type stars. We study the volatile-to-refractory abundance ratios to investigate their possible relation with the low-mass planetary formation. Methods: We present a fully differential chemical abundance analysis using high-quality HARPS and UVES spectra of 61 late F- and early G-type main-sequence stars, where 29 are planet hosts and 32 are stars without detected planets. Results: As for the previous sample of solar analogs, these stars slightly hotter than the Sun also provide very accurate Galactic chemical abundance trends in the metallicity range -0.3 < [Fe/H] < 0.4. Stars with and without planets show similar mean abundance ratios. Moreover, when removing the Galactic chemical evolution effects, these mean abundance ratios, Δ [X/Fe] SUN - STARS, against condensation temperature, tend to exhibit less steep trends with nearly zero or slightly negative slopes. We have also analyzed a subsample of 26 metal-rich stars, 13 with and 13 without known planets, with spectra at S/N ~ 850, on average, in the narrow metallicity range 0.04 < [Fe/H] < 0.19. We find the similar, although not equal, abundance pattern with negative slopes for both samples of stars with and without planets. Using stars at S/N ≥ 550 provides equally steep abundance trends with negative slopes for stars both with and without planets. We revisit the sample of solar analogs to study the abundance patterns of these stars, in particular, 8 stars hosting super-Earth-like planets. Among these stars having very low-mass planets, only four of them reveal clear increasing abundance trends versus condensation temperature. Conclusions: Finally, we compared these observed slopes with those predicted using a simple model that enables us to compute the mass of rocks that have formed terrestrial planets in each planetary system. We do not find any evidence supporting the conclusion that the volatile-to-refractory abundance ratio is related to the presence of rocky planets. Based on observations collected with the HARPS spectrograph at the 3.6-m telescope (072.C-0488(E)), installed at the La Silla Observatory, ESO (Chile), with the UVES spectrograph at the 8-m Very Large Telescope (VLT) - program IDs: 67.C-0206(A), 074.C-0134(A), 075.D-0453(A) -, installed at the Cerro Paranal Observatory, ESO (Chile), and with the UES spectrograph at the 4.2-m William Herschel Telescope (WHT), installed at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, on the island of La Palma.Tables A.1-A.8 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/A6

[Study on Application of NIR Spectral Information Screening in Identification of Maca Origin].

PubMed

Wang, Yuan-zhong; Zhao, Yan-li; Zhang, Ji; Jin, Hang

2016-02-01

Medicinal and edible plant Maca is rich in various nutrients and owns great medicinal value. Based on near infrared diffuse reflectance spectra, 139 Maca samples collected from Peru and Yunnan were used to identify their geographical origins. Multiplication signal correction (MSC) coupled with second derivative (SD) and Norris derivative filter (ND) was employed in spectral pretreatment. Spectrum range (7,500-4,061 cm⁻¹) was chosen by spectrum standard deviation. Combined with principal component analysis-mahalanobis distance (PCA-MD), the appropriate number of principal components was selected as 5. Based on the spectrum range and the number of principal components selected, two abnormal samples were eliminated by modular group iterative singular sample diagnosis method. Then, four methods were used to filter spectral variable information, competitive adaptive reweighted sampling (CARS), monte carlo-uninformative variable elimination (MC-UVE), genetic algorithm (GA) and subwindow permutation analysis (SPA). The spectral variable information filtered was evaluated by model population analysis (MPA). The results showed that RMSECV(SPA) > RMSECV(CARS) > RMSECV(MC-UVE) > RMSECV(GA), were 2. 14, 2. 05, 2. 02, and 1. 98, and the spectral variables were 250, 240, 250 and 70, respectively. According to the spectral variable filtered, partial least squares discriminant analysis (PLS-DA) was used to build the model, with random selection of 97 samples as training set, and the other 40 samples as validation set. The results showed that, R²: GA > MC-UVE > CARS > SPA, RMSEC and RMSEP: GA < MC-UVE < CARS

MUSE alignment onto VLT

NASA Astrophysics Data System (ADS)

Laurent, Florence; Renault, Edgard; Boudon, Didier; Caillier, Patrick; Daguisé, Eric; Dupuy, Christophe; Jarno, Aurélien; Lizon, Jean-Louis; Migniau, Jean-Emmanuel; Nicklas, Harald; Piqueras, Laure

2014-07-01

MUSE (Multi Unit Spectroscopic Explorer) is a second generation Very Large Telescope (VLT) integral field spectrograph developed for the European Southern Observatory (ESO). It combines a 1' x 1' field of view sampled at 0.2 arcsec for its Wide Field Mode (WFM) and a 7.5"x7.5" field of view for its Narrow Field Mode (NFM). Both modes will operate with the improved spatial resolution provided by GALACSI (Ground Atmospheric Layer Adaptive Optics for Spectroscopic Imaging), that will use the VLT deformable secondary mirror and 4 Laser Guide Stars (LGS) foreseen in 2015. MUSE operates in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently commissioning MUSE in the Very Large Telescope for the Preliminary Acceptance in Chile, scheduled for September, 2014. MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile where that was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transported, fully aligned and without any optomechanical dismounting, onto VLT telescope where the first light was overcame the 7th of February, 2014. This paper describes the alignment procedure of the whole MUSE instrument with respect to the Very Large Telescope (VLT). It describes how 6 tons could be move with accuracy better than 0.025mm and less than 0.25 arcmin in order to reach alignment requirements. The success of the MUSE alignment is demonstrated by the excellent results obtained onto MUSE image quality and throughput directly onto the sky.

MUSE field splitter unit: fan-shaped separator for 24 integral field units

NASA Astrophysics Data System (ADS)

Laurent, Florence; Renault, Edgard; Anwand, Heiko; Boudon, Didier; Caillier, Patrick; Kosmalski, Johan; Loupias, Magali; Nicklas, Harald; Seifert, Walter; Salaun, Yves; Xu, Wenli

2014-07-01

MUSE (Multi Unit Spectroscopic Explorer) is a second generation Very Large Telescope (VLT) integral field spectrograph developed for the European Southern Observatory (ESO). It combines a 1' x 1' field of view sampled at 0.2 arcsec for its Wide Field Mode (WFM) and a 7.5"x7.5" field of view for its Narrow Field Mode (NFM). Both modes will operate with the improved spatial resolution provided by GALACSI (Ground Atmospheric Layer Adaptive Optics for Spectroscopic Imaging), that will use the VLT deformable secondary mirror and 4 Laser Guide Stars (LGS) foreseen in 2015. MUSE operates in the visible wavelength range (0.465-0.93 μm). A consortium of seven institutes is currently commissioning MUSE in the Very Large Telescope for the Preliminary Acceptance in Chile, scheduled for September, 2014. MUSE is composed of several subsystems which are under the responsibility of each institute. The Fore Optics derotates and anamorphoses the image at the focal plane. A Splitting and Relay Optics feed the 24 identical Integral Field Units (IFU), that are mounted within a large monolithic instrument mechanical structure. Each IFU incorporates an image slicer, a fully refractive spectrograph with VPH-grating and a detector system connected to a global vacuum and cryogenic system. During 2012 and 2013, all MUSE subsystems were integrated, aligned and tested to the P.I. institute at Lyon. After successful PAE in September 2013, MUSE instrument was shipped to the Very Large Telescope in Chile where it was aligned and tested in ESO integration hall at Paranal. After, MUSE was directly transferred in monolithic way onto VLT telescope where the first light was achieved. This paper describes the MUSE main optical component: the Field Splitter Unit. It splits the VLT image into 24 subfields and provides the first separation of the beam for the 24 Integral Field Units. This talk depicts its manufacturing at Winlight Optics and its alignment into MUSE instrument. The success of the MUSE alignment is demonstrated by the excellent results obtained onto MUSE positioning, image quality and throughput onto the sky. MUSE commissioning at the VLT is planned for September, 2014.

VLT Unit Telescopes Named at Paranal Inauguration

NASA Astrophysics Data System (ADS)

1999-03-01

This has been a busy, but also a very successful and rewarding week for the European Southern Observatory and its staff. While "First Light" was achieved at the second 8.2-m VLT Unit Telescope (UT2) ahead of schedule, UT1 produced its sharpest image so far. This happened at a moment of exceptional observing conditions in the night between March 4 and 5, 1999. During a 6-min exposure of the majestic spiral galaxy, NGC 2997 , stellar images of only 0.25 arcsec FWHM (full-width half-maximum) were recorded. This and two other frames of nearly the same quality have provided the base for the beautiful colour-composite shown above. At this excellent angular resolution, individual star forming regions are well visible along the spiral arms. Of particular interest is the peculiar, twisted shape of the long spiral arm to the right. The Paranal Inauguration The official inauguration of the Paranal Observatory took place in the afternoon of March 5, 1999, in the presence of His Excellency, the President of the Republic of Chile, Don Eduardo Frei Ruiz-Tagle, and ministers of his cabinet, as well the Ambassadors to Chile of the ESO member states and many other distinguished guests. The President of the ESO Council, Mr. Henrik Grage, and the ESO Director General, Professor Riccardo Giacconi, were the foremost representatives of the ESO organisation; most members of the ESO Council and ESO staff also participated. A substantial number of media representatives from Europe and Chile were present and reported - often live - from Paranal during the afternoon and evening. The guests were shown the impressive installations at the new observatory, including the first and second 8.2-m VLT Unit Telescopes; the latter having achieved "First Light" just four days before. A festive ceremony took place in the dome of UT2, under the large telescope structure that had been tilted towards the horizon to make place for the numerous participants. After an introductory address by the ESO Director General, speeches were delivered by the President of the ESO Council and the President of Chile. The speakers praised the great achievement of bringing the very complex, high-technology VLT project this far so successfully and also the wonderful new opportunities for front-line research with this new facility. This would not have been possible without excellent cooperation between the many parties to this project, individuals as well as research institutes, companies and governments, all working towards a common goal. The ceremony was concluded with a discourse on "Understanding the Universe" by Physics Nobel Prize winner, Professor Carlo Rubbia, former Director of CERN. At the end of the day, the President of the ESO Council, the ESO Director General and the Heads of Delegations had the opportunity to witness an observing session with the UT1 from the VLT Control Room. The 300 other guests followed this event via internal video broadcast. Mapuche names for the Unit Telescopes It had long been ESO's intention to provide "real" names to the four VLT Unit Telescopes, to replace the current, somewhat dry and technical designations as UT1 to UT4. Four meaningful names of objects in the sky in the Mapuche language were chosen. This indigeneous people lives mostly in the area south of Santiago de Chile. An essay contest was arranged in this connection among schoolchildren of the Chilean II Region of which Antofagasta is the capital to write about the implications of these names. It drew many excellent entries dealing with the rich cultural heritage of ESO's host country. The jury was unanimous in its choice of the winning essay. This was submitted by 17-year old Jorssy Albanez Castilla from Chuquicamata near the city of Calama. She received the prize, an amateur telescope, during the Paranal Inauguration. Henceforth, the four Unit Telescopes will be known as ANTU (UT1; pronounced an-too ; The Sun), KUEYEN (UT2; qua-yen , like in "quake"; The Moon), MELIPAL (UT3; me-li-pal ; The Southern Cross) and YEPUN (UT4; ye-poon ; Sirius), respectively. An audio sequence with these names pronounced by a native speaker is available below: [RealMedia - Audio only - 164k] "First Light" of UT2 Following the installation of the main mirror in its cell and a 20-hour working session to put the complex secondary mirror and its support in place, the UT2, now Kueyen , achieved (technical) first light in the morning of March 1, 1999, when an image was obtained of a bright star. It showed this telescope to be in good optical shape and further adjustments of the optical and mechanical systems are expected soon to result in some "astronomical" images. The announcement of this important event was made by the ESO Director during the opening session of the VLT Symposium that was held in Antofagasta during March 1-4, 1999. This meeting attracted over 250 scientists from all over world. It provided a most useful opportunity to discuss future scientific programmes with the VLT and other large telescopes. The participants were left with the impression of mounting expectations, just four weeks before the first VLT Unit Telescope, Antu (UT1), will receive the first visiting astronomers. More images from UT1 ESO PR Photo 17c/99 ESO PR Photo 17c/99 [Preview - JPEG: 400 x 667 pix - 332k] [Normal - JPEG: 800 x 1334 pix - 1.3M] [High-Res - JPEG: 2108 x 3450 pix - 2.8M] Caption to PR Photo 17c/99 : This colour composite photo of the Chamaeleon I area is based on six 1-min exposures obtained with VLT UT1 + FORS1 in the V, R and I bands. The sky field measures 6.8 x 11.2 arcmin 2 ; North is up and East is left [1]. Despite the extensive preparations for the Paranal Inguration and the VLT Symposium, excellent progress is being made during the final tuning of Antu (UT1) and its instruments for the "hand-over" to the astronomers on April 1, 1999. This involves exposures in many different modes and of different sky regions. Another impressive photo is shown here that was obtained some nights ago. It displays a sky area near the Chamaeleon I complex of bright nebulae and hot stars in the constellation of the same name, close to the southern celestial pole. Note: [1]: The photos in this Press Release were prepared at Paranal immediately following the Inauguration event and have only been subject to minimal image processing. To reduce the file size, the high-resolution versions carry no identifying text How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

LMC X-1: A New Spectral Analysis of the O-star in the Binary and Surrounding Nebula

NASA Astrophysics Data System (ADS)

Hyde, E. A.; Russell, D. M.; Ritter, A.; Filipović, M. D.; Kaper, L.; Grieve, K.; O'Brien, A. N.

2017-09-01

We provide new observations of the LMC X-1 O star and its extended nebula structure using spectroscopic data from VLT/UVES as well as Hα imaging from the Wide Field Imager on the Max Planck Gesellschaft/European Southern Observatory 2.2 m telescope and ATCA imaging of the 2.1 GHz radio continuum. This nebula is one of the few known to be energized by an X-ray binary. We use a new spectrum extraction technique that is superior to other methods used to obtain both radial velocities and fluxes. This provides an updated spatial velocity of ≃ 21.0 +/- 4.8 km s-1 for the O star. The slit encompasses both the photo-ionized and shock-ionized regions of the nebula. The imaging shows a clear arc-like structure reminiscent of a wind bow shock in between the ionization cone and shock-ionized nebula. The observed structure can be fit well by the parabolic shape of a wind bow shock. If an interpretation of a wind bow shock system is valid, we investigate the N159-O1 star cluster as a potential parent of the system, suggesting a progenitor mass of ˜60 M ⊙ for the black hole. We further note that the radio emission could be non-thermal emission from the wind bow shock, or synchrotron emission associated with the jet-inflated nebula. For both wind- and jet-powered origins, this would represent one of the first radio detections of such a structure.

Detection of molecular hydrogen in a near Solar-metallicity damped Lyman-alpha system at zabs ~ 2 toward Q 0551-366 ≈ 2

NASA Astrophysics Data System (ADS)

Ledoux, C.; Srianand, R.; Petitjean, P.

2002-09-01

We report the detection of H2, C I, C I *, C I ** and Cl I lines in a near Solar-metallicity ([Zn/H]=-0.13) damped Lyman-alpha (DLA) system at zabs=1.962 observed on the line of sight to the quasar Q 0551-366. The iron-peak elements, X=Fe, Cr and Mn are depleted compared to zinc, [X/Zn] ~ -0.8, probably because they are tied up onto dust grains. Among the three detected H2-bearing clouds, spanning 55 km s-1 in velocity space, we derive a total molecular hydrogen column density N(H2)=2.6x 1017 cm-2 and a mean molecular fraction f=2N(H2)/(2N(H2)+N(H I))=1.7x 10-3. The depletion of heavy elements (S, Si, Mg, Mn, Cr, Fe, Ni and Ti) in the central component is similar to that observed in the diffuse neutral gas of the Galactic halo. This depletion is approximately the same in the six C I-detected components independently of the presence or absence of H2. The gas clouds in which H2 is detected always have large densities, nH>30 cm-3, and low temperatures, T01<~ 100 K. This shows that presence of dust, high particle density and/or low temperature is required for molecules to be present. The photo-dissociation rate derived in the components where H2 is detected suggests the existence of a local UV radiation field similar in strength to the one in the Galaxy. Star formation therefore probably occurs near these H2-bearing clouds. Based on observations carried out at the European Southern Observatory (ESO) under prog. ID No. 66.A-0624 with the UVES spectrograph installed at the Very Large Telescope (VLT) on Cerro Paranal, Chile.

How Old is the Milky Way ?

NASA Astrophysics Data System (ADS)

2004-08-01

VLT Observations of Beryllium in Two Old Stars Clock the Beginnings Summary Observations by an international team of astronomers [1] with the UVES spectrometer on ESO's Very Large Telescope at the Paranal Observatory (Chile) have thrown new light on the earliest epoch of the Milky Way galaxy. The first-ever measurement of the Beryllium content in two stars in a globular cluster (NGC 6397) - pushing current astronomical technology towards the limit - has made it possible to study the early phase between the formation of the first generation of stars in the Milky Way and that of this stellar cluster. This time interval was found to amount to 200 - 300 million years. The age of the stars in NGC 6397, as determined by means of stellar evolution models, is 13,400 ± 800 million years. Adding the two time intervals gives the age of the Milky Way, 13,600 ± 800 million years. The currently best estimate of the age of the Universe, as deduced, e.g., from measurements of the Cosmic Microwave Background, is 13,700 million years. The new observations thus indicate that the first generation of stars in the Milky Way galaxy formed soon after the end of the ~200 million-year long "Dark Ages" that succeeded the Big Bang. PR Photo 23a/04: Globular cluster NGC 6397 PR Photo 23b/04: The stars A0228 and A2111 in NGC 6397. PR Photo 23c/04: UVES spectra of the stars A0228 and A2111 in NGC 6397 with Beryllium lines. The age of the Milky Way ESO PR Photo 23a/04 ESO PR Photo 23a/04 Globular Cluster NGC 6397 [Preview - JPEG: 400 x 472 pix - 316k] [Normal - JPEG: 800 x 943 pix - 943k] [Full Res - JPEG: 4000 x 4717 pix - 16.3M] Caption: ESO PR Photo 23a/04 shows the globular cluster NGC 6397, located at a distance of approx. 7,200 light-years in the southern constellation Ara. It has undergone a "core collapse" and the central area is very dense. It contains about 400,000 stars and its age (based on evolutionary models) is 13,400 ± 800 million years. The photo is a composite of exposures in the B- , V- and I-bands obtained in the frame of the Pilot Stellar Survey with the Wide-Field-Imager (WFI) camera at the 2.2-m ESO/MPI telescope at the ESO La Silla Observatory. It was prepared and provided by the ESO Imaging Survey team. The spikes seen at some of the brighter stars are caused by the effect of overexposure (CCD "bleeding"). How old is the Milky Way ? When did the first stars in our galaxy ignite ? A proper understanding of the formation and evolution of the Milky Way system is crucial for our knowledge of the Universe. Nevertheless, the related observations are among the most difficult ones, even with the most powerful telescopes available, as they involve a detailed study of old, remote and mostly faint celestial objects. Globular clusters and the ages of stars Modern astrophysics is capable of measuring the ages of certain stars, that is the time elapsed since they were formed by condensation in huge interstellar clouds of gas and dust. Some stars are very "young" in astronomical terms, just a few million years old like those in the nearby Orion Nebula. The Sun and its planetary system was formed about 4,560 million years ago, but many other stars formed much earlier. Some of the oldest stars in the Milky Way are found in large stellar clusters, in particular in "globular clusters" (PR Photo 23a/04), so called because of their spheroidal shape. Stars belonging to a globular cluster were born together, from the same cloud and at the same time. Since stars of different masses evolve at different rates, it is possible to measure the age of globular clusters with a reasonably good accuracy. The oldest ones are found to be more than 13,000 million years old. Still, those cluster stars were not the first stars to be formed in the Milky Way. We know this, because they contain small amounts of certain chemical elements which must have been synthesized in an earlier generation of massive stars that exploded as supernovae after a short and energetic life. The processed material was deposited in the clouds from which the next generations of stars were made, cf. ESO PR 03/01. Despite intensive searches, it has until now not been possible to find less massive stars of this first generation that might still be shining today. Hence, we do not know when these first stars were formed. For the time being, we can only say that the Milky Way must be older than the oldest globular cluster stars. But how much older? Beryllium to the rescue What astrophysicists would like to have is therefore a method to measure the time interval between the formation of the first stars in the Milky Way (of which many quickly became supernovae) and the moment when the stars in a globular cluster of known age were formed. The sum of this time interval and the age of those stars would then be the age of the Milky Way. New observations with the VLT at ESO's Paranal Observatory have now produced a break-through in this direction. The magic element is "Beryllium"! Beryllium is one of the lightest elements [2] - the nucleus of the most common and stable isotope (Beryllium-9) consists of four protons and five neutrons. Only hydrogen, helium and lithium are lighter. But while those three were produced during the Big Bang, and while most of the heavier elements were produced later in the interior of stars, Beryllium-9 can only be produced by "cosmic spallation". That is, by fragmentation of fast-moving heavier nuclei - originating in the mentioned supernovae explosions and referred to as energetic "galactic cosmic rays" - when they collide with light nuclei (mostly protons and alpha particles, i.e. hydrogen and helium nuclei) in the interstellar medium. Galactic cosmic rays and the Beryllium clock The galactic cosmic rays travelled all over the early Milky Way, guided by the cosmic magnetic field. The resulting production of Beryllium was quite uniform within the galaxy. The amount of Beryllium increased with time and this is why it might act as a "cosmic clock". The longer the time that passed between the formation of the first stars (or, more correctly, their quick demise in supernovae explosions) and the formation of the globular cluster stars, the higher was the Beryllium content in the interstellar medium from which they were formed. Thus, assuming that this Beryllium is preserved in the stellar atmosphere, the more Beryllium is found in such a star, the longer is the time interval between the formation of the first stars and of this star. The Beryllium may therefore provide us with unique and crucial information about the duration of the early stages of the Milky Way. A very difficult observation So far, so good. The theoretical foundations for this dating method were developed during the past three decades and all what is needed is then to measure the Beryllium content in some globular cluster stars. But this is not as simple as it sounds! The main problem is that Beryllium is destroyed at temperatures above a few million degrees. When a star evolves towards the luminous giant phase, violent motion (convection) sets in, the gas in the upper stellar atmosphere gets into contact with the hot interior gas in which all Beryllium has been destroyed and the initial Beryllium content in the stellar atmosphere is thus significantly diluted. To use the Beryllium clock, it is therefore necessary to measure the content of this element in less massive, less evolved stars in the globular cluster. And these so-called "turn-off (TO) stars" are intrinsically faint. In fact, the technical problem to overcome is three-fold: First, all globular clusters are quite far away and as the stars to be measured are intrinsically faint, they appear quite faint in the sky. Even in NGC6397, the second closest globular cluster, the TO stars have a visual magnitude of ~16, or 10000 times fainter than the faintest star visible to the unaided eye. Secondly, there are only two Beryllium signatures (spectral lines) visible in the stellar spectrum and as these old stars do contain comparatively little Beryllium, those lines are very weak, especially when compared to neighbouring spectral lines from other elements. And third, the two Beryllium lines are situated in a little explored spectral region at wavelength 313 nm, i.e., in the ultraviolet part of the spectrum that is strongly affected by absorption in the terrestrial atmosphere near the cut-off at 300 nm, below which observations from the ground are no longer possible. It is thus no wonder that such observations had never been made before, the technical difficulties were simply unsurmountable. VLT and UVES do the job ESO PR Photo 23b/04 ESO PR Photo 23b/04 Stars A0228 and A2111 in NGC 6397 [Preview - JPEG: 580 x 400 pix - 143k] [Normal - JPEG: 1160 x 800 pix - 33k] ESO PR Photo 23c/04 ESO PR Photo 23c/04 UVES spectra of the stars A0228 and A2111 in Globular Cluster NGC 6397 [Preview - JPEG: 400 x 468 pix - 115k] [Normal - JPEG: 800 x 925 pix - 272k] Captions: ESO PR Photo 23b/04 identifies the two stars in the globular cluster NGC 6397 for which spectra were obtained with the UVES spectrometer on the VLT (at the centre of the fields shown). The photos have been extracted from PR Photo 23a/04 by the Wide-Field-Imager (WFI) camera at the 2.2-m ESO/MPI telescope at the ESO La Silla Observatory. ESO PR Photo 23c/04 is a reproduction of a small wavelength region of the spectra obtained with the UVES spectrometer at the 8.2-m Kueyen telescope at Paranal of these stars (above), together with that of another nearby star, HD 218502, a field star in which the Beryllium lines are also visible (below). This star, however, is not a member of a cluster and its age is not well known. The achieved signal-to-noise ratios are indicated. The best-fitting synthetic spectra are show as red dots; in the spectrum of A2111, the blue dashed lines illustrate the accuracy of the fit - they correspond to a variation of the Beryllium content by approx. ± 50% (0.2 dex). Using the high-performance UVES spectrometer on the 8.2-m Kuyen telescope of ESO's Very Large Telescope at the Paranal Observatory (Chile) which is particularly sensitive to ultraviolet light, a team of ESO and Italian astronomers [1] succeeded in obtaining the first reliable measurements of the Beryllium content in two TO-stars (denoted "A0228" and "A2111") in the globular cluster NGC 6397 (PR Photo 23b/04). Located at a distance of about 7,200 light-years in the direction of a rich stellar field in the southern constellation Ara, it is one of the two nearest stellar clusters of this type; the other is Messier 4. The observations were done during several nights in the course of 2003. Totalling more than 10 hours of exposure on each of the 16th-magnitude stars, they pushed the VLT and UVES towards the technical limit. Reflecting on the technological progress, the leader of the team, ESO-astronomer Luca Pasquini, is elated: "Just a few years ago, any observation like this would have been impossible and just remained an astronomer's dream!" The resulting spectra (PR Photo 23c/04) of the faint stars show the weak signatures of Beryllium ions (Be II). Comparing the observed spectrum with a series of synthetic spectra with different Beryllium content (in astrophysics: "abundance") allowed the astronomers to find the best fit and thus to measure the very small amount of Beryllium in these stars: for each Beryllium atom there are about 2,224,000,000,000 hydrogen atoms. Beryllium lines are also seen in another star of the same type as these stars, HD 218052, cf. PR Photo 23c/04. However, it is not a member of a cluster and its age is by far not as well known as that of the cluster stars. Its Beryllium content is quite similar to that of the cluster stars, indicating that this field star was born at about the same time as the cluster. From the Big Bang until now According to the best current spallation theories, the measured amount of Beryllium must have accumulated in the course of 200 - 300 million years. Italian astronomer Daniele Galli, another member of the team, does the calculation: "So now we know that the age of the Milky Way is this much more than the age of that globular cluster - our galaxy must therefore be 13,600 ± 800 million years old. This is the first time we have obtained an independent determination of this fundamental value!". Within the given uncertainties, this number also fits very well with the current estimate of the age of the Universe, 13,700 million years, that is the time elapsed since the Big Bang. It thus appears that the first generation of stars in the Milky Way galaxy was formed at about the time the "Dark Ages" ended, now believed to be some 200 million years after the Big Bang. It would seem that the system in which we live may indeed be one of the "founding" members of the galaxy population in the Universe. More information The research presented in this press release is discussed in a paper entitled "Be in turn-off stars of NGC 6397: early Galaxy spallation, cosmochronology and cluster formation" by L. Pasquini and co-authors that will be published in the European research journal "Astronomy & Astrophysics" (astro-ph/0407524). Notes [1] The team is composed of Luca Pasquini (ESO), Piercarlo Bonifacio (INAF-Osservatorio di Trieste, Italy), Sofia Randich and Daniele Galli (INAF-Osservatorio di Arcetri, Firenze, Italy), and Raffaele G. Gratton (INAF-Osservatorio di Padova, Italy). [2] Interestingly, the secondary mirrors of the four VLT Unit Telescopes are made of Beryllium in order to make them as light as possible while retaining the necessary stiffness. Each of the four mirrors measures 1.1 metres across and weighs about 50 kilograms.

Evolution of the VLT instrument control system toward industry standards

NASA Astrophysics Data System (ADS)

Kiekebusch, Mario J.; Chiozzi, Gianluca; Knudstrup, Jens; Popovic, Dan; Zins, Gerard

2010-07-01

The VLT control system is a large distributed system consisting of Linux Workstations providing the high level coordination and interfaces to the users, and VME-based Local Control Units (LCU's) running the VxWorks real-time operating system with commercial and proprietary boards acting as the interface to the instrument functions. After more than 10 years of VLT operations, some of the applied technologies used by the astronomical instruments are being discontinued making it difficult to find adequate hardware for future projects. In order to deal with this obsolescence, the VLT Instrumentation Framework is being extended to adopt well established Commercial Off The Shelf (COTS) components connected through industry standard fieldbuses. This ensures a flexible state of the art hardware configuration for the next generation VLT instruments allowing the access to instrument devices via more compact and simpler control units like PC-based Programmable Logical Controllers (PLC's). It also makes it possible to control devices directly from the Instrument Workstation through a normal Ethernet connection. This paper outlines the requirements that motivated this work, as well as the architecture and the design of the framework extension. In addition, it describes the preliminary results on a use case which is a VLTI visitor instrument used as a pilot project to validate the concepts and the suitability of some COTS products like a PC-based PLCs, EtherCAT8 and OPC UA6 as solutions for instrument control.

The UVES Large Program for testing fundamental physics I. Bounds on a change in α towards quasar HE 2217-2818

NASA Astrophysics Data System (ADS)

Molaro, P.; Centurión, M.; Whitmore, J. B.; Evans, T. M.; Murphy, M. T.; Agafonova, I. I.; Bonifacio, P.; D'Odorico, S.; Levshakov, S. A.; Lopez, S.; Martins, C. J. A. P.; Petitjean, P.; Rahmani, H.; Reimers, D.; Srianand, R.; Vladilo, G.; Wendt, M.

2013-07-01

Context. Absorption-line systems detected in quasar spectra can be used to compare the value of the fine-structure constant, α, measured today on Earth with its value in distant galaxies. In recent years, some evidence has emerged of small temporal and also spatial variations in α on cosmological scales. These variations may reach a fractional level of ≈ 10 ppm (parts per million). Aims: To test these claims we are conducting a Large Program of observations with the Very Large Telescope's Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high-resolution (R ≈ 60 000) and high signal-to-noise ratio (S/N ≈ 100) UVES spectra calibrated specifically for this purpose. Here we analyse the first complete quasar spectrum from this programme, that of HE 2217-2818. Methods: We applied the many multiplet method to measure α in five absorption systems towards this quasar: zabs = 0.7866, 0.9424, 1.5558, 1.6279 , and 1.6919. Results: The most precise result is obtained for the absorber at zabs = 1.6919 where 3 Fe ii transitions and Al ii λ1670 have high S/N and provide a wide range of sensitivities to α. The absorption profile is complex with several very narrow features, and it requires 32 velocity components to be fitted to the data. We also conducted a range of tests to estimate the systematic error budget. Our final result for the relative variation in α in this system is Δα/α = +1.3 ± 2.4stat ± 1.0sys ppm. This is one of the tightest current bounds on α-variation from an individual absorber. A second, separate approach to the data reduction, calibration, and analysis of this system yielded a slightly different result of -3.8 ppm, possibly suggesting a larger systematic error component than our tests indicated. This approach used an additional 3 Fe ii transitions, parts of which were masked due to contamination by telluric features. Restricting this analysis to the Fe ii transitions alone and using a modified absorption profile model gave a result that is consistent with the first approach, Δα/α = +1.1 ± 2.6stat ppm. The four other absorbers have simpler absorption profiles, with fewer and broader features, and offer transitions with a narrower range of sensitivities to α. They therefore provide looser bounds on Δα/α at the ≳10 ppm precision level. Conclusions: The absorbers towards quasar HE 2217-2818 reveal no evidence of any variation in α at the 3-ppm precision level (1σ confidence). If the recently reported 10-ppm dipolar variation in α across the sky is correct, the expectation at this sky position is (3.2-5.4) ± 1.7 ppm depending on dipole model used. Our constraint of Δα/α = +1.3 ± 2.4stat ± 1.0sys ppm is not inconsistent with this expectation. Based on observations taken at ESO Paranal Observatory. Program L 185.A-0745Tables 4-8 are available in electronic form at http://www.aanda.org

Associations of cumulative sun exposure and phenotypic characteristics with histologic solar elastosis

PubMed Central

Thomas, Nancy E.; Kricker, Anne; From, Lynn; Busam, Klaus; Millikan, Robert C.; Ritchey, Mary E.; Armstrong, Bruce K.; Lee-Taylor, Julia; Marrett, Loraine D.; Anton-Culver, Hoda; Zanetti, Roberto; Rosso, Stefano; Gallagher, Richard P.; Dwyer, Terence; Goumas, Chris; Kanetsky, Peter A.; Begg, Colin B.; Orlow, Irene; Wilcox, Homer; Paine, Susan; Berwick, Marianne

2010-01-01

Background Solar elastosis adjacent to melanomas in histologic sections is regarded as an indicator of sun exposure although the associations of ultraviolet (UV) exposure and phenotype with solar elastosis are yet to be fully explored. Methods The study included 2,589 incident primary melanoma patients with assessment of histologic solar elastosis in the population-based Genes, Environment, and Melanoma study. Ambient erythemal UV (UVE) at places of residence and sun exposure hours, including body site-specific exposure, were collected. We examined the association of cumulative site-specific and non site-specific sun exposure hours and ambient UVE with solar elastosis in multivariable models adjusted for age, sex, center, pigmentary characteristics, nevi and, where relevant, body site. Results Solar elastosis was associated most strongly with site-specific UVE (OR for top exposure quartile, 5.20; 95% CI, 3.40-7.96; P for trend <0.001) and also with site-specific sun exposure (OR for top quartile, 5.12; 95% CI, 3.35-7.83; P for trend <0.001). Older age (OR at >70 years, 7.69; 95% CI, 5.14-11.52); P trend < 0.001) and having more than 10 back nevi (OR, 0.77; 95% CI, 0.61-0.97; P = 0.03) were independently associated with solar elastosis. Conclusion Solar elastosis had a strong association with higher site-specific UVE dose, older age and fewer nevi. Impact Solar elastosis could be a useful biomarker of lifetime site-specific UV. Future research is needed to explore whether age represents more than simple accumulation of sun exposure and the reason that people with more nevi may be less prone to solar elastosis. PMID:20802019

Associations of cumulative sun exposure and phenotypic characteristics with histologic solar elastosis.

PubMed

Thomas, Nancy E; Kricker, Anne; From, Lynn; Busam, Klaus; Millikan, Robert C; Ritchey, Mary E; Armstrong, Bruce K; Lee-Taylor, Julia; Marrett, Loraine D; Anton-Culver, Hoda; Zanetti, Roberto; Rosso, Stefano; Gallagher, Richard P; Dwyer, Terence; Goumas, Chris; Kanetsky, Peter A; Begg, Colin B; Orlow, Irene; Wilcox, Homer; Paine, Susan; Berwick, Marianne

2010-11-01

Solar elastosis adjacent to melanomas in histologic sections is regarded as an indicator of sun exposure, although the associations of UV exposure and phenotype with solar elastosis are yet to be fully explored. The study included 2,589 incident primary melanoma patients with assessment of histologic solar elastosis in the population-based Genes, Environment, and Melanoma study. Ambient erythemal UV (UVE) at places of residence and sun exposure hours, including body site-specific exposure, were collected. We examined the association of cumulative site-specific and non-site-specific sun exposure hours and ambient UVE with solar elastosis in multivariable models adjusted for age, sex, center, pigmentary characteristics, nevi, and, where relevant, body site. Solar elastosis was associated most strongly with site-specific UVE [odds ratio (OR) for top exposure quartile, 5.20; 95% confidence interval (95% CI), 3.40-7.96; P for trend <0.001] and also with site-specific sun exposure (OR for top quartile, 5.12; 95% CI, 3.35-7.83; P for trend <0.001). Older age (OR at >70 years, 7.69; 95% CI, 5.14-11.52; P for trend < 0.001) and having more than 10 back nevi (OR, 0.77; 95% CI, 0.61-0.97; P = 0.03) were independently associated with solar elastosis. Solar elastosis had a strong association with higher site-specific UVE dose, older age, and fewer nevi. Solar elastosis could be a useful biomarker of lifetime site-specific UV. Future research is needed to explore whether age represents more than simple accumulation of sun exposure and to determine why people with more nevi may be less prone to solar elastosis. ©2010 AACR.

3D shape of asteroid (6) Hebe from VLT/SPHERE imaging: Implications for the origin of ordinary H chondrites

NASA Astrophysics Data System (ADS)

Marsset, M.; Carry, B.; Dumas, C.; Hanuš, J.; Viikinkoski, M.; Vernazza, P.; Müller, T. G.; Delbo, M.; Jehin, E.; Gillon, M.; Grice, J.; Yang, B.; Fusco, T.; Berthier, J.; Sonnett, S.; Kugel, F.; Caron, J.; Behrend, R.

2017-08-01

Context. The high-angular-resolution capability of the new-generation ground-based adaptive-optics camera SPHERE at ESO VLT allows us to assess, for the very first time, the cratering record of medium-sized (D 100-200 km) asteroids from the ground, opening the prospect of a new era of investigation of the asteroid belt's collisional history. Aims: We investigate here the collisional history of asteroid (6) Hebe and challenge the idea that Hebe may be the parent body of ordinary H chondrites, the most common type of meteorites found on Earth ( 34% of the falls). Methods: We observed Hebe with SPHERE as part of the science verification of the instrument. Combined with earlier adaptive-optics images and optical light curves, we model the spin and three-dimensional (3D) shape of Hebe and check the consistency of the derived model against available stellar occultations and thermal measurements. Results: Our 3D shape model fits the images with sub-pixel residuals and the light curves to 0.02 mag. The rotation period (7.274 47 h), spin (ECJ2000 λ, β of 343°, +47°), and volume-equivalent diameter (193 ± 6 km) are consistent with previous determinations and thermophysical modeling. Hebe's inferred density is 3.48 ± 0.64 g cm-3, in agreement with an intact interior based on its H-chondrite composition. Using the 3D shape model to derive the volume of the largest depression (likely impact crater), it appears that the latter is significantly smaller than the total volume of close-by S-type H-chondrite-like asteroid families. Conclusions: Our results imply that (6) Hebe is not the most likely source of H chondrites. Over the coming years, our team will collect similar high-precision shape measurements with VLT/SPHERE for 40 asteroids covering the main compositional classes, thus providing an unprecedented dataset to investigate the origin and collisional evolution of the asteroid belt. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme ID 60.A-9379 and 086.C-0785.

Why is the VLT Very Efficient?

NASA Astrophysics Data System (ADS)

Comerón, F.

2009-09-01

The operations model of the ESO Very Large Telescope (VLT) heavily relies on a full-scale implementation of Service Mode observing. In this contribution we review the main features of ESO's approach to Service Mode at the VLT, we outline the advantages offered by this mode, and the challenges faced when implementing it given the wide diversity of instrumentation and instrument modes currently available at the VLT and the VLT Interferometer (VLTI). We give special emphasis to the part of this challenge directly derived from the evolution of the atmospheric conditions, which drive the short-term scheduling of the different scientific programmes competing for the available time.

VLT adaptive optics search for luminous substructures in the lens galaxy towards SDSS J0924+0219

NASA Astrophysics Data System (ADS)

Faure, C.; Sluse, D.; Cantale, N.; Tewes, M.; Courbin, F.; Durrer, P.; Meylan, G.

2011-12-01

The anomalous flux ratios between quasar images are suspected of being caused by substructures in lens galaxies. We present new deep and high-resolution H and Ks imaging of the strongly lensed quasar SDSS J0924+0219 obtained using the ESO VLT with adaptive optics and the laser guide star system. SDSS J0924+0219 is particularly interesting because the observed flux ratio between the quasar images vastly disagree with the predictions from smooth mass models. With our adaptive optics observations we find a luminous object, Object L, located ~0.3'' to the north of the lens galaxy, but we show that it cannot be responsible for the anomalous flux ratios. Object L as well as a luminous extension of the lens galaxy to the south are seen in the archival HST/ACS image in the F814W filter. This suggests that Object L is part of a bar in the lens galaxy, as also supported by the presence of a significant disk component in the light profile of the lens galaxy. Finally, we find no evidence of any other luminous substructure that may explain the quasar images flux ratios. However, owing to the persistence of the flux ratio anomaly over time (~7 years), a combination of microlensing and millilensing is the favorite explanation for the observations. Based on observations obtained with the ESO VLT at Paranal observatory (Prog ID 084.A-0762(A); PI: Meylan). Also based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with the CASTLES (Cfa-Arizona Space Telescope LEns Survey) survey (ID: 9744, PI: C. S. Kochanek).

VizieR Online Data Catalog: HeI 5876 & 10830Å EWs of solar-type stars (Andretta+, 2017)

NASA Astrophysics Data System (ADS)

Andretta, V.; Giampapa, M. S.; Covino, E.; Reiners, A.; Beeck, B.

2017-11-01

A total of 134 FEROS spectra (R=48000) of our targets (including telluric standards) were acquired on the night of UT 2011 December 6-7; spectral coverage from 3500 to 9200Å. The Fiber Extended-range Optical Spectrograph (FEROS) was mounted at the 2.2m Max-Planck Gesellschaft/European Southern Observatory (MPG/ESO) telescope at La Silla (Chile). The HeIλ10830 spectroscopic observations were carried out on the same night as the FEROS D3 observations, using the CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES), mounted at Unit Telescope 1 (Antu) of the VLT array at Cerro Paranal. The details of the observations is given in table 1. (3 data files).

Ashes from the Elder Brethren

NASA Astrophysics Data System (ADS)

2001-03-01

UVES Observes Stellar Abundance Anomalies in Globular Clusters Summary Globular clusters are very massive assemblies of stars. More than 100 are known in the Milky Way galaxy and most of them harbour several million stars. They are very dense - at their centers, the typical distance between individual stars is comparable to the size of the Solar System, or 100 to 1000 times closer than the corresponding distances between stars in the solar neighborhood. Globular clusters are among the oldest objects known , with estimated ages of 11 to 15 billion years [1]. All stars in a globular cluster were formed at nearly the same moment, and from the same parent cloud of gas and dust. The original chemical composition of all stars is therefore the same. But now, an international group of astronomers [2], working with the UVES Spectrograph at the ESO Very Large Telescope (VLT) , have obtained some unexpected results during a detailed analysis of dwarf stars in some globular clusters . Such stars have about the same mass as our Sun and like it, they evolve very slowly. Thus they still ought to have about the same abundances of most chemical elements. Nevertheless, the astronomers found large abundance variations from star to star, especially for the common elements Oxygen, Sodium, Magnesium and Aluminium . This phenomenon has never been seen in such stars before . It appears that those stars must somehow have received "burnt" stellar material from more massive stars that died many billion years ago. In their final phase - as "planetary nebulae" - they eject stellar material that has been enriched with certain chemical elements which were produced by the nuclear processes in their interiors during their active life. Such an acquisition of material from other stars has been proposed but has never before been seen in globular clusters . This new discovery obviously sets stars in globular cluster apart from those in less dense environments, like the solar neighbourhood. PR Photo 06a/01 : The globular cluster NGC 6752 . PR Photo 06b/01 : Spectra of dwarf stars in NGC 6752 Globular clusters ESO PR Photo 06a/01 ESO PR Photo 06a/01 [Preview - JPEG: 400 x 467 pix - 136k] [Normal - JPEG: 800 x 934 pix - 424k] [Hires - JPEG: 3000 x 3503 pix - 3.0M] Caption : PR Photo 06a/01 is an image of the globular cluster NGC 6752 ; stars for which spectra were obtained in the present programme are marked by small circles (only visible in the high-resolution version of this photo). NGC 6752 is a typical globular cluster, containing many hundreds of thousands of stars, of which some tens of thousands are visible in this photo. It is located at a distance of approximately 13,000 light-years and is one of the oldest known objects in the Universe. The bright, round object to the lower right of the cluster is the overexposed image of the 7th magnitude star HD 177999 . Technical information about this photo is available below. Globular clusters are very massive and extremely dense agglomerates of stars: typical distances between stars at their centres are comparable to the size of the Solar System. They were formed very early in the Universe and have very low metal content, down to about 1/200 of the Solar abundance. They are among the oldest objects for which relatively accurate ages can be determined for individual stars by means of their observed colours (for information about the "radioactive" method, see ESO Press Release 02/01. The study of globular clusters therefore plays a basic role in our understanding of the evolution of the Universe and of our own Galaxy. The globular clusters are quite distant and most are located in the Milky Way halo, far above or below the main plane of this galaxy. The nearest globular cluster is Messier 4 (NGC 6121) , about 7,000 light-years away. The globular cluster NGC 6752 , shown in PR Photo 06a/01 , is a typical representative of this class of celestial objects. Its distance is estimated at 13,000 light-years Spectral analysis supports distance and age determinations The vast majority of stars in globular clusters are "dwarfs" like our own Sun. They burn Hydrogen into Helium in their central regions, and like the Sun they spend billions of years in this particular evolutionary phase. When their light is dispersed with a spectrograph , thousands of narrow spectral lines are revealed that are caused by chemical elements like Iron, Sodium, Oxygen, Magnesium and Lithium, present in the outer atmospheres of these stars. "Spectral analysis" is one of the basic tools of astronomy, during which the accurate chemical composition of a star is determined by means of a detailed study of the lines seen in its spectrum. In this context, very detailed observations of dwarf stars in globular clusters are of great importance. They allow to compare directly the properties of stars in distant clusters with those of much closer - and hence more easily observable - similar stars in the solar neighbourhood. Such a comparison contributes to reducing current uncertainties in the determination of distances and ages of the globular clusters. Studies like these will ultimately yield a better determination of the age of our own Galaxy and the Universe, as well as the universal distance scale. Variations in chemical abundances ESO PR Photo 06b/01 ESO PR Photo 06b/01 [Preview - JPEG: 400 x 457 pix - 96k] [Normal - JPEG: 800 x 914 pix - 264k] Caption : PR Photo 06b/01 displays a series of spectra of dwarf stars in the globular cluster NGC 6752 , obtained with the UVES high-dispersion spectrograph at the 8.2-m VLT KUEYEN telescope. Sodium (Na) and Oxygen (O) lines are marked, and the spectra are arranged according to the strength of the Sodium lines, with the strongest at the top. It is obvious that stars with stronger Sodium lines (and therefore with a higher Sodium abundance) have weaker Oxygen lines (and are therefore poorer in Oxygen). Even with UVES, the most powerful high-resolution astronomical spectrograph in the world, exposures of up to 4.5 hours were required to record good spectra of these faint objects (V-mag = 17.2). Detailed observations of dwarf stars in globular clusters are rather difficult because they are quite faint objects; The brightest are at least 10,000 times fainter than the dimmest stars observable with the unaided eye. Nevertheless, the closest globular clusters are seen in the southern sky and with the high efficiency of the UVES spectrograph mounted at the KUEYEN 8.2-m telescope at Paranal (Chile), it has now become possible for the first time to obtain excellent spectra for a significant number of dwarf stars in globular clusters, cf. PR Photo 06b/01 . The UVES spectra cover a wide wavelength interval (350 - 900 nm) and display a very large number of spectral lines that originate from many different elements. The first results obtained from the excellent data for this observational programme immediately brought a great surprise to Raffaele Gratton and his co-investigators. The Italian astronomer reports that "our detailed analysis revealed that, while heavy elements like Iron display an impressively similar abundance in all of the observed dwarf stars, other elements, such as Oxygen, Sodium, Magnesium and Aluminium show large abundance variations from star to star". Moreover, "these variations are apparently not completely random, as there is evidence that certain elements change in a similar pattern from star to star". Evidence for accretion? This result is indeed unexpected, since the dwarf stars in globular clusters originated from the same interstellar material. Which effect may therefore produce the observed variations ? And why are such variations not observed in dwarf stars in the solar neighborhood ? The scientists think they have the answer. It has been known since the early 1970's that large star-to-star variations in the abundances of light elements like Carbon, Nitrogen, Oxygen, Sodium, Magnesium and Aluminium may occur in giant stars . Contrary to dwarf stars that still burn Hydrogen at their centres into Helium, giant stars have exhausted their Hydrogen supplies and have become much more luminous. Most investigators attributed the observed variations to the fact that in giant stars a certain amount of "mixing" occurs between the upper atmospheric layers (that emit the light we see) and the deeper (warmer) layers, in which some nuclear burning is going on, transforming Carbon into Nitrogen, etc. However, it is a well established fact of stellar evolution theory that such mixing and, consequently, the presence of abundance anomalies in the upper atmosphere can only occur in bright, evolved giant stars. It does not happen in dwarf stars, because the central temperature of those objects is not high enough to burn Oxygen or Magnesium, and to produce Sodium and Aluminium. It seems therefore not possible that the abundance anomalies are produced in those stars where they are observed. They should have been produced elsewhere, and transported in some way to the surface layers of the stars where we observe them [3]. ESO astronomer Luca Pasquini from the team explains that "we therefore believe that these observations provide evidence that a certain fraction of stars in some globular cluster has received "burnt" material from more massive stars." He adds that "the stars of that elder generation ended their active lifetimes a long time ago by ejecting their material into surrounding space during a "planetary nebula" phase and have now become very dim "white dwarf stars" [4]. The acquisition of material from other stars is a phenomenon that is apparently unique to globular clusters (except that it has also been observed in a few close binary stars). It clearly distinguishes stars in globular cluster from those found in less dense environments, like the solar neighborhood. More information The research paper ("The O-Na and Mg-Al Anticorrelations in Turn-Off and early Subgiants in Globular Clusters") on which this Press Release is based is now in press in the European journal Astronomy & Astrophysics. It is also available on the web as astro-ph/0012457. Notes [1]: 1 billion = 1,000 million. [2]: The team members in the ESO Large Program 165-L0263 devoted to the analysis of globular cluster dwarf stars, described in this Press Release, are: Raffaele Gratton (PI), Eugenio Carretta , Riccardo Claudi , Silvano Desidera , Sara Lucatello (Osservatorio Astronomico di Padova, Italy), Gisella Clementini , Angela Bragaglia (Osservatorio Astronomico di Bologna, Italy), Paolo Molaro , Piercarlo Bonifacio , Miriam Centurion (Osservatorio Astronomico di Trieste, Italy), Francesca D' Antona (Osservatorio Astronomico di Roma, Italy), Vittorio Castellani (Universita' di Pisa, Italy), Alessandro Chieffi (CNR-IAS, Italy), Oscar Straniero (Osservatorio di Teramo, Italy), Luca Pasquini , Patrick Francois (ESO), Francois Spite , Monique Spite (Observatoire de Meudon, France), Chris Sneden (University of Texas at Austin, USA), Frank Grundahl (University of Aarhus, Denmark). [3]: While it is apparent that some mass is transferred from the Planetary Nebulae to the stars, the details of this process are not clear. It may have happened before the stars here observed were formed, or later. In the latter case, the accretion may have occurred only during a particular evolutionary phase, some 100 million years after the cluster formed, i.e. about 11 to 15 billion years ago, and in very dense environments. Moreover, the accretion rate will depend on the relative velocities: only stars that move slowly with respect to the interstellar medium has a good chance of accreting matter. This may also be (part of) an explanation of the observed, large differences from star to star. [4]: A photo of a large planetary nebula is available as PR Photo 38a/98 and information about VLT observations of white dwarf stars in globular clusters are described in PR 20/99. Technical information about the photo PR Photo 06a/01 The image has been obtained through a v-band filter with the DFOSC multi-mode instrument the Danish 1.5-m Telescope at the ESO La Silla Observatory (Chile). The diameter of the field-of-view is 9 arcmin; the exposure time was 10 min, and the seeing was 1.3 arcsec. A few CCD columns suffer from imaging defects.

Nondestructive determination of the modulus of elasticity of Fraxinus mandschurica using near-infrared spectroscopy

NASA Astrophysics Data System (ADS)

Yu, Huiling; Liang, Hao; Lin, Xue; Zhang, Yizhuo

2018-04-01

A nondestructive methodology is proposed to determine the modulus of elasticity (MOE) of Fraxinus mandschurica samples by using near-infrared (NIR) spectroscopy. The test data consisted of 150 NIR absorption spectra of the wood samples obtained using an NIR spectrometer, with the wavelength range of 900 to 1900 nm. To eliminate the high-frequency noise and the systematic variations on the baseline, Savitzky-Golay convolution combined with standard normal variate and detrending transformation was applied as data pretreated methods. The uninformative variable elimination (UVE), improved by the evolutionary Monte Carlo (EMC) algorithm and successive projections algorithm (SPA) selected three characteristic variables from full 117 variables. The predictive ability of the models was evaluated concerning the root-mean-square error of prediction (RMSEP) and coefficient of determination (Rp2) in the prediction set. In comparison with the predicted results of all the models established in the experiments, UVE-EMC-SPA-LS-SVM presented the best results with the smallest RMSEP of 0.652 and the highest Rp2 of 0.887. Thus, it is feasible to determine the MOE of F. mandschurica using NIR spectroscopy accurately.

The Most Remote Gamma-Ray Burst

NASA Astrophysics Data System (ADS)

2000-10-01

ESO Telescopes Observe "Lightning" in the Young Universe Summary Observations with telescopes at the ESO La Silla and Paranal observatories (Chile) have enabled an international team of astronomers [1] to measure the distance of a "gamma-ray burst", an extremely violent, cosmic explosion of still unknown physical origin. It turns out to be the most remote gamma-ray burst ever observed . The exceedingly powerful flash of light from this event was emitted when the Universe was very young, less than about 1,500 million years old, or only 10% of its present age. Travelling with the speed of light (300,000 km/sec) during 11,000 million years or more, the signal finally reached the Earth on January 31, 2000. The brightness of the exploding object was enormous, at least 1,000,000,000,000 times that of our Sun, or thousands of times that of the explosion of a single, heavy star (a "supernova"). The ESO Very Large Telescope (VLT) was also involved in trail-blazing observations of another gamma-ray burst in May 1999, cf. ESO PR 08/99. PR Photo 28a/00 : Sky field near GRB 000131 . PR Photo 28b/00 : The fading optical counterpart of GRB 000131 . PR Photo 28c/00 : VLT spectrum of GRB 000131 . What are Gamma-Ray Bursts? One of the currently most active fields of astrophysics is the study of the mysterious events known as "gamma-ray bursts" . They were first detected in the late 1960's by instruments on orbiting satellites. These short flashes of energetic gamma-rays last from less than a second to several minutes. Despite much effort, it is only within the last few years that it has become possible to locate the sites of some of these events (e.g. with the Beppo-Sax satellite ). Since the beginning of 1997, astronomers have identified about twenty optical sources in the sky that are associated with gamma-ray bursts. They have been found to be situated at extremely large (i.e., "cosmological") distances. This implies that the energy release during a gamma-ray burst within a few seconds is larger than that of the Sun during its entire life time (about 10,000 million years). "Gamma-ray bursts" are in fact by far the most powerful events since the Big Bang that are known in the Universe. While there are indications that gamma-ray bursts originate in star-forming regions within distant galaxies, the nature of such explosions remains a puzzle. Recent observations with large telescopes, e.g. the measurement of the degree of polarization of light from a gamma-ray burst in May 1999 with the VLT ( ESO PR 08/99), are now beginning to cast some light on this long-standing mystery. The afterglow of GRB 000131 ESO PR Photo 28a/00 ESO PR Photo 28a/00 [Preview - JPEG: 400 x 475 pix - 41k] [Normal - JPEG: 800 x 949 pix - 232k] [Full-Res - JPEG: 1200 x 1424 pix - 1.2Mb] ESO PR Photo 28b/00 ESO PR Photo 28b/00 [Preview - JPEG: 400 x 480 pix - 67k] [Normal - JPEG: 800 x 959 pix - 288k] [Full-Res - JPEG: 1200 x 1439 pix - 856k] Caption : PR Photo 28a/00 is a colour composite image of the sky field around the position of the gamma-ray burst GRB 000131 that was detected on January 31, 2000. It is based on images obtained with the ESO Very Large Telescope at Paranal. The object is indicated with an arrow, near a rather bright star (magnitude 9, i.e., over 1 million times brighter than the faintest objects visible on this photo). This and other bright objects in the field are responsible for various unavoidable imaging effects, caused by optical reflections (ring-shaped "ghost images", e.g. to the left of the brightest star) and detector saturation effects (horizontal and vertical straight lines and coloured "coronae" at the bright objects, and areas of "bleeding", e.g. below the bright star). PR Photo 28b/00 shows the rapid fading of the optical counterpart of GRB 000131 (slightly left of the centre), by means of exposures with the VLT on February 4 (upper left), 6 (upper right), 8 (lower left) and March 5 (lower right). It is no longer visible on the last photo. Technical information about these photos is available below. A gamma-ray burst was detected on January 31, 2000, by an international network of satellites ( Ulysses , NEAR and Konus ) via the InterPlanetary Network (IPN) [2]. It was designated GRB 000131 according to the date of the event. From geometric triangulation by means of the measured, exact arrival times of the signal at the individual satellites, it was possible to determine the direction from which the burst came. It was found to be from a point within a comparatively small sky area (about 50 arcmin 2 or 1/10 of the apparent size of the Moon), just inside the border of the southern constellation Carina (The Keel). Follow-up observations were undertaken by a group of European astronomers [1] with the ESO Very Large Telescope at the Paranal Observatory. A comparison of several exposures with the FORS1 multi-mode instrument at the 8.2-m VLT ANTU telescope during the nights of February 3-4 and 5-6 revealed a faint, point-like object that was fading rapidly - this was identified as the optical counterpart of the gamma-ray burst (the "afterglow"). On the second night, the R-magnitude (brightness) was found to be only 24.4, or 30 million times fainter than visible with the unaided eye in a dark sky. It was also possible to observe it with a camera at the 1.54-m Danish Telescope at the La Silla Observatory , albeit only in a near-infrared band and with a 1-hour exposure. Additional observations were made on February 8 with the SOFI multi-mode instrument at the ESO 3.58-m New Technology Telescope (NTT) at La Silla. The observations were performed partly by the astronomers from the group, partly in "service mode" by ESO staff at La Silla and Paranal. The observations showed that the light from the afterglow was very red, without blue and green light. This indicated a comparatively large distance and, assuming that the light from the explosion would originally have had the same colour (spectral distribution) as that of optical counterparts of other observed gamma-ray bursts, a photometric redshift of 4.35 to 4.70 was deduced [3]. A spectrum of GRB 000131 ESO PR Photo 28c/00 ESO PR Photo 28c/00 [Preview - JPEG: 400 x 332 pix - 22k] [Normal - JPEG: 800 x 663 pix - 62k] Caption : PR Photo 28c/00 shows the spectrum of the afterglow of GRB 000131 , obtained during a 3-hr exposure with the FORS1 multi-mode instrument at VLT ANTU on February 8, 2000. The "Lyman-alpha break" at wavelength 670.1 nm is indicated. Technical information about this photo is available below. An accurate measurement of the redshift - hence the distance - requires spectroscopic observations. A spectrum of GRB 000131 was therefore obtained on February 8, 2000, cf. PR Photo 28c/00 . At this time, the brightness had decreased further and the object had become so faint (R-magnitude 25.3) that a total of 3 hours of exposure time was necessary with VLT ANTU + FORS1 [4]. Still, this spectrum is quite "noisy". The deduced photometric redshift of GRB 000131 predicts that a "break" will be seen in the red region of the spectrum, at a wavelength somewhere between 650 and 700 nm. This break is caused by the strong absorption of light in intergalactic hydrogen clouds along the line of sight. The effect is known as the "Lyman-alpha forest" and is observed in all remote objects [5]. As PR Photo 28c/00 shows, such a break was indeed found at wavelength 670.1 nm. Virtually all light at shorter wavelengths from the optical counterpart of GRB 000131 is absorbed by intervening hydrogen clouds. From the rest wavelength of the Lyman-alpha break (121.6 nm), the redshift of GRB 000131 is then determined as 4.50, corresponding to a travel time of more than 90% of the age of the Universe . The most distant gamma-ray burst so far The measured redshift of 4.50 makes GRB 000131 the most distant gamma-ray burst known (the previous, spectroscopically confirmed record was 3.42). Assuming an age of the Universe of the order of 12 - 14,000 million years, the look-back time indicates that the explosion took place around the time our own galaxy, the Milky Way, was formed and at least 6,000 million years before the solar system was born. GRB 000131 and other gamma-ray bursts are believed to have taken place in remote galaxies. However, due to the huge distance, it has not yet been possible to see the galaxy in which the GRB 000131 event took place (the "host" galaxy). From the observed fading of the afterglow it is possible to estimate that the maximum brightness of this explosion was at least 10,000 times brighter than the host galaxy. Future studies of gamma-ray bursts The present team of astronomers has now embarked upon a detailed study of the surroundings of GRB 000131 with the VLT. A main goal is to observe the properties of the host galaxy. From the observations of about twenty optical counterparts of gamma-ray bursts identified until now, it is becoming increasingly clear that these very rare events are somehow related to the death of massive, short-lived stars . But despite the accumulating amount of excellent data, the details of the mechanism that leads to such dramatic explosions still remain a puzzle to astrophysicists. The detection and present follow-up observations of GRB 000131 highlight the new possibilities for studies of the extremely distant (and very early) Universe, now possible by means of gamma-ray bursts. When observed with the powerful instruments at a large ground-based telescope like the VLT, this incredibly bright class of cosmological objects may throw light on the fundamental processes of star formation in the infant universe. Of no less interest is the opportunity to analyse the chemical composition of the gas clouds at the epoch galaxies formed, by means of the imprints of the corresponding absorption lines on the afterglow spectrum. Waiting for the opportunity In this context, it would be extremely desirable to obtain very detailed (high-dispersion) spectra of the afterglow of a future gamma-ray burst, soon after the detection and while it is still sufficiently bright. It would for instance be possible to observe a gamma-ray burst like GRB 000131 with the UVES spectrograph at VLT KUEYEN at the moment of maximum brightness (that may have been about magnitude 16). An example of chemical studies of clouds at intermediate distance by means of a more nearby quasar is shown in ESO PR Photo 09h/00. Attempts are therefore now made to shorten considerably the various steps needed to perform such observations. This concerns especially the time needed to identify the counterpart of a gamma-ray burst and - to a lesser extent - the necessary reaction time at the VLT to point UVES towards the object (in theory, a matter of minutes only). The launch of the HETE-2 (High Energy Transient Explorer 2) gamma-ray burst satellite on October 9, 2000, is a major step in this direction. Under optimal conditions, a relative accurate sky position of a gamma-ray burst may henceforth reach the astronomy community within only 10-20 seconds of the first detection by this satellite. More information The research described in this press release is the subject of a scientific article by the team, entitled "VLT Identification of the optical afterglow of the gamma-ray burst GRB 000131 at z = 4.50" ; it will appear in a special VLT-issue (Letters to the Editor) of the European journal Astronomy & Astrophysics (December 1, 2000). The results are being presented today (October 18) at the joint CNR/ESO meeting on "Gamma-Ray Burst in the Afterglow Era" in Rome, Italy. Note also the related article in the ESO Messenger (No. 100, p. 32, June 2000). Notes [1]: The team consists of Michael Andersen (University of Oulu, Finland), Holger Pedersen, Jens Hjorth, Brian Lindgren Jensen, Lisbeth Fogh Olsen, Lise Christensen (University of Copenhagen, Denmark), Leslie Hunt (Centro per l'Astronomia Infrarossa e lo Studio del Mezzo, Florence, Italy), Javier Gorosabel (Danish Space Research Institute, Denmark), Johan Fynbo, Palle Møller (European Southern Observatory), Richard Marc Kippen (University of Alabama in Huntsville and NASA/Marshall Space Flight Center, USA), Bjarne Thomsen (University of Århus, Denmark), Marianne Vestergaard (Ohio State University, USA), Nicola Masetti, Eliana Palazzi (Instituto Tecnologie e Studio Radiazoni Extraterresti, Bologna, Italy) Kevin Hurley (University of California, Berkeley, USA), Thomas Cline (NASA Goddard Space Flight Center, Greenbelt, USA), Lex Kaper (Sterrenkundig Instituut ``Anton Pannekoek", the Netherlands) and Andreas O. Jaunsen (formerly University of Oslo, Norway; now ESO-Paranal). [2]: Detailed reports about the early observations of this gamma-ray burst are available at the dedicated webpage within the GRB Coordinates Network website. [3]: The photometric redshift method makes it possible to judge the distance to a remote celestial object (a galaxy, a quasar, a gamma-ray burst afterglow) from its measured colours. It is based on the proportionality between the distance and the velocity along the line of sight (Hubble's law) that reflects the expansion of the Universe. The larger the distance of an object is, the larger is its velocity and, due to the Doppler effect, the spectral shift of its emission towards longer (redder) wavelengths. Thus, the measured colour provides a rough indication of the distance. Examples of this method are shown in ESO PR 20/98 (Photos 48a/00 and 48e/00). [4]: In fact, the object was so faint that the positioning of the spectrograph slit had to be done in "blind" offset, i.e. without actually seeing the object on the slit during the observation. This very difficult observational feat was possible because of excellent preparations by the team of astronomers and the very good precision of the telescope and instrument. [5]: The " Lyman-alpha forest" refers to the crowding of absorption lines from intervening hydrogen clouds, shortward of the strong Lyman-alpha spectral line at rest wavelength 121.6 nm. Good examples in the VLT ANTU + FORS1 spectra of distant quasars are shown in ESO PR Photos 14a-c/99 and, at much higher dispersion, in a spectrum obtained with VLT KUEYEN + UVES, cf. ESO PR 08/00 (Photo 09f/00). Technical information about the photos PR Photo 28a/00 : The photo is based on three 8-min exposures obtained with VLT ANTU and the multi-mode FORS1 instrument. The optical filters were B (seeing 0.9 arcsec; here rendered as blue), V (0.8 arcsec; green) and R (0.7 arcsec; red). The field measures 6.8 x 6.8 arcmin 2. North is up and East is left. PR Photo 28b/00 : The four R-exposures were obtained with VLT ANTU + FORS1 on February 4 (magnitude R = 23.3), 6 (24.4), 8 (25.1) and March 5 (no longer visible). The field measures 48 x 48 arcsec 2. North is up and East is left. PR Photo 28c/00 : The spectrum was obtained during a 3-hr exposure with the FORS1 multi-mode instrument at VLT ANTU on February 8, 2000, when the object's magnitude was only R = 25.3. The mean levels of the spectral continua on either side of the redshifted "Lyman-alpha break" at wavelength 670.1 nm are indicated.

VLT Data Flow System Begins Operation

NASA Astrophysics Data System (ADS)

1999-06-01

Building a Terabyte Archive at the ESO Headquarters The ESO Very Large Telescope (VLT) is the sum of many sophisticated parts. The site at Cerro Paranal in the dry Atacama desert in Northern Chile is one of the best locations for astronomical observations from the surface of the Earth. Each of the four 8.2-m telescopes is a technological marvel with self-adjusting optics placed in a gigantic mechanical structure of the utmost precision, continuously controlled by advanced soft- and hardware. A multitude of extremely complex instruments with sensitive detectors capture the faint light from distant objects in the Universe and record the digital data fast and efficiently as images and spectra, with a minimum of induced noise. And now the next crucial link in this chain is in place. A few nights ago, following an extended test period, the VLT Data Flow System began providing the astronomers with a steady stream of high-quality, calibrated image and spectral data, ready to be interpreted. The VLT project has entered into a new phase with a larger degree of automation. Indeed, the first 8.2-m Unit Telescope, ANTU, with the FORS1 and ISAAC instruments, has now become a true astronomy machine . A smooth flow of data through the entire system ESO PR Photo 25a/99 ESO PR Photo 25a/99 [Preview - JPEG: 400 x 292 pix - 104k] [Normal - JPEG: 800 x 584 pix - 264k] [High-Res - JPEG: 3000 x 2189 pix - 1.5M] Caption to ESO PR Photo 25a/99 : Simplified flow diagramme for the VLT Data Flow System . It is a closed-loop software system which incorporates various subsystems that track the flow of data all the way from the submission of proposals to storage of the acquired data in the VLT Science Archive Facility. The DFS main components are: Program Handling, Observation Handling, Telescope Control System, Science Archive, Pipeline and Quality Control. Arrows indicate lines of feedback. Already from the start of this project more than ten years ago, the ESO Very Large Telescope was conceived as a complex digital facility to explore the Universe. In order for astronomers to be able to use this marvellous research tool in the most efficient manner possible, the VLT computer software and hardware systems must guarantee a smooth flow of scientific information through the entire system. This process starts when the astronomers submit well-considered proposals for observing time and it ends with large volumes of valuable astronomical data being distributed to the international astronomical community. For this, ESO has produced an integrated collection of software and hardware, known as the VLT Data Flow System (DFS) , that manages and facilitates the flow of scientific information within the VLT Observatory. Early information about this new concept was published as ESO Press Release 12/96 and extensive tests were first carried out at ESOs 3.5-m New Technology Telescope (NTT) at La Silla, cf. ESO Press Release 03/97 [1]. The VLT DFS is a complete (end-to-end) system that guarantees the highest data quality by optimization of the observing process and repeated checks that identify and eliminate any problems. It also introduces automatic calibration of the data, i.e. the removal of external effects introduced by the atmospheric conditions at the time of the observations, as well as the momentary state of the telescope and the instruments. From Proposals to Observations In order to obtain observing time with ESO telescopes, also with the VLT, astronomers must submit a detailed observing proposal to the ESO Observing Programmes Committee (OPC) . It meets twice a year and ranks the proposals according to scientific merit. More than 1000 proposals are submitted each year, mostly by astronomers from the ESO members states and Chile; the competition is fierce and only a fraction of the total demand for observing time can be fulfilled. During the submission of observing proposals, DFS software tools available over the World Wide Web enable the astronomers to simulate their proposed observations and provide accurate estimates of the amount of telescope time they will need to complete their particular scientific programme. Once the proposals have been reviewed by the OPC and telescope time is awarded by the ESO management according to the recommendation by this Committee, the successful astronomers begin to assemble detailed descriptions of their intended observations (e.g. position in the sky, time and duration of the observation, the instrument mode, etc.) in the form of computer files called Observation Blocks (OBs) . The software to make OBs is distributed by ESO and used by the astronomers at their home institutions to design their observing programs well before the observations are scheduled at the telescope. The OBs can then be directly executed by the VLT and result in an increased efficiency in the collection of raw data (images, spectra) from the science instruments on the VLT. The activation (execution) of OBs can be done by the astronomer at the telescope on a particular set of dates ( visitor mode operation) or it can be done by ESO science operations astronomers at times which are optimally suited for the particular scientific programme ( service mode operation). An enormous VLT Data Archive ESO PR Photo 25b/99 ESO PR Photo 25b/99 [Preview - JPEG: 400 x 465 pix - 160k] [Normal - JPEG: 800 x 929 pix - 568k] [High-Res - JPEG: 3000 x 3483 pix - 5.5M] Caption to ESO PR Photo 25b/99 : The first of several DVD storage robot at the VLT Data Archive at the ESO headquarters include 1100 DVDs (with a total capacity of about 16 Terabytes) that may be rapidly accessed by the archive software system, ensuring fast availbility of the requested data. The raw data generated at the telescope are stored by an archive system that sends these data regularly back to ESO headquarters in Garching (Germany) in the form of CD and DVD ROM disks. While the well-known Compact Disks (CD ROMs) store about 600 Megabytes (600,000,000 bytes) each, the new Digital Versatile Disks (DVD ROMs) - of the same physical size - can store up 3.9 Gigabytes (3,900,000,000 bytes) each, or over 6 times more. The VLT will eventually produce more than 20 Gigabytes (20,000,000,000 bytes) of astronomical data every night, corresponding to about 10 million pages of text [2]. Some of these data also pass through "software pipelines" that automatically remove the instrumental effects on the data and deliver data products to the astronomer that can more readily be turned into scientific results. Ultimately these data are stored in a permanent Science Archive Facility at ESO headquarters which is jointly operated by ESO and the Space Telescope European Coordinating Facility (ST-ECF). From here, data are distributed to astronomers on CD ROMs and over the World Wide Web. The archive facility is being developed to enable astronomers to "mine" the large volumes of data that will be collected from the VLT in the coming years. Within the first five years of operations the VLT is expected to produce around 100 Terabytes (100,000,000,000,000 bytes) of data. It is difficult to visualize this enormous amount of information. However, it corresponds to the content of 50 million books of 1000 pages each; they would occupy some 2,500 kilometres of bookshelves! The VLT Data Flow System enters into operation ESO PR Photo 25c/99 ESO PR Photo 25c/99 [Preview - JPEG: 400 x 444 pix - 164k] [Normal - JPEG: 800 x 887 pix - 552k] [High-Res - JPEG: 3000 x 3327 pix - 6.4M] Caption to ESO PR Photo 25c/99 : Astronomers from ESO Data Flow Operations Group at work with the VLT Archive. Science operations with the first VLT 8.2-m telescope ( ANTU ) began on April 1, 1999. Following the first call for proposals to use the VLT in October 1998, the OPC met in December and the observing schedule was finalized early 1999. The related Observation Blocks were prepared by the astronomers in February and March. Service-mode observations began in April and by late May the first scientific programs conducted by ESO science operations were completed. Raw data, instrument calibration information and the products of pipeline processing from these programs have now been assembled and packed onto CD ROMs by ESO science operations staff. On June 15 the first CD ROMs were delivered to astronomers in the ESO community. This event marks the closing of the data flow loop at the VLT for the first time and the successful culmination of more than 5 years of hard work by ESO engineers and scientists to implement a system for efficient and effective scientific data flow. This was achieved by a cross-organization science operations team involving staff in Chile and Europe. With the VLT Data Flow System, a wider research community will have access to the enormous wealth of data from the VLT. It will help astronomers to keep pace with the new technologies and extensive capabilities of the VLT and so obtain world-first scientific results and new insights into the universe. Notes [1] A more technical description of the VLT Data Flow System is available in Chapter 10 of the VLT Whitebook. [2] By definition, one "normal printed page" contains 2,000 characters. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Testing giant planet formation in the transitional disk of SAO 206462 using deep VLT/SPHERE imaging

NASA Astrophysics Data System (ADS)

Maire, A.-L.; Stolker, T.; Messina, S.; Müller, A.; Biller, B. A.; Currie, T.; Dominik, C.; Grady, C. A.; Boccaletti, A.; Bonnefoy, M.; Chauvin, G.; Galicher, R.; Millward, M.; Pohl, A.; Brandner, W.; Henning, T.; Lagrange, A.-M.; Langlois, M.; Meyer, M. R.; Quanz, S. P.; Vigan, A.; Zurlo, A.; van Boekel, R.; Buenzli, E.; Buey, T.; Desidera, S.; Feldt, M.; Fusco, T.; Ginski, C.; Giro, E.; Gratton, R.; Hubin, N.; Lannier, J.; Le Mignant, D.; Mesa, D.; Peretti, S.; Perrot, C.; Ramos, J. R.; Salter, G.; Samland, M.; Sissa, E.; Stadler, E.; Thalmann, C.; Udry, S.; Weber, L.

2017-05-01

Context. The SAO 206462 (HD 135344B) disk is one of the few known transitional disks showing asymmetric features in scattered light and thermal emission. Near-infrared scattered-light images revealed two bright outer spiral arms and an inner cavity depleted in dust. Giant protoplanets have been proposed to account for the disk morphology. Aims: We aim to search for giant planets responsible for the disk features and, in the case of non-detection, to constrain recent planet predictions using the data detection limits. Methods: We obtained new high-contrast and high-resolution total intensity images of the target spanning the Y to the K bands (0.95-2.3 μm) using the VLT/SPHERE near-infrared camera and integral field spectrometer. Results: The spiral arms and the outer cavity edge are revealed at high resolutions and sensitivities without the need for aggressive image post-processing techniques, which introduce photometric biases. We do not detect any close-in companions. For the derivation of the detection limits on putative giant planets embedded in the disk, we show that the knowledge of the disk aspect ratio and viscosity is critical for the estimation of the attenuation of a planet signal by the protoplanetary dust because of the gaps that these putative planets may open. Given assumptions on these parameters, the mass limits can vary from 2-5 to 4-7 Jupiter masses at separations beyond the disk spiral arms. The SPHERE detection limits are more stringent than those derived from archival NaCo/L' data and provide new constraints on a few recent predictions of massive planets (4-15 MJ) based on the spiral density wave theory. The SPHERE and ALMA data do not favor the hypotheses on massive giant planets in the outer disk (beyond 0.6''). There could still be low-mass planets in the outer disk and/or planets inside the cavity. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 095.C-0298 and 090.C-0443.

The Gaia-ESO Survey: dynamics of ionized and neutral gas in the Lagoon nebula (M 8)

NASA Astrophysics Data System (ADS)

Damiani, F.; Bonito, R.; Prisinzano, L.; Zwitter, T.; Bayo, A.; Kalari, V.; Jiménez-Esteban, F. M.; Costado, M. T.; Jofré, P.; Randich, S.; Flaccomio, E.; Lanzafame, A. C.; Lardo, C.; Morbidelli, L.; Zaggia, S.

2017-08-01

Aims: We present a spectroscopic study of the dynamics of the ionized and neutral gas throughout the Lagoon nebula (M 8), using VLT-FLAMES data from the Gaia-ESO Survey. The new data permit exploration of the physical connections between the nebular gas and the stellar population of the associated star cluster NGC 6530. Methods: We characterized through spectral fitting emission lines of Hα, [N II] and [S II] doublets, [O III], and absorption lines of sodium D doublet, using data from the FLAMES-Giraffe and UVES spectrographs, on more than 1000 sightlines toward the entire face of the Lagoon nebula. Gas temperatures are derived from line-width comparisons, densities from the [S II] doublet ratio, and ionization parameter from Hα/[N II] ratio. Although doubly-peaked emission profiles are rarely found, line asymmetries often imply multiple velocity components along the same line of sight. This is especially true for the sodium absorption, and for the [O III] lines. Results: Spatial maps for density and ionization are derived, and compared to other known properties of the nebula and of its massive stars 9 Sgr, Herschel 36 and HD 165052 which are confirmed to provide most of the ionizing flux. The detailed velocity fields across the nebula show several expanding shells, related to the cluster NGC 6530, the O stars 9 Sgr and Herschel 36, and the massive protostar M 8East-IR. The origins of kinematical expansion and ionization of the NGC 6530 shell appear to be different. We are able to put constrains on the line-of-sight (relative or absolute) distances between some of these objects and the molecular cloud. The data show that the large obscuring band running through the middle of the nebula is being compressed by both sides, which might explain its enhanced density. We also find an unexplained large-scale velocity gradient across the entire nebula. At larger distances, the transition from ionized to neutral gas is studied using the sodium lines. Based on observations collected with the FLAMES spectrograph at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia-ESO Large Public Survey (program 188.B-3002).Full Tables A.1 and A.2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/604/A135

Keck and VLT Observations of Super-Damped Lyman-Alpha Absorbers at z 2- 2.5: Constraints on Chemical Compositions and Physical Conditions

NASA Astrophysics Data System (ADS)

Kulkarni, Varsha P.; Som, Debopam; Morrison, Sean; Péroux, Celine; Quiret, Samuel; York, Donald G.

2015-12-01

We report Keck/Echellette Spectrograph and Imager and Very Large Telescope/Ultraviolet-Visual Echelle Spectrograph observations of three super-damped Lyα quasar absorbers with H i column densities log NH i ≥ 21.7 at redshifts 2 ≲ z ≲ 2.5. All three absorbers show similar metallicities (˜-1.3 to -1.5 dex), and dust depletion of Fe, Ni, and Mn. Two of the absorbers show supersolar [S/Zn] and [Si/Zn]. We combine our results with those for other damped Lyα a absorbers (DLAs) to examine trends between NH i, metallicity, and dust depletion. A larger fraction of the super-DLAs lie close to or above the line [X/H] = 20.59 - log NH i in the metallicity versus NH i plot, compared to the less gas-rich DLAs, suggesting that super-DLAs are more likely to be rich in molecules. Unfortunately, our data for Q0230-0334 and Q0743+1421 do not cover H2 absorption lines. For Q1418+0718, some H2 lines are covered, but not detected. CO is not detected in any of our absorbers. For DLAs with log NH i < 21.7, we confirm strong correlation between metallicity and Fe depletion, and find a correlation between metallicity and Si depletion. For super-DLAs, these correlations are weaker or absent. The absorbers toward Q0230-0334 and Q1418+0718 show potential detections of weak Lyα emission, implying star formation rates of ˜1.6 and ˜0.7 M⊙ yr-1, respectively (ignoring dust extinction). Upper limits on the electron densities from C ii*/C ii or Si ii*/Si ii are low, but are higher than the median values in less gas-rich DLAs. Finally, systems with log NH i > 21.7 may have somewhat narrower velocity dispersions Δv90 than the less gas-rich DLAs, and may arise in cooler and/or less turbulent gas. Includes observations collected during program ESO 93.A-0422 at the European Southern Observatory (ESO) Very Large Telescope (VLT) with the Ultraviolet-Visual Echelle Spectrograph (UVES) on the 8.2 m telescopes operated at the Paranal Observatory, Chile. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

Petrology and geochemistry of VLT glasses from double drive tube 79001/2

NASA Technical Reports Server (NTRS)

Wentworth, Susan J.; Lindstrom, D. J.; Martinez, R. R.; Mckay, D. S.

1993-01-01

As a part of more general studies of soils from Apollo 17 double drive tube 79001/2, glasses from the 79001/2 core are being analyzed by a multidisciplinary approach including SEM/EDS and INAA. Efforts are currently focused on VLT (very low-Ti; TiO2 less than 1 wt%) mare glasses, which are common in 79001/2 and have also been found in other Apollo 17 soils. One of the primary objectives is to determine whether any or all of the Apollo 17 VLT glasses represent pristine volcanic compositions. In addition, the range of VLT glass compositions and possible relationships between the glasses and VLT lithic samples, for which some geochemical data have been obtained previously, is being defined.

Optical turbulence profiling with Stereo-SCIDAR for VLT and ELT

NASA Astrophysics Data System (ADS)

Osborn, J.; Wilson, R. W.; Sarazin, M.; Butterley, T.; Chacón, A.; Derie, F.; Farley, O. J. D.; Haubois, X.; Laidlaw, D.; LeLouarn, M.; Masciadri, E.; Milli, J.; Navarrete, J.; Townson, M. J.

2018-04-01

Knowledge of the Earth's atmospheric optical turbulence is critical for astronomical instrumentation. Not only does it enable performance verification and optimisation of existing systems but it is required for the design of future instruments. As a minimum this includes integrated astro-atmospheric parameters such as seeing, coherence time and isoplanatic angle, but for more sophisticated systems such as wide field adaptive optics enabled instrumentation the vertical structure of the turbulence is also required. Stereo-SCIDAR is a technique specifically designed to characterise the Earth's atmospheric turbulence with high altitude resolution and high sensitivity. Together with ESO, Durham University has commissioned a Stereo-SCIDAR instrument at Cerro Paranal, Chile, the site of the Very Large Telescope (VLT), and only 20 km from the site of the future Extremely Large Telescope (ELT). Here we provide results from the first 18 months of operation at ESO Paranal including instrument comparisons and atmospheric statistics. Based on a sample of 83 nights spread over 22 months covering all seasons, we find the median seeing to be 0.64" with 50% of the turbulence confined to an altitude below 2 km and 40% below 600 m. The median coherence time and isoplanatic angle are found as 4.18 ms and 1.75" respectively. A substantial campaign of inter-instrument comparison was also undertaken to assure the validity of the data. The Stereo-SCIDAR profiles (optical turbulence strength and velocity as a function of altitude) have been compared with the Surface-Layer SLODAR, MASS-DIMM and the ECMWF weather forecast model. The correlation coefficients are between 0.61 (isoplanatic angle) and 0.84 (seeing).

Spinning Like a Blue Straggler: The Population of Fast Rotating Blue Straggler Stars in ω Centauri

NASA Astrophysics Data System (ADS)

Mucciarelli, A.; Lovisi, L.; Ferraro, F. R.; Dalessandro, E.; Lanzoni, B.; Monaco, L.

2014-12-01

By using high-resolution spectra acquired with FLAMES-GIRAFFE at the ESO/VLT, we measured the radial and rotational velocities for 110 blue straggler stars (BSSs) in ω Centauri, the globular cluster-like stellar system harboring the largest known BSS population. According to their radial velocities, 109 BSSs are members of the system. The rotational velocity distribution is very broad, with the bulk of BSSs spinning at less than ~40 km s-1 (in agreement with the majority of such stars observed in other globular clusters) and a long tail reaching ~200 km s-1. About 40% of the sample has ve sin i > 40 km s-1 and about 20% has ve sin i > 70 km s-1. Such a large fraction is very similar to the percentage of fast rotating BSSs observed in M4. Thus, ω Centauri is the second stellar cluster, beyond M4, with a surprisingly high population of fast spinning BSSs. We found a hint of radial behavior for a fraction of fast rotating BSSs, with a mild peak within one core radius, and a possible rise in the external regions (beyond four core radii). This may suggest that recent formation episodes of mass transfer BSSs occurred preferentially in the outskirts of ω Centauri, or that braking mechanisms able to slow down these stars are least efficient in the lowest density environments. Based on observations collected at the ESO-VLT under the programs 077.D-0696(A), 081.D-0356(A), and 089.D-0298(A).

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ryde, N.; Schultheis, M.; Grieco, V.

The structure, formation, and evolution of the Milky Way bulge is a matter of debate. Important diagnostics for discriminating between models of bulge formation and evolution include α-abundance trends with metallicity, and spatial abundance and metallicity gradients. Due to the severe optical extinction in the inner Bulge region, only a few detailed investigations of this region have been performed. Here we aim at investigating the inner 2 degrees of the Bulge (projected galactocentric distance of approximately 300 pc), rarely investigated before, by observing the [α/Fe] element trends versus metallicity, and by trying to derive the metallicity gradient in the bmore » < 2° region. [α/Fe] and metallicities have been determined by spectral synthesis of 2 μm spectra of 28 M-giants in the Bulge, lying along the southern minor axis at (l, b) = (0, 0), (0, −1°), and (0, −2°). These were observed with the CRIRES spectrometer at the Very Large Telescope, (VLT) at high spectral resolution. Low-resolution K-band spectra, observed with the ISAAC spectrometer at the VLT, are used to determine the effective temperature of the stars. We present the first connection between the Galactic center (GC) and the Bulge using similar stars, high spectral resolution, and analysis techniques. The [α/Fe] trends in all our three fields show a large similarity among each other and with trends further out in the Bulge. All point to a rapid star formation episode in the Bulge. We find that there is a lack of an [α/Fe] gradient in the Bulge all the way into the center, suggesting a homogeneous Bulge when it comes to the enrichment process and star formation history. We find a large range of metallicities from −1.2 < [Fe/H] < +0.3, with a lower dispersion in the GC: −0.2 < [Fe/H] < +0.3. The derived metallicities of the stars in the three fields get, in the mean, progressively higher the closer to the Galactic plane they lie. We could interpret this as a continuation of the metallicity gradient established further out in the Bulge, but due to the low number of stars and possible selection effects, more data of the same sort as presented here is necessary to conclude on the inner metallicity gradient from our data alone. Our results firmly argue for the center being in the context of the Bulge rather than very distinct.« less

Ruprecht 106: The first single population globular cluster?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Villanova, S.; Geisler, D.; Muñoz, C.

2013-12-01

All old Galactic globular clusters (GCs) studied in detail to date host at least two generations of stars, where the second is formed from gas polluted by processed material produced by massive stars of the first. This process can happen if the initial mass of the cluster exceeds a threshold above which ejecta are retained and a second generation is formed. A determination of this mass threshold is mandatory in order to understand how GCs form. We analyzed nine red giant branch stars belonging to the cluster Ruprecht 106. Targets were observed with the UVES@VLT2 spectrograph. Spectra cover a widemore » range and allowed us to measure abundances for light (O, Na, Mg, Al), α (Si, Ca, Ti), iron-peak (Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and neutron-capture (Y, Zr, Ba, La, Ce, Pr, Nd, Sm, Eu, Dy, Pb) elements. Based on these abundances, we show that Ruprecht 106 is the first convincing example of a single-population GC (i.e., a true simple stellar population), although the sample is relatively small. This result is supported also by an independent photometric test and by the horizontal branch morphology and the dynamical state. It is old (∼12 Gyr) and, at odds with other GCs, has no α-enhancement. The material it formed from was contaminated by both s- and r-process elements. The abundance pattern points toward an extragalactic origin. Its present-day mass (M = 10{sup 4.83} M {sub ☉}) can be assumed as a strong lower limit for the initial mass threshold below which no second generation is formed. Clearly, its initial mass must have been significantly greater, but we have no current constraints on the amount of mass loss during its evolution.« less

REOSC Delivers the Best Astronomical Mirror in the World to ESO

NASA Astrophysics Data System (ADS)

1999-12-01

On December 14, 1999, REOSC , the Optical Department of the SAGEM Group , finished the polishing of the fourth 8.2-m main mirror for the Very Large Telescope (VLT) of the European Southern Observatory. The mirror was today delivered to ESO at a ceremony at the REOSC factory in Saint Pierre du Perray, just south of Paris. The precision of the form of the mirror that was achieved during the polishing process is 8.5 nanometer (1 nanometer = 1 millionth of a millimetre) over the optical surface. This exceptional value corresponds to an optical resolution (theoretical image sharpness) of 0.03 arcseconds in the visible spectrum. This corresponds to distinguishing two objects separated by only 15 cm at a distance of 1000 km and will allow to detect astronomical objects that are 10,000 million times fainter than what can be perceived with the unaided eye. This impressive measure of quality, achieved by the REOSC teams during much painstaking work, implies that this VLT mirror is the most accurate in the world. In fact, all four 8.2-m VLT main mirrors polished by REOSC are well within the very strict specifications set by ESO, but this is the best of them all. The celebration today is the successful highlight of a contract initiated more than ten years ago, during which REOSC has perfected new polishing and control techniques - innovations improved and developed in a unique workshop dedicated to these giant mirrors. These methods and means are directly applicable to the new generations of segmented mirrors that are now being developed for astronomy and space observations. They are, in this sense, at the foremost front of optical technology. REOSC, the Optical Department of the SAGEM Group , is specialised in the study and realisation of high-precision optics for astronomy, space, defence, science and industry. For earlier information about the work on the VLT mirrors, cf. ESO Press Release 15/95 (13 November 1995). The SAGEM Group is a French high-technology group. It employs about 15,500 people - more information is available at URL: www.sagem.com. Information about the ESO and the VLT project is available via the ESO website: www.eso.org. Some Key Dates The polishing at REOSC of the main mirrors for the four VLT Unit Telescopes has been a major industrial feat. Here are some of the main dates: July 1989 ESO and REOSC sign contract for the polishing of the four 8.2-m and various associated activities July 1989 - April 1992 Design activities, construction of REOSC production plant April 1992 Mirror Container and concrete dummy mirror blank completed - test transport May 1992 Inauguration of REOSC production plant July 1993 Delivery of first 8.2-m mirror blank to ESO at Schott Glaswerke AG (Mainz, Germany) October 1994 Delivery of second 8.2-m mirror blank to ESO at Schott Glaswerke AG September 1995 Delivery of third 8.2-m mirror blank to ESO at Schott Glaswerke AG May 1996 Acceptance by ESO of first polished mirror at REOSC September 1996 Delivery of fourth 8.2-m mirror blank to ESO at Schott Glaswerke AG October 1996 Acceptance by ESO of second polished mirror at REOSC June 1997 Acceptance by ESO of third polished mirror at REOSC October - December 1997 Transport and delivery of first mirror to Paranal by Gondrand (France) August - September 1998 Transport and delivery of second mirror to Paranal by Gondrand December 1998 - January 1999 Transport and delivery of third mirror to Paranal by Gondrand December 1999 Acceptance by ESO of fourth polished mirror at REOSC February 1999 - April 2000 Transport and delivery of fourth mirror to Paranal by Gondrand Note [1] A Press Release on the REOSC event and the delivery of the fourth VLT main mirror to ESO is also published by SAGEM (in French and English). How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO PR Photo 44/99 may be reproduced, if credit is given to SAGEM and the European Southern Observatory.

VST: VLT Survey Telescope.

NASA Astrophysics Data System (ADS)

Arnaboldi, M.; Capaccioli, M.; Mancini, D.; Rafanelli, P.; Scaramella, R.; Sedmak, G.; Vettolani, G. P.

1998-09-01

The VLT era is rapidly approaching: the first instruments, ISAAC and FORS at UT1, will be available by the year 1999. Indeed, the beginning of the new millennium will witness fierce competition among quite a few 8-m telescopes, operated by different groups. As a consequence, there is a strong need to prepare, in a timely manner, suitable targetlists for the VLT, in order for it to play the leading role in ground-based optical and IR astronomy in the next decade. Preparation is one of the keys to success for the VLT observations.

Development of a visible light transmission (VLT) measurement system using an open-path optical method

NASA Astrophysics Data System (ADS)

Nurulain, S.; Manap, H.

2017-09-01

This paper describes about a visible light transmission (VLT) measurement system using an optical method. VLT rate plays an important role in order to determine the visibility of a medium. Current instrument to measure visibility has a gigantic set up, costly and mostly fails to function at low light condition environment. This research focuses on the development of a VLT measurement system using a simple experimental set-up and at a low cost. An open path optical technique is used to measure a few series of known-VLT thin film that act as sample of different visibilities. This measurement system is able to measure the light intensity of these thin films within the visible light region (535-540 nm) and the response time is less than 1s.

Very-long-term and short-term chromatic adaptation: are their influences cumulative?

PubMed

Belmore, Suzanne C; Shevell, Steven K

2011-02-09

Very-long-term (VLT) chromatic adaptation results from exposure to an altered chromatic environment for days or weeks. Color shifts from VLT adaptation are observed hours or days after leaving the altered environment. Short-term chromatic adaptation, on the other hand, results from exposure for a few minutes or less, with color shifts measured within seconds or a few minutes after the adapting light is extinguished; recovery to the pre-adapted state is complete in less than an hour. Here, both types of adaptation were combined. All adaptation was to reddish-appearing long-wavelength light. Shifts in unique yellow were measured following adaptation. Previous studies demonstrate shifts in unique yellow due to VLT chromatic adaptation, but shifts from short-term chromatic adaptation to comparable adapting light can be far greater than from VLT adaptation. The question considered here is whether the color shifts from VLT adaptation are cumulative with large shifts from short-term adaptation or, alternatively, does simultaneous short-term adaptation eliminate color shifts caused by VLT adaptation. The results show the color shifts from VLT and short-term adaptation together are cumulative, which indicates that both short-term and very-long-term chromatic adaptation affect color perception during natural viewing. Copyright © 2010 Elsevier Ltd. All rights reserved.

VizieR Online Data Catalog: Abundances & RVs for stars near (or in) NGC6273 (Johnson+, 2017)

NASA Astrophysics Data System (ADS)

Johnson, C. I.; Caldwell, N.; Rich, R. M.; Mateo, M.; Bailey, J. I., III; Clarkson, W. I.; Olszewski, E. W.; Walker, M. G.

2017-09-01

In order to efficiently obtain a large number of high-resolution spectra, we employed the Michigan/Magellan Fiber System (M2FS) and MSpec multi-object spectrograph mounted on the Magellan-Clay 6.5m telescope (R~27000). We supplemented the M2FS CaT data set with additional observations of 300 RGB stars taken with the VLT FLAMES-GIRAFFE instrument. The data were downloaded from the European Southern Observatory (ESO) Science Archive Facility (R~18000 from 8482 to 9000Å). In support of our spectroscopic observations, we have obtained new HST Wide Field Camera 3 UVIS channel (WFC3/UVIS) data centered on NGC 6273 that includes the F336W, F438W, F555W, and F814W filters. (7 data files).

Philippe Busquin Visits Paranal

NASA Astrophysics Data System (ADS)

2003-07-01

The European Commissioner for Research, Mr. Philippe Busquin, who is currently visiting the Republic of Chile, arrived at the ESO Paranal Observatory on Tuesday afternoon, July 29, 2003. The Commissioner was accompanied, among others, by the EU Ambassador to Chile, Mr. Wolfgang Plasa, and Ms. Christina Lazo, Executive Director of the Chilean Science and Technology Agency (CONICYT). The distinguished visitors were able to acquaint themselves with one of the foremost European research facilities, the ESO Very Large Telescope (VLT), during an overnight stay at this remote site. Arriving after the long flight from Europe in Antofagasta, capital of the II Chilean region, the Commissioner continued along the desert road to Paranal, some 130 km south of Antofasta and site of the world's largest and most efficient optical/infrared astronomical telescope facility. The high guests were welcomed by the ESO Director General, Dr. Catherine Cesarsky, and the ESO Representative in Chile, Mr. Daniel Hofstadt, as well as ESO staff members of many nationalities. The visitors were shown the various high-tech installations at the observatory, including many of the large, front-line VLT astronomical instruments that have been built in collaboration between ESO and European research institutes. Explanations were given by ESO astronomers and engineers and the Commissioner gained a good impression of the wide range of exciting research programmes that are carried out with the VLT. Having enjoyed the spectacular sunset over the Pacific Ocean from the KUEYEN telescope, one of the four 8.2-m telescopes that form the VLT array, the Commissioner visited the VLT Control Room from where the four 8.2-m Unit Telescopes and the VLT Interferometer (VLTI) are operated. Here, the Commissioner was invited to follow an observing sequence at the console of the KUEYEN telescope. " This is a tribute to the human genius ", commented the Commissioner. " It is an extraordinary contribution to the development of knowledge, and as Commissioner for Research, I am proud that this is a European achievement. " " It is a great pleasure to receive Commissioner Busquin, whose actions towards European research we admire, and to share with him the excitement about the wonders of the Universe and the advanced technology that allows us to probe them" , said the Director General of ESO, Dr. Catherine Cesarsky. The Commissioner and the other guests will leave Paranal in the early morning of Wednesday, July 30, travelling back to Santiago de Chile via Antofagasta.

Cosmological Gamma-Ray Bursts and Hypernovae Conclusively Linked

NASA Astrophysics Data System (ADS)

2003-06-01

Clearest-Ever Evidence from VLT Spectra of Powerful Event Summary A very bright burst of gamma-rays was observed on March 29, 2003 by NASA's High Energy Transient Explorer (HETE-II) , in a sky region within the constellation Leo. Within 90 min, a new, very bright light source (the "optical afterglow") was detected in the same direction by means of a 40-inch telescope at the Siding Spring Observatory (Australia) and also in Japan. The gamma-ray burst was designated GRB 030329 , according to the date. And within 24 hours, a first, very detailed spectrum of this new object was obtained by the UVES high-dispersion spectrograph on the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile). It allowed to determine the distance as about 2,650 million light-years (redshift 0.1685). Continued observations with the FORS1 and FORS2 multi-mode instruments on the VLT during the following month allowed an international team of astronomers [1] to document in unprecedented detail the changes in the spectrum of the optical afterglow of this gamma-ray burst . Their detailed report appears in the June 19 issue of the research journal "Nature". The spectra show the gradual and clear emergence of a supernova spectrum of the most energetic class known, a "hypernova" . This is caused by the explosion of a very heavy star - presumably over 25 times heavier than the Sun. The measured expansion velocity (in excess of 30,000 km/sec) and the total energy released were exceptionally high, even within the elect hypernova class. From a comparison with more nearby hypernovae, the astronomers are able to fix with good accuracy the moment of the stellar explosion. It turns out to be within an interval of plus/minus two days of the gamma-ray burst. This unique conclusion provides compelling evidence that the two events are directly connected. These observations therefore indicate a common physical process behind the hypernova explosion and the associated emission of strong gamma-ray radiation. The team concludes that it is likely to be due to the nearly instantaneous, non-symmetrical collapse of the inner region of a highly developed star (known as the "collapsar" model) . The March 29 gamma-ray burst will pass into the annals of astrophysics as a rare "type-defining event", providing conclusive evidence of a direct link between cosmological gamma-ray bursts and explosions of very massive stars . PR Photo 17a/03 : Image of the optical afterglow of GRB 030329 (VLT FORS1+2). PR Photo 17b/03 : A series of VLT spectra of the optical afterglow of GRB 030329. What are Gamma-Ray Bursts? One of the currently most active fields of astrophysics is the study of the dramatic events known as "gamma-ray bursts (GRBs)" . They were first detected in the late 1960's by sensitive instruments on-board orbiting military satellites, launched for the surveillance and detection of nuclear tests. Originating, not on the Earth, but far out in space, these short flashes of energetic gamma-rays last from less than a second to several minutes. Despite major observational efforts, it is only within the last six years that it has become possible to pinpoint with some accuracy the sites of some of these events. With the invaluable help of comparatively accurate positional observations of the associated X-ray emission by various X-ray satellite observatories since early 1997, astronomers have until now identified about fifty short-lived sources of optical light associated with GRBs (the "optical afterglows"). Most GRBs have been found to be situated at extremely large ("cosmological") distances. This implies that the energy released in a few seconds during such an event is larger than that of the Sun during its entire lifetime of more than 10,000 million years. The GRBs are indeed the most powerful events since the Big Bang known in the Universe, cf. ESO PR 08/99 and ESO PR 20/00 . During the past years circumstantial evidence has mounted that GRBs signal the collapse of massive stars. This was originally based on the probable association of one unusual gamma-ray burst with a supernova ("SN 1998bw", also discovered with ESO telescopes, cf. ESO PR 15/98 ). More clues have surfaced since, including the association of GRBs with regions of massive star-formation in distant galaxies, tantalizing evidence of supernova-like light-curve "bumps" in the optical afterglows of some earlier bursts, and spectral signatures from freshly synthesized elements, observed by X-ray observatories. VLT observations of GRB 030329 ESO PR Photo 17a/03 ESO PR Photo 17a/03 [Preview - JPEG: 588 x 400 pix - 61k [Normal - JPEG: 1176 x 800 pix - 688k] ESO PR Photo 17b/03 ESO PR Photo 17b/03 [Preview - JPEG: 400 x 509 pix - 52k [Normal - JPEG: 800 x 1018 pix - 288k] Captions : PR Photo 17a/03 is reproduced from a CCD-exposure, obtained with the FORS 1 and 2 multi-mode instruments at the 8.2-m VLT telescopes. It shows the fading image of the optical afterglow of GRB 030329 , as seen on April 3 (four days after the GRB event) and May 1, 2003. PR Photo 17b/03 displays a series of VLT-FORS-spectra, showing the spectral evolution of the hypernova (designated SN 2003dh [2]) underlying the gamma-ray burst GRB 030329 (black curves). The red-dotted spectra are those of an earlier, nearby hypernova, SN 1998bw , observed with various ESO telescopes. The elapsed time (days in the rest frame of the object) since the explosion is indicated. There is a striking similarity between the spectra of the two hypernovae, also in their evolution with time. This allowed a precise dating of the explosion of the hypernova underlying GRB 030329. On March 29, 2003 (at exactly 11:37:14.67 hrs UT) NASA's High Energy Transient Explorer (HETE-II) detected a very bright gamma-ray burst. Following identification of the "optical afterglow" by a 40-inch telescope at the Siding Spring Observatory (Australia), the redshift of the burst [3] was determined as 0.1685 by means of a high-dispersion spectrum obtained with the UVES spectrograph at the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile). The corresponding distance is about 2,650 million light-years. This is the nearest normal GRB ever detected, therefore providing the long-awaited opportunity to test the many hypotheses and models which have been proposed since the discovery of the first GRBs in the late 1960's. With this specific aim, the ESO-lead team of astronomers [1] now turned to two other powerful instruments at the ESO Very Large Telescope (VLT), the multi-mode FORS1 and FORS2 camera/spectrographs. Over a period of one month, until May 1, 2003, spectra of the fading object were obtained at regular rate, securing a unique set of observational data that documents the physical changes in the remote object in unsurpassed detail. The hypernova connection Based on a careful study of these spectra, the astronomers are now presenting their interpretation of the GRB 030329 event in a research paper appearing in the international journal "Nature" on Thursday, June 19. Under the prosaic title "A very energetic supernova associated with the gamma-ray burst of 29 March 2003", no less than 27 authors from 17 research institutes, headed by Danish astronomer Jens Hjorth conclude that there is now irrefutable evidence of a direct connection between the GRB and the "hypernova" explosion of a very massive, highly evolved star. This is based on the gradual "emergence" with time of a supernova-type spectrum, revealing the extremely violent explosion of a star. With velocities well in excess of 30,000 km/sec (i.e., over 10% of the velocity of light), the ejected material is moving at record speed, testifying to the enormous power of the explosion. Hypernovae are rare events and they are probably caused by explosion of stars of the so-called "Wolf-Rayet" type [4]. These WR-stars were originally formed with a mass above 25 solar masses and consisted mostly of hydrogen. Now in their WR-phase, having stripped themselves of their outer layers, they consist almost purely of helium, oxygen and heavier elements produced by intense nuclear burning during the preceding phase of their short life. " We have been waiting for this one for a long, long time ", says Jens Hjorth , " this GRB really gave us the missing information. From these very detailed spectra, we can now confirm that this burst and probably other long gamma-ray bursts are created through the core collapse of massive stars. Most of the other leading theories are now unlikely. " A "type-defining event" His colleague, ESO-astronomer Palle Møller , is equally content: " What really got us at first was the fact that we clearly detected the supernova signatures already in the first FORS-spectrum taken only four days after the GRB was first observed - we did not expect that at all. As we were getting more and more data, we realised that the spectral evolution was almost completely identical to that of the hypernova seen in 1998. The similarity of the two then allowed us to establish a very precise timing of the present supernova event ". The astronomers determined that the hypernova explosion (designated SN 2003dh [2]) documented in the VLT spectra and the GRB-event observed by HETE-II must have occurred at very nearly the same time. Subject to further refinement, there is at most a difference of 2 days, and there is therefore no doubt whatsoever, that the two are causally connected. " Supernova 1998bw whetted our appetite, but it took 5 more years before we could confidently say, we found the smoking gun that nailed the association between GRBs and SNe " adds Chryssa Kouveliotou of NASA. " GRB 030329 may well turn out to be some kind of 'missing link' for GRBs. " In conclusion, GRB 030329 was a rare "type-defining" event that will be recorded as a watershed in high-energy astrophysics . What really happened on March 29 (or 2,650 million years ago)? Here is the complete story about GRB 030329, as the astronomers now read it. Thousands of years prior to this explosion, a very massive star, running out of hydrogen fuel, let loose much of its outer envelope, transforming itself into a bluish Wolf-Rayet star [3]. The remains of the star contained about 10 solar masses worth of helium, oxygen and heavier elements. In the years before the explosion, the Wolf-Rayet star rapidly depleted its remaining fuel. At some moment, this suddenly triggered the hypernova/gamma-ray burst event. The core collapsed, without the outer part of the star knowing. A black hole formed inside, surrounded by a disk of accreting matter. Within a few seconds, a jet of matter was launched away from that black hole. The jet passed through the outer shell of the star and, in conjunction with vigorous winds of newly formed radioactive nickel-56 blowing off the disk inside, shattered the star. This shattering, the hypernova, shines brightly because of the presence of nickel. Meanwhile, the jet plowed into material in the vicinity of the star, and created the gamma-ray burst which was recorded some 2,650 million years later by the astronomers on Earth. The detailed mechanism for the production of gamma rays is still a matter of debate but it is either linked to interactions between the jet and matter previously ejected from the star, or to internal collisions inside the jet itself. This scenario represents the "collapsar" model, introduced by American astronomer Stan Woosley (University of California, Santa Cruz) in 1993 and a member of the current team, and best explains the observations of GRB 030329. " This does not mean that the gamma-ray burst mystery is now solved ", says Woosley . " We are confident now that long bursts involve a core collapse and a hypernova, likely creating a black hole. We have convinced most skeptics. We cannot reach any conclusion yet, however, on what causes the short gamma-ray bursts, those under two seconds long ."

Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. IV. Two bulge populations

NASA Astrophysics Data System (ADS)

Bensby, T.; Adén, D.; Meléndez, J.; Gould, A.; Feltzing, S.; Asplund, M.; Johnson, J. A.; Lucatello, S.; Yee, J. C.; Ramírez, I.; Cohen, J. G.; Thompson, I.; Bond, I. A.; Gal-Yam, A.; Han, C.; Sumi, T.; Suzuki, D.; Wada, K.; Miyake, N.; Furusawa, K.; Ohmori, K.; Saito, To.; Tristram, P.; Bennett, D.

2011-09-01

Based on high-resolution (R ≈ 42 000 to 48 000) and high signal-to-noise (S/N ≈ 50 to 150) spectra obtained with UVES/VLT, we present detailed elemental abundances (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba) and stellar ages for 12 new microlensed dwarf and subgiant stars in the Galactic bulge. Including previous microlensing events, the sample of homogeneously analysed bulge dwarfs has now grown to 26. The analysis is based on equivalent width measurements and standard 1-D LTE MARCS model stellar atmospheres. We also present NLTE Li abundances based on line synthesis of the 7Li line at 670.8 nm. The results from the 26 microlensed dwarf and subgiant stars show that the bulge metallicity distribution (MDF) is double-peaked; one peak at [Fe/H] ≈ -0.6 and one at [Fe/H] ≈ + 0.3, and with a dearth of stars around solar metallicity. This is in contrast to the MDF derived from red giants in Baade's window, which peaks at this exact value. A simple significance test shows that it is extremely unlikely to have such a gap in the microlensed dwarf star MDF if the dwarf stars are drawn from the giant star MDF. To resolve this issue we discuss several possibilities, but we can not settle on a conclusive solution for the observed differences. We further find that the metal-poor bulge dwarf stars arepredominantly old with ages greater than 10 Gyr, while the metal-rich bulge dwarf stars show a wide range of ages. The metal-poor bulge sample is very similar to the Galactic thick disk in terms of average metallicity, elemental abundance trends, and stellar ages. Speculatively, the metal-rich bulge population might be the manifestation of the inner thin disk. If so, the two bulge populations could support the recent findings, based on kinematics, that there are no signatures of a classical bulge and that the Milky Way is a pure-disk galaxy. Also, recent claims of a flat IMF in the bulge based on the MDF of giant stars may have to be revised based on the MDF and abundance trends probed by our microlensed dwarf stars. Based on observations made with the European Southern Observatory telescopes (84.B-0837, 85.B-0399, and 86.B-0757). This paper also includes data gathered with the 6.5 m Magellan Telescopes located at the Las Campanas Observatory, Chile, and data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration.Tables 4 and 5 are available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A134

Data fusion and photometric restoration

NASA Astrophysics Data System (ADS)

Pirzkal, Norbert; Hook, Richard N.

2001-11-01

The current generation of 8-10m optical ground-based telescopes have a symbiotic relationship with space telescopes. For direct imaging in the optical the former can collect photons relatively cheaply but the latter can still achieve, even in the era of adaptive optics, significantly higher spatial resolution, point-spread function stability and astrometric fidelity over fields of a few arcminutes. The large archives of HST imaging already in place, when combined with the ease of access to ground-based data afforded by the virtual observatory currently under development, will make space-ground data fusion a powerful tool for the future. We describe a photometric image restoration method that we have developed which allows the efficient and accurate use of high-resolution space imaging of crowded fields to extract high quality photometry from very crowded ground-based images. We illustrate the method using HST and ESO VLT/FORS imaging of a globular cluster and demonstrate quantitatively the photometric measurements quality that can achieved using the data fusion approach instead of just using data from just one telescope. This method can handle most of the common difficulties encountered when attempting this problem such as determining the geometric mapping to the requisite precision, deriving the PSF and the background.

Spectroscopic Characterisation of Microlensing Events: Towards a New Interpretation of OGLE-2011-BLG-0417

NASA Technical Reports Server (NTRS)

Santerne, A.; Beaulieu, J.-P.; Rojas Ayala, B.; Boisse, I.; Schlawin, E.; Almenara, J.-M.; Batista, V.; Bennett, D.; Diaz, R. F.; Figueira, P.;

Another Look at an Enigmatic New World

NASA Astrophysics Data System (ADS)

2005-02-01

VLT NACO Performs Outstanding Observations of Titan's Atmosphere and Surface On January 14, 2005, the ESA Huygens probe arrived at Saturn's largest satellite, Titan. After a faultless descent through the dense atmosphere, it touched down on the icy surface of this strange world from where it continued to transmit precious data back to the Earth. Several of the world's large ground-based telescopes were also active during this exciting event, observing Titan before and near the Huygens encounter, within the framework of a dedicated campaign coordinated by the members of the Huygens Project Scientist Team. Indeed, large astronomical telescopes with state-of-the art adaptive optics systems allow scientists to image Titan's disc in quite some detail. Moreover, ground-based observations are not restricted to the limited period of the fly-by of Cassini and landing of Huygens. They hence complement ideally the data gathered by this NASA/ESA mission, further optimising the overall scientific return. A group of astronomers [1] observed Titan with ESO's Very Large Telescope (VLT) at the Paranal Observatory (Chile) during the nights from 14 to 16 January, by means of the adaptive optics NAOS/CONICA instrument mounted on the 8.2-m Yepun telescope [2]. The observations were carried out in several modes, resulting in a series of fine images and detailed spectra of this mysterious moon. They complement earlier VLT observations of Titan, cf. ESO Press Photos 08/04 and ESO Press Release 09/04. The highest contrast images ESO PR Photo 04a/05 ESO PR Photo 04a/05 Titan's surface (NACO/VLT) [Preview - JPEG: 400 x 712 pix - 64k] [Normal - JPEG: 800 x 1424 pix - 524k] ESO PR Photo 04b/05 ESO PR Photo 04b/05 Map of Titan's Surface (NACO/VLT) [Preview - JPEG: 400 x 651 pix - 41k] [Normal - JPEG: 800 x 1301 pix - 432k] Caption: ESO PR Photo 04a/05 shows Titan's trailing hemisphere [3] with the Huygens landing site marked as an "X". The left image was taken with NACO and a narrow-band filter centred at 2 microns. On the right is the NACO/SDI image of the same location showing Titan's surface through the 1.6 micron methane window. A spherical projection with coordinates on Titan is overplotted. ESO PR Photo 04b/05 is a map of Titan taken with NACO at 1.28 micron (a methane window allowing it to probe down to the surface). On the leading side of Titan, the bright equatorial feature ("Xanadu") is dominating. On the trailing side, the landing site of the Huygens probe is indicated. ESO PR Photo 04c/05 ESO PR Photo 04c/05 Titan, the Enigmatic Moon, and Huygens Landing Site (NACO-SDI/VLT and Cassini/ISS) [Preview - JPEG: 400 x 589 pix - 40k] [Normal - JPEG: 800 x 1178 pix - 290k] Caption: ESO PR Photo 04c/05 is a comparison between the NACO/SDI image and an image taken by Cassini/ISS while approaching Titan. The Cassini image shows the Huygens landing site map wrapped around Titan, rotated to the same position as the January NACO SDI observations. The yellow "X" marks the landing site of the ESA Huygens probe. The Cassini/ISS image is courtesy of NASA, JPL, Space Science Institute (see http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=36222). The coloured lines delineate the regions that were imaged by Cassini at differing resolutions. The lower-resolution imaging sequences are outlined in blue. Other areas have been specifically targeted for moderate and high resolution mosaicking of surface features. These include the site where the European Space Agency's Huygens probe has touched down in mid-January (marked with the yellow X), part of the bright region named Xanadu (easternmost extent of the area covered), and a boundary between dark and bright regions. ESO PR Photo 04d/05 ESO PR Photo 04d/05 Evolution of the Atmosphere of Titan (NACO/VLT) [Preview - JPEG: 400 x 902 pix - 40k] [Normal - JPEG: 800 x 1804 pix - 320k] Caption: ESO PR Photo 04d/05 is an image of Titan's atmosphere at 2.12 microns as observed with NACO on the VLT at three different epochs from 2002 till now. Titan's atmosphere exhibits seasonal and meteorological changes which can clearly be seen here : the North-South asymmetry - indicative of changes in the chemical composition in one pole or the other, depending on the season - is now clearly in favour of the North pole. Indeed, the situation has reversed with respect to a few years ago when the South pole was brighter. Also visible in these images is a bright feature in the South pole, found to be presently dimming after having appeared very bright from 2000 to 2003. The differences in size are due to the variation in the distance to Earth of Saturn and its planetary system. The new images show Titan's atmosphere and surface at various near-infrared spectral bands. The surface of Titan's trailing side is visible in images taken through narrow-band filters at wavelengths 1.28, 1.6 and 2.0 microns. They correspond to the so-called "methane windows" which allow to peer all the way through the lower Titan atmosphere to the surface. On the other hand, Titan's atmosphere is visible through filters centred in the wings of these methane bands, e.g. at 2.12 and 2.17 microns. Eric Gendron of the Paris Observatory in France and leader of the team, is extremely pleased: "We believe that some of these images are the highest-contrast images of Titan ever taken with any ground-based or earth-orbiting telescope." The excellent images of Titan's surface show the location of the Huygens landing site in much detail. In particular, those centred at wavelength 1.6 micron and obtained with the Simultaneous Differential Imager (SDI) on NACO [4] provide the highest contrast and best views. This is firstly because the filters match the 1.6 micron methane window most accurately. Secondly, it is possible to get an even clearer view of the surface by subtracting accurately the simultaneously recorded images of the atmospheric haze, taken at wavelength 1.625 micron. The images show the great complexity of Titan's trailing side, which was earlier thought to be very dark. However, it is now obvious that bright and dark regions cover the field of these images. The best resolution achieved on the surface features is about 0.039 arcsec, corresponding to 200 km on Titan. ESO PR Photo 04c/04 illustrates the striking agreement between the NACO/SDI image taken with the VLT from the ground and the ISS/Cassini map. The images of Titan's atmosphere at 2.12 microns show a still-bright south pole with an additional atmospheric bright feature, which may be clouds or some other meteorological phenomena. The astronomers have followed it since 2002 with NACO and notice that it seems to be fading with time. At 2.17 microns, this feature is not visible and the north-south asymmetry - also known as "Titan's smile" - is clearly in favour in the north. The two filters probe different altitude levels and the images thus provide information about the extent and evolution of the north-south asymmetry. Probing the composition of the surface ESO PR Photo 04e/05 ESO PR Photo 04e/05 Spectrum of Two Regions on Titan (NACO/VLT) [Preview - JPEG: 400 x 623 pix - 44k] [Normal - JPEG: 800 x 1246 pix - 283k] Caption: ESO PR Photo 04e/05 represents two of the many spectra obtained on January 16, 2005 with NACO and covering the 2.02 to 2.53 micron range. The blue spectrum corresponds to the brightest region on Titan's surface within the slit, while the red spectrum corresponds to the dark area around the Huygens landing site. In the methane band, the two spectra are equal, indicating a similar atmospheric content; in the methane window centred at 2.0 microns, the spectra show differences in brightness, but are in phase. This suggests that there is no real variation in the composition beyond different atmospheric mixings. ESO PR Photo 04f/05 ESO PR Photo 04f/05 Imaging Titan with a Tunable Filter (NACO Fabry-Perot/VLT) [Preview - JPEG: 400 x 718 pix - 44k] [Normal - JPEG: 800 x 1435 pix - 326k] Caption: ESO PR Photo 04f/05 presents a series of images of Titan taken around the 2.0 micron methane window probing different layers of the atmosphere and the surface. The images are currently under thorough processing and analysis so as to reveal any subtle variations in wavelength that could be indicative of the spectral response of the various surface components, thus allowing the astronomers to identify them. Because the astronomers have also obtained spectroscopic data at different wavelengths, they will be able to recover useful information on the surface composition. The Cassini/VIMS instrument explores Titan's surface in the infrared range and, being so close to this moon, it obtains spectra with a much better spatial resolution than what is possible with Earth-based telescopes. However, with NACO at the VLT, the astronomers have the advantage of observing Titan with considerably higher spectral resolution, and thus to gain more detailed spectral information about the composition, etc. The observations therefore complement each other. Once the composition of the surface at the location of the Huygens landing is known from the detailed analysis of the in-situ measurements, it should become possible to learn the nature of the surface features elsewhere on Titan by combining the Huygens results with more extended cartography from Cassini as well as from VLT observations to come. More information Results on Titan obtained with data from NACO/VLT are in press in the journal Icarus ("Maps of Titan's surface from 1 to 2.5 micron" by A. Coustenis et al.). Previous images of Titan obtained with NACO and with NACO/SDI are accessible as ESO PR Photos 08/04 and ESO PR Photos 11/04. See also these Press Releases for additional scientific references.

The Sky Through Three Giant Eyes

NASA Astrophysics Data System (ADS)

2007-02-01

AMBER Instrument on VLT Delivers a Wealth of Results The ESO Very Large Telescope Interferometer, which allows astronomers to scrutinise objects with a precision equivalent to that of a 130-m telescope, is proving itself an unequalled success every day. One of the latest instruments installed, AMBER, has led to a flurry of scientific results, an anthology of which is being published this week as special features in the research journal Astronomy & Astrophysics. ESO PR Photo 06a/07 ESO PR Photo 06a/07 The AMBER Instrument "With its unique capabilities, the VLT Interferometer (VLTI) has created itself a niche in which it provide answers to many astronomical questions, from the shape of stars, to discs around stars, to the surroundings of the supermassive black holes in active galaxies," says Jorge Melnick (ESO), the VLT Project Scientist. The VLTI has led to 55 scientific papers already and is in fact producing more than half of the interferometric results worldwide. "With the capability of AMBER to combine up to three of the 8.2-m VLT Unit Telescopes, we can really achieve what nobody else can do," added Fabien Malbet, from the LAOG (France) and the AMBER Project Scientist. Eleven articles will appear this week in Astronomy & Astrophysics' special AMBER section. Three of them describe the unique instrument, while the other eight reveal completely new results about the early and late stages in the life of stars. ESO PR Photo 06b/07 ESO PR Photo 06b/07 The Inner Winds of Eta Carinae The first results presented in this issue cover various fields of stellar and circumstellar physics. Two papers deal with very young solar-like stars, offering new information about the geometry of the surrounding discs and associated outflowing winds. Other articles are devoted to the study of hot active stars of particular interest: Alpha Arae, Kappa Canis Majoris, and CPD -57o2874. They provide new, precise information about their rotating gas envelopes. An important new result concerns the enigmatic object Eta Carinae. Using AMBER with its high spatial and spectral resolution, it was possible to zoom into the very heart of this very massive star. In this innermost region, the observations are dominated by the extremely dense stellar wind that totally obscures the underlying central star. The AMBER observations show that this dense stellar wind is not spherically symmetric, but exhibits a clearly elongated structure. Overall, the AMBER observations confirm that the extremely high mass loss of Eta Carinae's massive central star is non-spherical and much stronger along the poles than in the equatorial plane. This is in agreement with theoretical models that predict such an enhanced polar mass-loss in the case of rapidly rotating stars. ESO PR Photo 06c/07 ESO PR Photo 06c/07 RS Ophiuchi in Outburst Several papers from this special feature focus on the later stages in a star's life. One looks at the binary system Gamma 2 Velorum, which contains the closest example of a star known as a Wolf-Rayet. A single AMBER observation allowed the astronomers to separate the spectra of the two components, offering new insights in the modeling of Wolf-Rayet stars, but made it also possible to measure the separation between the two stars. This led to a new determination of the distance of the system, showing that previous estimates were incorrect. The observations also revealed information on the region where the winds from the two stars collide. The famous binary system RS Ophiuchi, an example of a recurrent nova, was observed just 5 days after it was discovered to be in outburst on 12 February 2006, an event that has been expected for 21 years. AMBER was able to detect the extension of the expanding nova emission. These observations show a complex geometry and kinematics, far from the simple interpretation of a spherical fireball in extension. AMBER has detected a high velocity jet probably perpendicular to the orbital plane of the binary system, and allowed a precise and careful study of the wind and the shockwave coming from the nova. The stream of results from the VLTI and AMBER is no doubt going to increase in the coming years with the availability of new functionalities. "In addition to the 8.2-m Unit Telescopes, the VLTI can also combine the light from up to 4 movable 1.8-m Auxiliary Telescopes. AMBER fed by three of these AT's will be offered to the user community as of April this year, and from October we will also make FINITO available," said Melnick. "This 'fringe-tracking' device allows us to stabilise changes in the atmospheric conditions and thus to substantially improve the efficiency of the observations. By effectively 'freezing' the interferometric fringes, FINITO allows astronomers to significantly increase the exposure times." The Astronomy & Astrophysics special feature (volume 464 - March II 2007) on AMBER first results includes 11 articles. They are freely available on the A&A web site. More Information The AMBER consortium, led by Romain Petrov (Nice, France), includes researchers from the Laboratoire d'Astrophysique de Grenoble (France), Laboratoire d'Astrophysique Universitaire de Nice (France), Max-Planck Institut für Radioastronomie (Bonn, Germany), INAF-Osservatorio Astrofisico di Arcetri (Italy), and the Observatoire de la Côte d'Azur (Nice, France). In March 2004, the first on-line tests of AMBER (Astronomical Multiple BEam Recombiner) were completed, when astronomers combined the two beams of light from the southern star Theta Centauri from two test 40-cm aperture telescopes (ESO 07/04). It was later used to combine light from two, then three Unit Telescopes of ESO's VLT and light from the Auxiliary Telescopes. AMBER is part of the VLT Interferometer (VLTI) and completes the planned set of first-generation instruments for this facility. It continues the success story of the interferometric mode of the VLT, following the unique initial scientific results obtained by the VINCI and MIDI instruments, the installation of the four MACAO adaptive optics systems and the recent arrival of the last of the four 1.8-m Auxiliary Telescopes at Paranal. The principle of the interferometric technique is to combine the light collected by two or more telescopes. The greater the distance between the telescopes, the more details one can detect. For the VLTI, this distance can be up to 200 metres, providing observers with milli-arcsecond spatial resolution. With such a high spatial resolution, one would be able to distinguish between the headlights of a car located on the Moon. In addition, AMBER also provides astronomers with spectroscopic measurements, allowing the structure and the physics of the source to be constrained by comparing the measures at different wavelengths. AMBER combines the light beams from three telescopes - this is a world first for large telescopes such as the VLT. The ability to combine three beams, rather than just two as in a conventional interferometer, provides a substantial increase in the efficiency of observations, permitting astronomers to obtain three baselines simultaneously instead of one. The combination of these three baselines also permits the computation of the so-called closure phase, an important mathematical quantity that can be used in imaging applications. The AMBER instrument is mounted on a 4.2 x 1.5-m precision optical table, placed in the VLT Interferometric Laboratory at the top of the Paranal mountain. The total shipping weight of the instrument and its extensive associated electronics was almost 4 tons. Two of the results discussed here were already presented as ESO press releases in ESO 29/05 and 35/06.

Industrial solutions trends for the control of HiRes spectrograph@E-ELT

NASA Astrophysics Data System (ADS)

Di Marcantonio, P.; Baldini, V.; Calderone, G.; Cirami, R.; Coretti, I.; Cristiani, S.

Starting a few years ago, ESO initiated a number of projects aiming to explore the possible adoption of industrial standards and commercial off-the-shelf components (COTS) for the control of future VLT and E-ELT instrumentations. In this context, ESPRESSO, the next generation high-stability spectrograph for the VLT and to a certain extent, a precursor of HiRes, has adopted since the preliminary design phase those solutions. Based on the ESPRESSO experience and taking into account the requirements inferred from the preliminary Hi-Res studies in terms of both high-level operations as well as low-level control, I will present in this paper the current proposal for the HiRes hardware architecture.

Mapping of Ozone on Mars at Infrared Wavelengths Using Crires at VLT

NASA Astrophysics Data System (ADS)

Radeva, Y. L.; Mumma, M. J.; Villanueva, G.; Novak, R.; Hartogh, P.; Encrenaz, T.; Kaufl, H.; Smette, A.

2010-12-01

We present spatially resolved maps of ozone and water on Mars, acquired on 21 August 2009 using the ultra-high resolution infrared spectrometer CRIRES at ESO’s VLT (Paranal, Chile). On Mars, the season was mid-summer in the South (Ls = 325) and the latitudinal resolution was 10 degrees FWHM at disk center. Ozone is produced by recombination of photochemically produced O and O2. It is destroyed by UV photolysis (with O2 (a1Dg) as a principal product) but also by reaction with odd hydrogen species (especially, H - a product of H2O vapor photolysis). Thus, simultaneous measurements of water and ozone can test this relationship. We quantified ozone using spectral lines (near 1.27 mm) of O2 (a1Dg). The emission from O2 (a1Dg) serves as a tracer for O3 above 20 km, since at lower altitudes collisions with CO2 quench the excited O2 (a1Dg) molecules. We confirmed the vertical location of the O2 (a1Dg) emission by extracting rotational temperatures from line-by-line ratios, and comparing them with standard vertical temperature profiles for this season and location(s). On the same night, we also obtained 2-D (lat-long) maps of Martian water from multiple H2O lines detected in the 3.3 mm region. We compare our retrieved distributions for ozone (latitude and altitude) with predictions of Lefevre et al. [I] based on their comprehensive 3-D circulation and photochemical model for the Martian atmosphere. Acknowledgements: This work was funded by NASA’s R&A Programs in Astrobiology (344-53-51), Planetary Astronomy (344-32-51-96), and Planetary Atmospheres (NNX09AB65G). We gratefully acknowledge the Director and staff of the European Southern Observatory, for supporting these observations. References: [I] Lefevre et al. (2004), J. of Geophys. Res. 109, E07004

A multi-wavelength database of water vapor in planet-forming regions

NASA Astrophysics Data System (ADS)

Pontoppidan, Klaus

The inner few astronomical units of gas-rich protoplanetary disk are environments characterized by a rich and active gaseous chemistry. Primitive material left over from the formation of our own Solar System has for a long time yielded tantalizing clues to a heterogenous nebula with intricate dynamical, thermal and chemical structure that ultimately led to a great diversity in the planets and planetesimals of the Solar System. The discovery of a rich chemistry in protoplanetary disks via a forest of strong 3-40 micron molecular emission lines (H2O, OH, CO2, HCN, C2H2,...) allows us for the first time to investigate chemical diversity in other planet-forming environmments (Salyk et al. 2008; Carr & Najita 2008). Further efforts, supported by the Origins program, has established that this molecular forest is seen in the disks surrounding most young solar- type stars (Pontoppidan et al. 2010). We propose a 3-year program to analyze our growing multi-wavelength database of observations of water, OH and organic molecules in the surfaces of protoplanetary disks. The database includes high (R~25,000-100,000) and medium resolution (R~600-3000) 3- 200 micron spectra from a wide range of facilities (Keck-NIRSPEC, VLT-CRIRES, Spitzer-IRS, VLT-VISIR, Gemini-Michelle and Herschel-PACS). Our previous efforts have focused on demonstrating feasibility for observing water and other molecules in planet-forming regions, building statistics to show that the molecular forest is ubiquitous in disks around low-mass and solar-type stars and taking the first steps in understanding the implied chemical abundances. Now, as the next logical step, we will combine multi- wavelength data from our unique multi-wavelength database to map the radial distribution of, in particular, water and its derivatives. 1) We will use both line profile information from the high-resolution spectra, as well as line strengths, from a combination of high and low temperature lines to constrain the radial abundance of water vapor in the emitting surfaces of disks. Despite high water abundances inside ~1 AU, there is evidence that the disk surfaces are strongly depleted in water both from the gas and ice phases, by as much as 6 orders of magnitude, beyond 1-2 AU. This may be due to the settling of icy grains as part of the formation of icy planetesimals (Meijerink et al. 2009; Bergin et al. 2010). We wish to quantify the depletion factor and establish whether this is a common property of all protoplanetary disks. 2) We will pursue critical new datasets using upcoming observational facilities, including spectrally resolved rotational water lines in the mid-infrared. VLT-VISIR, with which we have successfully detected water lines at high resolution, is undergoing a significant hardware upgrade with a planned commissioning around January 2012. The upgrade includes a much larger and more sensitive detector based on technology developed for JWST-MIRI, which is expected to increase its efficiency by 1-2 orders of magnitude. On a longer time scale, SOFIA-EXES, JWST-NIRSpec and MIRI will become essential instruments for moving this field forward. Pontoppidan is a JWST-NIRSpec instrument scientist at STScI. 3) We will search for variability of water lines on time scales of months and compare them to variation already seen in CO gas to investigate its origin. One intriguing possibility is dynamical interaction with protoplanets. The proposed research is highly relevant for the Origins of Solar Systems program as described in the solicitation document. It falls into the categories dealing with "Observations related to understanding the formation and evolution of planetary systems" and "Studies of chemical processes related to the formation of planetary systems."

A multi-wavelength database of water vapor in planet-forming regions

NASA Astrophysics Data System (ADS)

Pontoppidan, Klaus

The inner few astronomical units of gas-rich protoplanetary disk are environments characterized by a rich and active gaseous chemistry. Primitive material left over from the formation of our own Solar System has for a long time yielded tantalizing clues to a heterogenous nebula with intricate dynamical, thermal and chemical structure that ultimately led to a great diversity in the planets and planetesimals of the Solar System. The discovery of a rich chemistry in protoplanetary disks via a forest of strong 3-40 micron molecular emission lines (H2O, OH, CO2, HCN, C2H2,...) allows us for the first time to investigate chemical diversity in other planet-forming environmments (Salyk et al. 2008; Carr & Najita 2008). Further efforts, supported by the Origins program, has established that this molecular forest is seen in the disks surrounding most young solar- type stars (Pontoppidan et al. 2010). We propose a 3-year program to analyze our growing multi-wavelength database of observations of water, OH and organic molecules in the surfaces of protoplanetary disks. The database includes high (R~25,000-100,000) and medium resolution (R~600-3000) 3- 200 micron spectra from a wide range of facilities (Keck-NIRSPEC, VLT-CRIRES, Spitzer-IRS, VLT-VISIR, Gemini-Michelle and Herschel-PACS). Our previous efforts have focused on demonstrating feasibility for observing water and other molecules in planet-forming regions, building statistics to show that the molecular forest is ubiquitous in disks around low-mass and solar-type stars and taking the first steps in understanding the implied chemical abundances. Now, as the next logical step, we will combine multi- wavelength data from our unique multi-wavelength database to map the radial distribution of, in particular, water and its derivatives. 1) Â We will use both line profile information from the high-resolution spectra, as well as line strengths, from a combination of high and low temperature lines to constrain the radial abundance of water vapor in the emitting surfaces of disks. Despite high water abundances inside ~1 AU, there is evidence that the disk surfaces are strongly depleted in water both from the gas and ice phases, by as much as 6 orders of magnitude, beyond 1-2 AU. This may be due to the settling of icy grains as part of the formation of icy planetesimals (Meijerink et al. 2009; Bergin et al. 2010). We wish to quantify the depletion factor and establish whether this is a common property of all protoplanetary disks. 2) Â We will pursue critical new datasets using upcoming observational facilities, including spectrally resolved rotational water lines in the mid-infrared. VLT-VISIR, with which we have successfully detected water lines at high resolution, is undergoing a significant hardware upgrade with a planned commissioning around January 2012. The upgrade includes a much larger and more sensitive detector based on technology developed for JWST-MIRI, which is expected to increase its efficiency by 1-2 orders of magnitude. On a longer time scale, SOFIA-EXES, JWST-NIRSpec and MIRI will become essential instruments for moving this field forward. Pontoppidan is a JWST-NIRSpec instrument scientist at STScI. 3) Â We will search for variability of water lines on time scales of months and compare them to variation already seen in CO gas to investigate its origin. One intriguing possibility is dynamical interaction with protoplanets. The proposed research is highly relevant for the Origins of Solar Systems program as described in the solicitation document. It falls into the categories dealing with "Observations related to understanding the formation and evolution of planetary systems" and "Studies of chemical processes related to the formation of planetary systems."

Data Flow System operations: from the NTT to the VLT

NASA Astrophysics Data System (ADS)

Silva, David R.; Leibundgut, Bruno; Quinn, Peter J.; Spyromilio, Jason; Tarenghi, Massimo

1998-07-01

Science operations at the ESO very large telescope is scheduled to begin in April 1999. ESO is currently finalizing the VLT science operations plan. This plan describes the operations tasks and staffing needed to support both visitor and service mode operations. The Data Flow Systems (DFS) currently being developed by ESO will provide the infrastructure necessary for VLT science operations. This paper describes the current VLT science operations plan, first by discussing the tasks involved and then by describing the operations teams that have responsibility for those tasks. Prototypes of many of these operational concepts and tools have been in use at the ESO New Technology Telescope (NTT) since February 1997. This paper briefly summarizes the status of these prototypes and then discusses what operation lessons have been learned from the NTT experience and how they can be applied to the VLT.

Search with UVES and X-Shooter for signatures of the low-mass secondary in the post common-envelope binary AA Doradus

NASA Astrophysics Data System (ADS)

Hoyer, D.; Rauch, T.; Werner, K.; Hauschildt, P. H.; Kruk, J. W.

2015-06-01

Context. AA Dor is a close, totally eclipsing, post common-envelope binary with an sdOB-type primary star and an extremely low-mass secondary star, located close to the mass limit of stable central hydrogen burning. Within error limits, it may either be a brown dwarf or a late M-type dwarf. Aims: We aim to extract the secondary's contribution to the phase-dependent composite spectra. The spectrum and identified lines of the secondary decide on its nature. Methods: In January 2014, we measured the phase-dependent spectrum of AA Dor with X-Shooter over one complete orbital period. Since the secondary's rotation is presumable synchronized with the orbital period, its surface strictly divides into a day and night side. Therefore, we may obtain the spectrum of its cool side during its transit and of its hot, irradiated side close to its occultation. We developed the Virtual Observatory (VO) tool TLISA to search for weak lines of a faint companion in a binary system. We successfully applied it to the observations of AA Dor. Results: We identified 53 spectral lines of the secondary in the ultraviolet-blue, visual, and near-infrared X-Shooter spectra that are strongest close to its occultation. We identified 57 (20 additional) lines in available Ultraviolet and Visual Echelle Spectrograph (UVES) spectra from 2001. The lines are mostly from C ii-iii and O ii, typical for a low-mass star that is irradiated and heated by the primary. We verified the orbital period of P = 22 597.033201 ± 0.00007 s and determined the orbital velocity K_sec = 232.9+16.6-6.5 km s-1 of the secondary. The mass of the secondary is M_sec = 0.081+0.018-0.010 M_⊙ and, hence, it is not possible to reliably determine a brown dwarf or an M-type dwarf nature. Conclusions: Although we identified many emission lines of the secondary's irradiated surface, the resolution and signal-to-noise ratio of our UVES and X-Shooter spectra are not good enough to extract a good spectrum of the secondary's nonirradiated hemisphere. Based on observations collected at the European Southern Observatory, Chile, programs 066.D-1800 and 092.C-0692.Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer.Figures 2-5, 9, and Appendices are available in electronic form at http://www.aanda.org

Introducing CUBES: the Cassegrain U-band Brazil-ESO spectrograph

NASA Astrophysics Data System (ADS)

Bristow, Paul; Barbuy, Beatriz; Macanhan, Vanessa B.; Castilho, Bruno; Dekker, Hans; Delabre, Bernard; Diaz, Marcos; Gneiding, Clemens; Kerber, Florian; Kuntschner, Harald; La Mura, Giovanni; Reiss, Roland; Vernet, J.

2014-07-01

CUBES is a high-efficiency, medium-resolution (R ≃ 20, 000) spectrograph dedicated to the "ground based UV" (approximately the wavelength range from 300 to 400nm) destined for the Cassegrain focus of one of ESO's VLT unit telescopes in 2018/19. The CUBES project is a joint venture between ESO and Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG) at the Universidade de São Paulo and the Brazilian Laboratório Nacional de Astrofísica (LNA). CUBES will provide access to a wealth of new and relevant information for stellar as well as extra-galactic sources. Principle science cases include the study of heavy elements in metal-poor stars, the direct determination of carbon, nitrogen and oxygen abundances by study of molecular bands in the UV range and the determination of the Beryllium abundance as well as the study of active galactic nuclei and the inter-galactic medium. With a streamlined modern instrument design, high efficiency dispersing elements and UV-sensitive detectors, it will enable a significant gain in sensitivity over existing ground based medium-high resolution spectrographs enabling vastly increased sample sizes accessible to the astronomical community. We present here a brief overview of the project, introducing the science cases that drive the design and discussing the design options and technological challenges.

On the orbital period of the magnetic cataclysmic variable HU Aquarii

NASA Astrophysics Data System (ADS)

Vogel, J.; Schwope, A.; Schwarz, R.; Kanbach, G.; Dhillon, V. S.; Marsh, T. R.

2008-02-01

We present an analysis of ULTRACAM light curves of the magnetic cataclysmic variable HU Aquarii which were taken at the VLT in May 2005. Since the light curves were serendipitously obtained during a low state, they allowed us to determine the binary and the stellar parameters with high accuracy. The light curve was decomposed into the components originating from the accretion spot, the photosphere surrounding it and the white dwarf itself, which allowed us to extract the eclipse light curve for the pure white dwarf. Combined with high-time resolution observations with different instruments over a 12 year baseline it was possible to get exact eclipse timings of the white dwarf and thus establish a significant deviation from a linear ephemeris. If described by a quadratic term, the period decreases by -1.13×10-11 ss-1. Interpreting this change in period as a pure angular momentum loss (AML) effect, the rate of J˙ = -4.9×1035 erg is much too high to be explained by gravitational radiation alone.

The VLT Opening Symposium

NASA Astrophysics Data System (ADS)

1999-02-01

Scientists Meet in Antofagasta to Discuss Front-Line Astrophysics To mark the beginning of the VLT era, the European Southern Observatory is organizing a VLT Opening Symposium which will take place in Antofagasta (Chile) on 1-4 March 1999, just before the start of regular observations with the ESO Very Large Telescope on April 1, 1999. The Symposium occupies four full days and is held on the campus of the Universidad Catolica del Norte. It consists of plenary sessions on "Science in the VLT Era and Beyond" and three parallel Workshops on "Clusters of Galaxies at High Redshift" , "Star-way to the Universe" and "From Extrasolar Planets to Brown Dwarfs" . There will be many presentations of recent work at the major astronomical facilities in the world. The meeting provides a very useful forum to discuss the latest developments and, in this sense, contributes to the planning of future research with the VLT and other large telescopes. The symposium will be opened with a talk by the ESO Director General, Prof. Riccardo Giacconi , on "Paranal - an observatory for the 21st century". It will be followed by reports about the first scientific results from the main astronomical instruments on VLT UT1, FORS1 and ISAAC. The Symposium participants will see the VLT in operation during special visits to the Paranal Observatory. Press conferences are being arranged each afternoon to inform about the highlights of the conference. After the Symposium, there will be an Official Inauguration Ceremony at Paranal on 5 March Contributions from ESO ESO scientists will make several presentations at the Symposium. They include general reviews of various research fields as well as important new data and results from the VLT that show the great potential of this new astronomical facility. Some of the recent work is described in this Press Release, together with images and spectra of a large variety of objects. Note that all of these data will soon become publicly available via the VLT Archive. The text below summarizes the individual projects. Comprehensive texts with all photos and diagrammes are available in nine separate web documents ( ESO PR Photos 08/99 to 16/99 ) that may be accessed via the links at the top of each section. The degree of detail and level of complexity of the texts depend on the subject and the available materials. 1. Dwarf Galaxies in the Local Group ESO PR Photo 10a/99 ESO PR Photo 10a/99 The Antlia Galaxy (FORS1 colour composite) . Access full text and PR Photos 10a-d/99 In addition to large spiral galaxies like the Milky Way Galaxy, the Andromeda Galaxy and Messier 33, the Local Group of Galaxies contains many dwarf galaxies. The VLT has observed two of these, Antlia and NGC 6822 . Antlia is a low-surface brightness, spheroidal dwarf galaxy that was only discovered in 1997. While it contains a large amount of atomic hydrogen at its centre, no young stars are found, and it appears that most of its stars are old. This is unlike other dwarf galaxies in the Milky Way neighbourhood, as star formation is expected to occur within dense hydrogen clouds. Further observations will be necessary to understand this unusual characteristics. The VLT also obtained images of an irregular dwarf galaxy in the Local Group, NGC 6822, as well as spectra of some of its stars. This galaxy is of the "irregular" type and is situated at a distance of about 2 million light-years. A comparison of the spectra of supergiant stars in NGC 6822 shows that many spectral lines are much weaker than in stars of similar type in the Milky Way, but of similar strength as in stars in the Small Magellanic Cloud. This confirms an earlier finding that NGC 6822 has chemical composition (a lower "metallicity") that is different from what is observed in our Galaxy. 2. The Double Stellar Cluster NGC 1850 in the LMC ESO PR Photo 15/99 ESO PR Photo 15/99 NGC 1850 (FORS1 colour composite) . Access full text and PR Photo 15/99 NGC 1850 is a double cluster in the Large Magellanic Cloud, a satellite galaxy to the Milky Way Galaxy. This cluster is representative of a class of objects, young, globular-like stellar associations , that has no counterpart in our own Galaxy. The VLT images show faint nebulosity in this area, with filaments and various sharp "shocks". This offers support to the theory of supernova-induced star birth in the younger of the two clusters. It is estimated that about 1000 stars in the older of the clusters have exploded during the past 20 million years. 3. The Barred Galaxy NGC 1365 ESO PR Photo 08a/99 ESO PR Photo 08a/99 The Barred Galaxy NGC 1365 (FORS1 colour composite) . Access full text and PR Photos 08a-e/99 NGC 1365 is one of the most prominent "barred" galaxies in the sky. It is a supergiant galaxy and is a member of the Fornax Cluster of Galaxies, at a distance of about 60 million light-years. This galaxy has an intricate structure with a massive straight bar and two pronounced spiral arms. There are many dust lanes and emission nebulae in these and also a bright nuclear region at the center that may hide a black hole. Several images of NGC 1365 have recently been obtained with all three astronomical instruments, now installed at the VLT UT1. They show the overall structure of this magnificent galaxy, and also the fine details of the innermost region, close to the centre. An infrared ISAAC image penetrates deep into the obscuring dust clouds in this area. 4. The colours of NGC 1232 ESO PR Photo 13a/99 ESO PR Photo 13a/99 Differential (UV-B) image of NGC 1232 (FORS1) . Access full text and PR Photos 13a-b/99 NGC 1232 is a large spiral galaxy in the constellation Eridanus (The River). With a diameter of nearly 200,000 light-years, it is about twice the size of the Milky Way galaxy. The distance is about 100 million light-years, but the excellent optical quality of the VLT and FORS allows us to see an incredible wealth of details. Computer processed "colour-index images" have been prepared that show the "difference" between images of the galaxy, as seen in different wavebands. Since different types of objects have different brightness in different colours, this method is very useful to locate objects of a particular type and to obtain an overview of their distribution in the galaxy. The distribution of star-forming regions and dust lanes in NGC 1232 are shown on two such photos. 5. A Selection of ISAAC Spectra ESO PR Photo 11a/99 ESO PR Photo 11a/99 He I 1038 nm line in SN1987A (ISAAC spectrum) . Access full text and PR Photos 11a-c/99 Various observations were made with the ISAAC multi-mode instrument at the Nasmyth focus of VLT UT1 during the recent commissioning periods for this infrared multi-mode instrument. They impressively demonstrate the unique capabilities of this facility. The new data include several infrared spectra of faint objects with interesting features. A spectrum was obtained in the near-infrared region of the ring nebula around SN 1987A in the Large Magellanic Cloud. It consists of material blown off the progenitor star during its evolution. Of particular interest is a jet like structure in the dispersion direction which reveals the presence of a broad, blueshifted, HeI component which presumably originates in the shock ionized ejecta. Another spectrum shows emission features in two galaxies at redshift z = 0.6 [1] that allow the determination of a rotation curve at this large distance. The 1 - 2.5 µm infrared spectrum of the radio galaxy MRC0406 at z =2.42 is also included. 6. The Cluster of Galaxies MS1008.1-1224 ESO PR Photo 09b/99 ESO PR Photo 09b/99 Centre of the Cluster of Galaxies MS1008.1-122 (FORS1 colour composite) . Access full text and PR Photos 09a-b/99 The study of "Deep Fields" is becoming a common tool in astronomy. Among the various sky fields that have been selected for detailed investigation of the faint and distant objects therein, is the FORS Deep Field that will be observed during FORS1 "guaranteed time", available to astronomers from institutes that built this instrument. In preparation of this work, an imaging programme was carried out during the FORS1 Science Verification programme. Multicolour (UBVRI) deep images were obtained of the galaxy cluster MS1008.1-1224 , to be complemented with infrared (JHK) images with ISAAC of the cluster core. The redshift is z = 0.306 and many arclets from gravitational lensing are seen within the cluster area. Such observations serve many purposes, including the study of the distribution of mass and the associated gravitational field of the cluster, of individual cluster galaxies, and also of background objects whose images are amplified and distorted by gravitational lensing caused by the cluster. 7. Quasar Spectra ESO PR Photo 14a/99 ESO PR Photo 14c/99 Spectrum of Quasar at z = 5 Access full text and PR Photos 14a-c/99 The FORS1 multi-mode instrument is able to record images as well as spectra of even very distant objects. During the past months, data have been obtained that show the properties of some of the remotest known objects in the Universe. Three spectral tracings of very distant quasars are included, for which the redshifts have been determined as z = 3.11, 3.83 and 5.0. They were taken by the FORS Commissioning Team in September and December 1998 in the long-slit spectroscopy mode of FORS1. This instrument is very efficient; even for the most distant and faintest quasar, the exposure time was only 1 hour. All spectra show a wealth of details. 8. Spectrum of a Gravitationally Lensed Galaxy ESO PR Photo 16c/99 ESO PR Photo 16c/99 Spectrum of Gravitationally Lensed Galaxy at z = 3.23 (FORS1) . Access full text and PR Photos 16a-c/99 The galaxy cluster 1ES 0657-55 is located in the southern constellation Carina (The Keel), at redshift z = 0.29. It emits strong and very hot X-ray emission and has an asymmetric galaxy distribution, indicating a large mass and recent formation. Earlier images with the ESO NTT at La Silla have revealed the presence of a gravitational arc, i.e. a background galaxy at larger distance, whose image is strongly distorted by the gravitational field of this cluster. New images of this cluster have been obtained with FORS1 under good seeing conditions. They show that this arc is very thin and long. Other arcs and arclets are also visible. It was possible to obtain a spectrum of the arc. Several absorption lines are well visible and show that the arc is the highly distorted image of a young, background galaxy at redshift z = 3.23. 9. Spectra of Faint Primordial Objects ESO PR Photo 12d/99 ESO PR Photo 12d/99 Spectrum of Distant Galaxy EIS 107 at z = 3.92 (FORS1) . Access full text and PR Photos 12a-f/99 During the recent commissioning and science verification of FORS1, spectra were taken of several objects, thought to be high-redshift galaxies. These objects are extremely faint and their spectra can only be observed with very large telescopes like the VLT and a highly efficient spectrograph. The near-infrared (I) magnitudes of the objects studied during the present test observations ranged between 23.4 and 25.5, or between 10 and 65 million times fainter than what can be seen with the unaided eye. As predicted, a large fraction of the spectra obtained turned out to be those of extremely distant galaxies, in the redshift range between z = 2.8 - 4.0. Outlook These observations provide but a small demonstration of the great capability of the ESO VLT to provide front-line astronomical data. Many others will be discussed during the Symposium and contribute to the future planning of the best possible exploitation of this great new research facility. The first 8.2-m VLT Unit Telescope (UT1) with which the observations reported in this Press Release were made will soon be joined by UT2, for which "First Light" is expected shortly, cf. PR Photos 07/99. The first instrument to be mounted on this telescope will be UVES that will provide the capability of obtaining high-dispersion spectra; the next is FORS2. During the coming years, more instruments of different types and capabilities will become available on the four 8.2-m telescopes, together providing an unrivalled potential for astronomical investigations. Note: [1]: In astronomy, the redshift (z) denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a distant galaxy or quasar gives a direct estimate of the universal expansion (i.e. the `recession velocity'). Since this expansion rate increases with the distance, the velocity (and thus the redshift) is itself a function (the Hubble relation) of the distance to the object. The larger the distance, the longer it has taken the light from the object to reach us, and the larger is the "look-back" time, i.e. the fraction of the age of the Universe that has elapsed since the light we now receive, was emitted from the object. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory . Note also the comprehensive VLT Information site.

Little Brother Joins the Large Family

NASA Astrophysics Data System (ADS)

2006-12-01

On the night of 15 December 2006, the fourth and last-to-be-installed VLTI Auxiliary Telescope (AT4) obtained its 'First Light'. The first images demonstrate that AT4 will be able to deliver the excellent image quality already delivered by the first three ATs. It will soon join its siblings to perform routinely interferometric measurements. ESO PR Photo 51a/06 ESO PR Photo 51a/06 VLT Auxiliary Telescope The VLT is composed of four 8.2-m Unit Telescope (Antu, Kueyen, Melipal and Yepun). They have been progressively put into service together with a vast suite of the most advanced astronomical instruments and are operated every night in the year. Contrary to other large astronomical telescopes, the VLT was designed from the beginning with the use of interferometry as a major goal. The VLT Interferometer (VLTI) combines starlight captured by two or three 8.2- VLT Unit Telescopes, dramatically increasing the spatial resolution and showing fine details of a large variety of celestial objects. ESO PR Photo 51b/06 ESO PR Photo 51b/06 One AT Under the Sky However, most of the time the large telescopes are used for other research purposes. They are therefore only available for interferometric observations during a limited number of nights every year. Thus, in order to exploit the VLTI each night and to achieve the full potential of this unique setup, some other (smaller), dedicated telescopes were included into the overall VLT concept. These telescopes, known as the VLTI Auxiliary Telescopes (ATs), are mounted on tracks and can be placed at precisely defined "parking" observing positions on the observatory platform. From these positions, their light beams are fed into the same common focal point via a complex system of reflecting mirrors mounted in an underground system of tunnels. The Auxiliary Telescopes are real technological jewels. They are placed in ultra-compact enclosures, complete with all necessary electronics, an air conditioning system and cooling liquid for thermal control, compressed air for enclosure seals, a hydraulic plant for opening the dome shells, etc. Each AT is also fitted with a transporter that lifts the telescope and relocates it from one station to another. It moves around with its own housing on the top of Paranal, almost like a snail. The VLTI is arguably the world's most advanced optical device of this type. It has already demonstrated its powerful capabilities by addressing several key scientific issues, such as determining the size and the shape of a variety of stars (ESO PR 22/02, PR 14/03, PR 31/03, and PR 09/06), measuring distances to stars (ESO PR 25/04), probing the innermost regions of the proto-planetary discs around young stars (ESO PR 27/04 and PR 35/06) or making the first detection by infrared interferometry of an extragalactic object (ESO PR 17/03).

Indications of a spatial variation of the fine structure constant.

PubMed

Webb, J K; King, J A; Murphy, M T; Flambaum, V V; Carswell, R F; Bainbridge, M B

2011-11-04

We previously reported Keck telescope observations suggesting a smaller value of the fine structure constant α at high redshift. New Very Large Telescope (VLT) data, probing a different direction in the Universe, shows an inverse evolution; α increases at high redshift. Although the pattern could be due to as yet undetected systematic effects, with the systematics as presently understood the combined data set fits a spatial dipole, significant at the 4.2 σ level, in the direction right ascension 17.5 ± 0.9 h, declination -58 ± 9 deg. The independent VLT and Keck samples give consistent dipole directions and amplitudes, as do high and low redshift samples. A search for systematics, using observations duplicated at both telescopes, reveals none so far which emulate this result.

Optical turbulence profiling with Stereo-SCIDAR for VLT and ELT

NASA Astrophysics Data System (ADS)

Osborn, J.; Wilson, R. W.; Sarazin, M.; Butterley, T.; Chacón, A.; Derie, F.; Farley, O. J. D.; Haubois, X.; Laidlaw, D.; LeLouarn, M.; Masciadri, E.; Milli, J.; Navarrete, J.; Townson, M. J.

2018-07-01

Knowledge of the Earth's atmospheric optical turbulence is critical for astronomical instrumentation. Not only does it enable performance verification and optimization of the existing systems, but it is required for the design of future instruments. As a minimum this includes integrated astro-atmospheric parameters such as seeing, coherence time, and isoplanatic angle, but for more sophisticated systems such as wide-field adaptive optics enabled instrumentation the vertical structure of the turbulence is also required. Stereo-SCIDAR (Scintillation Detection and Ranging) is a technique specifically designed to characterize the Earth's atmospheric turbulence with high-altitude resolution and high sensitivity. Together with ESO (European Southern Observatory), Durham University has commissioned a Stereo-SCIDAR instrument at Cerro Paranal, Chile, the site of the Very Large Telescope (VLT), and only 20 km from the site of the future Extremely Large Telescope (ELT). Here we provide results from the first 18 months of operation at ESO Paranal including instrument comparisons and atmospheric statistics. Based on a sample of 83 nights spread over 22 months covering all seasons, we find the median seeing to be 0.64″ with 50 per cent of the turbulence confined to an altitude below 2 km and 40 per cent below 600 m. The median coherence time and isoplanatic angle are found as 4.18 ms and 1.75″, respectively. A substantial campaign of inter-instrument comparison was also undertaken to assure the validity of the data. The Stereo-SCIDAR profiles (optical turbulence strength and velocity as a function of altitude) have been compared with the Surface-Layer Slope Detection And Ranging, Multi-Aperture Scintillation Sensor-Differential Image Motion Monitor, and the European Centre for Medium Range Weather Forecasts model. The correlation coefficients are between 0.61 (isoplanatic angle) and 0.84 (seeing).

Towards a coherent view at infrared wavelengths of mass loss in Betelgeuse

NASA Astrophysics Data System (ADS)

Kervella, P.; Perrin, G.; Montargès, M.; Haubois, X.

2013-05-01

The violent convective motions, low surface gravity, and high brightness of red supergiants combine to trigger an intense stellar wind. As the distance from the star increases, the standard scenario is that the ejected material forms molecules, then dust particles. But this general picture is still fragmentary. Our goal is to assemble a better understanding of mass loss in Betelgeuse, considered as a prototype for its class, from its photosphere to the interface of its wind with the interstellar medium. Thanks to its proximity ( ≈ 197 pc), it is ideally suited for such a detailed study. Over the past few years, our team obtained an extensive set of observations of Betelgeuse from high angular resolution instruments, probing a broad range of spatial scales: 1) interferometric imaging of its photosphere and close envelope in the near- and thermal-IR domains (IOTA/IONIC), 2) adaptive optics "lucky imaging" of its compact molecular envelope (VLT/NACO, 1.0-2.2 μm), and 3) diffraction-limited imaging of its dusty envelope (VLT/VISIR, 8-20 μm). From our interferometric data, we detect the presence of spots at the surface of the star, as well as CO and H2O molecules, and dust particles close to the star. Within 6 R⋆, the flux distribution of the envelope is compatible with the presence of the CN molecule. At a few arcseconds from the central star, we observe a complex dusty envelope probably containing O-rich dust (e.g. silicates, alumina). We present an overview of these recent observational results and ongoing work. They provide new hints on the physical and chemical mechanisms through which Betelgeuse interacts with its environment.

The Crowded Magnetosphere Of The Post-Common-Envelope Binary QS Virginis

NASA Astrophysics Data System (ADS)

Hill, Colin

2016-06-01

We present high-speed photometry and high-resolution spectroscopy of the short-period (Prot = 3.6 h) eclipsing post-common-envelope binary QS Virginis (QS Vir). Our UVES spectra span in excess of 6 orbits, over more than a year, and reveal the presence of several large prominences passing in front of both the M star and its white dwarf (WD) companion. Despite showing small variations on a time-scale of days, they persist for more than a year and may last decades. Roche tomography reveals a heavily spotted M star, with long-lived spots remaining in fixed locations, preferentially found on the hemisphere facing the WD. We find the 14,220 ± 350 K WD is relatively massive at 0.782 ± 0.013 M(_{odot}),with a radius of0.01068 ± 0.00007 R(_{odot}), consistent with evolutionary models. The tidally distorted M star has a mass of 0.382 ± 0.006 M(_{odot})and a radius of0.381 ± 0.003 R(_{odot}), also consistent with evolutionary models. Since the M star's radius is still within its Roche lobe and there is no evidence that it is overinflated, we conclude that QS Vir is most likely a pre-cataclysmic binary just about to become semidetached.

The nature of the ionised nebula surrounding the red supergiant W26

NASA Astrophysics Data System (ADS)

Wesson, Roger

2015-08-01

The red supergiant W26 in the massive star cluster Westerlund 1 is surrounded by a compact ionised nebula. This is unique among RSGs, and the excitation mechanism of the nebula is not yet known - it may be ionised by an unseen compact companion, or by a nearby blue supergiant. We present new observations of the nebula: high resolution spatially resolved spectra taken with FLAMES at the VLT show that the nebula is a ring, with velocities consistent with that expected for red supergiant ejecta, and ruling out the possibility of a Luminous Blue Variable-type eruption preceding the RSG phase as the origin of the nebula. A triangular patch of nebulosity outside the ring appears to be associated with W26, and may be material stripped from the expanding ring by the cumulative cluster wind and radiation field.

New Paranal Views

NASA Astrophysics Data System (ADS)

2001-01-01

Last year saw very good progress at ESO's Paranal Observatory , the site of the Very Large Telescope (VLT). The third and fourth 8.2-m Unit Telescopes, MELIPAL and YEPUN had "First Light" (cf. PR 01/00 and PR 18/00 ), while the first two, ANTU and KUEYEN , were busy collecting first-class data for hundreds of astronomers. Meanwhile, work continued towards the next phase of the VLT project, the combination of the telescopes into the VLT Interferometer. The test instrument, VINCI (cf. PR 22/00 ) is now being installed in the VLTI Laboratory at the centre of the observing platform on the top of Paranal. Below is a new collection of video sequences and photos that illustrate the latest developments at the Paranal Observatory. The were obtained by the EPR Video Team in December 2000. The photos are available in different formats, including "high-resolution" that is suitable for reproduction purposes. A related ESO Video News Reel for professional broadcasters will soon become available and will be announced via the usual channels. Overview Paranal Observatory (Dec. 2000) Video Clip 02a/01 [MPEG - 4.5Mb] ESO PR Video Clip 02a/01 "Paranal Observatory (December 2000)" (4875 frames/3:15 min) [MPEG Video+Audio; 160x120 pix; 4.5Mb] [MPEG Video+Audio; 320x240 pix; 13.5 Mb] [RealMedia; streaming; 34kps] [RealMedia; streaming; 200kps] ESO Video Clip 02a/01 shows some of the construction activities at the Paranal Observatory in December 2000, beginning with a general view of the site. Then follow views of the Residencia , a building that has been designed by Architects Auer and Weber in Munich - it integrates very well into the desert, creating a welcome recreational site for staff and visitors in this harsh environment. The next scenes focus on the "stations" for the auxiliary telescopes for the VLTI and the installation of two delay lines in the 140-m long underground tunnel. The following part of the video clip shows the start-up of the excavation work for the 2.6-m VLT Survey Telescope (VST) as well as the location known as the "NTT Peak", now under consideration for the installation of the 4-m VISTA telescope. The last images are from to the second 8.2-m Unit Telescope, KUEYEN, that has been in full use by the astronomers with the UVES and FORS2 instruments since April 2000. ESO PR Photo 04a/01 ESO PR Photo 04a/01 [Preview - JPEG: 466 x 400 pix - 58k] [Normal - JPEG: 931 x 800 pix - 688k] [Hires - JPEG: 3000 x 2577 pix - 7.6M] Caption : PR Photo 04a/01 shows an afternoon view from the Paranal summit towards East, with the Base Camp and the new Residencia on the slope to the right, above the valley in the shadow of the mountain. ESO PR Photo 04b/01 ESO PR Photo 04b/01 [Preview - JPEG: 791 x 400 pix - 89k] [Normal - JPEG: 1582 x 800 pix - 1.1Mk] [Hires - JPEG: 3000 x 1517 pix - 3.6M] PR Photo 04b/01 shows the ramp leading to the main entrance to the partly subterranean Residencia , with the steel skeleton for the dome over the central area in place. ESO PR Photo 04c/01 ESO PR Photo 04c/01 [Preview - JPEG: 498 x 400 pix - 65k] [Normal - JPEG: 995 x 800 pix - 640k] [Hires - JPEG: 3000 x 2411 pix - 6.6M] PR Photo 04c/01 is an indoor view of the reception hall under the dome, looking towards the main entrance. ESO PR Photo 04d/01 ESO PR Photo 04d/01 [Preview - JPEG: 472 x 400 pix - 61k] [Normal - JPEG: 944 x 800 pix - 632k] [Hires - JPEG: 3000 x 2543 pix - 5.8M] PR Photo 04d/01 shows the ramps from the reception area towards the rooms. The VLT Interferometer The Delay Lines consitute a most important element of the VLT Interferometer , cf. PR Photos 26a-e/00. At this moment, two Delay Lines are operational on site. A third system will be integrated early this year. The VLTI Delay Line is located in an underground tunnel that is 168 metres long and 8 metres wide. This configuration has been designed to accommodate up to eight Delay Lines, including their transfer optics in an ideal environment: stable temperature, high degree of cleanliness, low levels of straylight, low air turbulence. The positions of the Delay Line carriages are computed to adjust the Optical Path Lengths requested for the fringe pattern observation. The positions are controlled in real time by a laser metrology system, specially developed for this purpose. The position precision is about 20 nm (1 nm = 10 -9 m, or 1 millionth of a millimetre) over a distance of 120 metres. The maximum velocity is 0.50 m/s in position mode and maximum 0.05 m/s in operation. The system is designed for 25 year of operation and to survive earthquake up to 8.6 magnitude on the Richter scale. The VLTI Delay Line is a three-year project, carried out by ESO in collaboration with Dutch Space Holdings (formerly Fokker Space) and TPD-TNO . VLTI Delay Lines (December 2000) - ESO PR Video Clip 02b/01 [MPEG - 3.6Mb] ESO PR Video Clip 02b/01 "VLTI Delay Lines (December 2000)" (2000 frames/1:20 min) [MPEG Video+Audio; 160x120 pix; 3.6Mb] [MPEG Video+Audio; 320x240 pix; 13.7 Mb] [RealMedia; streaming; 34kps] [RealMedia; streaming; 200kps] ESO Video Clip 02b/00 shows the Delay Lines of the VLT Interferometer facility at Paranal during tests. One of the carriages is moving on 66-metre long rectified rails, driven by a linear motor. The carriage is equipped with three wheels in order to preserve high guidance accuracy. Another important element is the Cat's Eye that reflects the light from the telescope to the VLT instrumentation. This optical system is made of aluminium (including the mirrors) to avoid thermo-mechanical problems. ESO PR Photo 04e/01 ESO PR Photo 04e/01 [Preview - JPEG: 400 x 402 pix - 62k] [Normal - JPEG: 800 x 804 pix - 544k] [Hires - JPEG: 3000 x 3016 pix - 6.2M] Caption : PR Photo 04e/01 shows one of the 30 "stations" for the movable 1.8-m Auxiliary Telescopes. When one of these telescopes is positioned ("parked") on top of it, The light will be guided through the hole towards the Interferometric Tunnel and the Delay Lines. ESO PR Photo 04f/01 ESO PR Photo 04f/01 [Preview - JPEG: 568 x 400 pix - 96k] [Normal - JPEG: 1136 x 800 pix - 840k] [Hires - JPEG: 3000 x 2112 pix - 4.6M] PR Photo 04f/01 shows a general view of the Interferometric Tunnel and the Delay Lines. ESO PR Photo 04g/01 ESO PR Photo 04g/01 [Preview - JPEG: 406 x 400 pix - 62k] [Normal - JPEG: 812 x 800 pix - 448k] [Hires - JPEG: 3000 x 2956 pix - 5.5M] PR Photo 04g/01 shows one of the Delay Line carriages in parking position. The "NTT Peak" The "NTT Peak" is a mountain top located about 2 km to the north of Paranal. It received this name when ESO considered to move the 3.58-m New Technology Telescope from La Silla to this peak. The possibility of installing the 4-m VISTA telescope (cf. PR 03/00 ) on this peak is now being discussed. ESO PR Photo 04h/01 ESO PR Photo 04h/01 [Preview - JPEG: 630 x 400 pix - 89k] [Normal - JPEG: 1259 x 800 pix - 1.1M] [Hires - JPEG: 3000 x 1907 pix - 5.2M] PR Photo 04h/01 shows the view from the "NTT Peak" towards south, vith the Paranal mountain and the VLT enclosures in the background. ESO PR Photo 04i/01 ESO PR Photo 04i/01 [Preview - JPEG: 516 x 400 pix - 50k] [Normal - JPEG: 1031 x 800 pix - 664k] [Hires - JPEG: 3000 x 2328 pix - 6.0M] PR Photo 04i/01 is a view towards the "NTT Peak" from the top of the Paranal mountain. The access road and the concrete pillar that was used to support a site testing telescope at the top of this peak are seen This is the caption to ESO PR Photos 04a-1/01 and PR Video Clips 02a-b/01 . They may be reproduced, if credit is given to the European Southern Observatory. The ESO PR Video Clips service to visitors to the ESO website provides "animated" illustrations of the ongoing work and events at the European Southern Observatory. The most recent clip was: ESO PR Video Clip 01/01 about the Physics On Stage Festival (11 January 2001) . Information is also available on the web about other ESO videos.

Spatially-Resolved Observations of Giant Stars with SPHERE

NASA Astrophysics Data System (ADS)

Khouri, Theo

2018-04-01

SPHERE on the VLT is an extreme adaptive optics instrument that produces images with unprecedented angular resolution at visible and near-infrared wavelengths. Its primary goal is imaging, low-resolution spectroscopic, and polarimetric characterization of extra-solar planetary systems. Nonetheless, the high spatial resolution and the instrument design optimized for observations in a narrow field of view around bright targets make SPHERE the perfect instrument for obtaining spatially-resolved images of close-by giant, evolved stars. This is particularly true at the shortest wavelengths available with SPHERE, where the angular resolution is best (> 20 mas) and these stars appear larger (< 70 mas). In this talk, I will review how SPHERE has been used to study the surfaces and extended atmospheres of evolved stars and how these observations advance our understanding of the stellar pulsations and convective motions that shape these stars. Moreover, I will present recent results from a monitoring campaign of the star R Doradus using SPHERE with observations taken at twelve epochs over eight months that reveal features on the stellar disc varying on timescales of a few weeks. Finally, I will present quasi-simultaneous observations with SPHERE and ALMA that spatially resolve the stellar discs of two asymptotic giant branch stars, Mira and R Doradus, and discuss what such multi-wavelength observation campaigns can teach us about the processes that shape evolved stars.

Embedded AGN and star formation in the central 80 pc of IC 3639

NASA Astrophysics Data System (ADS)

Fernández-Ontiveros, J. A.; Tristram, K. R. W.; Hönig, S.; Gandhi, P.; Weigelt, G.

2018-03-01

Aims: Our goal is to probe the inner structure and the nature of the mid-IR emission in the active galaxy IC 3639, which hosts a Seyfert 2 nucleus and shows signatures of strong star-forming activity. Methods: We used interferometric observations in the N-band with VLTI/MIDI to resolve the mid-IR emission of this nucleus. The origin of the nuclear infrared emission is determined from: (1) the comparison of the correlated fluxes from VLTI/MIDI with the fluxes measured at subarcsecond resolution (VLT/VISIR, VLT/ISAAC); (2) diagnostics based on IR fine-structure line ratios, the IR continuum emission, IR bands produced by polycyclic aromatic hydrocarbons (PAH) and silicates; and (3) the high-angular resolution spectral energy distribution. Results: A large fraction of the total mid-IR emission of IC 3639 is produced in the innermost ≲80 pc with only 1% of the total luminosity released in the UV/optical range. The unresolved flux of IC 3639 is 90 ± 20 mJy at 10.5 μm, measured with three different baselines in VLTI (UT1-UT2, UT3-UT4, and UT2-UT3; 46-58 m), making this the faintest measurement so far achieved with mid-IR interferometry. The correlated flux is a factor of 3-4 times fainter than the VLT/VISIR total flux measurement. The observations suggest that most of the mid-IR emission has its origin on spatial scales between 10 and 80 pc (40-340 mas). The emission confined within the inner 80 pc is either dominated by a starburst component or by the AGN core. The brightness distribution could be reproduced by a single component associated with the AGN, although this scenario would imply a very extended dust distribution when compared to other nearby Seyfert galaxies detected with MIDI. The extended component could also be associated with polar dust emission, that is, with a dusty wind blown by the AGN. However, a mixed contribution dominated by the star formation component over the AGN is favoured by the diagnostics based on ratios of IR fine-structure emission lines, the shape of the IR continuum, and the PAH and silicate bands. Conclusions: A composite AGN-starburst scenario is able to explain both the mid-IR brightness distribution and the IR spectral properties observed in the nucleus of IC 3639. The nuclear starburst would dominate the mid-IR emission and the ionisation of low-excitation lines (e.g. [Ne II]12.8 μm) with a net contribution of 70%. The AGN accounts for the remaining 30% of the mid-IR flux, ascribed to the unresolved component in the MIDI observations, and the ionisation of high-excitation lines (e.g. [Ne V]14.3 μm and [O IV]25.9 μm). Based on observations collected at the European Southern Observatory, Chile, programmes 070.B-0393, 088.D-0005 and 088.B-0809.

[Y/Mg] stellar dating calibration

NASA Astrophysics Data System (ADS)

Titarenko, A.; Recio-Blanco, A.; de Laverny, P.; Hayden, M.; Guiglion, G.; Worley, C.

2018-04-01

Gaia DR1 has opened a new era of stellar age dating, that is crucial for many astrophysical objectives. In addition, the Gaia based isochrone fitting ages can be compared to other chemical clocks like the [Y/Mg] one (Nissen et al. 2015). In our work we have used ESO archived data of the AMBRE project (de Laverny et al. 2013) for UVES spectra, in order to evaluate the age [Y/Mg] abundance correlation for turn off stars. 310 turn off stars of the UVES-archive (setups 564 and 580) are included in the TGAS database. Isochrone fitting ages were derived. We have applied the GAUGUIN procedure for those stars to derive the Mg and the Y abundances. As the result we present the [Y/Mg] vs stellar age dependence for ~40 TO-stars.

The Gaia-ESO Survey: evidence of atomic diffusion in M67?

NASA Astrophysics Data System (ADS)

Bertelli Motta, C.; Pasquali, A.; Richer, J.; Michaud, G.; Salaris, M.; Bragaglia, A.; Magrini, L.; Randich, S.; Grebel, E. K.; Adibekyan, V.; Blanco-Cuaresma, S.; Drazdauskas, A.; Fu, X.; Martell, S.; Tautvaišienė, G.; Gilmore, G.; Alfaro, E. J.; Bensby, T.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Heiter, U.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-07-01

Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in subgiant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.

Large Interstellar Polarisation Survey:The Dust Elongation When Combining Optical-Submm Polarisation

NASA Astrophysics Data System (ADS)

Siebenmorgen, Ralf; Voschinnikov, N.; Bagnulo, S.; Cox, N.; Cami, J.

2017-10-01

The Planck mission has shown that dust properties of the diffuse ISM varies on a large scale and we present variability on a small scales. We present FORS spectro-polarimetry obtained by the Large Interstellar Polarisation Survey along 60 sight-lines. We fit these combined with extinction data by a silicate and carbon dust model with grain sizes ranging from the molecular to the sub-mic. domain. Large silicates of prolate shape account for the observed polarisation. For 37 sight-lines we complement our data set with UVES high-resolution spectra that establish the presence of single or multiple clouds along individual sight-lines. We find correlations between extinction and Serkowski parameters with the dust model and that the presence of multiple clouds depolarises the incoming radiation. However, there is a degeneracy in the dust model between alignment efficiency and the elongation of the grains. This degeneracy can be broken by combining polarization data in the optical-to-submm. This is of wide general interest as it improves the accuracy of deriving dust masses. We show that a flat IR/submm polarisation spectrum with substantial polarisation is predicted from dust models.

The Gaia-ESO Survey: Evidence of atomic diffusion in M67?

NASA Astrophysics Data System (ADS)

Motta, C. Bertelli; Pasquali, A.; Richer, J.; Michaud, G.; Salaris, M.; Bragaglia, A.; Magrini, L.; Randich, S.; Grebel, E. K.; Adibekyan, V.; Blanco-Cuaresma, S.; Drazdauskas, A.; Fu, X.; Martell, S.; TautvaišienÄ--, G.; Gilmore, G.; Alfaro, E. J.; Bensby, T.; Flaccomio, E.; Koposov, S. E.; Korn, A. J.; Lanzafame, A. C.; Smiljanic, R.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Damiani, F.; Franciosini, E.; Heiter, U.; Hourihane, A.; Jofré, P.; Lardo, C.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2018-04-01

Investigating the chemical homogeneity of stars born from the same molecular cloud at virtually the same time is very important for our understanding of the chemical enrichment of the interstellar medium and with it the chemical evolution of the Galaxy. One major cause of inhomogeneities in the abundances of open clusters is stellar evolution of the cluster members. In this work, we investigate variations in the surface chemical composition of member stars of the old open cluster M67 as a possible consequence of atomic diffusion effects taking place during the main-sequence phase. The abundances used are obtained from high-resolution UVES/FLAMES spectra within the framework of the Gaia-ESO Survey. We find that the surface abundances of stars on the main sequence decrease with increasing mass reaching a minimum at the turn-off. After deepening of the convective envelope in sub-giant branch stars, the initial surface abundances are restored. We found the measured abundances to be consistent with the predictions of stellar evolutionary models for a cluster with the age and metallicity of M67. Our findings indicate that atomic diffusion poses a non-negligible constraint on the achievable precision of chemical tagging methods.

Sm-Nd and Rb-Sr Isotopic Studies of Meteorite Kalahari 009: An Old VLT Mare Basalt

NASA Technical Reports Server (NTRS)

Shih, C.-Y.; Nyquist, L. E.; Reese, Y.; Bischoff, A.

2008-01-01

Lunar meteorite Kalahari 009 is a fragmental basaltic breccia contain ing various very-low-Ti (VLT) mare basalt clasts embedded in a fine-g rained matrix of similar composition. This meteorite and lunar meteorite Kalahari 008, an anorthositic breccia, were suggested to be paired mainly due to the presence of similar fayalitic olivines in fragment s found in both meteorites. Thus, Kalahari 009 probably represents a VLT basalt that came from a locality near a mare-highland boundary r egion of the Moon, as compared to the typical VLT mare basalt samples collected at Mare Crisium during the Luna-24 mission. The concordant Sm-Nd and Ar-Ar ages of such a VLT basalt (24170) suggest that the extrusion of VLT basalts at Mare Crisium occurred 3.30 +/- 0.05 Ga ag o. Previous age results for Kalahari 009 range from approximately 4.2 Ga by its Lu-Hf isochron age to 1.70?0.04 Ga of its Ar-Ar plateau ag e. However, recent in-situ U-Pb dating of phosphates in Kalahari 009 defined an old crystallization age of 4.35+/- 0.15 Ga. The authors su ggested that Kalahari 009 represents a cryptomaria basalt. In this r eport, we present Sm-Nd and Rb-Sr isotopic results for Kalahari 009, discuss the relationship of its age and isotopic characteristics to t hose of other L-24 VLT mare basalts and other probable cryptomaria ba salts represented by Apollo 14 aluminous mare basalts, and discuss it s petrogenesis.

ESO's Two Observatories Merge

NASA Astrophysics Data System (ADS)

2005-02-01

On February 1, 2005, the European Southern Observatory (ESO) has merged its two observatories, La Silla and Paranal, into one. This move will help Europe's prime organisation for astronomy to better manage its many and diverse projects by deploying available resources more efficiently where and when they are needed. The merged observatory will be known as the La Silla Paranal Observatory. Catherine Cesarsky, ESO's Director General, comments the new development: "The merging, which was planned during the past year with the deep involvement of all the staff, has created unified maintenance and engineering (including software, mechanics, electronics and optics) departments across the two sites, further increasing the already very high efficiency of our telescopes. It is my great pleasure to commend the excellent work of Jorge Melnick, former director of the La Silla Observatory, and of Roberto Gilmozzi, the director of Paranal." ESO's headquarters are located in Garching, in the vicinity of Munich (Bavaria, Germany), and this intergovernmental organisation has established itself as a world-leader in astronomy. Created in 1962, ESO is now supported by eleven member states (Belgium, Denmark, Finland, France, Germany, Italy, The Netherlands, Portugal, Sweden, Switzerland, and the United Kingdom). It operates major telescopes on two remote sites, all located in Chile: La Silla, about 600 km north of Santiago and at an altitude of 2400m; Paranal, a 2600m high mountain in the Atacama Desert 120 km south of the coastal city of Antofagasta. Most recently, ESO has started the construction of an observatory at Chajnantor, a 5000m high site, also in the Atacama Desert. La Silla, north of the town of La Serena, has been the bastion of the organization's facilities since 1964. It is the site of two of the most productive 4-m class telescopes in the world, the New Technology Telescope (NTT) - the first major telescope equipped with active optics - and the 3.6-m, which hosts HARPS, a unique instrument capable of measuring stellar radial velocities with an unsurpassed accuracy better than 1 m/s, making it a very powerful tool for the discovery of extra-solar planets. In addition, astronomers have also access to the 2.2-m ESO/MPG telescope with its Wide Field Imager camera. A new control room, the RITZ (Remote Integrated Telescope Zentrum), allows operating all three ESO telescopes at La Silla from a single place. The La Silla Observatory is also the first world-class observatory to have been granted certification for the International Organization for Standardization (ISO) 9001 Quality Management System. Moreover, the infrastructure of La Silla is still used by many of the ESO member states for targeted projects such as the Swiss 1.2-m Euler telescope and the robotic telescope specialized in the follow-up of gamma-ray bursts detected by satellites, the Italian REM (Rapid Eye Mount). In addition, La Silla is in charge of the APEX (Atacama Pathfinder Experiment) 12-m sub-millimetre telescope which will soon start routine observations at Chajnantor, the site of the future Atacama Large Millimeter Array (ALMA). The APEX project is a collaboration between the Max Planck Society in Germany, Onsala Observatory in Sweden and ESO. ESO also operates Paranal, home of the Very Large Telescope (VLT) and the VLT Interferometer (VLTI). Antu, the first 8.2-m Unit Telescope of the VLT, saw First Light in May 1998, starting what has become a revolution in European astronomy. Since then, the three other Unit Telescopes - Kueyen, Melipal and Yepun - have been successfully put into operation with an impressive suite of the most advanced astronomical instruments. The interferometric mode of the VLT (VLTI) is also operational and fully integrated in the VLT data flow system. In the VLTI mode, one state-of-the-art instrument is already available and another will follow soon. With its remarkable resolution and unsurpassed surface area, the VLT is at the forefront of astronomical technology and is one of the premier facilities in the world for optical and near-infrared observations. In addition to the state-of-the-art Very Large Telescope and the four Auxiliary Telescopes of 1.8-m diameter which can move to relocate in up to 30 different locations feeding the interferometer, Paranal will also be home to the 2.6-m VLT Survey telescope (VST) and the 4.2-m VISTA IR survey telescope. Both Paranal and La Silla have a proven record of their unique ability to address most current issues in observational astronomy. In 2004 alone, each observatory provided data for the publication of about 350 peer-reviewed journal articles, more than any other ground-based observatory. With the present merging of these top-ranking astronomical observatories, fostering synergies and harmonizing the many diverse activities, ESO and the entire community of European astronomers will profit even more from these highly efficient research facilities. Images of ESO's observatories and telescopes are available in the ESO gallery.

Eta Carinae's 2014.6 spectroscopic event: Clues to the long-term recovery from its Great Eruption

NASA Astrophysics Data System (ADS)

Mehner, A.; Davidson, K.; Humphreys, R. M.; Walter, F. M.; Baade, D.; de Wit, W. J.; Martin, J.; Ishibashi, K.; Rivinius, T.; Martayan, C.; Ruiz, M. T.; Weis, K.

2015-06-01

Aims: Every 5.5 years, η Car's light curve and spectrum change remarkably across all observed wavelength bands. These so-called spectroscopic events are most likely caused by the close approach of a companion. We compare the recent spectroscopic event in mid-2014 to the events in 2003 and 2009 and investigate long-term trends. Methods: Eta Car was observed with HST STIS, VLT UVES, and CTIO 1.5 m CHIRON for a period of more than two years in 2012-2015. Archival observations with these instruments cover three orbital cycles and the events of 2003.5, 2009.1, and 2014.6. The STIS spectra provide high spatial resolution and include epochs during the 2014 event when observations from most ground-based observatories were not feasible. The strategy for UVES observations allows for a multidimensional analysis, because each location in the reflection nebula is correlated with a different stellar latitude. Results: Important spectroscopic diagnostics during η Car's events show significant changes in 2014 compared to previous events. While the timing of the first He ii λ4686 flash was remarkably similar to previous events, the He ii equivalent widths were slightly larger, and the line flux increased by a factor of ~7 compared to 2003. The second He ii peak occurred at about the same phase as in 2009, but was stronger. The He i line flux grew by a factor of ~8 in 2009-2014 compared to 1998-2003. The N ii emission lines also increased in strength. On the other hand, Hα and Fe ii lines show the smallest emission strengths ever observed in η Car. The optical continuum brightened by a factor of ~4 in the past 10-15 years.The polar spectrum shows fewer changes in the broad wind emission lines: the Fe ii emission strength decreased by a factor of ~2 (compared to a factor of ~4 in our direct line of sight). The He ii equivalent widths at FOS4 were larger in 2009 and 2014 than during the 2003 event. Conclusions: The basic character of η Car's spectroscopic events has changed in the past two to three cycles. The ionizing UV radiation dramatically weakened during each pre-2014 event but not in 2014. The strengthening of He i and N ii emission and the weakening of the lower-excitation Hα and Fe ii wind featuresin our direct line of sight implies a substantial change in the physical parameters of the emitting regions. The polar spectrum at FOS4 shows fewer changes in the broad wind emission lines, which may be explained by the latitude-dependent wind structure of η Car. The quick and strong recovery of the He ii emission in 2014 supports a scenario, in which the wind-wind shock may not have completely collapsed as was proposed for previous events. As a result, the companion did not accrete as much material as in previous events. All this may be the consequence of just one elementary change, namely a strong decrease in the primary's mass-loss rate. This would mark the beginning of a new phase, in which the spectroscopic events can be described as an occultation by the primary's wind. Based on observations with the NASA/ESA Hubble Space Telescope, obtained (from the Data Archive) at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programmes #7302, 8036, 8327, 8483, 8619, 9083, 9242, 9337, 9420, 9973, 11506, 11612, 12013, 12508, 12750, 13377, and 13789. Based on observations collected at the European Southern Observatory, Chile under Prog-IDs: 60.A-9022(A), 70.D-0607(A), 71.D-0168(A), 072.D-0524(A), 074.D-0141(A), 077.D-0618(A), 380.D-0036(A), 381.D-0004(A), 282.D-5073(A,B,C,D,E), 089.D-0024(A), 592.D-0047(A,B,C). Based in part on data obtained with the SMARTS/CTIO 1.5 m, operated by the SMARTS Consortium.Tables 1-3 are available in electronic form at http://www.aanda.org

Detection of magnetic field in the B2 star ρ Ophiuchi A with ESO FORS2

NASA Astrophysics Data System (ADS)

Pillitteri, I.; Fossati, L.; Castro Rodriguez, N.; Oskinova, L.; Wolk, S. J.

2018-02-01

Circumstantial evidence suggests that magnetism and enhanced X-ray emission are likely correlated in early B-type stars: similar fractions of them ( 10%) are strong and hard X-ray sources and possess strong magnetic fields. It is also known that some B-type stars have spots on their surface. Yet up to now no X-ray activity associated with spots on early-type stars was detected. In this Letter we report the detection of a magnetic field on the B2V star ρ Oph A. Previously, we assessed that the X-ray activity of this star is associated with a surface spot, herewith we establish its magnetic origin. We analyze spectra of ρ Oph A obtained with the FORS2 spectrograph at ESO Very Large Telescope (VLT) at two epochs, and detect a longitudinal component of the magnetic field of the order of 500 G in one of the datasets. The detection of the magnetic field only at one epoch can be explained by stellar rotation which is also invoked to explain observed periodic X-ray activity. From archival HARPS ESO VLT high resolution spectra we derived the fundamental stellar parameters of ρ Oph A and further constrained its age. We conclude that ρ Oph A provides strong evidence for the presence of active X-ray emitting regions on young magnetized early type stars. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 099.D-0067(A) and 078.C-0403(A).

Dwarf planet Ceres: Ellipsoid dimensions and rotational pole from Keck and VLT adaptive optics images

NASA Astrophysics Data System (ADS)

Drummond, J. D.; Carry, B.; Merline, W. J.; Dumas, C.; Hammel, H.; Erard, S.; Conrad, A.; Tamblyn, P.; Chapman, C. R.

2014-07-01

The dwarf planet (1) Ceres, the largest object between Mars and Jupiter, is the target of the NASA Dawn mission, and we seek a comprehensive description of the spin-axis orientation and dimensions of Ceres in order to support the early science operations at the rendezvous in 2015. We have obtained high-angular resolution images using adaptive optics cameras at the W.M. Keck Observatory and the ESO VLT over ten dates between 2001 and 2010, confirming that the shape of Ceres is well described by an oblate spheroid. We derive equatorial and polar diameters of 967 ± 10 km and 892 ± 10 km, respectively, for a model that includes fading of brightness towards the terminator, presumably linked to limb darkening. These dimensions lie between values derived from a previous analysis of a subset of these images obtained at Keck by Carry et al. (Carry et al. [2008]. Astron. Astrophys. 478 (4), 235-244) and a study of Hubble Space Telescope observations (Thomas et al. [2005]. Nature 437, 224-226). Although the dimensions are 1-2% smaller than those found from the HST, the oblateness is similar. We find the spin-vector coordinates of Ceres to lie at (287°, +64°) in equatorial EQJ2000 reference frame (346°, +82° in ecliptic ECJ2000 coordinates), yielding a small obliquity of 3°. While this is in agreement with the aforementioned studies, we have improved the accuracy of the pole determination, which we set at a 3° radius.

Jupiter's Thermal Structure on the Eve of Juno's Arrival and an NEB Expansion Event

NASA Astrophysics Data System (ADS)

Fletcher, Leigh N.; Orton, Glenn S.; Greathouse, Thomas K.; Sinclair, James; Giles, Rohini; Irwin, Patrick; Rogers, John; Encrenaz, Therese

2016-04-01

We report on a continuing program of ground-based thermal-infrared imaging spectroscopy to explore variability in Jupiter's atmospheric temperatures, winds, clouds and composition in support of the NASA/Juno mission, scheduled to arrive at Jupiter in July 2016. Observations during the 2015/16 apparition, centred on opposition on March 8th 2016, will be presented from NASA's Infrared Telescope Facility (IRTF) and ESO's Very Large Telescope (VLT) as part of a world-wide campaign to characterise the Jovian atmosphere to support Juno. Thermal and chemical contrasts, combined with the visible-light record from the amateur community, show that Jupiter's North Equatorial Belt (NEB) is presently expanding northwards. The combination of thermal and visible observations will allow us to determine the environmental conditions underlying this belt/zone variability. Radiometrically calibrated spectral scan maps of Jupiter have been regularly obtained using the TEXES instrument (Texas Echelon cross Echelle Spectrograph, Lacy et al. 2002, PASP 114, p153-168) on the IRTF since 2012, and observations are planned in January and April 2016. Ten settings between 5 and 25 μm (10-20 cm-1 wide settings at spectral resolutions of 2000-10000) were selected to be sensitive to jovian temperatures (via H2, CH4 and CH3D), tropospheric phosphine and ammonia, tropospheric haze opacity and stratospheric hydrocarbons ethane and acetylene. These will be supplemented by photometric imaging from the VLT/VISIR instrument (Lagage et al., 2004, Messenger 117, p12-16) in ten narrow-band filters to determine temperatures associated with discrete phenomena (vortices, plumes, waves) at higher diffraction-limited spatial resolution. Spectra and images are inverted via the NEMESIS retrieval algorithm (Irwin et al., 2008, JSQRT 109, p1136-1150) to map temperatures at multiple altitudes (1-600 mbar), winds, aerosol opacity and gaseous composition. Our most recent observations (November 2015) revealed (i) a regular stratospheric wave pattern in stratospheric temperatures between 20 and 30°N (i.e., above the North Tropical Zone and Temperate Belt, NTropZ and NTB, respectively), possibly associated with the northward expansion of the broad North Equatorial Belt (NEB); (ii) tropospheric thermal variability along the NEB itself with correlations between aerosol variability in the 600-mbar region (sensed at 8.6 μm) and the 2-3 bar region (sensed at 5 μm). This appears to coincide with similar NEB and NTropZ wave structure observed in reflected sunlight near 2 μm, based on images from the SpeX instrument on the IRTF. Zonal mean distributions of temperature, phosphine, ammonia, aerosols and hydrocarbons will be compared to those derived by the Cassini Composite Infrared Spectrometer (CIRS) 15 years earlier. High-resolution VLT images of the Great Red Spot will be compared between 2008 and 2016 to understand the thermochemical changes associated with its recent shrinkage. All images and maps of retrieved properties will be assembled as a database (JCliD) to aid in the interpretation of Juno data during 2016-2017.

Obscuring and Feeding Supermassive Black Holes with Evolving Nuclear Star Clusters

NASA Astrophysics Data System (ADS)

Schartmann, M.; Burkert, A.; Krause, M.; Camenzind, M.; Meisenheimer, K.; Davies, R. I.

2010-05-01

Recently, high-resolution observations made with the help of the near-infrared adaptive optics integral field spectrograph SINFONI at the VLT proved the existence of massive and young nuclear star clusters in the centers of a sample of Seyfert galaxies. With the help of high-resolution hydrodynamical simulations with the pluto code, we follow the evolution of such clusters, especially focusing on mass and energy feedback from young stars. This leads to a filamentary inflow of gas on large scales (tens of parsecs), whereas a turbulent and very dense disk builds up on the parsec scale. Here we concentrate on the long-term evolution of the nuclear disk in NGC 1068 with the help of an effective viscous disk model, using the mass input from the large-scale simulations and accounting for star formation in the disk. This two-stage modeling enables us to connect the tens-of-parsecs scale region (observable with SINFONI) with the parsec-scale environment (MIDI observations). At the current age of the nuclear star cluster, our simulations predict disk sizes of the order 0.8 to 0.9 pc, gas masses of order 106 M⊙, and mass transfer rates through the inner boundary of order 0.025 M⊙ yr-1, in good agreement with values derived from observations.

Stellar Populations and Physical Conditions at 100 pc Resolution in a Lensed Galaxy at z 4

NASA Astrophysics Data System (ADS)

Berg, Danielle

2015-10-01

Large surveys of star-forming galaxies at high redshift (z > 1.5) have provided us with a broad understanding of how galaxies assemble and evolve, but the spatial and spectral limitations inherent in observing faint, distant objects mean that many of the physical processes regulating this dynamic evolution are poorly constrained. Much of our most detailed knowledge of the physical conditions in distant galaxies comes from careful studies of gravitationally lensed sources, few of which are at z>3.5. FOR J0332-3557 is a gravitationally lensed galaxy at z 4 for which we and other groups have obtained a total of 37.3 hours of VLT spectroscopy. The rest-frame UV spectrum is notable for its unusual combination of both strong emission lines in the rest-frame UV and strong Lya and interstellar absorption, and for the unusual spatial variation seen in the nebular emission lines, which are less extended than the underlying stellar continuum. We propose high spatial resolution imaging of FOR J0332-3557 with four broadband filters on WFC3, taking advantage of both the HST resolution and the lensing magnification to study star formation and extinction on 100 pc scales. Because the interpretation of our unusual rest-frame UV and optical spectra requires an accurate reddening estimate, combining these observations with ground-based spectroscopy will give the most complete picture to date of chemical evolution in a distant galaxy.

Trace element composition of Luna 24 Crisium VLT basalt

NASA Technical Reports Server (NTRS)

Haskin, L. A.

1978-01-01

The origins of the individual particles analyzed from the Luna 24 core and the information they provide on the trace-element composition of Mare Crisium basalt are considered. Previous analyses of several Luna 24 soil fragments are reviewed. It is concluded that: (1) the average trace-element concentrations for 12 VLT basalt fragments are the best available estimates for bulk samples of Crisium VLT basalt; (2) there is weak evidence that the average Crisium basalt might have a small positive Eu anomaly relative to chondritic matter; (3) the soils contain components from sources other than the Crisium VLT basalt; and (4) there is no convincing information in concentrations of rare-earth elements, Co, Sc, FeO, or Na2O among the analyzed fragments to indicate more than one parent basalt.

Searching for H2 emission from protoplanetary disks using near- and mid-infrared high-resolution spectroscopy

NASA Astrophysics Data System (ADS)

Carmona, A.; van den Ancker, M. E.; Henning, Th.; Pavlyuchenkov, Ya.; Dullemond, C. P.; Goto, M.; Fedele, D.; Stecklum, B.; Thi, W.-F.; Bouwman, J.; Waters, L. B. F. M.

2008-05-01

The mass and dynamics of protoplanetary disks are dominated by molecular hydrogen (H2). However, observationally very little is known about the H2. In this paper, we discuss two projects aimed to constrain the properties of H2 in the disk's planet forming region (R<50AU). First, we present a sensitive survey for pure-rotational H2 emission at 12.278 and 17.035 μm in a sample of nearby Herbig Ae/Be and T Tauri stars using VISIR, ESO's VLT high-resolution mid-infrared spectrograph. Second, we report on a search for H2 ro-vibrational emission at 2.1228, 2.2233 and 2.2477 μm in the classical T Tauri star LkHα 264 and the debris disk 49 Cet employing CRIRES, ESO's VLT high-resolution near-infrared spectrograph. VISIR project: none of the sources show H2 mid-IR emission. The observed disks contain less than a few tenths of MJupiter of optically thin H2 at 150 K, and less than a few MEarth at T>300 K. % and higher T. Our non-detections are consistent with the low flux levels expected from the small amount of H2 gas in the surface layer of a Chiang and Goldreich (1997) Herbig Ae two-layer disk model. In our sources the H2 and dust in the surface layer have not significantly departed from thermal coupling (Tgas/Tdust<2) and the gas-to-dust ratio in the surface layer is very likely <1000. CRIRES project: The H2 lines at 2.1218 μm and 2.2233 μm are detected in LkHα 264. An upper limit on the 2.2477 μm H2 line flux in LkHα 264 is derived. 49 Cet does not exhibit H2 emission in any of observed lines. There are a few MMoon of optically thin hot H2 in the inner disk (0.1 AU) of LkHα 264, and less than a tenth of a MMoon of hot H2 in the inner disk of 49 Cet. The shape of the 1 0 S(0) line indicates that LkHα disk is close to face-on (i<35o). The measured 1 0 S(0)/1 0 S(1) and 2 1 S(1)/1 0 S(1) line ratios in LkHα 264 indicate that the H2 is thermally excited at T<1500 K. The lack of H2 emission in the NIR spectra of 49 Cet and the absence of Hα emission suggest that the gas in the inner disk of 49 Cet has dissipated.

NGC 6334 V revisited: The complex nature of the infrared nebula

NASA Astrophysics Data System (ADS)

Tapia, M.; Persi, P.; Roth, M.

2017-07-01

A comprehensive analysis is presented of the most recent infrared observations of the small, very young and enigmatic infrared nebula associated with NGC 6334-V. We re-analized images from the Spitzer/IRAC (3.6 a 8 μm), Herschel/SPIRE/PACS (70 a 500 μm), VISTA (1.2 a 2.2 μm), VLT/VISIR (11.3 a 18.7 μm) and HST/NICMOS (2.0 μm) archives. The very high spatial resolution from the latter two sets, combined with very recent sub-millimetre maps, allow us to suggest several possible star-formation scenarios that explain the observed infrared and radio properties of the region. Evidence is provided of the presence of a small population of low and medium-mass young stars embedded in the infrared reflection nebulosity NGC 6334 V that coexist with the nearby much younger Class 0 protostars.

The High Level Data Reduction Library

NASA Astrophysics Data System (ADS)

Ballester, P.; Gabasch, A.; Jung, Y.; Modigliani, A.; Taylor, J.; Coccato, L.; Freudling, W.; Neeser, M.; Marchetti, E.

2015-09-01

The European Southern Observatory (ESO) provides pipelines to reduce data for most of the instruments at its Very Large telescope (VLT). These pipelines are written as part of the development of VLT instruments, and are used both in the ESO's operational environment and by science users who receive VLT data. All the pipelines are highly specific geared toward instruments. However, experience showed that the independently developed pipelines include significant overlap, duplication and slight variations of similar algorithms. In order to reduce the cost of development, verification and maintenance of ESO pipelines, and at the same time improve the scientific quality of pipelines data products, ESO decided to develop a limited set of versatile high-level scientific functions that are to be used in all future pipelines. The routines are provided by the High-level Data Reduction Library (HDRL). To reach this goal, we first compare several candidate algorithms and verify them during a prototype phase using data sets from several instruments. Once the best algorithm and error model have been chosen, we start a design and implementation phase. The coding of HDRL is done in plain C and using the Common Pipeline Library (CPL) functionality. HDRL adopts consistent function naming conventions and a well defined API to minimise future maintenance costs, implements error propagation, uses pixel quality information, employs OpenMP to take advantage of multi-core processors, and is verified with extensive unit and regression tests. This poster describes the status of the project and the lesson learned during the development of reusable code implementing algorithms of high scientific quality.

Four Eyes Are Better

NASA Astrophysics Data System (ADS)

2002-09-01

VLT Interferometer Passes Another Technical Hurdle Summary During the nights of September 15/16 and 16/17, 2002, preliminary tests were successfully carried out during which the light beams from all four VLT 8.2-m Unit Telescopes (UTs) at the ESO Paranal Observatory were successively combined, two by two, to produce interferometric fringes . This marks a next important step towards the full implementation of the VLT Interferometer (VLTI) that will ultimately provide European astronomers with unequalled opportunities for exciting front-line research projects. It is no simple matter to ensure that the quartet of ANTU, KUEYEN, MELIPAL and YEPUN , each a massive giant with a suite of computer-controlled active mirrors, can work together by sending beams of light towards a common focal point via a complex system of compensating optics. Yet, in the span of only two nights, the four VLT telescopes were successfully "paired" to do exactly this, yielding a first tantalizing glimpse of the future possibilities with this new science machine. While there is still a long way ahead to the routine production of extremely sharp, interferometric images, the present test observations have allowed to demonstrate directly the 2D-resolution capacity of the VLTI by means of multiple measurements of a distant star. Much valuable experience was gained during those two nights and the ESO engineers and scientists are optimistic that the extensive test observations with the numerous components of the VLTI will continue to progress rapidly. Five intense, technical test periods are scheduled during the next six months; some of these with the Mid-Infrared interferometric instrument for the VLTI (MIDI) which will soon be installed at Paranal. Later in 2003, the first of the four moveable VLTI 1.8-m Auxiliary Telescopes (ATs) will be put in place on the top of the mountain; together they will permit regular interferometric observations, also without having to use the large UTs. PR Photo 22a/02 : Delay Lines in the Interferometric Tunnel. PR Photo 22b/02 : Baselines and "Interferometric PSF" from observations of the star Achernar . Combining the VLT telescopes ESO PR Photo 22a/02 ESO PR Photo 22a/02 [Preview - JPEG: 503 x 400 pix - 81k] [Normal - JPEG: 1005 x 800 pix - 488k] [Hi-Res - JPEG: 3000 x 2389 pix - 2.8M] Caption : PR Photo 22a/02 : VLT Delay Lines in the Interferometric Tunnel. Less than one year after the first combination of two 8.2-m VLT telescopes - described in detail in ESO Press Release 23/01 - successful tests have now been carried out, during which all of the four telescopes were combined pairwise in rapid succession . Of the six combinations possible (ANTU-KUEYEN, ANTU-MELIPAL, ANTU-YEPUN, KUEYEN-MELIPAL, KUEYEN-YEPUN and MELIPAL-YEPUN), only the last one could not be used, because of the current geometrical configuration of the three delay lines installed so far. The combination of the light beams from two (or more) VLT Unit Telescopes is a daunting task. It involves pointing them simultaneously towards the same celestial object, ensuring optimal optical adjustment of the computer-controlled telescope mirrors (including the shape of the 8.2-m primary mirror by "active optics"), performing extremely smooth and stable tracking of the object as the Earth turns, guiding the light beams via additional ("coudé") mirrors into the "delay lines" installed in the Interferometric Tunnel below the telescope platform, keeping the total path lengths equal to within a fraction of a micron during hours at a time and finally, to register the interferometric fringes at the focal point of the VINCI instrument [1], where the light beams encounter each other. Next year, the first adaptive optics systems for the VLTI will be inserted below the telescopes. By drastically reducing the smearing effects of the turbulent atmosphere through which the light has to pass before it enters the telescopes, this will further "stabilize" the imaging and increase the sensitivity of the VLTI by a factor of almost 100. First results with four Unit Telescopes ESO PR Photo 22b/02 ESO PR Photo 22b/02 [Preview - JPEG: 573 x 400 pix - 78k] [Normal - JPEG: 1145 x 800 pix - 232k] Caption : PR Photo 22b/02 : The left panel shows the rather incomplete set of "baselines" used during the present, short interferometric test exposures (in interferometric terminology: the "UV-plane coverage"). Each baseline is represented by two opposite, short arcs, symmetric around the origin (centre) of the diagram. The colour-coded pattern reflects the telescope pairs (ANTU-KUEYEN = magenta, ANTU-MELIPAL = red, ANTU-YEPUN = green, KUEYEN-MELIPAL = cyan, KUEYEN-YEPUN = blue), as seen from the observed object. Due to the limited time available, this distribution is far from uniform and is quite elongated in one direction. To the right is shown the reconstructed, two-dimensional interferometric point-spread function (PSF) of the star Achernar (in "negative" - with most light in the darkest areas). It is the result of subsequent computer processing of the measurements with the different baselines. On the largest scale, the image consists of an inner, round distribution of light, 0.057 arcsec wide, surrounded by an outer, much weaker, broad "ring" and with a "white" zone between these two areas. This is the "Airy disk" for a single 8.2-m telescope at this infrared wavelength (the K-band at 2.2 µm). It represents the maximum resolution (image sharpness) obtainable when observing with a single telescope. As explained in the text, the interferometric "addition" of more telescopes greatly improves that resolution. The width of the individual - slightly S-shaped - lines ("fringes") in the inclined pattern visible in the inner area, about 0.003 arcsec, represents the achieved interferometric resolution in one direction (with an angular diameter of about 0.002 arcsec, the disk of Achernar is not resolved, making it a suitable object for this resolution test). The resolution in the perpendicular direction (along the lines) is evidently less - this is due to the specific (elongated) baseline pattern during these test observations (left panel). The image provides a direct illustration of the 20-fold increase in resolution of the VLTI over a single 8.2-m telescope . At this moment, three delay lines have been installed, but for the present first test, the VLTI engineers and astronomers used the telescopes in pairs, in order to set-up the various equipment configurations properly. In this way, they could also start "teaching" the computer control software to handle this very demanding process as efficiently and user-friendly as possible in the future. With the arrival of the science instrument AMBER in mid-2003, up to three beams can be combined simultaneously. It turned out that the various predictions of mirror positions and angles were quite accurate and only a moderate amount of time was needed to "obtain fringes" in all different configurations. Measurements were then made on a number of stars, among them the brightest star in the southern constellation Eridanus (The River), known as Alpha Eridani or Achernar , that was observed several times with the different telescope pairings. This star is a hot dwarf (spectral type "B5 IV") that is located at a distance of about 145 light-years. It has also been extensively observed during earlier VLTI tests. It is a very suitable object for the present resolution tests as its angular diameter is only about 0.002 arcsec and it therefore remains unresolved at the near-infrared wavelength of the K-band used (2.2 µm). In fact, the combination of these data (including also some that were obtained in October 2001) now makes it possible to reconstruct the first interferometric "point-spread function (PSF)" of a star obtained with the VLTI , cf. PR Photo 22b/02 . This is like an "interferometric image", except that the disk of this particular star remains unresolved. The angular resolution is inversely proportional to the aperture of a telescope for single telescope observation, and to the length of the "baseline" between two telescopes for the interferometric observation. However, observing interferometrically with two telescopes will improve the resolution only in the direction parallel to this baseline, while the resolution in the perpendicular direction will remain that of a single telescope. But then the use of other telescope pairs with different baseline orientations "adds" resolution in other directions. The reconstructed PSF of Achernar shown in PR Photo 22b/02 is obviously still very incomplete, due to the technical nature of the present tests and the limited time that was spent observing the star in each configuration. However, it already presents a powerful illustration of the extreme imaging sharpness that will be achieved with the VLTI.

New constraints on the disk characteristics and companion candidates around T Chamaeleontis with VLT/SPHERE

NASA Astrophysics Data System (ADS)

Pohl, A.; Sissa, E.; Langlois, M.; Müller, A.; Ginski, C.; van Holstein, R. G.; Vigan, A.; Mesa, D.; Maire, A.-L.; Henning, Th.; Gratton, R.; Olofsson, J.; van Boekel, R.; Benisty, M.; Biller, B.; Boccaletti, A.; Chauvin, G.; Daemgen, S.; de Boer, J.; Desidera, S.; Dominik, C.; Garufi, A.; Janson, M.; Kral, Q.; Ménard, F.; Pinte, C.; Stolker, T.; Szulágyi, J.; Zurlo, A.; Bonnefoy, M.; Cheetham, A.; Cudel, M.; Feldt, M.; Kasper, M.; Lagrange, A.-M.; Perrot, C.; Wildi, F.

2017-09-01

Context. The transition disk around the T Tauri star T Cha possesses a large gap, making it a prime target for high-resolution imaging in the context of planet formation. Aims: We aim to find signs of disk evolutionary processes by studying the disk geometry and the dust grain properties at its surface, and to search for companion candidates. Methods: We analyze a set of VLT/SPHERE data at near-infrared and optical wavelengths. We performed polarimetric imaging of T Cha with IRDIS (1.6 μm) and ZIMPOL (0.5-0.9 μm), and obtained intensity images from IRDIS dual-band imaging with simultaneous spectro-imaging with IFS (0.9-1.3 μm). Results: The disk around T Cha is detected in all observing modes and its outer disk is resolved in scattered light with unprecedented angular resolution and signal-to-noise. The images reveal a highly inclined disk with a noticeable east-west brightness asymmetry. The significant amount of non-azimuthal polarization signal in the Uφ images, with a Uφ/Qφ peak-to-peak value of 14%, is in accordance with theoretical studies on multiple scattering in an inclined disk. Our optimal axisymmetric radiative transfer model considers two coplanar inner and outer disks, separated by a gap of 0.̋28 ( 30 au) in size, which is larger than previously thought. We derive a disk inclination of 69 deg and PA of 114 deg. In order to self-consistently reproduce the intensity and polarimetric images, the dust grains, responsible for the scattered light, need to be dominated by sizes of around ten microns. A point source is detected at an angular distance of 3.5'' from the central star. It is, however, found not to be co-moving. Conclusions: We confirm that the dominant source of emission is forward scattered light from the near edge of the outer disk. Our point source analysis rules out the presence of a companion with mass larger than 8.5 Mjup between 0.̋1 and 0.̋3. The detection limit decreases to 2 Mjup for 0.̋3 to 4.0''. Based on observations made with European Southern Observatory (ESO) telescopes at the Paranal Observatory in Chile, under program IDs 095.C-0298(B), 096.C-0248(B) and 096.C-0248(C).

The ecological and construct validity of a newly developed measure of executive function: the Virtual Library Task.

PubMed

Renison, Belinda; Ponsford, Jennie; Testa, Renee; Richardson, Barry; Brownfield, Kylie

2012-05-01

Virtual reality (VR) assessment paradigms have the potential to address the limited ecological validity of pen and paper measures of executive function (EF) and the pragmatic and reliability issues associated with functional measures. To investigate the ecological validity and construct validity of a newly developed VR measure of EF, the Virtual Library Task (VLT); a real life analogous task--the Real Library Task (RLT); and five neuropsychological measures of EF were administered to 30 patients with traumatic brain injury (TBI) and 30 healthy Controls. Significant others for each participant also completed the Dysexecutive Questionnaire (DEX), which is a behavioral rating scale of everyday EF. Performances on the VLT and the RLT were significantly positively correlated indicating that VR performance is similar to real world performance. The TBI group performed significantly worse than the Control group on the VLT and the Modified Six Elements Test (MSET) but the other four neuropsychological measures of EF failed to differentiate the groups. Both the MSET and the VLT significantly predicted everyday EF suggesting that they are both ecologically valid tools for the assessment of EF. The VLT has the advantage over the MSET of providing objective measurement of individual components of EF.

Molecules and Dust in the Humunculus: Ejecta of Eta Carinae

NASA Technical Reports Server (NTRS)

Gull, T.

2007-01-01

In the 18401s, Eta Carinae ejected massive amounts of nitrogen-rich, carbon- and oxygen-poor material which we see as the hourglass-shaped Homunculus. With the Hubble Space Telescope Imaging Spectrograph, we detected multiple shells in line of sight, the most massive and intriguing being at -513 km/s. Numerous lines of Fe I, Fe II, Ni II, Cr II, Sc II, Sr II, Ti II, V II, etc are identified as well as nearly a thousand H2 lines. The metals have energy level populations consistent with 760K and excited by photons < 8.5eV. We have now identified CH, CH+, OH, and NH at the same velocity, but at 60K, suggesting stratification in the outer ejecta. Analysis of the interior, photoionized emission hourglass structure, known as the Little Homunculus, indicates He, N overabundances and C, 0 underabundances (approximately 1/80 solar). A skirt of neutral and partially ionized gas lies between the lobes of the hourglasses. A portion is seen as the Strontium Filament, a metal- ionized, neutral hydrogen structure. Relative abundances of TiNi are 1/80 solar, CrNi are 1/20 solar. This complex of ejecta appears to have been ejected by a massive star(s) at the end of the hydrogen-burning phase when convection led to overproduction of nitrogen at the expense of carbon and oxygen. Given the underabundances of carbon and oxygen, the chemistry of this system is quite different to the normal ISM, leading to a nitrogen- dominated chemistry. What little C and 0 that is formed is immediately taken up by SiO and Al0 molecules leading to a very different gas/dust ratio than the normal ISM. Dust in this ejecta is abundance, but known to be very grey in character. Observations with HST/STIS and VLT/UVES will be presented along with simple physical models and CLOUD modeling. Insight by the participants will be solicited.

ESO Delegation to Visit Chile: the Chile-Eso Treaty and Paranal

NASA Astrophysics Data System (ADS)

1994-05-01

The ESO Council, in its extraordinary session on 28 April 1994, among other matters discussed the relations with the Republic of Chile and the situation around Paranal mountain [1], the designated site for the ESO Very Large Telescope (VLT). Council decided to send a high ranking delegation to Santiago de Chile to discuss with Chilean authorities the pending problems, including the finalisation of the new Treaty between the Republic of Chile and ESO and the legal aspects of the Paranal location. The ESO delegation will consist of Dr. Peter Creola (President of ESO Council), Dr. Catherine Cesarsky (Vice-President of ESO Council), Dr. Henrik Grage (Former Vice-President of ESO Council) and Professor Riccardo Giacconi (ESO Director General), the latter accompanied by his advisers. The delegation will arrive in Chile during the second half of May 1994. The ESO delegation will meet with the Chilean Minister of Foreign Affairs, Mr. Carlos Figueroa, and the Secretary of State in the Ministry of Foreign Affairs, Mr. Jose Miguel Insulza. Other meetings at high level are being planned. The delegation will report about these discussions to the ESO Council during its ordinary session on 7 - 8 June 1994. FOUR PARANAL PHOTOS AVAILABLE A series of four photos which show the current status of the work at Paranal has been prepared. Photographic colour prints for use by the media can be requested from the ESO Information and Photographic Service (please remember to indicate the identification numbers). [1] See ESO Press Release 07/94 of 21 April 1994. PHOTO CAPTIONS ESO PR PHOTO 08/94-1: CERRO PARANAL This aerial photo of the Paranal mountain, the designated site for the ESO Very Large Telescope (VLT), was obtained on 22 March 1994. Paranal is situated in the driest part of the Chilean Atacama desert, approx. 130 km south of the city of Antofagasta, and about 12 km from the Pacific Ocean. In this view towards the West, the ocean is seen in the background. The altitude is 2650 metres. The top of the mountain has been levelled to make place for the extensive VLT installations. ESO has constructed a road from the main road in the area (the ``Old Panamericana'') to the summit. It passes by the ESO base camp (in the foreground, left of the road). The constructors' camp is located on the other side of the road. This photo (ESO PR Photo 08/94-1) accompanies ESO Press Release 08/94 of 6 May 1994 and may be reproduced, if credit is given to the European Southern Observatory. ESO PR PHOTO 08/94-2: CERRO PARANAL This aerial photo of the Paranal mountain, the designated site for the ESO Very Large Telescope (VLT), was obtained on 22 March 1994. Paranal is located in the driest part of the Chilean Atacama desert, approx. 130 km south of the city of Antofagasta, and about 12 km from the Pacific Ocean. The altitude is 2650 metres. In this view towards the East, the high mountains of the Andean Cordillera are in the background. The top of the mountain has been levelled to make place for the extensive VLT installations. The four excavations for the buildings that will house the four 8.2 metre VLT unit telescopes are clearly seen. There are some dust clouds from the construction activity at the site. There are several other peaks in this area which may possibly be used for astronomical installations. The one to the left on which some site testing equipment can be seen, is known as the ``NTT Peak''. This photo (ESO PR Photo 08/94-2) accompanies ESO Press Release 08/94 of 6 May 1994 and may be reproduced, if credit is given to the European Southern Observatory. ESO PR PHOTO 08/94-3: CERRO PARANAL This aerial photo of the Paranal mountain, the designated site for the ESO Very Large Telescope (VLT), was obtained on 22 March 1994. Paranal is located in the driest part of the Chilean Atacama desert, approx. 130 km south of the city of Antofagasta, and about 12 km from the Pacific Ocean. The altitude is 2650 metres. The top of the mountain has been levelled to make place for the extensive VLT installations. The four excavations for the buildings that will house the four 8.2 metre VLT unit telescopes are clearly seen. The positions of some of the future structures have been marked. The control building will be located on the platform at the rightmost edge of the mountain. This photo (ESO PR Photo 08/94-3) accompanies ESO Press Release 08/94 of 6 May 1994 and may be reproduced, if credit is given to the European Southern Observatory. ESO PR PHOTO 08/94-4: CERRO PARANAL This photo of the ESO Base Camp at the foot of the Paranal mountain, the designated site for the ESO Very Large Telescope (VLT), was obtained in late March 1994. Paranal is located in the driest part of the Chilean Atacama desert, approx. 130 km south of the city of Antofagasta, and about 12 km from the Pacific Ocean. The altitude is 2650 metres. The top of the mountain has been levelled to make place for the extensive VLT installations. This photo (ESO PR Photo 08/94-4) accompanies ESO Press Release 08/94 of 6 May 1994 and may be reproduced, if credit is given to the European Southern Observatory.

High-Resolution Mid-IR Imaging of Jupiter's Great Red Spot: Comparing Cassini, VLT and Subaru Observations

NASA Astrophysics Data System (ADS)

Fletcher, Leigh N.; Orton, G. S.; Yanamandra-Fisher, P.; Irwin, P. G. J.; Baines, K. H.; Edkins, E.; Line, M. R.; Mousis, O.; Parrish, P. D.; Vanzi, L.; Fuse, T.; Fujoyoshi, T.

2008-09-01

In the eight years since the Cassini fly-by of Jupiter, the spatial resolution of ground-based observations of Jupiter's giant anticyclonic storm systems (the Great Red Spot, Oval BA and others) using 8m-class telescopes has surpassed the resolution of the Cassini/CIRS maps. We present a time-series of mid-IR imaging of the Great Red Spot (GRS) and its environs from the VISIR instrument on the Very Large Telescope (UT3/Melipal) and the COMICS instrument on the Subaru telescope (Hawaii). The NEMESIS optimal-estimation retrieval algorithm (Irwin et al., 2008) is used to analyse both the 7-25 micron filtered imaging from 2005-2008 and Cassini/CIRS 7-16 micron data from 2000. We demonstrate the ability to map temperatures in the 100-400 mbar range, NH3, aerosol opacity and the para-H2 fraction from the filtered imaging. Furthermore, the Cassini/CIRS spectra are used to map the PH3 mole fraction around the GRS. The thermal field, gaseous composition and aerosol distribution are used as diagnostics for the atmospheric motion associated with the GRS. Changes in the atmospheric state in response to close encounters with Oval BA and other vortices will be assessed. These results will be discussed in light of their implications for the planning of the Europa-Jupiter System Mission.

CFBDSIR 2149-0403: young isolated planetary-mass object or high-metallicity low-mass brown dwarf?

NASA Astrophysics Data System (ADS)

Delorme, P.; Dupuy, T.; Gagné, J.; Reylé, C.; Forveille, T.; Liu, M. C.; Artigau, E.; Albert, L.; Delfosse, X.; Allard, F.; Homeier, D.; Malo, L.; Morley, C.; Naud, M. E.; Bonnefoy, M.

2017-06-01

Aims: We conducted a multi-wavelength, multi-instrument observational characterisation of the candidate free-floating planet CFBDSIR J214947.2-040308.9, a late T-dwarf with possible low-gravity features, in order to constrain its physical properties. Methods: We analysed nine hours of X-shooter spectroscopy with signal detectable from 0.8 to 2.3 μm, as well as additional photometry in the mid-infrared using the Spitzer Space Telescope. Combined with a VLT/HAWK-I astrometric parallax, this enabled a full characterisation of the absolute flux from the visible to 5 μm, encompassing more than 90% of the expected energy emitted by such a cool late T-type object. Our analysis of the spectrum also provided the radial velocity and therefore the determination of its full 3D kinematics. Results: While our new spectrum confirms the low gravity and/or high metallicity of CFBDSIR 2149, the parallax and kinematics safely rule out membership to any known young moving group, including AB Doradus. We use the equivalent width of the K I doublet at 1.25 μm as a promising tool to discriminate the effects of low-gravity from the effects of high-metallicity on the emission spectra of cool atmospheres. In the case of CFBDSIR 2149, the observed K I doublet clearly favours the low-gravity solution. Conclusions: CFBDSIR 2149 is therefore a peculiar late-T dwarf that is probably a young, planetary-mass object (2-13 MJup, <500 Myr) possibly similar to the exoplanet 51 Eri b, or perhaps a 2-40 MJup brown dwarf with super-solar metallicity. Based on observations obtained with X-shooter on VLT-UT2 at ESO-Paranal (run 091.D-0723). Based on observations obtained with HAWKI on VLT-UT4 (run 089.C-0952, 090.C-0483, 091.C-0543,092.C-0548,293.C-5019(A) and run 086.C-0655(A)). Based on observations obtained with ISAAC on VLT-UT3 at ESO-Paranal (run 290.C-5083). Based on observation obtained with WIRCam at CFHT (program 2012BF12). Based on Spitzer Space telescope DDT observation (program 10166).

Design of the VLT data flow model

NASA Astrophysics Data System (ADS)

Peron, Michele; Grosbol, Preben

1997-03-01

The basic objective of modern observatories is to globally maximize their efficiency and ensure a high, constant and predictable data quality. These challenges can only be met if the scientific operation of such facilities, from the submission of observing programs to the archiving of all information, is carried out in a consistent and well controlled manner. The size, complexity and long operational lifetime of such systems make it difficult to predict and control their behavior with the necessary accuracy. Moreover they are subject to changes and are cumbersome to maintain. We present in this paper an object-oriented end-to-end operations model which describes the flow of science data associated with the operation of the VLT. The analysis model helped us to get a clear understanding of the problem domain. We were able in the design phase to partition the system into subsystems, each of them being allocated to a team for detailed design and implementation. Each of these subsystems is addressed in this paper. Prototypes will be implemented in the near future and tested on the new technology telescope (NTT). They will allow us to clarify the astronomical requirements and check the new operational concepts introduced to meet the ambitious goals of the VLT.

VizieR Online Data Catalog: IMF in 3 low-redshift strong lenses from SNELLS (Newman+, 2017)

NASA Astrophysics Data System (ADS)

Newman, A. B.; Smith, R. J.; Conroy, C.; Villaume, A.; van Dokkum, P.

2018-04-01

The SINFONI Nearby Elliptical Lens Locator Survey (SNELLS) lenses (Smith+ 2015MNRAS.449.3441S) were observed using the IMACS spectrograph at the 6.5m Magellan Baade telescope during 2015 April 9-10 and 2015 September 25. Spectroscopic observations cover the wavelength range 3565-9415Å continuously with a uniform resolution of 2.8Å. Total exposure times ranged from 60 minutes to 100 minutes per grating. See section 2.1. All SNELLS lenses were also observed using FIRE, a near-infrared echellete spectrograph at the Magellan Baade telescope, during the nights of 2015 April 8, May 3, and September 25. The FIRE spectra cover 0.82-2.51um, but in this paper we use only the region around the Wing-Ford band of FeH near 9916Å for SNL-0 and SNL-1. On-target exposure times for SNL-0 and SNL-1 were 32 minutes and 54 minutes, respectively. The 1" wide slit provided a resolution of R~4000. See section 2.2. We acquired optical and near-infrared spectra for all the SNELLS lenses with X-shooter at the 8.2m UT2 of the ESO Very Large Telescope (VLT). See section 2.3. We obtained r-band images of SNL-1 and SNL-2 using the LDSS-3 imaging spectrograph at the Magellan 2 telescope. Photometric calibration was tied to the SDSS DR9. For SNL-0, we used Hubble Heritage observations taken with the Advanced Camera for Surveys and the F625W filter (Proposal 10710). When constructing our dynamical model of SNL-2, we also use an R-band image obtained in excellent seeing with FORS2 at the VLT. See section 2.4. (2 data files).

The Galactic Centre Mini-Spiral in the MM-Regime

NASA Technical Reports Server (NTRS)

Kunneriath, D.; Eckart, A.; Vogel, S. N.; Teuben, P.; Muzic, I.; Schoedel, R.; Garcia-Marin, M.; Moultaka, J.; Staguhn, J.; Straubmeier, C.;

ESO Council Visits First VLT Unit Telescope Structure in Milan

NASA Astrophysics Data System (ADS)

1995-12-01

As the ESO Very Large Telescope (VLT) rapidly takes on shape, Europe has just come one step closer to the realisation of its 556 million DEM astronomical showcase project. Last week, the ESO Council held its semi-annual meeting in Milan (Italy) [1]. During a break in the long agenda list, Council members had the opportunity to visit the Ansaldo factory in the outskirts of this city and to see for the first time the assembled mechanical structure of one of the four 8.2-metre VLT Unit telescopes. This Press Release is accompanied by a photo that shows the ESO Council delegates in front of the giant telescope. After a long climb up the steep staircase to the large Nasmyth platform at the side of the telescope where the astronomical instruments will later be placed, Dr. Peter Creola (Switzerland) , President of the ESO Council and a mechanics expert, grabbed the handrail and surveyed the structure with a professional eye: `I knew it was going to be big, but not that enormous!', he said. Other delegates experienced similar feelings, especially when they watched the 430 tonnes of steel in the 24-metre tall and squat structure turn smoothly and silently around the vertical axis. The Chairman of the ESO Scientific Technical Committee (STC), Dr. Johannes Andersen (Denmark) , summarized his first, close encounter with the VLT by `This is great fun!' and several of his colleague astronomers were soon seen in various corners of the vast structure, engaged in elated discussions about the first scientific investigations to be done with the VLT in two years' time. The VLT Main Structures The visit by Council took place at the invitation of Ansaldo Energia S.p.A. (Genova), EIE-European Industrial Engineering S.r.I. (Venice) and SOIMI-Societa Impianti Industriale S.p.A. (Milan), the three Italian enterprises responsible for the construction of the main structures of the VLT 8.2-metre Unit telescopes. Short speeches were given on this occasion by Drs. Ferruccio Bressani (Ansaldo), Luigi Guiffrida (SOIMI), Gianpietro Marchiori (EIE) and Prof. Massimo Tarenghi (ESO), describing the very successful implementation of this major VLT contract that was awarded by ESO in September 1991 [2]. All speakers praised the good collaboration between ESO and its industrial partners and Prof. Riccardo Giacconi , Director General of ESO, expressed his satisfaction `with the splendid performance of the ESO-Industry team which was bringing us close to the realisation of the premier telescope array in optical ground-based astronomy in the world'. The participants were also pleased to listen to several of the Italian engineers present who commented on the very positive experience of being personally involved in the world's largest telescope project. The VLT telescope structures incorporate many new technological concepts. Thanks to these and careful planning of the many components and their integration, it has been possible to achieve, among others, light weight construction, high mechanical stiffness, good thermal equilibrium with the ambient air (of importance for the seeing during the observations), low electromagnetic emissitivity (i.e. low interference with the sensitive astronomical instruments) and easy maintainability. Of particular interest is also the giant, direct drive system with a diameter of 9 metres and the sophisticated, innovative laser encoder system. In this way, there is no direct contact between the moving parts and the friction during the rotation is kept at an absolute minimum. The Next Steps The ESO VLT project is now entering into a decisive phase and the next years will see an increasing number of telescope parts and instruments from the scientific and industrial laboratories of Europe converging towards the VLT observatory at Cerro Paranal in Chile. It is gratifying that, despite its high degree of complexity and incorporation of a substantial number of new technologies, the project is within schedule and budget. There will be several important milestones in 1996. During the next two months, the mounting of the mechanical structure in Milan will be completed. Following this, a group of ESO hard- and software experts will spend about 6 months next to it, implementing and thoroughly testing all aspects of the very advanced VLT telescope control system. In the meantime, the erection of the first telescope enclosure at Paranal is rapidly proceeding and the outside panelling will soon be put in place. This work will be completed in January 1996, after which the integration of all inside mechanical components will follow. The take-over by ESO of the fully operational, first enclosure is scheduled for May 1996. The other enclosures will become ready at regular intervals thereafter. In Milan, all of the heavy parts of the second telescope structure have already been produced and the third and fourth are about 60 percent complete. While the first structure has now been pre-assembled for tests, the individual parts of the second will not be put together before they are shipped to Paranal in early 1996. Starting in June 1996, they will then be assembled inside the completed, first enclosure. Thus, the `second' structure will become the `first' VLT Unit telescope (UT1). This work will last until early 1997, after which the first 8.2-metre mirror will arrive from Europe and be installed. Finally, after another test and optimisation period, `first light' for UT1 is expected in late 1997. This procedure is very advantageous, because it allows to continue under less time pressure the extensive tests on the `first' structure in Milan until a satisfactory state of debugging and optimisation of the new VLT control system has been reached. In this way, the time necessary for the installation of this system in UT1 at Paranal in 1997 will be significantly shortened. In fact, the structure seen by the ESO Council in Milan will be the last to be shipped to Paranal where it will then become the fourth 8.2-metre Unit telescope (UT4). Mirrors and Instruments As earlier announced, ESO officially received the first 8.2-metre VLT mirror from REOSC in Paris [3] on November 21. The polishing of the second mirror has already started and, based on the experience gained with the first, it is expected that this work will be accomplished in less time. The third blank is already at REOSC and the fourth will soon be ready at Schott Glaswerke in Mainz (Germany). Following extended studies, and as yet another move towards new technology within the VLT project, it has now been decided to make the 1.2-metre secondary VLT mirrors of beryllium, a very light, exotic metal. The contracting firm is Dornier of the DASA group (Germany). This saves much weight and allows these relatively large mirrors to be efficiently used in the `chopping and tilting' mode needed for observations in the infrared wavelength region as well as for the critical, image-sharpening adaptive optics system. Significant progress has also been achieved on the first astronomical instruments which will be installed at the VLT. The integration of the first two of these, ISAAC and CONICA which will be installed on UT1 in the course of 1997, has already started in the ESO laboratories at the Headquarters in Garching. Important advances have also taken place within the FORS (managed by a consortium of Landessternwarte Heidelberg, Universitaets-Sternwarte Goettingen and Institut fuer Astronomie und Astrophysik der Ludwig Maximilians Universitaet Muenchen) and FUEGOS (Paris Observatory, Meudon Observatory, Toulouse Observatory, Geneva Observatory and Bologna Observatory) projects. More details about these and other VLT instruments will be given in later communications. Notes: [1] The Council of ESO consists of two representatives from each of the eight member states. It is the highest legislative authority of the organisation and normally meets twice a year. This time, Council was invited to Milan by the Director of the Osservatorio di Brera (Milan), Prof. Guido Chincarini, and the Italian delegation. [2] See ESO Press Release 08/91 of 24 September 1991. [3] See ESO Press Release 15/95 of 13 November 1995. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

VLT near- to mid-IR imaging and spectroscopy of the M 17 UC1 - IRS5 region

NASA Astrophysics Data System (ADS)

Chen, Zhiwei; Nürnberger, Dieter E. A.; Chini, Rolf; Jiang, Zhibo; Fang, Min

2015-06-01

Aims: We investigate the surroundings of the hypercompact H ii region M 17 UC1 to probe the physical properties of the associated young stellar objects and the environment of massive star formation. Methods: We use diffraction-limited near-IR (VLT/NACO) and mid-IR (VLT/VISIR) images to reveal the different morphologies at various wavelengths. Likewise, we investigate the stellar and nebular content of the region with VLT/SINFONI integral field spectroscopy with a resolution R ˜ 1500 at H + K bands. Results: Five of the seven point sources in this region show L-band excess emission. A geometric match is found between the H2 emission and near-IR polarized light in the vicinity of IRS5A, and between the diffuse mid-IR emission and near-IR polarization north of UC1. The H2 emission is typical for dense photodissociation regions (PDRs), which are initially far-ultraviolet pumped and repopulated by collisional de-excitation. The spectral types of IRS5A and B273A are B3-B7 V/III and G4-G5 III, respectively. The observed infrared luminosity LIR in the range 1-20 μm is derived for three objects; we obtain 2.0 × 103 L⊙ for IRS5A, 13 L⊙ for IRS5C, and 10 L⊙ for B273A. Conclusions: IRS5 might be a young quadruple system. Its primary star IRS5A is confirmed to be a high-mass protostellar object (˜9 M⊙, ˜1 × 105 yrs); it might have terminated accretion due to the feedback from stellar activities (radiation pressure, outflow) and the expanding H ii region of M 17. The object UC1 might also have terminated accretion because of the expanding hypercompact H ii region, which it ionizes. The disk clearing process of the low-mass young stellar objects in this region might be accelerated by the expanding H ii region. The outflows driven by UC1 are running south-north with its northeastern side suppressed by the expanding ionization front of M 17; the blue-shifted outflow lobe of IRS5A is seen in two types of tracers along the same line of sight in the form of H2 emission filament and mid-emission. The H2 line ratios probe the properties of M 17 SW PDR, which is confirmed to have a clumpy structure with two temperature distributions: warm, dense molecular clumps with nH> 105 cm-3 and T ≈ 575 K and cooler atomic gas with nH ˜ 3.7 × 103-1.5 × 104 cm-3 and T ˜ 50 - 200 K. Based on observations by the European Southern Observatory Very Large Telescope on Cerro Paranal, Chile (ESO program IDs: 281.C-5027(A), 281.C-5051(A, B)).

VLTI auxiliary telescopes: a full object-oriented approach

NASA Astrophysics Data System (ADS)

Chiozzi, Gianluca; Duhoux, Philippe; Karban, Robert

2000-06-01

The Very Large Telescope (VLT) Telescope Control Software (TCS) is a portable system. It is now in use or will be used in a whole family of ESO telescopes VLT Unit Telescopes, VLTI Auxiliary Telescopes, NTT, La Silla 3.6, VLT Survey Telescope and Astronomical Site Monitors in Paranal and La Silla). Although it has been developed making extensive usage of Object Oriented (OO) methodologies, the overall development process chosen at the beginning of the project used traditional methods. In order to warranty a longer lifetime to the system (improving documentation and maintainability) and to prepare for future projects, we have introduced a full OO process. We have taken as a basis the United Software Development Process with the Unified Modeling Language (UML) and we have adapted the process to our specific needs. This paper describes how the process has been applied to the VLTI Auxiliary Telescopes Control Software (ATCS). The ATCS is based on the portable VLT TCS, but some subsystems are new or have specific characteristics. The complete process has been applied to the new subsystems, while reused code has been integrated in the UML models. We have used the ATCS on one side to tune the process and train the team members and on the other side to provide a UML and WWW based documentation for the portable VLT TCS.

Alcohol affects video lottery terminal (VLT) gambling behaviors and cognitions differently.

PubMed

Ellery, Michael; Stewart, Sherry H

2014-03-01

People frequently combine alcohol use and gambling. However, our understanding of the effects of alcohol on gambling behavior is limited, both in terms of what the effects are and how they occur. The effects of a moderately intoxicating dose of alcohol (i.e., a blood alcohol concentration of .06 g%) on the video lottery terminal (VLT) gambling behaviors and cognitions of community-recruited nonpathological (n = 30) and probable pathological gamblers (n = 30) were compared. Alcohol increased the rate of double up betting (i.e., choosing to play a bonus game, after a winning video poker hand, which involves trying to pick a higher ranked card than the dealer's card from among 5 face down cards) of probable pathological gamblers, but did not influence their irrational beliefs about VLT play. Alcohol maintained the irrational beliefs about VLT play of nonpathological gamblers, but did not influence their gambling behaviors. Results are consistent with a growing body of research finding that gambling cognitions have an equivocal role in explaining actual gambling behaviors. Potential mechanisms for the observed effects are discussed. Applied implications discussed include: educating regular VLT players about the effects of alcohol on irrational gambling cognitions; reconsidering policies and practices that make alcohol available where machine gambling takes place; and targeting even moderate alcohol use in the treatment of gambling problems.

Sparse aperture masking at the VLT. II. Detection limits for the eight debris disks stars β Pic, AU Mic, 49 Cet, η Tel, Fomalhaut, g Lup, HD 181327 and HR 8799

NASA Astrophysics Data System (ADS)

Gauchet, L.; Lacour, S.; Lagrange, A.-M.; Ehrenreich, D.; Bonnefoy, M.; Girard, J. H.; Boccaletti, A.

2016-10-01

Context. The formation of planetary systems is a common, yet complex mechanism. Numerous stars have been identified to possess a debris disk, a proto-planetary disk or a planetary system. The understanding of such formation process requires the study of debris disks. These targets are substantial and particularly suitable for optical and infrared observations. Sparse aperture masking (SAM) is a high angular resolution technique strongly contributing to probing the region from 30 to 200 mas around the stars. This area is usually unreachable with classical imaging, and the technique also remains highly competitive compared to vortex coronagraphy. Aims: We aim to study debris disks with aperture masking to probe the close environment of the stars. Our goal is either to find low-mass companions, or to set detection limits. Methods: We observed eight stars presenting debris disks (β Pictoris, AU Microscopii, 49 Ceti, η Telescopii, Fomalhaut, g Lupi, HD 181327, and HR 8799) with SAM technique on the NaCo instrument at the Very Large Telescope (VLT). Results: No close companions were detected using closure phase information under 0.5'' of separation from the parent stars. We obtained magnitude detection limits that we converted to Jupiter masses detection limits using theoretical isochrones from evolutionary models. Conclusions: We derived upper mass limits on the presence of companions in the area of a few times the telescope's diffraction limits around each target star. Based on observations collected at the European Southern Observatory (ESO) during runs 087.C-0450(A), 087.C-0450(B) 087.C-0750(A), 088.C-0358(A).All magnitude detection limits maps are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/595/A31

New disk discovered with VLT/SPHERE around the M star GSC 07396-00759

NASA Astrophysics Data System (ADS)

Sissa, E.; Olofsson, J.; Vigan, A.; Augereau, J. C.; D'Orazi, V.; Desidera, S.; Gratton, R.; Langlois, M.; Rigliaco, E.; Boccaletti, A.; Kral, Q.; Lazzoni, C.; Mesa, D.; Messina, S.; Sezestre, E.; Thébault, P.; Zurlo, A.; Bhowmik, T.; Bonnefoy, M.; Chauvin, G.; Feldt, M.; Hagelberg, J.; Lagrange, A.-M.; Janson, M.; Maire, A.-L.; Ménard, F.; Schlieder, J.; Schmidt, T.; Szulágyi, J.; Stadler, E.; Maurel, D.; Delboulbé, A.; Feautrier, P.; Ramos, J.; Rigal, F.

2018-05-01

Debris disks are usually detected through the infrared excess over the photospheric level of their host star. The most favorable stars for disk detection are those with spectral types between A and K, while the statistics for debris disks detected around low-mass M-type stars is very low, either because they are rare or because they are more difficult to detect. Terrestrial planets, on the other hand, may be common around M-type stars. Here, we report on the discovery of an extended (likely) debris disk around the M-dwarf GSC 07396-00759. The star is a wide companion of the close accreting binary V4046 Sgr. The system probably is a member of the β Pictoris Moving Group. We resolve the disk in scattered light, exploiting high-contrast, high-resolution imagery with the two near-infrared subsystems of the VLT/SPHERE instrument, operating in the Y J bands and the H2H3 doublet. The disk is clearly detected up to 1.5'' ( 110 au) from the star and appears as a ring, with an inclination i 83°, and a peak density position at 70 au. The spatial extension of the disk suggests that the dust dynamics is affected by a strong stellar wind, showing similarities with the AU Mic system that has also been resolved with SPHERE. The images show faint asymmetric structures at the widest separation in the northwest side. We also set an upper limit for the presence of giant planets to 2 MJ. Finally, we note that the 2 resolved disks around M-type stars of 30 such stars observed with SPHERE are viewed close to edge-on, suggesting that a significant population of debris disks around M dwarfs could remain undetected because of an unfavorable orientation. Based on data collected at the European Southern Observatory, Chile (ESO Program 198.C-0298).

VLT spectroscopy of XTE J2123-058 during quiescence: the masses of the two components

NASA Astrophysics Data System (ADS)

Casares, J.; Dubus, G.; Shahbaz, T.; Zurita, C.; Charles, P. A.

2002-01-01

We present Very Large Telescope (VLT) low-resolution spectroscopy of the neutron star X-ray transient XTE J2123-058 during its quiescent state. Our data reveal the presence of a K7V companion which contributes 77 per cent to the total flux at λ6300 and orbits the neutron star at K2=287+/-12kms-1. Contrary to other soft X-ray transients (SXTs), the Hα emission is almost exactly in antiphase with the velocity curve of the optical companion. Using the light-centre technique we obtain K1=140+/-27kms-1 and hence q=K1/K2=M2/M1=0.49+/-0.10. This, combined with a previous determination of the inclination angle (i=73°+/-4°) yields M1=1.55+/-0.31Msolar and M2=0.76+/-0.22Msolar. M2 agrees well with the observed spectral type. Doppler tomography of the Hα emission shows a non-symmetric accretion disc distribution mimicking that seen in SW Sex stars. Although we find a large systemic velocity of - 110+/-8kms-1 this value is consistent with the galactic rotation velocity at the position of J2123-058, and hence a halo origin. The formation scenario of J2123-058 is still unresolved.

New ATCA, ALMA and VISIR observations of the candidate LBV SK -67 266 (S61): the nebular mass from modelling 3D density distributions

NASA Astrophysics Data System (ADS)

Agliozzo, C.; Nikutta, R.; Pignata, G.; Phillips, N. M.; Ingallinera, A.; Buemi, C.; Umana, G.; Leto, P.; Trigilio, C.; Noriega-Crespo, A.; Paladini, R.; Bufano, F.; Cavallaro, F.

2017-04-01

We present new observations of the nebula around the Magellanic candidate Luminous Blue Variable S61. These comprise high-resolution data acquired with the Australia Telescope Compact Array (ATCA), the Atacama Large Millimetre/Submillimetre Array (ALMA), and the VLT Imager and Spectrometer for mid Infrared (VISIR) at the Very Large Telescope. The nebula was detected only in the radio, up to 17 GHz. The 17 GHz ATCA map, with 0.8 arcsec resolution, allowed a morphological comparison with the Hα Hubble Space Telescope image. The radio nebula resembles a spherical shell, as in the optical. The spectral index map indicates that the radio emission is due to free-free transitions in the ionized, optically thin gas, but there are hints of inhomogeneities. We present our new public code RHOCUBE to model 3D density distributions and determine via Bayesian inference the nebula's geometric parameters. We applied the code to model the electron density distribution in the S61 nebula. We found that different distributions fit the data, but all of them converge to the same ionized mass, ˜ 0.1 M⊙, which is an order of magnitude smaller than previous estimates. We show how the nebula models can be used to derive the mass-loss history with high-temporal resolution. The nebula was probably formed through stellar winds, rather than eruptions. From the ALMA and VISIR non-detections, plus the derived extinction map, we deduce that the infrared emission observed by space telescopes must arise from extended, diffuse dust within the ionized region.

The peculiar Na-O anticorrelation of the bulge globular cluster NGC 6440

NASA Astrophysics Data System (ADS)

Muñoz, C.; Villanova, S.; Geisler, D.; Saviane, I.; Dias, B.; Cohen, R. E.; Mauro, F.

2017-08-01

Context. Galactic globular clusters (GCs) are essential tools for understanding the earliest epoch of the Milky Way, since they are among the oldest objects in the Universe and can be used to trace its formation and evolution. Current studies using high-resolution spectroscopy for many stars in each of a large sample of GCs allow us to develop a detailed observational picture of their formation and their relation with the Galaxy. However, it is necessary to complete this picture by including GCs that belong to all major Galactic components, including the bulge. Aims: Our aim is to perform a detailed chemical analysis of the bulge GC NGC 6440 in order to determine if this object has multiple populations (MPs) and investigate its relation with the bulge of the Milky Way and with the other Galactic GCs, especially those associated with the bulge, which are largely poorly studied. Methods: We determined the stellar parameters and the chemical abundances of light elements (Na, Al), iron-peak elements (Fe, Sc, Mn, Co, Ni), α-elements (O, Mg, Si, Ca, Ti) and heavy elements (Ba, Eu) in seven red giant members of NGC 6440 using high-resolution spectroscopy from FLAMES-UVES. Results: We found a mean iron content of [Fe/H] =-0.50 ± 0.03 dex in agreement with other studies. We found no internal iron spread. On the other hand, Na and Al show a significant intrinsic spread, but the cluster has no significant O-Na anticorrelation nor does it exhibit a Mg-Al anticorrelation. The α-elements show good agreement with the bulge field star trend, although they are at the high alpha end and are also higher than those of other GCs of comparable metallicity. The heavy elements are dominated by the r-process, indicating a strong contribution by SNeII. The chemical analysis suggests an origin similar to that of the bulge field stars.

A valiant little terminal: A VLT user's manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinstein, A.

1992-08-01

VLT came to be used at SLAC (Stanford Linear Accelerator Center), because SLAC wanted to assess the Amiga's usefulness as a color graphics terminal and T{sub E}X workstation. Before the project could really begin, the people at SLAC needed a terminal emulator which could successfully talk to the IBM 3081 (now the IBM ES9000-580) and all the VAXes on the site. Moreover, it had to compete in quality with the Ann Arbor Ambassador GXL terminals which were already in use at the laboratory. Unfortunately, at the time there was no commercial program which fit the bill. Luckily, Willy Langeveld hadmore » been independently hacking up a public domain VT100 emulator written by Dave Wecker et al. and the result, VLT, suited SLAC's purpose. Over the years, as the program was debugged and rewritten, the original code disappeared, so that now, in the present version of VLT, none of the original VT100 code remains.« less

A valiant little terminal: A VLT user`s manual. Revision 4

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weinstein, A.

1992-08-01

VLT came to be used at SLAC (Stanford Linear Accelerator Center), because SLAC wanted to assess the Amiga`s usefulness as a color graphics terminal and T{sub E}X workstation. Before the project could really begin, the people at SLAC needed a terminal emulator which could successfully talk to the IBM 3081 (now the IBM ES9000-580) and all the VAXes on the site. Moreover, it had to compete in quality with the Ann Arbor Ambassador GXL terminals which were already in use at the laboratory. Unfortunately, at the time there was no commercial program which fit the bill. Luckily, Willy Langeveld hadmore » been independently hacking up a public domain VT100 emulator written by Dave Wecker et al. and the result, VLT, suited SLAC`s purpose. Over the years, as the program was debugged and rewritten, the original code disappeared, so that now, in the present version of VLT, none of the original VT100 code remains.« less

Of Rings and Volcanoes

NASA Astrophysics Data System (ADS)

2002-01-01

Fine Images of Saturn and Io with VLT NAOS-CONICA Summary With its new NAOS-CONICA Adaptive Optics facility, the ESO Very Large Telescope (VLT) at the Paranal Observatory has recently obtained impressive views of the giant planet Saturn and Io, the volcanic moon of Jupiter. They show the two objects with great clarity, unprecedented for a ground-based telescope. The photos were made during the ongoing commissioning of this major VLT instrument, while it is being optimized and prepared for regular observations that will start later this year. PR Photo 04a/02 : VLT NAOS-CONICA photo of the giant planet Saturn (composite H+K band image). PR Photo 04b/02 : The Jovian moon Io (Br-gamma image). PR Photo 04c/02 : The Jovian moon Io (composite Br-gamma + L' image). Commissioning of NAOS-CONICA progresses "First light" for the new NAOS-CONICA Adaptive Optics facility on the 8.2-m VLT YEPUN telescope at the Paranal Observatory was achieved in November 2001, cf. ESO PR 25/01. A second phase of the "commissioning" of the new facility began on January 22, 2002, now involving specialized observing modes and with the aim of trimming it to maximum performance before it is made available to the astronomers later this year. During this demanding and delicate work, more test images have been made of various astronomical objects [1]. Some of these show selected solar system bodies, for which the excellent image sharpness achievable with this new instrument is of special significance. In fact, the VLT photos of the giant planet Saturn and Io, the innermost of Jupiter's four large moons, are among the sharpest ever obtained from the ground . They even compare well with some photos obtained from space, as can be seen via the related weblinks indicated below. The raw NAOS-CONICA data from which these images shown in this Photo Release were produced are now available via the public VLT Science Archive Facility [2]. The NAOS adaptive optics corrector was built, under an ESO contract, by the Office National d'Etudes et de Recherches Aérospatiales (ONERA) , Laboratoire d'Astrophysique de Grenoble (LAOG) and the DESPA and DASGAL laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA infra-red camera was built, under an ESO contract, by the Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut für Extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO. Saturn - Lord of the rings ESO PR Photo 04a/02 ESO PR Photo 04a/02 [Preview - JPEG: 460 x 400 pix - 54k] [Normal - JPEG: 1034 x 800 pix - 200k] Caption : PR Photo 04a/02 shows the giant planet Saturn, as observed with the VLT NAOS-CONICA Adaptive Optics instrument on December 8, 2001; the distance was 1209 million km. It is a composite of exposures in two near-infrared wavebands (H and K) and displays well the intricate, banded structure of the planetary atmosphere and the rings. Note also the dark spot at the south pole at the bottom of the image. One of the moons, Tethys, is visible as a small point of light below the planet. It was used to guide the telescope and to perform the adaptive optics "refocussing" for this observation. More details in the text. Technical information about this photo is available below. This NAOS/CONICA image of Saturn ( PR Photo 04a/02 ), the second-largest planet in the solar system, was obtained at a time when Saturn was close to summer solstice in the southern hemisphere. At this moment, the tilt of the rings was about as large as it can be, allowing the best possible view of the planet's South Pole. That area was on Saturn's night side in 1982 and could therefore not be photographed during the Voyager encounter. The dark spot close to the South Pole is a remarkable structure that measures approximately 300 km across. It was only recently observed in visible light from the ground with a telescope at the Pic du Midi Observatory in the Pyrenees (France) - this is the first infrared image to show it. The bright spot close to the equator is the remnant of a giant storm in Saturn's extended atmosphere that has lasted more than 5 years. The present photo provides what is possibly the sharpest view of the ring system ever achieved from a ground-based observatory . Many structures are visible, the most obvious being the main ring sections, the inner C-region (here comparatively dark), the middle B-region (here relatively bright) and the outer A-region, and also the obvious dark "divisions", including the well-known, broad Cassini division between the A- and B-regions, as well as the Encke division close to the external edge of the A-region and the Colombo division in the C-region. Moreover, many narrow rings can be seen at this high image resolution , in particular within the C-region - they may be compared with those seen by the Voyager spacecraft during the flybys, cf. the weblinks below. This image demonstrates the capability of NAOS-CONICA to observe also extended objects with excellent spatial resolution. It is a composite of four short-exposure images taken through the near-infrared H (wavelength 1.6 µm) and K (2.2 µm) filters. This observation was particularly difficult because of the motion of Saturn during the exposure. To provide the best possible images, the Adaptive Optics system of NAOS was pointed towards the Saturnian moon Tethys , while the image of Saturn was kept at a fixed position on the CONICA detector by means of "differential tracking" (compensating for the different motions in the sky of Saturn and Tethys). This is also why the (faint) image of Tethys - visible south of Saturn (i.e., below the planet in PR Photo 04a/02 ) - appears slightly trailed. Io - volcanoes and sulphur ESO PR Photo 04b/02 ESO PR Photo 04b/02 [Preview - JPEG: 400 x 478 pix - 39k] [Normal - JPEG: 800 x 955 pix - 112k] ESO PR Photo 04c/02 ESO PR Photo 04c/02 [Preview - JPEG: 400 x 469 pix - 58k] [Normal - JPEG: 800 x 937 pix - 368k] Caption : PR Photo 04b/02 shows Io , the volcanic moon of Jupiter, as imaged with the VLT NAOS-CONICA Adaptive Optics instrument on December 5, 2001, through a near-infrared, narrow optical filter (Brackett-gamma at wavelength 2.166 µm). Despite the small angular diameter of Io , about 1.2 arcsec, many features are visible at this excellent optical resolution. PR Photo 04c/02 is a composite of the same exposure with another obtained at a longer wavelength (L'-filter at 3.8 µm), with a latitude-longitude grid superposed and some of the main surface features identified. Technical information about these photos is available below. Io has a diameter of 3660 km and orbits Jupiter at a mean distance of 422,000 km - one revolution takes 42.5 hours. Like the Earth's moon, it always turns the same side towards the planet. As shown by the Voyager spacecraft in 1979, its surface is covered by active volcanoes and lava fields - it is in fact the most volcanic place known in the solar system. Due to this activity, Io's surface is continuously reshaped. The features now seen are all correspondingly young, with a mean age of the order of 1 million years only. The variations in appearance and colour are due to different volcanic deposits of sulphur compounds. The cause of all this activity is Jupiter's strong gravitational pull that leads to enormous stresses inside Io and related heating of the entire moon. PR Photo 04b/02 is a near-infrared NAOS-CONICA image of Io , obtained on December 5, 2001, through a narrow optical filter at wavelength 2.166 µm. The excellent image resolution makes it possible to identify many features on the surface. Some of these are volcanoes, others correspond to lava fields between these. PR Photo 04c/02 is a composite of that image and another obtained at longer wavelength (3.8 µm). A latitute-longitude grid has been superposed, with the most prominent features identified by name, including some of the large volcanoes and sulphurus plains on this very active moon. Io has been observed with the NASA Galileo spacecraft since 1996 at higher resolution in the visible and infrared, especially during close encounters with the satellite (a link to Galileo maps of Io is available below). However, this NAOS image fills a gap in the surface coverage of the infrared images from Galileo. The capability of NAOS/CONICA to map Io in the infrared at the present high image resolution will allow astronomers to continue the survey of the volcanic activity and to monitor regularly the related surface processes . Related sites The following links point to a number of prominent photos of these two objects that were obtained elsewhere. Saturn Voyager images : http://vraptor.jpl.nasa.gov/voyager/vgrsat_img.html HST images : http://hubble.stsci.edu/news_.and._views/pr.cgi.2001+15 Pic du Midi images : http://www.bdl.fr/s2p/saturne.html IfA-CFHT : http://www.ifa.hawaii.edu/ao/images/solarsys/new/new.html Io NASA/Galileo site : http://www.jpl.nasa.gov/galileo/moons/io.html Volcanoes on Io : http://volcano.und.nodak.edu/vwdocs/planet_volcano/Io/Overview.html HST image of Io : http://hubble.stsci.edu/news_.and._views/pr.cgi.1997+21 Keck I image of Io : http://www.astro.caltech.edu/mirror/keck/realpublic/inst/ao/Io/IoSnapshot.jpg Galileo and Voyager maps of Io : http://www.lowell.edu/users/ijw/maps/ (also with names of surface features) Notes [1]: The following astronomers and engineers from ESO and the partner institutes have participated in the current commissioning observations of Saturn and Io with NAOS-CONICA: Wolfgang Brandner, Jean-Gabriel Cuby, Pierre Drossart, Thierry Fusco, Eric Gendron, Markus Hartung, Norbert Hubin, François Lacombe, Anne-Marie Lagrange, Rainer Lenzen, David Mouillet, Claire Moutou, Gérard Rousset, Jason Spyromilio and Gérard Zins . [2]: New archive users may register via the ESO/ST-ECF Archive Registration Form. Technical information about the photos PR Photo 04a/02 is based on four exposures, obtained with VLT YEPUN and NAOS-CONICA on December 8, 2001 (UT). Two of these were made with an H-band filter (10 sec exposure each, wavelength 1.6 µm) and two with a K-band filter (12 sec each, 2.2 µm). The satellite Tethys (diameter 1070 km, orbiting Saturn at a distance of approx. 295,000 km) served as reference source for the Adaptive Optics corrections and the telescope was offset guided to compensate for the differential motion. The frames were reduced in the normal way with classical flats, dark and bias correction. No convolution was made before the two colours were combined to produce the image shown. At the time of the exposure, Saturn was 8.80 AU from the Earth. With a diameter of approx. 120,000 km, its disk subtended an angle of 20.6 arcsec. The nominal resolution of the NAOS-CONICA image, about 0.07 arcsec, thus corresponds to 410 km at Saturn. PR Photo 04b/02 is a reproduction based on a total exposure of 230 sec with VLT YEPUN and NAOS-CONICA on December 5, 2001, made through a Brackett-gamma filter centred at 2.166 µm. The resulting image resolution is 0.068 arcsec. At the moment of the exposure, the distance from the Earth to Io was about 641 million km (4.29 AU) and the image resolution therefore corresponds to approx. 210 km on the surface of the moon. PR Photo 04c/02 is based on a combination of the Brackett-gamma (here rendered as blue) with an L' frame (total exposure 4.2 sec; 3.800 µm; red), superposed with a coordinate grid and with some of the major surface features identified. The grid was produced with tools available at the website of the Institut de Mecanique Celeste et de Calcul des Ephemerides.

VLT instruments: industrial solutions for non-scientific detector systems

NASA Astrophysics Data System (ADS)

Duhoux, P.; Knudstrup, J.; Lilley, P.; Di Marcantonio, P.; Cirami, R.; Mannetta, M.

2014-07-01

Recent improvements in industrial vision technology and products together with the increasing need for high performance, cost efficient technical detectors for astronomical instrumentation have led ESO with the contribution of INAF to evaluate this trend and elaborate ad-hoc solutions which are interoperable and compatible with the evolution of VLT standards. The ESPRESSO spectrograph shall be the first instrument deploying this technology. ESO's Technical CCD (hereafter TCCD) requirements are extensive and demanding. A lightweight, low maintenance, rugged and high performance TCCD camera product or family of products is required which can operate in the extreme environmental conditions present at ESO's observatories with minimum maintenance and minimal downtime. In addition the camera solution needs to be interchangeable between different technical roles e.g. slit viewing, pupil and field stabilization, with excellent performance characteristics under a wide range of observing conditions together with ease of use for the end user. Interoperability is enhanced by conformance to recognized electrical, mechanical and software standards. Technical requirements and evaluation criteria for the TCCD solution are discussed in more detail. A software architecture has been adopted which facilitates easy integration with TCCD's from different vendors. The communication with the devices is implemented by means of dedicated adapters allowing usage of the same core framework (business logic). The preference has been given to cameras with an Ethernet interface, using standard TCP/IP based communication. While the preferred protocol is the industrial standard GigE Vision, not all vendors supply cameras with this interface, hence proprietary socket-based protocols are also acceptable with the provision of a validated Linux compliant API. A fundamental requirement of the TCCD software is that it shall allow for a seamless integration with the existing VLT software framework. ESPRESSO is a fiber-fed, cross-dispersed echelle spectrograph that will be located in the Combined-Coudé Laboratory of the VLT in the Paranal Observatory in Chile. It will be able to operate either using the light of any of the UT's or using the incoherently combined light of up to four UT's. The stabilization of the incoming beam is achieved by dedicated piezo systems controlled via active loops closed on 4 + 4 dedicated TCCD's for the stabilization of the pupil image and of the field with a frequency goal of 3 Hz on a 2nd to 3rd magnitude star. An additional 9th TCCD system shall be used as an exposure-meter. In this paper we will present the technical CCD solution for future VLT instruments.

ESO PR Highlights in 2000

NASA Astrophysics Data System (ADS)

2001-01-01

At the beginning of the new millennium, ESO and its staff are facing the future with confidence. The four 8.2-m Unit Telescopes of the Very Large Telescope (VLT) are in great shape and the VLT Interferometer (VLTI) will soon have "first fringes". The intercontinental ALMA project is progressing well and concepts for extremely large optical/infrared telescopes are being studied. They can also look back at a fruitful and rewarding past year. Perhaps the most important, single development has been the rapid transition of the Very Large Telescope (VLT). From being a "high-tech project under construction" it has now become a highly proficient, world-class astronomical observatory. This trend is clearly reflected in ESO's Press Releases , as more and more front-line scientific results emerge from rich data obtained at this very efficient facility. There were also exciting news from several of the instruments at La Silla. At the same time, the ESO community may soon grow, as steps towards membership are being taken by various European countries. Throughout 2000, a total of 54 PR communications were made, with a large number of Press Photos and Video Clips, cf. the 2000 PR Index. Some of the ESO PR highlights may be accessed directly via the clickable image on the present page. ESO PR Photo 01/01 is also available in a larger (non-clickable) version [ JPEG: 566 x 566 pix - 112k]. It may be reproduced, if credit is given to the European Southern Observatory.

Ultra-fast Movies of the Sky

NASA Astrophysics Data System (ADS)

2005-06-01

British scientists have opened a new window on the Universe with the recent commissioning of the Visitor Instrument ULTRACAM on the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Chile. ULTRACAM is an ultra fast camera capable of capturing some of the most rapid astronomical events. It can take up to 500 pictures a second in three different colours simultaneously. It has been designed and built by scientists from the Universities of Sheffield and Warwick (United Kingdom), in collaboration with the UK Astronomy Technology Centre in Edinburgh. ULTRACAM employs the latest in charged coupled device (CCD) detector technology in order to take, store and analyse data at the required sensitivities and speeds. CCD detectors can be found in digital cameras and camcorders, but the devices used in ULTRACAM are special because they are larger, faster and most importantly, much more sensitive to light than the detectors used in today's consumer electronics products. In May 2002, the instrument saw "first light" on the 4.2-m William Herschel Telescope (WHT) on La Palma. Since then the instrument has been awarded a total of 75 nights of time on the WHT to study any object in the Universe which eclipses, transits, occults, flickers, flares, pulsates, oscillates, outbursts or explodes. These observations have produced a bonanza of new and exciting results, leading to already 11 scientific publications published or in press. To study the very faintest stars at the very highest speeds, however, it is necessary to use the largest telescopes. Thus, work began 2 years ago preparing ULTRACAM for use on the VLT. "Astronomers using the VLT now have an instrument specifically designed for the study of high-speed phenomena", said Vik Dhillon, from the University of Sheffield (UK) and the ULTRACAM project scientist. "Using ULTRACAM in conjunction with the current generation of large telescopes makes it now possible to study high-speed celestial phenomena such as eclipses, oscillations and occultations in stars which are millions of times too faint to see with the unaided eye." Observing Black Holes ESO PR Photo 19b/05 ESO PR Photo 19b/05 Light curves of the black-hole GU Muscae. [Preview - JPEG: 400 x 427 pix - 151k] [Normal - JPEG: 800 x 854 pix - 354k] [Full Res - JPEG: 2221 x 2371 pix - 1.3M] Caption: ESO PR Photo 19b/05 presents an early scientific highlight from the first few nights of the ULTRACAM observing campaign on the Very Large Telescope: light curves in the i'- (red) and g'-band (green) of the quiescent black-hole X-ray transient GU Muscae. This object consists of a black hole in a 10-hour orbit with a normal solar-like star. The black hole is surrounded by an accretion disc of material transferred from the solar-like star. As this material accretes onto the black hole, energy is released, and this is evident from the large-amplitude flares visible in the light curves. What was not expected, however, is the series of sharp spikes that can be seen, and which are separated by approximately 7 minutes. Such a stable signal must be tied to a relatively stable structure in the accretion disc. The instrument saw first light on the VLT on May 4, 2005, and was then used for 17 consecutive nights on the telescope to study extrasolar planets, black-hole binary systems, pulsars, white dwarfs, asteroseismology, cataclysmic variables, brown dwarfs, gamma-ray bursts, active-galactic nuclei and Kuiper-belt objects. One of the faint objects studied with ULTRACAM on the VLT is GU Muscae. This object consists of a black hole in a 10-hour orbit with a normal, solar-like star. The black hole is surrounded by a disc of material transferred from the normal star. As this material falls onto the black hole, energy is released, producing large-amplitude flares visible in the light curve. This object has magnitude 21.4, that is, it is one million times fainter than what can be seen with the unaided eye. Yet, to study it in detail and detect the shortest possible pulses, it is necessary to use exposure times as short as 5 seconds. This is possible with the large aperture and great efficiency of the VLT. These unique observations have revealed a series of sharp spikes, separated by approximately 7 minutes. Such a stable signal must be tied to a relatively stable structure in the disc of matter surrounding the black hole. The astronomers are now in the process of analysing these results in great details in order to understand the origin of this structure. Another series of observations were dedicated to the study of extrasolar planets, more particularly those that transit in front of their host star. ULTRACAM observations have allowed the astronomers to obtain simultaneous light curves, in several colour-bands, of four known transiting exoplanets discovered by the OGLE survey, and this with a precision of a tenth of a percent and with a 4 second time resolution. This is a factor ten better than previous measurements and will provide very accurate masses and radii for these so-called "hot-Jupiters". Because ULTRACAM makes observations in three different wavebands, such observations will also allow astronomers to establish whether the radius of the exoplanet is different at different wavelengths. This could provide crucial information on the possible exoplanets' atmosphere. The camera is the first instrument to make use of the Visitor Focus on Melipal (UT3), and the first UK-built instrument to be mounted at the VLT. The Visitor Focus allows innovative technologies and instrumentation to be added to the telescope for short periods of time, permitting studies to take place that are not available with the current suite of instruments. "These few nights with ULTRACAM on the VLT have demonstrated the unique discoveries that can be made by combining an innovative technology with one of the best astronomical facilities in the world," said Tom Marsh of the University of Warwick and member of the team. "We hope that ULTRACAM will now become a regular visitor at the VLT, giving European astronomers access to a unique new tool with which to study the Universe." More information The ULTRACAM team is composed of Vik Dhillon, Stuart Littlefair, and Paul Kerry (Sheffield, UK), Tom Marsh (Warwick, UK), Andy Vick and Dave Atkinson (UKATC, Edinburgh, UK). For the installation on the VLT, they received support from Kieran O'Brien and Pascal Robert (ESO, Chile). The ULTRACAM project page can be found at http://www.shef.ac.uk/~phys/people/vdhillon/ultracam.

The circumstellar environments of B[e] Supergiants

NASA Astrophysics Data System (ADS)

Maravelias, G.; Kraus, M.; Cidale, L.; Arias, M. L.; Aret, A.; Borges Fernandes, M.

2017-11-01

The evolution of massive stars encompasses short-lived transition phases in which mass-loss is more enhanced and usually eruptive. A complex environment, combining atomic, molecular and dust regions, is formed around these stars. In particular, the circumstellar environment of B[e] Supergiants is not well understood. To address that, we have initiated a campaign to investigate their environments for a sample of Galactic and Magellanic Cloud sources. Using high-resolution optical and near-infrared spectra (MPG-ESO/FEROS, GEMINI/Phoenix and VLT/CRIRES, respectively), we examine a set of emission features ([OI], [CaII], CO bandheads) to trace the physical conditions and kinematics in their formation regions. We find that the B[e] Supergiants are surrounded by a series of rings of different temperatures and densities, a probable result of previous mass-loss events. In many cases the CO forms very close to the star, while we notice also an alternate mixing of densities and temperatures (which give rise to the different emission features) along the equatorial plane.

ESPRESSO optical bench: from mind to reality

NASA Astrophysics Data System (ADS)

Tenegi, F.; Santana, S.; Gómez, J.; Rodilla, E.; Hughes, I.; Mégevand, D.; Rebolo, R.; Riva, M.; Luis-Simoes, R.

2016-07-01

ESPRESSO [1] is a high-resolution spectrograph under development for the VLT telescope. In general, the Optical Bench (OB) structure can be considered as a 3D one, conformed by welding thin plates of Structural Steel (St-52) with a nickelplated surface treatment, combined for getting maximum stiffness and minimum weight, that will be finally re-machined to get stringent geometrical and dimensional tolerances at I/Fs positions. TIG conventional welding procedure has been selected to minimize the cost and facilitate the own welding process. This solution follows the inheritance from HARPS [2] due to its success to achieve the required performance for the bench. This paper contains an overview of the whole process of designing and manufacturing the Optical Bench of ESPRESSO, from the very first beginning with the specifications to the current status of the bench with its integration on the Spectrograph (including the Finite Element Models and the delivery of the final structure by the supplier) and lessons learned.

VizieR Online Data Catalog: VANDELS High-Redshift Galaxy Evolution (McLure+, 2017)

NASA Astrophysics Data System (ADS)

McLure, R.; Pentericci, L.; Vandels Team

2017-11-01

This is the first data release (DR1) of the VANDELS survey, an ESO public spectroscopy survey targeting the high-redshift Universe. The VANDELS survey uses the VIMOS spectrograph on ESO's VLT to obtain ultra-deep, medium resolution, optical spectra of galaxies within the UKIDSS Ultra Deep Survey (UDS) and Chandra Deep Field South (CDFS) survey fields (0.2 sq. degree total area). Using robust photometric redshift pre-selection, VANDELS is targeting ~2100 galaxies in the redshift interval 1.0=3. In addition, VANDELS is targeting a substantial number of passive galaxies in the redshift interval 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Myron A.; Shiao, Bernard; Bianchi, Luciana, E-mail: myronmeister@gmail.com, E-mail: shiao@stsci.edu, E-mail: bianchi@pha.jhu.edu

We report on intriguing photometric properties of Galactic stars observed in the Galaxy Evolution Explorer (GALEX) satellite's far-UV (FUV) and near-UV (NUV) bandpasses, as well as from the ground-based Sloan Digital Sky Survey (SDSS) and the Kepler Input Catalog. The first property is that the (FUV – NUV) color distribution of stars in the Kepler field consists of two well-separated peaks. A second and more perplexing property is that for stars with spectral types G or later the mean (FUV – NUV) color becomes much bluer, contrary to expectation. Investigating this tendency further, we found in two samples of mid-Fmore » through K type stars that 17%-22% of them exhibit FUV excesses relative to their NUV fluxes and spectral types. A correction for FUV incompleteness of the FUV magnitude-limited star sample brings this ratio to 14%-18%. Nearly the same fractions are also discovered among members of the Kepler Eclipsing Binary Catalog and in the published list of Kepler Objects of Interest. These UV-excess ('UVe') colors are confirmed by the negative UV continuum slopes in GALEX spectra of members of the population. The SDSS spectra of some UVe stars exhibit metallic line weakening, especially in the blue. This suggests an enhanced contribution of UV flux relative to photospheric flux of a solar-type single star. We consider the possibility that the UV excesses originate from various types of hot stars, including white dwarf DA and sdB stars, binaries, and strong chromosphere stars that are young or in active binaries. The space density of compact stars is too low to explain the observed frequency of the UVe stars. Our model atmosphere-derived simulations of colors for binaries with main-sequence pairs with a hot secondary demonstrate that the color loci conflict with the observed sequence. As a preferred alternative we are left with the active chromospheres explanation, whether in active close binaries or young single stars, despite the expected paucity of young, chromospherically active stars in the field. We also address a third perplexing color property, namely, the presence of a prominent island of 'UV red' stars surrounded by 'UV blue' stars in the diagnostic (NUV–g), (g – i) color diagram. We find that the subpopulation composing this island is mainly horizontal branch stars. These objects do not exhibit UV excesses and therefore have UV colors typical for their spectral types. This subpopulation appears 'red' in the UV only because the stars' colors are not pulled to the blue by the inclusion of UVe stars.« less

Large Interstellar Polarisation Survey. II. UV/optical study of cloud-to-cloud variations of dust in the diffuse ISM

NASA Astrophysics Data System (ADS)

Siebenmorgen, R.; Voshchinnikov, N. V.; Bagnulo, S.; Cox, N. L. J.; Cami, J.; Peest, C.

2018-03-01

It is well known that the dust properties of the diffuse interstellar medium exhibit variations towards different sight-lines on a large scale. We have investigated the variability of the dust characteristics on a small scale, and from cloud-to-cloud. We use low-resolution spectro-polarimetric data obtained in the context of the Large Interstellar Polarisation Survey (LIPS) towards 59 sight-lines in the Southern Hemisphere, and we fit these data using a dust model composed of silicate and carbon particles with sizes from the molecular to the sub-micrometre domain. Large (≥6 nm) silicates of prolate shape account for the observed polarisation. For 32 sight-lines we complement our data set with UVES archive high-resolution spectra, which enable us to establish the presence of single-cloud or multiple-clouds towards individual sight-lines. We find that the majority of these 35 sight-lines intersect two or more clouds, while eight of them are dominated by a single absorbing cloud. We confirm several correlations between extinction and parameters of the Serkowski law with dust parameters, but we also find previously undetected correlations between these parameters that are valid only in single-cloud sight-lines. We find that interstellar polarisation from multiple-clouds is smaller than from single-cloud sight-lines, showing that the presence of a second or more clouds depolarises the incoming radiation. We find large variations of the dust characteristics from cloud-to-cloud. However, when we average a sufficiently large number of clouds in single-cloud or multiple-cloud sight-lines, we always retrieve similar mean dust parameters. The typical dust abundances of the single-cloud cases are [C]/[H] = 92 ppm and [Si]/[H] = 20 ppm.

VLTI First Fringes with Two Auxiliary Telescopes at Paranal

NASA Astrophysics Data System (ADS)

2005-03-01

World's Largest Interferometer with Moving Optical Telescopes on Track Summary The Very Large Telescope Interferometer (VLTI) at Paranal Observatory has just seen another extension of its already impressive capabilities by combining interferometrically the light from two relocatable 1.8-m Auxiliary Telescopes. Following the installation of the first Auxiliary Telescope (AT) in January 2004 (see ESO PR 01/04), the second AT arrived at the VLT platform by the end of 2004. Shortly thereafter, during the night of February 2 to 3, 2005, the two high-tech telescopes teamed up and quickly succeeded in performing interferometric observations. This achievement heralds an era of new scientific discoveries. Both Auxiliary Telescopes will be offered from October 1, 2005 to the community of astronomers for routine observations, together with the MIDI instrument. By the end of 2006, Paranal will be home to four operational ATs that may be placed at 30 different positions and thus be combined in a very large number of ways ("baselines"). This will enable the VLTI to operate with enormous flexibility and, in particular, to obtain extremely detailed (sharp) images of celestial objects - ultimately with a resolution that corresponds to detecting an astronaut on the Moon. PR Photo 07a/05: Paranal Observing Platform with AT1 and AT2 PR Photo 07b/05: AT1 and AT2 with Open Domes PR Photo 07c/05: Evening at Paranal with AT1 and AT2 PR Photo 07d/05: AT1 and AT2 under the Southern Sky PR Photo 07e/05: First Fringes with AT1 and AT2 PR Video Clip 01/05: Two ATs at Paranal (Extract from ESO Newsreel 15) A Most Advanced Device ESO PR Video 01/05 ESO PR Video 01/05 Two Auxiliary Telescopes at Paranal [QuickTime: 160 x 120 pix - 37Mb - 4:30 min] [QuickTime: 320 x 240 pix - 64Mb - 4:30 min] ESO PR Photo 07a/05 ESO PR Photo 07a/05 [Preview - JPEG: 493 x400 pix - 44k] [Normal - JPEG: 985 x 800 pix - 727k] [HiRes - JPEG: 5000 x 4060 pix - 13.8M] Captions: ESO PR Video Clip 01/05 is an extract from ESO Video Newsreel 15, released on March 14, 2005. It provides an introduction to the VLT Interferometer (VLTI) and the two Auxiliary Telescopes (ATs) now installed at Paranal. ESO PR Photo 07a/05 shows the impressive ensemble at the summit of Paranal. From left to right, the enclosure of VLT Antu, Kueyen and Melipal, AT1, the VLT Survey Telescope (VST) in the background, AT2 and VLT Yepun. Located at the summit of the 2,600-m high Cerro Paranal in the Atacama Desert (Chile), ESO's Very Large Telescope (VLT) is at the forefront of astronomical technology and is one of the premier facilities in the world for optical and near-infrared observations. The VLT is composed of four 8.2-m Unit Telescope (Antu, Kueyen, Melipal and Yepun). They have been progressively put into service together with a vast suite of the most advanced astronomical instruments and are operated every night in the year. Contrary to other large astronomical telescopes, the VLT was designed from the beginning with the use of interferometry as a major goal. The href="/instruments/vlti">VLT Interferometer (VLTI) combines starlight captured by two 8.2- VLT Unit Telescopes, dramatically increasing the spatial resolution and showing fine details of a large variety of celestial objects. The VLTI is arguably the world's most advanced optical device of this type. It has already demonstrated its powerful capabilities by addressing several key scientific issues, such as determining the size and the shape of a variety of stars (ESO PR 22/02, PR 14/03 and PR 31/03), measuring distances to stars (ESO PR 25/04), probing the innermost regions of the proto-planetary discs around young stars (ESO PR 27/04) or making the first detection by infrared interferometry of an extragalactic object (ESO PR 17/03). "Little Brothers" ESO PR Photo 07b/05 ESO PR Photo 07b/05 [Preview - JPEG: 597 x 400 pix - 47k] [Normal - JPEG: 1193 x 800 pix - 330k] [HiRes - JPEG: 5000 x 3354 pix - 10.0M] ESO PR Photo 07c/05 ESO PR Photo 07c/05 [Preview - JPEG: 537 x 400 pix - 31k] [Normal - JPEG: 1074 x 800 pix - 555k] [HiRes - JPEG: 3000 x 2235 pix - 6.0M] ESO PR Photo 07d/05 ESO PR Photo 07d/05 [Preview - JPEG: 400 x 550 pix - 60k] [Normal - JPEG: 800 x 1099 pix - 946k] [HiRes - JPEG: 2414 x 3316 pix - 11.0M] Captions: ESO PR Photo 07b/05 shows VLTI Auxiliary Telescopes 1 and 2 (AT1 and AT2) in the early evening light, with the spherical domes opened and ready for observations. In ESO PR Photo 07c/05, the same scene is repeated later in the evening, with three of the large telescope enclosures in the background. This photo and ESO PR Photo 07c/05 which is a time-exposure with AT1 and AT2 under the beautiful night sky with the southern Milky Way band were obtained by ESO staff member Frédéric Gomté. However, most of the time the large telescopes are used for other research purposes. They are therefore only available for interferometric observations during a limited number of nights every year. Thus, in order to exploit the VLTI each night and to achieve the full potential of this unique setup, some other (smaller), dedicated telescopes were included into the overall VLT concept. These telescopes, known as the VLTI Auxiliary Telescopes (ATs), are mounted on tracks and can be placed at precisely defined "parking" observing positions on the observatory platform. From these positions, their light beams are fed into the same common focal point via a complex system of reflecting mirrors mounted in an underground system of tunnels. The Auxiliary Telescopes are real technological jewels. They are placed in ultra-compact enclosures, complete with all necessary electronics, an air conditioning system and cooling liquid for thermal control, compressed air for enclosure seals, a hydraulic plant for opening the dome shells, etc. Each AT is also fitted with a transporter that lifts the telescope and relocates it from one station to another. It moves around with its own housing on the top of Paranal, almost like a snail. Moreover, these moving ultra-high precision telescopes, each weighing 33 tonnes, fulfill very stringent mechanical stability requirements: "The telescopes are unique in the world", says Bertrand Koehler, the VLTI AT Project Manager. "After being relocated to a new position, the telescope is repositioned to a precision better than one tenth of a millimetre - that is, the size of a human hair! The image of the star is stabilized to better than thirty milli-arcsec - this is how we would see an object of the same size as one of the VLT enclosures on the Moon. Finally, the path followed by the light inside the telescope after bouncing on ten mirrors is stable to better than a few nanometres, which is the size of about one hundred atoms." A World Premiere ESO PR Photo 07e/05 ESO PR Photo 07e/05 "First Fringes" with two ATs [Preview - JPEG: 400 x 559 pix - 61k] [Normal - JPEG: 800 x 1134 pix - 357k] Caption: ESO PR Photo 07e/05 The "First Fringes" obtained with the first two VLTI Auxiliary Telescopes, as seen on the computer screen during the observation. The fringe pattern arises when the light beams from the two 1.8-m telescopes are brought together inside the VINCI instrument. The pattern itself contains information about the angular extension of the observed object, here the 6th-magnitude star HD62082. The fringes are acquired by moving a mirror back and forth around the position of equal path length for the two telescopes. One such scan can be seen in the third row window. This pattern results from the raw interferometric signals (the last two rows) after calibration and filtering using the photometric signals (the 4th and 5th row). The first two rows show the spectrum of the fringe pattern signal. More details about the interpretation of this pattern is given in Appendix A of PR 06/01. The possibility to move the ATs around and thus to perform observations with a large number of different telescope configurations ensures a great degree of flexibility, unique for an optical interferometric installation of this size and crucial for its exceptional performance. The ATs may be placed at 30 different positions and thus be combined in a very large number of ways. If the 8.2-m VLT Unit Telescopes are also taken into account, no less than 254 independent pairings of two telescopes ("baselines"), different in length and/or orientation, are available. Moreover, while the largest possible distance between two 8.2-m telescopes (ANTU and YEPUN) is about 130 metres, the maximal distance between two ATs may reach 200 metres. As the achievable image sharpness increases with telescope separation, interferometric observations with the ATs positioned at the extreme positions will therefore yield sharper images than is possible by combining light from the large telescopes alone. All of this will enable the VLTI to obtain exceedingly detailed (sharp) and very complete images of celestial objects - ultimately with a resolution that corresponds to detecting an astronaut on the Moon. Auxiliary Telescope no. 1 (AT1) was installed on the observatory's platform in January 2004. Now, one year later, the second of the four to be delivered, has been integrated into the VLTI. The installation period lasted two months and ended around midnight during the night of February 2-3, 2005. With extensive experience from the installation of AT1, the team of engineers and astronomers were able to combine the light from the two Auxiliary Telescopes in a very short time. In fact, following the necessary preparations, it took them only five minutes to adjust this extremely complex optical system and successfully capture the "First Fringes" with the VINCI test instrument! The star which was observed is named HD62082 and is just at the limit of what can be observed with the unaided eye (its visual magnitude is 6.2). The fringes were as clear as ever, and the VLTI control system kept them stable for more than one hour. Four nights later this exercise was repeated successfully with the mid-infrared science instrument MIDI. Fringes on the star Alphard (Alpha Hydrae) were acquired on February 7 at 4:05 local time. For Roberto Gilmozzi, Director of ESO's La Silla Paranal Observatory, "this is a very important new milestone. The introduction of the Auxiliary Telescopes in the development of the VLT Interferometer will bring interferometry out of the specialist experiment and into the domain of common user instrumentation for every astronomer in Europe. Without doubt, it will enormously increase the potentiality of the VLTI." With two more telescopes to be delivered within a year to the Paranal Observatory, ESO cements its position as world-leader in ground-based optical astronomy, providing Europe's scientists with the tools they need to stay at the forefront in this exciting science. The VLT Interferometer will, for example, allow astronomers to study details on the surface of stars or to probe proto-planetary discs and other objects for which ultra-high precision imaging is required. It is premature to speculate on what the Very Large Telescope Interferometer will soon discover, but it is easy to imagine that there may be quite some surprises in store for all of us.

How Old is the Universe?

NASA Astrophysics Data System (ADS)

2001-02-01

First Reading of a Basic Cosmic Chronometer with UVES and the VLT Summary Most astronomers would agree that the age of the Universe - the time elapsed since the "Big Bang" - is one of the " holy grails of cosmology ". Despite great efforts during recent years, the various estimates of this basic number have resulted in rather diverse values. When derived from current cosmological models, it depends on a number of theoretical assumptions that are not very well constrained by the incomplete available observational data. At present, a value in the range of 10-16 billion years [1] is considered most likely. But now, an international team of astronomers [2] has used the powerful ESO Very Large Telescope (VLT) and its very efficient spectrograph UVES to perform a unique measurement that paves the way for a new and more accurate determination of the age of the Universe. They measured for the first time the amount of the radioactive isotope Uranium-238 in a star that was born when the Milky Way, the galaxy in which we live, was still forming. It is the first measurement ever of uranium outside the Solar System . This method works in a way similar to the well-known Carbon-14 dating in archaeology, but over much longer times. Ever since the star was born, the Uranium "clock" has ticked away over the eons, unaffected by the turbulent history of the Milky Way. It now reads 12.5 billion years . Since the star obviously cannot be older than the Universe, it means that the Universe must be older than that . Although the stated uncertainty is still about 25% or about ±3 billion years, this is only to a minor extent due to the astronomical observation. The main problem is the current absence of accurate knowledge of some of the basic atomic and nuclear properties of the elements involved. However, further laboratory work will greatly improve this situation and a more accurate value for the age of the star and implicitly, for the Universe, should therefore be forthcoming before long . This important result is reported in the international research journal Nature in the issue of February 8, 2001. PR Photo 05a/01 : The 12.5-billion-year old star CS 31082-001. PR Photo 05b/01 : The telltale spectral line in CS 31082-001 - the first detection of uranium outside the Solar System . Heavy elements in stars While hydrogen, helium and lithium were produced during the Big Bang, all heavier elements result from nuclear reactions in the interiors of stars. When stars die, heavy-element enriched matter is dispersed into surrounding space and will later be incorporated in the next generations of stars. In fact, the gold in the ring on your finger was produced in an exploding star and deposited in the interstellar cloud from which the Sun and its planets were later formed. Thus, the older a star is, the lower is generally its content of heavy elements like iron and other metals. Measurements have shown that old stars that are members of large agglomerations known as globular clusters are normally quite "metal-poor"- their metal-content ranges down to about 1/200 of that of the Sun, in which these metals constitute only 2% of the total mass, the rest being still in the form of hydrogen and helium. Very old stars in the Milky Way galaxy After decades of mostly fruitless efforts, a large spectral survey by American astronomer Timothy C. Beers and his collaborators has recently uncovered hundreds of stars with much lower metal content than even the globular clusters, in some cases only 1/10,000 of the solar value. It is evident that these extremely metal-poor stars must have formed during the very infancy of the Milky Way, an important, but still poorly understood phase in the life of our galaxy. These particular stars exhibit a great variety of element abundances that may ultimately throw more light on the processes at work during this early period. As a step in this direction, an international team of astronomers [2] decided to study these stars in much more detail. They were awarded observing time for a Large Programme in 2000-2001 with the powerful combination of the ESO VLT and its very efficient high-dispersion spectrograph UVES. The first observations have been carried out and, not unexpectedly, have already proven to be a true gold mine of new information. Cosmochronology with radioactive isotopes It is possible to make a fundamental determination of the age of a star that is quite independent of stellar evolution models, provided it contains a suitable long-lived radioactive isotope [3]. The use of a "radioactive chronometer" depends on the measurement of the abundance of the radioactive isotope, as compared to a stable one. This technique is analogous to the Carbon-14 dating method that has been so successful in archaeology over time spans of up to a few tens of thousands of years. In astronomy, however, this technique must obviously be applied to vastly longer time scales. For the method to work well, the right choice of radioactive isotope is very critical. Contrary to stable elements that formed at the same time, the abundance of a radioactive (unstable) isotope decreases all the time. The faster the decay, the less there will be left of the radioactive isotope after a certain time, the greater will be the abundance difference when compared to a stable isotope, and the more accurate is the resulting age. Yet, for the clock to remain useful, the radioactive element must not decay too fast - there must still be enough left of it to allow an accurate measurement, even after several billion years. Thorium and Uranium clocks This leaves only two possible isotopes for astronomical measurements, thorium ( 232 Th or Thorium-232, with a half-life of 14.05 billion years [4]) and uranium ( 238 U or Uranium-238, half-life 4.47 billion years). Several age determinations have been made by means of the Thorium-232 isotope. Its strongest spectral line is measurable with current telescopes in a handful of comparatively bright stars, including the Sun. However, the decay is really too slow to provide sufficiently accurate time measurements. It takes around 47 billion years for this isotope to decay by a factor of 10, and with a typical measuring uncertainty of 25%, the resulting age uncertainty is about 4-5 billion years, or approx. one third of the age of the Universe. This slow-moving clock runs forever, but is hard to read accurately! The faster decay of Uranium-238 would make it a much more precise cosmic clock. However, because uranium is the rarest of all normal elements, its spectral lines in stars are always very weak; if visible at all, they normally drown entirely in a vast ocean of stronger spectral lines from more abundant elements. Nevertheless, this is exactly where the low abundance of heavier elements in very old stars comes to the rescue. In the stars that were studied by the present team at the VLT, with typically 1000 times less of the common elements than in the Sun, the predominance of the maze of atomic and molecular lines in the spectrum is greatly reduced. The lines of rare elements like uranium therefore stand a real chance of being measurable. This is particularly so, if for some reason uranium atoms were preferentially retained in the debris of those early supernova explosions that also created the iron-group elements we see in the stars today. The uranium line in CS 31082-001 ESO PR Photo 05a/01 ESO PR Photo 05a/01 [Preview - JPEG: 337 x 400 pix - 32k] [Normal - JPEG: 674 x 800 pix - 120k] Caption : PR Photo 05a/01 displays the Milky Way star field around CS 31082-001 , the 12th-magnitude star at the centre. The "cross" is caused by reflections in the telescope optics, a typical effect for relatively bright stars. Technical information about this photo is available below. ESO PR Photo 05b/01 ESO PR Photo 05b/01 [Preview - JPEG: 501 x 400 pix - 42k] [Normal - JPEG: 1001 x 800 pix - 128k] [Full-Res - JPEG: 1502 x 1200 pix - 200k] Caption : PR Photo 05b/01 The observed spectrum (dots) of the old star CS 31082-001 in the region of the uranium (U II) line at 385.96 nm. The origin of some of the other spectral lines in the region is also indicated (e.g. iron, neodymium). The synthetic spectrum (thin line) was computed for the adopted abundances of the stable elements and for four different values of the abundance (by number) of uranium atoms in the atmosphere of the star. The uppermost line (corresponding to no uranium at all) clearly does not fit the observed spectrum at all. The best fit is provided by the middle (red) line, representing a uranium abundance of approximately 6% of the solar value - see also the text. Technical information about this diagramme is available below. The excitement of the astronomers was great when they inspected the first spectrum of the 12th-magnitude programme star CS 31082-001 ! It showed what is probably the richest spectrum of rare, heavy elements ever seen. In particular, the faint lines of these elements were unusually free of interference from the lines of the iron-group elements which are indeed only 1/800 as abundant in this star as in the Sun, and by molecular lines (of CH and CN), often quite numerous even in such low-metallicity stars. While only one or at most two thorium lines have ever been measured in any other stars, no less than 14 thorium lines are seen in the spectrum of CS 31082-001 . Indeed, there is such a wealth of lines of other rare and precious metals that this spectrum is a real astronomers' treasure box. And best of all, the long sought-after line of singly ionized uranium is clearly detected at its rest wavelength of 389.59 nm in the near-ultraviolet region of the spectrum, cf. PR Photo 05b/01 ! Not surprisingly, the uranium line is still quite weak. After all, uranium is the rarest of elements to begin with and it has further decayed by a factor of eight since this star was born. Moreover, even in this low metal-abundance star, the near-UV spectrum remains rather rich in other lines. The accurate measurement of this faint spectral line therefore places extreme demands on the acuity (resolving power) and efficiency of the spectrograph and the light-gathering power of the telescope. The VLT and UVES have been built as the world-leading combination of these observational assets, and the spectra obtained of this comparatively faint star (magnitude 12, i.e. 500 times fainter than what can be seen with the unaided eye) are absolutely superb - indeed of a quality which until recently was reserved for naked-eye stars only. Despite its faintness, the uranium line can therefore be measured with very good accuracy. The age of CS 31082-001 A detailed analysis, using model atmospheres and synthetic spectrum calculations, shows that all the heaviest stable elements follow closely the abundance pattern seen in the Sun, but at a level of about 12% of the corresponding solar abundances [5]. The measurements also show that the thorium and uranium abundances are somewhat lower than this - of the order of 9% and 6% of the solar values, respectively. Since these two elements were formed by the same atomic processes as their stable neighbours in the periodic table, this means that radioactive decay has progressed further in CS 31082-001 than in the Sun. Different models of the element production in supernova explosions predict somewhat different production ratios between the stable and radioactive isotopes, leading to age estimates for this star in the range 11-16 billion years. The most likely age of CS 31082-001 is 12.5 billion years . The Universe is older than the star, hence it must be older than 12.5 billion years. Improved age determination soon possible Given the faster decay rate of Uranium-238, the measuring uncertainty for the stellar uranium line corresponds to an age uncertainty of only ±1.5 Gyr. This can be further reduced with even better spectra of CS 31082-001 and/or with the discovery and observation of other similar stars. However, for the immediate future, the accuracy of this age determination does not really depend on the VLT spectrum. For the time being, the real problems are the present uncertainties in the available laboratory data for uranium by means of which the measured line strengths are converted into element abundances. In addition, the nuclear-physics calculations of the initial isotope production ratios introduce errors that are larger than those of the spectral observation. Thus, improved measurements of those physical data are necessary in order to read more accurately the cosmic clock in CS 31082-001 from the existing observational data. The relevant laboratory measurements are now underway at the CEA, Saclay, France, and the University of Lund, Sweden. In the meantime, the team is trying to find other stars like CS 31082-001 . There may not be many, but if the uranium line can be seen and measured in more spectra, it will also become possible to judge whether those very old stars, as surmised, are all of about the same age, i.e. that of our Milky Way galaxy. More information The research described in this Press Release is reported in a research article ("Measurement of stellar age from uranium decay"), that appears in the international research journal Nature on Thursday, February 8, 2001. Notes [1]: 1 billion = 1,000 million. [2]: The team members are: Roger Cayrel (P.I.), Francois Spite and Monique Spite (all Observatoire de Paris, France), Vanessa Hill and Francesca Primas (ESO), Johannes Andersen and Birgitta Nordström (Copenhagen and Lund Observatories, Denmark and Sweden), Timothy C. Beers (Michigan State Univ., USA), Piercarlo Bonifacio and Paolo Molaro (Trieste, Italy), Bertrand Plez (Montpellier, France), and Beatriz Barbuy (Univ. of Sao Paulo, Brazil). [3]: Isotopes of a natural element contain different numbers of neutrons in the nuclei, in addition to a certain number of protons that characterize that particular element. Some isotopes are "radioactive", i.e. with time they are transformed into other elements or isotopes. Other isotopes are stable over exceedingly long periods of time. Uranium-238 contains 92 protons and 146 neutrons. [4]: The "half-life" of an isotope indicates the time after which half the atoms have decayed. After another time interval of this length has passed, only 25% of the original isotope is left, etc. [5]: As the iron abundance in CS 31082-001 is only 0.12% (1/800) of that in the Sun, this means that, relative to iron and similar, lighter elements, the heaviest elements in that star are approximately 100 times "overabundant". Their spectral lines, again in relative terms, are correspondingly stronger - this is of crucial importance for the present, difficult measurements. Technical information about the photos PR Photo 05a/01 is reproduced from the STScI Digitized Sky Survey (© 1993, 1994, AURA, Inc. - original plate material by Royal Observatory Edinburgh and the Anglo-Australian Observatory - All Rights Reserved) and based on blue-sensitive photographic data obtained using the UK Schmidt Telescope at Siding Spring (Australia). The comparatively empty sky field is located at high southern (-76°) galactic latitude and measures 7 x 7 arcmin 2 and. PR Photo 05b/01 is reproduced from a spectrum of CS 31082-001 , obtained in October 2000 with the UVES high-dispersion spectrograph at the VLT 8.2-m KUEYEN telescope at Paranal. The exposure lasted 4 hours, at a spectral resolution of approx. 75,000 and with a S/N-ratio of about 300. The lines are identified and three synthetic spectra, with different U-abundances, are drawn to illustrate the fit.

First Giant Mirror for the ESO VLT Ready at REOSC

NASA Astrophysics Data System (ADS)

1995-11-01

The REOSC Contract In 1989, the European Southern Observatory (ESO), the European Organisation for Astronomy, awarded to REOSC, a subsidiary of the SFIM Group and located in Saint Pierre du Perray (France), a comprehensive contract for the polishing of four 8.2-metre diameter mirrors for the unit telescopes of the ESO Very Large Telescope (VLT) project. These mirrors are the largest ever manufactured and polished. This contract comprises not only the polishing and high-precision optical testing of each giant mirror, but also the safe condition of transportation of the blanks which were manufactured by Schott Glaswerke in Mainz (Germany). In order to fulfill the contract, REOSC conceived, built and equipped a novel, high-tech workshop which would allow to polish and test the mirrors, each of which has a surface area of more than 50 square metres. First 8.2-Metre Mirror is Ready and within Specifications The REOSC polishing facility for giant mirrors was built in Saint Pierre du Perray, just south of Paris. It is equipped with two machines: one for grinding and the other for polishing the mirrors, and both with 150-actuator systems that support the thin and flexible mirrors. All equipment is computer controlled. State-of-the-art interferometers probe the accuracy of the mirror surface as the polishing proceeds; they are installed at the top level of the facility in a 30-metre high tower, at the centre of the mirror's radius of curvature. The success of the work at REOSC is now evident by the fact that careful measurements of the first mirror earlier this month have shown that the final optical surface is correct to within 0.00005 millimetres. For illustration, this corresponds to an accuracy of only 1 millimetre deviation over a surface with a diameter of 165 kilometres (equivalent to the entire Paris area)! ESO Receives the First VLT Mirror After having been carefully placed in a special transport box designed by REOSC, the first mirror blank, weighing 23.5 tons and with a replacement value of about 20 million DEM, was transported from Mainz to Saint Pierre du Perray in July 1993. The shaping and polishing phases lasted two years and were completed in October 1995. After one month's hard work, dedicated to optical and mechanical verifications by ESO and REOSC, the mirror's various characteristics have now been found to be in accordance with the contract specifications. Following the technical acceptance, the first mirror was re-installed in its transport container on November 13, 1995. It will thereafter be formally handed over to ESO during a ceremony at REOSC on Tuesday, November 21, 1995. The mirror will be stored at the REOSC facility until its future departure to ESO's VLT Observatory on Cerro Paranal, a 2650 m high summit in the Andean Cordillera in northern Chile. Here it will be installed in the first VLT unit telescope, soon after the assembly of the mechanical parts has been completed. Future Plans at REOSC The polishing of the second VLT mirror, as well as the grinding of the third mirror which was transported from Mainz to Saint Pierre du Perray at the beginning of October 1995, have already started. The transport of the fourth blank will take place in March 1996. With the construction, in a subsequent phase, of a workshop of more than 6000 square metres and mostly dedicated to space and astronomy, the SFIM group will have invested more than 50 million French Francs at the Saint Pierre du Perray site alone. The group is also involved in the contract related to the actuator support system; this is a clear indication of its determination to maintain its position within this scientific-technological market. In addition to the ESO VLT mirrors, REOSC will also polish the two 8.2-metre diameter mirrors of the Gemini programme of the Association of Universities for Research in Astronomy (AURA) in the United States. This important work was entrusted REOSC, following an international call for tenders, in which also US firms participated. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

First Images from VLT Science Verification Programme

NASA Astrophysics Data System (ADS)

1998-09-01

Two Weeks of Intensive Observations Successfully Concluded After a period of technical commissioning tests, the first 8.2-m telescope of the ESO VLT (UT1) has successfully performed an extensive series of "real science" observations , yielding nearly 100 hours of precious data. They concern all possible types of astronomical objects, from distant galaxies and quasars to pulsars, star clusters and solar system objects. This intensive Science Verification (SV) Programme took place as planned from August 17 to September 1, 1998, and was conducted by the ESO SV Team at the VLT Observatory on Paranal (Chile) and at the ESO Headquarters in Garching (Germany). The new giant telescope lived fully up to the high expectations and worked with spectacular efficiency and performance through the entire period. All data will be released by September 30 via the VLT archive and the web (with some access restrictions - see below). The Science Verification period Just before the beginning of the SV period, the 8.2-m primary mirror in its cell was temporarily removed in order to install the "M3 tower" with the tertiary mirror [1]. The reassembly began on August 15 and included re-installation at the Cassegrain focus of the VLT Test Camera that was also used for the "First Light" images in May 1998. After careful optical alignment and various system tests, the UT1 was handed over to the SV Team on August 17 at midnight local time. The first SV observations began immediately thereafter and the SV Team was active 24 hours a day throughout the two-week period. Video-conferences between Garching and Paranal took place every day at about noon Garching time (6 o'clock in the morning on Paranal). Then, while the Paranal observers were sleeping, data from the previous night were inspected and reduced in Garching, with feedback on what was best to do during the following night being emailed to Paranal several hours in advance of the beginning of the observations. The campaign ended in the morning of September 1 when the telescope was returned to the Commissioning Team that has since continued its work. The FORS instrument is now being installed and the first images from this facility are expected shortly. Observational circumstances During the two-week SV period, a total of 154 hours were available for astronomical observations. Of these, 95 hours (62%) were used to collect scientific data, including calibrations, e.g. flat-fielding and photometric standard star observations. 15 hours (10%) were spent to solve minor technical problems, while another 44 hours (29%) were lost due to adverse meteorological conditions (clouds or wind exceeding 15 m/sec). The amount of telescope technical downtime is very small at this moment of the UT1 commissioning. This fact provides an impressive indication of high technical reliability that has been achieved and which will be further consolidated during the next months. The meteorological conditions that were encountered at Paranal during this period were unfortunately below average, when compared to data from the same calendar period in earlier years. There was an excess of bad seeing and fewer good seeing periods than normal; see, however, ESO PR Photo 35c/98 with 0.26 arcsec image quality. Nevertheless, the measured image quality on the acquired frames was often better than the seeing measured outside the enclosure by the Paranal seeing monitor. Part of this very positive effect is due to "active field stabilization" , now performed during all observations by rapid motion (10 - 70 times per second) of the 1.1-m secondary mirror of beryllium (M2) and compensating for the "twinkling" of stars. Science Verification data soon to be released A great amount of valuable data was collected during the SV programme. The available programme time was distributed as follows: Hubble Deep Field - South [HDF-S; NICMOS and STIS Fields] (37.1 hrs); Lensed QSOs (3.2 hrs); High-z Clusters (6.2 hrs); Host Galaxies of Gamma-Ray Bursters (2.1 hrs); Edge-on Galaxies (7.4 hrs); Globular cluster cores (6.7 hrs); QSO Hosts (4.4 hrs); TNOs (3.4 hrs); Pulsars (1.3 hrs); Calibrations (22.7 hrs). All of the SV data are now in the process of being prepared for public release by September 30, 1998 to the ESO and Chilean astronomical communities. It will be possible to retrieve the data from the VLT archive, and a set of CDs will be distributed to all astronomical research institutes within the ESO member states and Chile. Moreover, data obtained on the HDF-S will become publicly available worldwide, and retrievable from the VLT archive. Updated information on this data release can be found on the ESO web site at http://www.eso.org/vltsv/. It is expected that the first scientific results based on the SV data will become available in the course of October and November 1998. First images from the Science Verification programme This Press Release is accompanied by three photos that reproduce some of the images obtained during the SV period. ESO PR Photo 35a/98 ESO PR Photo 35a/98 [Preview - JPEG: 671 x 800 pix - 752k] [High-Res - JPEG: 2518 x 3000 pix - 5.8Mb] This colour composite was constructed from the U+B, R and I Test Camera Images of the Hubble Deep Field South (HDF-S) NICMOS field. These images are displayed as blue, green and red, respectively. The first photo is a colour composite of the HDF-S NICMOS sky field that combines exposures obtained in different wavebands: ultraviolet (U) + blue (B), red (R) and near-infrared (I). For all of them, the image quality is better than 0.9 arcsec. Most of the objects seen in the field are distant galaxies. The image is reproduced in such a way that it shows the faintest features scaled, while rendering the image of the star below the large spiral galaxy approximately white. The spiral galaxy is displayed in such a way that the internal structure is visible. A provisional analysis has shown that limiting magnitudes that were predicted for the HDF-S observations (27.0 - 28.5, depending on the band), were in fact reached. Technical information : Photo 35a/98 is based on 16 U-frames (~370 nm; total exposure time 17800 seconds; mean seeing 0.71 arcsec) and 15 B-frames (~430 nm; 10200 seconds; 0.71 arcsec) were added and combined with 8 R frames (~600 nm; 7200 seconds; 0.49 arcsec) and 12 I-frames (~800 nm; 10150 seconds; 0.59 arcsec) to make this colour composite. Individual frames were flat-fielded and cleaned for cosmics before combination. The field shown measures 1.0 x 1.0 arcmin. North is up; East is to the left. ESO PR Photo 35b/98 ESO PR Photo 35b/98 [Preview - JPEG: 679 x 800 pix - 760k] [High-Res - JPEG: 2518 x 3000 pix - 5.7Mb] The colour composite of the HDF-S NICMOS field constructed by combining VLT Test Camera images in U+B and R bands with a HST NICMOS near-IR H-band exposure. These images are displayed as blue, green and red, respectively. The NICMOS image was smoothed to match the angular resolution of the R-band VLT image. The boundary of the NICMOS image is also shown. The next photo is similar to the first one, but uses a near-IR frame obtained with the Hubble Space Telescope NICMOS instrument instead of the VLT I-frame. The HST image has nearly the same total exposure time as the VLT images. Their combination is meaningful since the VLT and NICMOS images reach similar depths and show more or less the same faint objects. This is the result of several effects compensating each other: while more distant galaxies are redder and therefore better visible at the infrared waveband of the NICMOS image and this image has a better angular resolution than those from the VLT, the collecting area of the UT1 mirror is over 11 times larger than that of the HST. It is interesting to note that all objects in the NICMOS image are also visible in the VLT images, with the exception of the very red object just left of the face-on spiral. The bright red object near the bottom has not before been detected in optical images (to the limit of R ~ 26 mag), but is clearly present in all the VLT Test Camera coadded images, with the exception of the U-band image. Both of these very red objects are possibly extremely distant, elliptical galaxies [2]. The additional information that can be obtained from the combination of the VLT and the infrared NICMOS images has an immediate bearing on the future work with the VLT. When the infrared, multi-mode ISAAC instrument enters into operation in early 1999, it will be able to obtain spectra of such objects and, in general, to deliver very deep infrared images. Thus, the combination of visual (from FORS) and infrared (from ISAAC) images and spectra promises to become an extremely powerful tool that will allow the detection of very red and therefore exceedingly distant galaxies. Moreover, it is obvious that this sky field is not very crowded - much longer exposure times will thus be possible without encountering serious problems of overlapping objects at the "confusion limit". Technical information : Photo 35b/98 is based on 16 U-frames (~370 nm; total exposure time 17800 seconds; mean seeing 0.71 arcsec) and 15 B-frames (~430 nm; 10200 seconds; 0.71 arcsec) were added and combined with 8 R frames (~600 nm; 7200 seconds; 0.49 arcsec) as well as a HST/NICMOS H-band frame(a H-band HST/NICMOS image from the ST-ECF public archive) (~1600 nm; 7040 seconds; 0.2 arcsec) to make this colour composite. Individual frames were flat-fielded and cleaned for cosmics before combination. The field shown measures 1.0 x 1.0 arcmin. North is up; East is to the left. ESO PR Photo 35c/98 ESO PR Photo 35c/98 [Preview - JPEG: 654 x 800 pix - 280k] [High-Res - JPEG: 2489 x 3000 pix - 2.6Mb] Coaddition of two R-band images of edge-on galaxy ESO342-G017 , obtained with 0.26 arcsec image quality. The galaxy ESO342-G017 was observed on August 19, 1998 during a spell of excellent observing conditions. Two exposures, each lasting 120 seconds, were taken through a red filtre to produce this photo. The quality of the original images is excellent, with seeing (FWHM) of only 0.26 arcsec measured on the stars in the frame. ESO342-G017 is an Sc-type spiral galaxy seen edge-on, and the Test Camera was rotated so that the disk of the galaxy appears horizontal in the figure. Thanks to the image quality, the photo shows much detail in the rather flat disk, including a very thin, obscuring dust band and some brighter knots, most probably star-forming regions. This galaxy is located well outside the Milky Way band in the southern constellation of Sagittarius. Its distance is about 400 million light-years (recession velocity about 7,700 km/sec). A number of more distant galaxies are seen in the background on this short exposure. Technical information : Photo 35c/98 is a reproduced from a composite of two 120-second exposures in the red R-band (~600 nm) of the edge-on galaxy ESO342-G017, both with 0.26 arcsec image quality. The frames were flat-fielded and cleaned for cosmics before combination. The field shown measures 1.5 x 1.5 arcmin. North is inclined 38 o clockwise from the top, East is to the left. Notes: [1] The flat and elliptically shaped, tertiary mirror M3 is mounted on top of the M3 Tower that is fixed in the center of the M1 Cell. The tower can rotate along its axis and deflects the light coming from the M2 mirror to the astronomical instruments on either Nasmyth platform. A mechanism at the top of the M3 Tower is used to move the M3 mirror away from the optical path when the instrument at the Cassegrain focus is used, e.g. the Test Camera during the SV observations. [2] This effect is due to the fact that the more distant a galaxy is, the larger is the velocity with which it recedes from us (Hubble's law). The larger the velocity, the further its emitted light will be shifted redwards in the observed spectrum (the Doppler effect) and the redder its image will appear to us. By comparing the brightness of a distant galaxy in different wavebands (measuring its colour), it is therefore in practice possible to estimate its redshift and thus its distance (the " photometric redshift" method). How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

The Gaia-ESO Survey: Sodium and aluminium abundances in giants and dwarfs. Implications for stellar and Galactic chemical evolution

NASA Astrophysics Data System (ADS)

Smiljanic, R.; Romano, D.; Bragaglia, A.; Donati, P.; Magrini, L.; Friel, E.; Jacobson, H.; Randich, S.; Ventura, P.; Lind, K.; Bergemann, M.; Nordlander, T.; Morel, T.; Pancino, E.; Tautvaišienė, G.; Adibekyan, V.; Tosi, M.; Vallenari, A.; Gilmore, G.; Bensby, T.; François, P.; Koposov, S.; Lanzafame, A. C.; Recio-Blanco, A.; Bayo, A.; Carraro, G.; Casey, A. R.; Costado, M. T.; Franciosini, E.; Heiter, U.; Hill, V.; Hourihane, A.; Jofré, P.; Lardo, C.; de Laverny, P.; Lewis, J.; Monaco, L.; Morbidelli, L.; Sacco, G. G.; Sbordone, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

2016-05-01

Context. Stellar evolution models predict that internal mixing should cause some sodium overabundance at the surface of red giants more massive than ~1.5-2.0 M⊙. The surface aluminium abundance should not be affected. Nevertheless, observational results disagree about the presence and/or the degree of Na and Al overabundances. In addition, Galactic chemical evolution models adopting different stellar yields lead to very different predictions for the behavior of [Na/Fe] and [Al/Fe] versus [Fe/H]. Overall, the observed trends of these abundances with metallicity are not well reproduced. Aims: We readdress both issues, using new Na and Al abundances determined within the Gaia-ESO Survey. Our aim is to obtain better observational constraints on the behavior of these elements using two samples: I) more than 600 dwarfs of the solar neighborhood and of open clusters and II) low- and intermediate-mass clump giants in six open clusters. Methods: Abundances were determined using high-resolution UVES spectra. The individual Na abundances were corrected for nonlocal thermodynamic equilibrium effects. For the Al abundances, the order of magnitude of the corrections was estimated for a few representative cases. For giants, the abundance trends with stellar mass are compared to stellar evolution models. For dwarfs, the abundance trends with metallicity and age are compared to detailed chemical evolution models. Results: Abundances of Na in stars with mass below ~2.0 M⊙, and of Al in stars below ~3.0 M⊙, seem to be unaffected by internal mixing processes. For more massive stars, the Na overabundance increases with stellar mass. This trend agrees well with predictions of stellar evolutionary models. For Al, our only cluster with giants more massive than 3.0 M⊙, NGC 6705, is Al enriched. However, this might be related to the environment where the cluster was formed. Chemical evolution models that well fit the observed [Na/Fe] vs. [Fe/H] trend in solar neighborhood dwarfs cannot simultaneously explain the run of [Al/Fe] with [Fe/H], and vice versa. The comparison with stellar ages is hampered by severe uncertainties. Indeed, reliable age estimates are available for only a half of the stars of the sample. We conclude that Al is underproduced by the models, except for stellar ages younger than about 7 Gyr. In addition, some significant source of late Na production seems to be missing in the models. Either current Na and Al yields are affected by large uncertainties, and/or some important Galactic source(s) of these elements has as yet not been taken into account. Based on observations made with the ESO/VLT, at Paranal Observatory, under program 188.B-3002 (The Gaia-ESO Public Spectroscopic Survey), and on data obtained from the ESO Archive originally observed under programs 60.A-9143, 076.B-0263 and 082.D-0726.Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/589/A115

Biggest Star in Our Galaxy Sits within a Rugby-Ball Shaped Cocoon

NASA Astrophysics Data System (ADS)

2003-11-01

VLT Interferometer Gives Insight Into the Shape of Eta Carinae Summary Ever since 1841, when the until then inconspicuous southern star Eta Carinae underwent a spectacular outburst, astronomers have wondered what exactly is going on in this unstable giant star. However, due to its considerable distance - 7,500 light-years - details of the star itself were beyond observation. This star is known to be surrounded by the Homunculus Nebula , two mushroom-shaped clouds ejected by the star, each of which is hundreds of times larger than our solar system. Now, for the first time, infrared interferometry with the VINCI instrument on ESO's Very Large Telescope Interferometer (VLTI) enabled an international team of astronomers [1] to zoom-in on the inner part of its stellar wind. For Roy van Boekel , leader of the team, these results indicate that " the wind of Eta Carinae turns out to be extremely elongated and the star itself is highly unstable because of its fast rotation." PR Photo 32a/03 : The Immediate Surroundings of Eta Carinae (NAOS-CONICA/YEPUN). PR Photo 32b/03 : The Highly Unstable Star Eta Carinae (Artist's Impression) A monster in the southern sky ESO PR Photo 32a/03 ESO PR Photo 32a/03 [Preview - JPEG: 549 x 400 pix - 60k [Normal - JPEG: 1098 x 800 pix - 566k] Caption : The image to the left in PR Photo 32a/03 shows the mushroom-shaped clouds, known as the Homunculus Nebula , that surround the massive star Eta Carinae (Credit: NASA/ESA HST). To the right is an image obtained with the VLT NACO adaptive-optics camera that reveals the structure of the star's immediate surroundings. The central region displays a complex morphology of luminous objects. Eta Carinae , the most luminous star known in our Galaxy, is by all standards a real monster: it is 100 times more massive than our Sun and 5 million times as luminous. This star has now entered the final stage of its life and is highly unstable. It undergoes giant outbursts from time to time; one of the most recent happened in 1841 and created the beautiful bipolar nebula known as the Homunculus Nebula (see ESO PR Photo 32a/03 ). At that time, and despite the comparatively large distance - 7,500 light-years - Eta Carinae briefly became the second brightest star in the night sky, surpassed only by Sirius. Eta Carinae is so big that, if placed in our solar system, it would extend beyond the orbit of Jupiter. This large size, though, is somewhat arbitrary. Its outer layers are continually being blown into space by radiation pressure - the impact of photons on atoms of gas. Many stars, including our Sun, lose mass because of such "stellar winds", but in the case of Eta Carinae , the resulting mass loss is enormous (about 500 Earth-masses a year) and it is difficult to define the border between the outer layers of the star and the surrounding stellar wind region. Now, VINCI and NAOS-CONICA, two infrared-sensitive instuments on ESO's Very Large Telescope (VLT) at the Paranal Observatory (Chile), have probed the shape of the stellar wind region for the first time. Looking down into the stellar wind as far as possible, the astronomers could infer some of the structure of this enigmatic object. The astronomer team [1] first used the NAOS-CONICA adaptive optics camera [2], attached to the 8.2-m VLT YEPUN telescope, to image the hazy surroundings of Eta Carinae , with a spatial resolution comparable to the size of the solar system, cf. PR Photo 32a/03 . This image shows that the central region of the Homunculus nebula is dominated by an object that is seen as a point-like light source with many luminous "blobs" in the immediate vicinity. Towards the limit In order to obtain an even sharper view, the astronomers then turned to interferometry. This technique combines two or more telescopes to achieve an angular resolution [3] equal to that of a telescope as large as the separation of the individual telescopes (cf. ESO PR 06/01 and ESO PR 23/01 ). For the study of the rather bright star Eta Carinae the full power of the 8.2-m VLT telescopes is not required. The astronomers thus used VINCI, the VLT INterferometer Commissioning Instrument [4], together with two 35-cm siderostat test telescopes that served to obtain "First Light" with the VLT Interferometer in March 2001 (see ESO PR 06/01 ). The siderostats were placed at selected positions on the VLT Observing Platform at the top of Paranal to provide different configurations and a maximum baseline of 62 meters. During several nights, the two small telescopes were pointed towards Eta Carinae and the two light beams were directed towards a common focus in the VINCI test instrument in the centrally located VLT Interferometric Laboratory. It was then possible to measure the angular size of the star (as seen in the sky) in different directions. Pushing the spatial resolution of this configuration to the limit, the astronomers succeeded in resolving the shape of the outer layer of Eta Carinae . They were able to provide spatial information on a scale of 0.005 arcsec, that is about 11 AU (1650 million km) at the distance of Eta Carinae , corresponding to the full size of the orbit of Jupiter. Scaled down to terrestial dimensions, this achievement compares to making the distinction between an egg and a billiard ball at a distance of 2,000 kilometers. A most unusual shape ESO PR Photo 32b/03 ESO PR Photo 32b/03 [Preview - JPEG: 400 x 500 pix - 28k [Normal - JPEG: 800 x 999 pix - 302k] Caption : PR Photo 32b/03 is an artist's impression of the unstable star Eta Carinae , based on the new knowledge gained from measurements with the VLT Interferometer (VLTI). The inner elongated shape is the central star, as it would be visible in the absence of the stellar wind. The larger rugby-ball shape indicates the region where the strong stellar wind becomes opaque to VINCI. The longer axis of the system is found to coincide with the direction of the bipolar outflow, both on large and small scales. The VLTI observations brought the astronomers a surprise. They indicate that the wind around Eta Carinae is amazingly elongated: one axis is one-and-a-half times longer than the other! Moreover, the longer axis is found to be aligned with the direction in which the much larger mushroom-shaped clouds (seen on less sharp images) were ejected. Spanning a scale from 10 to 20-30,000 AU, the star itself and the Homunculus Nebula are thus closely aligned in space . VINCI was able to detect the boundary where the stellar wind from Eta Carinae becomes so dense that it is no longer transparent. Apparently, this stellar wind is much stronger in the direction of the long axis than of the short axis. According to mainstream theories, stars lose most mass around their equator. This is because this is where the stellar wind gets "lifting" assistance from the centrifugal force caused by the star's rotation. However, if this were so in the case of Eta Carinae , the axis of rotation (through the star's poles) would then be perpendicular to both mushroom-shaped clouds. But it is virtually impossible that the mushroom clouds are positioned like spokes in a wheel, relative to the rotating star. The matter ejected in 1841 would then have been stretched into a ring or torus. For Roy van Boekel , " the current overall picture only makes sense if the stellar wind of Eta Carinae is elongated in the direction of its poles . This is a surprising reversal of the usual situation, where stars (and planets) are flattened at the poles due to the centrifugal force . The next supernova? Such an exotic shape for Eta Carinae-type stars was predicted by theoreticians. The main assumption is that the star itself, which is located deep inside its stellar wind, is flattened at the poles for the usual reason. However, as the polar areas of this central zone are then closer to the centre where nuclear fusion processes take place, they will be hotter. Consequently, the radiation pressure in the polar directions will be higher and the outer layers above the polar regions of the central zone will get more "puffed up" than the outer layers at the equator. Assuming this model is correct, the rotation of Eta Carinae can be calculated. It turns out that it should spin at over 90 percent of the maximum speed possible (before break-up). Eta Carinae has experienced large outbursts other than the one in 1841, most recently around 1890. Whether another outburst will happen again in the near future is unknown, but it is certain that this unstable giant star will not settle down. At the present, it is losing so much mass so rapidly that nothing will be left of it after less than 100,000 years. More likely, though, Eta Carinae will destroy itself long before that in a supernova blast that could possibly become visible in the daytime sky with the naked eye. This may happen "soon" on the astronomical time-scale, perhaps already within the next 10-20,000 years. More information The research presented in this Press Release was published as a Letter to the Editor in the European astronomy journal Astronomy and Astrophysics ("Direct measurement of the size and shape of the present-day stellar wind of Eta Carinae", by Roy van Boekel et al. , A&A 410, L37-L40). Notes [1]: The team is composed of Roy van Boekel (ESO and the University of Amsterdam, The Netherlands), Pierre Kervella, Francesco Paresce and Markus Schöller (ESO), Wolfgang Brandner , Tom Herbst and Rainer Lenzen (MPI for Astronomy, Heidelberg, Germany), Alex de Koter and Rens Waters (University of Amsterdam, The Netherlands), John Hillier (University of Pittsburgh, USA), and Anne-Marie Lagrange (Observatoire de Grenoble, France). [2]: The Nasmyth Adaptive Optics System (NAOS) has been developed by a French Consortium including the Office National d'Etudes et de Recherches Aérospatiales (ONERA), the Laboratoire d'Astrophysique de Grenoble (LAOG) and Observatoire de Paris (DESPA and DASGAL), in collaboration with ESO. The CONICA Near-Infrared CAmera has been developed by the Max-Planck-Institut für Astronomie (MPIA, Heidelberg) and the Max-Planck-Institut für Extraterrestrische Physik (MPE, Garching), with an extensive ESO collaboration. See ESO PR 25/01. [3]: The achievable angular resolution is inversely proportional to the aperture of a telescope for single telescope observation, and to the length of the "baseline" between two telescopes for an interferometric observation. However, interferometric observations with two telescopes will improve the resolution only in the direction parallel to this baseline, while the resolution in the perpendicular direction will remain that of a single telescope. Nevertheless, the use of other telescope pairs with different baseline orientations "adds" resolution in other directions. [4]: The VINCI instrument was built under ESO contract at the Observatoire de Paris (France) and the camera in this instrument was delivered by the Max-Planck-Institute für Extraterrestrische Physik (Garching, Germany). The IR detector and the IRACE detector electronics were supplied by ESO.

Engineering aspects of the Large Binocular Telescope Observatory adaptive optics systems

NASA Astrophysics Data System (ADS)

Brusa, Guido; Ashby, Dave; Christou, Julian C.; Kern, Jonathan; Lefebvre, Michael; McMahon, Tom J.; Miller, Douglas; Rahmer, Gustavo; Sosa, Richard; Taylor, Gregory; Vogel, Conrad; Zhang, Xianyu

2016-07-01

Vertical profiles of the atmospheric optical turbulence strength and velocity is of critical importance for simulating, designing, and operating the next generation of instruments for the European Extremely Large Telescope. Many of these instruments are already well into the design phase meaning these profies are required immediately to ensure they are optimised for the unique conditions likely to be observed. Stereo-SCIDAR is a generalised SCIDAR instrument which is used to characterise the profile of the atmospheric optical turbulence strength and wind velocity using triangulation between two optical binary stars. Stereo-SCIDAR has demonstrated the capability to resolve turbulent layers with the required vertical resolution to support wide-field ELT instrument designs. These high resolution atmospheric parameters are critical for design studies and statistical evaluation of on-sky performance under real conditions. Here we report on the new Stereo-SCIDAR instrument installed on one of the Auxillary Telescope ports of the Very Large Telescope array at Cerro Paranal. Paranal is located approximately 20 km from Cerro Armazones, the site of the E-ELT. Although the surface layer of the turbulence will be different for the two sites due to local geography, the high-altitude resolution profiles of the free atmosphere from this instrument will be the most accurate available for the E-ELT site. In addition, these unbiased and independent profiles are also used to further characterise the site of the VLT. This enables instrument performance calibration, optimisation and data analysis of, for example, the ESO Adaptive Optics facility and the Next Generation Transit Survey. It will also be used to validate atmospheric models for turbulence forecasting. We show early results from the commissioning and address future implications of the results.

A tip/tilt mirror with large dynamic range for the ESO VLT Four Laser Guide Star Facility

NASA Astrophysics Data System (ADS)

Rijnveld, N.; Henselmans, R.; Nijland, B.

2011-09-01

One of the critical elements in the Four Laser Guide Star Facility (4LGSF) for the ESO Very Large Telescope (VLT) is the Optical Tube Assembly (OTA), consisting of a stable 20x laser beam expander and an active tip/tilt mirror, the Field Selector Mechanism (FSM). This paper describes the design and performance testing of the FSM. The driving requirement for the FSM is its large stroke of +/-6.1 mrad, in combination with less than 1.5 μrad RMS absolute accuracy. The FSM design consists of a Zerodur mirror, bonded to a membrane spring and strut combination to allow only tip and tilt. Two spindle drives actuate the mirror, using a stiffness based transmission to increase resolution. Absolute accuracy is achieved with two differential inductive sensor pairs. A prototype of the FSM is realized to optimize the control configuration and measure its performance. Friction in the spindle drive is overcome by creating a local velocity control loop between the spindle drives and the shaft encoders. Accuracy is achieved by using a cascaded low bandwidth control loop with feedback from the inductive sensors. The pointing jitter and settling time of the FSM are measured with an autocollimator. The system performance meets the strict requirements, and is ready to be implemented in the first OTA.

And Then There Were Three...!

NASA Astrophysics Data System (ADS)

2000-01-01

VLT MELIPAL Achieves Successful "First Light" in Record Time This was a night to remember at the ESO Paranal Observatory! For the first time, three 8.2-m VLT telescopes were observing in parallel, with a combined mirror surface of nearly 160 m 2. In the evening of January 26, the third 8.2-m Unit Telescope, MELIPAL ("The Southern Cross" in the Mapuche language), was pointed to the sky for the first time and successfully achieved "First Light". During this night, a number of astronomical exposures were made that served to evaluate provisionally the performance of the new telescope. The ESO staff expressed great satisfaction with MELIPAL and there were broad smiles all over the mountain. The first images ESO PR Photo 04a/00 ESO PR Photo 04a/00 [Preview - JPEG: 400 x 352 pix - 95k] [Normal - JPEG: 800 x 688 pix - 110k] Caption : ESO PR Photo 04a/00 shows the "very first light" image for MELIPAL . It is that of a relatively bright star, as recorded by the Guide Probe at about 21:50 hrs local time on January 26, 2000. It is a 0.1 sec exposure, obtained after preliminary adjustment of the optics during a few iterations with the computer controlled "active optics" system. The image quality is measured as 0.46 arcsec FWHM (Full-Width at Half Maximum). ESO PR Photo 04b/00 ESO PR Photo 04b/00 [Preview - JPEG: 400 x 429 pix - 39k] [Normal - JPEG: 885 x 949 pix - 766k] Caption : ESO PR Photo 04b/00 shows the central region of the Crab Nebula, the famous supernova remnant in the constellation Taurus (The Bull). It was obtained early in the night of "First Light" with the third 8.2-m VLT Unit Telescope, MELIPAL . It is a composite of several 30-sec exposures with the VLT Test Camera in three broad-band filters, B (here rendered as blue; most synchrotron emission), V (green) and R (red; mostly emission from hydrogen atoms). The Crab Pulsar is visible to the left; it is the lower of the two brightest stars near each other. The image quality is about 0.9 arcsec, and is completely determined by the external seeing caused by the atmospheric turbulence above the telescope at the time of the observation. The coloured, vertical lines to the left are artifacts of a "bad column" of the CCD. The field measures about 1.3 x 1.3 arcmin 2. This image may be compared with that of the same area that was recently obtained with the FORS2 instrument at KUEYEN ( PR Photo 40g/99 ). Following two days of preliminary adjustments after the installation of the secondary mirror, cf. ESO PR Photos 03a-n/00 , MELIPAL was pointed to the sky above Paranal for the first time, soon after sunset in the evening of January 26. The light of a bright star was directed towards the Guide Probe camera, and the VLT Commissioning Team, headed by Dr. Jason Spyromilio , initiated the active optics procedure . This adjusts the 150 computer-controlled supports under the main 8.2-m Zerodur mirror as well as the position of the secondary 1.1-m Beryllium mirror. After just a few iterations, the optical quality of the recorded stellar image was measured as 0.46 arcsec ( PR Photo 04a/00 ), a truly excellent value, especially at this stage! Immediately thereafter, at 22:16 hrs local time (i.e., at 01:16 hrs UT on January 27), the shutter of the VLT Test Camera at the Cassegrain focus was opened. A 1-min exposure was made through a R(ed) optical filter of a distant star cluster in the constellation Eridanus (The River). The light from its faint stars was recorded by the CCD at the focal plane and the resulting frame was read into the computer. Despite the comparatively short exposure time, myriads of stars were seen when this "first frame" was displayed on the computer screen. Moreover, the sizes of these images were found to be virtually identical to the 0.6 arcsec seeing measured simultaneously with a monitor telescope, outside the telescope enclosure. This confirmed that MELIPAL was in very good shape. Nevertheless, these very first images were still slightly elongated and further optical adjustments and tests were therefore made to eliminate this unwanted effect. It is a tribute to the extensive experience and fine skills of the ESO staff that within only 1 hour, a 30 sec exposure of the central region of the Crab Nebula in Taurus with round images was obtained, cf. PR Photo 04b/00 . The ESO Director General, Dr. Catherine Cesarsky , who assumed her function in September 1999, was present in the Control Room during these operations. She expressed great satisfaction with the excellent result and warmly congratulated the ESO staff to this achievement. She was particularly impressed with the apparent ease with which a completely new telescope of this size could be adjusted in such a short time. A part of her statement on this occasion was recorded on ESO PR Video Clip 02/00 that accompanies this Press Release. Three telescopes now in operation at Paranal At 02:30 UT on January 27, 2000, three VLT Unit Telescopes were observing in parallel, with measured seeing values of 0.6 arcsec ( ANTU - "The Sun"), 0.7 arcsec ( KUEYEN -"The Moon") and 0.7 arcsec ( MELIPAL ). MELIPAL has now joined ANTU and KUEYEN that had "First Light" in May 1998 and March 1999, respectively. The fourth VLT Unit Telescope, YEPUN ("Sirius") will become operational later this year. While normal scientific observations continue with ANTU , the UVES and FORS2 astronomical instruments are now being commissioned at KUEYEN , before this telescope will be handed over to the astronomers on April 1, 2000. The telescope commissioning period will now start for MELIPAL , after which its first instrument, VIMOS will be installed later this year. Impressions from the MELIPAL "First Light" event First Light for MELIPAL ESO PR Video Clip 02/00 "First Light for MELIPAL" (3350 frames/2:14 min) [MPEG Video+Audio; 160x120 pix; 3.1Mb] [MPEG Video+Audio; 320x240 pix; 9.4 Mb] [RealMedia; streaming; 34kps] [RealMedia; streaming; 200kps] ESO Video Clip 02/00 shows sequences from the Control Room at the Paranal Observatory, recorded with a fixed TV-camera on January 27 at 03:00 UT, soon after the moment of "First Light" with the third 8.2-m VLT Unit Telescope ( MELIPAL ). The video sequences were transmitted via ESO's dedicated satellite communication link to the Headquarters in Garching for production of the Clip. It begins with a statement by the Manager of the VLT Project, Dr. Massimo Tarenghi , as exposures of the Crab Nebula are obtained with the telescope and the raw frames are successively displayed on the monitor screen. In a following sequence, ESO's Director General, Dr. Catherine Cesarsky , briefly relates the moment of "First Light" for MELIPAL , as she experienced it at the telescope controls. ESO Press Photo 04c/00 ESO Press Photo 04c/00 [Preview; JPEG: 400 x 300; 44k] [Full size; JPEG: 1600 x 1200; 241k] The computer screen with the image of a bright star, as recorded by the Guide Probe in the early evening of January 26; see also PR Photo 04a/00. This image was used for the initial adjustments by means of the active optics system. (Digital Photo). ESO Press Photo 04d/00 ESO Press Photo 04d/00 [Preview; JPEG: 400 x 314; 49k] [Full size; JPEG: 1528 x 1200; 189k] ESO staff at the moment of "First Light" for MELIPAL in the evening of January 26. The photo was made in the wooden hut on the telescope observing floor from where the telescope was controlled during the first hours. (Digital Photo). ESO PR Photos may be reproduced, if credit is given to the European Southern Observatory. The ESO PR Video Clips service to visitors to the ESO website provides "animated" illustrations of the ongoing work and events at the European Southern Observatory. The most recent clip was: ESO PR Video Clip 01/00 with aerial sequences from Paranal (12 January 2000). Information is also available on the web about other ESO videos.

German Foreign Minister Visits Paranal Observatory

NASA Astrophysics Data System (ADS)

2002-03-01

During his current tour of countries in South America, the Honourable Foreign Minister of Germany, Mr. Joschka Fischer, stopped over at the ESO Paranal Observatory Wednesday night (March 6 - 7, 2002). Arriving in Antofagasta, capital of the II Chilean region, the Foreign Minister and his suite was met by local Chilean officials, headed by Mr. Jorge Molina, Intendente of the Region, as well as His Excellency, the German Ambassador to Chile, Mr. Georg CS Dick and others. In the afternoon of March 6, the Foreign Minister, accompanied by a distinguished delegation from the German Federal Parliament as well as by businessmen from Germany, travelled to Paranal, site of the world's largest optical/infrared astronomical facility, the ESO Very Large Telescope (VLT). The delegation was welcomed by the Observatory Director, Dr. Roberto Gilmozzi, the VLT Programme Manager, Professor Massimo Tarenghi, the ESO Representative in Chile, Mr. Daniel Hofstadt and ESO staff members, and also by Mr. Reinhard Junker, Deputy Director General (European Co-operation) at the German Ministry for Education and Research. The visitors were shown the various high-tech installations at this remote desert site, some of which have been constructed by German firms. Moreover, most of the large, front-line VLT astronomical instruments have been built in collaboration between ESO and European research institutes, several of these in Germany. One of the latest arrivals to Paranal, the CONICA camera (cf. ESO PR 25/01 ), was built under an ESO contract by the Max-Planck-Institutes for Astronomy (MPIA, in Heidelberg) and Extraterrestrial Physics (MPE, in Garching). The guests had the opportunity to enjoy the spectacular sunset over the Pacific Ocean from the terrace of the new Residencia building ( Photos 05/02 ). At the beginning of the night, the Minister was invited to the Control Room for the VLT Interferometer (VLTI) from where this unique new facility ( ESO PR 23/01 ) is now being thoroughly tested before it enters into service later this year. In his expression of thanks, Minister Fischer enthusiastically referred to his visit at Paranal. He said he was truly impressed by the technology of the telescopes and considered the VLT project a model of European technological and scientific cooperation. Later in the evening, the Minister was invited to perform an observing sequence at the console of the MELIPAL telescope.

Comet Tempel 1 Went Back to Sleep

NASA Astrophysics Data System (ADS)

2005-07-01

Astronomers Having Used ESO Telescopes Start Analysing Unique Dataset on the Comet Following the Deep Impact Mission Ten days after part of the Deep Impact spacecraft plunged onto Comet Tempel 1 with the aim to create a crater and expose pristine material from beneath the surface, astronomers are back in the ESO Offices in Santiago, after more than a week of observing at the ESO La Silla Paranal Observatory. In this unprecedented observing campaign - among the most ambitious ever conducted by a single observatory - the astronomers have collected a large amount of invaluable data on this comet. The astronomers have now started the lengthy process of data reduction and analysis. Being all together in a single place, and in close contacts with the space mission' scientific team, they will try to assemble a clear picture of the comet and of the impact. The ESO observations were part of a worldwide campaign to observe this unique experiment. During the campaign, ESO was connected by phone, email, and videoconference with colleagues in all major observatories worldwide, and data were freely exchanged between the different groups. This unique collaborative spirit provides astronomers with data taken almost around the clock during several days and this, with the largest variety of instruments, making the Deep Impact observing campaign one of the most successful of its kind, and thereby, ensuring the greatest scientific outcome. From the current analysis, it appears most likely that the impactor did not create a large new zone of activity and may have failed to liberate a large quantity of pristine material from beneath the surface. ESO PR Photo 22/05 ESO PR Photo 22/05 Evolution of Comet Tempel 1 (FORS2/VLT) [Preview - JPEG: 400 x 701 pix - 128k] [Normal - JPEG: 800 x 1401 pix - 357k] ESO PR Photo 22/05 Animated Gif Caption: ESO PR Photo 22/05 shows the evolution of Comet Tempel 1 as observed with the FORS2 instrument on Antu (VLT). The images obtained at the VLT show that after the impact, the morphology of Comet Tempel 1 had changed, with the appearance of a new plume-like structure, produced by matter being ejected with a speed of about 700 to 1000 km/h (see ESO PR Photo 23/05). This structure, however, diffused away in the following days, being more and more diluted and less visible, the comet taking again the appearance it had before the impact. Further images obtained with, among others, the adaptive optics NACO instrument on the Very Large Telescope, showed the same jets that were visible prior to impact, demonstrating that the comet activity survived widely unaffected by the spacecraft crash. The study of the gas in Comet Tempel 1 (see "Looking for Molecules"), made with UVES on Kueyen (UT2 of the VLT), reveals a small flux increase the first night following the impact. At that time, more than 17 hours after the impact, the ejected matter was fading away but still measurable thanks to the large light collecting power of the VLT. The data accumulated during 10 nights around the impact have provided the astronomers with the best ever time series of optical spectra of a Jupiter Family comet, with a total of more than 40 hours of exposure time. This unique data set has already allowed the astronomers to characterize the normal gas activity of the comet and also to detect, to their own surprise, an active region. This active region is not related to the impact as it was also detected in data collected in June. It shows up about every 41 hours, the rotation period of the comet nucleus determined by the Deep Impact spacecraft. Exciting measurements of the detailed chemical composition (such as the isotopic ratios) of the material released by the impact as well as the one coming from that source will be performed by the astronomers in the next weeks and months. Further spectropolarimetric observations with FORS1 have confirmed the surface of the comet to be rather evolved - as expected - but more importantly, that the dust is not coming from beneath the surface. These data constitute another unique high-quality data set on comets. Comet Tempel 1 may thus be back to sleep but work only starts for the astronomers. More information On July 4, 2005, the NASA Deep Impact spacecraft launched a 360 kg impactor onto Comet 9P/Tempel 1. This experiment is seen by many as the first opportunity to study the crust and the interior of a comet, revealing new information on the early phases of the Solar System. ESO actively participated in pre- and post-impact observations. Apart from a long-term monitoring of the comet, for two days before and six days after, all major ESO telescopes - i.e. the four Unit Telescopes of the Very Large Telescope Array at Paranal, as well as the 3.6m, 3.5m NTT and the 2.2m ESO/MPG telescopes at La Silla - have been observing Comet 9P/Tempel 1, in a coordinated fashion and in very close collaboration with the space mission' scientific team. The simultaneous use of all ESO telescopes with all together 10 instruments has an enormous potential, since it allows for observation of the comet at different wavelengths in the visible and infrared by imaging, spectroscopy and polarimetry. Such multiplexing capabilities of the instrumentation do not exist at any other observatory in the world. More information is available at the dedicated Deep Impact at ESO web site.

VLT/I Instrumentation: Lessons Learned FORUM

NASA Astrophysics Data System (ADS)

Monnet, G.; Bacon, R.

2003-09-01

This paper is the result of a joint effort by ESO and its Scientific and Technical Committee (STC) to extract the main lessons from last April's 'VLT/VLTI Instrumentation: Lessons learned' Forum and start applying them, in particular in the framework of the development of second generation VLT -and soon VLTI- instruments. This is but one step in a continuing effort to optimize these complex and challenging developments which involve a significant fraction of Europe's astronomical instrument builders in the near-UV to mid-IR range. With a major effort in the European radio community to build multiple receiver systems for ALMA now being pursued at an accelerated pace, it was also vital to revisit very quickly our whole procurement strategy in this area.

Search for water vapor in the high-resolution transmission spectrum of HD 189733b in the visible

NASA Astrophysics Data System (ADS)

Allart, R.; Lovis, C.; Pino, L.; Wyttenbach, A.; Ehrenreich, D.; Pepe, F.

2017-10-01

Context. Ground-based telescopes equipped with state-of-the-art spectrographs are able to obtain high-resolution transmission and emission spectra of exoplanets that probe the structure and composition of their atmospheres. Various atomic and molecular species, such as Na, CO, H2O have been already detected in a number of hot Jupiters. Molecular species have been observed only in the near-infrared while atomic species have been observed in the visible. In particular, the detection and abundance determination of water vapor bring important constraints to the planet formation process. Aims: We aim to search for water vapor in the atmosphere of the exoplanet HD 189733b using a high-resolution transmission spectrum in the visible obtained with HARPS. Methods: We used the atmospheric transmission code Molecfit to correct for telluric absorption features. Then we computed the high-resolution transmission spectrum of the planet using three transit datasets. We finally searched for water vapor absorption in the water band around 6500 Å using a cross-correlation technique that combines the signal of 600-900 individual lines. Results: Telluric features are corrected to the noise level. We place a 5-σ upper limit of 100 ppm on the strength of the 6500 Å water vapor band. The 1-σ precision of 20 ppm on the transmission spectrum demonstrates that space-like sensitivity can be achieved from the ground, even for a molecule that is a strong telluric absorber. Conclusions: This approach opens new possibilites for the detection of various atomic and molecular species with future instruments such as ESPRESSO at the VLT. Extrapolating from our results, we show that only one transit with ESPRESSO would be sufficient to detect water vapor on HD 189733b-like hot Jupiter with a cloud-free atmosphere. Upcoming near-IR spectrographs will be even more efficient and sensitive to a wider range of molecular species. Moreover, the detection of the same molecular species in different bands (e.g., visible and IR) is key to constrain the structure and composition of the atmosphere, such as the presence of Rayleigh scattering or aerosols (cloud and/or hazes).

High spectral resolution spectroscopy of the SiO fundamental lines in red giants and red supergiants with VLT/VISIR

NASA Astrophysics Data System (ADS)

Ohnaka, K.

2014-01-01

Context. The mass-loss mechanism in red giants and red supergiants is not yet understood well. The SiO fundamental lines near 8 μm are potentially useful for probing the outer atmosphere, which is essential for clarifying the mass-loss mechanism. However, these lines have been little explored until now. Aims: We present high spectral resolution spectroscopic observations of the SiO fundamental lines near 8.1 μm in 16 bright red giants and red supergiants. Our sample consists of seven normal (i.e., non-Mira) K-M giants (from K1.5 to M6.5), three Mira stars, three optically bright red supergiants, two dusty red supergiants, and the enigmatic object GCIRS3 near the Galactic center. Methods: Our program stars were observed between 8.088 μm and 8.112 μm with a spectral resolution of 30 000 using VLT/VISIR. Results: We detected SiO fundamental lines in all of our program stars except for GCIRS3. The SiO lines in normal K and M giants as well as optically bright (i.e., not dusty) red supergiants do not show P-Cyg profiles or blueshifts, which means the absence of systematic outflows in the SiO line forming region. We detected P-Cyg profiles in the SiO lines in the dusty red supergiants VY CMa and VX Sgr, with the latter object being a new detection. These SiO lines originate in the outflowing gas with the thermal dust continuum emission seen as the background. The outflow velocities of the SiO line forming region in VY CMa and VX Sgr are estimated to be 27 km s-1 and 17 km s-1, respectively. We derived basic stellar parameters (effective temperature, surface gravity, luminosity, and mass) for the normal K-M giants and optically bright red supergiants in our sample and compared the observed VISIR spectra with synthetic spectra predicted from MARCS photospheric models. Most of the SiO lines observed in the program stars warmer than ~3400 K are reasonably reproduced by the MARCS models, which allowed us to estimate the silicon abundance as well as the 28Si/29Si and 28Si/30Si ratios. However, we detected possible absorption excess in some SiO lines. Moreover, the SiO lines in the cooler red giants and red supergiant cannot be explained by the MARCS models at all, even if the dust emission is taken into account. This disagreement may be a signature of the dense, extended molecular outer atmosphere. Based on VISIR observations made with the Very Large Telescope of the European Southern Observatory. Program ID: 087.D-0522(A).Reduced spectra are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A47

Integrating the internal and external training loads in soccer.

PubMed

Akubat, Ibrahim; Barrett, Steve; Abt, Grant

2014-05-01

This study aimed to assess the relationships of fitness in soccer players with a novel integration of internal and external training load (TL). Ten amateur soccer players performed a lactate threshold (LT) test followed by a soccer simulation (Ball-Sport Endurance and Sprint Test [BEAST90mod]). The results from the LT test were used to determine velocity at lactate threshold (vLT), velocity at onset of blood lactate accumulation (vOBLA), maximal oxygen uptake (VO2max), and the heart rate-blood lactate profile for calculation of internal TL (individualized training impulse, or iTRIMP). The total distance (TD) and high intensity distance (HID) covered during the BEAST90mod were measured using GPS technology that allowed measurement of performance and external TL. The internal TL was divided by the external TL to form TD:iTRIMP and HID:iTRIMP ratios. Correlation analyses assessed the relationships between fitness measures and the ratios to performance in the BEAST90mod. vLT, vOBLA, and VO2max showed no significant relationship to TD or HID. HID:iTRIMP significantly correlated with vOBLA (r = .65, P = .04; large), and TD:iTRIMP showed a significant correlation with vLT (r = .69, P = .03; large). The results suggest that the integrated use of ratios may help in the assessment of fitness, as performance alone showed no significant relationships with fitness.

Effects of preventive surgery for unruptured intracranial aneurysms on attention, executive function, learning and memory: a prospective cohort study.

PubMed

Chung, Joonho; Seok, Jeong-Ho; Kwon, Min A; Kim, Yong Bae; Joo, Jin-Yang; Hong, Chang-Ki

2016-01-01

We prospectively evaluated the effects of preventive surgery for unruptured intracranial aneurysms on attention, executive function, learning and memory. Between March 2012 and June 2013, 56 patients were recruited for this study. Fifty-one patients met the inclusion criteria and were enrolled. Inclusion criteria were as follows: (1) age ≤65 years and (2) planned microsurgery or endovascular surgery for unruptured intracranial aneurysm. Exclusion criteria were as follows: (1) preoperative intelligence quotient <80 (n = 3); (2) initial modified Rankin scale ≥1 (n = 1); (3) loss to follow-up (n = 1). An auditory controlled continuous performance test (ACCPT), word-color test (WCT) and verbal learning test (VLT) were performed before and after (6 months) preventive surgery. ACCPT (attention), WCT (executive function) and VLT (learning and memory) scores did not change significantly between the pre- and postoperative evaluations. The ACCPT, WCT, total VLT scores (verbal learning) and delayed VLT scores (memory) did not differ significantly between patients undergoing microsurgery and those undergoing endovascular surgery. However, ACCPT, WCT and delayed VLT scores decreased postoperatively in patients with leukoaraiosis on preoperative FLAIR images (OR 9.899, p = 0.041; OR 11.421, p = 0.006; OR 2.952, p = 0.024, respectively). Preventive surgery for unruptured intracranial aneurysms did not affect attention, executive function, learning or memory. However, patients with leukoaraiosis on FLAIR images might be prone to deficits in attention, executive function and memory postoperatively, whereas learning might not be affected.

77 FR 2346 - Actions Taken Pursuant to Executive Order 13382 Related to the Islamic Republic of Iran Shipping...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-01-17

.... Lucia Street Valletta, VLT 1185, Malta; c/o Irano Hind Shipping Company, PO Box 15875, Mehrshad Street... C31530 (Malta); Web site www.iranohind.com [NPWMD] ISIM AMIN LIMITED, 147/1 St. Lucia Street, Valletta...-Asr Ave., Tehran, Iran; 147/1 St. Lucia Street, Valletta VLT 1185, Malta; Business Registration...

The variable star population in the globular cluster NGC 6934

NASA Astrophysics Data System (ADS)

Yepez, M. A.; Arellano Ferro, A.; Muneer, S.; Giridhar, Sunetra

2018-04-01

We report an analysis of new V and I CCD time-series photometry of the globular cluster NGC 6934. Through the Fourier decomposition of the RR Lyrae light curves the mean values of [Fe/H] and the distance of the cluster were estimated; we found: [Fe/H]UVES = - 1.48 ± 0.14 and d = 16.03 ± 0.42 kpc, and [Fe/H]UVES = - 1.43 ± 0.11 and d = 15.91 ± 0.39 kpc, from the calibrations of RRab and RRc stars respectively. Independent distance estimations from SX Phe and SR stars are also discussed. Individual absolute magnitudes, radii and masses are also reported for RR Lyrae stars. We found 12 new variables: 4 RRab, 3 SX Phe, 2 W Virginis (CW) and 3 semi-regular (SR). The inter-mode or "either-or" region in the instability strip is shared by the RRab and RRc stars. This characteristic, observed only in some OoI clusters and never seen in an OoII, is discussed in terms of mass distribution in the ZAHB.

Reconnaissance of the β Pictoris system down to 1.75 AU with the L' - b and vector vortex coronagraph on VLT/NACO

NASA Astrophysics Data System (ADS)

Milli, J.; Absil, O.; Mawet, D.; Lagrange, A.-M.

2013-09-01

High contrast imaging has thoroughly combed through the limited parameter space accessible with first-generation ground-based adaptive optics instruments and the HST. Only a few objects were discovered, and many non-detections reported and statistically interpreted. The field is now in need of a technological breakthrough. We aim at opening a new parameter space with first-generation systems such as NACO at the Very Large Telescope, by providing ground-breaking inner working angle (IWA) capabilities in the L' band. This mid-infrared wavelength range is a sweet spot for high contrast coronagraphy since the planets-to-star brightness ratio is favorable, while Strehl ratio is naturally higher. An annular groove phase mask (AGPM) vector vortex coronagraph optimized for the L' band, made out of diamond subwavelength gratings has been manufactured and qualified in the lab. The AGPM enables high contrast imaging at very small IWA (here 0".09), potentially being the key to a new parameter space. Here we present the results of the installation and successful commissioning of an L'- band AGPM on VLT/NACO. During a recent science verification run, we imaged the inner regions of Beta Pictoris down to the previously unexplored projected radius of 1.75 AU with unprecedented point source sensitivity. The disk was also clearly resolved down to its inner truncation . The new NACO mode is an opportunity to introduce a more rigorous framework for deriving detection limits at very small angles, which is also relevant for SPHERE and GPI and every high contrast imaging instrument with small IWA ambitions. Indeed, classical tools assuming Gaussian statistics, perfectly valid at large separations, loose significance close to the center simply because the sample size decreases dramatically (fewer resolution elements at a given radius). Moreover, the probability density function (PDF) of speckle noise and associated confidence level for detection depend on radius. ADI was shown to transform speckles'modified Rician PDF into quasi-Gaussian PDF at large separations, but it is expected that this property of ADI does not hold true at small angles. Finally, the flux attenuation induced by ADI, potentially significant at small angles, does not scale linearly with the companion brightness, which makes its calibration more difficult.

Deep Sky Diving with the ESO New Technology Telescope

NASA Astrophysics Data System (ADS)

1998-01-01

Preparations for future cosmological observations with the VLT Within a few months, the first 8.2-meter Unit Telescope of the ESO Very Large Telescope (VLT) array will open its eye towards the sky above the Atacama desert. As documented by recent Press Photos from ESO, the construction work at the Paranal VLT Observatory is proceeding rapidly. Virtually all of the telescope components, including the giant Zerodur mirror (cf. ESO PR Photos 35a-l/97 ), are now on the mountain. While the integration of the telescope and its many optical, mechanical and electronic components continues, astronomers in the ESO member countries and at ESO are now busy defining the observing programmes that will be carried out with the new telescope, soon after it enters into operation. In this context, new and exciting observations have recently been obtained with the 3.5-m New Technology Telescope at the ESO La Silla Observatory, 600 km to the south of Paranal. How to record the faintest and most remote astronomical objects With its very large mirror surface (and correspondingly great light collecting power), as well as an unsurpassed optical quality, the VLT will be able to look exceedingly far out into the Universe, well beyond current horizons. The best technique to record the faintest possible light and thus the most remote celestial objects, is to combine large numbers of exposures of the same field with slightly different telescope pointing. This increases the total number of photons recorded and by imaging the stars and galaxies on different areas (pixels) of the detector, the signal-to-noise ratio and hence the visibility of the faintest objects is improved. The famous Hubble Deep Field Images were obtained in this way by combining over 300 single exposures and they show myriads of faint galaxies in the distant realms of the Universe. The NTT as test bench for the VLT ESO is in the fortunate situation of possessing a `prototype' model of the Very Large Telescope, the 3.5-m New Technology Telescope. Many of the advanced technological concepts now incorporated into the VLT were first tested in the NTT. When this new facility entered into operation at La Silla in 1990, it represented a break-through in telescope technology and it has since then made many valuable contributions to front-line astronomical projects. Last year, the control and data flow system at the NTT was thoroughly refurbished to the high VLT standards and current observations with the NTT closely simulate the future operation of the VLT. The successful, early tests with the new operations system have been described in ESO Press Release 03/97. The NTT SUSI Deep Field With the possibility to test already now observing procedures which will become standard for the operation of the VLT, a group of astronomers [1] was granted NTT time for observations of Faint Galaxies in an Ultra-Deep Multicolour SUSI field . This is a programme aimed at the study of the distribution of faint galaxies in the field and of gravitational lensing effects (cosmic mirages and deformation of images of distant galaxies caused by the gravitational field of intervening matter). SUSI (SUperb Seeing Imager) is a high-resolution CCD-camera at the NTT that is particularly efficient under excellent sky conditions. The observations were fully defined in advance and were carried out in service mode from February to April 1997 with flexible scheduling by a team of dedicated ESO astronomers (the NTT team). Only in this way was it possible to obtain the exposures under optimal atmospheric conditions, i.e. `photometric' sky and little atmospheric turbulence (seeing better than 1 arcsec). A total of 122 CCD frames were obtained in four colours (blue, green-yellow, red and near-infrared) with a total exposure time of no less than 31.5 hours. The frames cover a 2.3 x 2.3 arcmin `empty' sky field centered south of the high-redshift quasar QSO BR 1202-0725 (z=4.7), located just south of the celestial equator. ESO PR Photo 01a/98 Caption to ESO PR Photo 01/98 and access to two versions of the photo The frames were computer processed and combined to yield a colour view of the corresponding sky field ( ESO Press Photo 01/98 ). This is indeed a very deep look into the southern sky. The astronomers have found that the limiting magnitude (at a signal-to-noise ratio of 3) is beyond 27 in the blue and red frames and only slightly brighter in the two others. Magnitude 27 corresponds to a brightness that is 250 million times fainter than what can be perceived with the unaided eye. Although not as deep as the Hubble Deep Field due to the shorter exposure time and brighter sky background (caused by light emission in the upper layers of the terrestrial atmosphere), this new set of data is among the best ground-based observations of this type ever obtained. Galaxies down to a magnitude of roughly 25 will soon be targets of detailed spectroscopic observations with the VLT. They will provide a measure of their basic physical parameters like redshift, luminosity and mass. How to access the new data This scientific program aims at the study of the photometric redshift distribution of the faint galaxies [2] and of gravitational lensing effects (cosmic mirages). It has been decided to make the complete data set available to the wide scientific community and it is expected that many astronomers all over the world will want to perform their own investigations by means of this unique observational material. A full description of the project is available on the ESO Web at http://www.eso.org/ndf/. Here you will find a comprehensive explanation of the scientific background, details about the observations and the data reduction, as well as easy access to the corresponding data files. Notes: [1] The group consists of Sandro D'Odorico (Principal Investigator, ESO) and Jacqueline Bergeron (ESO), Hans-Martin Adorf (ESO), Stephane Charlot (IAP, Paris, France), David Clements (IAS, Orsay, France), Stefano Cristiani (Univ. of Padova, Italy), Luiz da Costa (ESO), Eiichi Egami (MPI Extraterrestrial Physics, Garching, Germany), Adriano Fontana (Rome Observatory, Italy), Bernard Fort (Paris Observatory, France), Laurent Gautret (Paris Observatory, France), Emanuele Giallongo (Rome Observatory, Italy), Roberto Gilmozzi, Richard N.Hook and Bruno Leibundgut (ESO), Yannick Mellier and Patrick Petitjean (IAP, Paris, France), Alvio Renzini, Sandra Savaglio and Peter Shaver (ESO), Stella Seitz (Munich Observatory, Germany) and Lin Yan (ESO). [2]. The photometric redshift method allows to determine an approximate distance of a distant galaxy by measuring its colour, i.e., its relative brightness (magnitude) in different wavebands. It is based on the proportionality between the distance of a galaxy and its recession velocity (the Hubble law). The higher the velocity, the more its emission will be shifted towards longer wavelengths and the redder is the colour. Recent investigations of galaxies seen in the Hubble Deep Field have shown that the redshifts (and thus distances) found by this method are quite accurate in most cases. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

High resolution of fast-rotating stars across the H-R diagram: photosphere and circumstellar environment

NASA Astrophysics Data System (ADS)

Domiciano de Souza, Armando

2014-12-01

Rotation is a fundamental parameter that governs the physical structure and evolution of stars, for example by generating internal circulations of matter and angular momentum, which in turn change the stellar lifetime. Massive stars (spectral types OBA) are those presenting the highest rotation velocities and thus those for which the consequences of rotation are the strongest. On the external layers of the star, fast-rotation induces in particular (1) a flattening (equatorial radius higher than the polar radius) and (2) a gravity darkening (non-uniform distribution of flux, and thus effective temperature, between the poles and the equator). This important modification in the photospheric physical structure can also drive an anisotropic (axisymmetric) mass and angular momentum loss, originating for example the complex circumstellar environments around Be and supergiant B[e] stars. The techniques of high angular and high spectral resolution allow a detailed study of the effects of rotation on the stellar photosphere and circumstellar environment across the H-R diagram. Thanks to these techniques, and in particular to the optical/infrared long-baseline interferometry, our knowledge on the impact of rotation in stellar physics was highly deepened since the beginning of the XXI century. The results described in this Habilitation Thesis are placed in this context and are the fruit a double approach combining both (1) observation, mainly with the ESO-VLT(I) instruments (e.g. NACO, VISIR, MIDI, AMBER, PIONIER) and (2) astrophysical modeling with different codes, including also radiation transfer (CHARRON, HDUST, FRACS). I present, in particular, the results obtained on three fast-rotating stars: Altair (A7V; delta Scuti), Achernar (B6Ve; Be star), and CPD-57° 2874 (supergiant B[e] star).

Quantitative Spectroscopy of Supergiants in the Local Group Dwarf Galaxy IC 1613: Metallicity and Distance

NASA Astrophysics Data System (ADS)

Berger, Travis A.; Kudritzki, Rolf-Peter; Urbaneja, Miguel A.; Bresolin, Fabio; Gieren, Wolfgang; Pietrzyński, Grzegorz; Przybilla, Norbert

2018-06-01

We present a spectral analysis of 21 blue supergiant stars of spectral types late B to early A within the Local Group dwarf galaxy IC 1613, based on VLT Focal Reducer and Low Dispersion Spectrograph 2 low-resolution spectra. Combining our results with studies of early B-type blue supergiants, we report a wide bimodal distribution of metallicities with two peaks around [Z] ∼ ‑0.50 dex and [Z] ∼ ‑0.85 dex. The bimodal distribution correlates with spatial location, when compared with column densities of neutral hydrogen in IC 1613. While the low [Z] objects appear in regions of relatively high ISM H I column densities or close to them, the high [Z] supergiants are found in the central H I hole that is almost devoid of hydrogen. This suggests there are varied chemical evolution histories for the young stellar populations in IC 1613. Utilizing the flux-weighted gravity–luminosity relation, we determine IC 1613's distance modulus as m ‑ M = 24.39 ± 0.11 mag. This value is in agreement within previous distance measurements using the near-infrared period–luminosity relationship of Cepheids and the tip of the red giant branch.

VLT Images the Horsehead Nebula

NASA Astrophysics Data System (ADS)

2002-01-01

Summary A new, high-resolution colour image of one of the most photographed celestial objects, the famous "Horsehead Nebula" (IC 434) in Orion, has been produced from data stored in the VLT Science Archive. The original CCD frames were obtained in February 2000 with the FORS2 multi-mode instrument at the 8.2-m VLT KUEYEN telescope on Paranal (Chile). The comparatively large field-of-view of the FORS2 camera is optimally suited to show this extended object and its immediate surroundings in impressive detail. PR Photo 02a/02 : View of the full field around the Horsehead Nebula. PR Photo 02b/02 : Enlargement of a smaller area around the Horse's "mouth" A spectacular object ESO PR Photo 02a/02 ESO PR Photo 02a/02 [Preview - JPEG: 400 x 485 pix - 63k] [Normal - JPEG: 800 x 970 pix - 896k] [Full-Res - JPEG: 1951 x 2366 pix - 4.7M] ESO PR Photo 02b/02 ESO PR Photo 02b/02 [Preview - JPEG: 400 x 501 pix - 91k] [Normal - JPEG: 800 x 1002 pix - 888k] [Full-Res - JPEG: 1139 x 1427 pix - 1.9M] Caption : PR Photo 02a/02 is a reproduction of a composite colour image of the Horsehead Nebula and its immediate surroundings. It is based on three exposures in the visual part of the spectrum with the FORS2 multi-mode instrument at the 8.2-m KUEYEN telescope at Paranal. PR Photo 02b/02 is an enlargement of a smaller area. Technical information about these photos is available below. PR Photo 02a/02 shows the famous "Horsehead Nebula" , which is situated in the Orion molecular cloud complex. Its official name is Barnard 33 and it is a dust protrusion in the southern region of the dense dust cloud Lynds 1630 , on the edge of the HII region IC 434 . The distance to the region is about 1400 light-years (430 pc). This beautiful colour image was produced from three images obtained with the multi-mode FORS2 instrument at the second VLT Unit Telescope ( KUEYEN ), some months after it had "First Light", cf. PR 17/99. The image files were extracted from the VLT Science Archive Facility and the photo constitutes a fine example of the subsequent use of such valuable data. Details about how the photo was made and some weblinks to other pictures are available below. The comparatively large field-of-view of the FORS2 camera (nearly 7 x 7 arcmin 2 ) and the detector resolution (0.2 arcsec/pixel) make this instrument optimally suited for imaging of this extended object and its immediate surroundings. There is obviously a wealth of detail, and scientific information can be derived from the colours shown in this photo. Three predominant colours are seen in the image: red from the hydrogen (H-alpha) emission from the HII region; brown for the foreground obscuring dust; and blue-green for scattered starlight. The blue-green regions of the Horsehead Nebula correspond to regions not shadowed from the light from the stars in the H II region to the top of the picture and scatter stellar radiation towards the observer; these are thus `mountains' of dust . The Horse's `mane' is an area in which there is less dust along the line-of-sight and the background (H-alpha) emission from ionized hydrogen atoms can be seen through the foreground dust. A chaotic area At the high resolution of this image the Horsehead appears very chaotic with many wisps and filaments and diffuse dust . At the top of the figure there is a bright rim separating the dust from the HII region. This is an `ionization front' where the ionizing photons from the HII region are moving into the cloud, destroying the dust and the molecules and heating and ionizing the gas. Dust and molecules can exist in cold regions of interstellar space which are shielded from starlight by very large layers of gas and dust. Astronomers refer to elongated structures, such as the Horsehead, as `elephant trunks' (never mind the zoological confusion!) which are common on the boundaries of HII regions. They can also be seen elsewhere in Orion - another well-known example is the pillars of M16 (the "Eagle Nebula") made famous by the fine HST image - a new infrared view by VLT and ISAAC of this area was published last month, cf. PR 25/01. Such structures are only temporary as they are being constantly eroded by the expanding region of ionized gas and are destroyed on timescales of typically a few thousand years. The Horsehead as we see it today will therefore not last forever and minute changes will become observable as the time passes. The surroundings To the east of the Horsehead (at the bottom of this image) there is ample evidence for star formation in the Lynds 1630 dark cloud . Here, the reflection nebula NGC 2023 surrounds the hot B-type star HD 37903 and some Herbig Haro objects are found which represent high-speed gas outflows from very young stars with masses of around a solar mass. The HII region to the west (top of picture) is ionized by the strong radiation from the bright star Sigma Orionis , located just below the southernmost star in Orion's Belt. The chain of dust and molecular clouds are part of the Orion A and B regions (also known as Orion's `sword' ). Other images of the Horsehead Nebula The Horsehead Nebula is a favourite object for amateur astrophotographers and large numbers of images are available on the WWW. Due to its significant extension and the limited field-of-view of some professional telescopes, fewer photographs are available from today's front-line facilities, except from specialized wide-field instruments like Schmidt telescopes, etc. The links below point to a number of prominent photos obtained elsewhere and some contain further useful links to other sites with more information about this splendid sky area. "Astronomy Picture of the Day" : http://antwrp.gsfc.nasa.gov/apod/ap971025.html Hubble Heritage image : http://hubble.stsci.edu/news_.and._views/pr.cgi?2001%2B12 INT Wide-Field image : http://www.ing.iac.es/PR/science/horsehead.htm NOT image : http://www.not.iac.es/new/general/photos/astronomical/ NOAO Wide-Field image : http://www.noao.edu/outreach/press/pr01/ir0101.html Bill Arnett's site : http://www.seds.org/billa/twn/b33x.html Technical information about the photos PR Photo 02a/02 was produced from three images, obtained on February 1, 2000, with the FORS2 multi-mode instrument at the 8.2-m KUEYEN Unit Telescope and extracted from the VLT Science Archive Facility. The frames were obtained in the B-band (600 sec exposure; wavelength 429 nm; FWHM 88 nm; here rendered as blue), V-band (300 sec; 554 nm; 112 nm; green) and R-band (120 sec; 655 nm; 165 nm; red) The original pixel size is 0.2 arcsec. The photo shows the full field recorded in all three colours, approximately 6.5 x 6.7 arcmin 2. The seeing was about 0.75 arcsec. PR Photo 02b/02 is an enlargement of a smaller area, measuring 3.8 x 4.1 arcmin 2. North is to the left and east is down (the usual orientation for showing this object). The frames were recorded with a TK2048 SITe CCD and the ESO-FIERA Controller, built by the Optical Detector Team (ODT). The images were prepared by Cyril Cavadore (ESO-ODT) , by means of Prism software. ESO PR Photos 02a-b/02 may be reproduced, if credit is given the European Southern Observatory (ESO).

Close Companions to Nearby Young Stars from Adaptive Optics Imaging on VLT and Keck

NASA Astrophysics Data System (ADS)

Haisch, Karl E.; Jayawardhana, Ray; Brandeker, Alexis; Mardones, Diego

We report the results of VLT and Keck adaptive optics surveys of known members of the η Chamaeleontis, MBM 12, and TW Hydrae (TWA) associations to search for close companions. The multiplicity statistics of η Cha, MBM 12, and TWA are quite high compared with other clusters and associations, although our errors are large due to small number statistics. We have resolved S18 in MBM 12 and RECX 9 in η Cha into triples for the first time. The tight binary TWA 5Aab in the TWA offers the prospect of measuring the dynamical masses of both components as well as an independent distance to the system within a few years. The AO detection of the close companion to the nearby young star χ1 Orionis, previously inferred from radial velocity and astrometric observations, has already made it possible to derive the dynamical masses of that system without any astrophysical assumption.

With the VLT Interferometer towards Sharper Vision

NASA Astrophysics Data System (ADS)

2000-05-01

The Nova-ESO VLTI Expertise Centre Opens in Leiden (The Netherlands) European science and technology will gain further strength when the new, front-line Nova-ESO VLTI Expertise Centre (NEVEC) opens in Leiden (The Netherlands) this week. It is a joint venture of the Netherlands Research School for Astronomy (NOVA) (itself a collaboration between the Universities of Amsterdam, Groningen, Leiden, and Utrecht) and the European Southern Observatory (ESO). It is concerned with the Very Large Telescope Interferometer (VLTI). The Inauguration of the new Centre will take place on Friday, May 26, 2000, at the Gorlaeus Laboratory (Lecture Hall no. 1), Einsteinweg 55 2333 CC Leiden; the programme is available on the web. Media representatives who would like to participate in this event and who want further details should contact the Nova Information Centre (e-mail: jacques@astro.uva.nl; Tel: +31-20-5257480 or +31-6-246 525 46). The inaugural ceremony is preceded by a scientific workshop on ground and space-based optical interferometry. NEVEC: A Technology Centre of Excellence As a joint project of NOVA and ESO, NEVEC will develop in the coming years the expertise to exploit the unique interferometric possibilities of the Very Large Telescope (VLT) - now being built on Paranal mountain in Chile. Its primary goals are the * development of instrument modeling, data reduction and calibration techniques for the VLTI; * accumulation of expertise relevant for second-generation VLTI instruments; and * education in the use of the VLTI and related matters. NEVEC will develop optical equipment, simulations and software to enable interferometry with VLT [1]. The new Center provides a strong impulse to Dutch participation in the VLTI. With direct involvement in this R&D work, the scientists at NOVA will be in the front row to do observations with this unique research facility, bound to produce top-level research and many exciting new discoveries. The ESO VLTI at Paranal ESO PR Photo 14a/00 ESO PR Photo 14a/00 [Preview - JPEG: 359 x 400 pix - 120k] [Normal - JPEG: 717 x 800 pix - 416k] [High-Res - JPEG: 2689 x 3000 pix - 6.7M] Caption : A view of the Paranal platform with the four 8.2-m VLT Unit Telescopes (UTs) and the foundations for the 1.8-m VLT Auxiliary Telescopes (ATs) that together will be used as the VLT Interferometer (VLTI). The three ATs will move on rails (yet to be installed) between the thirty observing stations above the holes that provide access to the underlying tunnel system. The light beams from the individual telescopes will be guided towards the centrally located, partly underground Interferometry Laboratory in which the VLTI instruments will be set up. This photo was obtained in December 1999 at which time some construction materials were still present on the platform; they were electronically removed in this reproduction. The ESO VLT facility at Paranal (Chile) consists of four Unit Telescopes with 8.2-m mirrors and several 1.8-m auxiliary telescopes that move on rails, cf. PR Photo 14a/00 . While each of the large telescopes can be used individually for astronomical observations, a prime feature of the VLT is the possibility to combine all of these telescopes into the Very Large Telescope Interferometer (VLTI) . In the interferometric mode, the light beams from the VLT telescopes are brought together at a common focal point in the Interferometry Laboratory that is placed at the centre of the observing platform on top of Paranal. In principle, this can be done in such a way that the resulting (reconstructed) image appears to come from a virtual telescope with a diameter that is equal to the largest distance between two of the individual telescopes, i.e., up to about 200 metres. The theoretically achievable image sharpness of an astronomical telescope is proportional to its diameter (or, for an interferometer, the largest distance between two of its component telescopes). The interferometric observing technique will thus allow the VLTI to produce images as sharp as 0.001 arcsec (at wavelength 1 µm) - this corresponds to viewing the shape of a golfball at more than 8,000 km distance. The VLTI will do even better when this technique is later extended to shorter wavelengths in the visible part of the spectrum - it may ultimately distinguish human-size objects on the surface of the Moon (a 2-metre object at this distance, about 400,000 km, subtends an angle of about 0.001 arcsec). However, interferometry with the VLT demands that the wavefronts of light from the individual telescopes that are up to 200 meters apart must be matched exactly, with less than 1 wavelength of difference. This demands continuous mechanical stability to a fraction of 1 µm (0.001 mm) for the heavy components over such large distances, and is a technically formidable challenge. This is achieved by electronic feed-back loops that measure and adjust the distances during the observations. In addition, continuous and automatic correction of image distortions from air turbulence in the telescopes' field of view is performed by means of adaptive optics [2]. VLTI technology at ESO, industry and institutes The VLT Interferometer is based on front-line technologies introduced and advanced by ESO, and its many parts are now being constructed at various sites in Europe. ESO PR Photo 14b/00 ESO PR Photo 14b/00 [Preview - JPEG: 359 x 400 pix - 72k] [Normal - JPEG: 717 x 800 pix - 200k] [High-Res - JPEG: 2687 x 3000 pix - 1.3M] Caption : Schematic lay-out of the VLT Interferometer. The light from a distant celestial objects enters two of the VLT telescopes and is reflected by the various mirrors into the Interferometric Tunnel, below the observing platform on the top of Paranal. Two Delay Lines with moveable carriages continuously adjust the length of the paths so that the two beams interfere constructively and produce fringes at the interferometric focus in the laboratory. In 1998, Fokker Space (also in Leiden, The Netherlands) was awarded a contract for the delivery of the three Delay Lines of the VLTI. This mechanical-optical system will compensate the optical path differences of the light beams from the individual telescopes. It is necessary to ensure that the light from all telescopes arrives in the same phase at the focal point of the interferometer. Otherwise, the very sharp interferometric images cannot be obtained. More details are available in the corresponding ESO PR 04/98 and recent video sequences, included in ESO Video News Reel No. 9 and Video Clip 04a/00 , cf. below. Also in 1998, the company AMOS (Liège, Belgium) was awarded an ESO contract for the delivery of the three 1.8-m Auxiliary Telescopes (ATs) and of the full set of on-site equipment for the 30 AT observing stations, cf. ESO PR Photos 25a-b/98. This work is now in progress at the factory - various scenes are incorporated into ESO Video News Reel No. 9 and Video Clip 04b/00 . Several instruments for imaging and spectroscopy are currently being developed for the VLTI. The first will be the VLT Interferometer Commissioning Instrument (VINCI) that is the test and first-light instrument for the VLT Interferometer. It is being built by a consortium of French and German institutes under ESO contract. The VLTI Near-Infrared / Red Focal Instrument (AMBER) is a collaborative project between five institutes in France, Germany and Italy, under ESO contract. It will operate with two 8.2-m UTs in the wavelength range between 1 and 2.5 µm during a first phase (2001-2003). The wavelength coverage will be extended in a second phase down to 0.6 µm (600 nm) at the time the ATs become operational. Main scientific objectives are the investigation at very high-angular resolution of disks and jets around young stellar objects and dust tori at active galaxy nuclei with spectroscopic observations. The Phase-Referenced Imaging and Microarcsecond Astrometry (PRIMA) device is managed by ESO and will allow simultaneous interferometric observations of two objects - each with a maximum size of 2 arcsec - and provide exceedingly accurate positional measurements. This will be of importance for many different kinds of astronomical investigations, for instance the search for planetary companions by means of accurate astrometry. The MID-Infrared interferometric instrument (MIDI) is a project collaboration between eight institutes in France, Germany and the Netherlands [1], under ESO contract. The actual design of MIDI is optimized for operation at 10 µm and a possible extension to 20 µm is being considered. Notes [1] The NEVEC Centre is involved in the MIDI project for the VLTI. Another joint project between ESO and NOVA is the Wide-Field Imager OMEGACAM for the VLT Survey Telescope (VST) that will be placed at Paranal. [2] Adaptive Optics systems allow to continuously "re-focus" an astronomical telescope in order to compensate for the atmospheric turbulence and thus to obtain the sharpest possible images. The work at ESO is described on the Adaptive Optics Team Homepage. VLTI-related videos now available In conjunction with the Inauguration of the NEVEC Centre (Leiden, The Netherlands) on May 26, 2000, ESO has issued ESO Video News Reel No. 9 (May 2000) ( "The Sharpest Vision - Interferometry with the VLT" ). Tapes with this VNR, suitable for transmission and in full professional quality (Betacam, etc.), are now available for broadcasters upon request; please contact the ESO EPR Department for more details. Extracts from this VNR are available as ESO Video Clips 04a/00 and 04b/00 . ESO PR Video Clip 04a/00 [160x120 pix MPEG-version] ESO PR Video Clip 04a/00 (2600 frames/1:44 min) [MPEG Video+Audio; 160x120 pix; 2.4Mb] [MPEG Video+Audio; 320x240 pix; 4.8 Mb] [RealMedia; streaming; 33kps] [RealMedia; streaming; 200kps] ESO Video Clip 04a/00 shows some recent tests with the prototype VLT Delay Line carriage at FOKKER Space (Leiden, The Netherlands. This device is crucial for the proper functioning of the VLTI and will be mounted in the main interferometric tunnel at Paranal. Contents: Outside view of the FOKKER site. The carriage on rails. The protecting cover is removed. View towards the cat's eye. The carriage moves on the rails. ESO PR Video Clip 04b/00 [160x120 pix MPEG-version] ESO PR Video Clip 04b/00 (3425 frames/2:17 min) [MPEG Video+Audio; 160x120 pix; 3.2Mb] [MPEG Video+Audio; 320x240 pix; 6.3 Mb] [RealMedia; streaming; 33kps] [RealMedia; streaming; 200kps] ESO Video Clip 04b/00 shows the construction of the 1.8-m VLT Auxiliary Telescopes at AMOS (Liège, Belgium). Contents: External view of the facility. Computer drawing of the mechanics. The 1.8-m mirror (graphics). Construction of the centerpiece of the telescope tube. Mechanical parts. Checking the optical shape of an 1.8-m mirror. Mirror cell with supports for the 1.8-m mirror. Test ramp with rails on which the telescope moves and an "observing station" (the hole). The telescope yoke that will support the telescope tube. Both clips are available in four versions: two MPEG files and two streamer-versions of different sizes; the latter require RealPlayer software. They may be freely reproduced if ESO is mentioned as source. Most of the ESO PR Video Clips at the ESO website provide "animated" illustrations of the ongoing work and events at the European Southern Observatory. The most recent clip was: ESO PR Video Clip 03/00 with a trailer for "Physics on Stage" (2 May 2000). Information is also available on the web about other ESO videos.

The photospheric solar oxygen project. II. Non-concordance of the oxygen abundance derived from two forbidden lines

NASA Astrophysics Data System (ADS)

Caffau, E.; Ludwig, H.-G.; Malherbe, J.-M.; Bonifacio, P.; Steffen, M.; Monaco, L.

2013-06-01

Context. In the Sun, the two forbidden [O i] lines at 630 and 636 nm were previously found to provide discrepant oxygen abundances. Aims: We investigate whether this discrepancy is peculiar to the Sun or whether it is also observed in other stars. Methods: We make use of high-resolution, high signal-to-noise ratio spectra of four dwarf to turn-off stars, five giant stars, and one sub-giant star observed with THEMIS, HARPS, and UVES to investigate the coherence of the two lines. Results: The two lines provide oxygen abundances that are consistent, within observational errors, in all the giant stars examined by us. On the other hand, for the two dwarf stars for which a measurement was possible, for Procyon, and for the sub-giant star Capella, the 636 nm line provides systematically higher oxygen abundances, as already seen for the Sun. Conclusions: The only two possible reasons for the discrepancy are a serious error in the oscillator strength of the Ni i line blending the 630 nm line or the presence of an unknown blend in the 636 nm line, which makes the feature stronger. The CN lines blending the 636 nm line cannot be responsible for the discrepancy. The Ca i autoionisation line, on the red wing of which the 636 nm line is formed, is not well modelled by our synthetic spectra. However, a better reproduction of this line would result in even higher abundances from the 636 nm, thus increasing the discrepancy. Based on observations collected at ESO Paranal Observatory, Programme 182.D-5053(A).

CHEMICAL ANALYSIS OF ASYMPTOTIC GIANT BRANCH STARS IN M62

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lapenna, E.; Mucciarelli, A.; Ferraro, F. R.

2015-11-10

We have collected UVES-FLAMES high-resolution spectra for a sample of 6 asymptotic giant branch (AGB) and 13 red giant branch (RGB) stars in the Galactic globular cluster (GC) M62 (NGC 6266). Here we present the detailed abundance analysis of iron, titanium, and light elements (O, Na, Mg, and Al). For the majority (five out of six) of the AGB targets, we find that the abundances of both iron and titanium determined from neutral lines are significantly underestimated with respect to those obtained from ionized features, the latter being, instead, in agreement with those measured for the RGB targets. This ismore » similar to recent findings in other clusters and may suggest the presence of nonlocal thermodynamic equilibrium (NLTE) effects. In the O–Na, Al–Mg, and Na–Al planes, the RGB stars show the typical correlations observed for GC stars. Instead, all the AGB targets are clumped in the regions where first-generation stars are expected to lie, similar to what was recently found for the AGB population of NGC 6752. While the sodium and aluminum abundances could be underestimated as a consequence of the NLTE bias affecting iron and titanium, the oxygen line used does not suffer from the same effects, and the lack of O-poor AGB stars therefore is a solid result. We can thus conclude that none of the investigated AGB stars belongs to the second stellar generation of M62. We also find an RGB star with extremely high sodium abundance ([Na/Fe] = +1.08 dex)« less

The Paranal Metamorphosis

NASA Astrophysics Data System (ADS)

2000-12-01

Some years ago, the Paranal mountain was still a remote and inhospitable site, some 12 km from the Pacific Coast in the dry Atacama desert in northern Chile. Few aircraft passengers flying along that coast would notice anything particular about this peak, except perhaps that it was one of the tallest in the steep coastal mountain range. Already in the early 1960's, pioneer astronomers crossed this desolate region in search of suitable sites for future observatories. One of them, Jürgen Stock , did notice the Paranal peak as a possible candidate. However, without any water in this extremely dry area, how could any people, even hardy scientists, ever live up there? He then went on to discover La Silla, where ESO decided to build its first observatory in 1964. ESO presence at Paranal from 1983 In the beginning of the 1980's, when the main construction phase at La Silla was over, ESO launched a thorough search for the best possible site for the next-generation telescope, already then known as the "Very Large Telescope", or VLT. During this campaign, the Paranal mountain was visited by a small search troupe from this organisation, including the ESO Director General (1975 - 1987), Lo Woltjer . The first test measurements indicated a great potential for astronomical observations, both in term of clear nights and low humidity, the latter being particularly important for infrared observations. From 1983, ESO maintained a small site testing station at the top of Paranal. The meteorological conditions were registered around the clock and the atmospheric transparency and stability were recorded each night. At that time, the mountain Vizcachas, a site near ESO's first observatory, La Silla, and some 600 km further south, was also considered a possible site for the VLT. The data from the two sites were therefore carefully compared over a period of several years. Paranal becomes the site for the VLT Following the decision in December 1987 by the ESO Council to embark upon the VLT Project (with Massimo Tarenghi as Project Manager), Paranal was chosen as the site in 1991. In the meantime, the Chilean Government had resolved to donate an area of approx. 700 km 2 around this mountain to ESO, and construction work started the same year. The left photo shows Paranal at this stage. The development of Paranal included much blasting and heavy earthwork; about 350,000 m 3 of rock had to be moved to achieve a flat platform of sufficient size to house the various components of the VLT and, in particular, the spacious VLT Interferometer. The situation, right after this work, is depicted in the middle photo from 1994. An operational observatory The construction at Paranal progressed at high speed. It is hard to believe that just four years later, "First Light" was achieved with the first 8.2-m telescope, ANTU, in May 1998. Then followed KUEYEN (March 1999), MELIPAL (January 2000) and YEPUN (September 2000). The first two telescopes have now been "taken over" by the astronomers and Paranal has become an operational observatory with Roberto Gilmozzi as Director. Large numbers of scientists in the ESO member countries, and even more within international collaborations, are busy producing exciting research results, now increasingly visible in the world's professional journals and some of which are announced in the ESO Press Releases. The other two will soon be equipped with high-quality astronomical instruments; the first will be VIMOS at MELIPAL in the beginning of 2001. Both telescopes will become fully available to the astronomical community in the course of 2001. And now the VLT Interferometer... The next decisive step will happen already in early 2001, when the VLT Interferometer is expected to see "First Fringes", the equivalent of "First Light" for this type of facility. This is when two small "siderostats" on the Paranal platform will track and capture the light from one and the same (bright) star, directing the two beams towards the underground Interferometric Laboratory via a series of intermediate mirrors. Here, the critical technical elements are the "delay lines" in the Interferometric Tunnel, cf. ESO Press Photos 26a-e/00.They have already undergone the first tests with very positive results, so the ESO staff is in a confident mood. Later in 2001, two of the 8.2-m Unit Telescopes will be coupled and interferometric test observations will be made on faint celestial objects. In the next years, the three movable 1.8-m Auxiliary Telescopes will be installed on the Paranal "railroad" and the VLT Interferometer will progressively enter into full operation. From a lonely mountain top to the world's foremost optical/infrared astronomical observatory, Paranal has indeed come a long way! This is the caption to ESO PR Photo 36/00 . It may be reproduced, if credit is given to the European Southern Observatory.

Polarimetric Imaging Of Protoplanetary Disks From The Optical To Sub-Mm

NASA Astrophysics Data System (ADS)

De Boer, Jos; Ménard, F.; Pinte, C.; van der Plas, G.; Snik, F.

2017-10-01

To learn how planets form from the smallest building blocks within protoplanetary disks, we first need to know how dust grains grow from micron to mm sizes. Polarimetry across the spectrum has proven to be sensitive to grain properties like dust size distribution and composition and thus can be used to characterize the scattering grains. However, polarization measured with radio interferometric arrays is rarely studied in concert with optical polarimetry. Our team has successfully calibrated the NIR polarimetric imaging mode of VLT/SPHERE, hence upgrading the instrument from a high-contrast imager to a robust tool for quantitative characterization. In this presentation, we will discuss which lessons can be learned by comparing polarimetry in the optical and sub-mm and explore for which science cases both techniques can complement each other. When we combine the polarimetric capabilities of the most advanced optical high-contrast imagers (e.g., Gemini GPI or VLT SPHERE) with that of ALMA we will be able to study the spatial distribution of an extensive range of different grains, which allows us to take an essential step towards a deeper understanding of planet formation.

Adaptive optics for the ESO-VLT

NASA Astrophysics Data System (ADS)

Merkle, Fritz

1989-04-01

This paper discusses adaptive optics, its performance, and its requirements for applications in astronomy to overcome limitations due to atmospheric turbulence. Guidelines for the implementation of these devices in telescopes are given, in particular for the Very Large Telescope (VLT) at ESO. It is intended to equip each one of the four 8-m telescopes of the VLT, which are arranged in a linear array with an independent adaptive optical system. These systems will serve the individual and the combined coude foci. A small-scale prototype adaptive system is under development. It is equipped with a 19-piezoelectric-actuator deformable mirror, a Shack-Hartmann-type wavefront sensor, and a dedicated wavefront computer for closing the feedback loop. This system is based on a polychromatic approach; i.e., it senses the wavefront in the visible, but the adaptive correction loop works at 3-5 microns.

C/O ratios in planetary nebulae with dual-dust chemistry from faint optical recombination lines

NASA Astrophysics Data System (ADS)

García-Rojas, J.; Delgado-Inglada, G.; García-Hernández, D. A.; Dell'Agli, F.; Lugaro, M.; Karakas, A. I.; Rodríguez, M.

2018-02-01

We present deep high-resolution (R ˜ 15 000) and high-quality UVES optical spectrophotometry of nine planetary nebulae with dual-dust chemistry. We compute physical conditions from several diagnostics. Ionic abundances for a large number of ions of N, O, Ne, S, Cl, Ar, K, Fe and Kr are derived from collisionally excited lines. Elemental abundances are computed using state-of-the-art ionization correction factors. We derive accurate C/O ratios from optical recombination lines. We have re-analysed additional high-quality spectra of 14 PNe from the literature following the same methodology. Comparison with asymptotic giant branch models reveals that about half of the total sample objects are consistent with being descendants of low-mass progenitor stars (M < 1.5 M⊙). Given the observed N/O, C/O and He/H ratios, we cannot discard that some of the objects come from more massive progenitor stars (M > 3-4 M⊙) that have suffered a mild hot bottom burning. None of the objects seem to be descendant of very massive progenitors. We propose that in most of the planetary nebulae studied here, the polycyclic aromatic hydrocarbons have been formed through the dissociation of the CO molecule. The hypothesis of a last thermal pulse that turns O-rich PNe into C-rich PNe is discarded, except in three objects, that show C/O > 1. We also discuss the possibility of an He pre-enrichment to explain the most He-enriched objects. We cannot discard another scenarios like extra mixing, stellar rotation or binary interactions to explain the chemical abundances behaviour observed in our sample.

Searching for reflected light from τ Bootis b with high-resolution ground-based spectroscopy: Approaching the 10-5 contrast barrier

NASA Astrophysics Data System (ADS)

Hoeijmakers, H. J.; Snellen, I. A. G.; van Terwisga, S. E.

2018-02-01

Context. It is challenging to measure the starlight reflected from exoplanets because of the extreme contrast with their host stars. For hot Jupiters, this contrast is in the range of 10-6 to 10-4, depending on their albedo, radius and orbital distance. Searches for reflected light have been performed since the first hot Jupiters were discovered, but with very limited success because hot Jupiters tend to have low albedo values due to the general absence of reflective cloud decks. Aim. The aim of this study is to search for reflected light from τ Boo b, a hot Jupiter with one of the brightest host stars. Since its discovery in 1997, it has been the subject of several reflected-light searches using high-dispersion spectroscopy. Here we aim to combine these data in to a single meta-analysis. Methods: We analysed more than 2000 archival high-dispersion spectra obtained with the UVES, ESPaDOnS, NARVAL UES and HARPS-N spectrographs during various epochs between 1998 and 2013. Each spectrum was first cleaned of the stellar spectrum and subsequently cross-correlated with a PHOENIX model spectrum. These were then Doppler shifted to the planet rest-frame and co-added in time, weighted according to the expected signal-to-noise of the planet signal. Results: We reach a 3σ upper limit of the planet-to-star contrast of 1.5 × 10-5. Assuming a planet radius of 1.15 RJ, this corresponds to an optical albedo of between 400-700 nm. A low albedo is in line with secondary eclipse and phase curve observations of other hot Jupiters using space-based observatories, as well as theoretical predictions of their reflective properties.

Cosmic dance at z 3: Detecting the host galaxies of the dual AGN system LBQS 0302-0019 and Jil with HAWK-I+GRAAL

NASA Astrophysics Data System (ADS)

Husemann, B.; Bielby, R.; Jahnke, K.; Arrigoni-Battaia, F.; Worseck, G.; Shanks, T.; Wardlow, J.; Scholtz, J.

2018-06-01

We recently discovered that the luminous radio-quiet quasi-stellar objects (QSO) LBQS 0302-0019 at z = 3.286 is likely accompanied by an obscured AGN at 20 kpc projected distance, which we dubbed Jil. It represents the tightest candidate system of an obscured and unobscured dual AGN at z > 3. To verify the dual AGN scenario, we obtained deep Ks band (rest-frame V band) imaging with the VLT/HAWK-I+GRAAL instrument at 0.″4 resolution during science verification in January 2018. We detect the individual host galaxies of the QSO and Jil with estimated stellar masses of log(M⋆/M⊙) = 11.4 ± 0.5 and log(M⋆/M⊙) = 0.9 ± 0.5, respectively. Near-IR spectra obtained with Very Large Telescope-K-band Multi Object Spectrograph (VLT-KMOS) reveal a clear [O III] λ5007 line detection at the location of Jil that does not contribute significantly to the Ks band flux. Both observations therefore corroborate the dual AGN scenario. A comparison to Illustris simulations suggests a parent halo mass of log(Mhalo/M⊙) = 13.2 ± 0.5 for this interacting galaxy system, corresponding to a massive dark matter halo at that epoch. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme(s) 60.A-9471(A) and 100.A-0134(B).

The X-shooter pipeline

NASA Astrophysics Data System (ADS)

Modigliani, Andrea; Goldoni, Paolo; Royer, Frédéric; Haigron, Regis; Guglielmi, Laurent; François, Patrick; Horrobin, Matthew; Bristow, Paul; Vernet, Joel; Moehler, Sabine; Kerber, Florian; Ballester, Pascal; Mason, Elena; Christensen, Lise

2010-07-01

The X-shooter data reduction pipeline, as part of the ESO-VLT Data Flow System, provides recipes for Paranal Science Operations, and for Data Product and Quality Control Operations at Garching headquarters. At Paranal, it is used for the quick-look data evaluation. The pipeline recipes can be executed either with EsoRex at the command line level or through the Gasgano graphical user interface. The recipes are implemented with the ESO Common Pipeline Library (CPL). X-shooter is the first of the second generation of VLT instruments. It makes possible to collect in one shot the full spectrum of the target from 300 to 2500 nm, subdivided in three arms optimised for UVB, VIS and NIR ranges, with an efficiency between 15% and 35% including the telescope and the atmosphere, and a spectral resolution varying between 3000 and 17,000. It allows observations in stare, offset modes, using the slit or an IFU, and observing sequences nodding the target along the slit. Data reduction can be performed either with a classical approach, by determining the spectral format via 2D-polynomial transformations, or with the help of a dedicated instrument physical model to gain insight on the instrument and allowing a constrained solution that depends on a few parameters with a physical meaning. In the present paper we describe the steps of data reduction necessary to fully reduce science observations in the different modes with examples on typical data calibrations and observations sequences.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wilson, T. L.; Nilsson, R.; Chen, C. H.

We have carried out two sets of observations to quantify the properties of SiO gas in the unusual HD 172555 debris disk: (1) a search for the J = 8–7 rotational transition from the vibrational ground state, carried out with the Atacama Pathfinder EXperiment (APEX) submillimeter telescope and heterodyne receiver at 863 μ m and (2) a search at 8.3 μ m for the P(17) ro-vibrational transition of gas phase SiO, carried out with the Very Large Telescope (VLT)/VISIR with a resolution, λ /Δ λ , of 30,000. The APEX measurement resulted in a 3.3 σ detection of an interstellarmore » feature, but only an upper limit to emission at the radial velocity and line width expected from HD 172555. The VLT/VISIR result was also an upper limit. These were used to provide limits for the abundance of gas phase SiO for a range of temperatures. The upper limit from our APEX detection, assuming an 8000 K primary star photospheric excitation, falls more than an order of magnitude below the self-shielding stability threshold derived by Johnson et al. (2012). Our results thus favor a solid-state origin for the 8.3 μ m feature seen in the Spitzer IRS spectrum of the circumstellar excess emission and the production of circumstellar O i and Si i by SiO UV photolysis. The implications of these estimates are explored in the framework of models of the HD 172555 circumstellar disk.« less

Performance characteristics of two volume phase holographic grisms produced for the ESPRESSO spectrograph

NASA Astrophysics Data System (ADS)

Arns, James A.

2016-08-01

The ESPRESSO spectrograph [1], a new addition to the European Southern Observatory's (ESO) Very Large Telescope (VLT), requires two volume phase holographic (VPH) grisms, one blue and the other red, splitting the overall spectral range of the instrument to maximize throughput while achieving high resolution. The blue grism covers the spectral range from 375 nm to 520 nm with a dispersion of 0.88 degrees/nm at the central wavelength of 438 nm. The red grism operates from 535 nm to 780 nm with a dispersion of 0.47 degrees/nm at 654.8 nm. Both designs use a single input prism to enhance the dispersion of the grism assembly. The grisms are relatively large in size with a working aperture of 185 mm x 185 mm for the blue grism and 215 nm x 185 mm for the red grism respectively. This paper describes the specifications of the two grating types, gives the rigorous coupled wave analysis (RCWA) theoretical performances of diffraction efficiency for the production designs and presents the measured performances of each of the delivered grisms.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalessandro, E.; Lapenna, E.; Mucciarelli, A.

We used a combination of optical and near-UV Hubble Space Telescope photometry and FLAMES/ESO-VLT high-resolution spectroscopy to characterize the stellar content of the old and massive globular cluster (GC) NGC 121 in the Small Magellanic Cloud (SMC). We report on the detection of multiple stellar populations, the first case in the SMC stellar cluster system. This result enforces the emerging scenario in which the presence of multiple stellar populations is a distinctive-feature of old and massive GCs regardless of the environment, as far as the light-element distribution is concerned. We find that second-generation (SG) stars are more centrally concentrated thanmore » first-generation (FG) ones. More interestingly, at odds with what is typically observed in Galactic GCs, we find that NGC 121 is the only cluster so far to be dominated by FG stars that account for more than 65% of the total cluster mass. In the framework where GCs were born with 90%–95% of FG stars, this observational finding would suggest that either NGC 121 experienced a milder stellar mass-loss with respect to Galactic GCs or it formed a smaller fraction of SG stars.« less

Effects of a Video Lottery Terminal (VLT) Banner on Gambling: A Field Study

ERIC Educational Resources Information Center

Gallagher, Timothy; Nicki, Richard; Otteson, Amy; Elliott, Heather

2011-01-01

The effects of a warning banner, informing patrons of the randomness of Video Lottery Terminal (VLT) outcomes, on gambling behaviour and beliefs were tested in a field setting using a mixed-model 2 x 3 design over a six-week period with 27 problem and 27 non-problem gamblers recruited from bars in a Canadian city with a population of 85,000.…

Manipulations of the features of standard video lottery terminal (VLT) games: effects in pathological and non-pathological gamblers.

PubMed

Loba, P; Stewart, S H; Klein, R M; Blackburn, J R

2001-01-01

The present study was conducted to identify game parameters that would reduce the risk of abuse of video lottery terminals (VLTs) by pathological gamblers, while exerting minimal effects on the behavior of non-pathological gamblers. Three manipulations of standard VLT game features were explored. Participants were exposed to: a counter which displayed a running total of money spent; a VLT spinning reels game where participants could no longer "stop" the reels by touching the screen; and sensory feature manipulations. In control conditions, participants were exposed to standard settings for either a spinning reels or a video poker game. Dependent variables were self-ratings of reactions to each set of parameters. A set of 2(3) x 2 x 2 (game manipulation [experimental condition(s) vs. control condition] x game [spinning reels vs. video poker] x gambler status [pathological vs. non-pathological]) repeated measures ANOVAs were conducted on all dependent variables. The findings suggest that the sensory manipulations (i.e., fast speed/sound or slow speed/no sound manipulations) produced the most robust reaction differences. Before advocating harm reduction policies such as lowering sensory features of VLT games to reduce potential harm to pathological gamblers, it is important to replicate findings in a more naturalistic setting, such as a real bar.

VLT deformable secondary mirror: integration and electromechanical tests results

NASA Astrophysics Data System (ADS)

Biasi, R.; Andrighettoni, M.; Angerer, G.; Mair, C.; Pescoller, D.; Lazzarini, P.; Anaclerio, E.; Mantegazza, M.; Gallieni, D.; Vernet, E.; Arsenault, R.; Madec, P.-Y.; Duhoux, P.; Riccardi, A.; Xompero, M.; Briguglio, R.; Manetti, M.; Morandini, M.

2012-07-01

The VLT Deformable secondary is planned to be installed on the VLT UT#4 as part of the telescope conversion into the Adaptive Optics test Facility (AOF). The adaptive unit is based on the well proven contactless, voice coil motor technology that has been already successfully implemented in the MMT, LBT and Magellan adaptive secondaries, and is considered a promising technical choice for the forthcoming ELT-generation adaptive correctors, like the E-ELT M4 and the GMT ASM. The VLT adaptive unit has been recently assembled after the completion of the manufacturing and modular test phases. In this paper, we present the most relevant aspects of the system integration and report the preliminary results of the electromechanical tests performed on the unit. This test campaign is a typical major step foreseen in all similar systems built so far: thanks to the metrology embedded in the system, that allows generating time-dependent stimuli and recording in real time the position of the controlled mirror on all actuators, typical dynamic response quality parameters like modal settling time, overshoot and following error can be acquired without employing optical measurements. In this way the system dynamic and some aspect of its thermal and long term stability can be fully characterized before starting the optical tests and calibrations.

Dual-Mission Large Aircraft Feasibility Study and Aerodynamic Investigation

NASA Technical Reports Server (NTRS)

Mavris, Dimitri

1997-01-01

A Dual-Mission Large Aircraft, or DMLA, represents the possibility of a single aircraft capable of fulfilling both a Global Reach Aircraft (GRA) and Very Large Transport (VLT) roles. The DMLA, by combining the GRA and VLT into a single new aircraft, could possibly lower the aircraft manufacturer's production costs through the resulting increase in production quantity. This translates into lower aircraft acquisition costs, a primary concern for both the Air Force and commercial airlines. This report outlines the first steps taken in this study, namely the assessment of technical and economic feasibility of the DMLA concept. In the course of this project, specialized GRA and VLT aircraft were sized for their respective missions, using baseline conventional (i.e., lacking advanced enabling technologies) aircraft models from previous work for the Air Force's Wright Laboratory and NASA-Langley. DMLA baseline aircraft were then also developed, by first sizing the aircraft for the more critical of the two missions and then analyzing the aircraft's performance over the other mission. The resulting aircraft performance values were then compared to assess technical feasibility. Finally, the life-cycle costs of each aircraft (GRA, VLT, and DMLA) were analyzed to quantify economic feasibility. These steps were applied to both a two-engine aircraft set, and a four-engine aircraft set.

Fifteen Years of Service Mode Operations: Closing the Loop with the Community

NASA Astrophysics Data System (ADS)

Primas, F.; Tacconi-Garman, L.; Marteau, S.; Mainieri, V.; Rejkuba, M.; Mysore, S.; Dumas, C.; Kaufer, A.; Patat, F.; Sterzik, M.

2014-12-01

The first Service Mode (SM) observations with the VLT were made by ISAAC in April 1999. Since then new instruments have become operational and first generation ones replaced, filling the 12 VLT foci and feeding the VLT Interferometer and its four Auxiliary Telescopes. Efficiently operating such a broad range of instruments, installed and available every night of each year, on four 8-metre telescopes offers many challenges. Although it may appear that little has changed since 1999, the underlying VLT operational model has evolved in order to accommodate different requirements from the user community and features of new instruments. As ESO and its Member States approach routine operations with ALMA, and at the same time prepare for the next challenge, the construction of the E-ELT, it seems timely to take a closer look at what SM has brought to the scientific arena, both in terms of science data and support. Did it fulfil its original goal, if so, how well, and what are the lessons learned? A careful analysis of statistics and trends in Phase 1 and Phase 2 are now being conducted in the DOME (Dashboard for Operational Metrics at ESO) project. We summarise the main findings, concentrating on the handling of Service Mode.

Relations Between Chile and ESO

NASA Astrophysics Data System (ADS)

1994-06-01

As announced in an earlier Press Release (PR 08/94 of 6 May 1994), a high-ranking ESO delegation visited Santiago de Chile during the week of 24 - 28 May 1994 to discuss various important matters of mutual interest with the Chilean Government. It consisted of Dr. Peter Creola (President of ESO Council), Dr. Catherine Cesarsky (Vice-President of ESO Council), Dr. Henrik Grage (Former Vice-President of ESO Council) and Professor Riccardo Giacconi (ESO Director General), the latter accompanied by his advisers. THE SUPPLEMENTARY TREATY BETWEEN CHILE AND ESO Following a meeting with the ambassadors to Chile of the eight ESO member countries, the ESO delegation was received by the Chilean Minister of Foreign Affairs, Mr. Carlos Figueroa, and members of his staff. The ESO delegation was pleased to receive assurances that the present Chilean Government, like its predecessors, will continue to honour all contractual agreements, in particular the privileges and immunities of this Organisation, which were laid down in the Treaty between ESO and Chile that was signed by the parties in 1963 and ratified the following year. The discussions covered some aspects of the proposed Supplementary Treaty which has been under preparation during the past year. This included in particular the desire of the Chilean side to further increase the percentage of guaranteed time for Chilean astronomers at the future ESO Very Large Telescope (VLT) and also the rules governing the installation by ESO member countries of additional telescopes at the ESO observatories in Chile. ESO invited a Chilean delegation to visit the ESO Headquarters in Garching (Germany) later this year for the final adjustment of the text of the Supplementary Treaty, after which it should be possible to proceed rapidly with the signing and ratification by the Chilean Parliament and the ESO Council. THE SITUATION AROUND PARANAL The ESO delegation expressed its deep concern to the Chilean Government about the continuing legal questioning of ESO's privileges and immunities at the designated VLT site on the Paranal mountain south of the city of Antofagasta (see ESO Press Release 07/94 of 21 April 1994), and also around the ownership of the land. ESO is now very worried about the timely completion of this 500 million DEM project. Unless a clarification of this problem is achieved as soon as possible, it is unlikely that the current plan for the construction of the VLT observatory at Paranal can be maintained. The ESO delegation expressed the opinion that these uncertainties must be removed, before the final negotiations about the above mentioned Treaty can proceed. RECEPTION BY THE PRESIDENT OF CHILE During its stay in Santiago, the ESO delegation was honoured to be received by the President of the Republic of Chile, Don Eduardo Frei Ruiz Tagle. ESO extended a warm invitation to the President to lay the cornerstone of the VLT observatory at Paranal later in 1994 at the appropriate moment. Twenty-five years ago, in 1969, the ESO La Silla observatory was inaugurated by his predecessor and father, Don Eduardo Frei Montalva. DECISIONS BY THE ESO COUNCIL The ESO delegation reported about the discussions in Santiago to the ESO Council, during its ordinary semi-annual session on June 7 - 8, 1994. The Council noted with satisfaction the clear attitude expressed by the Chilean Government, especially what concerns ESO's privileges and immunities in the host country. The ESO Council expects that the Chilean courts will also confirm these privileges and immunities. The ESO Council expressed the hope that it will now be possible to arrive at a resolution of the outstanding issues. However, in view of the increasingly tight VLT schedule - it is planned to ship the first VLT building to Paranal in the month of September this year - the Council was also much concerned about any further delays. Council requested the ESO management to ensure that the authorities of the member countries will be kept closely informed about the further developments during the coming months. The ESO Council Working Group on Relations between ESO and Chile will meet on June 29, 1994, to analyse the developments; it will report to Council immediately thereafter. Further underlining the importance of these issues for the Organisation and European Astronomy, Council resolved to meet during an extraordinary meeting on August 8 - 9, 1994. This will allow a thorough evaluation of the entire situation before ESO engages itself more fully at Paranal.

Elephant Moraine 87521: The first lunar meteorite composed of predominantly mare material

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warren, P.H.; Kallemeyn, G.W.

1989-12-01

The trace-element chemistry and detailed petrography of brecciated Antarctic meteorite EET87521 reveal that it is not, as originally classified, a eucrite. Its Fe/Mn ratio and bulk Co content are fair higher than expected for a eucrite. Only one known type of extraterrestrial material resembles EET87521 in all important respects for which constraints exist: very-low-Ti (VLT) lunar mare basalts. Even compared to VLT basalts, EET87521 is enriched in REE. However, other varieties of high-alumina, low-Ti mare basalt are known that contain REE at even higher concentrations than EET87521. Several clasts in EET87521 preserve clear vestiges of coarse-grained igneous, possibly orthocumulate, textures.more » Mineralogically, these coarse-grained clasts are diverse; e.g., olivine ranges from Fo{sub 15} in one to Fo{sub 67} in another. One clast with an anomalously fine-grained texture is anorthositic and contains exceptionally Mg-rich pyroxene and Na-poor plagioclase, along with the only FeNi-metal in the thin section. Its FeNi-metals have compositions typical of metals incorporated into lunar soils and polymict breccias as debris from metal-rich meteorites. However, the low Ni and Ir contents of our bulk-rock analysis imply that the proportion of impact-projectile matter in our chip sample is probably small. The moderate degree of lithologic diversity among the lithic lasts and the bulk composition in general indicate that EET87521 is dominated by a single rock type: VLT mare basalt.« less

First scattered light detection of a nearly edge-on transition disk around the T Tauri star RY Lupi

NASA Astrophysics Data System (ADS)

Langlois, M.; Pohl, A.; Lagrange, A.-M.; Maire, A.-L.; Mesa, D.; Boccaletti, A.; Gratton, R.; Denneulin, L.; Klahr, H.; Vigan, A.; Benisty, M.; Dominik, C.; Bonnefoy, M.; Menard, F.; Avenhaus, H.; Cheetham, A.; Van Boekel, R.; de Boer, J.; Chauvin, G.; Desidera, S.; Feldt, M.; Galicher, R.; Ginski, C.; Girard, J. H.; Henning, T.; Janson, M.; Kopytova, T.; Kral, Q.; Ligi, R.; Messina, S.; Peretti, S.; Pinte, C.; Sissa, E.; Stolker, T.; Zurlo, A.; Magnard, Y.; Blanchard, P.; Buey, T.; Suarez, M.; Cascone, E.; Moller-Nilsson, O.; Weber, L.; Petit, C.; Pragt, J.

2018-06-01

Context. Transition disks are considered sites of ongoing planet formation, and their dust and gas distributions could be signposts of embedded planets. The transition disk around the T Tauri star RY Lup has an inner dust cavity and displays a strong silicate emission feature. Aims: Using high-resolution imaging we study the disk geometry, including non-axisymmetric features, and its surface dust grain, to gain a better understanding of the disk evolutionary process. Moreover, we search for companion candidates, possibly connected to the disk. Methods: We obtained high-contrast and high angular resolution data in the near-infrared with the VLT/SPHERE extreme adaptive optics instrument whose goal is to study the planet formation by detecting and characterizing these planets and their formation environments through direct imaging. We performed polarimetric imaging of the RY Lup disk with IRDIS (at 1.6 μm), and obtained intensity images with the IRDIS dual-band imaging camera simultaneously with the IFS spectro-imager (0.9-1.3 μm). Results: We resolved for the first time the scattered light from the nearly edge-on circumstellar disk around RY Lup, at projected separations in the 100 au range. The shape of the disk and its sharp features are clearly detectable at wavelengths ranging from 0.9 to 1.6 μm. We show that the observed morphology can be interpreted as spiral arms in the disk. This interpretation is supported by in-depth numerical simulations. We also demonstrate that these features can be produced by one planet interacting with the disk. We also detect several point sources which are classified as probable background objects.

Stable and unstable accretion in the classical T Tauri stars IM Lup and RU Lup as observed by MOST

NASA Astrophysics Data System (ADS)

Siwak, Michal; Ogloza, Waldemar; Rucinski, Slavek M.; Moffat, Anthony F. J.; Matthews, Jaymie M.; Cameron, Chris; Guenther, David B.; Kuschnig, Rainer; Rowe, Jason F.; Sasselov, Dimitar; Weiss, Werner W.

2016-03-01

Results of the time variability monitoring of the two classical T Tauri stars, RU Lup and IM Lup, are presented. Three photometric data sets were utilized: (1) simultaneous (same field) MOST satellite observations over four weeks in each of the years 2012 and 2013, (2) multicolour observations at the South African Astronomical Observatory in April-May of 2013, (3) archival V-filter All Sky Automated Survey (ASAS) data for nine seasons, 2001-2009. They were augmented by an analysis of high-resolution, public-domain VLT-UT2 Ultraviolet Visual Echelle Spectrograph spectra from the years 2000 to 2012. From the MOST observations, we infer that irregular light variations of RU Lup are caused by stochastic variability of hotspots induced by unstable accretion. In contrast, the MOST light curves of IM Lup are fairly regular and modulated with a period of about 7.19-7.58 d, which is in accord with ASAS observations showing a well-defined 7.247 ± 0.026 d periodicity. We propose that this is the rotational period of IM Lup and is due to the changing visibility of two antipodal hotspots created near the stellar magnetic poles during the stable process of accretion. Re-analysis of RU Lup high-resolution spectra with the broadening function approach reveals signs of a large polar coldspot, which is fairly stable over 13 years. As the star rotates, the spot-induced depression of intensity in the broadening function profiles changes cyclically with period 3.710 58 d, which was previously found by the spectral cross-correlation method.

Discovery of a stellar companion to the nearby solar-analogue HD 104304

NASA Astrophysics Data System (ADS)

Schnupp, C.; Bergfors, C.; Brandner, W.; Daemgen, S.; Fischer, D.; Marcy, G.; Henning, Th.; Hippler, S.; Janson, M.

2010-06-01

Context. Sun-like stars are promising candidates to host exoplanets and are often included in exoplanet surveys by radial velocity (RV) and direct imaging. In this paper we report on the detection of a stellar companion to the nearby solar-analogue star HD 104304, which previously was considered to host a planetary mass or brown dwarf companion. Aims: We searched for close stellar and substellar companions around extrasolar planet host stars with high angular resolution imaging to characterize planet formation environments. Methods: The detection of the stellar companion was achieved by high angular resolution measurements, using the “Lucky Imaging” technique at the ESO NTT 3.5 m with the AstraLux Sur instrument. We combined the results with VLT/NACO archive data, where the companion could also be detected. The results were compared to precise RV measurements of HD 104304, obtained at the Lick and Keck observatories from 2001-2010. Results: We confirmed common proper motion of the binary system. A spectral type of M4V of the companion and a mass of 0.21 M_⊙ was derived. Due to comparison of the data with RV measurements of the unconfirmed planet candidate listed in the Extrasolar Planets Encyclopaedia, we suggest that the discovered companion is the origin of the RV trend and that the inclination of the orbit of i≈35°explains the relatively small RV signal. Based on observations made with ESO Telescopes at the La Silla and Paranal Observatory under programme IDs 083.C-0145 and 084.C-0812, and on data obtained from the ESO Science Archive Facility.

Youngest Brown Dwarf Yet in a Multiple Stellar System

NASA Astrophysics Data System (ADS)

2000-07-01

... and the Sharpest Optical Image (0.18 arcsec) from the VLT so far...! Astronomers are eager to better understand the formation of stars and planets - with an eye on the complex processes that lead to the emergence of our own solar system some 4600 million years ago. Brown Dwarfs (BDs) play a special role in this context. Within the cosmic zoo, they represent a class of "intermediate" objects. While they are smaller than normal stars, they shine by their own energy for a limited time, in contrast to planets. Recent observations with the ESO Very Large Telescope (VLT) of a "young" Brown Dwarf in a multiple stellar system are taking on a particular importance in this connection. An evaluation of the new data by an international team of astronomers [1] shows that it is by far the youngest of only four such objects found in a stellar system so far. The results are now providing new insights into the stellar formation process. This small object is known as TWA-5 B and with a mass of only 15 - 40 times that of Jupiter, it is near the borderline between planets and Brown Dwarfs, cf. the explanatory Appendix to this Press Release. However, visible and infrared VLT spectra unambiguously classify it in the latter category. Accurate positional measurements with the Hubble Space Telescope (HST) and the VLT hint that it is orbiting the central, much heavier and brighter star in this system, TWA-5 A (itself a close double star of which each component presumably has a mass of 0.75 solar masses), with a period that may be as long as 900 years. And, by the way, an (I-band) image of the TWA-5 system is the sharpest delivered by the VLT so far, with an image size of only 0.18 arcsec [2]! Brown Dwarfs: a cool subject In current astronomical terminology, Brown Dwarfs (BDs) are objects whose masses are below those of normal stars - the borderline is believed to be about 8% of the mass of our Sun - but larger than those of planets, cf. [3]. Unlike normal stars, Brown Dwarfs are unable to sustain stable nuclear fusion of hydrogen. Once they have been formed, they enter into a very long phase of slow contraction. This process releases (potential) energy that is emitted in the form of electromagnetic radiation. Their brightness decreases with time, as they become smaller and smaller and their energy reservoir dwindles. A few dozen "free-floating", isolated Brown Dwarfs have been discovered so far in space. They include members of the well-known, comparatively young Pleiades cluster (120 million years old) and some much older ones (some thousands of million years) only a few light-years away. A typical example is Kelu-1 that was found at ESO in 1997, see PR 07/97. However, despite extensive searches and much invested effort, astronomers have so far only found three Brown Dwarfs that have been confirmed as companions to normal stars: Gl 229 B , G196-3 B , and Gl 570 D . The younger a Brown Dwarf is, the more luminous it is, and the nearer it is to us, the brighter it appears in the sky. Old Brown Dwarfs are intrinsically so faint that, with the currently available instruments, they can only be found if they are nearby. It is therefore no surprise that the known, nearby Brown Dwarfs are generally older than the more distant ones, e.g. those found in the Pleiades. A programme to find young Brown Dwarfs It is on this background, that the international astronomer team [1] is now searching for young Brown Dwarfs that are companions to young, nearby stars. However, young stars are quite rare in the solar neighbourhood. Only a few were known before the very successful ROSAT X-ray survey that discovered about 100 young and nearby stars, less than 100 million years old and within ~ 300 light-years distance. The new research programme attempts to find brown dwarf companions to these and other young and nearby stars. For this, state-of-the-art infrared imaging cameras are used at the 3.6-m New Technology Telescope (NTT) with the SOFI (and SHARP) instrument on La Silla, as well as the 8.2-m VLT/ANTU telescope with the ISAAC multi-mode instrument at Paranal. The first step is to take high-resolution images of the stars from the ROSAT list to look for possible faint companions. However, any faint object found near one of the programme stars may of course be a completely unrelated fore- or background object and it is therefore imperative to check this by means of supplementary observations. Two methods are available. The first implies taking spectra of the companion candidates that demonstrate whether they are bona-fide Brown Dwarfs that display spectral lines typical for the cool atmospheres of this class, e.g., of Titanium Oxide (TiO) and Vanadium Oxide (VO). Infrared spectra are particularly useful for a measurement of the atmospheric temperature. The other involves obtaining a second image some years later. If the companion candidate and the brighter star belong to the same stellar system, they must move together on the sky or, as astronomers say, their measured "proper motions" must be (nearly) the same. If both checks are positive, the fainter object is most likely to be a bona-fide Brown Dwarf companion to the young and nearby star. To be absolutely certain, its orbital motion should also be detected, but it will be very slow and can only be perceived after several years of continued observations. VLT observations of TWA-5 B Two years ago, a faint companion candidate was found near one of the young and nearby stars included in the present programme and designated TWA-5 (also known as CoD -33 7795 ). It is about 12 million years old and is a member of a group of about a dozen young stars (of the "T Tauri"-type ), seen in the southern constellation Hydra (the Water-Snake) and grouped around the star TW Hya , the first to be found in this area ("TWA" means the "TW Hya Association"). The HIPPARCOS mission of the European Space Agency (ESA) measured a mean distance to some of these stars of ~ 180 light-years (55 parsec). This faint companion ( "TWA-5 B" ) was first detected in 1998 with the Hubble Space Telescope (HST) , but until now, no spectrum had been published, nor had the proper motion been measured. It is indeed a difficult object to observe: it is 100 times fainter than the bright star and is located only two arcsec away in the sky. ESO PR Photo 17a/00 ESO PR Photo 17a/00 [Preview - JPEG: 400 x 463 pix - 128k] [Normal - JPEG: 800 x 925 pix - 272k] Caption : An image of TWA-5 A (lower, bright object) and TWA-5 B (upper), taken with the FORS-2 multi-mode instrument at the 8.2-m VLT/KUEYEN telescope on 21 February 2000. The integration time was 1 second through an I-band filter (wavelength 900 nm) with the high-resolution collimator (0.1 arcsec per pixel). The image quality is 0.18 arcsec FWHM (full-width-half maximum). The lines emerging from the bright image are caused by optical reflection in the telescope. The angular distance is 2 arcsec, cf. the indicated scale. In order to investigate the nature of this object, the team obtained images and spectra with the Very Large Telescope (VLT) at Paranal. An optical image was taken by ESO staff on 21 February 2000 during a technical test period ( [4]) with the FORS-2 (FOcal Reducer/low dispersion Spectrograph) at the 8.2-m VLT/KUEYEN telescope, cf. PR Photo 17a/00 . This is actually the sharpest optical image so far taken with the VLT, with a FWHM (full-width-at-half-maximum) of only 0.18 arcsec [2] and it shows the images of the primary star ("TWA-5 A") and the 100 times fainter companion ("TWA-5 B") very well separated. An infrared image was taken on 16 April 2000 with the ISAAC (Infrared Spectrograph and Array Camera) multi-mode instrument at the 8.2-m VLT/ANTU telescope. This image was obtained by ESO staff in service mode and again, TWA-5 A and B are both clearly seen. More recently, spectra of TWA-5 B were taken with FORS-2 (optical wavelength region) and ISAAC (infrared). These observations were particularly difficult, because of the need to avoid contamination from the strong light of the much brighter object, only 2 arcsec away. The nature of TWA-5 B ESO PR Photo 17b/00 ESO PR Photo 17b/00 [Preview - JPEG: 509 x 400 pix - 124k] [Normal - JPEG: 1017 x 800 pix - 264k] Caption : This optical spectrum (600 - 900 nm wavelength range) of TWA-5 B was obtained with the FORS-2 instrument at the 8.2-m VLT/KUEYEN telescope on 23 February 2000. A 30-min exposure was made through a 0.7 arcsec wide slit, positioned on the object in east-west direction, i.e., perpendicular to the direction to the much brighter TWA-5 A , only 2 arcsec to the south, see PR Photo 17a/00. Thanks to this, the obtained spectrum was very "clean". Also shown is the optical spectrum of a typical M9-type star. The spectra are very similar, with broad molecular absorption bands from TiO and VO. TWA-5 B also shows strong hydrogen emission (H-alpha) and weak sodium (Na) absorption, both indicative of its comparatively young age. ESO PR Photo 17c/00 ESO PR Photo 17c/00 [Preview - JPEG: 515 x 400 pix - 124k] [Normal - JPEG: 1030 x 800 pix - 284k] Caption : This infrared spectrum was obtained on 16 April 2000 with the ISAAC multi-mode instrument at the 8.2-m VLT/ANTU telescope in the 1.4 - 1.8 µm wavelength range (the H-band), with spectral resolution 500. It corresponds to a total exposure time of 20 min and was made through a 0.6 arcsec wide slit. Lines of Magnesium (Mg), Carbon Monoxide (CO), and the Hydroxyl radical (OH) are identified. The general shape of the spectrum is typical of that of a late M-type dwarf star. For comparison, the infrared spectrum of an M9-type star is shown. The spectra are indeed quite similar. The optical spectrum of TWA-5 B shows strong molecular absorption features (TiO and VO, cf. PR Photo 17b/00 ), typical for very cold stellar atmospheres and confirming it as a Brown Dwarf. Both the optical and the infrared ( PR Photo 17c/00 ) spectra indicate a late spectral type (about M9) of TWA-5 B that corresponds to an atmospheric temperature of "only" ~2200 °C (2500 K). For comparison, that of the Sun is ~ 6000 °C. The hydrogen (H-alpha) emission line indicates strong activity in the upper atmospheric layers (the chromosphere), as normally found in young stars and young Brown Dwarfs. Moreover, the comparatively weak sodium (Na) absorption line shows that this object must be relatively large for its low mass, and that it is still in the early stage of contraction. These are clear signs of young age and fully consistent with TWA-5 B being a bona-fide companion to the young star TWA-5 A . In fact, the possibility that an object as cold as TWA-5 B is located within 2 arcsec from TWA-5 A by chance is less than 10 -8. The motion of TWA-5 B ESO PR Photo 17d/00 ESO PR Photo 17d/00 [Preview - JPEG: 400 x 463 pix - 64k] [Normal - JPEG: 800 x 925 pix - 140k] Caption : The diagramme shows the relative positions of TWA-5 A and TWA-5 B , as measured on the sky by the HST in 1998 (points 1 and 2) and the VLT in 2000 (3 and 4). The ellipses indicate the measurement uncertainties. It is obvious that the two objects move in nearly the same direction and with the same speed. This greatly strengthens the conclusion that they are physically connected in the same multiple stellar system. When comparing the HST positional observations from 1998 and those with the VLT in 2000 ( PR Photo 17d/00 ), it is obvious that TWA-5 A and TWA-5 B move with very nearly the same speed and in the same direction on the sky. There is therefore no doubt that the two objects are physically connected within a stellar multiple system. At the distance of about 180 light-years, the angular separation (2 arcsec) corresponds to a projected distance of 110 AU (about 2.75 times the mean distance between the Sun and the outermost planet in the solar system, Pluto). From this and the mass of TWA-5 A , it is possible to conclude that one full orbit of TWA-5 B around TWA-5 A will last about 900 years. Mass, temperature and age of TWA-5 From the measured optical and infrared brightness of TWA-5 B and the known distance, it is found to be about 400 times fainter than our Sun. Together with the measured temperature, about 2200 °C, and based on theoretical models of Brown Dwarfs, a mass of about 15 to 40 Jupiter masses is deduced. It is also possible to estimate its age; it is found to be very similar as that of TWA-5 A (12 million years), further supporting the conclusion that they were formed at the same time and belong to the same stellar system. TWA-5 B is only the fourth Brown Dwarf so far confirmed as a companion to a normal star , both by spectroscopic and proper motion measurements. It is unique among these by being by far the youngest (12 million years). The others are much older; one is nearly 300 million years old and the other two are several thousand million years old. Indeed, TWA-5 A and its Brown Dwarf companion TWA-5 B are still in the process of formation . The system is the only one so far discovered at this early evolutionary stage. These new findings thus have a direct bearing on the question how Brown Dwarfs form as companions to normal stars. The next steps More detailed investigations of this unique object are now planned. They will include an attempt to detect absorption lines of other elements that are typical for brown dwarfs (especially of lithium) by means of higher-resolution spectra, as well as further imaging that may lead to a detection of the orbital motion within a few years. The team is also actively searching for other very low-mass companions in order to cast more light on some of the fundamental questions, e.g.: What is the mass range of Brown Dwarfs ? What are their orbital characteristics ? Can stars of all masses have Brown Dwarf companions ? Are the distributions of the masses of isolated and companion brown dwarfs similar or different ? Not less exciting, the same observational method can also be used to search for companions of even lower mass, in particular planets. Until now, no extra-solar planets have been detected directly, but only indirectly by other methods, cf. ESO PR 13/00. For this, "deep" images of young nearby stars and their immediate surroundings must be obtained. Young planets are also still relatively hot and, hence, relatively bright, but they are many times fainter than TWA-5 B , hence the need for long exposures. However, such observations are extremely difficult, as any planet - even a young and relatively massive and bright one - will be much fainter than the star around which it revolves and is located very close to it in the sky. One observational method that helps overcome this fundamental obstacle is already used by the team. It consists of taking a very large number (hundreds or even thousands) of very short exposures (1 second or less) and then to add them up using computers (the "speckle method") and suppressing the image blur caused by atmospheric turbulence. In this way, even very faint companions may be detected near bright stars. This will work even better with adaptive optics , e.g. with the CONICA-NAOS instrument that will soon be installed at the third VLT Unit Telescope, MELIPAL. When will the first image of an exoplanet be obtained? This kind of research is very exciting, but also demands great care. A recent event illustrates this. Just a few months ago, the present astronomer team detected a companion candidate to another young star on their list ( TWA-7 ). This object was 100,000 times fainter than and only 2.5 arcsec away from TWA-7 . If it were a true companion orbiting TWA-7 , its mass would have been only 3 Jupiter masses (as deduced from the observed brightness) and it would thus very likely have been a true exoplanet. However, an infrared spectrum subsequently taken with the ISAAC instrument at VLT/ANTU showed that it was in fact a background star, located almost 10,000 light-years farther away than TWA-7 ! Despite the negative result, those observations clearly showed that direct detection and subsequent, effective spectroscopic verification of extra-solar planets is now quite feasible with a ground-based facility like the VLT. It is thus not a very daring prediction that the ongoing searches may soon lead to the first direct images of an extra-solar planet. These are indeed exciting times! More information The work described in this Press Release is discussed by the team in a research article that has been accepted for publication in the European journal Astronomy & Astrophysics. Another paper ( "Direct imaging search for planetary companions next to young nearby stars" ) is also available with more details about the current searches, including the spectrum of the background star at TWA-7. The Principal Investigator for this project may be contacted at: Ralph Neuhaeuser Max-Planck-Institut für Extraterrestrische Physik D-85748 Garching Germany Phone +49-89-32993398 email: rne@mpe.mpg.de Notes [1]: The team consists of Ralph Neuhaeuser (Principal Investigator) and Nuria Huelamo (both Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany), Eike Guenther (Landessternwarte Tautenburg, Germany), Monika Petr (Max-Planck-Institut für Radioastronomie, Bonn, Germany), Wolfgang Brandner (Institute for Astronomy, Honolulu, Hawaii, USA) and João Alves (ESO, Garching, Germany). [2]: The hitherto sharpest image (0.25 arcsec) was obtained in March 1999, cf. ESO PR 06/99. It was obtained during a period of exceptionally good "seeing" (low level of atmospheric turbulence). The installation of adaptive optics at the VLT, foreseen in 2001, will provide a means to overcome the image smearing effect of air turbulence and hence, consistently obtain stellar images of a few hundredths of an arcsecond diameter, near the theoretical limit for an 8.2-m telescope (the telescope diffraction limit ). [3]: 1 solar mass = 2 x 10 30 kg. 1 Jupiter mass = 2 x 10 27 kg ~ 0.001 solar mass. Thus, the "BD-limit" of 0.08 solar masses corresponds to ~ 80 Jupiter masses. [4]: This CCD frame was taken by Paranal Observatory staff during the one of the KUEYEN/FORS-2 "dry runs" in a "technical period", i.e. test observations that served to practise and perfect the operation of the telescope and instrument, before it was made available to the community on April 1, 2000. These and many similar data from this period were quickly released to the community and are available in the publicly accessible area of the VLT Data Archive. Appendix: Planets and Brown Dwarfs Planets and Brown Dwarfs mainly differ by the way they form. While it is believed that Brown Dwarfs (both as companions to normal stars and as isolated objects) form as do normal low-mass stars by fragmentation and subsequent contraction in interstellar gas clouds , planets form in circumstellar gas- and dust disks around their central star. However, an exact dividing line in terms of mass cannot yet be drawn between planets and brown dwarfs, neither from theory nor from observation. It appears that the lower mass limit for Brown Dwarfs is around 0.01 solar masses (about 10 Jupiter masses) and that the upper mass limit for planets is also near this value. Further observations and theoretical progress are needed to clarify this question. Below this mass limit (~ 0.01 solar masses), an object cannot burn the hydrogen isotope deuterium . Planets will therefore have more deuterium in their atmospheres than Brown Dwarfs. One way to distinguish observationally between a planet and a Brown Dwarf is therefore to search for absorption lines of deuterium in the spectrum of the object. These lines would be much stronger in a planet than in a Brown Dwarf. However, such observations would require very high spectral resolution in the infrared region. At this moment, no corresponding observational facilities exist, but it will most probably be possible with the VLT High-Resolution IR Echelle Spectrometer (CRIRES) , currently under development for installation at VLT/ANTU in 2003. The dividing line between real stars on one side and Brown Dwarfs and planets on the other side is better known. Any object that weighs less than ~ 0.08 solar masses cannot sustain stable fusion of hydrogen and also cannot burn the light element lithium.

VISIR upgrade overview: all's well that ends well

NASA Astrophysics Data System (ADS)

Kerber, Florian; Käufl, Hans Ulrich; Tristram, Konrad; Asmus, Daniel; Baksai, Pedro; Di Lieto, Nicola; Dobrzycka, Danuta; Duhoux, Philippe; Finger, Gert; Hummel, Christian; Ives, Derek; Jakob, Gerd; Lundin, Lars; Mawet, Dimitri; Mehrgan, Leander; Pantin, Eric; Riquelme, Miguel; Sanchez, Joel; Sandrock, Stefan; Siebenmorgen, Ralf; Stegmeier, Jörg; Smette, Alain; Taylor, Julian; van den Ancker, Mario; Valdes, Guillermo; Venema, Lars

2016-08-01

We present an overview of the VISIR instrument after its upgrade and return to science operations. VISIR is the midinfrared imager and spectrograph at ESO's VLT. The project team is comprised of ESO staff and members of the original VISIR consortium: CEA Saclay and ASTRON. The project plan was based on input from the ESO user community with the goal of enhancing the scientific performance and efficiency of VISIR by a combination of measures: installation of improved hardware, optimization of instrument operations and software support. The cornerstone of the upgrade is the 1k by 1k Si:As AQUARIUS detector array manufactured by Raytheon. In addition, a new prism spectroscopic mode covers the whole N-band in a single observation. Finally, new scientific capabilities for high resolution and high-contrast imaging are offered by sub-aperture mask and coronagraphic modes. In order to make optimal use of favourable atmospheric conditions, a water vapour monitor has been deployed on Paranal, allowing for real-time decisions and the introduction of a user-defined constraint on water vapour. During the commissioning in 2012, it was found that the on-sky sensitivity of the AQUARIUS detector was significantly below expectations. Extensive testing of the detector arrays in the laboratory and on-sky enabled us to diagnose the cause for the shortcoming of the detector as excess low frequency noise. It is inherent to the design chosen for this detector and cannot be remedied by changing the detector set-up. Since this is a form of correlated noise, its impact can be limited by modulating the scene recorded by the detector. After careful analysis, we have implemented fast (up to 4 Hz) chopping with field stabilization using the secondary mirror of the VLT. During commissioning, the upgraded VISIR has been confirmed to be more sensitive than the old instrument, and in particular for low-resolution spectroscopy in the N-band, a gain of a factor 6 is realized in observing efficiency. After overcoming several additional technical problems, VISIR is back in Science Operations since April 2015. In addition an upgrade of the IT infrastructure related to VISIR has been conducted in order to support burst-mode operations. Science Verification of the new modes was performed in Feb 2016. The upgraded VISIR is a powerful instrument providing close to background limited performance for diffraction-limited observations at an 8-m telescope. It offers synergies with facilities such as ALMA, JWST, VLTI and SOFIA, while a wealth of targets is available from survey works like WISE. In addition, it will bring confirmation of the technical readiness and scientific value of several aspects for future mid-IR instrumentation at Extremely Large Telescopes. We also present several lessons learned during the project.

Evaluation Data of a High Temperature COTS Flash Memory Module (TI SM28VLT32) for Use in Geothermal Electronics Packages

DOE Data Explorer

Cashion, Avery

2014-08-29

The accompanying raw data is composslection. Each file is 3 columns and tab-delimited with the first column being the data address, the second column being the first byte of the data, and the third column being the second byte of the data.

MAXI J1820+070: VLT and GTC spectroscopic follow-up shows a significant spectral evolution from the early stages of the outburst

NASA Astrophysics Data System (ADS)

Munoz-Darias, T.; Jimenez-Ibarra, F.; Padilla, M. Armas; Casares, J.; Torres, M. A. P.

2018-03-01

The detection of the new black hole candidate MAXI J1807+132 has triggered a worldwide follow-up campaign from high energies to radio wavelengths (ATel #11400, #11403, #11418, #11421, #11423, #11424, #11425, #11426, #11427, #11432, #11437, #11439, #11440, #11445, #11451, #11458 and #11458).

Tracing the evolution of the Galactic bulge with chemodynamical modelling of alpha-elements

NASA Astrophysics Data System (ADS)

Friaça, A. C. S.; Barbuy, B.

2017-02-01

Context. Galactic bulge abundances can be best understood as indicators of bulge formation and nucleosynthesis processes by comparing them with chemo-dynamical evolution models. Aims: The aim of this work is to study the abundances of alpha-elements in the Galactic bulge, including a revision of the oxygen abundance in a sample of 56 bulge red giants. Methods: Literature abundances for O, Mg, Si, Ca and Ti in Galactic bulge stars are compared with chemical evolution models. For oxygen in particular, we reanalysed high-resolution spectra obtained using FLAMES+UVES on the Very Large Telescope, now taking each star's carbon abundances, derived from CI and C2 lines, into account simultaneously. Results: We present a chemical evolution model of alpha-element enrichment in a massive spheroid that represents a typical classical bulge evolution. The code includes multi-zone chemical evolution coupled with hydrodynamics of the gas. Comparisons between the model predictions and the abundance data suggest a typical bulge formation timescale of 1-2 Gyr. The main constraint on the bulge evolution is provided by the O data from analyses that have taken the C abundance and dissociative equilibrium into account. Mg, Si, Ca and Ti trends are well reproduced, whereas the level of overabundance critically depends on the adopted nucleosynthesis prescriptions. Observations collected both at the European Southern Observatory, Paranal, Chile (ESO programmes 71.B-0617A, 73.B0074A, and GTO 71.B-0196)

Chemical study of the metal-rich globular cluster NGC 5927

NASA Astrophysics Data System (ADS)

Mura-Guzmán, A.; Villanova, S.; Muñoz, C.; Tang, B.

2018-03-01

Globular clusters (GCs) are natural laboratories where stellar and chemical evolution can be studied in detail. In addition, their chemical patterns and kinematics can tell us to which Galactic structure (disc, bulge, halo or extragalactic) the cluster belongs to. NGC 5927 is one of most metal-rich GCs in the Galaxy and its kinematics links it to the thick disc. We present abundance analysis based on high-resolution spectra of seven giant stars. The data were obtained using Fibre Large Array Multi Element Spectrograph/Ultraviolet Echelle Spectrograph (UVES) spectrograph mounted on UT2 telescope of the European Southern Observatory. The principal objective of this work is to perform a wide and detailed chemical abundance analysis of the cluster and look for possible Multiple Populations (MPs). We determined stellar parameters and measured 22 elements corresponding to light (Na, Al), alpha (O, Mg, Si, Ca, Ti), iron-peak (Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and heavy elements (Y, Zr, Ba, Ce, Nd, Eu). We found a mean iron content of [Fe/H] = -0.47 ± 0.02 (error on the mean). We confirm the existence of MPs in this GC with an O-Na anti-correlation, and moderate spread in Al abundances. We estimate a mean [α/Fe] = 0.25 ± 0.08. Iron-peak elements show no significant spread. The [Ba/Eu] ratios indicate a predominant contribution from SNeII for the formation of the cluster.

THREE DISCRETE GROUPS WITH HOMOGENEOUS CHEMISTRY ALONG THE RED GIANT BRANCH IN THE GLOBULAR CLUSTER NGC 2808

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carretta, E., E-mail: eugenio.carretta@oabo.inaf.it

2014-11-10

We present the homogeneous reanalysis of Mg and Al abundances from high resolution UVES/FLAMES spectra for 31 red giants in the globular cluster NGC 2808. We found a well defined Mg-Al anticorrelation reaching a regime of subsolar Mg abundance ratios, with a spread of about 1.4 dex in [Al/Fe]. The main result from the improved statistics of our sample is that the distribution of stars is not continuous along the anticorrelation because they are neatly clustered into three distinct clumps, each with different chemical compositions. One group (P) shows a primordial composition of field stars of similar metallicity, and the other twomore » (I and E) have increasing abundances of Al and decreasing abundances of Mg. The fraction of stars we found in the three components (P: 68%, I: 19%, E: 13%) is in excellent agreement with the ratios computed for the three distinct main sequences in NGC 2808: for the first time there is a clear correspondence between discrete photometric sequences of dwarfs and distinct groups of giants with homogeneous chemistry. The composition of the I group cannot be reproduced by mixing of matter with extreme processing in hot H-burning and gas with pristine, unprocessed composition, as also found in the recent analysis of three discrete groups in NGC 6752. This finding suggests that different classes of polluters were probably at work in NGC 2808 as well.« less

ESO Council Decides to Continue VLT Project at Paranal

NASA Astrophysics Data System (ADS)

1994-08-01

The Council [1] of the European Southern Observatory has met in extraordinary session at the ESO Headquarters in Garching near Munich on August 8 and 9, 1994. The main agenda items were concerned with the recent developments around ESO's relations with the host state, the Republic of Chile, as well as the status of the organisation's main project, the 16-metre equivalent Very Large Telescope (VLT) which will become the world's largest optical telescope. Council had decided to hold this special meeting [2] because of various uncertainties that have arisen in connection with the implementation of the VLT Project at Cerro Paranal, approx. 130 kilometres south of Antofagasta, capital of the II Region in Chile. Following continued consultations at different levels within the ESO member states and after careful consideration of all aspects of the current situation - including various supportive actions by the Chilean Government as well as the incessive attacks against this international organisation from certain sides reported in the media in that country - Council took the important decision to continue the construction of the VLT Observatory at Paranal, while at the same time requesting the ESO Management to pursue the ongoing studies of alternative solutions. THE COUNCIL DECISIONS In particular, the ESO Council took note of recent positive developments which have occurred since the May 1994 round of discussions with the Chilean authorities in Santiago. The confirmation of ESO's immunities as an International Organization in Chile, contained in a number of important statements and documents, is considered a significant step by the Chilean Government to insure to ESO the unhindered erection and later operation of the VLT on Paranal. Under these circumstances and in order to maintain progress on the VLT project, the ESO Council authorized the ESO Management to continue the on-site work at Paranal. Council also took note of the desire expressed by the Chilean Government to complete negotiation of a Supplementary and Amending Agreement and it was decided that a Council Delegation shall conclude as soon as possible the negotiation of this Agreement. Council noted that the Chilean Delegation has accepted ESO's invitation to hold the final round of negotiations in Europe and proposed that this final round shall be held in the period Sept. 15 - Oct. 15, 1994. Nonetheless, Council also expressed its preoccupation with regard to remaining ambiguities contained in some official statements according to which the formal recognition of ESO's status on Paranal would depend on the conclusion of the above mentioned Agreement. At the May 1994 meetings in Santiago [2], understanding had been reached that this Agreement will merely confirm the already existing legal situation. The main objective is to expand the cooperation between Chile and ESO by granting ensured access for Chilean astronomers to ESO's facilities and incorporate elements of Chilean labour legislation into the ESO internal staff regulations. In view of these circumstances, and pending the successful conclusion of these negotiations, Council therefore instructed the ESO Management to continue exploring alternative sites for the VLT. In a final statement, the ESO Council again expressed its hope that the scientific co-operation between Europe and Chile in the field of astronomy which began in 1963 will continue to develop and expand well into the next century to the mutual benefit of science in both communities. CONTINUATION OF THE VLT PROJECT In practical terms, the above decision by Council implies that ESO will now initiate the steps necessary to move from Europe to Paranal the main mechanical parts of the rotating dome (total weight around 500 tonnes) for the first VLT 8.2-metre unit telescope. It is expected that the sea transport will take place in September-October of this year and that assembly at Paranal will begin soon thereafter, once the concrete base, now under construction, is ready. This will enable the 500 million DEM VLT Project to stay within the planned timeline for completion just after the year 2000. 1. The Council of ESO consists of two representatives from each of the eight member states. It is the highest authority of the organisation and normally meets twice a year. 2. See ESO Press Release 12/94 of June 10, 1994.

Two VLT 8.2-m Unit Telescopes in Action

NASA Astrophysics Data System (ADS)

1999-04-01

Visitors at ANTU - Astronomical Images from KUEYEN The VLT Control Room at the Paranal Observatory is becoming a busy place indeed. From here, two specialist teams of ESO astronomers and engineers now operate two VLT 8.2-m Unit Telescopes in parallel, ANTU and KUEYEN (formerly UT1 and UT2, for more information about the naming and the pronunciation, see ESO Press Release 06/99 ). Regular science observations have just started with the first of these giant telescopes, while impressive astronomical images are being obtained with the second. The work is hard, but the mood in the control room is good. Insiders claim that there have even been occasions on which the groups have had a friendly "competition" about which telescope makes the "best" images! The ANTU-team has worked with the FORS multi-mode instrument , their colleagues at KUEYEN use the VLT Test Camera for the ongoing tests of this new telescope. While the first is a highly developed astronomical instrument with a large-field CCD imager (6.8 x 6.8 arcmin 2 in the normal mode; 3.4 x 3.4 arcmin 2 in the high-resolution mode), the other is a less complex CCD camera with a smaller field (1.5 x 1.5 arcmin 2 ), suited to verify the optical performance of the telescope. As these images demonstrate, the performance of the second VLT Unit Telescope is steadily improving and it may not be too long before its optical quality will approach that of the first. First KUEYEN photos of stars and galaxies We present here some of the first astronomical images, taken with the second telescope, KUEYEN, in late March and early April 1999. They reflect the current status of the optical, electronic and mechanical systems, still in the process of being tuned. As expected, the experience gained from ANTU last year has turned out to be invaluable and has allowed good progress during this extremely delicate process. ESO PR Photo 19a/99 ESO PR Photo 19a/99 [Preview - JPEG: 400 x 433 pix - 160k] [Normal - JPEG: 800 x 866 pix - 457k] [High-Res - JPEG: 1985 x 2148 pix - 2.0M] ESO PR Photo 19b/99 ESO PR Photo 19b/99 [Preview - JPEG: 400 x 478 pix - 165k] [Normal - JPEG: 800 x 956 pix - 594k] [High-Res - JPEG: 3000 x 3583 pix - 7.1M] Caption to PR Photo 19a/99 : This photo was obtained with VLT KUEYEN on April 4, 1999. It is reproduced from an excellent 60-second R(ed)-band exposure of the innermost region of a globular cluster, Messier 68 (NGC 4590) , in the southern constellation Hydra (The Water-Snake). The distance to this 8-mag cluster is about 35,000 light years, and the diameter is about 140 light-years. The excellent image quality is 0.38 arcsec , demonstrating a good optical and mechanical state of the telescope, already at this early stage of the commissioning phase. The field measures about 90 x 90 arcsec 2. The original scale is 0.0455 pix/arcsec and there are 2048x2048 pixels in one frame. North is up and East is left. Caption to PR Photo 19b/99 : This photo shows the central region of spiral galaxy ESO 269-57 , located in the southern constellation Centaurus at a distance of about 150 million light-years. Many galaxies are seen in this direction at about the same distance, forming a loose cluster; there are also some fainter, more distant ones in the background. The designation refers to the ESO/Uppsala Survey of the Southern Sky in the 1970's during which over 15,000 southern galaxies were catalogued. ESO 269-57 is a tightly bound object of type Sar , the "r" referring to the "ring" that surrounds the bright centre, that is overexposed here. The photo is a composite, based on three exposures (Blue - 600 sec; Yellow-Green - 300 sec; Red - 300 sec) obtained with KUEYEN on March 28, 1999. The image quality is 0.7 arcsec and the field is 90 x 90 arcsec 2. North is up and East is left. ESO PR Photo 19c/99 ESO PR Photo 19c/99 [Preview - JPEG: 400 x 478 pix - 132k] [Normal - JPEG: 800 x 956 pix - 446k] [High-Res - JPEG: 3000 x 3583 pix - 4.6M] ESO PR Photo 19d/99 ESO PR Photo 19d/99 [Preview - JPEG: 400 x 454 pix - 86k] [Normal - JPEG: 800 x 907 pix - 301k] [High-Res - JPEG: 978 x 1109 pix - 282k] Caption to PR Photo 19c/99 : Somewhat further out in space, and right on the border between the southern constellations Hydra and Centaurus lies this knotty spiral galaxy, IC 4248 ; the distance is about 210 million light-years. It was imaged with KUEYEN on March 28, 1999, with the same filters and exposure times as used for Photo 19b/99. The image quality is 0.75 arcsec and the field is 90 x 90 arcsec 2. North is up and East is left. Caption to PR Photo 19d/99 : This is a close-up view of the double galaxy NGC 5090 (right) and NGC 5091 (left), in the southern constellation Centaurus. The first is a typical S0 galaxy with a bright diffuse centre, surrounded by a fainter envelope of stars (not resolved in this picture). However, some of the starlike objects seen in this region may be globular clusters (or dwarf galaxies) in orbit around NGC 5090. The other galaxy is of type Sa (the spiral structure is more developed) and is seen at a steep angle. The three-colour composite is based on frames obtained with KUEYEN on March 29, 1999, with the same filters and exposure times as used for Photo 19b/99. The image quality is 0.7 arcsec and the field is 90 x 90 arcsec 2. North is up and East is left. ( Note inserted on April 26: The original caption text identified the second galaxy as NGC 5090B - this error has now been corrected. ESO PR Photo 19e/99 ESO PR Photo 19e/99 [Preview - JPEG: 400 x 441 pix - 282k] [Normal - JPEG: 800 x 882 pix - 966k] [High-Res - JPEG: 3000 x 3307 pix - 6,4M] Caption to PR Photo 19e/99 : Wide-angle photo of the second 8.2-m VLT Unit Telescope, KUEYEN , obtained on March 10, 1999, with the main mirror and its cell in place at the bottom of the telescope structure. The Test Camera with which the astronomical images above were made, is positioned at the Cassegrain focus, inside this mirror cell. The Paranal Inauguration on March 5, 1999, took place under this telescope that was tilted towards the horizon to accommodate nearly 300 persons on the observing floor. Astronomical observations with ANTU have started On April 1, 1999, the first 8.2-m VLT Unit Telescope, ANTU , was "handed over" to the astronomers. Last year, about 270 observing proposals competed about the first, precious observing time at Europe's largest optical telescope and more than 100 of these were accommodated within the six-month period until the end of September 1999. The complete observing schedule is available on the web. These observations will be carried out in two different modes. During the Visitor Mode , the astronomers will be present at the telescope, while in the Service Mode , ESO observers perform the observations. The latter procedure allows a greater degree of flexibility and the possibility to assign periods of particularly good observing conditions to programmes whose success is critically dependent on this. The first ten nights at ANTU were allocated to service mode observations. After some initial technical problems with the instruments, these have now started. Already in the first night, programmes at ISAAC requiring 0.4 arcsec conditions could be satisfied, and some images better than 0.3 arcsec were obtained in the near-infrared . The first astronomers to use the telescope in visitors mode will be Professors Immo Appenzeller (Heidelberg, Germany; "Photo-polarimetry of pulsars") and George Miley (Leiden, The Netherlands; "Distant radio galaxies") with their respective team colleagues. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory. Note also the dedicated webarea with VLT Information.

Report on the ''2017 ESO Calibration Workshop: The Second-Generation VLT Instruments and Friends''

NASA Astrophysics Data System (ADS)

Smette, A.; Kerber, F.; Kaufer, A.

2017-03-01

The participants at the 2017 ESO Calibration Workshop shared their experiences and the challenges encountered in calibrating VLT second-generation instruments and the upgraded first-generation instruments, and discussed improvements in the characterisation of the atmosphere and data reduction. A small group of ESO participants held a follow-up retreat and identified possible game changers in the future operations of the La Silla Paranal Observatory: feedback on the proposals is encouraged.

VST project: distributed control system overview

NASA Astrophysics Data System (ADS)

Mancini, Dario; Mazzola, Germana; Molfese, C.; Schipani, Pietro; Brescia, Massimo; Marty, Laurent; Rossi, Emilio

2003-02-01

The VLT Survey Telescope (VST) is a co-operative program between the European Southern Observatory (ESO) and the INAF Capodimonte Astronomical Observatory (OAC), Naples, for the study, design, and realization of a 2.6-m wide-field optical imaging telescope to be operated at the Paranal Observatory, Chile. The telescope design, manufacturing and integration are responsibility of OAC. The VST has been specifically designed to carry out stand-alone observations in the UV to I spectral range and to supply target databases for the ESO Very Large Telescope (VLT). The control hardware is based on a large utilization of distributed embedded specialized controllers specifically designed, prototyped and manufactured by the Technology Working Group for VST project. The use of a field bus improves the whole system reliability in terms of high level flexibility, control speed and allow to reduce drastically the plant distribution in the instrument. The paper describes the philosophy and the architecture of the VST control HW with particular reference to the advantages of this distributed solution for the VST project.

Design and performance of the VLT 8-m coating unit

NASA Astrophysics Data System (ADS)

Schneermann, Michael W.; Groessl, M.; Nienaber, U.; Ettlinger, E.; Spiteri, J. A.; Clow, H.

1997-03-01

The 8 m coating unit for the VLT mirrors is designed for the deposition of high reflective, homogeneous aluminum coatings. For the process of the film deposition the sputter technology is utilized. The design of the following major subsystems is completed: the vacuum vessel and the vacuum generation system, the thin film deposition equipment and the glow discharge cleaning device, the substrate support and rotation system as well as the supporting framework and the auxiliary equipment. Manufacturing of the coating unit has started. The pre- assembly and testing activities, which will take place prior to the shipment to the site, are defined. This paper describes the design features and the major performance requirements of the 8 m coating unit. The performance of the sputter source design has been verified in a qualification test. The deposition rate, the film thickness and reflectance, as well as the film purity have been measured. The test set-up and the results of the qualification tests of the selected magnetron type are presented and discussed.

Hot molecular hydrogen in the central parsec of the Galaxy through near-infrared 3D fitting

NASA Astrophysics Data System (ADS)

Ciurlo, A.; Paumard, T.; Rouan, D.; Clénet, Y.

2016-10-01

Aims: We have investigated neutral gas in the central cavity of the circumnuclear disk (CND) at the Galactic center, where the ionized minispiral lies, to describe the H2 distribution and properties in this ionized environment. Methods: This study was carried out through a spectro-imaging data cube of the central cavity obtained with SPIFFI on the VLT. The observed field of view is 36″ × 29″, with a spectral resolution R = 1300 in the near-infrared. These observations cover several H2 lines. To preserve the spatial resolution and avoid edge effects, we applied a new line-fitting method that consists of a regularized 3D fitting. We also applied a more classical 1D fitting to compare the relative strength of the H2 lines. Results: We present high spatial and spectral resolution maps of the intensity, velocity, and width of five H2 lines and an extinction map derived from H2. Molecular gas is detected everywhere in the field. In particular, in addition to the known CND features, we detected an emission from the northern arm cloud and from the minicavity. The excitation diagrams allow us to estimate the temperature, mass, and density of these features. Conclusions: We interpret the CND emission as coming from a hot, thermalized, thin layer at the surface of the clouds. The observed H2 corresponds only to a small fraction of the total H2 mass. The emission remains fairly strong in the whole central cavity, but it is not thermalized. A strong deviation from thermal equilibrium is detected near the minicavity. We suggest that this emission is caused by constantly forming H2 that is destroyed again before it reaches ortho/para equilibrium.

VizieR Online Data Catalog: Large spectrosc. survey of Palomar 5 stellar stream (Ibata+, 2017)

NASA Astrophysics Data System (ADS)

Ibata, R. A.; Lewis, G. F.; Thomas, G.; Martin, N. F.; Chapman, S.

2018-02-01

The present contribution builds upon the survey of Paper I (Ibata+, 2016,J/ApJ/819/1). In addition to the deep CFHT photometry, in Paper I we also presented shallower KPNO photometry of this system using the M-band filter (approximately V) and the intermediate-band "DDO 51" filter (central wavelength 5145.2Å, FWHM=162.9Å) which covers the Mg b triplet. Here we present a large spectroscopic survey of the stellar stream. On 2009 June 23-27, we used the FLAMES multiobject spectrograph on the 8m VLT to observe 35 fields along the Palomar 5 stellar stream. The high-resolution setting HR21 was used, which straddles the CaII triplet feature and covers the spectral region between 8484Å and 9001Å with a resolution of R=16200. Each field consisted of 3x600s exposures. The FLAMES fields are fully contained within the CFHT survey region (see Figure 1), and yielded a total of 1327 stars. We also observed 15 fields with the AAOmega multiobject spectrograph at the 4m Australian Astronomical Telescope on the nights of 2006 June 13-18. The 1700D grating was used to measure the spectral region between ~8400Å and ~8850Å, at a resolution of 0.24Å/pixel. In each field, three exposures of 1800s were combined. Selecting good quality stars from both data sets (S/N>40 for FLAMES, S/N>30 for AAOmega), we obtain 45 stars in common. The velocity difference between the two samples is vFLAMES-vAAO=3.73+/-1.89km/s, and we used this mean offset to put the AAO velocities onto the FLAMES zero point. (1 data file).

VizieR Online Data Catalog: NGC1068 interferometric mid-IR measurements (Lopez-Gonzaga+, 2017)

NASA Astrophysics Data System (ADS)

Lopez-Gonzaga, N.; Asmus, D.; Bauer, F. E.; Tristram, K. R. W.; Burtscher, L.; Marinucci, A.; Matt, G.; Harrison, F. A.

2017-06-01

Single-aperture mid-infrared images and spectra were taken with the VLT spectrometer and imager for the mid-infrared (VISIR). Interferometric measurements were obtained with the instrument MIDI at the ESO's VLTI facility. Observations with intermediate AT baselines were requested and observed during the nights of January, 10, 20, and 23, 2015 using Director's discretionary time (DDT). We additionally included published and unpublished interferometric data from our previous campaigns with the requirement that they were observed (nearly) contemporaneously to the period of X-ray variation or observed a few years before. These include observations taken on the nights of September, 21, 26, and 30, 2014, and November, 17, 2014, using Guaranteed Time Observations (GTO). For our observations we used the low-resolution NaCl prism with spectral resolution R=λ/Δλ~30 to disperse the light of the beams. A log of the observations and instrument setup can be found in Appendix A. The published data were taken from Lopez-Gonzaga et al. (2014A&A...565A..71L, Cat. J/A+A/565/A71). (2 data files).

A likely planet-induced gap in the disc around T Cha

NASA Astrophysics Data System (ADS)

Hendler, Nathanial P.; Pinilla, Paola; Pascucci, Ilaria; Pohl, Adriana; Mulders, Gijs; Henning, Thomas; Dong, Ruobing; Clarke, Cathie; Owen, James; Hollenbach, David

2018-03-01

We present high-resolution (0.11 × 0.06 arcsec2) 3 mm ALMA observations of the highly inclined transition disc around the star T Cha. Our continuum image reveals multiple dust structures: an inner disc, a spatially resolved dust gap, and an outer ring. When fitting sky-brightness models to the real component of the 3 mm visibilities, we infer that the inner emission is compact (≤1 au in radius), the gap width is between 18 and 28 au, and the emission from the outer ring peaks at ˜36 au. We compare our ALMA image with previously published 1.6 μm VLT/SPHERE imagery. This comparison reveals that the location of the outer ring is wavelength dependent. More specifically, the peak emission of the 3 mm ring is at a larger radial distance than that of the 1.6 μm ring, suggesting that millimeter-sized grains in the outer disc are located farther away from the central star than micron-sized grains. We discuss different scenarios to explain our findings, including dead zones, star-driven photoevaporation, and planet-disc interactions. We find that the most likely origin of the dust gap is from an embedded planet, and estimate - for a single planet scenario - that T Cha's gap is carved by a 1.2MJup planet.

The crowded magnetosphere of the post-common-envelope binary QS Virginis

NASA Astrophysics Data System (ADS)

Parsons, S. G.; Hill, C. A.; Marsh, T. R.; Gänsicke, B. T.; Watson, C. A.; Steeghs, D.; Dhillon, V. S.; Littlefair, S. P.; Copperwheat, C. M.; Schreiber, M. R.; Zorotovic, M.

2016-05-01

We present high-speed photometry and high-resolution spectroscopy of the eclipsing post-common-envelope binary QS Virginis (QS Vir). Our Ultraviolet and Visual Echelle Spectrograph (UVES) spectra span multiple orbits over more than a year and reveal the presence of several large prominences passing in front of both the M star and its white dwarf companion, allowing us to triangulate their positions. Despite showing small variations on a time-scale of days, they persist for more than a year and may last decades. One large prominence extends almost three stellar radii from the M star. Roche tomography reveals that the M star is heavily spotted and that these spots are long-lived and in relatively fixed locations, preferentially found on the hemisphere facing the white dwarf. We also determine precise binary and physical parameters for the system. We find that the 14 220 ± 350 K white dwarf is relatively massive, 0.782 ± 0.013 M⊙, and has a radius of 0.010 68 ± 0.000 07 R⊙, consistent with evolutionary models. The tidally distorted M star has a mass of 0.382 ± 0.006 M⊙ and a radius of 0.381 ± 0.003 R⊙, also consistent with evolutionary models. We find that the magnesium absorption line from the white dwarf is broader than expected. This could be due to rotation (implying a spin period of only ˜700 s), or due to a weak (˜100 kG) magnetic field, we favour the latter interpretation. Since the M star's radius is still within its Roche lobe and there is no evidence that it is overinflated, we conclude that QS Vir is most likely a pre-cataclysmic binary just about to become semidetached.

Surprisingly different star-spot distributions on the near equal-mass equal-rotation-rate stars in the M dwarf binary GJ 65 AB

NASA Astrophysics Data System (ADS)

Barnes, J. R.; Jeffers, S. V.; Haswell, C. A.; Jones, H. R. A.; Shulyak, D.; Pavlenko, Ya. V.; Jenkins, J. S.

2017-10-01

We aim to understand how stellar parameters such as mass and rotation impact the distribution of star-spots on the stellar surface. To this purpose, we have used Doppler imaging to reconstruct the surface brightness distributions of three fully convective M dwarfs with similar rotation rates. We secured high cadence spectral time series observations of the 5.5 au separation binary GJ 65, comprising GJ 65A (M5.5V, Prot = 0.24 d) and GJ 65B (M6V, Prot = 0.23 d). We also present new observations of GJ 791.2A (M4.5V, Prot = 0.31 d). Observations of each star were made on two nights with UVES, covering a wavelength range from 0.64 - 1.03μm. The time series spectra reveal multiple line distortions that we interpret as cool star-spots and which are persistent on both nights suggesting stability on the time-scale of 3 d. Spots are recovered with resolutions down to 8.3° at the equator. The global spot distributions for GJ 791.2A are similar to observations made a year earlier. Similar high latitude and circumpolar spot structure is seen on GJ 791.2A and GJ 65A. However, they are surprisingly absent on GJ 65B, which instead reveals more extensive, larger, spots concentrated at intermediate latitudes. All three stars show small amplitude latitude-dependent rotation that is consistent with solid body rotation. We compare our measurements of differential rotation with previous Doppler imaging studies and discuss the results in the wider context of other observational estimates and recent theoretical predictions.

ESO Highlights in 2008

NASA Astrophysics Data System (ADS)

2009-01-01

As is now the tradition, the European Southern Observatory looks back at the exciting moments of last year. 2008 was in several aspects an exceptionally good year. Over the year, ESO's telescopes provided data for more than 700 scientific publications in refereed journals, making ESO the most productive ground-based observatory in the world. ESO PR Highlights 2008 ESO PR Photo 01a/09 The image above is a clickable map. These are only some of the press releases issued by ESO in 2008. For a full listing, please go to ESO 2008 page. Austria signed the agreement to join the other 13 ESO member states (ESO 11/08 and 20/08), while the year marked the 10th anniversary of first light for ESO's "perfect science machine", the Very Large Telescope (ESO 16/08 and 17/08). The ALMA project, for which ESO is the European partner, had a major milestone in December, as the observatory was equipped with its first antenna (ESO 49/08). Also the Atacama Pathfinder Experiment (APEX) telescope impressed this year with some very impressive and publicly visible results. Highlights came in many fields: Astronomers for instance used the Very Large Telescope (VLT) to discover and image a probable giant planet long sought around the star Beta Pictoris (ESO 42/08). This is now the eighth extrasolar planet to have been imaged since the VLT imaged the first extrasolar planet in 2004 (three of eight were imaged with VLT). The VLT also enabled three students to confirm the nature of a unique planet (ESO 45/08). This extraordinary find, which turned up during their research project, is a planet about five times as massive as Jupiter. This is the first planet discovered orbiting a fast-rotating hot star. The world's foremost planet-hunting instrument, HARPS, located at ESO's La Silla observatory, scored a new first, finding a system of three super-Earths around a star (ESO 19/08). Based on the complete HARPS sample, astronomers now think that one Sun-like star out of three harbours short orbit, low-mass planets. With the VLT and another recent instrument, CRIRES, astronomers have also been able to study planet-forming discs around young Sun-like stars in unsurpassed detail, clearly revealing the motion and distribution of the gas in the inner parts of the disc, possibly implying the presence of giant planets (ESO 27/08). As the result of an impressive 16-year long study, that combines data obtained with ESO's New Technology Telescope and the VLT, a team of German astronomers has produced the most detailed view ever of the surroundings of the monster lurking at our Galaxy's heart -- a supermassive black hole (ESO 46/08). Combining data from APEX and the VLT, another team studied the violent flares coming from this region (ESO 41/08). The flares are the likely signatures of material being torn apart by the black hole. Making such science discoveries doesn't happen without the best technological tools. ESO is constantly upgrading its battery of instruments and telescopes on Cerro Paranal, home of the VLT. For example, the PRIMA instrument for the VLT Interferometer (VLTI) recently saw first light (ESO 29/08). When fully operational, PRIMA will boost the capabilities of the VLTI to see sources much fainter than any previous interferometers, and determine positions on the sky better than any other existing astronomical facility. The Multi-Conjugate Adaptive Optics Demonstrator (MAD) prototype, mounted on the VLT, provided astronomers with the sharpest image of the full disc of planet Jupiter ever taken from the Earth's surface (ESO 33/08). The future VISTA telescope on Paranal also received its record-curved 4.1-metre mirror, paving the way for unique surveys of the southern sky in the infrared (ESO 10/08). In preparation for other instruments of the future, staff at ESO joined with quantum optics specialists to develop a new calibration system for ultra-precise spectrographs (ESO 26/08). Given the presence of such state-of-the-art technology, it is perhaps no surprise that the crucial scenes from the latest James Bond sequel were filmed at Paranal (even though the director was really more interested in blowing up the Residencia, the lodge where staff and visitors can relax after working at one of the world's most advanced ground-based astronomical observatories). In March, a movie crew of 300 people, including the principal actors, were shooting at Paranal (ESO 007/08 and 38/08). On the outreach side, ESO's series of video podcasts, the ESOcast, premiered with the first three episodes. More than two thousand new and historic ESO images were put online in the ESO image archive as well as more than 300 hundred videos, mostly in High Definition. The work to digitise ESO's heritage will continue in 2009. Doubtless just as many exciting results will be presented this year too. Especially as 2009 has been officially declared the International Year of Astronomy (IYA) by the UN, UNESCO and the International Astronomical Union. The Year is coordinated from the global IYA Secretariat hosted by ESO. In addition ESO leads a number of global and regional activities.

The Secrets of the Nearest Starburst Cluster. I. Very Large Telescope/ISAAC Photometry of NGC 3603

NASA Astrophysics Data System (ADS)

Stolte, Andrea; Brandner, Wolfgang; Brandl, Bernhard; Zinnecker, Hans; Grebel, Eva K.

2004-08-01

VLT/ISAAC JHKL photometry with subarcsecond resolution of the dense, massive starburst cluster NGC 3603 YC forming the core of the NGC 3603 giant molecular cloud is analyzed to reveal characteristics of the stellar population in unprecedented detail. The color-magnitude plane features a strong pre-main-sequence/main-sequence (PMS/MS) transition region, including the PMS/MS transition point, and reveals a secondary sequence for the first time in a nearby young starburst cluster. Arguments for a possible binary nature of this sequence are given. The resolved PMS/MS transition region allows isochrone fitting below the hydrogen-burning turn-on in NGC 3603 YC, yielding an independent estimate of global cluster parameters. A distance modulus of 13.9 mag, equivalent to d=6.0+/-0.3 kpc, is derived, as well as a line-of-sight extinction of AV=4.5+/-0.6 toward PMS stars in the cluster center. The interpretation of a binary candidate sequence suggests a single age of 1 Myr for NGC 3603 YC, providing evidence for a single burst of star formation without the need to employ an age spread in the PMS population, as argued for in earlier studies. Disk fractions are derived from L-band excesses, indicating a radial increase in the disk frequency from 20% to 40% from the core to the cluster outskirts. The low disk fraction in the cluster core, as compared to the 42% L-band excess fraction found for massive stars in the Trapezium cluster of a comparably young age, indicates strong photoevaporation in the cluster center. The estimated binary fraction of 30%, as well as the low disk fraction, suggest strong impacts on low-mass star formation due to stellar interactions in the dense starburst. The significant differences between NGC 3603 YC and less dense and massive young star clusters in the Milky Way reveal the importance of using local starbursts as templates for massive extragalactic star formation. Based on observations obtained at the ESO VLT on Paranal, Chile, under programs 63.I-0015 and 65.I-0135, and data from the public VLT archive provided by ESO, as well as observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555.

Obsolescence of electronics at the VLT

NASA Astrophysics Data System (ADS)

Hüdepohl, Gerhard; Haddad, Juan-Pablo; Lucuix, Christian

2016-07-01

The ESO Very Large Telescope Observatory (VLT) at Cerro Paranal in Chile had its first light in 1998. Most of the telescopes' electronics components were chosen and designed in the mid 1990s and are now around 20 years old. As a consequence we are confronted with increasing failure rates due to aging and lack of spare parts, since many of the components are no longer available on the market. The lifetime of large telescopes is generally much beyond 25 years. Therefore the obsolescence of electronics components and modules becomes an issue sooner or later and forces the operations teams to upgrade the systems to new technology in order to avoid that the telescope becomes inoperable. Technology upgrade is a time and money consuming process, which in many cases is not straightforward and has various types of complications. This paper shows the strategy, analysis, approach, timeline, complications and progress in obsolescence driven electronics upgrades at the ESO Very Large Telescope (VLT) at the Paranal Observatory.

The new VLT-DSM M2 unit: construction and electromechanical testing

NASA Astrophysics Data System (ADS)

Gallieni, Daniele; Biasi, Roberto

2013-12-01

We present the design, construction and validation of the new M2 unit of the VLT Deformable Secondary Mirror. In the framework of the Adaptive Optics Facility program, ADS and Microgate designed a new secondary unit which replaces the current Dornier one. The M2 is composed by the mechanical structure, a new hexapod positioner and the Deformable Secondary Mirror unit.The DSM is based on the well proven contactless, voice coil motor technology that has been already successfully implemented in the MMT, LBT and Magellan adaptive secondaries, and is considered a promising technical choice for the E-ELT M4 and the GMT ASM. The VLT adaptive unit has been fully integrated and, before starting the optical calibration, has completed the electromechanical characterization, focused on the dynamic performance. With respect to the previous units we introduced several improvements, both in hardware and control architecture that allowed achieving a significant enhancement of the system dynamics and reduction of power consumption.

VLT enclosures: design and construction

NASA Astrophysics Data System (ADS)

Schneermann, Michael W.; Marchiori, Gianpietro; Dimichino, Francesco

1997-03-01

The VLT enclosures main functions are to protect the telescopes during operational as well as non-operational phases from any adverse weather conditions and to provide optimal conditions for observation. An adequate design of a ventilation and wind protection system is important for the performance of the enclosures with respect to the minimization of the corresponding seeing effects. The VLT enclosures are equipped with ventilation doors on the azimuth platform level, with louvers on the rotating part and with a windscreen at the observing slit. Extensive qualification tests of the louvers and windscreen mechanical assemblies have been performed during the enclosures development phase. This paper gives an overview over the general layout of the enclosures and the major subsystems, summarizes the main functional specifications and gives the main results and conclusions of the functional performance tests. Presently the first enclosure erection is nearing its completion and pre- commissioning of all systems will commence. The status of the site erection of the enclosures is presented and the planning for the next phases of the erection is presented.

A VLT Large Programme to Study Galaxies at z ~ 2: GMASS — the Galaxy Mass Assembly Ultra-deep Spectroscopic Survey

NASA Astrophysics Data System (ADS)

Kurk, Jaron; Cimatti, Andrea; Daddi, Emanuele; Mignoli, Marco; Bolzonella, Micol; Pozzetti, Lucia; Cassata, Paolo; Halliday, Claire; Zamorani, Gianni; Berta, Stefano; Brusa, Marcella; Dickinson, Mark; Franceschini, Alberto; Rodighiero, Guilia; Rosati, Piero; Renzini, Alvio

2009-03-01

We report on the motivation, sample selection and first results of our VLT FORS2 Large Programme (173.A-0687), which has obtained the longest targeted spectra of distant galaxies obtained so far with the VLT. These long exposures, up to 77 hours for objects included in three masks, were required to detect spectral features of extremely faint galaxies, such as absorption lines of passive galaxies at z > 1.4, a population that had previously escaped attention due to its faintness in the optical wavelength regime, but which represents a critical phase in the evolution of massive galaxies. The ultra-deep spectroscopy allowed us to estimate the stellar metallicity of star-forming galaxies at z ~ 2, to trace colour bimodality up to z = 2 and to characterise a galaxy cluster progenitor at z = 1.6. The approximately 200 spectra produced by GMASS constitute a lasting legacy, populating the “redshift desert” in GOODS-S.

The Orion Nebula: The Jewel in the Sword

NASA Astrophysics Data System (ADS)

2001-01-01

Orion the Hunter is perhaps the best known constellation in the sky, well placed in the evening at this time of the year for observers in both the northern and southern hemispheres, and instantly recognisable. And for astronomers, Orion is surely one of the most important constellations, as it contains one of the nearest and most active stellar nurseries in the Milky Way, the galaxy in which we live. Here tens of thousands of new stars have formed within the past ten million years or so - a very short span of time in astronomical terms. For comparison: our own Sun is now 4,600 million years old and has not yet reached half-age. Reduced to a human time-scale, star formation in Orion would have been going on for just one month as compared to the Sun's 40 years. Just below Orion's belt, the hilt of his sword holds a great jewel in the sky, the beautiful Orion Nebula . Bright enough to be seen with the naked eye, a small telescope or even binoculars show the nebula to be a few tens of light-years' wide complex of gas and dust, illuminated by several massive and hot stars at its core, the famous Trapezium stars . However, the heart of this nebula also conceals a secret from the casual observer. There are in fact about one thousand very young stars about one million years old within the so-called Trapezium Cluster , crowded into a space less than the distance between the Sun and its nearest neighbour stars. The cluster is very hard to observe in visible light, but is clearly seen in the above spectacular image of this area ( ESO PR 03a/01 ), obtained in December 1999 by Mark McCaughrean (Astrophysical Institute Potsdam, Germany) and his collaborators [1] with the infrared multi-mode ISAAC instrument on the ESO Very Large Telescope (VLT) at Paranal (Chile). Many details are seen in the new ISAAC image ESO PR Photo 03b/01 ESO PR Photo 03b/01 [Preview - JPEG: 400 x 589 pix - 62k] [Normal - JPEG: 800 x 1178 pix - 648k] [Hires - JPEG: 1957 x 2881 pix - 2.7M] ESO PR Photo 03c/01 ESO PR Photo 03c/01 [Preview - JPEG: 400 x 452 pix - 57k] [Normal - JPEG: 800 x 904 pix - 488k] [Hires - JPEG: 2300 x 2600 pix - 3.3M] Caption : PR Photo 03b/01 and PR Photo 03c/01 show smaller, particularly interesting areas of PR Photo 03a/01 . Photo 03b/01 shows the traces of a massive outflow of gas from a very young object embedded in the dense molecular cloud behind the Orion Nebula. Shards of gas from the explosion create shocks and leave bow-waves as they move at speeds of up to 200 km/sec from the source. Photo 03c/01 shows the delicate tracery created at the so-called Bright Bar , as the intense UV-light and strong winds from the hot Trapezium stars eat their way into the surrounding molecular cloud. Also visible are a number of very young red objects partly hidden in the cloud, waiting to be revealed as new members of the Trapezium Cluster . Technical information about these photos is available below. Indeed, at visible wavelengths, the dense cluster of stars at the centre is drowned out by the light from the nebula and obscured by remnants of the dust in the gas from which they were formed. However, at longer wavelengths, these obscuring effects are reduced, and the cluster is revealed. In the past couple of years, several of the world's premier ground- and space-based telescopes have made new detailed infrared studies of the Orion Nebula and the Trapezium Cluster , but the VLT image shown here is the "deepest" wide-field image obtained so far. The large collecting area of the VLT and the excellent seeing of the Paranal site combined to yield this beautiful image, packed full of striking details. Powerful explosions and winds from the most massive stars in the region are evident, as well as the contours of gas sculpted by these stars, and more finely focused jets of gas flowing from the smaller stars. Sharper images from the VLT ESO PR Photo 03d/01 ESO PR Photo 03d/01 [Preview - JPEG: 400 x 490 pix - 28k] [Normal - JPEG: 800 x 980 pix - 192k] [Hi-Res - JPEG: 2273 x 2784 pix - 976k] Caption : PR Photo 03d/01 shows a small section of the observational data (in one infrared spectral band only, here reproduced in B/W) on which PR Photo 03a/01 is based. The field is centred on one of the famous Orion silhouette disks (Orion 114-426) (it is located approximately halfway between the centre and the right edge of PR Photo 03c/01 ). The dusty disk itself is seen edge-on as a dark streak against the background emission of the Orion Nebula, while the bright fuzzy patches on either side betray the presence of the embedded parent star that illuminates tenuous collections of dust above its north and south poles to create these small reflection nebulae. Recent HST studies suggest that the very young Orion 114-426 disk - that is thirty times bigger than our present-day Solar System - may already be showing signs of forming its own proto-planetary system. Technical information about this photo is available below. It is even possible to see disks of dust and gas surrounding a few of the young stars, as silhouettes in projection against the bright background of the nebula. Many of these disks are very small and usually only seen on images obtained with the Hubble Space Telescope (HST) [2]. However, under the best seeing conditions on Paranal, the sharpness of VLT images at infrared wavelengths approaches that of the HST in this spectral band, revealing some of these disks, as shown in PR Photo 03d/01 . Indeed, the theoretical image sharpness of the 8.2-m VLT is more than three times better than that of the 2.4-m HST. Thus, the VLT will soon yield images of small regions with even higher resolution by means of the High-Resolution Near-Infrared Camera (CONICA) and the Nasmyth Adaptive Optics System (NAOS) that will compensate the smearing effect introduced by the turbulence in the atmosphere. Later on, extremely sharp images will be obtained when all four VLT telescopes are combined to form the Very Large Telescope Interferometer (VLTI). With these new facilities, astronomers will be able to make very detailed studies - among others, they will be looking for evidence that the dust and gas in these disks might be agglomerating to form planets. Free-floating planets in Orion? Recently, research teams working at other telescopes have claimed to have already seen planets in the Orion Nebula, as very dim objects, apparently floating freely between the brighter stars in the cluster. They calculated that if those objects are of the same age as the other stars, if they are located in the cluster, and if present theoretical predictions of the brightness of young stars and planets are correct, then they should have masses somewhere between 5 and 15 times that of planet Jupiter. Astronomer Mark McCaughrean is rather sceptical about this: " Calling these objects "planets" of course sounds exciting, but that interpretation is based on a number of assumptions. To me it seems equally probable that they are somewhat older, higher-mass objects of the "brown dwarf" type from a previous generation of star formation in Orion, which just happen to lie near the younger Trapezium Cluster today. Even if these objects were confirmed to have very low masses, many astronomers would disagree with them being called planets, since the common idea of a planet is that it should be in orbit around a star ". He explains: " While planets form in circumstellar disks, current thinking is that these Orion Nebula objects probably formed in the same way as do stars and brown dwarfs, and so perhaps we'd be better off talking about them just as low-mass brown dwarfs " and also notes that " similar claims of "free-floating planets" found in another cluster associated with the star Sigma Orionis have also been met with some scepticism ". Here, as in other branches of science, claim, counter-claim, scepticism and amicable controversy are typical elements of the scientific search for the truth. Thus the goal must now be to look at these objects in much more detail, and to try to determine their real properties and formation history. Comprehensive VLT study of Orion well underway This is indeed one of the main aims of the present major VLT study, of which the image shown here is decidedly a good start and a great "appetizer"! In fact, even the present photo - that is based on quite short exposures with a total of only 13.5 min at each image point (4.5 min in each of the three bands) - is already of sufficient quality to raise questions about some of the "very low-mass objects". McCaughrean acknowledges that " some of these very faint objects were right at the limit of earlier studies and hence the determination of their brightnesses was less precise. The new, more accurate VLT data show several of them to be intrinsically brighter than previously thought and thus more massive; also some other objects seem not to be there at all ". Clearly, the answer is to look even deeper in order to get more accurate data and to discover more of these objects. More infrared images were obtained for the present programme in December 2000 by the VLT team. They will now be combined with the earlier data shown here to create a very deep survey of the central area of the Orion Nebula. One of the great strengths of the VLT is its comprehensive instrumentation programme, and the team intends to carry out a detailed spectral analysis of the very faintest objects in the cluster, using the VLT VIMOS and NIRMOS multiobject spectrometers, as these become available. Only then, by analysing all these data, will it become possible to determine the masses, ages, and motions of the very faintest members of the Trapezium Cluster , and to provide a solid answer to the tantalising question of their origin. The beautiful infrared image shown here may just be a first "finding chart" made at the beginning of a long-term research project, but it already carries plenty of new astrophysical information. For the astronomers, images like these and the follow-up studies will help to solve some of the fascinating and perplexing questions about the birth and early lives of stars and their planetary systems. Note [1] The new VLT data covering the Orion Nebula and Trapezium Cluster were obtained as part of a long-term project by Mark McCaughrean (Principal Investigator, Astrophysical Institute Potsdam [AIP], Germany), João Alves (ESO, Garching, Germany), Hans Zinnecker (AIP) and Francesco Palla (Arcetri Observatory, Florence, Italy). The data also form part of the collaborative research being undertaken by the European Commission-sponsored Research Training Network on "The Formation and Evolution of Young Star Clusters" (RTN1-1999-00436), led by the Astrophysical Institute Potsdam, and including the Arcetri Observatory in Florence (Italy), the University of Cambridge (UK), the University of Cardiff (UK), the University of Grenoble (France), the University of Lisbon (Portugal) and the CEA Saclay (France). [2] To compare the present VLT infrared image with the more familiar view of the Orion Nebula in optical light, the ST-ECF has prepared an image covering a similar field from data taken with the NASA/ESA Hubble Space Telescope WFPC2 camera and extracted and processed by Jeremy Walsh from the ESO/ST-ECF archive. This 4-colour composite emphasises the light from the gaseous nebula rather than from the stars, and there is dramatic difference from the infrared view which sees much deeper into the region. The HST image is available at http://www.stecf.org/epo/support/orion/. Technical information about the photos PR Photo 03a/01 of the Orion Nebula and the Trapezium Cluster was made using the near-infrared camera ISAAC on the ESO 8.2-m VLT ANTU telescope on December 20 - 21, 1999. The full field measures approx. 7 x 7 arcmin, covering roughly 3 x 3 light-years (0.9 x 0.9 pc) at the distance of the nebula (about 1500 light-years, or 450 pc). This required a 9-position mosaic (3 x 3 grid) of ISAAC pointings; at each pointing, a series of images were taken in each of the near-infrared J s - (centred at 1.24 µm wavelength), H- (1.65 µm), and K s - (2.16 µm) bands. North is up and East left. The total integration time for each pixel in the mosaic was 4.5 min in each band. The seeing FWHM (full width at half maximum) was excellent, between 0.35 and 0.50 arcsec throughout. Point sources are detected at the 3-sigma level (central pixel above background noise) of 20.5, 19.2, and 18.8 magnitude in the J s -, H-, and K s -bands, respectively, mainly limited by the bright background emission of the nebula. After removal of instrumental signatures and the bright infrared sky background, all frames in a given band were carefully aligned and adjusted to form a seamless mosaic. The three monochromatic mosaics were then unsharp-masked and scaled logarithmically to reduce the enormous dynamic range and enhance the faint features of the outer nebula. The mosaics were then combined to create this colour-coded image, with the J s -band being rendered as blue, the H-band as green, and the K s -band as red. A total of 81 individual ISAAC images were merged to form this mosaic. PR Photos 03b-c/01 show smaller sections of the large image; the areas are 2.6 x 3.2 and 4.2 x 3.8 arcmin (1.1 x 1.4 and 1.8 x 1.6 light-years), respectively. PR Photo 03d/01 is based on J s band data only, to ensure good visibility (maximum contrast) of the Orion 114-426 silhouette disk against the background nebula. The three highest spatial resolution images covering this region were accurately aligned to form a mosaic with a resolution of 0.4 arcsec FWHM (180 Astronomical Units [AU]) in the vicinity of the disk. A 29 x 29 arcsec (0.2 x 0.2 light-year) section of this smaller mosaic was cut out and the square root of the intensity taken to enhance the disk. The disk is roughly 2 arcsec or 900 AU in diameter. North is up, East left.

Titanic Weather Forecasting

NASA Astrophysics Data System (ADS)

2004-04-01

New Detailed VLT Images of Saturn's Largest Moon Optimizing space missions Titan, the largest moon of Saturn was discovered by Dutch astronomer Christian Huygens in 1655 and certainly deserves its name. With a diameter of no less than 5,150 km, it is larger than Mercury and twice as large as Pluto. It is unique in having a hazy atmosphere of nitrogen, methane and oily hydrocarbons. Although it was explored in some detail by the NASA Voyager missions, many aspects of the atmosphere and surface still remain unknown. Thus, the existence of seasonal or diurnal phenomena, the presence of clouds, the surface composition and topography are still under debate. There have even been speculations that some kind of primitive life (now possibly extinct) may be found on Titan. Titan is the main target of the NASA/ESA Cassini/Huygens mission, launched in 1997 and scheduled to arrive at Saturn on July 1, 2004. The ESA Huygens probe is designed to enter the atmosphere of Titan, and to descend by parachute to the surface. Ground-based observations are essential to optimize the return of this space mission, because they will complement the information gained from space and add confidence to the interpretation of the data. Hence, the advent of the adaptive optics system NAOS-CONICA (NACO) [1] in combination with ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile now offers a unique opportunity to study the resolved disc of Titan with high sensitivity and increased spatial resolution. Adaptive Optics (AO) systems work by means of a computer-controlled deformable mirror that counteracts the image distortion induced by atmospheric turbulence. It is based on real-time optical corrections computed from image data obtained by a special camera at very high speed, many hundreds of times each second (see e.g. ESO Press Release 25/01 , ESO PR Photos 04a-c/02, ESO PR Photos 19a-c/02, ESO PR Photos 21a-c/02, ESO Press Release 17/02, and ESO Press Release 26/03 for earlier NACO images, and ESO Press Release 11/03 for MACAO-VLTI results.) The southern smile ESO PR Photo 08a/04 ESO PR Photo 08a/04 Images of Titan on November 20, 25 and 26, 2002 Through Five Filters (VLT YEPUN + NACO) [Preview - JPEG: 522 x 400 pix - 40k] [Normal - JPEG: 1043 x 800 pix - 340k] [Hires - JPEG: 2875 x 2205 pix - 1.2M] Caption: ESO PR Photo 08a/04 shows Titan (apparent visual magnitude 8.05, apparent diameter 0.87 arcsec) as observed with the NAOS/CONICA instrument at VLT Yepun (Paranal Observatory, Chile) on November 20, 25 and 26, 2003, between 6.00 UT and 9.00 UT. The median seeing values were 1.1 arcsec and 1.5 arcsec respectively for the 20th and 25th. Deconvoluted ("sharpened") images of Titan are shown through 5 different narrow-band filters - they allow to probe in some detail structures at different altitudes and on the surface. Depending on the filter, the integration time varies from 10 to 100 seconds. While Titan shows its leading hemisphere (i.e. the one observed when Titan moves towards us) on Nov. 20, the trailing side (i.e the one we see when Titan moves away from us in its course around Saturn) - which displays less bright surface features - is observed on the last two dates. ESO PR Photo 08b/04 ESO PR Photo 08b/04 Titan Observed Through Nine Different Filters on November 26, 2002 [Preview - JPEG: 480 x 400 pix - 36k] [Normal - JPEG: 960 x 800 pix - 284k] Caption: ESO PR Photo 08b/04: Images of Titan taken on November 26, 2002 through nine different filters to probe different altitudes, ranging from the stratosphere to the surface. On this night, a stable "seeing" (image quality before adaptive optics correction) of 0.9 arcsec allowed the astronomers to attain the diffraction limit of the telescope (0.032 arcsec resolution). Due to these good observing conditions, Titan's trailing hemisphere was observed with contrasts of about 40%, allowing the detection of several bright features on this surface region, once thought to be quite dark and featureless. ESO PR Photo 08c/04 ESO PR Photo 08c/04 Titan Surface Projections [Preview - JPEG: 601 x 400 pix - 64k] [Normal - JPEG: 1201 x 800 pix - 544k] Caption: ESO PR Photo 08c/04 : Titan images obtained with NACO on November 26th, 2002. Left: Titan's surface projection on the trailing hemisphere as observed at 1.3 μm, revealing a complex brightness structure thanks to the high image contrast of about 40%. Right: a new, possibly meteorological, phenomenon observed at 2.12 μm in Titan's atmosphere, in the form of a bright feature revolving around the South Pole. A team of French astronomers [2] have recently used the NACO state-of-the-art adaptive optics system on the fourth 8.2-m VLT unit telescope, Yepun, to map the surface of Titan by means of near-infrared images and to search for changes in the dense atmosphere. These extraordinary images have a nominal resolution of 1/30th arcsec and show details of the order of 200 km on the surface of Titan. To provide the best possible views, the raw data from the instrument were subjected to deconvolution (image sharpening). Images of Titan were obtained through 9 narrow-band filters, sampling near-infrared wavelengths with large variations in methane opacity. This permits sounding of different altitudes ranging from the stratosphere to the surface. Titan harbours at 1.24 and 2.12 μm a "southern smile", that is a north-south asymmetry, while the opposite situation is observed with filters probing higher altitudes, such as 1.64, 1.75 and 2.17 μm. A high-contrast bright feature is observed at the South Pole and is apparently caused by a phenomenon in the atmosphere, at an altitude below 140 km or so. This feature was found to change its location on the images from one side of the south polar axis to the other during the week of observations. Outlook An additional series of NACO observations of Titan is foreseen later this month (April 2004). These will be a great asset in helping optimize the return of the Cassini/Huygens mission. Several of the instruments aboard the spacecraft depend on such ground-based data to better infer the properties of Titan's surface and lower atmosphere. Although the astronomers have yet to model and interpret the physical and geophysical phenomena now observed and to produce a full cartography of the surface, this first analysis provides a clear demonstration of the marvellous capabilities of the NACO imaging system. More examples of the exciting science possible with this facility will be found in a series of five papers published today in the European research journal Astronomy & Astrophysics (Vol. 47, L1 to L24).

Multi-epoch observations with high spatial resolution of multiple T Tauri systems

NASA Astrophysics Data System (ADS)

Csépány, Gergely; van den Ancker, Mario; Ábrahám, Péter; Köhler, Rainer; Brandner, Wolfgang; Hormuth, Felix; Hiss, Hector

2017-07-01

Context. In multiple pre-main-sequence systems the lifetime of circumstellar discs appears to be shorter than around single stars, and the actual dissipation process may depend on the binary parameters of the systems. Aims: We report high spatial resolution observations of multiple T Tauri systems at optical and infrared wavelengths. We determine whether the components are gravitationally bound and orbital motion is visible, derive orbital parameters, and investigate possible correlations between the binary parameters and disc states. Methods: We selected 18 T Tau multiple systems (16 binary and two triple systems, yielding 16 + 2 × 2 = 20 binary pairs) in the Taurus-Auriga star-forming region from a previous survey, with spectral types from K1 to M5 and separations from 0.22″ (31 AU) to 5.8″ (814 AU). We analysed data acquired in 2006-07 at Calar Alto using the AstraLux lucky imaging system, along with data from SPHERE and NACO at the VLT, and from the literature. Results: We found ten pairs to orbit each other, five pairs that may show orbital motion, and five likely common proper motion pairs. We found no obvious correlation between the stellar parameters and binary configuration. The 10 μm infra-red excess varies between 0.1 and 7.2 mag (similar to the distribution in single stars, where it is between 1.7 and 9.1), implying that the presence of the binary star does not greatly influence the emission from the inner disc. Conclusions: We have detected orbital motion in young T Tauri systems over a timescale of ≈ 20 yr. Further observations with even longer temporal baseline will provide crucial information on the dynamics of these young stellar systems.

The nature of ultra-massive lens galaxies

NASA Astrophysics Data System (ADS)

Canameras, Raoul

2017-08-01

During the past decade, strong gravitational lensing analyses have contributed tremendously to the characterization of the inner properties of massive early-type galaxies, beyond the local Universe. Here we intend to extend studies of this kind to the most massive lens galaxies known to date, well outside the mass limits investigated by previous lensing surveys. This will allow us to probe the physics of the likely descendants of the most violent episodes of star formation and of the compact massive galaxies at high redshift. We propose WFC3 imaging (F438W and F160W) of four extremely massive early-type lens galaxies at z 0.5, in order to put them into context with the evolutionary trends of ellipticals as a function of mass and redshift. These systems were discovered in the SDSS and show one single main lens galaxy with a stellar mass above 1.5x10^12 Msun and large Einstein radii. Our high-resolution spectroscopic follow-up with VLT/X-shooter provides secure lens and source redshifts, between 0.3 and 0.7 and between 1.5 and 2.5, respectively, and confirm extreme stellar velocity dispersions > 400 km/s for the lenses. The excellent angular resolution of the proposed WFC3 imaging - not achievable from the ground - is the remaining indispensable piece of information to :(1) Resolve the lens structural parameters and obtain robust measurements of their stellar mass distributions,(2) Model the amount and distribution of the lens total masses and measure their M/L ratios and stellar IMF with joint strong lensing and stellar dynamics analyses,(3) Enhance our on-going lens models through the most accurate positions and morphologies of the blue multiply-imaged sources.

HST/WFPC2 and VLT/ISAAC Observations of Proplyds in the Giant H II Region NGC 3603

NASA Astrophysics Data System (ADS)

Brandner, Wolfgang; Grebel, Eva K.; Chu, You-Hua; Dottori, Horacio; Brandl, Bernhard; Richling, Sabine; Yorke, Harold W.; Points, Sean D.; Zinnecker, Hans

2000-01-01

We report the discovery of three proplyd-like structures in the giant H II region NGC 3603. The emission nebulae are clearly resolved in narrowband and broadband HST/WFPC2 observations in the optical and broadband VLT/ISAAC observations in the near-infrared. All three nebulae are tadpole shaped, with the bright ionization front at the head facing the central cluster and a fainter ionization front around the tail pointing away from the cluster. Typical sizes are 6000 AUx20,000 AU The nebulae share the overall morphology of the proplyds (PROto PLanetarY DiskS) in Orion, but are 20 to 30 times larger in size. Additional faint filaments located between the nebulae and the central ionizing cluster can be interpreted as bow shocks resulting from the interaction of the fast winds from the high-mass stars in the cluster with the evaporation flow from the proplyds. Low-resolution spectra of the brightest nebula, which is at a projected separation of 1.3 pc from the cluster, reveal that it has the spectral excitation characteristics of an ultra compact H II region with electron densities well in excess of 104 cm-3. The near-infrared data reveal a point source superposed on the ionization front. The striking similarity of the tadpole-shaped emission nebulae in NGC 3603 to the proplyds in Orion suggests that the physical structure of both types of objects might be the same. We present two-dimensional radiation hydrodynamical simulations of an externally illuminated star-disk-envelope system, which was still in its main accretion phase when first exposed to ionizing radiation from the central cluster. The simulations reproduce the overall morphology of the proplyds in NGC 3603 very well, but also indicate that mass-loss rates of up to 10-5 Msolar yr-1 are required in order to explain the size of the proplyds. Due to these high mass-loss rates, the proplyds in NGC 3603 should only survive ~105 yr. Despite this short survival time, we detect three proplyds. This indicates that circumstellar disks must be common around young stars in NGC 3603 and that these particular proplyds have only recently been exposed to their present harsh UV environment.

[Characteristic wavelengths selection of soluble solids content of pear based on NIR spectral and LS-SVM].

PubMed

Fan, Shu-xiang; Huang, Wen-qian; Li, Jiang-bo; Zhao, Chun-jiang; Zhang, Bao-hua

2014-08-01

To improve the precision and robustness of the NIR model of the soluble solid content (SSC) on pear. The total number of 160 pears was for the calibration (n=120) and prediction (n=40). Different spectral pretreatment methods, including standard normal variate (SNV) and multiplicative scatter correction (MSC) were used before further analysis. A combination of genetic algorithm (GA) and successive projections algorithm (SPA) was proposed to select most effective wavelengths after uninformative variable elimination (UVE) from original spectra, SNV pretreated spectra and MSC pretreated spectra respectively. The selected variables were used as the inputs of least squares-support vector machine (LS-SVM) model to build models for de- termining the SSC of pear. The results indicated that LS-SVM model built using SNVE-UVE-GA-SPA on 30 characteristic wavelengths selected from full-spectrum which had 3112 wavelengths achieved the optimal performance. The correlation coefficient (Rp) and root mean square error of prediction (RMSEP) for prediction sets were 0.956, 0.271 for SSC. The model is reliable and the predicted result is effective. The method can meet the requirement of quick measuring SSC of pear and might be important for the development of portable instruments and online monitoring.

VizieR Online Data Catalog: Near-IR spectrum of 2M1207b (Patience+, 2010)

NASA Astrophysics Data System (ADS)

Patience, J.; King, R. R.; de Rosa, R. J.; Marois, C.

2010-08-01

Near-IR spectroscopy of the planetary-mass companion to 2M1207. These observations were made with the ESO VLT SINFONI spectrograph. The flux has been scaled by the J and K-band photometry in the J and HK spectral orders. In regions of high telluric absorption the data have been masked and flux set to zero. (1 data file).

VLT spectroscopic observations of highly magnified Galactic Disk microlensing event Gaia18bmt

NASA Astrophysics Data System (ADS)

Wyrzykowski, L.; Gromadzki, M.; Kruszynska, K.; Rybicki, K. A.; Zielinski, P.

2018-06-01

Gaia18bmt (Ra, Dec = 14:16:03.55, -56:54:48.24) was found by Gaia Science Alerts programme on 2018-06-11 (http://gsaweb.ast.cam.ac.uk/alerts/alert/Gaia18bmt/) as a significant brigthening by more than 2 mag on a 15.5 mag star in the Galactic Disk (l,b = 314.32362, 4.07498).

Study of Pulsations in the Atmosphere of the roAp star HD 137949

NASA Astrophysics Data System (ADS)

Sachkov, M.; Hareter, M.; Ryabchikova, T.; Wade, G.; Kochukhov, O.; Weiss, W. W.

The roAp star HD 137949 (33 Lib) shows the most complex pulsational behaviour among all roAp stars. Mkrtichian et al. (2003) found nearly anti-phase pulsations of Nd II and Nd III lines, which they attribute to the presence of a pulsation node high in the atmosphere of HD 137949. This was confirmed by Kurtz at al. (2005), who also find that in some REE lines the main frequency, corresponding to 8.27 min, and its harmonic have almost equal RV amplitudes. Based on high accuracy observations Ryabchikova et al. (2007a) studied pulsational characteristics of the HD 137949 atmosphere in detail. In general, spectroscopy provides 3D resolution of modes and allows to search for the photometrically undetectable frequencies. The high-accuracy space photometry provides very high-precision measurements of detected pulsation frequencies and enables an accurate phasing of multi-site spectroscopic data. A combination of simultaneous spectroscopy and photometry represents the most sophisticated asteroseismic dataset for any roAp star. In 2009 the star HD 137949 became a target of an intense observing campaign that combined ground-based spectroscopy with space photometry, obtained with the MOST satellite. We collected 780 spectra using the ESPaDOnS spectrograph mounted on the 3.6 m CFHT telescope; 374 spectra were obtained with the FIES spectrograph mounted on the 2.56-m NOT to perform the time-resolved spectroscopy of HD 137949. In addition, we used 111 UVES spectra (2004) from the ESO archive to check the mode stability. The frequency analysis of the new radial velocity (RV) measurements confirmed the previously reported frequency pattern (two frequencies and the first harmonic of the main frequency), and revealed an additional frequency at 1.991 mHz. The new frequency solution fits perfectly the RV variations from the 2004 and 2009 observational sets providing a strong support for the p-mode stability in the roAp star HD 137949 for at least 5 years.

Summer at Saturn's North Pole: Seasonal Changes Seen by ISS & CIRS on Cassini, and VLT on the Ground

NASA Astrophysics Data System (ADS)

Sayanagi, K. M.; Blalock, J.; Fletcher, L. N.; Ingersoll, A. P.; Dyudina, U.; Ewald, S. P.

2016-12-01

We report seasonal changes in Saturn's north polar vortex seen by Cassini ISS, Cassini CIRS, and ground-based VLT VISIR thermal infrared observations. ISS observation of Saturn's northern high latitudes show that a reflective, bright polar spot has formed over the north pole, seen first in images captured in 2016. This coincides with the warm cyclonic north polar vortex that has been steadily warming since it was first discovered in 2007 by Cassini CIRS. The reflective spot was not present when the north pole was observed during the previous period of Cassini spacecraft's high-inclination orbits in 2012. In 2012, the concentration of light-scattering aerosols within 2-degree latitude of the north pole appeared to be less than that of the surrounding region, and appeared dark in all ISS filters. The new bright spot over the north pole is similar to that over the south pole seen in 2007. In 2007, Saturn was approaching the equinox of 2009 and south pole had been continuously illuminated since the previous equinox in 1995. The bright spot over the summer south pole in 2007 was hypothesized to consist of aerosols produced by ultraviolet photodissociation of hydrocarbon molecules; we follow this hypothesis to propose that the new bright spot over the north pole is also produced by the same mechanism. We argue that, in 2012 (3 years after equinox), the north polar bright spot hadn't formed because the ultraviolet insolation was not sufficient to produce enough photochemical aerosols. The new polar bright cloud formation is consistent with the rising abundances of stratospheric hydrocarbons (potential precursors to aerosol formation) over the north polar region as tracked by CIRS (Fletcher et al., 2015). In addition to ISS images, we also present CIRS and VLT-VISIR thermal maps of the northern high latitudes as the new north polar bright spot is expected to have implications on radiative energy balance. Our research has been supported by the Cassini Project, NASA grants OPR NNX11AM45G, CDAPS NNX15AD33G, PATM NNX14AK07G, and NSF grant AAG 1212216.

On the lithium dip in the metal poor open cluster NGC 2243

NASA Astrophysics Data System (ADS)

François, P.; Pasquini, L.; Biazzo, K.; Bonifacio, P.; Palsa, R.

2014-05-01

Lithium is a key element for studying the mixing mechanisms operating in stellar interiors. It can also be used to probe the chemical evolution of the Galaxy and the Big Bang nucleosynthesis. Measuring the abundance of Lithium in stars belonging to Open Clusters (hereafter OC) allows a detailed comparison with stellar evolutionary models. NGC 2243 is particularly interesting thanks to its relative low metallicity ([Fe/H]=-0.54 ± 0.10 dex). We performed a detailed analysis of high-resolution spectra obtained with the multi-object facility FLAMES at the VLT 8.2m telescope. Lithium abundance has been measured in 27 stars. We found a Li dip center of 1.06 M⊙, which is significantly smaller than that observed in solar metallicity and metal-rich clusters. This finding confirms and strengthens the conclusion that the mass of the stars in the Li dip strongly depends on stellar metallicity. The mean Li abundance of the cluster is log n(Li) = 2.70 dex, which is substantially higher than that observed in 47 Tue. We derived an iron abundance of [Fe/H]=-0.54±0.10 dex for NGC 2243, in agreement (within the errors) with previous findings.

AMBER-NACO aperture-synthesis imaging of the half-obscured central star and the edge-on disk of the red giant L2 Puppis

NASA Astrophysics Data System (ADS)

Ohnaka, K.; Schertl, D.; Hofmann, K.-H.; Weigelt, G.

2015-09-01

Aims: The red giant L2 Pup started a dimming event in 1994, which is considered to be caused by the ejection of dust clouds. We present near-IR aperture-synthesis imaging of L2 Pup achieved by combining data from VLT/NACO and the AMBER instrument of the Very Large Telescope Interferometer (VLTI). Our aim is to spatially resolve the innermost region of the circumstellar environment. Methods: We carried out speckle interferometric observations at 2.27 μm with VLT/NACO and long-baseline interferometric observations with VLTI/AMBER at 2.2-2.35 μm with baselines of 15-81 m. We also extracted an 8.7 μm image from the mid-IR VLTI instrument MIDI. Results: The diffraction-limited image obtained by bispectrum speckle interferometry with NACO with a spatial resolution of 57 mas shows an elongated component. The aperture-synthesis imaging combining the NACO speckle data and AMBER data with a spatial resolution of 5.6 × 7.3 mas further resolves not only this elongated component, but also the central star. The reconstructed image reveals that the elongated component is a nearly edge-on disk with a size of ~180 × 50 mas lying in the E-W direction, and furthermore, that the southern hemisphere of the central star is severely obscured by the equatorial dust lane of the disk. The angular size of the disk is consistent with the distance that the dust clouds that were ejected at the onset of the dimming event should have traveled by the time of our observations, if we assume that the dust clouds moved radially. This implies that the formation of the disk may be responsible for the dimming event. The 8.7 μm image with a spatial resolution of 220 mas extracted from the MIDI data taken in 2004 (seven years before the AMBER and NACO observations) shows an approximately spherical envelope without a signature of the disk. This suggests that the mass loss before the dimming event may have been spherical. Based on AMBER, NACO, and MIDI observations made with the Very Large Telescope and Very Large Telescope Interferometer of the European Southern Observatory. Program ID: 074.D-0075(A), 074.D-0101(A), 074.D-0198(B), 088.D-0150(A/B), and 288.D-5041(A). Appendices are available in electronic form at http://www.aanda.org

GRB host galaxies with VLT/X-Shooter: properties at 0.8 < z < 1.3

NASA Astrophysics Data System (ADS)

Piranomonte, S.; Japelj, J.; Vergani, S. D.; Savaglio, S.; Palazzi, E.; Covino, S.; Flores, H.; Goldoni, P.; Cupani, G.; Krühler, T.; Mannucci, F.; Onori, F.; Rossi, A.; D'Elia, V.; Pian, E.; D'Avanzo, P.; Gomboc, A.; Hammer, F.; Randich, S.; Fiore, F.; Stella, L.; Tagliaferri, G.

2015-10-01

Long gamma-ray bursts (LGRBs) are associated with the death of massive stars. Their host galaxies therefore represent a unique class of objects tracing star formation across the observable Universe. Indeed, recently accumulated evidence shows that GRB hosts do not differ substantially from general population of galaxies at high (z > 2) redshifts. However, it has been long recognized that the properties of z < 1.5 hosts, compared to general star-forming population, are unusual. To better understand the reasons for the supposed difference in LGRB hosts properties at z < 1.5, we obtained Very Large Telescope (VLT)/X-Shooter spectra of six hosts lying in the redshift range of 0.8 < z < 1.3. Some of these hosts have been observed before, yet we still lack well-constrained information on their characteristics such as metallicity, dust extinction and star formation rate (SFR). We search for emission lines in the VLT/X-Shooter spectra of the hosts and measure their fluxes. We perform a detailed analysis, estimating host average extinction, SFRs, metallicities and electron densities where possible. Measured quantities of our hosts are compared to a larger sample of previously observed GRB hosts at z < 2. SFRs and metallicities are measured for all the hosts analysed in this paper and metallicities are well determined for four hosts. The mass-metallicity relation, the fundamental metallicity relation and SFRs derived from our hosts occupy similar parameter space as other host galaxies investigated so far at the same redshift. We therefore conclude that GRB hosts in our sample support the found discrepancy between the properties of low-redshift GRB hosts and the general population of star-forming galaxies.

PC based PLCs and ethernet based fieldbus: the new standard platform for future VLT instrument control

NASA Astrophysics Data System (ADS)

Kiekebusch, Mario J.; Lucuix, Christian; Erm, Toomas M.; Chiozzi, Gianluca; Zamparelli, Michele; Kern, Lothar; Brast, Roland; Pirani, Werther; Reiss, Roland; Popovic, Dan; Knudstrup, Jens; Duchateau, Michel; Sandrock, Stefan; Di Lieto, Nicola

2014-07-01

ESO is currently in the final phase of the standardization process for PC-based Programmable Logical Controllers (PLCs) as the new platform for the development of control systems for future VLT/VLTI instruments. The standard solution used until now consists of a Local Control Unit (LCU), a VME-based system having a CPU and commercial and proprietary boards. This system includes several layers of software and many thousands of lines of code developed and maintained in house. LCUs have been used for several years as the interface to control instrument functions but now are being replaced by commercial off-the-shelf (COTS) systems based on BECKHOFF Embedded PCs and the EtherCAT fieldbus. ESO is working on the completion of the software framework that enables a seamless integration into the VLT control system in order to be ready to support upcoming instruments like ESPRESSO and ERIS, that will be the first fully VLT compliant instruments using the new standard. The technology evaluation and standardization process has been a long and combined effort of various engineering disciplines like electronics, control and software, working together to define a solution that meets the requirements and minimizes the impact on the observatory operations and maintenance. This paper presents the challenges of the standardization process and the steps involved in such a change. It provides a technical overview of how industrial standards like EtherCAT, OPC-UA, PLCOpen MC and TwinCAT can be used to replace LCU features in various areas like software engineering and programming languages, motion control, time synchronization and astronomical tracking.

Australia to Build Fibre Positioner for the Very Large Telescope

NASA Astrophysics Data System (ADS)

1998-06-01

The Anglo-Australian Observatory (AAO) at Epping (New South Wales, Australia) has been awarded the contract to build a fibre positioner for the European Southern Observatory's Very Large Telescope (VLT). This new, large astronomical facility is located at the Paranal Observatory in Chile and will feature four Unit Telescopes, each with a main mirror of 8.2-m diameter. This positioner, (affectionately) known as the OzPoz , will form part of the FLAMES facility (the F ibre L arge A rea M ulti- E lement S pectrograph), to be mounted on the second Unit Telescope (UT2) of the VLT in 2001. The construction of this facility includes other institutes in Europe, e.g. Observatoire de Genève (Switzerland) and Observatoire de Meudon (France). The ESO Instrument Division will coordinate the entire project that will result in an observational capability that is unique in the world. Optical fibres at astronomical telescopes Optical fibres have come to play an increasingly important role as transmitters of information, for instance in telephone and computer networks. It may be less known that they can be used in a similar way to transmit visible and infrared light in astronomical telescopes. Over the past decade, the AAO has been refining its skills in building optical-fibre instruments for its own telescopes, the 3.9-metre Anglo-Australian Telescope and the 1.2-m UK Schmidt Telescope (a telescope dedicated to wide-field surveys). These instruments enable astronomers to study many celestial objects simultaneously, increasing the effectiveness and productivity by enormous factors. The OzPoz positioner sets up to 560 optical fibres (developed in collaboration with the Observatoire de Meudon in France) very precisely by a robotic arm to match the positions of galaxies and quasars in the telescope's focal plane. The positional accuracy is about 50 µm (0.05 mm), or 0.08 arcsec on the sky. The fibres siphon the light from these very faint and distant astronomical objects and guide it to very efficient, custom designed, spectrographs. Here the light is dispersed into its characteristic colours and analysed to determine the object's type, distance and chemical composition, etc. ESO PR Photo 18/98 ESO PR Photo 18/98 Reduced resolution 1024 x 1024 pix [JPEG, 860k] Full resolution 1500 x 1500 pix [GIF, 2.1 Mb] This image illustrates the use of the new Fibre Positioner (OzPoz). It shows an example of the 25 arcmin field-of-view of the VLT with the FLAMES facility, as recorded during the ESO Imaging Survey (EIS) with the 3.5-m New Technology Telescope (NTT) at La Silla. Within only one night, FLAMES with the OzPoz positioner will be capable of obtaining optical and infrared spectra for no less than 1/3 of the approx. 9000 objects (many of which are distant galaxies) seen in this image! They can then be used to determine their redshift, chemical composition and dynamics. This will increase enormously the observational efficiency of the VLT. In just one night, it is possible to observe and analyse thousands of objects, a task that would have taken years in the past. The contract Dr. Brian Boyle , Director of the AAO, is very pleased with the new ESO contract: "The AAO has been recognised many times in the past as being a world-leader in astronomy, but this contract marks a new era. Up until now, we have built instruments for our own telescopes to ensure we stay ahead. Now we have expanded into instrument making for other telescopes. Our engineers, computer programmers and scientists have formed a productive and innovative team which is the envy of many observatories around the world." The Director General of ESO, Professor Riccardo Giacconi , is also happy: "The Anglo-Australian Observatory has excellent credentials in instrument making, and we have no doubt about their ability to build the critical optical fibre positioner for the VLT. The spectacular success of the AAO 2dF instrument (see below) reinforced our decision." The contract will take about 3 years to build and will involve the work of at least 10 AAO engineers and technicians over this period. The AAO 2dF optical fibre positioner The 2dF (two-degree field) optical fibre positioner has taken more than seven years to perfect, and is now fully operational at the 3.9 m Anglo-Australian Telescope. With it, two very ambitious survey projects are now well underway. The 2dF Galaxy Redshift Survey and the 2dF Quasar Redshift Survey aim at analysing more than 250 000 galaxies and 3000 quasars over the next few years to give a three-dimensional picture of the Universe on a large scale. A few nights of early observations yielded spectra from 4000 galaxies and 1000 quasars; a massive data set which, through expert, dedicated software, was analysed on-line and distributed to the international science team by email within minutes of the completion of the observations. Note: [1] This Press Release is issued jointly by ESO and the Anglo-Australian Observatory (AAO). This Press Release is accompanied by ESO PR Photo 18/98 . It is available in two versions: Reduced resolution 1024 x 1024 pix [JPEG, 860k] and Full resolution 1500 x 1500 pix [GIF, 2.1 Mb]. It may be reproduced, if credit is given to the European Southern Observatory. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

VLT/X-shooter Spectroscopy of a dusty planetary nebula discovered with Spitzer/IRS

NASA Astrophysics Data System (ADS)

Oliveira, I.; Overzier, R. A.; Pontoppidan, K. M.; van Dishoeck, E. F.; Spezzi, L.

2011-02-01

As part of a mid-infrared spectroscopic survey of young stars with the Spitzer Space Telescope, an unclassified red emission line object was discovered. Based on its high ionization state indicated by the Spitzer spectrum, this object could either be a dusty supernova remnant (SNR) or a planetary nebula (PN). In this research note, the object is classified and the available spectroscopic data are presented to the community for further analysis. UV/optical/NIR spectra were obtained during the science verification run of the VLT/X-shooter. A large number of emission lines are identified allowing the determination of the nature of this object. The presence of strong, narrow (Δv ~8 - 74 km s-1) emission lines, combined with very low line ratios of, e.g., [N ii]/Hα and [S ii]/Hα show that the object is a PN that lies at an undetermined distance behind the Serpens Molecular Cloud. This illustrates the potential of X-shooter as an efficient tool for constraining the nature of faint sources with unknown spectral properties or colors.

Green glass vitrophyre 78526 - An impact of very low-Ti mare basalt composition

NASA Technical Reports Server (NTRS)

Warner, R. D.; Taylor, G. J.; Kiel, K.; Planner, H. H.; Nehru, C. E.; Ma, M.-S.; Schmitt, R. A.

1978-01-01

Rake sample 78526 is an 8.77 g rock consisting primarily of vitrophyric pale green glass with subordinate mineral and lithic relics. Petrographic and compositional evidence leads to the following conclusions: (1) the bulk composition represents that of a mixture formed by impact melting of at least two different textural and compositional varieties of VLT mare basalt that are now present in the rock as lithic relics and a poorly defined low-Ti mare basalt component observed in thin section only in the form of isolated mineral relics; (2) the admixed VLT mare basalts had REE abundances lower than those found in other mare basalts (but probably higher than emerald green glass) and REE patterns showing significant enrichment of the heavy relative to light REE's, suggesting that they were derived by comparatively high degrees of partial melting of a clinopyroxene-rich source region; and (3) the impact melt supercooled to produce the vitrophyre, with rather sharply contrasting textural domains present in the vitrophyre resulting from differences in nucleation kinetics and degrees of supercooling in various portions of the sample.

pyZELDA: Python code for Zernike wavefront sensors

NASA Astrophysics Data System (ADS)

Vigan, A.; N'Diaye, M.

2018-06-01

pyZELDA analyzes data from Zernike wavefront sensors dedicated to high-contrast imaging applications. This modular software was originally designed to analyze data from the ZELDA wavefront sensor prototype installed in VLT/SPHERE; simple configuration files allow it to be extended to support several other instruments and testbeds. pyZELDA also includes simple simulation tools to measure the theoretical sensitivity of a sensor and to compare it to other sensors.

VLT/X-Shooter spectrum of the blazar TXS 0506+056 (located inside the IceCube-170922A error box)

NASA Astrophysics Data System (ADS)

Coleiro, Alexis; Chaty, Sylvain

2017-10-01

The blazar TXS 0506+056 (PMN J0509+0541) is currently reported to show increased gamma-ray and optical activity (ATel #10791, #10792, #10794, #10799, #10801, #10817, #10830, #10831, #10838) and has been proposed as the counterpart to the high-energy neutrino event IceCube-170922A (https://gcn.gsfc.nasa.gov/notices_amon/50579430_130033.amon).

Automated observation scheduling for the VLT

NASA Technical Reports Server (NTRS)

Johnston, Mark D.

1988-01-01

It is becoming increasingly evident that, in order to optimize the observing efficiency of large telescopes, some changes will be required in the way observations are planned and executed. Not all observing programs require the presence of the astronomer at the telescope: for those programs which permit service observing it is possible to better match planned observations to conditions at the telescope. This concept of flexible scheduling has been proposed for the VLT: based on current and predicted environmental and instrumental observations which make the most efficient possible use of valuable time. A similar kind of observation scheduling is already necessary for some space observatories, such as Hubble Space Telescope (HST). Space Telescope Science Institute is presently developing scheduling tools for HST, based on the use of artificial intelligence software development techniques. These tools could be readily adapted for ground-based telescope scheduling since they address many of the same issues. The concept are described on which the HST tools are based, their implementation, and what would be required to adapt them for use with the VLT and other ground-based observatories.

The Fornax Cluster VLT Spectroscopic Survey II - Planetary Nebulae kinematics within 200 kpc of the cluster core

NASA Astrophysics Data System (ADS)

Spiniello, C.; Napolitano, N. R.; Arnaboldi, M.; Tortora, C.; Coccato, L.; Capaccioli, M.; Gerhard, O.; Iodice, E.; Spavone, M.; Cantiello, M.; Peletier, R.; Paolillo, M.; Schipani, P.

2018-06-01

We present the largest and most spatially extended planetary nebulae (PNe) catalogue ever obtained for the Fornax cluster. We measured velocities of 1452 PNe out to 200 kpc in the cluster core using a counter-dispersed slitless spectroscopic technique with data from FORS2 on the Very Large Telescope (VLT). With such an extended spatial coverage, we can study separately the stellar haloes of some of the cluster main galaxies and the intracluster light. In this second paper of the Fornax Cluster VLT Spectroscopic Survey, we identify and classify the emission-line sources, describe the method to select PNe, and calculate their coordinates and velocities from the dispersed slitless images. From the PN 2D velocity map, we identify stellar streams that are possibly tracing the gravitational interaction of NGC 1399 with NGC 1404 and NGC 1387. We also present the velocity dispersion profile out to ˜200 kpc radii, which shows signatures of a superposition of the bright central galaxy and the cluster potential, with the latter clearly dominating the regions outside R ˜ 1000 arcsec (˜100 kpc).

Impaired ability to organize information in individuals with autism spectrum disorders and their siblings.

PubMed

Sumiyoshi, Chika; Kawakubo, Yuki; Suga, Motomu; Sumiyoshi, Tomiki; Kasai, Kiyoto

2011-03-01

Despite rigorous research on disturbances of executive function and social cognition in autism spectrum disorders (ASD), little information has been available concerning higher cognitive functions, such as the ability to focus and associate relevant features to form categories, or 'organizing of information'. The purpose of this study was to investigate this issue by using the Wisconsin Card Sorting Test (WCST) and the Verbal Learning Task (VLT). Cognitive assessments were conducted in 22 individuals with ASD, 14 non-affected siblings, and 15 age-matched control subjects. Overall, individuals with ASD performed significantly worse on the WCST and VLT compared to their siblings and normal control subjects. Although siblings performed generally well on both tasks, they exhibited similar degree of perseverative responses in the WCST compared to the probands. A linear increase of the memory organization score in the VLT was also absent in siblings as well as the ASD group. These results suggest an impaired ability to organize information is one of the cognitive endophenotypes for ASD. Copyright © 2010 Elsevier Ireland Ltd and the Japan Neuroscience Society. All rights reserved.

Final binary star results from the ESO VLT Lunar occultations program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richichi, A.; Fors, O.; Cusano, F.

2014-03-01

We report on 13 subarcsecond binaries, detected by means of lunar occultations in the near-infrared at the ESO Very Large Telescope (VLT). They are all first-time detections except for the visual binary HD 158122, which we resolved for the first time in the near-infrared. The primaries have magnitudes in the range K = 4.5-10.0, and companions in the range K = 6.8-11.1. The magnitude differences have a median value of 2.4, with the largest being 4.6. The projected separations are in the range of 4-168 mas, with a median of 13 mas. We discuss and compare our results with themore » available literature. With this paper, we conclude the mining for binary star detections in the 1226 occultations recorded at the VLT with the ISAAC instrument. We expect that the majority of these binaries may be unresolvable by adaptive optics on current telescopes, and they might be challenging for long-baseline interferometry. However, they constitute an interesting sample for future larger telescopes and for astrometric missions such as GAIA.« less

The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES)

NASA Astrophysics Data System (ADS)

Cami, J.; Cox, N. L.; Farhang, A.; Smoker, J.; Elyajouri, M.; Lallement, R.; Bacalla, X.; Bhatt, N. H.; Bron, E.; Cordiner, M. A.; de Koter, A..; Ehrenfreund, P.; Evans, C.; Foing, B. H.; Javadi, A.; Joblin, C.; Kaper, L.; Khosroshahi, H. G.; Laverick, M.; Le Petit, F..; Linnartz, H.; Marshall, C. C.; Monreal-Ibero, A.; Mulas, G.; Roueff, E.; Royer, P.; Salama, F.; Sarre, P. J.; Smith, K. T.; Spaans, M.; van Loon, J. T..; Wade, G.

2018-03-01

The ESO Diffuse Interstellar Band Large Exploration Survey (EDIBLES) is a Large Programme that is collecting high-signal-to-noise (S/N) spectra with UVES of a large sample of O and B-type stars covering a large spectral range. The goal of the programme is to extract a unique sample of high-quality interstellar spectra from these data, representing different physical and chemical environments, and to characterise these environments in great detail. An important component of interstellar spectra is the diffuse interstellar bands (DIBs), a set of hundreds of unidentified interstellar absorption lines. With the detailed line-of-sight information and the high-quality spectra, EDIBLES will derive strong constraints on the potential DIB carrier molecules. EDIBLES will thus guide the laboratory experiments necessary to identify these interstellar “mystery molecules”, and turn DIBs into powerful diagnostics of their environments in our Milky Way Galaxy and beyond. We present some preliminary results showing the unique capabilities of the EDIBLES programme.

Near-IR 2D-spectroscopy of the 4''x 4'' region around the Active Galactic Nucleus of NGC 1068 with ISAAC/VLT

NASA Astrophysics Data System (ADS)

Galliano, E.; Alloin, D.

2002-10-01

New near-IR long slit spectroscopic data obtained with ISAAC on VLT/ANTU (ESO/Paranal) complement and extend our previously published near-IR data (Alloin et al. \\cite{all01}) to produce Brgamma and H2 emission line maps and line profile grids of the central 4'' x 4'' region surrounding the central engine of NGC 1068. The seeing quality together with the use of an 0.3'' wide slit and 0.3'' slit position offsets allow one to perform 2D-spectroscopy at a spatial resolution ~ 0.5''. Slit orientations (PA = 102 degr and PA = 12 degr) were chosen so as to match respectively the equatorial plane and the axis of the suspected molecular/dusty torus in NGC 1068. The selected wavelength range from 2.1 to 2.2μm is suitable to detect and analyze the Brgamma and H2 emission lines at a spectral resolution corresponding to 35km s-1. An asymmetric distribution of H2 emission around the continuum peak is observed. No H2 emission is detected at the location of the strong 2.2μm continuum core (coincident within error-bars with the central engine location), while two conspicuous knots of H2 emission are detected at about 1'' on each side of the central engine along PA = 90 degr, with a projected velocity difference of 140km s-1: this velocity jump has been interpreted in Alloin et al. (\\cite{all01}) as the signature of a rotating disk of molecular material. From this new data set, we find that only very low intensity Brgamma emission is detected at the location of the two main knots of H2 emission. Another knot with both H2 and Brgamma emission is detected to the North of the central engine, close to the radio source C where the small scale radio jet is redirected and close to the brightest [OIII] cloud NLR-B. It has a counterpart to the South, placed almost symmetrically with respect to the central engine, although mainly visible in the Brgamma emission. The northern and southern knots appear to be related to the ionization cone. At the achieved spectral resolution, the H2 emission line profiles appear highly asymmetric with their low velocity wing being systematically more extended than their high velocity wing. A simple way to account for the changes of the H2 line profiles (peak-shift with respect to the systemic velocity, width, asymmetry) over the entire 4'' x 4'' region, is to consider that a radial outflow is superimposed over the emission of the rotating molecular disk. We present a model of such a kinematical configuration and compare our predicted H2 emission profiles to the observed ones. Excitation of the H2 line is briefly discussed: X-ray irradiation from the central engine is found to be the most likely source of excitation. Given the fact that the material obscuring our direct view toward the central engine is Compton thick (NH >= 1024 {cm-2}), the observed location of the main H2 knots at a distance of 70 pc from the central engine suggests that the rotating molecular disk is warped. Based on observations collected at the ESO/Paranal 8 m UT1 telescope, Proposals 63.P-0167A & 66.B-0142A.

The Abundances of the Fe Group Elements in AV 304, an Abundance Standard in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Peters, Geraldine J.; Lanz, Thierry; Bouret, Jean-Claude; Proffitt, Charles R.; Adelman, Saul J.; Hubeny, Ivan

2018-06-01

AV 304 is a B0.5 IV field star in the Small Magellanic Cloud with ultra-sharp spectral lines that has emerged as an abundance standard. We have combined recent spectroscopic observations from the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope with archival data from the Far Ultraviolet Spectroscopic Explorer (FUSE) and ESO’s VLT/UVES to determine the abundances of the Fe group elements (Ti, V, Cr, Mn, Fe, Co, & Ni). The analysis was carried through using the Hubeny/Lanz NLTE programs TLUSTY/SYNSPEC. The COS observations were secured with the G130M, G160M, G185M, and G225M gratings. Combined with the FUSE data, we have achieved spectral coverage in the UV from 950 to 2400 A. Measurable lines from the Fe group, except for a very few multiplets of Fe II, III are not observed in optical spectra. The following stellar parameters were found: Teff = 27500±500 K, log g = 3.7±0.1 cm/s2, Vturb= 1±1 km/s, and v sin i = 8 ±2 km/s. The Fe abundance appears to be only slightly lower than the mean depletion in the SMC, but the other Fe group elements are underabundant by 0.3 dex or more. This study confirmed the low abundance of nitrogen (-1.25 dex relative to the solar value) that was reported by Peters & Adelman (ASP Conf. Series, 348, p. 136, 2006). Whereas the light elements are delivered to the ISM by core-collapse supernovae (CCSNe), the Fe group elements are believed to come mostly from low/intermediate mass binaries containing white dwarfs that undergo SNe Ia explosions. A single SNe Ia can deliver 0.5 solar masses of pure Fe (and maybe Mn) to the ISM compared with about 0.07 solar masses from a CCSNe. It appears that there is very little processed material from its interior in the atmosphere of AV 304 and that the star did not form from an interstellar cloud that was enriched by material from earlier supernova activity. Support from STScI grants HST-GO-14081.002 and HST-GO-13346.022, and USC’s Women in Science and Engineering (WiSE) program is greatly appreciated.

A new method for detecting velocity shifts and distortions between optical spectra

DOE Office of Scientific and Technical Information (OSTI.GOV)

Evans, Tyler M.; Murphy, Michael T., E-mail: tevans@astro.swin.edu.au

2013-12-01

Recent quasar spectroscopy from the Very Large Telescope (VLT) and Keck suggests that fundamental constants may not actually be constant. To better confirm or refute this result, systematic errors between telescopes must be minimized. We present a new method to directly compare spectra of the same object and measure any velocity shifts between them. This method allows for the discovery of wavelength-dependent velocity shifts between spectra, i.e., velocity distortions, that could produce spurious detections of cosmological variations in fundamental constants. This 'direct comparison' method has several advantages over alternative techniques: it is model-independent (cf. line-fitting approaches), blind, in that spectralmore » features do not need to be identified beforehand, and it produces meaningful uncertainty estimates for the velocity shift measurements. In particular, we demonstrate that, when comparing echelle-resolution spectra with unresolved absorption features, the uncertainty estimates are reliable for signal-to-noise ratios ≳7 per pixel. We apply this method to spectra of quasar J2123–0050 observed with Keck and the VLT and find no significant distortions over long wavelength ranges (∼1050 Å) greater than ≈180 m s{sup –1}. We also find no evidence for systematic velocity distortions within echelle orders greater than 500 m s{sup –1}. Moreover, previous constraints on cosmological variations in the proton-electron mass ratio should not have been affected by velocity distortions in these spectra by more than 4.0 ± 4.2 parts per million. This technique may also find application in measuring stellar radial velocities in search of extra-solar planets and attempts to directly observe the expansion history of the universe using quasar absorption spectra.« less

A Powerful Twin Arrives

NASA Astrophysics Data System (ADS)

1999-11-01

First Images from FORS2 at VLT KUEYEN on Paranal The first, major astronomical instrument to be installed at the ESO Very Large Telescope (VLT) was FORS1 ( FO cal R educer and S pectrograph) in September 1998. Immediately after being attached to the Cassegrain focus of the first 8.2-m Unit Telescope, ANTU , it produced a series of spectacular images, cf. ESO PR 14/98. Many important observations have since been made with this outstanding facility. Now FORS2 , its powerful twin, has been installed at the second VLT Unit Telescope, KUEYEN . It is the fourth major instrument at the VLT after FORS1 , ISAAC and UVES.. The FORS2 Commissioning Team that is busy installing and testing this large and complex instrument reports that "First Light" was successfully achieved already on October 29, 1999, only two days after FORS2 was first mounted at the Cassegrain focus. Since then, various observation modes have been carefully tested, including normal and high-resolution imaging, echelle and multi-object spectroscopy, as well as fast photometry with millisecond time resolution. A number of fine images were obtained during this work, some of which are made available with the present Press Release. The FORS instruments ESO PR Photo 40a/99 ESO PR Photo 40a/99 [Preview - JPEG: 400 x 345 pix - 203k] [Normal - JPEG: 800 x 689 pix - 563kb] [Full-Res - JPEG: 1280 x 1103 pix - 666kb] Caption to PR Photo 40a/99: This digital photo shows the twin instruments, FORS2 at KUEYEN (in the foreground) and FORS1 at ANTU, seen in the background through the open ventilation doors in the two telescope enclosures. Although they look alike, the two instruments have specific functions, as described in the text. FORS1 and FORS2 are the products of one of the most thorough and advanced technological studies ever made of a ground-based astronomical instrument. They have been specifically designed to investigate the faintest and most remote objects in the universe. They are "multi-mode instruments" that may be used in several different observation modes. FORS2 is largely identical to FORS1 , but there are a number of important differences. For example, it contains a Mask Exchange Unit (MXU) for laser-cut star-plates [1] that may be inserted at the focus, allowing a large number of spectra of different objects, in practice up to about 70, to be taken simultaneously. Highly sophisticated software assigns slits to individual objects in an optimal way, ensuring a great degree of observing efficiency. Instead of the polarimetry optics found in FORS1 , FORS2 has new grisms that allow the use of higher spectral resolutions. The FORS project was carried out under ESO contract by a consortium of three German astronomical institutes, the Heidelberg State Observatory and the University Observatories of Göttingen and Munich. The participating institutes have invested a total of about 180 man-years of work in this unique programme. The photos below demonstrate some of the impressive possibilities with this new instrument. They are based on observations with the FORS2 standard resolution collimator (field size 6.8 x 6.8 armin = 2048 x 2048 pixels; 1 pixel = 0.20 arcsec). In addition, observations of the Crab pulsar demonstrate a new observing mode, high-speed photometry. Protostar HH-34 in Orion ESO PR Photo 40b/99 ESO PR Photo 40b/99 [Preview - JPEG: 400 x 444 pix - 220kb] [Normal - JPEG: 800 x 887 pix - 806kb] [Full-Res - JPEG: 2000 x 2217 pix - 3.6Mb] The Area around HH-34 in Orion ESO PR Photo 40c/99 ESO PR Photo 40c/99 [Preview - JPEG: 400 x 494 pix - 262kb] [Full-Res - JPEG: 802 x 991 pix - 760 kb] The HH-34 Superjet in Orion (centre) PR Photo 40b/99 shows a three-colour composite of the young object Herbig-Haro 34 (HH-34) , now in the protostar stage of evolution. It is based on CCD frames obtained with the FORS2 instrument in imaging mode, on November 2 and 6, 1999. This object has a remarkable, very complicated appearance that includes two opposite jets that ram into the surrounding interstellar matter. This structure is produced by a machine-gun-like blast of "bullets" of dense gas ejected from the star at high velocities (approaching 250 km/sec). This seems to indicate that the star experiences episodic "outbursts" when large chunks of material fall onto it from a surrounding disk. HH-34 is located at a distance of approx. 1,500 light-years, near the famous Orion Nebula , one of the most productive star birth regions. Note also the enigmatic "waterfall" to the upper left, a feature that is still unexplained. PR Photo 40c/99 is an enlargement of a smaller area around the central object. Technical information : Photo 40b/99 is based on a composite of three images taken through three different filters: B (wavelength 429 nm; Full-Width-Half-Maximum (FWHM) 88 nm; exposure time 10 min; here rendered as blue), H-alpha (centered on the hydrogen emission line at wavelength 656 nm; FWHM 6 nm; 30 min; green) and S II (centrered at the emission lines of inonized sulphur at wavelength 673 nm; FWHM 6 nm; 30 min; red) during a period of 0.8 arcsec seeing. The field shown measures 6.8 x 6.8 arcmin and the images were recorded in frames of 2048 x 2048 pixels, each measuring 0.2 arcsec. The Full Resolution version shows the original pixels. North is up; East is left. N 70 Nebula in the Large Magellanic Cloud ESO PR Photo 40d/99 ESO PR Photo 40d/99 [Preview - JPEG: 400 x 444 pix - 360kb] [Normal - JPEG: 800 x 887 pix - 1.0Mb] [Full-Res - JPEG: 1997 x 2213 pix - 3.4Mb] The N 70 Nebula in the LMC ESO PR Photo 40e/99 ESO PR Photo 40e/99 [Preview - JPEG: 400 x 485 pix - 346kb] [Full-Res - JPEG: 986 x 1196 pix - 1.2Mb] The N70 Nebula in the LMC (detail) PR Photo 40d/99 shows a three-colour composite of the N 70 nebula. It is a "Super Bubble" in the Large Magellanic Cloud (LMC) , a satellite galaxy to the Milky Way system, located in the southern sky at a distance of about 160,000 light-years. This photo is based on CCD frames obtained with the FORS2 instrument in imaging mode in the morning of November 5, 1999. N 70 is a luminous bubble of interstellar gas, measuring about 300 light-years in diameter. It was created by winds from hot, massive stars and supernova explosions and the interior is filled with tenuous, hot expanding gas. An object like N70 provides astronomers with an excellent opportunity to explore the connection between the lifecycles of stars and the evolution of galaxies. Very massive stars profoundly affect their environment. They stir and mix the interstellar clouds of gas and dust, and they leave their mark in the compositions and locations of future generations of stars and star systems. PR Photo 40e/99 is an enlargement of a smaller area of this nebula. Technical information : Photos 40d/99 is based on a composite of three images taken through three different filters: B (429 nm; FWHM 88 nm; 3 min; here rendered as blue), V (554 nm; FWHM 111 nm; 3 min; green) and H-alpha (656 nm; FWHM 6 nm; 3 min; red) during a period of 1.0 arcsec seeing. The field shown measures 6.8 x 6.8 arcmin and the images were recorded in frames of 2048 x 2048 pixels, each measuring 0.2 arcsec. The Full Resolution version shows the original pixels. North is up; East is left. The Crab Nebula in Taurus ESO PR Photo 40f/99 ESO PR Photo 40f/99 [Preview - JPEG: 400 x 446 pix - 262k] [Normal - JPEG: 800 x 892 pix - 839 kb] [Full-Res - JPEG: 2036 x 2269 pix - 3.6Mb] The Crab Nebula in Taurus ESO PR Photo 40g/99 ESO PR Photo 40g/99 [Preview - JPEG: 400 x 444 pix - 215kb] [Full-Res - JPEG: 817 x 907 pix - 485 kb] The Crab Nebula in Taurus (detail) PR Photo 40f/99 shows a three colour composite of the well-known Crab Nebula (also known as "Messier 1" ), as observed with the FORS2 instrument in imaging mode in the morning of November 10, 1999. It is the remnant of a supernova explosion at a distance of about 6,000 light-years, observed almost 1000 years ago, in the year 1054. It contains a neutron star near its center that spins 30 times per second around its axis (see below). PR Photo 40g/99 is an enlargement of a smaller area. More information on the Crab Nebula and its pulsar is available on the web, e.g. at a dedicated website for Messier objects. In this picture, the green light is predominantly produced by hydrogen emission from material ejected by the star that exploded. The blue light is predominantly emitted by very high-energy ("relativistic") electrons that spiral in a large-scale magnetic field (so-called syncrotron emission ). It is believed that these electrons are continuously accelerated and ejected by the rapidly spinning neutron star at the centre of the nebula and which is the remnant core of the exploded star. This pulsar has been identified with the lower/right of the two close stars near the geometric center of the nebula, immediately left of the small arc-like feature, best seen in PR Photo 40g/99 . Technical information : Photo 40f/99 is based on a composite of three images taken through three different optical filters: B (429 nm; FWHM 88 nm; 5 min; here rendered as blue), R (657 nm; FWHM 150 nm; 1 min; green) and S II (673 nm; FWHM 6 nm; 5 min; red) during periods of 0.65 arcsec (R, S II) and 0.80 (B) seeing, respectively. The field shown measures 6.8 x 6.8 arcmin and the images were recorded in frames of 2048 x 2048 pixels, each measuring 0.2 arcsec. The Full Resolution version shows the original pixels. North is up; East is left. The High Time Resolution mode (HIT) of FORS2 ESO PR Photo 40h/99 ESO PR Photo 40h/99 [Preview - JPEG: 400 x 304 pix - 90kb] [Normal - JPEG: 707 x 538 pix - 217kb] Time Sequence of the Pulsar in the Crab Nebula ESO PR Photo 40i/99 ESO PR Photo 40i/99 [Preview - JPEG: 400 x 324 pix - 42kb] [Normal - JPEG: 800 x 647 pix - 87kb] Lightcurve of the Pulsar in the Crab Nebula In combination with the large light collecting power of the VLT Unit Telescopes, the high time resolution (25 nsec = 0.000000025 sec) of the ESO-developed FIERA CCD-detector controller opens a new observing window for celestial objects that undergo light intensity variations on very short time scales. A first implementation of this type of observing mode was tested with FORS2 during the first commissioning phase, by means of one of the most fascinating astronomical objects, the rapidly spinning neutron star in the Crab Nebula . It is also known as the Crab pulsar and is an exceedingly dense object that represents an extreme state of matter - it weighs as much as the Sun, but measures only about 30 km across. The result presented here was obtained in the so-called trailing mode , during which one of the rectangular openings of the Multi-Object Spectroscopy (MOS) assembly within FORS2 is placed in front of the lower end of the field. In this way, the entire surface of the CCD is covered, except the opening in which the object under investigation is positioned. By rotating this opening, some neighbouring objects (e.g. stars for alignment) may be observed simultaneously. As soon as the shutter is opened, the charges on the chip are progressively shifted upwards, one pixel at a time, until those first collected in the bottom row behind the opening have reached the top row. Then the entire CCD is read out and the digital data with the full image is stored in the computer. In this way, successive images (or spectra) of the object are recorded in the same frame, displaying the intensity variation with time during the exposure. For this observation, the total exposure lasted 2.5 seconds. During this time interval the image of the pulsar (and those of some neighbouring stars) were shifted 2048 times over the 2048 rows of the CCD. Each individual exposure therefore lasted exactly 1.2 msec (0.0012 sec), corresponding to a nominal time-resolution of 2.4 msec (2 pixels). Faster or slower time resolutions are possible by increasing or decreasing the shift and read-out rate [2]. In ESO PR Photo 40h/99 , the continuous lines in the top and bottom half are produced by normal stars of constant brightness, while the series of dots represents the individual pulses of the Crab pulsar, one every 33 milliseconds (i.e. the neutron star rotates around its axis 30 times per second). It is also obvious that these dots are alternatively brighter and fainter: they mirror the double-peaked profile of the light pulses, as shown in ESO PR Photo 40i/99 . In this diagramme, the time increases along the abscissa axis (1 pixel = 1.2 msec) and the momentary intensity (uncalibrated) is along the ordinate axis. One full revolution of the neutron star corresponds to the distance from one high peak to the next, and the diagramme therefore covers six consecutive revolutions (about 200 milliseconds). Following thorough testing, this new observing mode will allow to investigate the brightness variations of this and many other objects in great detail in order to gain new and fundamental insights in the physical mechanisms that produce the radiation pulses. In addition, it is foreseen to do high time resolution spectroscopy of rapidly varying phenomena. Pushing it to the limits with an 8.2-m telescope like KUEYEN will be a real challenge to the observers that will most certainly lead to great and exciting research projects in various fields of modern astrophysics. Technical information : The frame shown in Photo 40h/99 was obtained during a total exposure time of 2.5 sec without any optical filtre. During this time, the charges on the CCD were shifted over 2048 rows; each row was therefore exposed during 1.2 msec. The bright continuous line comes from the star next to the pulsar; the orientation was such that the "observation slit" was placed over two neighbouring stars. Preliminary data reduction: 11 pixels were added across the pulsar image to increase the signal-to-noise ratio and the background light from the Crab Nebula was subtracted for the same reason. Division by a brighter star (also background-subtracted, but not shown in the image) helped to reduce the influence of the Earth's atmosphere. Notes [1] The masks are produced by the Mask Manufacturing Unit (MMU) built by the VIRMOS Consortium for the VIMOS and NIRMOS instruments that will be installed at the VLT MELIPAL and YEPUN telescopes, respectively. [2] The time resolution achieved during the present test was limited by the maximum charge transfer rate of this particular CCD chip; in the future, FORS2 may be equipped with a new chip with a rate that is up to 20 times faster. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Sharpest Ever VLT Images at NAOS-CONICA "First Light"

NASA Astrophysics Data System (ADS)

2001-12-01

Very Promising Start-Up of New Adaptive Optics Instrument at Paranal Summary A team of astronomers and engineers from French and German research institutes and ESO at the Paranal Observatory is celebrating the successful accomplishment of "First Light" for the NAOS-CONICA Adaptive Optics facility . With this event, another important milestone for the Very Large Telescope (VLT) project has been passed. Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. However, with the Adaptive Optics (AO) technique, this drawback can be overcome and the telescope produces images that are at the theoretical limit, i.e., as sharp as if it were in space . Adaptive Optics works by means of a computer-controlled, flexible mirror that counteracts the image distortion induced by atmospheric turbulence in real time. The larger the main mirror of the telescope is, and the shorter the wavelength of the observed light, the sharper will be the images recorded. During a preceding four-week period of hard and concentrated work, the expert team assembled and installed this major astronomical instrument at the 8.2-m VLT YEPUN Unit Telescope (UT4). On November 25, 2001, following careful adjustments of this complex apparatus, a steady stream of photons from a southern star bounced off the computer-controlled deformable mirror inside NAOS and proceeded to form in CONICA the sharpest image produced so far by one of the VLT telescopes. With a core angular diameter of only 0.07 arcsec, this image is near the theoretical limit possible for a telescope of this size and at the infrared wavelength used for this demonstration (the K-band at 2.2 µm). Subsequent tests reached the spectacular performance of 0.04 arcsec in the J-band (wavelength 1.2 µm). "I am proud of this impressive achievement", says ESO Director General Catherine Cesarsky. "It shows the true potential of European science and technology and it provides a fine demonstration of the value of international collaboration. ESO and its partner institutes and companies in France and Germany have worked a long time towards this goal - with the first, extremely promising results, we shall soon be able to offer a new and fully tuned instrument to our wide research community." The NAOS adaptive optics corrector was built, under an ESO contract, by Office National d'Etudes et de Recherches Aérospatiales (ONERA) , Laboratoire d'Astrophysique de Grenoble (LAOG) and the DESPA and DASGAL laboratories of the Observatoire de Paris in France, in collaboration with ESO. The CONICA infra-red camera was built, under an ESO contract, by the Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck Institut für Extraterrestrische Physik (MPE) (Garching) in Germany, in collaboration with ESO. The present event happens less than four weeks after "First Fringes" were achieved for the VLT Interferometer (VLTI) with two of the 8.2-m Unit Telescopes. No wonder that a spirit of great enthusiasm reigns at Paranal! Information for the media: ESO is producing a Video News Release ( ESO Video News Reel No. 13 ) with sequences from the NAOS-CONICA "First Light" event at Paranal, a computer animation illustrating the principle of adaptive optics in NAOS-CONICA, as well as the first astronomical images obtained. In addition to the usual distribution, this VNR will also be transmitted via satellite Friday 7 December 2001 from 09:00 to 09:15 CET (10:00 to 10:15 UT) on "Europe by Satellite" . These video images may be used free of charge by broadcasters. Satellite details, the script and the shotlist will be on-line from 6 December on the ESA TV Service Website http://television.esa.int. Also a pre-view Real Video Stream of the video news release will be available as of that date from this URL. Video Clip 07/01 : Various video scenes related to the NAOS-CONICA "First Light" Event ( ESO Video News Reel No. 13 ). PR Photo 33a/01 : NAOS-CONICA "First light" image of an 8-mag star. PR Photo 33b/01 : The moment of "First Light" at the YEPUN Control Consoles. PR Photo 33c/01 : Image of NGC 3603 (K-band) area (NAOS-CONICA) . PR Photo 33d/01 : Image of NGC 3603 wider field (ISAAC) PR Photo 33e/01 : I-band HST-WFPC2 image of NGC 3603 field . PR Photo 33f/01 : Animated GIF, with NAOS-CONICA (K-band) and HST-WFPC2 (I-band) images of NGC 3603 area PR Photo 33g/01 : Image of the Becklin-Neugebauer Object . PR Photo 33h/01 : Image of a very close double star . PR Photo 33i/01 : Image of a 17-magnitude reference star PR Photo 33j/01 : Image of the central area of the 30 Dor star cluster . PR Photo 33k/01 : The top of the Paranal Mountain (November 25, 2001). PR Photo 33l/01 : The NAOS-CONICA instrument attached to VLT YEPUN.. A very special moment at Paranal! First light for NAOS-CONICA at the VLT - PR Video Clip 07/01] ESO PR Video Clip 07/01 "First Light for NAOS-CONICA" (25 November 2001) (3850 frames/2:34 min) [MPEG Video+Audio; 160x120 pix; 3.6Mb] [MPEG Video+Audio; 320x240 pix; 8.9Mb] [RealMedia; streaming; 34kps] [RealMedia; streaming; 200kps] ESO Video Clip 07/01 provides some background scenes and images around the NAOS-CONICA "First Light" event on November 25, 2001 (extracted from ESO Video News Reel No. 13 ). Contents: NGC 3603 image from ISAAC and a smaller field as observed by NAOS-CONICA ; the Paranal platform in the afternoon, before the event; YEPUN and NAOS-CONICA with cryostat sounds; Tension is rising in the VLT Control Room; Wavefront Sensor display; the "Loop is Closed"; happy team members; the first corrected image on the screen; Images of NGC 3603 by HST and VLT; 30 Doradus central cluster; BN Object in Orion; Statement by the Head of the ESO Instrument Division. ESO PR Photo 33a/01 ESO PR Photo 33a/01 [Preview - JPEG: 317 x 400 pix - 27k] [Normal - JPEG: 800 x 634 pix - 176k] ESO PR Photo 33b/01 ESO PR Photo 33b/01 [Preview - JPEG: 400 x 322 pix - 176k] [Normal - JPEG: 800 x 644 pix - 360k] ESO PR Photo 33a/01 shows the first image in the infrared K-band (wavelength 2.2 µm) of a star (visual magnitude 8) obtained - before (left) and after (right) the adaptive optics was switched on (see the text). The middle panel displays the 3-D intensity profiles of these images, demonstrating the tremendous gain, both in image sharpness and central intensity. ESO PR Photo 33b/01 shows some of the NAOS-CONICA team members in the VLT Control Room at the moment of "First Light" in the night between November 25-26, 2001. From left to right: Thierry Fusco (ONERA), Clemens Storz (MPIA), Robin Arsenault (ESO), Gerard Rousset (ONERA). The numerous boxes with the many NAOS and CONICA parts arrived at the ESO Paranal Observatory on October 24, 2001. Astronomers and engineers from ESO and the participating institutes and organisations then began the painstaking assembly of these very complex instruments on one of the Nasmyth platforms on the fourth VLT 8.2-m Unit Telescope, YEPUN . Then followed days of technical tests and adjustments, working around the clock. In the afternoon of Sunday, November 25, the team finally declared the instrument fit to attempt its "First Light" observation. The YEPUN dome was opened at sunset and a small, rather apprehensive group gathered in the VLT Control Room, peering intensively at the computer screens over the shoulders of their colleagues, the telescope and instrument operators. Time passed imperceptibly to those present, as the basic calibrations required at this early stage to bring NAOS-CONICA to full operational state were successfully completed. Everybody sensed the special moment approaching when, finally, the telescope operator pushed a button and the giant telescope started to turn smoothly towards the first test object, an otherwise undistinguished star in our Milky Way. Its non-corrected infra-red image was recorded by the CONICA detector array and soon appeared on the computer screen. It was already very good by astronomical standards, with a diameter of only 0.50 arsec (FWHM), cf. PR Photo 33a/01 (left) . Then, by another command, the instrument operator switched on the NAOS adaptive optics system , thereby "closing the loop" for the first time on a sky field, by using that ordinary star as a reference light source to measure the atmospheric turbulence. Obediently, the deformable mirror in NAOS began to follow the "orders" that were issued 500 times per second by its powerful control computer.... As if by magics, that stellar image on the computer screen pulled itself together....! What seconds before had been a jumping, rather blurry patch of light suddenly became a rock-steady, razor-sharp and brilliant spot of light. The entire room burst into applause - there were happy faces and smiles all over, and then the operator announced the measured image diameter - a truly impressive 0.068 arcsec, already at this first try, cf. PR Photo 33a/01 (right) ! All the team members who were lucky to be there sent a special thought to those many others who had also put in over four years' hard and dedicated work to make this event a reality. The time of this historical moment was November 25, 2001, 23:00 Chilean time (November 26, 2001, 02:00 am UT) . During this and the following nights, more images were made of astronomcal objects, opening a new chapter of the long tradition of Adaptive Optics at ESO. More information about the NAOS-CONICA international collaboration , technical details about this instrument and its special advantages are available below. The first images The star-forming region around NGC 3603 ESO PR Photo 33c/01 ESO PR Photo 33c/01 [Preview - JPEG: 326 x 400 pix - 200k] [Normal - JPEG: 651 x 800 pix - 480k] ESO PR Photo 33d/01 ESO PR Photo 33d/01 [Preview - JPEG: 348 x 400 pix - 240k] [Normal - JPEG: 695 x 800 pix - 592k] Caption : PR Photo 33c/01 displays a NAOS-CONICA image of the starburst cluster NGC 3603, obtained during the second night of NAOS-CONICA operation. The sky region shown is some 20 arcsec to the North of the centre of the cluster. NAOS was compensating atmospheric disturbances by analyzing light from the central star with its visual wavefront sensor, while CONICA was observing in the K-band. The image is nearly diffraction-limited and has a Full-Width-Half-Maximum (FWHM) diameter of 0.07 arcsec, with a central Strehl ratio of 56% (a measure of the degree of concentration of the light). The exposure lasted 300 seconds. North is up and East is left. The field measures 27 x 27 arcsec. On PR Photo 33d/01 , the sky area shown in this NAOS-CONICA high-resolution image is indicated on an earlier image of a much larger area, obtained in 1999 with the ISAAC multi-mode instrument on VLT ANTU ( ESO PR 16/99 ) Among the first images to be obtained of astronomical objects was one of the stellar cluster NGC 3603 that is located in the Carina spiral arm in the Milky Way at a distance of about 20,000 light-years, cf. PR Photo 33c/01 . With its central starburst cluster, it is one of the densest and most massive star forming regions in our Galaxy. Some of the most massive stars - with masses up to 120 times the mass of our Sun - can be found in this cluster. For a long time astronomers have suspected that the formation of low-mass stars is suppressed by the presence of high-mass stars, but two years ago, stars with masses as low as 10% of the mass of our Sun were detected in NGC 3603 with the ISAAC multi-mode instrument at VLT ANTU, cf. PR Photo 33d/01 and ESO PR 16/99. The high stellar density in this region, however, prevented the search for objects with still lower masses, so-called Brown Dwarfs. The new, high-resolution K-band images like PR Photo 33c/01 , obtained with NAOS-CONICA at YEPUN, now for the first time facilitate the study of the elusive class of brown dwarfs in such a starburst environment. This will, among others, offer very valuable insight into the fundamental problem about the total amount of matter that is deposited into stars in star-forming regions. An illustration of the potential of Adaptive Optics ESO PR Photo 33e/01 ESO PR Photo 33e/01 [Preview - JPEG: 376 x 400 pix - 128k] [Normal - JPEG: 752 x 800 pix - 336k] ESO PR Photo 33f/01 ESO PR Photo 33f/01 [Animated GIF: 400 x 425 pix - 71k] Caption : PR Photo 33e/01 was obtained with the WFPC2 camera on the Hubble Space Telescope (HST) in the I-band (800nm). It is a 400-sec exposure and shows the same sky region as in the NAOS-CONICA image shown in PR Photo 33c/01. PR Photo 33f/01 provides a direct comparison of the two images (animated GIF). The HST image was extracted from archival data. HST is operated by NASA and ESA. Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence . However, the Adaptive Optics (AO) technique overcomes this problem and when the AO instrument is optimized, the telescope produces images that are at the theoretical limit, i.e., as sharp as if it were in space . The theoretical image diameter is inversely proportional to the diameter of the main mirror of the telescope and proportional to the wavelength of the observed light. Thus, the larger the telescope and the shorter the wavelength, the sharper will be the images recorded . To illustrate this, a comparison of the NAOS-CONICA image of NGC 3603 ( PR Photo 33c/01 ) is here made with a near-infrared image obtained earlier by the Hubble Space Telescope (HST) covering the same sky area ( PR Photo 33e/01 ). Both images are close to the theoretical limit ("diffraction limited"). However, the diameter of the VLT YEPUN mirror (8.2-m) is somewhat more than three times that of that of HST (2.4-m). This is "compensated" by the fact that the wavelength of the NAOS-CONICA image (2.2 µm) is about two-and-a-half times longer that than of the HST image (0.8 µm). The measured image diameters are therefore not too different, approx. 0.085 arcsec (HST) vrs. approx. 0.068 arcsec (VLT). Although the exposure times are similar (300 sec for the VLT image; 400 sec for the HST image), the VLT image shows considerably fainter objects. This is partly due to the larger mirror, partly because by observing at a longer wavelength, NAOS-CONICA can detect a host of cool low-mass stars. The Becklin-Neugebauer object and its associated nebulosity ESO PR Photo 33g/01 ESO PR Photo 33g/01 [Preview - JPEG: 299 x 400 pix - 128k] [Normal - JPEG: 597 x 800 pix - 272k] Caption : PR Photo 33g/01 is a composite (false-) colour image obtained by NAOS-CONICA of the region around the Becklin-Neugebauer object that is deeply embedded in the Orion Nebula. It is based on two exposures, one in the light of shock-excited molecular hydrogen line (H 2 ; wavelength 2.12 µm; here rendered as blue) and one in the broader K-band (2.2 µm; red) from ionized hydrogen. A third (green) image was produced as an "average" of the H 2 and K-band images. The field-of-view measures 20 x 25 arcsec 2 , cf. the 1 x 1 arcsec 2 square. North is up and east to the left. PR Photo 33g/01 is a composite image of the region around the Becklin-Neugebauer object (generally refered to as "BN" ). With its associated Kleinmann-Low nebula, it is located in the Orion star forming region at a distance of approx. 1500 light-years. It is the nearest high-mass star-forming complex. The immediate vicinity of BN (the brightest star in the image) is highly dynamic with outflows and cloudlets glowing in the light of shock-excited molecular hydrogen. While many masers and outflows have been detected, the identification of their driving sources is still lacking. Deep images in the infrared K and H bands, as well as in the light of molecular hydrogen emission were obtained with NAOS-CONICA at VLT YEPUN during the current tests. The new images facilitate the detection of fainter and smaller structures in the cloud than ever before. More details on the embedded star cluster are revealed as well. These observations were only made possible by the infrared wavefront sensor of NAOS. The latter is a unique capability of NAOS and allows to do adaptive optics on highly embedded infrared sources, which are practically invisible at optical wavelengths. Exploring the limits ESO PR Photo 33h/01 ESO PR Photo 33h/01 [Preview - JPEG: 400 x 260 pix - 44k] [Normal - JPEG: 800 x 520 pix - 112k] Caption : PR Photo 33h/01 shows a NAOS-CONICA image of the double star GJ 263 for which the angular distance between the two components is only 0.030 arcsec . The raw image, as directly recorded by CONICA, is shown in the middle, with a computer-processed (using the ONERA MISTRAL myopic deconvolution algorithm) version to the right. The recorded Point-Spread-Function (PSF) is shown to the left. For this, the C50S camera (0.01325 arcsec/pixel) was used, with an FeII filter at the near-infrared wavelength 1.257 µm. The exposure time was 10 seconds. ESO PR Photo 33i/01 ESO PR Photo 33i/01 [Preview - JPEG: 400 x 316 pix - 82k] [Normal - JPEG: 800 x 631 pix - 208k] Caption : PR Photo 33i/01 shows the near-diffraction-limited image of a 17-mag reference star , as recorded with NAOS-CONICA during a 200-second exposure in the K-band under 0.60 arcsec seeing. The 3D-profile is also shown. ESO PR Photo 33j/01 ESO PR Photo 33j/01 [Preview - JPEG: 342 x 400 pix - 83k] [Normal - JPEG: 684 x 800 pix - 200k] Caption : PR Photo 33j/01 shows the central cluster in the 30 Doradus HII region in the Large Magellanic Cloud (LMC), a satellite of our Milky Way Galaxy. It was obtained by NAOS-CONICA in the infrared K-band during a 600 second exposure. The field shown here measures 15 x 15 arcsec 2. PR Photos 33h-j/01 provide three examples of images obtained during specific tests where the observers pushed NAOS-CONICA towards the limits to explore the potential of the new instrument. Although, as expected, these images are not "perfect", they bear clear witness to the impressive performance, already at this early stage of the commissioning programme. The first PR Photo 33h/01 shows how diffraction-limited imaging with NAOS-CONICA at a wavelength of 1.257 µm allows to view the individual components of a close double star, here the binary star GJ 263 for which the angular distance between the two stars is only 0.030 arcsec (i.e., the angle subtended by a 1 Euro coin at a distance of 160 km). Spatially resolved observations of binary stars like this one will allow the determination of orbital parameters, and ultimately of the masses of the individual binary star components. After few days of optimisation and calibration, NAOS-CONICA was able to "close the loop" on a reference star as faint as visual magnitude 17 and to provide a fine diffraction-limited K-band image with Strehl ratio 19% under 0.6 arcsec seeing. PR Photo 33i/01 provides a view of this image, as seen in the recorder frame and as a 3D-profile. The exposure time was 200 seconds. The ability to use reference stars as faint as this is an enormous asset for NAOS-CONICA - it will be first to offer this capability to non-specialist users with an instrument on an 8-10 m class telescope . This permits to access many sky fields and already get significant AO corrections, without having to wait for the artificial laser guide star now being constructed for the VLT, see below. 30 Doradus in the Large Magellanic Cloud (LMC - a satellite of our Galaxy) is the most luminous, giant HII region in the Local Group of Galaxies. It is powered by a massive star cluster with more than 100 ultra-luminous stars (of the "Wolf-Rayet"-type and O-stars). The NAOS CONICA K-band image PR Photo 33x/01 resolves the dense stellar core of high-mass stars at the centre of the cluster, revealing thousands of lower mass cluster members. Due to the lack of a sufficiently bright, isolated and single reference star in this sky field, the observers used instead the bright central star complex (R136a) to generate the corrective signals to the flexible mirror, needed to compensate for the atmospheric turbulence. However, R136a is not a round object; it is strongly elongated in the "5 hour"-direction. As a result, all star images seen in this photo are slightly elongated in the same direction as R136a. Nevertheless, this is a small penalty to pay for the large improvement obtained over a direct (seeing-limited) image! Adaptive Optics at ESO - a long tradition ESO PR Photo 33k/01 ESO PR Photo 33k/01 [Preview - JPEG: 400 x 320 pix - 144k] [Normal - JPEG: 800 x 639 pix - 344k] [Hi-Res - JPEG: 3000 x 2398 pix - 3.0M] ESO PR Photo 33l/01 ESO PR Photo 33l/01 [Preview - JPEG: 400 x 367 pix - 47k] [Normal - JPEG: 800 x 734 pix - 592k] [Hi-Res - JPEG: 3000 x 2754 pix - 3.9M] Caption : PR Photo 33k/01 is a view of the upper platform at the ESO Paranal Observatory with the four enclosures for the VLT 8.2-m Unit Telescopes and the partly subterranean Interferometric Laboratory (at centre). YEPUN (UT4) is housed in the enclosure to the right. This photo was obtained in the evening of November 25, 2001, some hours before "First Light" was achieved for the new NAOS-CONICA instrument, mounted at that telescope. PR Photo 33l/01 NAOS-CONICA installed on the Nasmyth B platform of the 8.2-m VLT YEPUN Unit Telescope. From left to right: the telescope adapter/rotator (dark blue), NAOS (light blue) and the CONICA cryostat (red). The control electronics is housed in the white cabinet. "Adaptive Optics" is a modern buzzword of astronomy. It embodies the seemingly magic way by which ground-based telescopes can overcome the undesirable blurring effect of atmospheric turbulence that has plagued astronomers for centuries. With "Adaptive Optics", the images of stars and galaxies captured by these instruments are now as sharp as theoretically possible. Or, as the experts like to say, "it is as if a giant ground-based telescope is 'lifted' into space by a magic hand!" . Adaptive Optics works by means of a computer-controlled, flexible mirror that counteracts the image distortion induced by atmospheric turbulence in real time. The concept is not new. Already in 1989, the first Adaptive Optics system ever built for Astronomy (aptly named "COME-ON" ) was installed on the 3.6-m telescope at the ESO La Silla Observatory, as the early fruit of a highly successful continuing collaboration between ESO and French research institutes (ONERA and Observatoire de Paris). Ten years ago, ESO initiated an Adaptive Optics program , to serve the needs for its frontline VLT project. In 1993, the Adaptive Optics facility (ADONIS) was offered to Europe's astronomers, as the first instrument of its kind, available for non-specialists. It is still in operation and continues to produce frontline results, cf. ESO PR 22/01. In 1997, ESO launched a collaborative effort with a French Consortium ( see below) for the development of the NAOS Nasmyth Adaptive Optics System . With its associated CONICA IR high angular resolution camera , developed with a German Consortium ( see below), it provides a full high angular resolution capability on the VLT at Paranal. With the successful "First Light" on November 25, 2001, this project is now about to enter into the operational phase. The advantages of NAOS-CONICA NAOS-CONICA belongs to a new generation of sophisticated adaptive optics (AO) devices. They have certain advantages over past systems. In particular, NAOS is unique in being equipped with an infrared-sensitive Wavefront Sensor (WFS) that permits to look inside regions that are highly obscured by interstellar dust and therefore unobservable in visible light. With its other WFS for visible light , NAOS should be able to achieve the highest degree of light concentration (the so-called "Strehl ratio") obtained at any existing 8-m class telescope. It also provides partially corrected images, using reference stars (see PR Photo 33e/01 ) as faint as visual magnitude 18, fainter than demonstrated so far at any other AO system at such large telescope. A major advantage of CONICA is to offer the large format and very high image quality required to fully match NAOS' performance , as well as a variety of observing modes. Moreover, NAOS-CONICA is the first astronomical AO instrument to be offered with a full end-to-end observing capability. It is completely integrated into the VLT dataflow system , with a seamless process from the preparation of the observations, including optimization of the instrument, to their execution at the telescope and on to automatic data quality assessment and storage in the VLT Archive. Collaboration and Institutes The Nasmyth Adaptive Optics System (NAOS) has been developed, with the support of INSU-CNRS, by a French Consortium in collaboration with ESO. The French consortium consists of Office National d'Etudes et de Recherches Aérospatiales (ONERA) , Laboratoire d'Astrophysique de Grenoble (LAOG) and Observatoire de Paris (DESPA and DASGAL). The Project Manager is Gérard Rousset (ONERA), the Instrument Responsible is François Lacombe (Observatoire de Paris) and the Project Scientist is Anne-Marie Lagrange (Laboratoire d'Astrophysique de Grenoble). The CONICA Near-Infrared CAmera has been developed by a German Consortium, with an extensive ESO collaboration. The Consortium consists of Max-Planck-Institut für Astronomie (MPIA) (Heidelberg) and the Max-Planck-Institut für Extraterrestrische Physik (MPE) (Garching). The Principal Investigator (PI) is Rainer Lenzen (MPIA), with Reiner Hofmann (MPE) as Co-Investigator. Contacts Norbert Hubin European Southern Observatory Garching, Germany Tel.: +4989-3200-6517 email: nhubin@eso.org Alan Moorwood European Southern Observatory Garching, Germany Tel.: +4989-3200-6294 email: amoorwoo@eso.org Appendix: Technical Information about NAOS and CONICA Once fully tested, NAOS-CONICA will provide adaptive optics assisted imaging, polarimetry and spectroscopy in the 1 - 5 µm waveband. NAOS is an adaptive optics system equipped with both visible and infrared, Shack-Hartmann type, wavefront sensors. Provided a reference source (e.g., a star) with visual magnitude V brighter than 18 or K-magnitude brighter than 13 mag is available within 60 arcsec of the science target, NAOS-CONICA will ultimately offer diffraction limited resolution at the level of 0.030 arcsec at a wavelength of 1 µm, albeit with a large halo around the image core for the faint end of the reference source brightness. This may be compared with VLT median seeing images of 0.65 arcsec at a wavelength of 1 µm and exceptionally good images around 0.30 arcsec. NAOS-CONICA is installed at Nasmyth Focus B at VLT YEPUN (UT4). In about two years' time, this instrument will benefit from a sodium Laser Guide Star (LGS) facility. The creation of an artificial guide star is then possible in any sky field of interest, thereby providing a much better sky coverage than what is possible with natural guide stars only. NAOS is equipped with two wavefront sensors, one in the visible part of the spectrum (0.45 - 0.95 µm) and one in the infrared part (1 - 2.5 µm); both are based on the Shack-Hartmann principle. The maximum correction frequency is about 500 Hz. There are 185 deformable mirror actuators plus a tip-tilt mirror correction. Together, they should permit to obtain a high Strehl ratio in the K-band (2.2 µm), up to 70%, depending on the actual seeing and waveband. Both the visible and IR wavefront sensors (WFS) have been optimized to provide AO correction for faint objects/stars. The visible WFS provides a low-order correction for objects as faint as visual magnitude ~ 18. The IR WFS will provide a low-order correction for objects as faint as K-magnitude 13. CONICA is a high performant instrument in terms of image quality and detector sensitivity. It has been designed so that it is able to make optimal use of the AO system. Inherent mechanical flexures are corrected on-line by NAOS through a pointing model. It offers a variety of modes, e.g., direct imaging, polarimetry, slit spectroscopy, coronagraphy and spectro-imaging. The ESO PR Video Clips service to visitors to the ESO website provides "animated" illustrations of the ongoing work and events at the European Southern Observatory. The most recent clip was: ESO PR Video Clip 06/01 about observations of a binary star (8 October 2001). Information is also available on the web about other ESO videos.

Search for an exosphere in sodium and calcium in the transmission spectrum of exoplanet 55 Cancri e

NASA Astrophysics Data System (ADS)

Ridden-Harper, A. R.; Snellen, I. A. G.; Keller, C. U.; de Kok, R. J.; Di Gloria, E.; Hoeijmakers, H. J.; Brogi, M.; Fridlund, M.; Vermeersen, B. L. A.; van Westrenen, W.

2016-10-01

Context. The atmospheric and surface characterization of rocky planets is a key goal of exoplanet science. Unfortunately, the measurements required for this are generally out of reach of present-day instrumentation. However, the planet Mercury in our own solar system exhibits a large exosphere composed of atomic species that have been ejected from the planetary surface by the process of sputtering. Since the hottest rocky exoplanets known so far are more than an order of magnitude closer to their parent star than Mercury is to the Sun, the sputtering process and the resulting exospheres could be orders of magnitude larger and potentially detectable using transmission spectroscopy, indirectly probing their surface compositions. Aims: The aim of this work is to search for an absorption signal from exospheric sodium (Na) and singly ionized calcium (Ca+) in the optical transmission spectrum of the hot rocky super-Earth 55 Cancri e. Although the current best-fitting models to the planet mass and radius require a possible atmospheric component, uncertainties in the radius exist, making it possible that 55 Cancri e could be a hot rocky planet without an atmosphere. Methods: High resolution (R ~ 110 000) time-series spectra of five transits of 55 Cancri e, obtained with three different telescopes (UVES/VLT, HARPS/ESO 3.6 m and HARPS-N/TNG) were analysed. Targeting the sodium D lines and the calcium H and K lines, the potential planet exospheric signal was filtered out from the much stronger stellar and telluric signals, making use of the change of the radial component of the orbital velocity of the planet over the transit from -57 to +57 km s-1. Results: Combining all five transit data sets, we detect a signal potentially associated with sodium in the planet exosphere at a statistical significance level of 3σ. Combining the four HARPS transits that cover the calcium H and K lines, we also find a potential signal from ionized calcium (4.1σ). Interestingly, this latter signal originates from just one of the transit measurements - with a 4.9σ detection at this epoch. Unfortunately, due to the low significance of the measured sodium signal and the potentially variable Ca+ signal, we estimate the p-values of these signals to be too high (corresponding to <4σ) to claim unambiguous exospheric detections. By comparing the observed signals with artificial signals injected early in the analysis, the absorption by Na and Ca+ are estimated to be at a level of ~2.3 × 10-3 and ~7.0 × 10-2 respectively, relative to the stellar spectrum. Conclusions: If confirmed, the 3σ signal would correspond to an optically thick sodium exosphere with a radius of 5 R⊕, which is comparable to the Roche lobe radius of the planet. The 4.9σ detection of Ca+ in a single HARPS data set would correspond to an optically thick Ca+ exosphere approximately five times larger than the Roche lobe radius. If this were a real detection, it would imply that the exosphere exhibits extreme variability. Although no formal detection has been made, we advocate that probing the exospheres of hot super-Earths in this way has great potential, also knowing that Mercury's exosphere varies significantly over time. It may be a fast route towards the first characterization of the surface properties of this enigmatic class of planets. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 092.C-0178 and 288.C-5010 and the Telescopio Nazionale Galileo under programme CAT13B_33.

Chemical Characterization of the Inner Galactic bulge: North-South Symmetry

NASA Astrophysics Data System (ADS)

Nandakumar, G.; Ryde, N.; Schultheis, M.; Thorsbro, B.; Jönsson, H.; Barklem, P. S.; Rich, R. M.; Fragkoudi, F.

2018-05-01

While the number of stars in the Galactic bulge with detailed chemical abundance measurements is increasing rapidly, the inner Galactic bulge (|b| < 2°) remains poorly studied, due to heavy interstellar absorption and photometric crowding. We have carried out a high-resolution IR spectroscopic study of 72 M giants in the inner bulge using the CRIRES (ESO/VLT) facility. Our spectra cover the wavelength range of 2.0818 - 2.1444 μm with the resolution of R˜50,000 and have signal-to-noise ratio of 50-100. Our stars are located along the bulge minor axis at l = 0°, b = ±0°, ±1°, ±2°and +3°. Our sample was analysed in a homogeneous way using the most current K-band line list. We clearly detect a bimodal MDF with a metal-rich peak at ˜ +0.3 dex and a metal-poor peak at ˜ -0.5 dex, and no stars with [Fe/H] > +0.6 dex. The Galactic Center field reveals in contrast a mainly metal-rich population with a mean metallicity of +0.3 dex. We derived [Mg/Fe] and [Si/Fe] abundances which are consistent with trends from the outer bulge. We confirm for the supersolar metallicity stars the decreasing trend in [Mg/Fe] and [Si/Fe] as expected from chemical evolution models. With the caveat of a relatively small sample, we do not find significant differences in the chemical abundances between the Northern and the Southern fields, hence the evidence is consistent with symmetry in chemistry between North and South.

Feeling the Heat

NASA Astrophysics Data System (ADS)

2004-05-01

Successful "First Light" for the Mid-Infrared VISIR Instrument on the VLT Summary Close to midnight on April 30, 2004, intriguing thermal infrared images of dust and gas heated by invisible stars in a distant region of our Milky Way appeared on a computer screen in the control room of the ESO Very Large Telescope (VLT). These images mark the successful "First Light" of the VLT Imager and Spectrometer in the InfraRed (VISIR), the latest instrument to be installed on this powerful telescope facility at the ESO Paranal Observatory in Chile. The event was greeted with a mixture of delight, satisfaction and some relief by the team of astronomers and engineers from the consortium of French and Dutch Institutes and ESO who have worked on the development of VISIR for around 10 years [1]. Pierre-Olivier Lagage (CEA, France), the Principal Investigator, is content : "This is a wonderful day! A result of many years of dedication by a team of engineers and technicians, who can today be proud of their work. With VISIR, astronomers will have at their disposal a great instrument on a marvellous telescope. And the gain is enormous; 20 minutes of observing with VISIR is equivalent to a whole night of observing on a 3-4m class telescope." Dutch astronomer and co-PI Jan-Willem Pel (Groningen, The Netherlands) adds: "What's more, VISIR features a unique observing mode in the mid-infrared: spectroscopy at a very high spectral resolution. This will open up new possibilities such as the study of warm molecular hydrogen most likely to be an important component of our galaxy." PR Photo 16a/04: VISIR under the Cassegrain focus of the Melipal telescope PR Photo 16b/04: VISIR mounted behind the mirror of the Melipal telescope PR Photo 16c/04: Colour composite of the star forming region G333.6-0.2 PR Photo 16d/04: Colour composite of the Galactic Centre PR Photo 16e/04: The Ant Planetary Nebula at 12.8 μm PR Photo 16f/04: The starburst galaxy He2-10 at 11.3μm PR Photo 16g/04: High-resolution spectrum of G333.6-0.2 around 12.8μm PR Photo 16h/04: High-resolution spectrum of the Ant Planetary Nebula around 12.8μm From cometary tails to centres of galaxies The mid-infrared spectral region extends from a few to a few tens of microns in wavelength and provides a unique view of our Universe. Optical astronomy, that is astronomy at wavelengths to which our eyes are sensitive, is mostly directed towards light emitted by gas, be it in stars, nebulae or galaxies. Mid-Infrared astronomy, however, allows us to also detect solid dust particles at temperatures of -200 to +300 °C. Dust is very abundant in the universe in many different environments, ranging from cometary tails to the centres of galaxies. This dust also often totally absorbs and hence blocks the visible light reaching us from such objects. Red light, and especially infrared light, can propagate much better in dust clouds. Many important astrophysical processes occur in regions of high obscuration by dust, most notably star formation and the late stages of their evolution, when stars that have burnt nearly all their fuel shed much of their outer layers and dust grains form in their "stellar wind". Stars are born in so-called molecular clouds. The proto-stars feed from these clouds and are shielded from the outside by them. Infrared is a tool - very much as ultrasound is for medical inspections - for looking into those otherwise hidden regions to study the stellar "embryos". It is thus crucial to also observe the Universe in the infrared and mid-infrared. Unfortunately, there are also infrared-emitting molecules in the Earth's atmosphere, e.g. water vapour, Nitric Oxides, Ozone, Methane. Because of these gases, the atmosphere is completely opaque at certain wavelengths, except in a few "windows" where the Earth's atmosphere is transparent. Even in these windows, however, the sky and telescope emit radiation in the infrared to an extent that observing in the mid-infrared at night is comparable to trying to do optical astronomy in daytime. Ground-based infrared astronomers have thus become extremely adept at developing special techniques called "chopping' and "nodding" for detecting the extremely faint astronomical signals against this unwanted bright background [3]. VISIR: an extremely complex instrument VISIR - the VLT Imager and Spectrometer in the InfraRed - is a complex multi-mode instrument designed to operate in the 10 and 20 μm atmospheric windows, i.e. at wavelengths up to about 40 times longer than visible light and to provide images as well as spectra at a wide range of resolving power up to ~ 30.000. It can sample images down to the diffraction limit of the 8.2-m Melipal telescope (0.27 arcsec at 10 μm wavelength, i.e. corresponding to a resolution of 500 m on the Moon), which is expected to be reached routinely due to the excellent seeing conditions experienced for a large fraction of the time at the VLT [2]. Because at room temperature the metal and glass of VISIR would emit strongly at exactly the same wavelengths and would swamp any faint mid-infrared astronomical signals, the whole VISIR instrument is cooled to a temperature close to -250° C and its two panoramic 256x256 pixel array detectors to even lower temperatures, only a few degrees above absolute zero. It is also kept in a vacuum tank to avoid the unavoidable condensation of water and icing which would otherwise occur. The complete instrument is mounted on the telescope and must remain rigid to within a few thousandths of a millimetre as the telescope moves to acquire and then track objects anywhere in the sky. Needless to say, this makes for an extremely complex instrument and explains the many years needed to develop and bring it to the telescope on the top of Paranal. VISIR also includes a number of important technological innovations, most notably its unique cryogenic motor drive systems comprising integrated stepper motors, gears and clutches whose shape is similar to that of the box of the famous French Camembert cheese. VISIR is mounted on Melipal ESO PR Photo 16a/04 ESO PR Photo 16a/04 VISIR under the Cassegrain focus of the Melipal telescope [Preview - JPEG: 400 x 476 pix - 271k] [Normal - JPEG: 800 x 951 pix - 600k] ESO PR Photo 16b/04 ESO PR Photo 16b/04 VISIR mounted behind the mirror of the Melipal telescope [Preview - JPEG: 400 x 603 pix - 366k] [Normal - JPEG: 800 x 1206 pix - 945k] Caption: ESO PR Photo 16a/04 shows VISIR about to be attached at the Cassegrain focus of the Melipal telescope. On ESO PR Photo 16b/04, VISIR appears much smaller once mounted behind the enormous 8.2-m diameter mirror of the Melipal telescope. The fully integrated VISIR plus all the associated equipment (amounting to a total of around 8 tons) was air freighted from Paris to Santiago de Chile and arrived at the Paranal Observatory on 25th March after a subsequent 1500 km journey by road. Following tests to confirm that nothing had been damaged, VISIR was mounted on the third VLT telescope "Melipal" on April 27th. PR Photos 16a/04 and 16b/04 show the approximately 1.6 tons of VISIR being mounted at the Cassegrain focus, below the 8.2-m main mirror. First technical light on a star was achieved on April 29th, shortly after VISIR had been cooled down to its operating temperature. This allowed to proceed with the necessary first basic operations, including focusing the telescope, and tests. While telescope focusing was one of the difficult and frequent tasks faced by astronomers in the past, this is no longer so with the active optics feature of the VLT telescopes which, in principle, has to be focused only once after which it will forever be automatically kept in perfect focus. First images and spectra from VISIR ESO PR Photo 16c/04 ESO PR Photo 16c/04 Colour composite of the star forming region G333.6-0.2 [Preview - JPEG: 400 x 477 pix - 78k] [Normal - JPEG: 800 x 954 pix - 191k] ESO PR Photo 16d/04 ESO PR Photo 16d/04 Colour composite of the Galactic Centre [Preview - JPEG: 400 x 478 pix - 159k] [Normal - JPEG: 800 x 955 pix - 348k] Caption: ESO PR Photo 16c/04 is a colour composite image of the visually obscured G333.6-0.2 star-forming region at a distance of nearly 10,000 light-years in our Milky Way galaxy. This image was made by combining three digital images of the intensity of the infrared emission at wavelengths of 11.3μm (one of the Polycyclic Aromatic Hydrocarbon features, coded blue), 12.8 μm (an emission line of [NeII], coded green) and 19μm (warm dust emission, coded red). Each pixel subtends 0.127 arcsec and the total field is ~ 33 x 33 arcsec with North at the top and East to the left. The total integration times were 13 seconds at the shortest and 35 seconds at the longer wavelengths. The brighter spots locate regions where the dust, which obscures all the visible light, has been heated by recently formed stars. ESO PR Photo 16d/04 shows another colour composite, this time of the Galactic Centre at a distance of about 30,000 light-years. It was made by combining images in filters centred at 8.6μm (Polycyclic Aromatic Hydrocarbon molecular feature - coded blue), 12.8μm ([NeII] - coded green) and 19.5μm (coded red). Each pixel subtends 0.127 arcsec and the total field is ~ 33 x 33 arcsec with North at the top and East to the left. Total integration times were 300, 160 and 300 s for the 3 filters, respectively. This region is very rich, full of stars, dust, ionised and molecular gas. One of the scientific goals will be to detect and monitor the signal from the black hole at the centre of our galaxy. ESO PR Photo 16e/04 ESO PR Photo 16e/04 The Ant Planetary Nebula at 12.8 μm [Preview - JPEG: 400 x 477 pix - 77k] [Normal - JPEG: 800 x 954 pix - 182k] Caption: ESO PR Photo 16e/04 is an image of the "Ant" Planetary Nebula (Mz3) in the narrow-band filter centred at wavelength 12.8 μm. The scale is 0.127 arcsec/pixel and the total field-of-view is 33 x 33 arcsec, with North at the top and East to the left. The total integration time was 200 seconds. Note the diffraction rings around the central star which confirm that the maximum spatial resolution possible with the 8.2-m telescope is being achieved. ESO PR Photo 16f/04 ESO PR Photo 16f/04 The starburst galaxy He2-10 at 11.3μm [Preview - JPEG: 400 x 477 pix - 69k] [Normal - JPEG: 800 x 954 pix - 172k] Caption: ESO PR Photo 16f/04 is an image at wavelength 11.3 μm of the "nearby" (distance about 30 million light-years) blue compact galaxy He2-10, which is actively forming stars. The scale is 0.127 arcsec per pixel and the full field covers 15 x 15 arcsec with North at the top and East on the left. The total integration time for this observation is one hour. Several star forming regions are detected, as well as a diffuse emission, which was unknown until these VISIR observations. The star-forming regions on the left of the image are not visible in optical images. ESO PR Photo 16g/04 ESO PR Photo 16g/04 High-resolution spectrum of G333.6-0.2 around 12.8 μm [Preview - JPEG: 652 x 400 pix - 123k] [Normal - JPEG: 1303 x 800 pix - 277k] Caption: ESO PR Photo 16g/04 is a reproduction of a high-resolution spectrum of the Ne II line (ionised Neon) at 12.8135 μm of the star-forming region G333.6-0.2 shown in ESO PR Photo 16c/04. This spectrum reveals the complex motions of the ionized gas in this region. The images are 256 x 256 frames of 50 x 50 micron pixels. The "field" direction is horizontal, with total slit length of 32.5 arcsec; North is left and South is to the right. The dispersion direction is vertical, with the wavelength increasing downward. The total integration time was 80 sec. ESO PR Photo 16h/04 ESO PR Photo 16h/04 High-resolution spectrum of the Ant nebula around 12.8 μm [Preview - JPEG: 610 x 400 pix - 354k] [Normal - JPEG: 1219 x 800 pix - 901k] Caption: ESO PR Photo 16h/04 is a reproduction of a high-resolution spectrum of the Ne II line (ionised Neon) at 12.8135 microns of the Ant Planetary Nebula, also known as Mz-3, shown in ESO PR Photo 16d/04. The technical details are similar to ESO PR Photo 16g/04. The total integration time was 120 sec. The photos above resulted from some of the first observational tests with VISIR. PR Photo 16c/04 shows the scientific "First Light" image, obtained one day later on April 30th, of a visually obscured star forming region nearly 10,000 light-years away in our galaxy, the Milky Way. The picture shown here is a false-colour image made by combining three digital images of the intensity of the infrared emission from this region at wavelengths of 11.3 μm (one of the Polycyclic Aromatic Hydrocarbon - PAH - features), 12.8 μm (an emission line of ionised neon) and 19 μm (cool dust emission). Ten times sharper Until now, an elegant way to avoid the problems caused by the emission and absorption of the atmosphere was to fly infrared telescopes on satellites as was done in the highly successful IRAS and ISO missions and currently the Spitzer observatory. For both technical and cost reasons, however, such telescopes have so far been limited to only 60-85 cm in diameter. While very sensitive therefore, the spatial resolution (sharpness) delivered by these telescopes is 10 times worse than that of the 8.2-m diameter VLT telescopes. They have also not been equipped with the very high spectral resolution capability, a feature of the VISIR instrument, which is thus expected to remain the instrument of choice for a wide range of studies for many years to come despite the competition from space. More information A corresponding [1]: The consortium of institutes responsible for building the VISIR instrument under contract to ESO comprises the CEA/DSM/DAPNIA, Saclay, France - led by the Principal Investigator (PI), Pierre-Olivier Lagage and the Netherlands Foundation for Research in Astronomy/ASTRON - (Dwingeloo, The Netherlands) with Jan-Willem Pel from Groningen University as Co-PI for the spectrometer. [2]: Stellar radiation on its way to the observer is also affected by the turbulence of the Earth's atmosphere. This is the effect which makes the stars twinkle for the human eye. While the general public enjoys this phenomenon as something that makes the night sky interesting and may be entertaining, the twinkling is a major concern for amateur and professional astronomers, as it smears out the optical images. Infrared radiation is less affected by this effect. Therefore an instrument like VISIR can make full use of the extremely high optical quality of modern telescopes, like the VLT. [3]: Observations from the ground at wavelengths of 10 to 20 μm are particularly difficult because this is the wavelength region in which both the telescope and the atmosphere emits most strongly. In order to minimize its effect, the images shown here were made by tilting the telescope secondary mirror every few seconds (chopping) and the whole telescope every minute (nodding) so that this unwanted telescope and sky background emission could be measured and subtracted from the science images faster than it varies.

Latitudinal Variation of Germane in Jovian Atmosphere

NASA Astrophysics Data System (ADS)

Hyder, A.; Lunine, J. I.; Wang, D.

2017-12-01

Wang et al (2016) presented a chemical-dynamical model for Jupiter's atmosphere that predicted abundances of Germane and other disequilibrium species as a function of latitude, under the assumption that only vertical transport is relevant and no horizontal advection occurs. The model disagrees with the latitudinal distributions derived from high-resolution spectral data acquired from the CRIRES instrument at the VLT as described in Giles et al. 2017. Wang et al. 2016 predicts a maximum molar abundance of Germane at (0.7±0.2) ppb with depletion at higher latitudes, while Giles et al. 2017 predicts a constant molar abundance of Germane at 0.58 ppb with no depletion. We explore an empirical horizontal term for the diffusive transport coefficient as a function of latitude, which does not produce a satisfactory result unless highly arbitrary variations of the vertical eddy mixing term as a function of latitude are imposed. We therefore also explore a horizontal wind from the equator that produces a constant latitudinal profile by transporting Germane-rich gas to the poles, effectively producing a Hadley cell. References: Giles, R. S., Fletcher, L. N., & Irwin, P. G. (2017). Latitudinal variability in Jupiter's tropospheric disequilibrium species: GeH 4, AsH 3 and PH 3. Icarus, 289, 254-269. Wang, D., Lunine, J.I., Mousis, O., 2016. Modeling the disequilibrium species for Jupiter and Saturn: implications for Juno and Saturn entry probe. Icarus 276, 21-38.

Chemical analysis of eight giant stars of the globular cluster NGC 6366

NASA Astrophysics Data System (ADS)

Puls, Arthur A.; Alves-Brito, Alan; Campos, Fabíola; Dias, Bruno; Barbuy, Beatriz

2018-05-01

The metal-rich Galactic globular cluster NGC 6366 is the fifth closest to the Sun. Despite its interest, it has received scarce attention, and little is known about its internal structure. Its kinematics suggests a link to the halo, but its metallicity indicates otherwise. We present a detailed chemical analysis of eight giant stars of NGC 6366, using high-resolution and high-quality spectra (R > 40 000, S/N > 60) obtained at the VLT (8.2 m) and CFHT (3.6 m) telescopes. We attempted to characterize its chemistry and to search for evidence of multiple stellar populations. The atmospheric parameters were derived using the method of excitation and ionization equilibrium of Fe I and Fe II lines and from those atmospheric parameters we calculated the abundances for other elements and found that none of the elements measured presents star-to-star variation greater than the uncertainties. We compared the derived abundances with those of other globular clusters and field stars available in the literature. We determined a mean [Fe/H] = -0.60 ± 0.03 for NGC 6366 and found some similarity of this object with M 71, another inner halo globular cluster. The Na-O anticorrelation extension is short and no star-to-star variation in Al is found. The presence of second generation stars is not evident in NGC 6366.

Deep Photometry of Galaxies in the VEGAS Survey: The Case of NGC 4472

NASA Astrophysics Data System (ADS)

Spavone, M.

The VST-VEGAS project is aimed at observing and studying a rich sample of nearby early-type galaxies in order to systematically characterize their properties over a wide baseline of sizes and out to the faint outskirts where data are rather scarce so far. The external regions of galaxies more easily retain signatures about the formation and evolution mechanisms which shaped them, as their relaxation time are longer, and they are more weakly influenced by processes such as mergers, secular evolution, central black hole activity, and supernova feedback on the ISM, which tend to level age and metallicity gradients. The collection of a wide photometric dataset of a large number of galaxies in various environmental conditions, may help to shed light on these questions. To this end VEGAS exploits the potential of the VLT Survey Telescope (VST) which provides high quality images of 1 deg2 field of view in order to satisfy both the requirement of high resolution data and the need of studying nearby, and thus large, objects. We present a detailed study of the surface photometry of the elliptical galaxy NGC4472 and of smaller ETGs in its field, performed by using new g and i bands images to constrain the formation history of this nearby giant galaxy, and to investigate the presence of very faint substructures in its surroundings.

ESO and Fokker Space Sign Contract about VLTI Delay Line

NASA Astrophysics Data System (ADS)

1998-03-01

The European Southern Observatory is building the world's largest optical telescope, the Very Large Telescope (VLT) , at the ESO Paranal Observatory in Chile. The VLT consists of four 8.2-m unit telescopes and several smaller, moveable Auxiliary Telescopes. When coupled as the giant VLT Interferometer (VLTI) , they will together provide the sharpest images ever obtained by any optical telescope. It will in principle be able to see an astronaut on the surface of the Moon, 400,000 km away. The VLTI Delay Lines Fokker Space (Leiden, The Netherlands) has been awarded a contract for the delivery of the Delay Line of the VLTI. This is a mechanical-optical system that will compensate the optical path differences of the light beams from the individual telescopes. Such a system is necessary to ensure that the light from all telescopes arrive in the same phase at the focal point of the interferometer. Otherwise, the very sharp interferometric images cannot be obtained. ESO PR Photo 08/98 [JPEG, 102k] Schematic representation of the VLTI Delay Line, showing the retro-reflector on its moving base. For more details, please consult the technical explanation below. This highly accurate system will be developed in close co-operation with the Dutch institute TNO-TPD (Netherlands Organization for Applied Scientific Research - Institute of Applied Physics) . The most innovative feature of the Delay Line is the new control strategy, a two-stage control system, based on linear motor technology, combined with high accuracy piezo-electric control elements. This enables the system to position the so-called cat's eye reflector system with an accuracy of only a few nanometers (millionth of a millimetre (nm)) over a stroke length of 60 metres. Within radio astronomy, interferometric techniques have been applied by Dutch astronomers since many years. They will now be able to contribute with their extensive knowledge of such systems to the next generation of astronomical interferometric instruments within the present collaboration. About Fokker Space Fokker Space is the largest company in the Dutch space industry. It is based in Leiden, has 481 employees and an operating income of 220 million Netherlands Guilders in 1996. Fokker Space is mainly active in the field of solar arrays, launcher structures, thermal products, instruments and simulators. It also plays a key role in the development of robotics and is responsible as a prime contractor for the European Robotics Arm (ERA) to be used on the International Space Station. Fokker Space is well embedded in the Dutch aerospace infrastructure, thanks to close relations with the Dutch Space Agency (NIVR) , the National Aerospace Laboratory (NLR) , the Delft University of Technology and other Dutch space industries and institutes like TNO-TPD (Netherlands Organization for Applied Scientific Research - Institute of Applied Physics) . Fokker Space has also entered into strategic partnerships in Europe, Russia and North America. These facts, combined with the long lasting relation with the European Space Agency ESA and with the Dutch Government imply that Fokker Space has secured a solid base for continuation of its business far into the next millennium. Some technical details about the VLTI Delay Line The VLT Delay Line forms an essential part of the VLT Interferometer (VLTI) . It represents the current limit of high technology in this field and includes many innovative features. Some of the technical details are given below. In order to enable a useful combination of the light beams from the individual telescopes of the VLT (that is, to produce interferometric fringes at the focal point), the optical path length differences must be corrected by the Delay Line system. These differences are caused by: * the static geometric path length difference between the telescopes in a certain configuration; * the diurnal motion of the astronomical source during observation due to Earth's rotation; and * the rapid path length variations due to atmospheric disturbances and/or mechanical vibrations along the optical path length. The VLTI Delay Line system consists of a retro-reflector mounted on a moving base. The optical design of this `Cat's Eye' is of the Ritchey-Chretien type that reflects the light very effectively. For this particular application, the `Cat's Eye' is not a corner cube with 3 perpendicular mirrors as is the case in the reflectors on cars and bicycles; it is in fact a telescope with a mirror at the focus that sends a light beam back in a direction parallel to the one it came from. The moving base enables the Cat's Eye to travel along a 60 metres long rail track, thereby providing optical path difference corrections of up to 120 metres, as required for the VLT telescope configurations at Paranal. The necessary, rapid path length corrections are performed by a fine positioning loop in which a piezo crystal (mounted on the backside of the Variable Curvature Mirror M3) is used to correct the fast optical path variations as measured by a Fringe Sensing Unit (FSU). The latter provides a signal to the Delay Line system via a fast link to the Delay Line Local Control Unit. An optical datalink to the Cat's Eye on the carriage ensures the transfer of data to the Piezo controller. The carriage is driven by a Linear Induction Motor. The coils for the motor are mounted on the floor of the Delay Line Long Support Bench and the magnets are mounted on the bottom of the carriage. The metrology system (to measure the carriage position) consists of a laser-interferometer whose beam follows the same path as the light beams from the telescopes via the Cat's Eye. The main design parameters are shown here: Optical Path range above 120 m Optical Path resolution better than 20 nm Optical Path stability better than 14 nm over any 0.01 sec (in the visible spectral range) better than 50 nm over any 0.05 sec (in Near-IR spectral range) better than 225 nm over any 0.3 sec (in Thermal-IR spectral range) Absolute position repeatability 50 micron (over full length - 60 metres) 1 micron (over observation length - 3 metres) Maximum velocity: 0.5 m/sec Maximum velocity errors 1 micron/sec Maximum power dissipation 15 Watts Note: [1] This Press Release is issued jointly by ESO and Fokker Space on the occasion of the signature of the contract for the VLTI Delay System which takes place at Fokker Space in Leiden (The Netherlands) today. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Eccentricity in planetary systems and the role of binarity. Sample definition, initial results, and the system of HD 211847

NASA Astrophysics Data System (ADS)

Moutou, C.; Vigan, A.; Mesa, D.; Desidera, S.; Thébault, P.; Zurlo, A.; Salter, G.

2017-06-01

We explore the multiplicity of exoplanet host stars with high-resolution images obtained with VLT/SPHERE. Two different samples of systems were observed: one containing low-eccentricity outer planets, and the other containing high-eccentricity outer planets. We find that 10 out of 34 stars in the high-eccentricity systems are members of a binary, while the proportion is 3 out of 27 for circular systems. Eccentric-exoplanet hosts are, therefore, significantly more likely to have a stellar companion than circular-exoplanet hosts. The median magnitude contrast over the 68 data sets is 11.26 and 9.25, in H and K, respectively, at 0.30 arcsec. The derived detection limits reveal that binaries with separations of less than 50 au are rarer for exoplanet hosts than for field stars. Our results also imply that the majority of high-eccentricity planets are not embedded in multiple stellar systems (24 out of 34), since our detection limits exclude the presence of a stellar companion. We detect the low-mass stellar companions of HD 7449 and HD 211847, both members of our high-eccentricity sample. HD 7449B was already detected and our independent observation is in agreement with this earlier work. HD 211847's substellar companion, previously detected by the radial velocity method, is actually a low-mass star seen face-on. The role of stellar multiplicity in shaping planetary systems is confirmed by this work, although it does not appear as the only source of dynamical excitation. Based on observations collected with SPHERE on the Very Large Telescope (ESO, Chile).

High-cadence, High-contrast Imaging for Exoplanet Mapping: Observations of the HR 8799 Planets with VLT/SPHERE Satellite-spot-corrected Relative Photometry

NASA Astrophysics Data System (ADS)

Apai, Dániel; Kasper, Markus; Skemer, Andrew; Hanson, Jake R.; Lagrange, Anne-Marie; Biller, Beth A.; Bonnefoy, Mickaël; Buenzli, Esther; Vigan, Arthur

2016-03-01

Time-resolved photometry is an important new probe of the physics of condensate clouds in extrasolar planets and brown dwarfs. Extreme adaptive optics systems can directly image planets, but precise brightness measurements are challenging. We present VLT/SPHERE high-contrast, time-resolved broad H-band near-infrared photometry for four exoplanets in the HR 8799 system, sampling changes from night to night over five nights with relatively short integrations. The photospheres of these four planets are often modeled by patchy clouds and may show large-amplitude rotational brightness modulations. Our observations provide high-quality images of the system. We present a detailed performance analysis of different data analysis approaches to accurately measure the relative brightnesses of the four exoplanets. We explore the information in satellite spots and demonstrate their use as a proxy for image quality. While the brightness variations of the satellite spots are strongly correlated, we also identify a second-order anti-correlation pattern between the different spots. Our study finds that KLIP reduction based on principal components analysis with satellite-spot-modulated artificial-planet-injection-based photometry leads to a significant (˜3×) gain in photometric accuracy over standard aperture-based photometry and reaches 0.1 mag per point accuracy for our data set, the signal-to-noise ratio of which is limited by small field rotation. Relative planet-to-planet photometry can be compared between nights, enabling observations spanning multiple nights to probe variability. Recent high-quality relative H-band photometry of the b-c planet pair agrees to about 1%.

VizieR Online Data Catalog: MIR view of polar dust emission in local AGNs (Asmus+, 2016)

NASA Astrophysics Data System (ADS)

Asmus, D.; Honig, S. F.; Gandhi, P.

2018-02-01

The parent sample for this work is the AGN MIR atlas of 253 objects (Asmus et al. 2014, J/MNRAS/439/1648). The optical classifications and distances (using the same cosmology) are adopted from that work. We furthermore use the nuclear MIR flux measurements from Asmus et al. (2014, J/MNRAS/439/1648). These are extracted from ground-based multi-filter photometry obtained with the instruments VLT/VISIR (Lagage et al. 2004Msngr.117...12L), Gemini/T-ReCS (Telesco et al. 1998SPIE.3354..534T), Gemini/Michelle (Glasse et al. 1997SPIE.2871.1197G), and Subaru/COMICS (Kataza et al. 2000SPIE.4008.1144K), with an angular resolution of the order of 0.35" or 120 pc for the median sample distance of 72 Mpc at 12 μm. (2 data files).

ESPRESSO: the ultimate rocky exoplanets hunter for the VLT

NASA Astrophysics Data System (ADS)

Mégevand, Denis; Zerbi, Filippo M.; Cabral, Alexandre; Di Marcantonio, Paolo; Amate, Manuel; Pepe, Francesco; Cristiani, Stefano; Rebolo, Rafael; Santos, Nuno C.; Dekker, Hans; Abreu, Manuel; Affolter, Michael; Avila, Gerardo; Baldini, Veronica; Bristow, Paul; Broeg, Christopher; Carvas, Pedro; Cirami, Roberto; Coelho, João.; Comari, Maurizio; Conconi, Paolo; Coretti, Igor; Cupani, Guido; D'Odorico, Valentina; De Caprio, Vincenzo; Delabre, Bernard; Figueira, Pedro; Fleury, Michel; Fragoso, Ana; Genolet, Ludovic; Gomes, Ricardo; Gonzalez Hernandez, Jonay; Hughes, Ian; Iwert, Olaf; Kerber, Florian; Landoni, Marco; Lima, Jorge; Lizon, Jean-Louis; Lovis, Christophe; Maire, Charles; Mannetta, Marco; Martins, Carlos; Moitinho, André; Molaro, Paolo; Monteiro, Manuel; Rasilla, José Luis; Riva, Marco; Santana Tschudi, Samuel; Santin, Paolo; Sosnowska, Danuta; Sousa, Sergio; Spanò, Paolo; Tenegi, Fabio; Toso, Giorgio; Vanzella, Eros; Viel, Matteo; Zapatero Osorio, Maria Rosa

2012-09-01

ESPRESSO, the VLT rocky exoplanets hunter, will combine the efficiency of modern echelle spectrograph with extreme radial-velocity precision. It will be installed at Paranal on ESO's VLT in order to achieve a gain of two magnitudes with respect to its predecessor HARPS, and the instrumental radial-velocity precision will be improved to reach 10 cm/s level. We have constituted a Consortium of astronomical research institutes to fund, design and build ESPRESSO on behalf of and in collaboration with ESO, the European Southern Observatory. The project has passed the preliminary design review in November 2011. The spectrograph will be installed at the so-called "Combined Coudé Laboratory" of the VLT, it will be linked to the four 8.2 meters Unit Telescopes (UT) through four optical "Coudé trains" and will be operated either with a single telescope or with up to four UTs. In exchange of the major financial and human effort the building Consortium will be awarded with guaranteed observing time (GTO), which will be invested in a common scientific program. Thanks to its characteristics and the ability of combining incoherently the light of 4 large telescopes, ESPRESSO will offer new possibilities in many fields of astronomy. Our main scientific objectives are, however, the search and characterization of rocky exoplanets in the habitable zone of quiet, near-by G to M-dwarfs, and the analysis of the variability of fundamental physical constants. In this paper, we present the ambitious scientific objectives, the capabilities of ESPRESSO, the technical solutions for the system and its subsystems, enlightening the main differences between ESPRESSO and its predecessors. The project aspects of this facility are also described, from the consortium and partnership structure to the planning phases and milestones.

Characterization of multiple lithologies within the lunar feldspathic regolith breccia meteorite Northeast Africa 001

NASA Astrophysics Data System (ADS)

Snape, Joshua F.; Joy, Katherine H.; Crawford, Ian A.

2011-09-01

Abstract- Lunar meteorite Northeast Africa (NEA) 001 is a feldspathic regolith breccia. This study presents the results of electron microprobe and LA-ICP-MS analyses of a section of NEA 001. We identify a range of lunar lithologies including feldspathic impact melt, ferroan noritic anorthosite and magnesian feldspathic clasts, and several very-low titanium (VLT) basalt clasts. The largest of these basalt clasts has a rare earth element (REE) pattern with light-REE (LREE) depletion and a positive Euanomaly. This clast also exhibits low incompatible trace element (ITE) concentrations (e.g., <0.1 ppm Th, <0.5 ppm Sm), indicating that it has originated from a parent melt that did not assimilate KREEP material. Positive Eu-anomalies and such low-ITE concentrations are uncharacteristic of most basalts returned by the Apollo and Luna missions, and basaltic lunar meteorite samples. We suggest that these features are consistent with the VLT clasts crystallizing from a parent melt which was derived from early mantle cumulates that formed prior to the separation of plagioclase in the lunar magma ocean, as has previously been proposed for some other lunar VLT basalts. Feldspathic impact melts within the sample are found to be more mafic than estimations for the composition of the upper feldspathic lunar crust, suggesting that they may have melted and incorporated material from the lower lunar crust (possibly in large basin-forming events). The generally feldspathic nature of the impact melt clasts, lack of a KREEP component, and the compositions of the basaltic clasts, leads us to suggest that the meteorite has been sourced from the Outer-Feldspathic Highlands Terrane (FHT-O), probably on the lunar farside and within about 1000 km of sources of both Low-Ti and VLT basalts, the latter possibly existing as cryptomaria deposits.

Variability of OH rotational temperatures on time scales from hours to 15 years by kinetic temperature variations, emission layer changes, and non-LTE effects

NASA Astrophysics Data System (ADS)

Noll, Stefan

2016-07-01

Rotational temperatures derived from hydroxyl (OH) line emission are frequently used to study atmospheric temperatures at altitudes of about 87 km. While the measurement only requires intensities of a few bright lines of an OH band, the interpretation can be complicated. Ground-based temperatures are averages for the entire, typically 8 km wide emission layer. Variations in the rotational temperature are then caused by changes of the kinetic temperature and the OH emission profile. The latter can also be accompanied by differences in the layer-averaged efficiency of the thermalisation of the OH rotational level populations. Since this especially depends on the frequency of collisions with O_2, which is low at high altitudes, the non-local thermodynamic equilibrium (non-LTE) contribution to the measured temperatures can be significant and variable. In order to understand the impact of the different sources of OH rotational temperature variations from time scales of hours to a solar cycle, we have studied spectra from the astronomical echelle spectrographs X-shooter and UVES located at Cerro Paranal in Chile. While the X-shooter data spanning 3.5 years allowed us to measure temperatures for 25 OH and two O_2 bands, the UVES spectra cover no more than 10 OH bands simultaneously but a period of about 15 years. These data have been complemented by kinetic temperature and OH and O_2 emission profiles from the multi-channel radiometer SABER on the TIMED satellite. Taking the O_2 and SABER kinetic temperatures as reference and considering the different band-dependent emission profiles, we could evaluate the contribution of non-LTE effects to the measured OH rotational temperatures depending on line set, band, and time. Non-LTE contributions are significant for most bands and can exceed 10 K. The amplitudes of their average nocturnal and seasonal variation are of the order of 1 to 2 K.

Fiber IFU unit for the second generation VLT spectrograph KMOS

NASA Astrophysics Data System (ADS)

Tomono, Daigo; Weisz, Harald; Hofmann, Reiner

2003-03-01

KMOS is a cryogenic multi-object near-infrared spectrograph for the VLT. It will be equipped with about 20 deployable integral field units (IFUs) which can be positioned anywhere in the 7.2 arcmin diameter field o the VLT Nasmyth focus by a cryogenic robot. We describe IFUs using micro lens arrays and optical fibers to arrange the two-dimensional fields from the IFUs on the spectrograph entrance slit. Each micro-lens array is mounted in a spider arm which also houses the pre-optics with a cold stop. The spider arms are positioned by a cryogenic robot which is built around the image plane. For the IFUs, two solutions are considered: monolithic mirco-lens arrays with fibers attached to the back where the entrance pupil is imaged, and tapered fibers with integrated lenses which are bundled together to form a lens array. The flexibility of optical fibers relaxes boundary conditions for integration of the instrument components. On the other hand, FRD and geometric characteristics of optical fibers leads to higher AΩ accepted by the spectrograph. Conceptual design of the instrument is presented as well as advantages and disadvantages of the fiber IFUs.

VIMOS Instrument Control Software Design: an Object Oriented Approach

NASA Astrophysics Data System (ADS)

Brau-Nogué, Sylvie; Lucuix, Christian

2002-12-01

The Franco-Italian VIMOS instrument is a VIsible imaging Multi-Object Spectrograph with outstanding multiplex capabilities, allowing to take spectra of more than 800 objects simultaneously, or integral field spectroscopy mode in a 54x54 arcsec area. VIMOS is being installed at the Nasmyth focus of the third Unit Telescope of the European Southern Observatory Very Large Telescope (VLT) at Mount Paranal in Chile. This paper will describe the analysis, the design and the implementation of the VIMOS Instrument Control System, using UML notation. Our Control group followed an Object Oriented software process while keeping in mind the ESO VLT standard control concepts. At ESO VLT a complete software library is available. Rather than applying waterfall lifecycle, ICS project used iterative development, a lifecycle consisting of several iterations. Each iteration consisted in : capture and evaluate the requirements, visual modeling for analysis and design, implementation, test, and deployment. Depending of the project phases, iterations focused more or less on specific activity. The result is an object model (the design model), including use-case realizations. An implementation view and a deployment view complement this product. An extract of VIMOS ICS UML model will be presented and some implementation, integration and test issues will be discussed.

Spectroscopic analyses on interaction of o-Vanillin- D-Phenylalanine, o-Vanillin- L-Tyrosine and o-Vanillin- L-Levodopa Schiff Bases with bovine serum albumin (BSA)

NASA Astrophysics Data System (ADS)

Gao, Jingqun; Guo, Yuwei; Wang, Jun; Wang, Zhiqiu; Jin, Xudong; Cheng, Chunping; Li, Ying; Li, Kai

2011-04-01

In this work, three o-Vanillin Schiff Bases (o-VSB: o-Vanillin- D-Phenylalanine (o-VDP), o-Vanillin- L-Tyrosine (o-VLT) and o-Vanillin- L-Levodopa (o-VLL)) with alanine constituent were synthesized by direct reflux method in ethanol solution, and then were used to study the interaction to bovine serum albumin (BSA) molecules by fluorescence spectroscopy. Based on the fluorescence quenching calculation, the bimolecular quenching constant ( Kq), apparent quenching constant ( Ksv), effective binding constant ( KA) and corresponding dissociation constant ( KD) as well as binding site number ( n) were obtained. In addition, the binding distance ( r) was also calculated according to Foster's non-radioactive energy transfer theory. The results show that these three o-VSB can efficiently bind to BSA molecules, but the binding array order is o-VDP-BSA > o-VLT-BSA > o-VLL-BSA. Synchronous fluorescence spectroscopy indicates that the o-VDP is more accessibility to tryptophan (Trp) residues of BSA molecules than to tyrosine (Tyr) residues. Nevertheless, the o-VLT and o-VLL are more accessibility to Tyr residues than to Trp residues.

Spectroscopic analyses on interaction of o-Vanillin-D-Phenylalanine, o-Vanillin-L-Tyrosine and o-Vanillin-L-Levodopa Schiff Bases with bovine serum albumin (BSA).

PubMed

Gao, Jingqun; Guo, Yuwei; Wang, Jun; Wang, Zhiqiu; Jin, Xudong; Cheng, Chunping; Li, Ying; Li, Kai

2011-04-01

In this work, three o-Vanillin Schiff Bases (o-VSB: o-Vanillin-D-Phenylalanine (o-VDP), o-Vanillin-L-Tyrosine (o-VLT) and o-Vanillin-L-Levodopa (o-VLL)) with alanine constituent were synthesized by direct reflux method in ethanol solution, and then were used to study the interaction to bovine serum albumin (BSA) molecules by fluorescence spectroscopy. Based on the fluorescence quenching calculation, the bimolecular quenching constant (K(q)), apparent quenching constant (K(sv)), effective binding constant (K(A)) and corresponding dissociation constant (K(D)) as well as binding site number (n) were obtained. In addition, the binding distance (r) was also calculated according to Foster's non-radioactive energy transfer theory. The results show that these three o-VSB can efficiently bind to BSA molecules, but the binding array order is o-VDP-BSA>o-VLT-BSA>o-VLL-BSA. Synchronous fluorescence spectroscopy indicates that the o-VDP is more accessibility to tryptophan (Trp) residues of BSA molecules than to tyrosine (Tyr) residues. Nevertheless, the o-VLT and o-VLL are more accessibility to Tyr residues than to Trp residues. Copyright © 2010 Elsevier B.V. All rights reserved.

Lunar mare volcanism: Mixing of distinct, mantle source regions with KREEP-like component

NASA Technical Reports Server (NTRS)

Shervais, John W.; Vetter, Scott K.

1993-01-01

Mare basalts comprise less than 1% of the lunar crust, but they constitute our primary source of information on the moon's upper mantle. Compositional variations between mare basalt suites reflect variations in the mineralogical and geochemical composition of the lunar mantle which formed during early lunar differentiation (4.5-4.4 AE). Three broad suites of mare basalt are recognized: very low-Ti (VLT) basalts with TiO2 less than 1 wt%, low-Ti basalts with TiO2 = 2-4 wt%, and high-Ti basalts with TiO2 = 10-14 wt%. Important subgroups include the Apollo 12 ilmenite basalts (TiO2 = 5-6 wt%), aluminous low-Ti mare basalts (TiO2 = 2-4 wt%, Al2O3 = 10-14 wt%), and the newly discovered Very High potassium (VHK) aluminous low-Ti basalts, with K2O = 0.4-1.5 wt%. The mare basalt source region has geochemical characteristics complementary to the highlands crust and is generally thought to consist of mafic cumulates from the magma ocean which formed the felsic crust by feldspar flotation. The progressive enrichment of mare basalts in Fe/Mg, alkalis, and incompatible trace elements in the sequence VLT basalt yields low-Ti basalt yields high-Ti basalt is explained by the remelting of mafic cumulates formed at progressively shallower depths in the evolving magma ocean. This model is also consistent with the observed decrease in compatible element concentrations and the progressive increase in negative Eu anomalies.

Sharper and Deeper Views with MACAO-VLTI

NASA Astrophysics Data System (ADS)

2003-05-01

"First Light" with Powerful Adaptive Optics System for the VLT Interferometer Summary On April 18, 2003, a team of engineers from ESO celebrated the successful accomplishment of "First Light" for the MACAO-VLTI Adaptive Optics facility on the Very Large Telescope (VLT) at the Paranal Observatory (Chile). This is the second Adaptive Optics (AO) system put into operation at this observatory, following the NACO facility ( ESO PR 25/01 ). The achievable image sharpness of a ground-based telescope is normally limited by the effect of atmospheric turbulence. However, with Adaptive Optics (AO) techniques, this major drawback can be overcome so that the telescope produces images that are as sharp as theoretically possible, i.e., as if they were taken from space. The acronym "MACAO" stands for "Multi Application Curvature Adaptive Optics" which refers to the particular way optical corrections are made which "eliminate" the blurring effect of atmospheric turbulence. The MACAO-VLTI facility was developed at ESO. It is a highly complex system of which four, one for each 8.2-m VLT Unit Telescope, will be installed below the telescopes (in the Coudé rooms). These systems correct the distortions of the light beams from the large telescopes (induced by the atmospheric turbulence) before they are directed towards the common focus at the VLT Interferometer (VLTI). The installation of the four MACAO-VLTI units of which the first one is now in place, will amount to nothing less than a revolution in VLT interferometry . An enormous gain in efficiency will result, because of the associated 100-fold gain in sensitivity of the VLTI. Put in simple words, with MACAO-VLTI it will become possible to observe celestial objects 100 times fainter than now . Soon the astronomers will be thus able to obtain interference fringes with the VLTI ( ESO PR 23/01 ) of a large number of objects hitherto out of reach with this powerful observing technique, e.g. external galaxies. The ensuing high-resolution images and spectra will open entirely new perspectives in extragalactic research and also in the studies of many faint objects in our own galaxy, the Milky Way. During the present period, the first of the four MACAO-VLTI facilties was installed, integrated and tested by means of a series of observations. For these tests, an infrared camera was specially developed which allowed a detailed evaluation of the performance. It also provided some first, spectacular views of various celestial objects, some of which are shown here. PR Photo 12a/03 : View of the first MACAO-VLTI facility at Paranal PR Photo 12b/03 : The star HIC 59206 (uncorrected image). PR Photo 12c/03 : HIC 59206 (AO corrected image) PR Photo 12e/03 : HIC 69495 (AO corrected image) PR Photo 12f/03 : 3-D plot of HIC 69495 images (without and with AO correction) PR Photo 12g/03 : 3-D plot of the artificially dimmed star HIC 74324 (without and with AO correction) PR Photo 12d/03 : The MACAO-VLTI commissioning team at "First Light" PR Photo 12h/03 : K-band image of the Galactic Center PR Photo 12i/03 : K-band image of the unstable star Eta Carinae PR Photo 12j/03 : K-band image of the peculiar star Frosty Leo MACAO - the Multi Application Curvature Adaptive Optics facility ESO PR Photo 12a/03 ESO PR Photo 12a/03 [Preview - JPEG: 408 x 400 pix - 56k [Normal - JPEG: 815 x 800 pix - 720k] Captions : PR Photo 12a/03 is a front view of the first MACAO-VLTI unit, now installed at the 8.2-m VLT KUEYEN telescope. Adaptive Optics (AO) systems work by means of a computer-controlled deformable mirror (DM) that counteracts the image distortion induced by atmospheric turbulence. It is based on real-time optical corrections computed from image data obtained by a "wavefront sensor" (a special camera) at very high speed, many hundreds of times each second. The ESO Multi Application Curvature Adaptive Optics (MACAO) system uses a 60-element bimorph deformable mirror (DM) and a 60-element curvature wavefront sensor, with a "heartbeat" of 350 Hz (times per second). With this high spatial and temporal correcting power, MACAO is able to nearly restore the theoretically possible ("diffraction-limited") image quality of an 8.2-m VLT Unit Telescope in the near-infrared region of the spectrum, at a wavelength of about 2 µm. The resulting image resolution (sharpness) of the order of 60 milli-arcsec is an improvement by more than a factor of 10 as compared to standard seeing-limited observations. Without the benefit of the AO technique, such image sharpness could only be obtained if the telescope were placed above the Earth's atmosphere. The technical development of MACAO-VLTI in its present form was begun in 1999 and with project reviews at 6 months' intervals, the project quickly reached cruising speed. The effective design is the result of a very fruitful collaboration between the AO department at ESO and European industry which contributed with the diligent fabrication of numerous high-tech components, including the bimorph DM with 60 actuators, a fast-reaction tip-tilt mount and many others. The assembly, tests and performance-tuning of this complex real-time system was assumed by ESO-Garching staff. Installation at Paranal The first crates of the 60+ cubic-meter shipment with MACAO components arrived at the Paranal Observatory on March 12, 2003. Shortly thereafter, ESO engineers and technicians began the painstaking assembly of this complex instrument, below the VLT 8.2-m KUEYEN telescope (formerly UT2). They followed a carefully planned scheme, involving installation of the electronics, water cooling systems, mechanical and optical components. At the end, they performed the demanding optical alignment, delivering a fully assembled instrument one week before the planned first test observations. This extra week provided a very welcome and useful opportunity to perform a multitude of tests and calibrations in preparation of the actual observations. AO to the service of Interferometry The VLT Interferometer (VLTI) combines starlight captured by two or more 8.2- VLT Unit Telescopes (later also from four moveable1.8-m Auxiliary Telescopes) and allows to vastly increase the image resolution. The light beams from the telescopes are brought together "in phase" (coherently). Starting out at the primary mirrors, they undergo numerous reflections along their different paths over total distances of several hundred meters before they reach the interferometric Laboratory where they are combined to within a fraction of a wavelength, i.e., within nanometers! The gain by the interferometric technique is enormous - combining the light beams from two telescopes separated by 100 metres allows observation of details which could otherwise only be resolved by a single telescope with a diameter of 100 metres. Sophisticated data reduction is necessary to interpret interferometric measurements and to deduce important physical parameters of the observed objects like the diameters of stars, etc., cf. ESO PR 22/02 . The VLTI measures the degree of coherence of the combined beams as expressed by the contrast of the observed interferometric fringe pattern. The higher the degree of coherence between the individual beams, the stronger is the measured signal. By removing wavefront aberrations introduced by atmospheric turbulence, the MACAO-VLTI systems enormously increase the efficiency of combining the individual telescope beams. In the interferometric measurement process, the starlight must be injected into optical fibers which are extremely small in order to accomplish their function; only 6 µm (0.006 mm) in diameter. Without the "refocussing" action of MACAO, only a tiny fraction of the starlight captured by the telescopes can be injected into the fibers and the VLTI would not be working at the peak of efficiency for which it has been designed. MACAO-VLTI will now allow a gain of a factor 100 in the injected light flux - this will be tested in detail when two VLT Unit Telescopes, both equipped with MACAO-VLTI's, work together. However, the very good performance actually achieved with the first system makes the engineers very confident that a gain of this order will indeed be reached. This ultimate test will be performed as soon as the second MACAO-VLTI system has been installed later this year. MACAO-VLTI First Light After one month of installation work and following tests by means of an artificial light source installed in the Nasmyth focus of KUEYEN, MACAO-VLTI had "First Light" on April 18 when it received "real" light from several astronomical obejcts. During the preceding performance tests to measure the image improvement (sharpness, light energy concentration) in near-infrared spectral bands at 1.2, 1.6 and 2.2 µm, MACAO-VLTI was checked by means of a custom-made Infrared Test Camera developed for this purpose by ESO. This intermediate test was required to ensure the proper functioning of MACAO before it is used to feed a corrected beam of light into the VLTI. After only a few nights of testing and optimizing of the various functions and operational parameters, MACAO-VLTI was ready to be used for astronomical observations. The images below were taken under average seeing conditions and illustrate the improvement of the image quality when using MACAO-VLTI . MACAO-VLTI - First Images Here are some of the first images obtained with the test camera at the first MACAO-VLTI system, now installed at the 8.2-m VLT KUEYEN telescope. ESO PR Photo 12b/03 ESO PR Photo 12b/03 [Preview - JPEG: 400 x 468 pix - 25k [Normal - JPEG: 800 x 938 pix - 291k] ESO PR Photo 12c/03 ESO PR Photo 12c/03 [Preview - JPEG: 400 x 469 pix - 14k [Normal - JPEG: 800 x 938 pix - 135k] Captions : PR Photos 12b-c/03 show the first image, obtained by the first MACAO-VLTI system at the 8.2-m VLT KUEYEN telescope in the infrared K-band (wavelength 2.2 µm). It displays images of the star HIC 59206 (visual magnitude 10) obtained before (left; Photo 12b/03 ) and after (right; Photo 12c/03 ) the adaptive optics system was switched on. The binary is separated by 0.120 arcsec and the image was taken under medium seeing conditions (0.75 arcsec) seeing. The dramatic improvement in image quality is obvious. ESO PR Photo 12d/03 ESO PR Photo 12d/03 [Preview - JPEG: 400 x 427 pix - 18k [Normal - JPEG: 800 x 854 pix - 205k] ESO PR Photo 12e/03 ESO PR Photo 12e/03 [Preview - JPEG: 483 x 400 pix - 17k [Normal - JPEG: 966 x 800 pix - 169k] Captions : PR Photo 12d/03 shows one of the best images obtained with MACAO-VLTI (logarithmic intensity scale). The seeing was 0.8 arcsec at the time of the observations and three diffraction rings can clearly be seen around the star HIC 69495 of visual magnitude 9.9. This pattern is only well visible when the image resolution is very close to the theoretical limit. The exposure of the point-like source lasted 100 seconds through a narrow K-band filter. It has a Strehl ratio (a measure of light concentration) of about 55% and a Full-Width- Half-Maximum (FWHM) of 0.060 arcsec. The 3-D plot ( PRPhoto 12e/03 ) demonstrates the tremendous gain in peak intensity of the AO image (right) in peak intensity as compared to "open-loop" image (the "noise" to the left) obtained without the benefit of AO. ESO PR Photo 12f/03 ESO PR Photo 12f/03 [Preview - JPEG: 494 x 400 pix - 20k [Normal - JPEG: 988 x 800 pix - 204k] Caption : PR Photo 12f/03 demonstrates the correction performance of MACAO-VLTI when using a faint guide star. The observed star ( HIC 74324 (stellar spectral type G0 and visual magnitude 9.4) was artificially dimmed by a neutral optical filter to visual magnitude 16.5. The observation was carried out in 0.55 arcsec seeing and with a rather short atmospheric correlation time of 3 milliseconds at visible wavelengths. The Strehl ratio in the 25-second K-band exposure is about 10% and the FWHM is 0.14 arcseconds. The uncorrected image is shown to the left for comparison. The improvement is again impressive, even for a star as faint as this, indicating that guide stars of this magnitude are feasible during future observations. ESO PR Photo 12g/03 ESO PR Photo 12g/03 [Preview - JPEG: 528 x 400 pix - 48k [Normal - JPEG: 1055 x 800 pix - 542k] Captions : PR Photo 12g/03 shows some of the MACAO-VLTI commissioning team members in the VLT Control Room at the moment of "First Light" during the night between April 18-19, 2003. Sitting: Markus Kasper, Enrico Fedrigo - Standing: Robin Arsenault, Sebastien Tordo, Christophe Dupuy, Toomas Erm, Jason Spyromilio, Rob Donaldson (all from ESO). PR Photos 12b-c/03 show the first image in the infrared K-band (wavelength 2.2 µm) of a star (visual magnitude 10) obtained without and with image corrections by means of adaptive optics. PR Photo 12d/03 displays one of the best images obtained with MACAO-VLTI during the early tests. It shows a Strehl ratio (measure of light concentration) that fulfills the specifications according to which MACAO-VLTI was built. This enormous improvement when using AO techniques is clearly demonstrated in PR Photo 12e/03 , with the uncorrected image profile (left) hardly visible when compared to the corrected profile (right). PR Photo 11f/03 demonstrates the correction capabilities of MACAO-VLTI when using a faint guide star. Tests using different spectral types showed that the limiting visual magnitude varies between 16 for early-type B-stars and about 18 for late-type M-stars. Astronomical Objects seen at the Diffraction Limit The following examples of MACAO-VLTI observations of two well-known astronomical objects were obtained in order to provisionally evaluate the research opportunities now opening with MACAO-VLTI. They may well be compared with space-based images. The Galactic Center ESO PR Photo 12h/03 ESO PR Photo 12h/03 [Preview - JPEG: 693 x 400 pix - 46k [Normal - JPEG: 1386 x 800 pix - 403k] Caption : PR Photo 12h/03 shows a 90-second K-band exposure of the central 6 x 13 arcsec 2 around the Galactic Center obtained by MACAO-VLTI under average atmospheric conditions (0.8 arcsec seeing). Although the 14.6 magnitude guide star is located roughly 20 arcsec from the field center - this leading to isoplanatic degradation of image sharpness - the present image is nearly diffraction limited and has a point-source FWHM of about 0.115 arcsec. The center of our own galaxy is located in the Sagittarius constellation at a distance of approximately 30,000 light-years. PR Photo 12h/03 shows a short-exposure infrared view of this region, obtained by MACAO-VLTI during the early test phase. Recent AO observations using the NACO facility at the VLT provide compelling evidence that a supermassive black hole with 2.6 million solar masses is located at the very center, cf. ESO PR 17/02 . This result, based on astrometric observations of a star orbiting the black hole and approaching it to within a distance of only 17 light-hours, would not have been possible without images of diffraction limited resolution. Eta Carinae ESO PR Photo 12i/03 ESO PR Photo 12i/03 [Preview - JPEG: 400 x 482 pix - 25k [Normal - JPEG: 800 x 963 pix - 313k] Caption : PR Photo 12i/03 displays an infrared narrow K-band image of the massive star Eta Carinae . The image quality is difficult to estimate because the central star saturated the detector, but the clear structure of the diffraction spikes and the size of the smallest features visible in the photo indicate a near-diffraction limited performance. The field measures about 6.5 x 6.5 arcsec 2. Eta Carinae is one of the heaviest stars known, with a mass that probably exceeds 100 solar masses. It is about 4 million times brighter than the Sun, making it one of the most luminous stars known. Such a massive star has a comparatively short lifetime of about 1 million years only and - measured in the cosmic timescale- Eta Carinae must have formed quite recently. This star is highly unstable and prone to violent outbursts. They are caused by the very high radiation pressure at the star's upper layers, which blows significant portions of the matter at the "surface" into space during violent eruptions that may last several years. The last of these outbursts occurred between 1835 and 1855 and peaked in 1843. Despite its comparaticely large distance - some 7,500 to 10,000 light-years - Eta Carinae briefly became the second brightest star in the sky at that time (with an apparent magnitude -1), only surpassed by Sirius. Frosty Leo ESO PR Photo 12j/03 ESO PR Photo 12j/03 [Preview - JPEG: 411 x 400 pix - 22k [Normal - JPEG: 821 x 800 pix - 344k] Caption : PR Photo 12j/03 shows a 5 x 5 arcsec 2 K-band image of the peculiar star known as "Frosty Leo" obtained in 0.7 arcsec seeing. Although the object is comparatively bright (visual magnitude 11), it is a difficult AO target because of its extension of about 3 arcsec at visible wavelengths. The corrected image quality is about FWHM 0.1 arcsec. Frosty Leo is a magnitude 11 (post-AGB) star surrounded by an envelope of gas, dust, and large amounts of ice (hence the name). The associated nebula is of "butterfly" shape (bipolar morphology) and it is one of the best known examples of the brief transitional phase between two late evolutionary stages, asymptotic giant branch (AGB) and the subsequent planetary nebulae (PNe). For a three-solar-mass object like this one, this phase is believed to last only a few thousand years, the wink of an eye in the life of the star. Hence, objects like this one are very rare and Frosty Leo is one of the nearest and brightest among them.

A Galaxy for Science and Research

NASA Astrophysics Data System (ADS)

2007-11-01

During his visit to ESO's Very Large Telescope at Paranal, the European Commissioner for Science and Research, Janez Potočnik, participated in an observing sequence and took images of a beautiful spiral galaxy. ESO PR Photo 43/07 ESO PR Photo 49/07 Twisted Spiral Galaxy NGC 134 The visit took place on 27 October and the Commissioner observed with one of the FORS instruments on Antu, the first 8.2-m Unit Telescope of the VLT. "Two hours bus ride from the nearest town, Antofagasta, in the middle of nowhere and at 2 600 m altitude, rises a state of the art astronomical observatory at which scientists from across Europe venture to exploit some of the most advanced technologies and sophisticated techniques available within astronomy. One of the facilities is the VLT, the Very Large Telescope, with which, together with the other telescopes, scientists can study objects at the far edge of the Universe," wrote Potočnik on his blog. Known until now as a simple number in a catalogue, NGC 134, the 'Island in the Universe' that was observed by the Commissioner is replete with remarkable attributes, and the VLT has clapped its eyes on them. Just like our own Galaxy, NGC 134 is a barred spiral with its spiral arms loosely wrapped around a bright, bar-shaped central region. One feature that stands out is its warped disc. While a galaxy's disc is often pictured as a flat structure of gas and stars surrounding the galaxy's centre, a warped disc is a structure that, when viewed sideways, resembles a bent record album left out too long in the burning Sun. Warps are actually not atypical. More than half of the spiral galaxies do show warps one way or another, and our own Milky Way also has a small warp. Many theories exist to explain warps. One possibility is that warps are the aftermath of interactions or collisions between galaxies. These can also produce tails of material being pulled out from the galaxy. The VLT image reveals that NGC 134 also appears to have a tail of gas stripped from the top edge of the disc. So did NGC 134 have a striking encounter with another galaxy in the past? Or is some other galaxy out there exerting a gravitational pull on it? This is a riddle astronomers need to solve. The superb VLT image also shows that the galaxy has its fair share of ionised hydrogen regions (HII regions) lounging along its spiral arms. Seen in the image as red features, these are glowing clouds of hot gas in which stars are forming. The galaxy also shows prominent dark lanes of dust across the disc, obscuring part of the galaxy's starlight. Studying galaxies like NGC 134 is an excellent way to learn more about our own Galaxy. NGC 134 was discovered by Sir John Herschel at the Cape of Good Hope and is located in the Sculptor southern constellation. The galaxy is located about 60 million light-years away - when the light that was captured by the VLT originally left the galaxy, a dramatic episode of mass extinction had led to the disappearance of dinosaurs on Earth, paving the way for the appearance of mammals and later specifically of humans, who have built unique high-tech installations in the Atacama desert to satisfy their curiosity about the workings of the Universe. Still, NGC 134 is not very far away, by cosmological standards. It is the dominant member of a small group of galaxies that belongs to the Virgo or Local Supercluster and is one of the 200 brightest galaxies in our skies.

ESO Successfully Tests Automation of Telescope Operations

NASA Astrophysics Data System (ADS)

1997-02-01

This week astronomers at the European Southern Observatory have tested a novel approach of doing astronomy from the ground. Inaugurating a new era, the ESO 3.5-metre New Technology Telescope (NTT) at La Silla successfully performed a series of observations under automatic control by advanced computer software developed by the ESO Data Management Division (DMD) for use with the ESO Very Large Telescope (VLT). This move has been made necessary by technological improvements in telescopes and the increasing competition among scientists for these valuable resources. Caption to ESO PR Photo 05/97 [JPG, 184k] This Press Release is accompanied by ESO Press Photo 05/97 of the NTT. New telescopes produce more data Over the past few years, astronomical telescopes and the amount of data they produce have grown rapidly in size. With the advent of increasingly efficient, large digital cameras, the new telescopes with mirrors as large as 8 to 10 metres in diameter will deliver Gigabytes of valuable information each night. There is little doubt that scientific breakthroughs will be made with these telescopes and it should be no surprise that there is fierce competition for precious observing nights among the international astronomical community. Automated observations In order to make sure that the available observing time at the VLT will be used in the best and most efficient way, ESO has been developing advanced computer systems which will automatically schedule observations according to the scientific priorities of astronomers and the prevailing conditions of weather and equipment at the observatory. Once the astronomical data is gathered it is processed automatically at the telescope to provide the astronomer with immediately useful astronomical images and other pertinent information. No longer will the astronomer be required to spend weeks processing data into a form where results can be extracted. The continuous flow of astronomical data made possible with this system is referred to as the VLT Data Flow System , now being perfected by the ESO Data Management Division for use on ESO's Very Large Telescope project. First tests at the NTT On February 5, a team of software engineers and astronomers from ESO used a first version of the new VLT Data Flow System to perform observations on ESO's New Technology Telescope (NTT) at the La Silla Observatory in Chile. A computer file containing a complete description of an observation (for instance, object position in the sky, filtres and exposure time, and other relevant information) prepared in advance by an astronomer was transferred via the satellite link from the ESO Headquarters in Germany to the NTT computers at La Silla and executed on the control system of the telescope. The telescope then moved to the correct position in the sky, the camera was activated and a few minutes later, a processed image a distant galaxy appeared on the screen in front of the observers. The image was saved in an automatic archive system that writes the astronomical data on CD-ROM. The entire process took place automatically and demonstrated that this system is capable of taking high quality data from the sky at the best possible time and delivering the results to the astronomer, efficiently and in the most convenient form. Further developments This is the first time that a ground-based telescope has been operated under the new system. This successful initial test bodes well for the start-up of the VLT. During 1997, ESO will further develop the data flow system in preparation for the beginning of commissioning of the first VLT 8.2-metre unit, less then 12 months from now. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

ESO PR Highlights in 2004

NASA Astrophysics Data System (ADS)

2005-01-01

Last year proved again a wonderful one for astronomy in general and for ESO in particular. Certainly the most important astronomical event for a large public was the unique Transit of Venus : on June 8, 2004, Venus - the Earth's sister planet - passed in front of the Sun. This rare event - the last one occurred in 1882 - attracted the attention of millions of people all over the world. ESO in cooperation with several other institutes and with support from the European Commission organised through the whole year the Venus Transit 2004 (VT-2004) public education programme that successfully exposed the broad public to a number of fundamental issues at the crucial interface between society and basic science. The web site experienced a record 55 million webhits during a period of 8 hours around the transit. The programme also re-enacted the historical determination of the distance to the Sun (the "Astronomical Unit") by collecting 4550 timings of the four contacts made by more than 1500 participating group of observers and combining them in a calculation of the AU. This resulted in an astonishing accurate value of the Astronomical Unit. More details are available at the VT-2004 website, whose wealth of information will certainly make it a useful tool until the next transit in 2012! For ESO also, 2004 proved a very special year. Finland officially joined as eleventh member state and in December, the Chilean President, Ricardo Lagos, visited the Paranal Observatory. Last year was also the Fifth anniversary of the Very Large Telescope, ESO's flagship facility, as on April 1, 1999 the first 8.2-m VLT Unit Telescope, Antu (UT1), was "handed over" to the astronomers. On this occasion, ESO released several products, including a selection of the best astronomical images taken with the VLT, the VLT Top 20. But there is no doubt that the numerous high quality images published last year are all contenders to top the charts of best astronomical pictures. The year 2004 also saw many new interesting scientific results on the basis of data from ESO telescopes, including several results from the unmatched interferometer mode of the VLT, the VLTI, some of which were highlighted in ESO Press Releases. Certainly worth noting is the possible first ever bona-fide image of an exoplanet and the discovery of the lightest known exoplanet . At the beginning of the year, Paranal welcomed the first Auxiliary Telescope, while on the instrument side as well, 2004 was a good year: we saw the arrival of SINFONI on the VLT, of AMBER on the VLTI, and the installation at the NACO Adaptive Optics instrument of the " Simultaneous Differential Imager (SDI)" to detect exoplanets. And the first prototype of the Astrophysical Virtual Observatory was able to provide unprecedented results on the existence of Type-2 quasars by discovering an entire population of obscured, powerful supermassive black holes. Many of these developments are described in ESO's Press Releases, most with Press Photos, cf. the 2004 PR Index. Some of last year's ESO PR highlights may be accessed directly via the clickable image above.

Very Massive Stars and the upper end of the IMF

NASA Astrophysics Data System (ADS)

Crowther, P.

2013-06-01

I discuss theoretical and observational evidence regarding the existence of Very Massive Stars (VMS) with initial masses significantly in excess of 100~Mo. Theoretical evidence includes consideration of the (classical) Eddington limit, while observational evidence involves efforts to interpret photometric and spectroscopic observations of the brightest stars in young, high mass clusters (R136a, Arches, NGC 3603), including new VLT/SINFONI and HST/STIS spectroscopy plus consideration of multiplicity (binaries and higher order systems).

New Insights on 216 Kleopatra Based on Images Collected with the SPHERE Extreme AO System

NASA Astrophysics Data System (ADS)

Marchis, F.; Vernazza, P.; Hanus, J.; Marsset, M.; Yang, B.; Carry, B.; Santana-Ros, T.; Birlan, M.

2017-12-01

ESO allocated to our Large Asteroid Survey with SPHERE (LASS) program 152 hours of observations over four semesters (PI: Pierre Vernazza, run ID: 199.C-0074) to carry out disk-resolved images of 38 large (D≥100 km) main-belt asteroids (sampling the four main compositional classes) at high angular- resolution with VLT/SPHERE throughout their rotation in order to derive their 3-D shape, the size distribution of the largest craters, and their density. Here we focus on the analysis of SPHERE data taken in July 2017 of the triple asteroid (216) Kleopatra. Two tiny moons (3 & 5 km diameter) were discovered in September 2008 around the large (equivalent radius 67.5±2.9 km) M-type asteroid orbiting very close to the irregularly shaped primary at 300 and 700 km respectively (Descamps et al. 2010). With these additional data, our goals are i) to refine the average density of this interesting M-type asteroid ii) estimate its interior structure by detecting precession effects between the satellites iii) detect the presence of an additional moon which was suspected in W.M. Keck AO observation taken back in 2008. We will present this new data set, their analysis and new conclusion on the origins and formation of this asteroid.

Psychological Vulnerability and Problem Gambling: The Mediational Role of Cognitive Distortions.

PubMed

Lévesque, David; Sévigny, Serge; Giroux, Isabelle; Jacques, Christian

2018-01-03

Despite numerous studies demonstrating the influence of cognitive distortions on gambling problem severity, empirical data regarding the role of psychological vulnerability on the latter is limited. Hence, this study assesses the mediating effect of cognitive distortions between psychological vulnerability (personality and mood), and gambling problem severity. It also verifies whether the relationships between these variables differs according to the preferred gambling activity. The sample is composed of 272 male gamblers [191 poker players; 81 video lottery terminal (VLT) players] aged between 18 and 82 years (M = 35.2). Bootstrap analysis results revealed that cognitive distortions mediate the effect of narcissism on gambling problem severity for both groups. The level of depression for VLT players significantly predicted gambling problem severity, both directly and indirectly via the mediating effect of cognitive distortions. Mediation analyses also indicated that narcissism had an indirect impact on problem gambling through cognitive distortions for both groups. These findings suggest that certain vulnerabilities related to personality and mood may influence cognitive distortion intensity and gambling problem severity. In addition, psychological vulnerabilities could differ based on preferred gambling activity. These results may be useful for prevention policies, identifying high risk gamblers and planning psychological interventions.

Status and new operation modes of the versatile VLT/NaCo

NASA Astrophysics Data System (ADS)

Girard, Julien H. V.; Kasper, Markus; Quanz, Sascha P.; Kenworthy, Matthew A.; Rengaswamy, Sridharan; Schödel, Rainer; Gallenne, Alexandre; Gillessen, Stefan; Huerta, Nicolas; Kervella, Pierre; Kornweibel, Nick; Lenzen, Rainer; Mérand, Antoine; Montagnier, Guillaume; O'Neal, Jared; Zins, Gérard

2010-07-01

This paper aims at giving an update on the most versatile Adaptive Optics fed instrument to date, the well known and successful NACO*. Although NACO is only scheduled for about two more years† at the Very Large Telescope (VLT), it keeps on evolving with additional operation modes bringing original astronomical results. The high contrast imaging community uses it creatively as a test-bench for SPHERE‡ and other second generation planet imagers. A new visible wavefront sensor (WFS) optimized for Laser Guide Star (LGS) operations has been installed and tested, the cube mode is more and more required for frame selection on bright sources, a seeing enhancer mode (no tip/tilt correction) is now offered to provide full sky coverage and welcome all kind of extragalactic applications, etc. The Instrument Operations Team (IOT) and Paranal engineers are currently working hard at maintaining the instrument overall performances but also at improving them and offering new capabilities, providing the community with a well tuned and original instrument for the remaining time it is being used. The present contribution delivers a non-exhaustive overview of the new modes and experiments that have been carried out in the past months.

Velocity-resolved [Ne III] from X-ray irradiated Sz 102 microjets

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Chun-Fan; Shang, Hsien; Walter, Frederick M.

2014-05-10

Neon emission lines are good indicators of high-excitation regions close to a young stellar system because of their high ionization potentials and large critical densities. We have discovered [Ne III] λ3869 emission from the microjets of Sz 102, a low-mass young star in Lupus III. Spectroastrometric analyses of two-dimensional [Ne III] spectra obtained from archival high-dispersion (R ≈ 33, 000) Very Large Telescope/UVES data suggest that the emission consists of two velocity components spatially separated by ∼0.''3, or a projected distance of ∼60 AU. The stronger redshifted component is centered at ∼ + 21 km s{sup –1} with a linemore » width of ∼140 km s{sup –1}, and the weaker blueshifted component at ∼ – 90 km s{sup –1} with a line width of ∼190 km s{sup –1}. The two components trace velocity centroids of the known microjets and show large line widths that extend across the systemic velocity, suggesting their potential origins in wide-angle winds that may eventually collimate into jets. Optical line ratios indicate that the microjets are hot (T ≲ 1.6 × 10{sup 4} K) and ionized (n{sub e} ≳ 5.7 × 10{sup 4} cm{sup –3}). The blueshifted component has ∼13% higher temperature and ∼46% higher electron density than the redshifted counterpart, forming a system of an asymmetric pair of jets. The detection of the [Ne III] λ3869 line with the distinct velocity profile suggests that the emission originates in flows that may have been strongly ionized by deeply embedded hard X-ray sources, most likely generated by magnetic processes. The discovery of [Ne III] λ3869 emission along with other optical forbidden lines from Sz 102 supports the picture of wide-angle winds surrounding magnetic loops in the close vicinity of the young star. Future high-sensitivity X-ray imaging and high angular-resolution optical spectroscopy may help confirm the picture proposed.« less

Acne at The Bottom Of The Main Sequence

NASA Astrophysics Data System (ADS)

Barnes, John; Haswell, C.; Jenkins, J.; Jeffers, S.; Jones, H. R. A.; Lohr, M.; Pavlenko, Y.

2016-08-01

Starspots are an important manifestation of stellar activity and yet their distribution patterns on the lowest mass stars is not well known. Time series spectra of fully convective M dwarfs taken in the red-optical with UVES reveal numerous line profile distortions which are interpreted as starspots. We derive Doppler images for four M4.5V - M9V stars and find that contrast ratios corresponding to photosphere-spot temperature differences of only 200-300 K are sufficient to model the timeseries spectra. Although more starspot structure is found at high latitudes, spots are reconstructed at a range of phases and latitudes with mean spot filling factors of only a few per cent. The occurrence of low-contrast spots at predominantly high latitudes is in general likely to be responsible for the low amplitude photometric variability seen in late-M dwarfs. The recovered starspot patterns are used to assess their effect on precision radial velocity surveys aimed at detecting planets around this population of stars.

Development of predictive models for total phenolics and free p-coumaric acid contents in barley grain by near-infrared spectroscopy.

PubMed

Han, Zhigang; Cai, Shengguan; Zhang, Xuelei; Qian, Qiufeng; Huang, Yuqing; Dai, Fei; Zhang, Guoping

2017-07-15

Barley grains are rich in phenolic compounds, which are associated with reduced risk of chronic diseases. Development of barley cultivars with high phenolic acid content has become one of the main objectives in breeding programs. A rapid and accurate method for measuring phenolic compounds would be helpful for crop breeding. We developed predictive models for both total phenolics (TPC) and p-coumaric acid (PA), based on near-infrared spectroscopy (NIRS) analysis. Regressions of partial least squares (PLS) and least squares support vector machine (LS-SVM) were compared for improving the models, and Monte Carlo-Uninformative Variable Elimination (MC-UVE) was applied to select informative wavelengths. The optimal calibration models generated high coefficients of correlation (r pre ) and ratio performance deviation (RPD) for TPC and PA. These results indicated the models are suitable for rapid determination of phenolic compounds in barley grains. Copyright © 2017 Elsevier Ltd. All rights reserved.

An abundance analysis from the STIS-HST UV spectrum of the non-magnetic Bp star HR 6000

NASA Astrophysics Data System (ADS)

Castelli, F.; Cowley, C. R.; Ayres, T. R.; Catanzaro, G.; Leone, F.

2017-05-01

Context. The sharp-line spectrum of the non-magnetic, main-sequence Bp star HR 6000 has peculiarities that distinguish it from those of the HgMn stars with which it is sometimes associated. The position of the star close to the center of the Lupus 3 molecular cloud, whose estimated age is on the order of 9.1 ± 2.1 Myr, has lead to the hypothesis that the anomalous peculiarities of HR 6000 can be explained by the young age of the star. Aims: Observational material from the Hubble Space Telescope (HST) provides the opportunity to extend the abundance analysis previously performed for the optical region and clarify the properties of this remarkable peculiar star. Our aim was to obtain the atmospheric abundances for all the elements observed in a broad region from 1250 to 10 000 Å. Methods: An LTE synthetic spectrum was compared with a high-resolution spectrum observed with the Space Telescope Imaging Spectrograph (STIS) equipment in the 1250-3040 Å interval. Abundances were changed until the synthetic spectrum fit the observed spectrum. The assumed model is an LTE, plane-parallel, line-blanketed ATLAS12 model already used for the abundance analysis of a high-resolution optical spectrum observed at ESO with the Ultraviolet and Visual Echelle Spectrograph (UVES). The stellar parameters are Teff = 13450 K, log g = 4.3, and zero microturbulent velocity. Results: Abundances for 28 elements and 7 upper limits were derived from the ultraviolet spectrum. Adding results from previous work, we have now quantitative results for 37 elements, some of which show striking contrasts with those of a broad sample of HgMn stars. The analysis has pointed out numerous abundance anomalies, such as ionization anomalies and line-to-line variation in the derived abundances, in particular for silicon. The inferred discrepancies could be explained by non-LTE effects and with the occurrence of diffusion and vertical abundance stratification. In the framework of the last hypothesis, we obtained, by means of trial and error, empirical step functions of abundance versus optical depth log (τ5000) for carbon, nitrogen, silicon, manganese, and gold, while we failed to find such a function for phosphorous. The poor results for carbon, and mostly for phosphorus, suggest the possible importance in this star of NLTE effects to be investigated in future works.

Characterization of members to stellar kinematic groups using chemical tagging

NASA Astrophysics Data System (ADS)

Tabernero, H. M.

2014-10-01

In this thesis we have characterized more than one thousand late-type stars. For this characterization we have been making use of high resolution spectroscopy (R > 40,000) taken in different spectrographs, HERMES at the Mercator telescope in La Palma, FOCES in the 2.2m telescope at Calar Alto, the Coudé-Echelle spectrograph at 2 m-the Alfred- Jensch-Teleskop in Tautenburg, and UVES at the Very Large Telescope in La Silla. Stellar spectroscopy, in particular at high-resolution, is a modern tool that allows us to extract a lot of information of a given star. In particular, we have obtained their atmospheric parameters, namely: effective temperature (Teff), surface gravity (log g), microturbulent velocity (ξ), and iron abundance ([Fe/H], used as a metallicity proxy). An automatic code (StePar) has been developed. This code allows to derive stellar atmospheric parameters (Teff , log g, ξ, and [Fe/H]) only in a few minutes. Also, with these parameters at hand we have derived chemical abundances for 20 different chemical elements: Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ba, Ce, and Nd, which offer many or at least some isolated transitions in the wavelength range of the spectra taken with these spectrographs. This work comprises two publications in Astronomy & Astrophysics. The first one is about chemical tagging applied to the Hyades SC (see Chapter 2 or Tabernero et al. 2012). The second paper is a in-depth study of the chemical composition of candidate members to the Ursa Major MG (see Chapter 3 or Tabernero et al. 2015). Additionally there is another chapter that comprises the analysis of Galactic stars within the GAIA ESO Survey stars (GES, Gilmore et al. 2012; Randich & Gilmore 2013) whose data have contributed to the publication of some release (Lanzafame et al. 2014; Smiljanic et al. 2014) and science papers (Jofre et al. 2014; Sousa et al. 2014; Spina et al. 2014a,b) that made use the survey results. The two papers included in this thesis deal with the characterization of late-type stars (F, G, and K spectral types). In particular, this thesis is based on the determination of stellar atmospheric parameters and element abundances.

"First Light" for the VLT Interferometer

NASA Astrophysics Data System (ADS)

2001-03-01

Excellent Fringes From Bright Stars Prove VLTI Concept Summary Following the "First Light" for the fourth of the 8.2-m telescopes of the VLT Observatory on Paranal in September 2000, ESO scientists and engineers have just successfully accomplished the next major step of this large project. On March 17, 2001, "First Fringes" were obtained with the VLT Interferometer (VLTI) - this important event corresponds to the "First Light" for an astronomical telescope. At the VLTI, it occurred when the infrared light from the bright star Sirius was captured by two small telescopes and the two beams were successfully combined in the subterranean Interferometric Laboratory to form the typical pattern of dark and bright lines known as " interferometric fringes ". This proves the success of the robust VLTI concept, in particular of the "Delay Line". On the next night, the VLTI was used to perform a scientific measurement of the angular diameter of another comparatively bright star, Alpha Hydrae ( Alphard ); it was found to be 0.00929±0.00017 arcsec . This corresponds to the angular distance between the two headlights of a car as seen from a distance of approx. 35,000 kilometres. The excellent result was obtained during a series of observations, each lasting 2 minutes, and fully confirming the impressive predicted abilities of the VLTI . This first observation with the VLTI is a monumental technological achievement, especially in terms of accuracy and stability . It crucially depends on the proper combination and functioning of a large number of individual opto-mechnical and electronic elements. This includes the test telescopes that capture the starlight, continuous and extremely precise adjustment of the various mirrors that deflect the light beams as well as the automatic positioning and motion of the Delay Line carriages and, not least, the optimal tuning of the VLT INterferometer Commissionning Instrument (VINCI). These initial observations prove the overall concept for the VLTI . It was first envisaged in the early 1980's and has been continuously updated, as new technologies and materials became available during the intervening period. The present series of functional tests will go on for some time and involve many different configurations of the small telescopes and the instrument. It is then expected that the first combination of light beams from two of the VLT 8.2-m telescopes will take place in late 2001 . According to current plans, regular science observations will start from 2002, when the European and international astronomical community will have access to the full interferometric facility and the specially developed VLTI instrumentation now under construction. A wide range of scientific investigations will then become possible, from the search for planets around nearby stars, to the study of energetic processes at the cores of distant galaxies. With its superior angular resolution (image sharpness), the VLT is now beginning to open a new era in observational optical and infrared astronomy. The ambition of ESO is to make this type of observations available to all astronomers, not just the interferometry specialists. Video Clip 03/01 : Various video scenes related to the VLTI and the "First Fringes". PR Photo 10a/01 : "First Fringes" from the VLTI on the computer screen. PR Photo 10b/01 : Celebrating the VLTI "First Fringes" . PR Photo 10c/01 : Overview of the VLT Interferometer . PR Photo 10d/01 : Interferometric observations: Fringes from two stars of different angular size . PR Photo 10e/01 : Interferometric observations: Change of fringes with increasing baseline . PR Photo 10f/01 : Aerial view of the installations for the VLTI on the Paranal platform. PR Photo 10g/01 : Stations for the VLTI Auxiliary Telescopes. PR Photo 10h/01 : A test siderostat in place for observations. PR Photo 10i/01 : A test siderostat ( close-up ). PR Photo 10j/01 : One of the Delay Line carriages in the Interferometric Tunnel. PR Photo 10k/01 : The VINCI instrument in the Interferometric Laboratory. PR Photo 10l/01 : The VLTI Control Room . "First Fringes at the VLTI": A great moment! First light of the VLT Interferometer - PR Video Clip 03/01 [MPEG - x.xMb] ESO PR Video Clip 03/01 "First Light of the VLT Interferometer" (March 2001) (5025 frames/3:21x min) [MPEG Video+Audio; 144x112 pix; 6.9Mb] [MPEG Video+Audio; 320x240 pix; 13.7Mb] [RealMedia; streaming; 34kps] [RealMedia; streaming; 200kps] ESO Video Clip 03/01 provides a quick overview of the various elements of the VLT Interferometer and the important achievement of "First Fringes". The sequence is: General view of the Paranal observing platform. The "stations" for the VLTI Auxiliary Telescopes. Statement by the Manager of the VLT project, Massimo Tarenghi . One of the VLTI test telescopes ("siderostats") is being readied for observations. The Delay Line carriages in the Interferometric Tunnel move. The VINCI instrument in the Interferometric Laboratory is adjusted. Platform at sunset, before the observations. Astronomers and engineers prepare for the first observations in the VLTI Control Room in the Interferometric Building. "Interferometric Fringes" on the computer screen. Concluding statements by Andreas Glindemann , VLTI Project Leader, and Massimo Tarenghi . Distant view of the installations at Paranal at sunset (on March 1, 2001). The moment of "First Fringes" at the VLTI occurred in the evening of March 17, 2001 . The bright star Sirius was observed with two small telescopes ("siderostats"), specially constructed for this purpose during the early VLTI test phases. ESO PR Video Clip 03/01 includes related scenes and is based on a more comprehensive documentation, now available as ESO Video News Reel No. 12. The star was tracked by the two telescopes and the light beams were guided via the Delay Lines in the Interferometric Tunnel to the VINCI instrument [1] at the Interferometric Laboratory. The path lengths were continuously adjusted and it was possible to keep them stable to within 1 wavelength (2.2 µm, or 0.0022 mm) over a period of at least 2 min. Next night, several other stars were observed, enabling the ESO astronomers and engineers in the Control Room to obtain stable fringe patterns more routinely. With the special software developed, they also obtained 'on-line' an accurate measurement of the angular diameter of a star. This means that the VLTI delivered its first valid scientific result, already during this first test . First observation with the VLTI ESO PR Photo 10a/01 ESO PR Photo 10a/01 [Preview - JPEG: 400 x 315 pix - 96k] [Normal - JPEG: 800 x 630 pix - 256k] [Hi-Res - JPEG: 3000 x 2400 pix - 1.7k] ESO PR Photo 10b/01 ESO PR Photo 10b/01 [Preview - JPEG: 400 x 218 pix - 80k] [Normal - JPEG: 800 x 436 pix - 204k] Caption : PR Photo 10a/01 The "first fringes" obtained with the VLTI, as seen on the computer screen during the observation (upper right window). The fringe pattern arises when the light beams from two small telescopes are brought together in the VINCI instrument. The pattern itself contains information about the angular extension of the observed object, here the bright star Sirius . More details about the interpretation of this pattern is given in Appendix A. PR Photo 10b/01 : Celebrating the moment of "First Fringes" at the VLTI. At the VLTI control console (left to right): Pierre Kervella , Vincent Coudé du Foresto , Philippe Gitton , Andreas Glindemann , Massimo Tarenghi , Anders Wallander , Roberto Gilmozzi , Markus Schoeller and Bill Cotton . Bertrand Koehler was also present and took the photo. Technical information about PR Photo 10a/01 is available below. Following careful adjustment of all of the various components of the VLTI, the first attempt to perform a real observation was initiated during the night of March 16-17, 2001. "Fringes" were actually acquired during several seconds, leading to further optimization of the Delay Line optics. The next night, March 17-18, stable fringes were obtained on the bright stars Sirius and Lambda Velorum . The following night, the first scientifically valid results were obtained during a series of observations of six stars. One of these, Alpha Hydrae , was measured twice, with an interval of 15 minutes between the 2-min integrations. The measured diameters were highly consistent, with a mean of 0.00929±0.00017 arcsec. This new VLTI measurement is in full agreement with indirect (photometric) estimates of about 0.009 arcsec. The overall performance of the VLTI was excellent already in this early stage. For example, the interferometric efficiency ('contrast' on a stellar point source) was measured to be 87% and stable to within 1.3% over several days. This performance will be further improved following additional tuning. The entire operation of the VLTI was performed remotely from the Control Room, as this will also be the case in the future. Another great advantage of the VLTI concept is the possibility to analyse the data at the control console. This is one of the key features of the VLTI that contributes to make it a very user-friendly facility. Overview of the VLT Interferometer ESO PR Photo 10c/01 ESO PR Photo 10c/01 [Preview - JPEG: 400 x 410 pix - 60k] [Normal - JPEG: 800 x 820 pix - 124k] [Hi-Res - JPEG: 3000 x 3074 pix - 680k] Caption : PR Photo 10c/01 Overview of the VLT Interferometer, with the various elements indicated. In this case, the light beams from two of the 8.2-m telescopes are combined. The VINCI instrument that was used for the present test, is located at the common focus in the Interferometric Laboratory. The interferometric principle is based on the phase-stable combination of light beams from two or more telescopes at a common interferometric focus , cf. PR Photo 10c/01 . The light from a celestial object is captured simultaneously by two or more telescopes. For the first tests, two "siderostats" with 40-cm aperture are used; later on, two or more 8.2-m Unit Telescopes will be used, as well as several moving 1.8-m Auxiliary Telescopes (ATs), now under construction at the AMOS factory in Belgium. Via several mirrors and through the Delay Line, that continuously compensates for changes in the path length introduced by the Earth's rotation as well as by other effects (e.g., atmospheric turbulence), the light beams are guided towards the interferometric instrument VINCI at the common interferometric focus. It is located in the subterranean Interferometric Laboratory , at the centre of the observing platform on the top of the Paranal mountain. Photos of some of the VLTI elements are shown in Appendix B. The interferometric technique allows achieving images, as sharp as those of a telescope with a diameter equivalent to the largest distance between the telescopes in the interferometer. For the VLTI, this distance is about 200 metres, resulting in a resolution of 0.001 arcsec in the near-infrared spectral region (at 1 µm wavelength), or 0.0005 arcsec in visual light (500 nm). The latter measure corresponds to about 2 metres on the surface of the Moon. The VLTI instruments The installation and putting into operation of the VLTI at Paranal is a gradual process that will take several years. While the present "First Fringe" event is of crucial importance, the full potential of the VLTI will only be reached some years from now. This will happen with the successive installation of a number of highly specialised instruments, like the near-infrared/red VLTI focal instrument (AMBER) , the Mid-Infrared interferometric instrument for the VLTI (MIDI) and the instrument for Phase-Referenced Imaging and Microarcsecond Astrometry (PRIMA). Already next year, the three 1.8-m Auxiliary Telescopes that will be fully devoted to interferometric observations, will arrive at Paranal. Ultimately, it will be possible to combine the light beams from all the large and small telescopes. Great research promises Together, they will be able to achieve an unprecedented image sharpness (angular resolution) in the optical/infrared wavelength region, and thanks to the great light-collecting ability of the VLT Unit Telescopes, also for observations of quite faint objects. This will make it possible to carry out many different front-line scientific studies, beyond the reach of other instruments. There are many promising research fields that will profit from VLTI observations, of which the following serve as particularly interesting examples: * The structure and composition of the outer solar system, by studies of individual moons, Trans-Neptunian Objects and comets. * The direct detection and imaging of exoplanets in orbit around other stars. * The formation of star clusters and their evolution, from images and spectra of very young objects. * Direct views of the surface structures of stars other than the Sun. * Measuring accurate distances to the most prominent "stepping stones" in the extragalactic distance scale, e.g., galactic Cepheid stars, the Large Magellanic Cloud and globular clusters. * Direct investigations of the physical mechanisms responsible for stellar pulsation, mass loss and dust formation in stellar envelopes and evolution to the Planetary Nebula and White Dwarf stages. * Close-up studies of interacting binary stars to better understand their mass transfer mechanisms and evolution. * Studies of the structure of the circum-stellar environment of stellar black holes and neutron stars. * The evolution of the expanding shells of unstable stars like novae and supernovae and their interaction with the interstellar medium. * Studying the structure and evolution of stellar and galactic nuclear accretion disks and the associated features, e.g., jets and dust tori. * With images and spectra of the innermost regions of the Milky Way galaxy, to investigate the nature of the nucleus surrounding the central black hole. Clearly, there will be no lack of opportunities for trailblazing research with the VLTI. The "First Fringes" constitute a very important milestone in this direction. Appendix A: How does it work? ESO PR Photo 10d/01 ESO PR Photo 10d/01 [Preview - JPEG: 400 x 290 pix - 24k] [Normal - JPEG: 800 x 579 pix - 68k] [Hi-Res - JPEG: 3000 x 2170 pix - 412k] ESO PR Photo 10e/01 ESO PR Photo 10e/01 [Preview - JPEG: 400 x 219 pix - 32k] [Normal - JPEG: 800 x 438 pix - 64k] [Hi-Res - JPEG: 3000 x 1644 pix - 336k] Caption : PR Photo 10d/01 demonstrates in a schematic way, how the images of two stars of different angular size (left) will look like, with a single telescope (middle) and with an interferometer like the VLTI (right). Whereas there is little difference with one telescope, the fringe patterns at the interferometer are quite different. Conversely, the appearance of this pattern provides a measure of the star's angular diameter. In PR Photo 10e/01 , interferometric observations of a single star are shown, as the distance between the two telescopes is gradually increased. The observed pattern at the focal plane clearly changes, and the "fringes" disappear completely. See the text for more details. The principle behind interferometry is the "coherent optical interference" of light beams from two or more telescopes, due to the wave nature of light. The above illustrations serve to explain what the astronomers observe in the simplest case, that of a single star with a certain angular size, and how this can be translated into a measurement of this size. In PR Photo 10d/01 , the difference between two stars of different diameter is illustrated. While the image of the smaller star displays strong interference effects (i.e., a well visible fringe pattern), those of the larger star are much less prominent. The "visibility" of the fringes is therefore a direct measure of the size; the stronger they appear (the "larger the contrast"), the smaller is the star. If the distance between the two telescopes is increased when a particular star is observed ( PR Photo 10e/01 ), then the fringes become less and less prominent. At a certain distance, the fringe pattern disppears completely. This distance is directly related to the angular size of the star. Appendix B: Elements of the VLT Interferometer Contrary to other large astronomical telescopes, the VLT was designed from the beginning with the use of interferometry as a major goal . For this reason, the four 8.2-m Unit Telescopes were positioned in a quasi-trapezoidal configuration and several moving 1.8-m telescopes were included into the overall VLT concept, cf. PR Photo 10f/01 . The photos below show some of the key elements of the VLT Interferometer during the present observations. They include the siderostats , 40-cm telescopes that serve to capture the light from a comparatively bright star ( Photos 10g-i/01 ), the Delay Lines ( Photo 10j/01 ), and the VINCI instrument ( Photo 10k/01) Earlier information about the development and construction of the individual elements of the VLTI is available as ESO PR 04/98 , ESO PR 14/00 and ESO PR Photos 26a-e/00.

Chandra and the VLT Jointly Investigate the Cosmic X-Ray Background

NASA Astrophysics Data System (ADS)

2001-03-01

Summary Important scientific advances often happen when complementary investigational techniques are brought together . In the present case, X-ray and optical/infrared observations with some of the world's foremost telescopes have provided the crucial information needed to solve a 40-year old cosmological riddle. Very detailed observations of a small field in the southern sky have recently been carried out, with the space-based NASA Chandra X-Ray Observatory as well as with several ground-based ESO telescopes, including the Very Large Telescope (VLT) at the Paranal Observatory (Chile). Together, they have provided the "deepest" combined view at X-ray and visual/infrared wavelengths ever obtained into the distant Universe. The concerted observational effort has already yielded significant scientific results. This is primarily due to the possibility to 'identify' most of the X-ray emitting objects detected by the Chandra X-ray Observatory on ground-based optical/infrared images and then to determine their nature and distance by means of detailed (spectral) observations with the VLT . In particular, there is now little doubt that the so-called 'X-ray background' , a seemingly diffuse short-wave radiation first detected in 1962, in fact originates in a vast number of powerful black holes residing in active nuclei of distant galaxies . Moreover, the present investigation has permitted to identify and study in some detail a prime example of a hitherto little known type of object, a distant, so-called 'Type II Quasar' , in which the central black hole is deeply embedded in surrounding gas and dust. These achievements are just the beginning of a most fruitful collaboration between "space" and "ground". It is yet another impressive demonstration of the rapid progress of modern astrophysics, due to the recent emergence of a new generation of extremely powerful instruments. PR Photo 09a/01 : Images of a small part of the Chandra Deep Field South , obtained with ESO telescopes in three different wavebands. PR Photo 09b/01 : A VLT/FORS1 spectrum of a 'Type II Quasar' discovered during this programme. The 'Chandra Deep Field South' and the X-Ray Background ESO PR Photo 09a/01 ESO PR Photo 09a/01 [Preview - JPEG: 400 x 183 pix - 76k] [Normal - JPEG: 800 x 366 pix - 208k] [Hires - JPEG: 3000 x 1453 pix - 1.4M] Caption : PR Photo 09a/01 shows optical/infrared images in three wavebands ('Blue', 'Red', 'Infrared') from ESO telescopes of the Type II Quasar CXOCDFS J033229.9 -275106 (at the centre), one of the distant X-ray sources identified in the Chandra Deep Field South (CDFS) area during the present study. Technical information about these photos is available below. The 'Chandra Deep Field South (CDFS)' is a small sky area in the southern constellation Fornax (The Oven). It measures about 16 arcmin across, or roughly half the diameter of the full moon. There is unusually little gas and dust within the Milky Way in this direction and observations towards the distant Universe within this field thus profit from an particularly clear view. That is exactly why this sky area was selected by an international team of astronomers [1] to carry out an ultra-deep survey of X-ray sources with the orbiting Chandra X-Ray Observatory . In order to detect the faintest possible sources, NASA's satellite telescope looked in this direction during an unprecedented total of almost 1 million seconds of exposure time (11.5 days). The main scientific goal of this survey is to understand the nature and evolution of the elusive sources that make up the 'X-ray background' . This diffuse glare in the X-ray sky was discovered by Riccardo Giacconi and his collaborators during a pioneering rocket experiment in 1962. The excellent imaging quality of Chandra (the angular resolution is about 1 arcsec) makes it possible to do extremely deep exposures without encountering problems introduced by the "confusion effect". This refers to the overlapping of images of sources that are seen close to each other in the sky and thus are difficult to study individually. Previous X-ray satellites were not able to obtain sufficiently sharp X-ray images and the earlier deep X-ray surveys therefore suffered severely from this effect. Moreover, Chandra has much better sensitivity at shorter wavelengths (higher energies) which are less affected by obscuration effects. It can therefore better detect faint sources that emit very energetic ("hard") X-rays. X-ray and optical surveys in the Chandra Deep Field South The one-million second Chandra observations were completed in December 2000. In parallel, a group of astronomers based at institutes in Europe and the USA (the CFDS-team [1]) has been collecting deep images and extensive spectroscopic data with the VLT during the past 2 years (cf. PR Photo 09a/01 ). Their aim was to 'identify' the Chandra X-ray sources, i.e., to unveil their nature and measure their distances. For the identification of these sources, the team has also made extensive use of the observations that were carried out as a part of the comprehensive ESO Imaging Survey Project (EIS). More than 300 X-ray sources were detected in the CDFS by Chandra . A significant fraction of these objects shine so faintly in the optical and near-infrared wavebands that only long-exposure observations with the VLT have been able to detect them. During five observing nights with the FORS1 multi-mode instrument at the 8.2-m VLT ANTU telescope in October and November 2000, the CDFS team was able to identify and obtain spectra of more than one hundred of the X-ray sources registered by Chandra . Nature of the X-ray sources The first results from this study have now confirmed that the 'hard' X-ray background is mainly due to Active Galactic Nuclei (AGN) . The observations also reveal that a large fraction of them are of comparatively low brightness (referred to as 'low-luminosity AGN'), heavily enshrouded by dust and located at distances of 8,000 - 9,000 million light-years (corresponding to a redshift of about 1 and a look-back time of 57% of the age of the Universe [2]) . It is generally believed that all these sources are powered by massive black holes at their centres. Previous X-ray surveys missed most of these objects because they were too faint to be observed by the telescopes then available, in particular at short X-ray wavelengths ('hard X-ray photons') where more radiation from the highly active centres is able to pass through the surrounding, heavily absorbing gas and dust clouds. Other types of well-known X-ray sources, e.g., QSOs ('quasars' = high-luminosity AGN) as well as clusters or groups of galaxies were also detected during these observations. Studies of all classes of objects in the CDFS are also being carried out by several other European groups. This sky field, already a standard reference in the southern hemisphere, will be the subject of several multi-wavelength investigations for many years to come. A prime example will be the Great Observatories Origins Deep Survey (GOODS) which will be carried out by the NASA SIRTF infrared satellite in 2003. Discovery of a distant Type II Quasar ESO PR Photo 09b/01 ESO PR Photo 09b/01 [Preview - JPEG: 400 x 352 pix - 56k] [Normal - JPEG: 800 x 703 pix - 128k] Caption : PR Photo 09b/01 displays the optical spectrum of the distant Type II Quasar CXOCDFS J033229.9 -275106 in the Chandra Deep Field South (CDFS), obtained with the FORS1 multi-mode instrument at VLT ANTU. Strong, redshifted emission lines of Hydrogen and ionised Helium, Oxygen, Nitrogen and Carbon are marked. Technical information about this photo is available below. One particular X-ray source that was identified with the VLT during the present investigation has attracted much attention - it is the discovery of a dust-enshrouded quasar (QSO) at very high redshift ( z = 3.7, corresponding to a distance of about 12,000 million light-years; [2]), cf. PR Photo 09a/01 and PR Photo 09b/01 . It is the first very distant representative of this elusive class of objects (referred to as ' Type II Quasars ') which are believed to account for approximately 90% of the black-hole-powered quasars in the distant Universe. The 'sum' of the identified Chandra X-ray sources in the CDFS was found to match both the intensity and the spectral properties of the observed X-ray background. This important result is a significant step forward towards the definitive resolution of this long-standing cosmological problem. Naturally, ESO astronomer Piero Rosati and his colleagues are thrilled: " It is clearly the combination of the new and detailed Chandra X-ray observations and the enormous light-gathering power of the VLT that has been instrumental to this success. " However, he says, " the identification of the remaining Chandra X-ray sources will be the next challenge for the VLT since they are extremely faint. This is because they are either heavily obscured by dust or because they are extremely distant ". More Information This Press Release is issued simultaneously with a NASA Press Release (see also the Harvard site ). Some of the first results are described in a research paper ("First Results from the X-ray and Optical Survey of the Chandra Deep Field South" available on the web at astro-ph/0007240. More information about science results from the Chandra X-Ray Observatory may be found at: http://asc.harvard.edu/. The optical survey of CDFS at ESO with the Wide-Field Imager is described in connection with PR Photos 46a-b/99 ('100,000 galaxies at a glance'). An image of the Chandra Deep Field South is available at the ESO website on the EIS Image Gallery webpage. . Notes [1]: The Chandra Team is lead by Riccardo Giacconi (Association of Universities Inc. [AUI], Washington, USA) and includes: Piero Rosati , Jacqueline Bergeron , Roberto Gilmozzi , Vincenzo Mainieri , Peter Shaver (European Southern Observatory [ESO]), Paolo Tozzi , Mario Nonino , Stefano Borgani (Osservatorio Astronomico, Trieste, Italy), Guenther Hasinger , Gyula Szokoly (Astrophysical Institute Potsdam [AIP], Germany), Colin Norman , Roberto Gilli , Lisa Kewley , Wei Zheng , Andrew Zirm , JungXian Wang (Johns Hopkins University [JHU], Baltimore, USA), Ken Kellerman (National Radio Astronomy Observatory [NRAO], Charlottesville, USA), Ethan Schreier , Anton Koekemoer and Norman Grogin (Space Telescope Science Institute (STScI), Baltimore, USA). [2] In astronomy, the redshift denotes the fraction by which the lines in the spectrum of an object are shifted towards longer wavelengths. The observed redshift of a distant galaxy or quasar gives a direct estimate of the apparent recession velocity as caused by the universal expansion. Since the expansion rate increases with the distance, the velocity is itself a function (the Hubble relation) of the distance to the object. Redshifts of 1 and 3.7 correspond to when the Universe was about 43% and 12% of its present age. The distances indicated in this Press Release depend on the cosmological model chosen and are based on an age of 19,000 million years. Technical information about the photos PR Photo 09a/01 shows B-, R- and I-band images of a 20 x 20 arcsec 2 area within the CDFS, centred on the Type II Quasar CXOCDFS J033229.9 -275106 . They were obtained with the MPG/ESO 2.2-m telescope and the Wide-Field Imager (WFI) at La Silla (B-band; 8 hrs exposure time) and the 8.2-m VLT ANTU telescope with the FORS1 multi-mode instrument at Paranal (R- and I-bands; each 2 hrs exposure). The measured magnitudes are R=23.5 and I=22.7. The overlaid contours show the associated Chandra X-ray source (smoothed with a sigma = 1 arcsec gaussian profile). North is up and East is left. The spectrum shown in PR Photo 09b/01 was obtained on November 25, 2000, with VLT ANTU and FORS1 in the multislit mode (150-I grism, 1.2 arcsec slit). The exposure time was 3 hours.

New insights on Ba overabundance in open clusters. Evidence for the intermediate neutron-capture process at play?

NASA Astrophysics Data System (ADS)

Mishenina, T.; Pignatari, M.; Carraro, G.; Kovtyukh, V.; Monaco, L.; Korotin, S.; Shereta, E.; Yegorova, I.; Herwig, F.

2015-02-01

Recently, an increasing number of studies were devoted to measure the abundances of neutron-capture elements heavier than iron in stars belonging to Galactic Open Clusters (OCs). OCs span a sizeable range in metallicity (-0.6 ≤ [Fe/H] ≤ +0.4), and they show abundances of light elements similar to disc stars of the same age. A different pattern is observed for heavy elements. A large scatter is observed for Ba, with most OCs showing [Ba/Fe] and [Ba/La] overabundant with respect to the Sun. The origin of this overabundance is not clearly understood. With the goal of providing new observational insights, we determined radial velocities, atmospheric parameters and chemical composition of 27 giant stars members of five OCs: Cr 110, Cr 261, NGC 2477, NGC 2506 and NGC 5822. We used high-resolution spectra obtained with the UVES spectrograph at European Southern Observatory Paranal. We perform a detailed spectroscopic analysis of these stars to measure the abundance of up to 22 elements per star. We study the dependence of element abundance on metallicity and age with unprecedented detail, complementing our analysis with data culled from the literature. We confirm the trend of Ba overabundance in OCs, and show its large dispersion for clusters younger than ˜4 Gyr. Finally, the implications of our results for stellar nucleosynthesis are discussed. We show in this work that the Ba enrichment compared to other neutron-capture elements in OCs cannot be explained by the contributions from the slow neutron-capture process and the rapid neutron-capture process. Instead, we argue that this anomalous signature can be explained by assuming an additional contribution by the intermediate neutron-capture process.

Catching a Falling Star

NASA Astrophysics Data System (ADS)

2004-07-01

ESO's Very Large Telescope Obtains Unique Spectrum of a Meteor Summary While observing a supernova in a distant galaxy with the FORS instrument on ESO's Very Large Telescope at the Paranal Observatory (Chile), astronomers were incredibly lucky to obtain serendipitously a high quality spectrum of a very large meteor in the terrestrial atmosphere. The VLT spectrograph provided a well calibrated spectrum, making it a reference in this field of research. From this spectrum, the temperature of the meteor trail was estimated to be about 4600 degrees centigrade. The serendipitous spectrum reveals the telltale meteor emissions of oxygen and nitrogen atoms and nitrogen molecules. The VLT spectrum was the first to reveal the far red range where carbon emission lines are predicted; the absence of the lines puts constraints on the role of atmospheric chemistry when life started on earth. Because the VLT is tuned to observe objects far out in space, it focuses at infinity. The meteor, being "only" 100 km above the telescope, therefore appears out of focus in the field of view. PR Photo 22a/04: Meteor Caught in the Act (MASCOT) PR Photo 22b/04: Spectrum of a Meteor (FORS1/VLT) PR Photo 22c/04: Details of the Meteor Spectrum (FORS1/VLT) Astronomers' luck ESO PR Photo 22a/04 ESO PR Photo 22a/04 Meteor Caught in the Act (MASCOT) [Preview - JPEG: 426 x 400 pix - 85k] [Normal - JPEG: 851 x 800 pix - 187k] [Full Res - JPEG: 2567 x 2413 pix - 908k] Captions: ESO PR Photo 22a/04 shows the trail of a bright meteor, photographed by the Mini All-Sky Cloud Observation Tool (MASCOT) at the ESO Paranal Observatory. MASCOT consists of a small CCD camera behind a fish-eye objective. It typically takes 90s exposures every 3 minutes and helps astronomers inside the VLT Control Room to keep an eye on the sky. The main purpose of MASCOT is to monitor the clouds over Paranal but it also observes from time to time serendipitous events like meteor showers, atmospheric phenomena, artificial satellites, etc. This image was obtained by MASCOT on August 25, 2002 and shows a meteor caught in the act. (Note that this is not the meteor whose spectrum was recorded). The Milky Way is also clearly visible in the centre. A popular saying states that when you see a meteor, you may make a wish. While astronomers cannot promise that it will be realised, a team of astronomers [1] have indeed seen a dream come true! On May 12, 2002, they were lucky to record the spectrum of a bright meteor when it happened - by sheer chance and against all reasonable odds - to cross the narrow slit of the FORS1 instrument on the ESO Very Large Telescope. At the time of this unlikely event, the telescope was performing a series of 20-minute spectroscopic exposures of a supernova in a distant galaxy in order to establish constraints on the dark energy content of the Universe (see e.g. ESO PR 21/98). Thanks to its enormous light-collecting and magnifying power, the VLT recorded the spectrum of the meteor trail perpendicular to its path on one of these exposures. "We really hit the jackpot", says ESO astronomer Emmanuel Jehin: "Chances of capturing a meteor in the narrow slit of the FORS1 spectrograph are about as big as for me winning the national lottery." Meteor spectra have on occasion been obtained serendipitously during photographic star spectra surveys. But this is now maybe the only meteor spectrum recorded with a large telescope and a modern spectrograph. The spectrum covers the wavelength range from 637 to 1050 nm, which is dominated by emissions from air atoms and molecules in the meteor path and teach us about the collision processes in the wake of a meteoroid. The rapid motion of the meteor across the sky resulted in a very brief exposure while crossing the narrow spectrograph slit - only 1/50 of a millisecond! - and despite the relative brightness of the meteor it was only thanks to the VLT's great light-gathering power that any record was procured. The meteor was estimated at magnitude -8, or nearly as bright as the first-quarter Moon. Although it is not possible to be sure from which shower this meteor belongs, a possible candidate is the Southern May Ophiuchid shower which appears from a direction just east of the bright star Antares. The shower contributes only one or two meteors per hour but was one of the stronger showers of that night. Telltale emissions ESO PR Photo 22b/04 ESO PR Photo 22b/04 Spectrum of a Meteor (FORS1/VLT) [Preview - JPEG: 426 x 400 pix - 91k] [Normal - JPEG: 851 x 800 pix - 232k] [Full Res - JPEG: 2567 x 2413 pix - 2.1M] ESO PR Photo 22c/04 ESO PR Photo 22c/04 Details of the Meteor Spectrum (FORS1/VLT) [Preview - JPEG: 1006 x 400 pix - 122k] [Normal - JPEG: 2011 x 800 pix - 236k] [Full Res - JPEG: 3414 x 1358 pix - 957k] Captions: ESO PR Photo 22b/04 shows the spectrum of a bright meteor, as observed serendipitously by the multi-mode FORS 1 instrument on the ESO Very Large Telescope during the night of May 12-13, 2002, in front of a photo of the VLT enclosures and with a meteor trail inserted in the sky (montage). The position of the meteor trail on the narrow slit of FORS (not to scale) is also indicated. The lower panel shows the spectrum of the meteor, following removal of the supernova spectrum and before (up) and after (down) removal of the spectrum of the night sky by image processing. Several emission lines from colliding Oxygen and Nitrogen atoms (sharp emissions) and molecules (broad emissions) are visible. ESO PR Photo 22c/04 illustrates details of the extracted VLT meteor spectrum (solid line): the intensity (in arbitrary units) is shown as a function of the wavelength. The dashed line is a theoretical model of the spectrum of air heated to a temperature of 4600 degrees at an altitude of 95 km. "At first, the bright trace across the supernova spectrum was a puzzle, but then I realized that the spectroscopic signature was that of our atmosphere being bombarded," says astronomer Remi Cabanac of the Catholic University of Santiago de Chile. "We asked around to see if others in our country had witnessed the meteor, but it seems we at the VLT were the only ones, perhaps not too surprising as Paranal is located in the middle of the empty desert." And unfortunately for the astronomers, the MASCOT all-sky camera (e.g. PR Photo 22a/04) was not yet in operation at that time. The VLT spectrograph provided a well calibrated spectrum of the meteor emission, making it a reference in this field of research. The meteor emission results from collisions between air molecules, knocked to high speeds after initial collision with the meteoroid. Closer inspection of the spectrum revealed about 20 telltale meteor emissions of oxygen and nitrogen atoms and nitrogen molecules (see PR Photo 22b/04 and 22c/04). The ratio of atomic and molecular emissions could be used as a "thermometer" to measure the conditions in the meteor-induced hot gas in the wake of the meteoroid, by means of laboratory measurements and meteor models that calibrate the VLT data. From here to infinity "To our surprise, we found the meteor trail to be wider than expected and also that the meteor's heat appeared evenly distributed in the trail, with the temperature varying only from about 4,570 to 4,650 degrees across the trail," says meteor specialist, astronomer Peter Jenniskens of the SETI Intitute, who analysed the data together with Christophe Laux of the Ecole Centrale Paris (France) and Iain Boyd of the University of Michigan at Ann Arbor (USA). "We later realised that this was due to the fact that, as seen by the VLT, the meteor trail was out of focus, even though it was 100 kilometres away!" The VLT is indeed focussed at infinity, which is perfect for most astronomical objects that it routinely observes. But not for meteoroids entering the atmosphere above Paranal. A point at 100 kilometres distance will appear as a small circle of diameter 15 arcsec at the VLT focal plane. This corresponds to roughly half of the maximum apparent diameter of Mars in the evening sky! It is the same effect as when you try to photograph your children with a forest in the background. If you focus your camera on the distant forest, then (in most cases) your children will be out of focus. Or to put this in another way, the VLT is clearly not very suited to observe ships passing by on the Pacific Ocean, just 12 km from Paranal! No Trace of Carbon The meteor spectrum also provided a first view of such an object in the near-infrared window between wavelengths 900 and 1050 nm. This spectral region contains relatively strong lines of atomic carbon, but no such emissions were detected. "We calculated that these lines should have been visible if all atmospheric carbon dioxide in the meteor path was dissociated into carbon and oxygen atoms," says Jenniskens, "but they were conspicuously absent". This observation is important because it sets new constraints on the efficiency of meteor-induced atmospheric chemistry at the time when life began on our planet. Appendix: Cosmic showers Meteoroids are small grains of rocks orbiting the Sun. Far smaller than asteroids, they make their presence known to us in a dramatic and beautiful way when they enter earth's atmosphere and burn up, producing a short glowing trail in the night sky, rarely lasting more than a second or two - a meteor. Most meteoroids are completely destroyed at altitudes between 80 and 110 km, but some of the bigger ones make it to the ground. Here they may be collected as meteorites. Many meteoroids originate as fragments of asteroids and appear to be unaltered since the formation of the Solar System, some 4500 million years ago. Based on the peculiar composition of some meteorites, we know that a small fraction of meteoroids originate from the Moon, Mars or the large asteroid Vesta. They obviously result from major impacts on these bodies which blasted rock fragments into space. These fragments then orbit the Sun and may eventually collide with the Earth. Comets are another important source of meteoroids and perhaps the most spectacular. After many visits near the Sun, a comet "dirty-snowball" nucleus of ice and dust decays and fragments, leaving a trail of meteoroids along its orbit. Some "meteoroid streams" cross the earth's orbit and when our planet passes through them, some of these particles will enter the atmosphere. The outcome is a meteor shower - the most famous being the "Perseids" in the month of August [2] and the "Leonids" in November. Thus, although meteors are referred to as "shooting" or "falling stars" in many languages, they are of a very different nature. More information The research presented in this paper is published in the journal Meteoritics and Planetary Science, Vol. 39, Nr. 4, p. 1, 2004 ("Spectroscopic anatomy of a meteor trail cross section with the ESO Very Large Telescope", by P. Jenniskens et al.). Notes [1] The team is composed of Peter Jenniskens (SETI Institute, USA), Emmanuël Jehin (ESO), Remi Cabanac (Pontificia Universidad Catolica de Chile), Christophe Laux (Ecole Centrale de Paris, France), and Iain Boyd (University of Michigan, USA). [2] The maximum of the Perseids is expected on August 12 after sunset and should be easily seen.

HIGH-CADENCE, HIGH-CONTRAST IMAGING FOR EXOPLANET MAPPING: OBSERVATIONS OF THE HR 8799 PLANETS WITH VLT/SPHERE SATELLITE-SPOT-CORRECTED RELATIVE PHOTOMETRY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Apai, Dániel; Skemer, Andrew; Hanson, Jake R.

Time-resolved photometry is an important new probe of the physics of condensate clouds in extrasolar planets and brown dwarfs. Extreme adaptive optics systems can directly image planets, but precise brightness measurements are challenging. We present VLT/SPHERE high-contrast, time-resolved broad H-band near-infrared photometry for four exoplanets in the HR 8799 system, sampling changes from night to night over five nights with relatively short integrations. The photospheres of these four planets are often modeled by patchy clouds and may show large-amplitude rotational brightness modulations. Our observations provide high-quality images of the system. We present a detailed performance analysis of different data analysismore » approaches to accurately measure the relative brightnesses of the four exoplanets. We explore the information in satellite spots and demonstrate their use as a proxy for image quality. While the brightness variations of the satellite spots are strongly correlated, we also identify a second-order anti-correlation pattern between the different spots. Our study finds that KLIP reduction based on principal components analysis with satellite-spot-modulated artificial-planet-injection-based photometry leads to a significant (∼3×) gain in photometric accuracy over standard aperture-based photometry and reaches 0.1 mag per point accuracy for our data set, the signal-to-noise ratio of which is limited by small field rotation. Relative planet-to-planet photometry can be compared between nights, enabling observations spanning multiple nights to probe variability. Recent high-quality relative H-band photometry of the b–c planet pair agrees to about 1%.« less

The Integration of Internal and External Training Load Metrics in Hurling

PubMed Central

Doran, Dominic; Akubat, Ibrahim; Collins, Kieran

2016-01-01

Abstract The current study aimed to assess the relationship between the hurling player’s fitness profile and integrated training load (TL) metrics. Twenty-five hurling players performed treadmill testing for VO2max, the speed at blood lactate concentrations of 2 mmol•L-1 (vLT) and 4 mmol•L-1 (vOBLA) and the heart rate-blood lactate profile for calculation of individual training impulse (iTRIMP). The total distance (TD; m), high speed distance (HSD; m) and sprint distance (SD; m) covered were measured using GPS technology (4-Hz, VX Sport, Lower Hutt, New Zealand) which allowed for the measurement of the external TL. The external TL was divided by the internal TL to form integration ratios. Pearson correlation analyses allowed for the assessment of the relationships between fitness measures and the ratios to performance during simulated match play. External measures of the TL alone showed limited correlations with fitness measures. Integrated TL ratios showed significant relationships with fitness measures in players. TD:iTRIMP was correlated with aerobic fitness measures VO2max (r = 0.524; p = 0.006; 95% CI: 0.224 to 0.754; large) and vOBLA (r = 0.559; p = 0.003; 95% CI: 0.254 to 0.854; large). HSD:iTRIMP also correlated with aerobic markers for fitness vLT (r = 0.502; p = 0.009; 95% CI: 0.204 to 0.801; large); vOBLA (r = 0.407; p = 0.039; 95% CI: 0.024 to 0.644; moderate). Interestingly SD:iTRIMP also showed significant correlations with vLT (r = 0.611; p = 0.001; 95% CI: 0.324 to 0.754; large). The current study showed that TL ratios can provide practitioners with a measure of fitness as external performance alone showed limited relationships with aerobic fitness measures. PMID:28149425

The unusual N IV] -emitter galaxy GDS J033218.92-275302.7: star formation or AGN-driven winds from a massive galaxy at z = 5.56

NASA Astrophysics Data System (ADS)

Vanzella, E.; Grazian, A.; Hayes, M.; Pentericci, L.; Schaerer, D.; Dickinson, M.; Cristiani, S.; Giavalisco, M.; Verhamme, A.; Nonino, M.; Rosati, P.

2010-04-01

Aims: We investigate the nature of the source GDS J033218.92-275302.7 at redshift ~5.56. Methods: The spectral energy distribution of the source is well-sampled by 16 bands photometry from UV-optical (HST and VLT), near infrared, near infrared (VLT) to mid-infrared (Spitzer). The detection of a signal in the mid-infrared Spitzer/IRAC bands 5.8, 8.0 μm - where the nebular emission contribution is less effective - suggests that there is a Balmer break, the signature of an underlying stellar population formed at earlier epochs. The high-quality VLT/FORS2 spectrum shows a clear Lyα emission line, together with semi-forbidden N iv] 1483.3-1486.5 also in emission. These lines imply a young stellar population. In particular, the N iv] 1483.3-1486.5 feature (if the source is not hosting an AGN) is a signature of massive and hot stars with an associated nebular emission. Conversely, it may be a signature of an AGN. The observed SED and the Lyα emission line profile were modeled carefully to investigate the internal properties of the source. Results: From the SED-fitting with a single and a double stellar population and from the Lyα modeling, it turns out that the source seems to have an evolved component with a stellar mass of ~5 × 1010 M⊙ and age ~0.4 Gyr, and a young component with an age of ~0.01 Gyr and star formation rate in the range of 30-200 M⊙ yr-1. The limits on the effective radius derived from the ACS/z850 and VLT/Ks bands indicate that this galaxy is denser than the local ones with similar mass. A relatively high nebular gas column density is favored from the Lyα line modeling (NHI ⪆ 1021 cm-2). A vigorous outflow (~ 450 km s-1) has been measured from the optical spectrum, consistent with the Lyα modeling. From ACS observations it turns out that the region emitting Lyα photons is spatially compact and has a similar effective radius (~0.1 kpc physical) estimated at the ~1400 Å rest-frame wavelength, whose emission is dominated by the stellar continuum and/or AGN. The gas is blown out from the central region, but, given the mass of the galaxy, it is uncertain whether it will pollute the IGM to large distances. We argue that a burst of star formation in a dense gas environment is active (possibly containing hot and massive stars and/or a low luminosity AGN), superimposed on an already formed fraction of stellar mass. Based on observations made at the European Southern Observatory, Paranal, Chile (ESO program 170.A-0788 The Great Observatories Origins Deep Survey: ESO Public Observations of the SIRTF Legacy/HST Treasury/Chandra Deep Field South).

Young massive star clusters in the era of HST and integral field spectroscopy

NASA Astrophysics Data System (ADS)

Zeidler, Peter; Nota, Antonella; Sabbi, Elena; Grebel, Eva K.; Pasquali, Anna

2018-01-01

With an age of 1 – 2 Myr at a distance of 4 kpc and a total stellar mass of 3.7×104 M⊙, Westerlund 2 (Wd2) is one of the most massive young star clusters in the Milky Way. We present a detailed analysis of its prominent pre-main-sequence population using the data of a high-resolution multi-band survey in the optical and near-infrared with the Hubble Space Telescope (HST), in combination with our spectroscopic survey, observed with the VLT/MUSE integral field unit. With our derived high-resolution extinction map of the region, which is absolutely essential giving the dominating presences of the gas and dust, we derived the spatial dependence of the mass function and quantify the degree of mass segregation down to 0.65 M⊙ with a completeness level better than 50%. Studying the radial dependence of the mass function of Wd2 and quantifying the degree of mass segregation in this young massive star cluster showed that it consists of two sub-clumps, namely the main cluster and the northern clump. From the MUSE data, we can extract individual stellar spectra and spectral energy distributions of the stars, based on the astrometry, provided by our high-resolution HST photometric catalog. This data will provide us with an almost complete spectral classification of a young massive star cluster down to 1.0 M⊙. The combination of the MUSE data, together with 3 more years of approved HST data will allow us to obtain, for the first time, the 3D motions of the stars with an accuracy of 1-2 km s-2 to determine the stellar velocity dispersion in order to study the fate of Wd2. This information is of great importance to adjust the initial conditions in cluster evolution models in order to connect these young massive star clusters and the old globular cluster population. Additionally, the combination of the photometric and spectroscopic datasets allows us to study the stars and their feedback onto the surrounding HII region simultaneously, as well as peculiar objects such as the massive, eclipsing Wolf-Rayet binary, WR20a or a possible Herbig-Haro object in the northern clump.

Neutron Star Astronomy in the era of the European Extremely Large Telescope

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mignani, Roberto P.

About 25 isolated neutron stars (INSs) are now detected in the optical domain, mainly thanks to the HST and to VLT-class telescopes. The European Extremely Large Telescope(E-ELT) will yield {approx}100 new identifications, many of which from the follow-up of SKA, IXO, and Fermi observations. Moreover, the E-ELT will allow to carry out, on a much larger sample, INS observations which still challenge VLT-class telescopes, enabling studies on the structure and composition of the NS interior, of its atmosphere and magnetosphere, as well as to search for debris discs. In this contribution, I outline future perspectives for NS optical astronomy withmore » the E-ELT.« less

Chandra Observations of the Brightest Sunyaev-Zeldovich Effect Cluster

NASA Astrophysics Data System (ADS)

Hughes, John

2011-09-01

We propose deep Chandra observations of ACT-CL J0102-4915, the brightest Sunyaev-Zeldovich effect cluster discovered by the Atacama Cosmology Telescope and South Pole Telescope surveys. These surveys covered approximately 3000 square degrees and are essentially complete to high redshift. Our recent Chandra and VLT optical data reveal ACL-CL J0102-4915 to be undergoing a major merger. It is likely a high redshift (z=0.870) counterpart to the famous ``bullet'' cluster. New Chandra data will determine the properties of the merger shock and the HST/ACS data will provide a weak lensing mass map.

Late Afternoon at Taruntius

NASA Astrophysics Data System (ADS)

2002-08-01

Thirty-three years after the first manned landing on the Moon, the ESO Very Large Telescope (VLT) has obtained what may be the sharpest image of the lunar surface ever recorded from the ground, cf. PR Photo 19a/02 . It was made with the NAOS-CONICA (NACO) adaptive optics camera mounted on the ESO VLT 8.2-m YEPUN telescope at the Paranal Observatory. The photo shows an area about 700 km from the Apollo XI landing site. The location is in the Eastern hemisphere, just North of the lunar equator, and right between two of the major "seas", Mare Tranquillitatis (Sea of Tranquillity) and Mare Foecunditatis (Sea of Fertility). The field-of-view measures about 60 x 45 km 2 (taking into account the foreshortening because of the viewing angle [2]), with part of a sunlit, 10-km wide crater named Cameron [1] surrounded by a comparatively level terrain, bordered by some hills and, not least, with an incredible number of smaller craters. The site of this NACO photo is situated at the rim of an older, rather eroded 56-km crater, Taruntius [1]. A small part of the multiple walls of that crater are seen in the upper right corner and also to the left of the bottom centre of PR Photo 19a/02 . The centre of Taruntius is near the lower right corner of the photo. The rather flat terrain to the left in the photo corresponds to an "opening" in the crater walls. At the time of the exposure, the Sun was approximately 7° above the Western horizon to the left [2], and the shadows are therefore quite prominent, approx. 8 times longer than the elevation of the corresponding peaks and hills. The nominal image sharpness is 0.07 arcsec, or about 130 metres on the lunar surface (in the N-S direction). Elevation differences of a few tens of metres only are therefore visible by the shadows they cast. The VLT image represents what an astronaut (with normal eye acuity of 1 arcmin) would see from 400 km above the surface. Lunar surface formations ESO PR Photo 19b/02 ESO PR Photo 19b/02 [Preview - JPEG: 462 x 400 pix - 66k] [Full-Res - JPEG: 1250 x 1082 pix - 656k] Caption : PR Photo 19b/02 is a computer-processed version of PR Photo 19a/02 , in which the lunar surface is now viewed directly "from above". Located at 46° East lunar longitude, 6° North lunar latitude, this area is viewed from the VLT at an inclined angle and the craters therefore all appear as ellipses in the NACO image. However, taking into account the direction of the line-of-sight at the time of the observation [2], this view can be "rectified" by simple image processing. The corresponding "view from above" is shown in PR Photo 19b/02 ; most of the craters in the field now appear quite round. Many different types of lunar surface formations are visible in the VLT photo. In addition to the numerous impact craters of all sizes, there are also hills and ridges of a great variety of shapes, as well as a prominent "valley" (a "Rima", or fissure) that stretches nearly 50 km through the photo in East-West direction. It has been identified on earlier photos and as it is situated inside that crater, it was given the name "Rimae Taruntius" in 1985. It is very well resolved in this photo and resembles "Rima Hadley" that was visited by the Apollo 15 astronauts in 1971, but is much smaller. The mean width is about 600 metres (12 pixels). The bottom is in the shadows and the depth is therefore unknown. It is overlapped by several smaller craters that must have been caused by impacts after this depression was formed. Measuring the length of the shadows, it is possible to infer the height of some of the formations. For instance, the shadows of the two peaks at the lower centre of the photo are about 4 km long, indicating that these formations are about 500 metres tall. The surroundings ESO PR Photo 19c/02 ESO PR Photo 19c/02 [Preview - JPEG: 482 x 400 pix - 77k] [Normal - JPEG: 964 x 800 pix - 440k] [Full-Res - JPEG: 2408 x 1998 pix - 1.6M] Caption : Where is the NACO field at the Taruntius crater located on the Moon? A 400 x 400 km 2 area surrounding this crater is shown in the right panel of PR Photo 19c/02 ; it has been reproduced from a photo mosaique with 500-metre resolution based on exposures made in 1994 by NASA's "Clementine" spacecraft in lunar orbit [3]. Taruntius , Cameron and other craters in this area are identified in the diagram at the lower left. The area covered by the Clementine photo is outlined on a photo of the entire Moon (upper left), obtained at nearly the same phase as when the NACO image was made [4]. This area around Taruntius was imaged in 1994 by the NASA Clementine spacecraft when it mapped the entire lunar surface at 125-250 metres per pixel. The data led to the first complete map of the mineralogy (rock types) of the Moon. The Clementine image shown here ( PR Photo 19c/02 ) helps to identify the small area depicted by NACO. It is part of the Clementine Basemap Mosaic and has been observed with the onboard Ultraviolet/Visible camera through an optical filter centred at 750 nm [3]. It covers a field-of-view of about 400 x 400 km 2 , with a nominal resolution of about 500 metres. Many craters are well visible, including Taruntius with Cameron on the upper left sector of the multiple rim. Testing the NAOS-CONICA instrument This splendid VLT image is a by-product of the ongoing, thorough testing of the NAOS-CONICA (NACO) Adaptive Optics facility , recently installed at the 8.2-m YEPUN telescope, the fourth unit of the Very Large Telescope (VLT) at the ESO Paranal Observatory. This major astronomical instrument has already delivered other impressive views of the Universe, cf. ESO PR 25/01 and ESO PR Photos 04a-c/02. Normally, NACO functions by "locking" on a point-like guide star, correcting the image smearing caused in the turbulent terrestrial atmophere by measuring the deformation of the recorded image of that star. However, in the morning of April 30, 2002, shortly before sunrise, the astronomers and engineers working with NACO decided to do a test of wavefront sensing on an extended celestial object . For this, the giant telescope was turned towards the Moon, at that moment seen in the southern constellation of Ophiuchus, high above the western horizon at Paranal [2]. Guiding the advanced instrument on a sunlit lunar peak in the area between Mare Tranquillitatis and Mare Foecunditatis, a short exposure (0.22 seconds) was made through a narrow-band near-infrared filter (at wavelength 2.3 µm), with the adaptive optics (AO) activated in closed-loop mode. The telescope was set to track on that lunar mountain and the flexible AO mirror in NACO superbly "refocussed" the 25 x 25 arcsec 2 field-of-view. Although the atmosphere above Paranal was rather turbulent that morning - the nominal seeing was measured as 1.5 arcsec - and despite the use of an extended feature for the guiding, the NACO adaptive optics compensation achieved nearly theoretical image sharpness, about 0.068 arcsec for this waveband. Images of other areas on the lunar surface may be attempted in the future with the VLT and NACO. Other lunar images An impressive ESO photo of the waning Moon was obtained in 1999 with the WFI camera at the La Silla Observatory, cf. ESO PR 02/99. Many websites display fine images of the Moon, obtained with professional and amateur telescopes. Many links are available at the dedicated page maintained by the Centre de Données Planétaires at the Institut d'Astrophysique Spatiale (Paris, France). The Hubble Space Telescope (HST) did not photograph the Taruntius area, but an excellent photo of the Copernicus crater was published in 1999. Notes [1]: The lunar crater Taruntius (lunar co-ordinates: 5.6° N; 46.5° E) was named in 1935 by the International Astronomical Union (IAU) after the Roman philosopher Lucius Firmanus Taruntius (? - 86 B.C.). It measures about 56 km across. The 10-km crater Cameron (6.2° N; 45.9° E) was named by the IAU in 1972 after the American astronomer Robert Curry Cameron (1925 - 1972). Names of surface features on planets and their natural satellites, including the Earth's Moon, are allocated by the "IAU Working Group for Planetary System Nomenclature" and published on the web in the "Gazetteer of Planetary Nomenclature". [2]: The NACO image was exposed on April 30, 2002, at 09:42 hrs UT. The geometrical circumstances of this observation were the following: the Moon was located at (Azimuth Az = 266° Elevation h = +62°) in the sky above the VLT at the Paranal Observatory; the Earth (Paranal) was located at ( Az = 263° h = +50°) and the Sun at ( Az = 268° h = +7°) in the lunar sky above the Cameron crater. The distance from Paranal to the Moon was about 370,000 km. [3]: Acknowledgment: The Clementine Basemap Mosaic was compiled for the National Aeronautics and Space Administration (NASA) by the United States Geological Survey (USGS) under the direction of Dr. Alfred S. McEwen, principal Investigator (now with the University of Arizona). The DoD/BMDO Clementine spacecraft was built and operated by the Naval Research Laboratory, with remote-sensing instruments from the Lawrence Livermore National Laboratory. The field shown in PR Photo 19c/02 was reproduced from a 0.5-km full resolution frame (BM14N045) for which a browse page is available on the web; the file itself is at: http://pdsimage.wr.usgs.gov/CDROMS/cl_3015/bm90_90/bm14n045.img. Another image of the Taruntius area with 100-metre pixels is available at http://pdsimage.wr.usgs.gov/CDROMS/cl_3003/bi00_35n/bi03n045.img. A comprehensive collection of data gathered by the instruments onboard Clementine may be found via the Clementine Navigator of the Jet Propulsion Laboratory Planetary Data System. Clementine also obtained images of a small fraction of the lunar surface by means of a High Resolution Camera (HRC) with a nominal resolution of 7 to 20 metres. However, none of these covered the area shown in the NACO photo. [4]: Acknowledgment: The image of the entire Moon shown at the upper left of PR Photo 19c/02 was obtained with a 12-inch refractor when the Moon was "aged" 17.9 days, i.e. almost the same phase as when the NACO image was taken. It is reproduced from the Berliner Mond-Atlas (3rd edition, 1989), published by the Wilhelm-Foerster-Sternwarte - Berlin (Germany). ESO PR Photos 19a-c/02 may be reproduced, if credit is given to the European Southern Observatory (ESO). Please note the additional credits needed for PR Photo 19c/02 , as stated in Notes 3 and 4.

Measuring FeO variation using astronomical spectroscopic observations

NASA Astrophysics Data System (ADS)

Unterguggenberger, Stefanie; Noll, Stefan; Feng, Wuhu; Plane, John M. C.; Kausch, Wolfgang; Kimeswenger, Stefan; Jones, Amy; Moehler, Sabine

2017-03-01

Airglow emission lines of OH, O2, O and Na are commonly used to probe the MLT (mesosphere-lower thermosphere) region of the atmosphere. Furthermore, molecules like electronically excited NO, NiO and FeO emit a (pseudo-) continuum. These continua are harder to investigate than atomic emission lines. So far, limb-sounding from space and a small number of ground-based low-to-medium resolution spectra have been used to measure FeO emission in the MLT. In this study the medium-to-high resolution echelle spectrograph X-shooter at the Very Large Telescope (VLT) in the Chilean Atacama Desert (24°37' S, 70°24' W; 2635 m) is used to study the FeO pseudo-continuum in the range from 0.5 to 0.72 µm based on 3662 spectra. Variations of the FeO spectrum itself, as well as the diurnal and seasonal behaviour of the FeO and Na emission intensities, are reported. These airglow emissions are linked by their common origin, meteoric ablation, and they share O3 as a common reactant. Major differences are found in the main emission peak of the FeO airglow spectrum between 0.58 and 0.61 µm, compared with a theoretical spectrum. The FeO and Na airglow intensities exhibit a similar nocturnal variation and a semi-annual seasonal variation with equinoctial maxima. This is satisfactorily reproduced by a whole atmosphere chemistry climate model, if the quantum yields for the reactions of Fe and Na with O3 are 13 ± 3 and 11 ± 2 % respectively. However, a comparison between the modelled O3 in the upper mesosphere and measurements of O3 made with the SABER satellite instrument suggests that these quantum yields may be a factor of ˜ 2 smaller.

Surprise Discovery of Highly Developed Structure in the Young Universe

NASA Astrophysics Data System (ADS)

2005-03-01

ESO-VLT and ESA XMM-Newton Together Discover Earliest Massive Cluster of Galaxies Known Summary Combining observations with ESO's Very Large Telescope and ESA's XMM-Newton X-ray observatory, astronomers have discovered the most distant, very massive structure in the Universe known so far. It is a remote cluster of galaxies that is found to weigh as much as several thousand galaxies like our own Milky Way and is located no less than 9,000 million light-years away. The VLT images reveal that it contains reddish and elliptical, i.e. old, galaxies. Interestingly, the cluster itself appears to be in a very advanced state of development. It must therefore have formed when the Universe was less than one third of its present age. The discovery of such a complex and mature structure so early in the history of the Universe is highly surprising. Indeed, until recently it would even have been deemed impossible. PR Photo 05a/05: Discovery X-Ray Image of the Distant Cluster (ESA XMM-Netwon) PR Photo 05b/05: False Colour Image of XMMU J2235.3-2557 (FORS/VLT and ESA XMM-Newton) Serendipitous discovery ESO PR Photo 05a/05 ESO PR Photo 05a/05 Discovery X-Ray Image of the Distant Cluster (ESA XMM-Newton) [Preview - JPEG: 400 x 421 pix - 106k] [Normal - JPEG: 800 x 842 pix - 843k] [Full Res - JPEG: 2149 x 2262 pix - 2.5M] Caption: ESO PR Photo 05a/05 is a reproduction of the XMM-Newton observations of the nearby active galaxy NGC7314 (bright object in the centre) from which the newly found distant cluster (white box) was serendipitously identified. The circular field-of-view of XMM-Newton is half-a-degree in diameter, or about the same angular size as the Full Moon. The inset shows the diffuse X-ray emission from the distant cluster XMMU J2235.3-2557. Clusters of galaxies are gigantic structures containing hundreds to thousands of galaxies. They are the fundamental building blocks of the Universe and their study thus provides unique information about the underlying architecture of the Universe as a whole. About one-fifth of the optically invisible mass of a cluster is in the form of a diffuse, very hot gas with a temperature of several tens of millions of degrees. This gas emits powerful X-ray radiation and clusters of galaxies are therefore best discovered by means of X-ray satellites (cf. ESO PR 18/03 and 15/04). It is for this reason that a team of astronomers [1] has initiated a search for distant, X-ray luminous clusters "lying dormant" in archive data from ESA's XMM-Newton satellite observatory. Studying XMM-Newton observations targeted at the nearby active galaxy NGC 7314, the astronomers found evidence of a galaxy cluster in the background, far out in space. This source, now named XMMU J2235.3-2557, appeared extended and very faint: no more than 280 X-ray photons were detected over the entire 12 hour-long observations. A Mature Cluster at Redshift 1.4 ESO PR Photo 05b/05 ESO PR Photo 05b/05 False Colour Image of XMMU J2235.3-2557 (FORS/VLT and ESA XMM-Newton) [Preview - JPEG: 400 x 455 pix - 50k] [Normal - JPEG: 800 x 909 pix - 564k] [Full Res - JPEG: 1599 x 1816 pix - 1.5M] Caption: ESO PR Photo 05b/05 is a false colour image of the XMMU J2235.3-2557 cluster of galaxies, overlaid with the X-ray intensity contours derived from the ESA XMM-Newton data. The red channel is a VLT-ISAAC image (exposure time: 1 hour) obtained in the near-infrared Ks-band (at wavelength 2.2 microns); the green channel is a VLT-FORS2 z-band image (910 nm; 480 sec); the blue channel is a VLT-FORS2 R-band image (; 657 nm; 1140 sec). The VLT reveals 12 reddish galaxies, of elliptical types, as members of the cluster. Knowing where to look, the astronomers then used the European Southern Observatory's Very Large Telescope (VLT) at Paranal (Chile) to obtain images in the visible wavelength region. They confirmed the nature of this cluster and it was possible to identify 12 comparatively bright member galaxies on the images (see ESO PR Photo 05b/05). The galaxies appear reddish and are of the elliptical type. They are full of old, red stars. All of this indicates that these galaxies are already several thousand million years old. Moreover, the cluster itself has a largely spherical shape, also a sign that it is already a very mature structure. In order to determine the distance of the cluster - and hence its age - Christopher Mullis, former European Southern Observatory post-doctoral fellow and now at the University of Michigan in the USA, and his colleagues used again the VLT, now in the spectroscopic mode. By means of one of the FORS multi-mode instruments, the astronomers zoomed-in on the individual galaxies in the field, taking spectral measurements that reveal their overall characteristics, in particular their redshift and hence, distance [2]. The FORS instruments are among the most efficient and versatile available anywhere for this delicate work, obtaining on the average quite detailed spectra of 30 or more galaxies at a time. The VLT data measured the redshift of this cluster as 1.4, indicating a distance of 9,000 million light-years, 500 million light years farther out than the previous record holding cluster. This means that the present cluster must have formed when the Universe was less than one third of its present age. The Universe is now believed to be 13,700 million years old. "We are quite surprised to see that a fully-fledged structure like this could exist at such an early epoch," says Christopher Mullis. "We see an entire network of stars and galaxies in place, just a few thousand million years after the Big Bang". "We seem to have underestimated how quickly the early Universe matured into its present-day state," adds Piero Rosati of ESO, another member of the team. "The Universe did grow up fast!" Towards a Larger Sample This discovery was relative easy to make, once the space-based XMM and the ground-based VLT observations were combined. As an impressive result of the present pilot programme that is specifically focused on the identification of very distant galaxy clusters, it makes the astronomers very optimistic about their future searches. The team is now carrying out detailed follow-up observations both from ground- and space-based observatories. They hope to find many more exceedingly distant clusters, which would then allow them to test competing theories of the formation and evolution of such large structures. "This discovery encourages us to search for additional distant clusters by means of this very efficient technique," says Axel Schwope, team leader at the Astrophysical Institute Potsdam (Germany) and responsible for the source detection from the XMM-Newton archival data. Hans Böhringer of the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, another member of the team, adds: "Our result also confirms the great promise inherent in other facilities to come, such as APEX (Atacama Pathfinder Experiment) at Chajnantor, the site of the future Atacama Large Millimeter Array. These intense searches will ultimately place strong constraints on some of the most fundamental properties of the Universe." More information This finding is presented today by Christopher Mullis at a scientific meeting in Kona, Hawaii, entitled "The Future of Cosmology with Clusters of Galaxies". It will also soon appear in The Astrophysical Journal ("Discovery of an X-ray Luminous Galaxy Cluster at z=1.4", by C. R. Mullis et al.). More images and information is available on Christopher Mullis' dedicated web page at http://www.astro.lsa.umich.edu/~cmullis/research/xmmuj2235/. A German version of the press release is issued by the Max Planck Society and is available at http://www.mpg.de/bilderBerichteDokumente/dokumentation/pressemitteilungen/2005/pressemitteilung20050228/presselogin/ .

Surface composition of Europa based on VLT observations

NASA Astrophysics Data System (ADS)

Ligier, N.; Poulet, F.; Carter, J.

2016-12-01

Jupiter's moon Europa may harbor a global salty ocean under an 80-170 km thick outer layer consisting of an icy crust (Anderson et al. 1998). Meanwhile, the 10-50 My old surface, dated by cratering rates (Pappalardo et al. 1999) implies rapid surface recycling and reprocessing that could result in tectonic activity (Kattenhorn et al. 2014) and plumes (Roth et al. 2014). The surface could thus exhibit fingerprints of chemical species, as minerals characteristics of an ocean-mantle interaction and/or organics of exobiological interest, directly originating from the subglacial ocean. In order to re-investigate the composition of Europa's surface, a global mapping campaign of the satellite was performed with the near-infrared integral field spectrograph SINFONI on the Very Large Telescope (VLT) in Chile. The high spectral binning of this instrument (0.5 nm) and large signal noise ratio in comparison to previous observations are adequate to detect sharp absorptions in the wavelength range 1.45-2.45 μm. In addition, the spatially resolved spectra we obtained over five epochs nearly cover the entire surface of Europa with a pixel scale of 12.5 by 25 m.a.s ( 35 by 70 km on Europa's surface), thus permitting a global scale study. Several icy and non-icy compounds were detected and mapped at <100 km resolution. They are unevenly distributed on the moon's surface. Amorphous and crystalline water ice are both present and, in spite of a particularly strong amorphization process likely engendered by the Io plasma torus, the crystalline form is found to be approximately twice as abundant as the amorphous ice based on the analysis of the 1.65 μm band. If the surface is dominated by small and mid-sized water ice grains (25-200 μm), crystalline water-ice grains exhibit spatial inhomogeneities in their distribution. The sulfuric acid hydrate distribution exhibits the typical "bullseye" feature on the trailing hemisphere. The presence of Mg-bearing chlorinated salts (chloride, chlorate, and perchlorate) is supported by linear spectral modeling of the data, while the presence of sulfate salts is challenged. The distribution of some of these species is inconsistent with exogenic processes mainly impacting the trailing orbital hemisphere. These species may be traces of endogenous processes occurring on Europa.

CLASH-VLT: INSIGHTS ON THE MASS SUBSTRUCTURES IN THE FRONTIER FIELDS CLUSTER MACS J0416.1–2403 THROUGH ACCURATE STRONG LENS MODELING

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grillo, C.; Suyu, S. H.; Umetsu, K.

2015-02-10

We present a detailed mass reconstruction and a novel study on the substructure properties in the core of the Cluster Lensing And Supernova survey with Hubble (CLASH) and Frontier Fields galaxy cluster MACS J0416.1–2403. We show and employ our extensive spectroscopic data set taken with the VIsible Multi-Object Spectrograph instrument as part of our CLASH-VLT program, to confirm spectroscopically 10 strong lensing systems and to select a sample of 175 plausible cluster members to a limiting stellar mass of log (M {sub *}/M {sub ☉}) ≅ 8.6. We reproduce the measured positions of a set of 30 multiple images withmore » a remarkable median offset of only 0.''3 by means of a comprehensive strong lensing model comprised of two cluster dark-matter halos, represented by cored elliptical pseudo-isothermal mass distributions, and the cluster member components, parameterized with dual pseudo-isothermal total mass profiles. The latter have total mass-to-light ratios increasing with the galaxy HST/WFC3 near-IR (F160W) luminosities. The measurement of the total enclosed mass within the Einstein radius is accurate to ∼5%, including the systematic uncertainties estimated from six distinct mass models. We emphasize that the use of multiple-image systems with spectroscopic redshifts and knowledge of cluster membership based on extensive spectroscopic information is key to constructing robust high-resolution mass maps. We also produce magnification maps over the central area that is covered with HST observations. We investigate the galaxy contribution, both in terms of total and stellar mass, to the total mass budget of the cluster. When compared with the outcomes of cosmological N-body simulations, our results point to a lack of massive subhalos in the inner regions of simulated clusters with total masses similar to that of MACS J0416.1–2403. Our findings of the location and shape of the cluster dark-matter halo density profiles and on the cluster substructures provide intriguing tests of the assumed collisionless, cold nature of dark matter and of the role played by baryons in the process of structure formation.« less

The European ALMA production antennas: new drive applications for better performances and low cost management

NASA Astrophysics Data System (ADS)

Giacomel, L.; Manfrin, C.; Marchiori, G.

2008-07-01

From the first application on the VLT Telescopes till today, the linear motor identifies the best solution in terms of quality/cost for any technological application in the astronomical field. Its application also in the radio-astronomy sector with the ALMA project represents a whole of forefront technology, high reliability and minimum maintenance. The adoption of embedded electronics on each motor sector makes it a system at present modular, redundant with resetting of EMC troubles.

First results from SAM-FP: Fabry-Perot observations with ground-layer adaptive optics - the structure and kinematics of the core of 30 Doradus

NASA Astrophysics Data System (ADS)

Mendes de Oliveira, C.; Amram, P.; Quint, Bruno C.; Torres-Flores, S.; Barbá, R.; Andrade, D.

2017-08-01

The aim of this paper is to present the first data set obtained with SOAR Adaptive Module-Fabry-Parot (SAM-FP), a Fabry-Perot instrument mounted inside the SOAR telescope Adaptive-Optics Module. This is the only existing imaging Fabry-Perot interferometer using laser-assisted ground-layer adaptive optics. SAM-FP was used to observe the ionized gas, traced by Hα, in the centre of the 30 Doradus starburst (the Tarantula Nebula) in the Large Magellanic Cloud, with high spatial (˜0.6 arcsec, or 0.15 pc) and spectral (R ≃ 11 200) resolution. Radial velocity, velocity dispersion and monochromatic maps were derived. The region displays a mix of narrow, σ ˜ 20 km s-1 profiles and multiple broader profiles with σ ˜ 70-80 km s-1, indicating the complex nature of the nebula kinematics. A comparison with previously obtained VLT/FLAMES spectroscopy demonstrates that the data agree well in the regions of overlap, but the Fabry-Perot data are superior in spatial coverage. A preliminary analysis of the observations finds a new expanding bubble south of R136, with a projected radius of r = 5.6 pc and an expansion velocity of 29 ± 4 km s-1. In addition, the first-time detailed kinematic maps derived here for several complexes and filaments of 30 Doradus allow identification of kinematically independent structures. These data exemplify the power of the combination of a high-order Fabry-Perot with a wide-field imager (3 × 3 arcmin2 GLAO-corrected field of view) for high-resolution spatial and spectral studies. In particular, SAM-FP data cubes are highly advantageous over multifibre or long-slit data sets for nebula structure studies and to search for small-scale bubbles, given their greatly improved spatial coverage. For reference, this paper also presents two appendices with detailed descriptions of the usage of Fabry-Perot devices, including formulae and explanations for understanding Fabry-Perot observations.

Fundamental properties and atmospheric structure of the red supergiant VY Canis Majoris based on VLTI/AMBER spectro-interferometry

NASA Astrophysics Data System (ADS)

Wittkowski, M.; Hauschildt, P. H.; Arroyo-Torres, B.; Marcaide, J. M.

2012-04-01

Aims: We investigate the atmospheric structure and fundamental properties of the red supergiant VY CMa. Methods: We obtained near-infrared spectro-interferometric observations of VY CMa with spectral resolutions of 35 and 1500 using the AMBER instrument at the VLTI. Results: The visibility data indicate the presence of molecular layers of water vapor and CO in the extended atmosphere with an asymmetric morphology. The uniform disk diameter in the water band around 2.0 μm is increased by ~20% compared to the near-continuum bandpass at 2.20-2.25 μm, and in the CO band at 2.3-2.5 μm it is increased by up to ~50%. The closure phases indicate relatively small deviations from point symmetry close to the photospheric layer, and stronger deviations in the extended H2O and CO layers. Making use of the high spatial and spectral resolution, a near-continuum bandpass can be isolated from contamination by molecular and dusty layers, and the Rosseland-mean photospheric angular diameter is estimated to 11.3 ± 0.3 mas based on a PHOENIX atmosphere model. Together with recent high-precision estimates of the distance and spectro-photometry, this estimate corresponds to a radius of 1420 ± 120 R⊙ and an effective temperature of 3490 ± 90 K. Conclusions: VY CMa exhibits asymmetric, possibly clumpy, atmospheric layers of H2O and CO, which are not co-spatial, within a larger elongated dusty envelope. Our revised fundamental parameters put VY CMa close to the Hayashi limit of recent evolutionary tracks of initial mass 25 M⊙ with rotation or 32 M⊙ without rotation, shortly before evolving blueward in the HR-diagram. Based on observations made with the VLT Interferometer (VLTI) at Paranal Observatory under programme ID 386.D-0012.Figures 2, 3 and 5 are available in electronic form at http://www.aanda.org

Discovery of Water at High Spectral Resolution in the Atmosphere of 51 Peg b

NASA Astrophysics Data System (ADS)

Birkby, J. L.; de Kok, R. J.; Brogi, M.; Schwarz, H.; Snellen, I. A. G.

2017-03-01

We report the detection of water absorption features in the day side spectrum of the first-known hot Jupiter, 51 Peg b, confirming the star-planet system to be a double-lined spectroscopic binary. We use high-resolution (R≈ 100,000), 3.2 μ {{m}} spectra taken with CRIRES/VLT to trace the radial-velocity shift of the water features in the planet’s day side atmosphere during 4 hr of its 4.23 day orbit after superior conjunction. We detect the signature of molecular absorption by water at a significance of 5.6σ at a systemic velocity of {V}{sys}=-33+/- 2 km s-1, coincident with the 51 Peg host star, with a corresponding orbital velocity {K}{{P}}={133}-3.5+4.3 km s-1. This translates directly to a planet mass of {M}{{p}}={0.476}-0.031+0.032 {M}{{J}}, placing it at the transition boundary between Jovian and Neptunian worlds. We determine upper and lower limits on the orbital inclination of the system of 70^\\circ < I< 82\\buildrel{\\circ}\\over{.} 2. We also provide an updated orbital solution for 51 Peg b, using an extensive set of 639 stellar radial velocities measured between 1994 and 2013, finding no significant evidence of an eccentric orbit. We find no evidence of significant absorption or emission from other major carbon-bearing molecules of the planet, including methane and carbon dioxide. The atmosphere is non-inverted in the temperature-pressure region probed by these observations. The deepest absorption lines reach an observed relative contrast of 0.9× {10}-3 with respect to the host star continuum flux at an angular separation of 3 milliarcseconds. This work is consistent with a previous tentative report of K-band molecular absorption for 51 Peg b by Brogi et al.

A frozen super-Earth orbiting a star at the bottom of the main sequence

NASA Astrophysics Data System (ADS)

Kubas, D.; Beaulieu, J. P.; Bennett, D. P.; Cassan, A.; Cole, A.; Lunine, J.; Marquette, J. B.; Dong, S.; Gould, A.; Sumi, T.; Batista, V.; Fouqué, P.; Brillant, S.; Dieters, S.; Coutures, C.; Greenhill, J.; Bond, I.; Nagayama, T.; Udalski, A.; Pompei, E.; Nürnberger, D. E. A.; Le Bouquin, J. B.

2012-04-01

Context. Microlensing is a unique method to probe low mass exoplanets beyond the snow line. However, the scientific potential of the new microlensing planet discovery is often unfulfilled due to lack of knowledge of the properties of the lens and source stars. The discovery light curve of the super Earth MOA-2007-BLG-192Lb suffers from significant degeneracies that limit what can be inferred about its physical properties. Aims: High resolution adaptive optics images allow us to solve this problem by resolving the microlensing target from all unrelated background stars, yielding the unique determination of magnified source and lens fluxes. This estimation permits the solution of our microlens model for the mass of the planet and its host and their physical projected separation. Methods: We observed the microlensing event MOA-2007-BLG-192 at high angular resolution in JHKs with the NACO adaptive optics system on the VLT while the object was still amplified by a factor 1.23 and then at baseline 18 months later. We analyzed and calibrated the NACO photometry in the standard 2MASS system in order to accurately constrain the source and the lens star fluxes. Results: We detect light from the host star of MOA-2007-BLG-192Lb, which significantly reduces the uncertainties in its characteristics as compared to earlier analyses. We find that MOA-2007-BLG-192L is most likely a very low mass late type M-dwarf (0.084-0.012+0.015 M⊙) at a distance of 660-70+100 pc orbited by a 3.2-1.8+5.2 M⊕ super-Earth at 0.66-0.22+0.51 AU. We then discuss the properties of this cold planetary system. Based on observations under ESO Prog.IDs: 279.C-5044(A) and 383-C.0495(A).

The separation distribution and merger rate of double white dwarfs: improved constraints

NASA Astrophysics Data System (ADS)

Maoz, Dan; Hallakoun, Na'ama; Badenes, Carles

2018-05-01

We obtain new and precise information on the double white dwarf (DWD) population and on its gravitational-wave-driven merger rate by combining the constraints on the DWD population from two previous studies on radial velocity variation. One of the studies is based on a sample of white dwarfs (WDs) from the Sloan Digital Sky Survey (SDSS, which with its low spectral resolution probes systems at separations a < 0.05 au) and the other is based on the ESO-VLT Supernova-Ia Progenitor surveY (SPY, which with its high spectral resolution is sensitive to a < 4 au). From a joint likelihood analysis, the DWD fraction among WDs is fbin = 0.095 ± 0.020 (1σ, random) +0.010 (systematic) in the separation range ≲4 au. The index of a power-law distribution of initial WD separations (at the start of solely gravitational-wave-driven binary evolution), N(a)da ∝ aαda, is α = -1.30 ± 0.15 (1σ) +0.05 (systematic). The Galactic WD merger rate per WD is Rmerge = (9.7 ± 1.1) × 10-12 yr-1. Integrated over the Galaxy lifetime, this implies that 8.5-11 per cent of all WDs ever formed have merged with another WD. If most DWD mergers end as more-massive WDs, then some 10 per cent of WDs are DWD-merger products, consistent with the observed fraction of WDs in a `high-mass bump' in the WD mass function. The DWD merger rate is 4.5-7 times the Milky Way's specific Type Ia supernova (SN Ia) rate. If most SN Ia explosions stem from the mergers of some DWDs (say, those with massive-enough binary components) then ˜15 per cent of all WD mergers must lead to a SN Ia.

Task demand influences relationships among sex, clustering strategy, and recall: 16-word versus 9-word list learning tests.

PubMed

Sunderaraman, Preeti; Blumen, Helena M; DeMatteo, David; Apa, Zoltan L; Cosentino, Stephanie

2013-06-01

We compared the relationships among sex, clustering strategy, and recall across different task demands using the 16-word California Verbal Learning Test-Second Edition (CVLT-II) and the 9-word Philadelphia (repeatable) Verbal Learning Test (PrVLT). Women generally score higher than men on verbal memory tasks, possibly because women tend to use semantic clustering. This sex difference has been established via word-list learning tests such as the CVLT-II. In a retrospective between-group study, we compared how 2 separate groups of cognitively healthy older adults performed on a longer and a shorter verbal learning test. The group completing the CVLT-II had 36 women and 26 men; the group completing the PrVLT had 27 women and 21 men. Overall, multiple regression analyses revealed that semantic clustering was significantly associated with total recall on both tests' lists (P<0.001). Sex differences in recall and semantic clustering diminished with the shorter PrVLT word list. Semantic clustering uniquely influenced recall on both the longer and shorter word lists. However, serial clustering and sex influenced recall depending on the length of the word list (ie, the task demand). These findings suggest a complex nonlinear relationship among verbal memory, clustering strategies, and task demand.

Task Demand Influences Relationships Among Sex, Clustering Strategy, and Recall: 16-Word Versus 9-Word List Learning Tests

PubMed Central

Sunderaraman, Preeti; Blumen, Helena M.; DeMatteo, David; Apa, Zoltan; Cosentino, Stephanie

2013-01-01

Objective We compared the relationships among sex, clustering strategy, and recall across different task demands using the 16-word California Verbal Learning Test–Second Edition (CVLT-II) and the 9-word Philadelphia (repeatable) Verbal Learning Test (PrVLT). Background Women generally score higher than men on verbal memory tasks, possibly because women tend to use semantic clustering. This sex difference has been established via word-list learning tests such as the CVLT-II. Methods In a retrospective between-group study, we compared how 2 separate groups of cognitively healthy older adults performed on a longer and a shorter verbal learning test. The group completing the CVLT-II had 36 women and 26 men; the group completing the PrVLT had 27 women and 21 men. Results Overall, multiple regression analyses revealed that semantic clustering was significantly associated with total recall on both tests’ lists (P < 0.001). Sex differences in recall and semantic clustering diminished with the shorter PrVLT word list. Conclusions Semantic clustering uniquely influenced recall on both the longer and shorter word lists. However, serial clustering and sex influenced recall depending on the length of the word list (ie, the task demand). These findings suggest a complex nonlinear relationship among verbal memory, clustering strategies, and task demand. PMID:23812171

Laboratory results of the AOF system testing

NASA Astrophysics Data System (ADS)

Kolb, Johann; Madec, Pierre-Yves; Arsenault, Robin; Oberti, Sylvain; Paufique, Jérôme; La Penna, Paolo; Ströbele, Stefan; Donaldson, Robert; Soenke, Christian; Suárez Valles, Marcos; Kiekebusch, Mario; Argomedo, Javier; Le Louarn, Miska; Vernet, Elise; Haguenauer, Pierre; Duhoux, Philippe; Aller-Carpentier, Emmanuel; Valenzuela, Jose Javier; Guerra, Juan Carlos

2016-07-01

For two years starting in February 2014, the AO modules GRAAL for HAWK-I and GALACSI for MUSE of the Adaptive Optics Facility project have undergone System Testing at ESO's Headquarters. They offer four different modes: NGS SCAO, LGS GLAO in the IR, LGS GLAO and LTAO in the visible. A detailed characterization of those modes was made possible by the existence of ASSIST, a test bench emulating an adaptive VLT including the Deformable Secondary Mirror, a star simulator and turbulence generator and a VLT focal plane re-imager. This phase aimed at validating all the possible components and loops of the AO modules before installation at the actual VLT that comprises the added complexity of real LGSs, a harsher non-reproducible environment and the adaptive telescope control. In this paper we present some of the major results obtained and challenges encountered during the phase of System Tests, like the preparation of the Acquisition sequence, the testing of the Jitter loop, the performance optimization in GLAO and the offload of low-order modes from the DSM to the telescope (restricted to the M2 hexapod). The System Tests concluded with the successful acceptance, shipping, installation and first commissioning of GRAAL in 2015 as well as the acceptance and shipping of GALACSI, ready for installation and commissioning early 2017.

The VLT Interferometer and its AMBER Instrument: Simulations of Interferometric Imaging in the Wide-Field Mode

NASA Astrophysics Data System (ADS)

Blöcker, T.; Hofmann, K.-H.; Przygodda, F.; Weigelt, G.

We present computer simulations of interferometric imaging with the VLT interferometer and the AMBER instrument. These simulations include both the astrophysical modelling of a stellar object by radiative transfer calculations and the simulation of light propagation from the object to the detector (through atmosphere, telescopes, and the AMBER instrument), simulation of photon noise and detector read-out noise, and finally data processing of the interferograms. The results show the dependence of the visibility error bars on the following observational parameters: different seeing during the observation of object and reference star (Fried parameters r0,object and r0,ref. ranging between 0.9 m and 1.2 m), different residual tip-tilt error (δtt,object and δtt,ref. ranging between 0.1% and 20% of the Airy disk diameter), and object brightness (Kobject=3.5 mag to 13 mag, Kref.=3.5 mag). Exemplarily, we focus on stars in late stages of stellar evolution and study one of its key objects, the dusty supergiant IRC +10 420 that is rapidly evolving on human timescales. We show computer simulations of VLT interferometry of IRC +10 420 with two ATs (wide-field mode, i.e. without fiber optics spatial filters) and discuss whether the visibility accuracy is sufficient to distinguish between different theoretical model predictions.

The influence of acutely administered nicotine on cue-induced craving for gambling in at-risk video lottery terminal gamblers who smoke.

PubMed

McGrath, Daniel S; Dorbeck, Anders; Barrett, Sean P

2013-04-01

Evidence indicates that tobacco use and gambling often co-occur. Despite this association, little is known about how tobacco use affects the propensity to gamble. Nicotine, the putative addictive component of tobacco, has been reported to potentiate the hedonic value of other nonsmoking stimuli. Environmental cues have been identified as an important contributor to relapse in addictive behavior; however, the extent to which nicotine can affect the strength of gambling cues remains unknown. This study examined whether nicotine influences subjective ratings for gambling following gambling cues. In a mixed within/between-subjects design, 30 (20 men) video lottery terminal (VLT) gamblers ('moderate-risk' or 'problem' gamblers) who smoke daily were assigned to nicotine (4 mg deliverable) or placebo lozenge conditions. Subjective and behavioral responses were assessed at baseline, following lozenge, following neutral cues, and following presentation of gambling cues. Nicotine lozenge was found to significantly reduce tobacco-related cravings (P<0.05) but did not affect gambling-related cravings, the choice to play a VLT, or other subjective responses. These results suggest that a low dose of acutely administered nicotine does not increase cue-induced craving for gambling in at-risk VLT gamblers who smoke.

Multiple Eyes for the VLT

NASA Astrophysics Data System (ADS)

2002-01-01

First System of Deployable Multi-Integral Field Units Ready Summary The ESO Very Large Telescope (VLT) at the Paranal Observatory is being equipped with many state-of-the-art astronomical instruments that will allow observations in a large number of different modes and wavebands. Soon to come is the Fibre Large Array Multi-Element Spectrograph (FLAMES) , a project co-ordinated by ESO. It incorporates several complex components, now being constructed at various research institutions in Europe and Australia. One of these, a true technological feat, is a unique system of 15 deployable fibre bundles, the so-called Integral Field Units (IFUs) . They can be accurately positioned within a sky field-of-view measuring no less that 25 arcmin in diameter, i.e., almost as large as the full Moon . Each of the IFUs looks like an insect's eye and images a small sky area (3 x 2 arcsec 2 ) with a multiple microlens. From each IFU, 20 narrow light beams are sent via optical fibres to an advanced spectrograph. All 300 spectra are recorded simultaneously by a sensitive digital camera. A major advantage of this technique is that, contrary usual spectroscopic observations in which spectral information is obtained along a (one-dimensional) line on the sky, it now allows (two-dimensional) area spectroscopy . This will permit extremely efficient spectral observations of many celestial objects, including faint galaxies, providing detailed information about their internal structure and motions. Such studies will have an important impact on our understanding, e.g., of the early evolution of galaxies , the main building blocks in the Universe. The IFUs have been developed by a team of astronomers and engineers [2] at the Observatoire de Paris-Meudon. All IFU components are now at the ESO Headquarters in Garching (Germany) where they are being checked and integrated into the instrument [3]. PR Photo 03a/02 : The GIRAFFE spectrograph in the ESO Assembly Hall (Garching, Germany) . PR Photo 03b/02 : Example of a future IFU observation in a sky field with galaxies. PR Photo 03c/02 : An illustration of how the IFUs function . PR Photo 03d/02 : The IFU design . PR Photo 03e/02 : Computer simulation of the motions in a galaxy , as deduced from IFU observations. The FLAMES instrument and its many parts ESO PR Photo 03a/02 ESO PR Photo 03a/02 [Preview - JPEG: 560 x 400 pix - 62k] [Normal - JPEG: 1120 x 800 pix - 544k] [Hi-Res - JPEG: 2885 x 2061 pix - 5.3M] Caption : PR Photo 03a/02 : The GIRAFFE spectrograph, a major component of the VLT Fibre Large Array Multi-Element Spectrograph (FLAMES) , during the present assembly at the ESO Headquarters in Garching (Germany). Late last year, the ESO Very Large Telescope (VLT) at the Paranal Observatory received its newest instrument, NAOS-CONICA . The first tests were very successful, cf. PR 25/01. But this is far from the last. Work is now underway at several European and overseas research institutes to complete the many other large astronomical instruments planned for the VLT. Over the next years, these new facilities will enter into operation one by one, further enhancing the capabilities of this true flagship of European science. One of these instruments is the Fibre Large Array Multi-Element Spectrograph (FLAMES) , to be installed at the 8.2-m VLT KUEYEN Unit Telescope. It will be able to observe the spectra of a large number of individual, faint objects (or small sky areas) simultaneously and incorporates several highly complex components, e.g., * a Nasmyth Corrector - an optical system to focus the light that is received from the telescope over a sky field of no less than 25 arcmin in diameter, i.e., almost as large as the full Moon . It was installed on KUEYEN in September 2001 * a Fibre Positioner (known as "OzPoz"). It is now being built by the AUSTRALIS Consortium, lead by the Anglo Australian Observatory (AAO) , cf. ESO PR 07/98 * a high- and intermediate-resolution optical spectrograph, GIRAFFE , with its own fibre system, developed by the Observatoire de Paris-Meudon in close collaboration with ESO . It is now in the process of being assembled in the ESO laboratories in Garching, cf. PR Photo 03a/01 . Work at the FLAMES facility will be supported by specialized data reduction software developed by Observatoire de Genève-Lausanne in collaboration with Observatoire de Paris-Meudon , and specialized observing software developed at ESO . There will also be a fibre link to the UVES high-dispersion spectrograph and there are plans for incorporating an intermediate resolution IR spectrograph in the future; the ITAL-FLAMES consortium is now preparing the associated instrument control and data reduction software packages. The Integral Field Units (IFUs) for FLAMES ESO PR Photo 03b/02 ESO PR Photo 03b/02 [Preview - JPEG: 573 x 400 pix - 94k] [Normal - JPEG: 1145 x 800 pix - 592k] ESO PR Photo 03c/02 ESO PR Photo 03c/02 [Preview - JPEG: 538 x 400 pix - 63k] [Normal - JPEG: 1076 x 800 pix - 256k] Caption : PR Photo 03b/02 : An example of observations with Integral Field Units (IFUs) at FLAMES (only 4 of the 15 units are shown here). Each IFU is placed so that it records the light from 20 small adjacent sky areas (each measuring about 3 x 2 arcsec 2 ). In this way, it is possible to register simultaneously the spectrum of as many different regions of a (distant) galaxy. PR Photo 03c/02 : How the IFUs work: each IFU consists of a microlens that guides the light from a small sky area, normally centred on a celestial object (e.g., a distant galaxy) and sends it on to the entry of the spectrograph (inside the dotted box). When it enters into operation later this year [3], GIRAFFE will become the most efficient instrument of its kind available at the world's large optical/infrared telescopes. It will be especially suited for the study of the dynamical properties of distant galaxies - their motion in space, as well as the internal motions of their stars and gas clouds. Indeed, observations of the velocity fields in a large variety of galaxies in the early Universe (when its age was only one third to one half of its current age) will be essential for a better understanding of those major building blocks of the Universe. This is first of all due to the unique system of 15 deployable fibre bundles, the Integral Field Units (IFUs) , that can be accurately positioned within a field-of-view measuring no less than 25 arcmin across, cf. PR Photo 03b/02 . Each IFU is a microscopic, state-of-the-art two-dimensional lens array with an aperture of 3 x 2 arcsec 2 on the sky. It contains twenty micro-lenses coupled with optical fibres leading the light recorded at each point in the field to the entry slit of the spectrograph, cf. PR Photo 03c/02 . A great advantage of this technique is that, contrary to usual spectroscopic observations in which spectral information is obtained along a (one-dimensional) line on the sky, it now allows (two-dimensional) area spectroscopy . It is therefore possible to obtain spectra of larger areas of a celestial object simultaneously, and not just along one particular diameter. With 15 IFUs at their disposal, the astronomers will be able to observe many galaxies at the same time - this will represent a tremendous gain of efficiency with many more astrophysical data collected within the available observation time! The IFU design ESO PR Photo 03d/02 ESO PR Photo 03d/02 [Preview - JPEG: 400 x 469 pix - 86k] [Normal - JPEG: 800 x 937 pix - 232k] Caption : PR Photo 03d/02 : Mechanical design of an IFU "button". Upper right: photo of an "IFU entrance" with the 20 square microlenses, each measuring 1.8 x 1.8 mm 2. PR Photo 03d/02 shows the mechanical design of the entrance of one IFU. An array of 20 square microlenses, each measuring 1.8 x 1.8 mm 2 is used to concentrate the light in the corresponding, small sky field onto a prism that passes the light on to 20 fibres. These are inserted and cemented into a mechanical holder and the entire assembly is then mounted in an IFU "button" that will be positioned in the focal plane by the OzPoz Positioner. A magnet is incorporated at the base of the button to ensure a stable position (a firm hold) on the focal plate during the observation. The optical cementing is ensured with an UV curing and the fibre bundle is cemented into the button with an epoxy glue in order to ensure excellent stiffness of the complete assembly. The external diameter of the button is about 6 mm, corresponding to about 11 arcsec on the sky, allowing quite close positioning of the buttons on the focal plate. An example of astronomical observations with IFUs ESO PR Photo 03e/02 ESO PR Photo 03e/02 [Preview - JPEG: 467 x 400 pix - 51k] [Normal - JPEG: 933 x 800 pix - 264k] Caption : PR Photo 03e/02 is a computer simulation of the velocity field in a galaxy , as deduced on the basis of IFU spectra. The blue area has negative velocities and is thus the approaching side of the galaxy, while the red area is receding. In this way, the direction of rotation can be determined. The velocity unit is km/s. During the astronomical observation with the IFUs , the spectrograph slit receives light from 15 sky areas simultaneously, each with 21 fibres (20 from the IFU and 1 that collects the light from the night sky in an adjacent sky field) or 22 fibres (with the addition of 1 fibre with light from a calibration lamp). Altogether, about 300 spectra are recorded simultaneously. By means of such observations, the astronomers can perform many different studies, e.g., of the dynamics of star clusters and motions of stars and interstellar clouds in galaxies. PR Photo 03e/02 provides an example of a computer simulation of a resulting diagramme in which the internal rotation of a distant spiral galaxy is clearly visible. Red and yellow areas have positive velocities that are approaching while the blue areas are receding). Of special interest will be the study of the often violent motions when two or more galaxies interact gravitationally. Notes [1]: This is a joint Press Release of ESO and the Observatoire de Paris (cf. http://www.obspm.fr/actual/nouvelle/jan02/flames.shtml ). [2]:The GIRAFFE team at the Observatoire de Paris that has developed the Integral Field Units (IFUs) discussed in this Press Release includes Jean-Pierre Aoustin, Sebastien Baratchart, Patrice Barroso, Veronique Cayatte, Laurent Chemin, Florence Cornu, Jean Cretenet, Jean-Paul Danton, Hector Flores, Francoise Gex, Fabien Guillon, Isabelle Guinouard, Francois Hammer, Jacques Hammes, David Horville, Jean-Michel Huet, Laurent Jocou, Pierre Kerlirzin, Serge Lebourg, Hugo Lenoir, Claude Lesqueren, Regis Marichal, Michel Marteaud, Thierry Melse, Fabrice Peltier, Francois Rigaud, Frederic Sayede and Pascal Vola . [3]: It is expected to ship the various components of the FLAMES instrument to the VLT Observatory at Paranal (Chile) during the next month. "First Light" is scheduled to take place some weeks thereafter, following installation at the telescope and extensive system tests. ESO will issue another Press Release with more details on that occasion.

SPLAT: Using Spectral Indices to Identify and Characterize Ultracool Stars, Brown Dwarfs and Exoplanets in Deep Surveys and as Companions to Nearby Stars

NASA Astrophysics Data System (ADS)

Aganze, Christian; Burgasser, Adam J.; Martin, Eduardo; Konopacky, Quinn; Masters, Daniel C.

2016-06-01

The majority of ultracool dwarf stars and brown dwarfs currently known were identified in wide-field red optical and infrared surveys, enabling measures of the local, typically isolated, population in a relatively shallow (<100 pc radius) volume. Constraining the properties of the wider Galactic population (scale height, radial distribution, Population II sources), and close brown dwarf and exoplanet companions to nearby stars, requires specialized instrumentation, such as high-contrast, coronagraphic spectrometers (e.g., Gemini/GPI, VLT/Sphere, Project 1640); and deep spectral surveys (e.g., HST/WFC3 parallel fields, Euclid). We present a set of quantitative methodologies to identify and robustly characterize sources for these specific populations, based on templates and tools developed as part of the SpeX Prism Library Analysis Toolkit. In particular, we define and characterize specifically-tuned sets spectral indices that optimize selection of cool dwarfs and distinguish rare populations (subdwarfs, young planetary-mass objects) based on low-resolution, limited-wavelength-coverage spectral data; and present a template-matching classification method for these instruments. We apply these techniques to HST/WFC3 parallel fields data in the WISPS and HST-3D programs, where our spectral index set allows high completeness and low contamination for searches of late M, L and T dwarfs to distances out to ~3 kpc.The material presented here is based on work supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G.

Towards a coherent view of mass loss in Betelgeuse from the photosphere to the interstellar medium

NASA Astrophysics Data System (ADS)

Montarges, Miguel; Kervella, Pierre; Perrin, Guy

2013-06-01

Massive evolved stars contribute to the chemical enrichment of the interstellar medium (ISM), the Galaxy and ultimately the Universe through their mass loss. From the photosphere to the ISM, large convective motions, low surface gravity and high brightness combine to trigger an intense stellar wind. The released material evolves chemically as the distance from the star increases, and eventually forms dust particles. The involved physical and chemical processes are central to apprehend the cosmic impact of massive evolved stars, but they are poorly understood: the surface convection remains essentially uncharacterized, as the composition of the wind, and the role of the magnetic field is unknown. Betelgeuse is the closest red supergiant and therefore it stands out as the best candidate to obtain detailed observations of the close circumstellar environment of a massive evolved star. We are currently running a high angular resolution observations program to obtain a multi-wavelength and multi-epoch characterisation of this star. Using the IOTA interferometer, Haubois et al. reconstructed an image of the photosphere of the star. Within 1 to 100 stellar radii, the VLT and VLTI allowed us to probe the compact molecular envelope of Betelgeuse (the MOLsphere) in the near-infrared, and the extended dusty envelope in the thermal infrared domain. They were recently completed with HST/STIS observations of the chromosphere in the UV, whose location is surprisingly coincident with the MOLsphere. We will present a brief review of our recent results and of our ongoing work on Betelgeuse.

New Vistas Open with MIDI at the VLT Interferometer

NASA Astrophysics Data System (ADS)

2002-12-01

"First Fringes" in Mid-Infrared Spectral Region with Two Giant Telescopes Summary Following several weeks of around-the-clock work, a team of astronomers and engineers from Germany, the Netherlands, France and ESO [2] has successfully performed the first observations with the MID-Infrared interferometric instrument (MIDI), a new, extremely powerful instrument just installed in the underground laboratory of the VLT Interferometer (VLTI) at the Paranal Observatory (Chile). In the early morning of December 15, 2002, two of the 8.2 m VLT unit telescopes (ANTU and MELIPAL) were pointed towards the southern star eta Carinae and the two light beams were directed via the complex intervening optics system towards MIDI. After a few hours of tuning and optimization, strong and stable interferometric fringes were obtained, indicating that all VLTI components - from telescopes to the new instrument - were working together perfectly. Two more stars were observed before sunrise, further proving the stability of the entire system. The first observations with MIDI mark one more important step towards full and regular operation of the VLT Interferometer [3] . They are a result of five years of determined efforts within a concerted technology project, based on a close collaboration between ESO and several European research institutes (see below). Now opening great research vistas, they also represent several "firsts" in observational astrophysics, together amounting to a real breakthrough in the field of astronomical interferometry . New views at mid-infrared wavelengths : MIDI is sensitive to light of a wavelength near 10 µm, i.e., in the mid-infrared spectral region ("thermal infrared"). This provides rich opportunities to study a wide range of otherwise inaccessible, crucial astrophysical phenomena, e.g., the formation of planets in dusty disks around newborn stars and the innermost regions around black holes. However, it is a great technical challenge to perform mid-IR observations. This is first of all because the terrestrial atmosphere, the telescopes, their mounts and, not least, the complicated optics system needed to guide the beams the long way from the telescopes to the MIDI instrument all glow bright at mid-IR wavelengths. Thus, even the most luminous mid-IR stellar sources "drown" in this bright background, calling for highly refined observational methods and data reduction procedures. Fainter objects with large telescopes : This is the first time telescopes with mirrors as large as these have been used for mid-IR interferometry. The use of the VLT giants at Paranal now allows observing much fainter objects than before. Sharper images with Interferometry : The distance between ANTU and MELIPAL during these observations, 102 metres, is a new world record for interferometry at this wavelength. The achieved angular resolution is indeed the one theoretically possible with this instrumental configuration, about 0.01 arcsec, better than what has ever been achieved before from ground or space at this wavelength. MIDI is the first of two instruments that will be placed at the focus of the VLT Interferometer. It is a collaborative project between several European research institutes: * European Southern Observatory (ESO) * Max Planck Institut für Astronomie (MPIA) (Heidelberg, Germany) * Netherlands Graduate School for Astronomy (NOVA) (Leiden, The Netherlands) * Department of Astronomy - Leiden Observatory (The Netherlands) * Kapteyn Astronomical Institute (Groningen, The Netherlands) * Astronomical Institute, Utrecht University (The Netherlands) * Netherlands Foundation for Research in Astronomy (NFRA) (Dwingeloo, The Netherlands) * Space Research Organization Netherlands (SRON) (Utrecht, Groningen; The Netherlands) * Thüringer Landessternwarte Tautenburg (TLS) (Germany) * Kiepenheuer-Institut für Sonnenphysik (KIS) (Freiburg, Germany) * Observatoire de Paris (OBSPM) (Paris, Meudon, Nancay; France) * Observatoire de la Côte d'Azur (OCA) (Nice, France) The first observations with MIDI will now be followed up by thorough tests of the new instrument before it enters into regular service. It is planned that the first community observations will be performed at the VLTI in mid-2003. Great efforts have gone into making observations with this complex science machine as user-friendly as possible and, contrary to what is normally the case in this technically demanding branch of astronomy, scientists will find interferometric work at the VLTI quite similar to that of using the many other, more conventional VLT instruments. PR Photo 30a/02: MIDI " First Fringes " of eta Carinae. PR Photo 30b/02: The happy team at the moment of "First Fringes". PR Photo 30c/02: MIDI in the Interferometric Laboratory at Paranal. PR Video Clip 03/02: Optical path scan with "First Fringes" appearing on the computer screen. A wonderful moment ESO PR Video Clip 03/02 [384x288 pix MPEG-version] ESO PR Video Clip 03/02 (480 frames/0:19 min) [MPEG; 384x288 pix; 6.6M] [RealMedia; streaming; 56kps] [RealMedia; streaming; 200kps] Another vital step has been accomplished as planned towards full operation of the ESO Very Large Telescope (VLT) and the associated VLT Interferometer (VLTI) at the Paranal Observatory in Chile, one of the world's foremost astronomical facilities. Indeed, plans had been made more than one year ago for this milestone event to take place at the end of 2002. In the early morning of December 15, 2002, at 02:45 local time (05:45 UT), a team of astronomers and engineers from Germany, Netherlands, France and ESO celebrated the first successful combination of mid-infrared "light" beams from ANTU and MELIPAL, two of the four 8.2-m VLT Unit Telescopes . This special moment, referred to as the "First Fringes" , occurred when infrared radiation at a wavelength of 8.7 µm from the bright star eta Carinae was captured simultaneously by the two telescopes (situated 102 metres apart) and then directed via a complex optics system towards the MID-Infrared interferometric instrument (MIDI), a new, extremely sensitive and versatile instrument just installed in the underground VLT Interferometric Laboratory. Strong interferometric fringes, well visible on the computer screen to the delighted team, cf. PR Photo 30a-b/02 and PR Video Clip 03/02 , were obtained repeatedly by the MIDI instrument and the recorded data were of excellent quality. A great achievement This is the first time ever interferometry in the near-infrared 8.7 µm-band (technically: the "N"-band") with large telescopes has been accomplished and the first time at 100-m baselines. For this to happen, it was necessary to keep the difference in the length of the light paths from the two telescopes to the focus of the MIDI instrument stable and equal to within a small fraction of this wavelength during the observations, in practice to about 1 µm (0.001 mm). The team spent the first few hours of the night tuning the system, positioning the many optical components and optimizing the various feed-back mechanisms that involve precision-guided mirrors below the two telescopes and the so-called "delay lines" in the underground Interferometric Tunnel [3]. After a few attempts and successive on-line optimization, modulated "fringes" - the typical signature of interferometric measurements - became visible on the screens of the instrument computers, demonstrating conclusively the validity of the overall concept, cf. PR Video Clip 03/02 . The rest of the night was used to further trim the VLTI and MIDI. The team also observed two other objects before sunrise, the young binary star Z Canis Majoris and the enigmatic Eta Carinae - for both, interferometric fringes were convincingly obtained. The perfection of all of the 32 optical elements needed to guide the starlight towards MIDI for these observations contributed to this, as did the availability of advanced user-friendly control software, specially developed for the VLTI and its instruments in order to facilitate the future observations, also by non-specialists. Advantages of MIDI With its high sensitivity to thermal radiation, MIDI is ideally suited to study cosmic material (dust and gas) near a central hot object and heated by its radiation . In the case of astronomical observations in the visible spectral region, such material is usually hidden from view because of a strong obscuring effect that is caused by the dust it contains. Most optical observations of star-forming clouds only show the dark contours of the cloud and nothing about the complex processes that happen inside. Contrarily, this obscuring effect of the dust is often entirely insignificant at the longer mid-infrared wavelengths around 10 µm (0.01 mm) at which MIDI observes, allowing direct studies of what is going on inside. MIDI science targets Thanks to interferometry and the large collecting surface of the VLT telescopes, MIDI achieves unsurpassed image sharpness (about 0.01 arcsec) and sensitivity at these "revealing" wavelengths, promising extremely detailed views, also of faint and distant objects. Clearly, the associated opportunities for exciting research are almost unlimited. Some of the first targets for the fully operational MIDI instrument will thus include the enigmatic dust rings now believed to be located around giant black holes at the centers of quasars and strong radio galaxies. Equally interesting will be in-depth studies of those disks of matter that are known to accompany the creation of new stars and from which exoplanets are forming . And with MIDI, it will now be possible to investigate the outer zones of the extended atmospheres of giant stars where the dust grains form in the first place - those complex particles that, loaded with water ice, minerals and simple organic molecules, eventually move into interstellar space and later play a crucial role in the formation of stars and planets. MIDI - a new and powerful instrument for the VLT Interferometer The MIDI instrument has been developed by a European consortium of astronomical institutes, under the leadership of the Max-Planck-Institut für Astronomie (MPIA) in Heidelberg (Germany). Following the installation in 2001 by ESO of the VLTI test instrument, VINCI, to verify and tune the exceedingly complex optical system [3], MIDI is the first of two scientific instruments that will be devoted to interferometric observations with the VLT Interferometer during the coming decade. The other is AMBER which will combine three beams from different telescopes and will be sensitive in the wavelength region of 1-2.5 µm. The MIDI instrument weighs about 1.5 tons and is mounted on a 1.5 x 2.1 m precision optical table, placed at the centre of the underground VLT Interferometric Laboratory at the top of the Paranal mountain, cf. PR Photo 30c/02 . The large cube at the back of the table is a vacuum vessel that allows cooling of the infrared detector and the surrounding optics to temperatures of -270 to -240 °C (4K to 35K on the absolute temperature scale), which is necessary for observations at these infrared wavelengths. Despite its large dimensions, MIDI has to be very carefully adjusted to the light beams arriving from the telescopes, with initial precision exceeding 0.01° (angles) and 0.1 mm (position). The electronic equipment necessary to run the instrument is installed in a separate room in order to reduce any disturbances from heat, noise and vibrations to the lowest possible level. During the observations, the astronomers operate the entire instrument, as well as the VLT Interferometer, from a building below the mountain top, more than one hundred metres away. This state-of-the-art instrument is the outcome of a close collaboration between several European research institutes [1], greatly profiting from their combined expertise in many different technological areas. This involves the construction of large astronomical instruments for infrared observations, involving operation in vacuum and at low temperatures (MPIA in Heidelberg, Germany), designing and manufacturing optics for the extreme cryogenic environment (ASTRON in Dwingeloo, The Netherlands), designing and creating the complex software needed to run the instrument in a user-friendly way (NEVEC in Leiden, The Netherlands, and MPIA), as well as other specialised contributions from the Kiepenheuer-Institut für Sonnenphysik in Freiburg (Germany), Observatoire de Paris-Meudon and Observatoire de la Côte d'Azur in Nice (France), and Thüringer Landessternwarte in Tautenburg (Germany). This wide collaboration was carried out in close cooperation with and profiting from the professional experience of ESO that has built and now operates the Paranal Observatory, ensuring the proper interfacing between MIDI and the VLTI needed for high-performance interferometric measurements. Brief history of the MIDI project Work on the mid-infraredinterferometric instrument MIDI started in 1997 when MPIA proposed to ESO to build such a facility that would conform with ESO's plans for interferometric observations with the VLT telescopes and which would most probably become the first of its kind worldwide. Soon thereafter, the Netherlands Science Organization NOVA with ASTRON and NEVEC and the other partner institutes in France, the Netherlands and Germany joined the project. With Christoph Leinert and Uwe Graser from MPIA teaming up to lead the project, more than two dozen engineers, astronomers and students worked intensively for three and a half years on the planning, design and production, before the integration of this highly complex instrument could start at the Max-Planck-Institut für Astronomie in Heidelberg. This took place in September 2001 and was followed by a period of extensive instrumental tests. Much preparatory work had to be done at Paranal in parallel, to be ready for a smooth installation of MIDI [3]. After a positive, concluding status review of MIDI by ESO in September 2002, the many parts of the complex instrument were packed into 32 big wooden boxes, with a total weight of 8 tons, and sent from Heidelberg to Paranal by air freight. The installation of MIDI in the VLT Interferometric Laboratory began as scheduled in early November. The first test measurements were carried out during the first days of December with two 40-cm siderostats, the same that were used to obtain "first fringes" with the VINCI test instrument in March 2001, cf. ESO PR 06/01. These initial measurements led to stable, good-quality fringes on the bright stars Alpha Orionis (Betelgeuse) and Omicron Ceti (Mira). The total cost of MIDI is of the order of 6 million Euros. Of this, 1.8 million Euros are for equipment, materials and optical parts, with the remaining for salaries during the extensive planning, construction and testing of this front-line instrument. Some related technical achievements Astronomical observations of electromagnetic radiation at mid-infrared wavelengths near 10 µm are difficult, because this is the spectral region of thermal radiation from our environment . If our eyes were sensitive to that radiation, everything around us would be brilliantly bright, including the sky at night, and no stars would then be visible to the naked eye. Sensitive imaging detectors for these wavelengths have become available during the past years, but to work satisfactorily, they must be cooled to a very low temperature around -265 °C (4K - 10K) during operation. Also the optics in front of the detector must be cooled to about -240 °C - otherwise all images would be immediately overexposed, due to the added thermal radiation from those lenses and mirrors. In practice, the technical solution to this fundamental problem is a so-called closed-cycle cooler that works with high-pressure helium gas and achieves the required low temperatures on several "cold fingers" inside the instrument. However, the associated moving pistons cause vibrations which must be reduced to a minimum by means of special damping materials and connections for the cooler and the instrument. Otherwise this motion would be detrimental to the sensitive measurements, which require near-perfect mechanical stability, to within a fraction of the infrared wavelength, i.e., to 0.001 mm (1 µm) or better. Similarly, slight bending effects of the instrument parts during cool-down from room temperature would also compromise the measurements. This has been avoided by manufacturing the support of all optical parts near the detector from one single, carefully selected block of special aluminium. Still, as the light from the star being observed falls on the detector inside MIDI, it will be surrounded by strong thermal radiation from the terrestrial atmosphere in this direction and all uncooled ("warm") mirrors in the light path. The transfer of the digitally recorded images from the detector to the computer data storage must therefore occur at very high speed, one image per 0.001 sec, and always be strictly synchronized with a modulation inherent in the measurement process. This requires powerful, highly specialized and yet flexible electronics - this crucial part of the new instrument was developed over the past years at MPIA. With this and many other technical innovations successfully completed, and with the first on-the-sky observations just accomplished to the full satisfaction of the MIDI team, this new, powerful instrument will soon be ready to enter into new and unknown research territory. Hundreds of astronomers in the ESO members countries and their colleagues all over the world are now eagerly waiting to get their hands on this new facility.

Zinc abundances in Galactic bulge field red giants: Implications for damped Lyman-α systems

NASA Astrophysics Data System (ADS)

Barbuy, B.; Friaça, A. C. S.; da Silveira, C. R.; Hill, V.; Zoccali, M.; Minniti, D.; Renzini, A.; Ortolani, S.; Gómez, A.

2015-08-01

Context. Zinc in stars is an important reference element because it is a proxy to Fe in studies of damped Lyman-α systems (DLAs), permitting a comparison of chemical evolution histories of bulge stellar populations and DLAs. In terms of nucleosynthesis, it behaves as an alpha element because it is enhanced in metal-poor stars. Abundance studies in different stellar populations can give hints to the Zn production in different sites. Aims: The aim of this work is to derive the iron-peak element Zn abundances in 56 bulge giants from high resolution spectra. These results are compared with data from other bulge samples, as well as from disk and halo stars, and damped Lyman-α systems, in order to better understand the chemical evolution in these environments. Methods: High-resolution spectra were obtained using FLAMES+UVES on the Very Large Telescope. We computed the Zn abundances using the Zn i lines at 4810.53 and 6362.34 Å. We considered the strong depression in the continuum of the Zn i 6362.34 Å line, which is caused by the wings of the Ca i 6361.79 Å line suffering from autoionization. CN lines blending the Zn i 6362.34 Å line are also included in the calculations. Results: We find [Zn/Fe] = +0.24 ± 0.02 in the range -1.3 < [Fe/H] < -0.5 and [Zn/Fe] = + 0.06 ± 0.02 in the range -0.5 < [Fe/H] < -0.1, whereas for [Fe/H] ≥ -0.1, it shows a spread of -0.60 < [Zn/Fe] < + 0.15, with most of these stars having low [Zn/Fe] < 0.0. These low zinc abundances at the high metallicity end of the bulge define a decreasing trend in [Zn/Fe] with increasing metallicities. A comparison with Zn abundances in DLA systems is presented, where a dust-depletion correction was applied for both Zn and Fe. When we take these corrections into account, the [Zn/Fe] vs. [Fe/H] of the DLAs fall in the same region as the thick disk and bulge stars. Finally, we present a chemical evolution model of Zn enrichment in massive spheroids, representing a typical classical bulge evolution. Observations collected both at the European Southern Observatory, Paranal, Chile (ESO programmes 71.B-0617A, 73.B0074A, and GTO 71.B-0196).Table 6 is available in electronic form at http://www.aanda.org

Probing individual star-forming regions in maximal starburst galaxiesat redshifts z=2-4 with the SMA (and other major facilities): Planck's Dusty GEMS.

NASA Astrophysics Data System (ADS)

Nesvadba, Nicole

2018-01-01

Strongly gravitationally lensed galaxies are veritable gems for our understanding of high-redshift galaxy evolution, allowing us to study dust, gas, and star formation even in the most intense starbursts on scales of individual star-forming regions. On these scales, below one to few 100 pc in the source plane, kpc-scale rotational support no longer dominates, and star formation is regulated by the local gas and stellar mass surface densities and energy injection from turbulence and winds driven by star formation and AGN. I will report on our on-going follow-up of Planck's Dusty GEMS, a small sample of 11 of the brightest, gravitationally lensed high-redshift galaxies on the extragalactic sub-mm sky. SMA 850-micron imaging is playing a critical role in identifying and characterizing the dusty starburst regions, their star-formation properties, and the gravitational lens modeling, and has been paving the way towards a rich multi-wavelength program, which would not have been possible without. This includes VLT, HST and ALMA high-resolution studies of the gas and stellar populations, amongst others. These observations enabled us, e.g., to study theinterplay between gravity and turbulence in an Eddington-limited starburst for the first time, and to detect the first absorption line of [CII] from diffuse gas outside the Milky Way. I will also discussthe first direct lensing estimate of a (bottom-heavy) initial mass function in the early Universe and outline how these and similar observations would benefit from increased bandwidth.

Four-Wavelength Lidar Evaluation of Particle Characteristics and Aerosol Densities

DTIC Science & Technology

1985-06-01

34 Cure2: 11.4% with/witlhot 0.0 OAS Own 3: 25.9% PONameter .0s _ uve :1 %omu-lmlto x -, 0 2 0.01 Tagt 199% ---- Target solution Curve 1: 11.8% Bt-fit...propagation paths. 2. (U) MULTUVELZNGTI LMIAR SYSTIM (U) The multiwavelength lidar systmn is installed within a 6-meter long van to facilitate opera- ti"ms...the, lidar receivers fog application to the Smoke Week VI/SNOW-TWO exparimenta. New extended-range logarithmic amlif jets were ýý -& led on thfý 0.53

Software engineering for ESO's VLT project

NASA Astrophysics Data System (ADS)

Filippi, G.

1994-12-01

This paper reports on the experience at the European Southern Observatory on the application of software engineering techniques to a 200 man-year control software project for the Very Large Telescope (VLT). This shall provide astronomers, before the end of the century, with one of the most powerful telescopes in the world. From the definition of the general model, described in the software management plan, specific activities have been and will be defined: standards for documents and for code development, design approach using a CASE tool, the process of reviewing both documentation and code, quality assurance, test strategy, etc. The initial choices, the current implementation and the future planned activities are presented and, where feedback is already available, pros and cons are discussed.

Particle accelerators in the hot spots of radio galaxy 3C 445, imaged with the VLT.

PubMed

Prieto, M Almudena; Brunetti, Gianfranco; Mack, Karl-Heinz

2002-10-04

Hot spots (HSs) are regions of enhanced radio emission produced by supersonic jets at the tip of the radio lobes of powerful radio sources. Obtained with the Very Large Telescope (VLT), images of the HSs in the radio galaxy 3C 445 show bright knots embedded in diffuse optical emission distributed along the post-shock region created by the impact of the jet into the intergalactic medium. The observations reported here confirm that relativistic electrons are accelerated by Fermi-I acceleration processes in HSs. Furthermore, both the diffuse emission tracing the rims of the front shock and the multiple knots demonstrate the presence of additional continuous re-acceleration processes of electrons (Fermi-II).

A Glimpse of the Young Milky Way

NASA Astrophysics Data System (ADS)

2002-10-01

VLT UVES Observes Most Metal-Deficient Star Known [1] Summary A faint star in the southern Milky Way, designated HE 0107-5240 , has been found to consist virtually only of hydrogen and helium . It has the lowest abundance of heavier elements ever observed , only 1/200,000 of that of the Sun - 20 times less than the previous record-holding star. This is the result of a major ongoing research project by an international team of astronomers [2]. It is based on a decade-long survey of the southern sky, with detailed follow-up observations by means of the powerful UV-Visual Echelle Spectrograph (UVES) on the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory in Chile. This significant discovery now opens a new window towards the early times when the Milky Way galaxy was young, possibly still in the stage of formation. It proves that, contrary to most current theories, comparatively light stars like HE 0107-5240 (with 80% of the mass of the Sun) may form in environments (nearly) devoid of heavier elements. Since some years, astronomers have been desperately searching for stars of the very first stellar generation in the Milky Way, consisting only of hydrogen and helium from the Big Bang. None have been detected so far and doubts have arisen that they exist at all. The present discovery provides new hope that it will ultimately be possible to find such stellar relics from the young Universe and thereby to study "unpolluted" Big Bang material. PR Photo 25a/02 : The sky region around the very metal-deficient star HE 0107-5240 . PR Photo 25b/02 : Comparison of UVES spectra of stars with different metal abundances. Stellar generations in the Milky Way galaxy The Milky Way galaxy in which we live formed from a gigantic cloud of gas, when the Universe was still young, soon after the initial Big Bang. At the beginning, this gas was presumably composed almost exclusively of hydrogen and helium atoms produced during the Big Bang. However, once the first stars formed by contraction in that gas, many heavier elements were built up by nuclear processes in their interiors. As time passed, many of the stars of this and following stellar generations returned the processed matter to their surroundings at the ends of their lives, either during violent supernova explosions or via strong "stellar winds". In this way, the interstellar gas in the Milky Way system has ever since been continuously enriched with heavier elements. Stars of later generations like our Sun now contain those elements produced by their ancestors and we are indeed ourselves made up of them. Consequently, the early (and hence, old) stars in the Milky Way mainly differ from younger stars by containing very small amounts of such elements . Hunting the earliest stars Have some of those earliest stars survived to our days? In theory, at least, it would be possible that some of the lighter ones - having the longest lifetimes - are still around. But if so, where are they? During the past three decades, astronomers have desperately tried to find bona-fide representatives of the very first stellar generation(s) in the Milky Way, i.e. stars with no or, at most, extremely low abundance of elements other than hydrogen and helium. The researchers usually refer to such objects as Population III stars , the other two populations being stars with heavy-element abundances like the Sun (Population I) or somewhat less (Population II) [3]. The Hamburg/ESO survey Now, a group of astronomers from Germany, Sweden, Australia, Brazil and the USA [2] has found a giant star that has a concentration of heavy elements 200,000 times lower than the Sun, or about 20 times less than the previous "record" for this kind of star. It thus provides the researchers with a unique window towards the early stages of the formation of the Milky Way and a fine opportunity to study stellar gas with a composition close to that produced during the Big Bang. This is one important outcome of a systematic search for the most metal-deficient stars that is currently being carried out at Hamburger Sternwarte [4]. Over a period of more than 10 years, a large collection of photographic pictures of the southern sky were obtained with the ESO 1-m Schmidt Telescope, a wide-angle telescope at the La Silla observatory in Chile that has now been decommissioned. Thanks to a large glass prism in the front of the telescope, every object in the observed sky field - stars as well as galaxies - was imaged as a small spectrum, providing a first rough idea about its type and composition. The main aim of this "Hamburg/ESO survey" (with Dieter Reimers , Associate Director of the Hamburger Sternwarte, as Principal Investigator and Lutz Wisotzki , now at Astrophysikalisches Institut Potsdam, Germany, as Project Scientist) was to find quasars (particularly active centres of galaxies), a task that was accomplished most successfully, cf. e.g., ESO PR 10/97 and ESO PR 08/00 (Report F). A very welcome by-product of this survey has been a rich harvest of very metal-poor stars . This part of the project is led by Norbert Christlieb , also from the Hamburg Observatory, and now on sabbatical leave at the Research School of Astronomy and Astrophysics of the Australian National University (Canberra, Australia). Using fast computers and advanced pattern-recognition software to analyze the photographic exposures and thus to sift through millions of registered stellar spectra, about 8000 candidates for very metal-poor stars were found. These stars are now being scrutinized spectroscopically one-by-one with many medium-sized telescopes all over the world. Confirmed candidates are then observed with the largest telescopes in the world in order to obtain very detailed spectra (of high spectral resolution), which allow the astronomers to determine their chemical composition accurately. The very metal-deficient star HE 0107-5240 ESO PR Photo 25a/02 ESO PR Photo 25a/02 [Preview - JPEG: 400 x 458 pix - 86k [Normal - JPEG: 800 x 915 pix - 648k] ESO PR Photo 25b/02 ESO PR Photo 25b/02 [Preview - JPEG: 494 x 400 pix - 55k [Normal - JPEG: 987 x 800 pix - 216k] Caption : PR Photo 25a/02 shows a small sky field with the very metal-deficient star HE 0107-5240 at the centre (reproduced from the Digital Sky Survey [STScI Digitized Sky Survey, (C) 1993, 1994, AURA, Inc. all rights reserved - cf. http://archive.eso.org/dss/dss]). PR Photo 25b/02 displays a comparison of a region of the spectrum of the Sun (top) with that of CD -38 245 , the previously most iron-deficient star known (2nd from top), the new record-holder HE 0107-5240 (3rd from top), and a (hypothetical) Population III star [4], consisting only of elements produced in the Big Bang, i.e. hydrogen and helium, and traces of lithium. As can be seen, the spectral absorption lines become progressively weaker with decreasing content of heavier elements. While there is 1 iron atom for every 31,000 hydrogen atoms in the atmosphere of the Sun, in HE 0107-5240 this ratio is about 200,000 times smaller, or only 1 iron atom for every 6.8 billion hydrogen atoms! The two spectra in the middle show that HE 0107-5240 is indeed much more metal-poor than the previous record-holder CD -38 245 - the iron (Fe) lines in the spectrum of HE 0107-5240 are weaker (or absent) and the Nickel (Ni) line is not visible at all. One of these stars has been designated HE 0107-5240 ("HE" stands for Hamburg/ESO Survey, and the number denotes the approximate position of the star on the sky). It is about ten thousand times fainter than the faintest stars that can be seen with the unaided eye. It is located in the direction of the southern constellation Phoenix, at a distance of about 36,000 light-years. This star was observed in December 2001 with the UV-Visual Echelle Spectrograph (UVES) on the 8.2-m VLT KUEYEN telescope at the ESO Paranal Observatory (Chile). From these spectra, Norbert Christlieb and his colleagues at the Dept. of Astronomy and Space Physics, University of Uppsala (Sweden) and at the Munich University Observatory (Germany) were able to determine the chemical composition of the star. The implications HE 0107-5240 turns out to be the most metal-poor star known to date . " This is, in a way, the closest we have ever come to the conditions directly after the Big Bang by studying stars ", says Norbert Christlieb . " But obviously, a lot must have happened between the Big Bang and the formation of this star. In spite of its extreme metal-poorness, it evidently contains some metals, and they were most probably formed in a even earlier, massive star that exploded as a supernova ". Bengt Gustafsson from the University of Uppsala, who lead the chemical analysis jointly with Christlieb, adds that " this star also has an abnormally large content of carbon and nitrogen. Those elements may possibly have been formed by nuclear reactions with helium and hydrogen deep inside the star and subsequently transported upwards to the stellar surface where they can now be observed. It is also possible that a neigbouring star at the end of its life 'polluted' our star by transferring some of its enriched material to HE 0107-5240 at that moment. The ongoing observations with UVES will help us to decide which scenario is the most probable ." Renewed hope to find first-generation stars The mass of HE 0107-5240 is about 80% of that of the Sun. This discovery thus clearly demonstrates that stars with masses slightly less than the Sun can form from very metal-poor gas. This is unexpected, as most current theoretical calculations indicate that it is very difficult to form low-mass stars shortly after the Big Bang, because metals are needed to efficiently cool gas clouds as they contract into stars. But now HE 0107-5240 reveals that Nature has found a way to achieve the necessary cooling. It therefore appears that many of the model calculations must be refined. Equally important: if a star like HE 0107-5240 , with about 0.8 solar mass and 1/200,000 of the metal content of the Sun, did indeed form in the early Universe, then it should also have been possible for low-mass Population III stars to form . If so, they would have survived until today. This implies that there is new hope to find them by means of large, systematic searches like the Hamburg/ESO Survey. Until now, follow-up spectroscopic observations - which are necessarily quite time-consuming - have only been made of about one-quarter of the 8000 low-metal-abundance candidate stars identified in that survey. It is therefore not excluded that a bona-fide Population III star may eventually be found in the course of this programme. More information The information presented in this Press Release is based on a research article ("A stellar relic from the early Milky Way" by Norbert Christlieb et al.) that appears in the research journal "Nature" on October 31, 2002. Notes [1]: This press release is issued in coordination between ESO and Hamburger Sternwarte in Germany. [2]: The team consists of Norbert Christlieb (Hamburger Sternwarte, University of Hamburg, Germany; on sabbatical leave at the Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Australia), Michael S. Bessell (Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Australia), Timothy C. Beers (Department of Physics and Astronomy, Michigan State University, East Lansing, USA), Bengt Gustafsson, Paul S. Barklem, Torgny Karlsson, Michelle Mizuno-Wiedner (Department of Astronomy and Space Physics, University of Uppsala, Sweden), Andreas Korn (University Observatory Munich, Germany) and Silvia Rossi (Instituto de Astronomia, Geofísica e Ciencias Atmosféricas, Universidade de São Paulo, Brazil). [3]: Most stars in the Milky Way galaxy move within the disk, and for most of these, 1 to 2 percent of their mass consists of chemical elements that are heavier than hydrogen and helium; this is also the case for the Sun, which at 4.6 billion years is about one third of the age of our galaxy. There exists, however, another population of stars for which the heavy-element abundance is only 1/10 - 1/1000 of that of the Sun. Those stars are found in globular clusters, but most move in a huge swarm around the disk, in the halo of the Galaxy. These "halo stars" were born when the Milky Way galaxy was young and their motions still carry the imprint of the process by which our galaxy formed, when gravity brought the gas together and the first stars appeared. The "halo stars" are said to belong to "Population II", in contrast to the younger stars in the disk (like the Sun) that are referred to as "Population I" stars. But what is then the origin of the small amount of heavy elements in Population II stars? There must have been supernovae and other exploding stars in the very early (or even pre-) Milky Way gas, out of which Population II stars were formed. This first (still hypothetical) stellar generation has been named "Population III". There have been many attempts to find Population III stars, which are then presumably totally void of metals, but those searches have not succeeded so far. [4]: Astronomers refer to elements heavier than hydrogen and helium as "metals". Stars with a low abundance of heavier elements are thus referred to as "metal-poor" stars .

Lots of Small Stars Born in Starburst Region

NASA Astrophysics Data System (ADS)

1999-10-01

Decisive Study of NGC 3603 with the VLT and ISAAC An international group of astronomers [1] has used the ESO Very Large Telescope (VLT) at Paranal (Chile) to perform unique observations of an interstellar nebula in which stars are currently being born. Thanks to the excellent imaging properties of the first of the four 8.2-m VLT Unit Telescopes, ANTU, they were able to demonstrate, for the first time, the presence of large numbers of small and relatively light, new-born stars in NGC 3603, a well-known "starburst" region in the Milky Way Galaxy . Until now, it has only been possible to observe brighter and much heavier stars in such nebulae. The new observations show that stars of all masses are being born together in the same starburst event, a fundamental result for our understanding of the very complex process of star formation. Background of the project The present research programme was granted observing time with VLT ANTU in April 1999. Its general aim is to investigate collective, massive star formation, in particular the coalescence of high- and low-mass stars in the violent environments of starburst regions . These are areas in which the processes that lead to the birth of new stars are particularly active just now. Several fundamental questions arise in this context. A very basic one is whether low-mass stars form at all in such environments. And if so, do they form together with the most massive stars in a starburst event or do they form at different times, before or after or perhaps on different timescales? Are low-mass stars born with any "preferred" mass that may possibly give further clues to the ongoing processes? All of this is most important in order to understand the detailed mechanisms of star formation. Most current theoretical scenarios explain how single stars form in an isolated, contracting gas cloud, but most stars in the Universe did not form in that simple way. Once some massive stars have formed in some place and start to shine, they will quickly affect their environment, but how much? At this moment, nobody knows for sure what determines the actual masses of individual stars that are formed in a very massive and turbulent gas cloud, although some ideas can now be tested with these new observations. The NGC 3603 region The new VLT observations are the key part of a larger research programme that also includes observations of the stellar cluster in the famous Tarantula Nebula in the Large Magellanic Cloud (LMC) with the NICMOS instrument on the Hubble Space Telescope (HST), as well as adaptive optics observations with ground-based telescopes of more quiescent, star-forming regions in the Galaxy. However, the team considered the starburst region NGC 3603 as the best target for this kind of investigation. It is situated in the far southern constellation Carina (The Keel) and can only be observed from the South. Moreover, such a study has to focus on the densest part of the cluster that can only be resolved with a very sensitive infrared (IR) instrument under the best seeing conditions. The VLT ANTU telescope and the multi-mode ISAAC facility are ideally suited for this purpose. NGC 3603 is located in the Carina spiral arm in the Milky Way galaxy at a distance of about 20,000 light-years (6 - 7 kpc). It is the only massive, galactic "HII-region" (so denoted by astronomers because part of its hydrogen is ionized) in which a central cluster of strongly UV-radiating stars of types "O" and "B" that ionize the nebula can be studied at visual and near-infrared wavelengths. This is because the line-of-sight is reasonably free of dust in this direction; the dimming in near-infrared radiation due to intervening matter between the nebula and us is only about a factor of 2 (contrary to 80 in visible light). The total mass of the hot O- and B-stars in NGC 3603 is over 2000 solar masses. Together, the more than fifty heavy and bright O-stars in NGC 3603 have about 100 times the ionizing power of the well-known Trapezium cluster in the Orion Nebula . In fact, the star cluster in NGC 3603 is in many respects very similar to the core of the large, ionizing cluster in the approx. eight times more distant Tarantula Nebula in the LMC. The new VLT observations ESO PR Photo 38a/99 ESO PR Photo 38a/99 [Preview - JPEG: 400 x 447 pix - 296k] [Normal - JPEG: 800 x 894 pix - 956k] [Full-Res - JPEG: 1366 x 1526 pix - 1.7M] ESO PR Photo 38b/99 ESO PR Photo 38b/99 [Preview - JPEG: 400 x 448 pix - 200k] [Full-Res - JPEG: 516 x 578 pix - 238k] Caption : ESO PR Photo 38a/99 is a composite "false-colour" infrared image of the starburst region NGC 3603 that is composed from three exposures obtained with the multi-mode ISAAC instrument at the Nasmyth focus of the first 8.2-m VLT Unit Telescope (ANTU) in April 1999. Three near-infrared filters were used, J s (wavelength 1.24 µm; here reproduced in blue), H (1.65 µm; green) and K s (2.17 µm; red). The intensities are scaled in logarithmic units and the field measures 3.4 x 3.4 arcmin 2 , or about 20 x 20 light-years 2 at the distance of the nebula. North is up; East to the left. The central cluster is the densest concentration of massive stars known in the Milky Way (this area is enlarged in ESO PR Photo 38b/99 ; the field shown is about 2.5 x 2.5 light-years 2 ). It hosts more than 50 hot O-type stars. The brightest star in the field is the red supergiant IRS4 ; it is located about 80 arcsec NE of the center. About 18 arcsec N of the center are the ring nebula and the bipolar outflows around the blue supergiant Sher25 . The photo also shows three proplyd-like objects [2] that have been recently discovered; they are similar to those seen in Orion Nebula, but 20-30 times more extended. About 1 arcmin SSE of the central cluster are seen the brightest members of the deeply embedded proto cluster IRS9 . The nebulosities to the South and West of the center appear to be red because of strong emission in the Bracket-gamma spectral line from hydrogen atoms at 2.166 µm. Images of the NGC 3603 region were obtained in three near-IR filter bands (J s , H and K s ) with the ISAAC instrument at the ANTU telescope. The observations were made in "service" mode on April 4 - 6 and 9, 1999, during selected periods when the (optical) seeing was equal to or better than 0.4 arcsec. This was a most essential requirement in order to achieve sufficient angular resolution (image sharpness) that would allow to do accurate photometric measurements of individual stars in this crowded cluster . This particular observing mode, during which ESO observers at ANTU kept careful track of the actual atmospheric conditions, contributed greatly to securing the very high quality images needed for this programme. In view of the many comparatively bright stars in the field, the observing strategy was to use the shortest possible exposure time (1.77 sec) to keep the number of over-exposed (saturated) stellar images to a minimum. As the minimum time required to stabilize the telescope's active optics control system and guarantee the optimum optical quality was about 1 min, thirty-four short exposures were made at each sky position and then co-added to an effective one-minute exposure. After each such series, the telescope pointing was offset in a random pattern up to 20 arcsec from the center; this enlarged the imaged sky area somewhat and facilitated the subtraction of the infrared emission from the sky background. The individual 1-min exposures were then very carefully co-aligned to obtain the highest possible spatial resolution and co-added. The resulting images cover a sky field of 3.4 x 3.4 arcmin 2 with a pixel size of 0.074 arcsec. The effective exposure times of the final broad-band images in the central 2.5 x 2.5 arcmin 2 area are 37, 45, and 48 min in the J s , H and K s filters, respectively. The final step involved the computer-aided detection of the individual stars in the frames, the measurement of their brightness as seen in the different wavebands and hence their infrared colours. About 20,000 intensity peaks were detected in each waveband at the same pixel location. However, after the rejection of very faint and spurious images and recording only objects that were detected independently in all three wavebands within the same pixel, the resulting list of measured stellar images was reduced to 6967 objects, still a substantial number, though. The brightness and colours of a star are an indication of its mass and age. By comparing the measured brightness and colours with computer simulations, the astronomers were therefore able to deduce the numbers of stars with different ages and masses in NGC 3603 . Detecting the low-mass stars in NGC 3603 The new VLT observations are the most sensitive ones made to date of this densely packed starburst region. They allowed the team to investigate in unprecedented detail the low-mass stellar population in this area. Although the low-mass stars in NGC 3603 are not exceedingly faint - they are in fact about 3 magnitudes brighter than ISAAC's detection limit - it is extremely difficult to detect them and to measure their brightness accurately because of the enormous range of brightnesses (more than a factor of 10,000) among the densely crowded stars in the inner region of the cluster. Unless high angular resolution, high optical stability and high overall sensitivity is achieved, the fainter images of the low-mass stars will "drown" in the light of the adjacent, much brighter stars. Only a powerful telescope/instrument combination like ANTU/ISAAC can successfully perform such a critical observation. The sensitivity limit obtained - set by the requirement that a star must be detected in all three infrared wavebands - corresponds to about one-tenth of a solar mass for young stars (in the astronomical sense) aged only 700,000 years, and still in the initial contraction phase. Thus, for the first time, it was possible to reach the necessary angular resolution and sensitivity to study a starburst region on a star-by-star basis down to this low mass limit. For comparison, the most sensitive observations of the more distant Tarantula Nebula only reach down to a limit of about 1 solar mass. A most important conclusion of this study is that there are lots of sub-solar mass stars in NGC 3603 , i.e., contrary to several theoretical predictions, these low-mass stars do form in violent starbursts ! The overall age of stars in the contraction phase that are located in the innermost region of NGC 3603 was found to be 300,000 - 1,000,000 years. The counts clearly show that this cluster is well populated in sub-solar mass stars. The next steps The team describes these new results in a scientific article ( "Low-mass stars in the massive HII region NGC 3603 - Deep NIR imaging with ANTU/ISAAC") that will appear in the European research journal Astronomy & Astrophysics in December 1999. Further information about related work on NGC 3603 is available at a dedicated webpage. The present VLT data will now be used for continued studies during which the limits of detection and measurement will be further pushed by means of advanced image processing and analysis. It will also be interesting to look further into possible variations of the number of stars with a given mass over the observed field, not least, to compare the new results with other ongoing studies of different regions (although less massive), e.g. with the Hubble Space Telescope and its infrared instrument NICMOS or with ground-based Adaptive Optics instruments. Notes [1] The team consists of Bernhard Brandl (Principal Investigator; Cornell University, Ithaca, New York, USA), Wolfgang Brandner (University of Hawaii, Honolulu, USA), Frank Eisenhauer (Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany), Anthony F.J. Moffat (Université de Montreal, Canada), Francesco Palla (Osservatorio Astrofisico di Arcetri, Florence, Italy) and Hans Zinnecker (Astrophysikalisches Institut Potsdam, Germany). [2] Proplyd is an astronomical term that stands for "proto-planetary disk", i.e. disks around young stars in which planets may later form. However, although they look like the proplyds found in the Orion Nebula, the "proplyd-like" objects in NGC 3603 are not likely to develop into planets. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org../ ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Quantifying photometric observing conditions on Paranal using an IR camera

NASA Astrophysics Data System (ADS)

Kerber, Florian; Querel, Richard R.; Hanuschik, Reinhard

2014-08-01

A Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics GmbH (RPG), is used to monitor sky conditions over ESO's Paranal observatory in support of VLT science operations. In addition to measuring precipitable water vapour (PWV) the instrument also contains an IR camera measuring sky brightness temperature at 10.5 μm. Due to its extended operating range down to -100 °C it is capable of detecting very cold and very thin, even sub-visual, cirrus clouds. We present a set of instrument flux calibration values as compared with a detrended fluctuation analysis (DFA) of the IR camera zenith-looking sky brightness data measured above Paranal taken over the past two years. We show that it is possible to quantify photometric observing conditions and that the method is highly sensitive to the presence of even very thin clouds but robust against variations of sky brightness caused by effects other than clouds such as variations of precipitable water vapour. Hence it can be used to determine photometric conditions for science operations. About 60 % of nights are free of clouds on Paranal. More work will be required to classify the clouds using this technique. For the future this approach might become part of VLT science operations for evaluating nightly sky conditions.

THE GJ1214 SUPER-EARTH SYSTEM: STELLAR VARIABILITY, NEW TRANSITS, AND A SEARCH FOR ADDITIONAL PLANETS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berta, Zachory K.; Charbonneau, David; Bean, Jacob

2011-07-20

The super-Earth GJ1214b transits a nearby M dwarf that exhibits a 1% intrinsic variability in the near-infrared. Here, we analyze new observations to refine the physical properties of both the star and planet. We present three years of out-of-transit photometric monitoring of the stellar host GJ1214 from the MEarth Observatory and find the rotation period to be long, most likely an integer multiple of 53 days, suggesting low levels of magnetic activity and an old age for the system. We show that such variability will not pose significant problems to ongoing studies of the planet's atmosphere with transmission spectroscopy. Wemore » analyze two high-precision transit light curves from ESO's Very Large Telescope (VLT) along with seven others from the MEarth and Fred Lawrence Whipple Observatory 1.2 m telescopes, finding physical parameters for the planet that are consistent with previous work. The VLT light curves show tentative evidence for spot occultations during transit. Using two years of MEarth light curves, we place limits on additional transiting planets around GJ1214 with periods out to the habitable zone of the system. We also improve upon the previous photographic V-band estimate for the star, finding V = 14.71 {+-} 0.03.« less

Construction of conjugative gene transfer system between E. coli and moderately thermophilic, extremely acidophilic Acidithiobacillus caldus MTH-04.

PubMed

Liu, Xiangmei; Lin, Jianqun; Zhang, Zheng; Bian, Jiang; Zhao, Qing; Liu, Ying; Lin, Jianqiang; Yan, Wangming

2007-01-01

A genetic transfer system for introducing foreign genes to biomining microorganisms is urgently needed. Thus, a conjugative gene transfer system was investigated for a moderately thermophilic, extremely acidophilic biomining bacterium, Acidithiobacillus caldus MTH-04. The broad-host-range IncP plasmids RP4 and R68.45 were transferred directly into A. caldus MTH-04 from Escherichia coli by conjugation at relatively high frequencies. Additionally the broad-host-range IncQ plasmids pJRD215, pVLT33, and pVLT35 were also transferred into A. caldus MTH-04 with the help of plasmid RP4 or strains with plasmid RP4 integrated into their chromosome, such as E. coli SM10. The Km(r) and Sm(r) selectable markers from these plasmids were successfully expressed in A. caldus MTH-04. Futhermore, the IncP and IncQ plasmids were transferred back into E. coli cells from A. caldus MTH-04, thereby confirming the initial transfer of these plasmids from E. coli to A. caldus MTH-04. All the IncP and IncQ plasmids studied were stable in A. caldus MTH-04. Consequently, this development of a conjugational system for A. caldus MTH-04 will greatly facilitate its genetic study.

The discovery of the peculiar L dwarf ULAS J222711-004547

NASA Astrophysics Data System (ADS)

Marocco, F.; Day-Jones, A. C.; Jones, H. R. A.; Pinfield, D. J.; Burningham, B.; Zhang, Z. H.

We present the discovery of a very peculiar L dwarf from the UKIDSS Large Area Survey (LAS), ULAS J222711-004547. Its very red infrared colours (MKO J-K = 2.79) make it the reddest brown dwarf discovered so far. The object was discovered as part of a large spectroscopic campaign aimed at constraining the sub-stellar birth rate. We obtained a moderate resolution spectrum of this target using the echelle spectrograph XSHOOTER on VLT/UT2, and classified it as L7pec, confirming its very red nature. We show that applying a simple de-reddening curve to the spectrum of ULAS J222711-004547, this becomes very similar to the spectrum of a L7 spectroscopic standard. Therefore we conclude that the reddening of the spectrum is mostly due to an excess of dust in the photosphere of the object. This new discovery joins the list of unusually red L dwarfs, whose nature is not yet fully understood, and poses a new important challenge to atmospheric modeling of substellar objects.

Astrometry with the VLT Interferometer

NASA Astrophysics Data System (ADS)

Quirrenbach, Andreas

The VLTI was originally conceived as an imaging instrument, providing a resolution of a few milliarcseconds at near-infrared wavelengths for studies of stars, circumstellar matter, and extragalactic objects. However, following the pioneering work on interferometric narrow-angle astrometry by Shao and Colavita (1992) and Colavita (1994), it was proposed that the VLTI could also be used for astrometric planet detection (Quirrenbach 1995). It was envisaged that the astrometric mode of the VLTI could be implemented by taking advantage of the large unvignetted field-of-view foreseen at that time (von der Lühe, Quirrenbach, & Koehler 1995). The idea of using the VLTI for narrowangle astrometry was embraced by ESO's Interferometry Science Advisory Committee (Paresce et al. 1996), but the technical concept for the delay lines has changed. The current plan for narrow-angle astrometry is based on dual star feeds at the telescopes and comprehensive internal laser metrology, as described in the PRIMA (Phase-Referenced Imaging and Microarcsecond Astrometry) study (Quirrenbach et al. 1998).

Detailed abundance analysis of globular clusters in the Local Group. NGC 147, NGC 6822, and Messier 33

NASA Astrophysics Data System (ADS)

Larsen, S. S.; Brodie, J. P.; Wasserman, A.; Strader, J.

2018-06-01

Context. Globular clusters (GCs) are emerging as powerful tracers of the chemical composition of extragalactic stellar populations. Aims: We present new abundance measurements for 11 GCs in the Local Group galaxies NGC 147, NGC 6822, and Messier 33. These are combined with previously published observations of four GCs in the Fornax and Wolf-Lundmark-Melotte (WLM) galaxies. Methods: The abundances were determined from analyses of integrated-light spectra obtained with the HIRES spectrograph on the Keck I telescope and with UVES on the Very Large Telescope (VLT). We used our analysis technique that was developed for this purpose and tested on Milky Way GCs. Results: We find that the clusters with [Fe/H] < -1.5 are all α-enhanced at about the same level as Milky Way GCs. Their Na abundances are also generally enhanced relative to Milky Way halo stars, suggesting that these extragalactic GCs resemble their Milky Way counterparts in containing large numbers of Na-rich stars. For [Fe/H] > -1.5, the GCs in M33 are also α-enhanced, while the GCs that belong to dwarfs (NGC 6822 SC7 and Fornax 4) have closer to solar-scaled α-element abundances. The abundance patterns in SC7 are remarkably similar to those in the Galactic GC Ruprecht 106, including significantly subsolar [Na/Fe] and [Ni/Fe] ratios. In NGC 147, the GCs with [Fe/H] < -2.0 account for about 6% of the total luminosity of stars in the same metallicity range, a lower fraction than those previously found in the Fornax and WLM galaxies, but substantially higher than in the Milky Way halo. Conclusions: At low metallicities, the abundance patterns suggest that GCs in the Milky Way, dwarf galaxies, and M33 experienced similar enrichment histories and/or processes. At higher metallicities, the lower levels of α-enhancement in the GCs found in dwarf galaxies resemble the abundance patterns observed in field stars in nearby dwarfs. Constraining the presence of multiple populations in these GCs is complicated by lack of information about detailed abundances in field stars of the corresponding metallicities. We suggest that correlations such as [Na/Fe] versus [Ni/Fe] may prove useful for this purpose if an accuracy of 0.1 dex or better can be reached for integrated-light measurements. Tables A.1-A.15 (individual abundance measurements) are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/613/A56

Free from the Atmosphere

NASA Astrophysics Data System (ADS)

2007-06-01

An artificial, laser-fed star now shines regularly over the sky of Paranal, home of ESO's Very Large Telescope, one of the world's most advanced large ground-based telescopes. This system provides assistance for the adaptive optics instruments on the VLT and so allows astronomers to obtain images free from the blurring effect of the atmosphere, regardless of the brightness and the location on the sky of the observed target. Now that it is routinely offered by the observatory, the skies seem much sharper to astronomers. In order to counteract the blurring effect of Earth's atmosphere, astronomers use the adaptive optics technique. This requires, however, a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. To surmount this limitation, astronomers now use at Paranal a powerful laser that creates an artificial star, where and when they need it. Two of the Adaptive Optics (AO) science instruments at the Paranal observatory, NACO and SINFONI, have been upgraded to work with the recently installed Laser Guide Star (LGS; see ESO 07/06) and have delivered their first scientific results. This achievement opens astronomers' access to a wealth of new targets to be studied under the sharp eyes of AO. "These unique results underline the advantage of using a Laser Guide Star with Adaptive Optics instruments, since they could not be obtained with Natural Guide Stars," says Norbert Hubin, head of the Adaptive Optics group at ESO. "This is also a crucial milestone towards the multi-laser systems ESO is designing for the VLT and the future E-ELT" (see e.g. ESO 19/07). ESO PR Photo 27a/07 ESO PR Photo 27a/07 An Ultra Luminous Merger (NACO-LGS/VLT) The Laser Guide Star System installed at Paranal uses the PARSEC dye laser developed by MPE-Garching and MPIA-Heidelberg, while the launch telescope and the laser laboratory was developed by ESO. "It is great to see the whole system working so well together," emphasises Richard Davies, project manager of the PARSEC laser. "To test the laser guide star adaptive optics system to its limits, and even beyond, we observed a number of galaxies, ranging from a close neighbour to one that is seen when the universe was very young," explains Markus Kasper, the NACO Instrument Scientist at ESO. The first objects that were observed are interacting galaxies. The images obtained reveal exquisite details, and have a resolution comparable to that of the Hubble Space Telescope. In one case, it was possible to derive for the first time the motion of the stars in two merging galaxies, showing that there are two counter-rotating discs of stars. "The enhanced resolution that laser guide star adaptive optics provides is certain to bring important new discoveries in this exciting area," says Davies ESO PR Photo 27c/07 ESO PR Photo 27c/07 Merging System Arp 220 (SINFONI-LGS/VLT) The astronomers then turned the laser to a galaxy called K20-ID5 which is at a redshift of 2.2 - we are seeing this galaxy when the universe was less than 1/3 of its current age. The image obtained with NACO shows that the stars are concentrated in a much more compact region than the gas. "These observations are both remarkable and exciting," declares Kasper. "They are the first time that it has been possible to trace in such detail the distributions of both the stars and the gas at an epoch where we are witnessing the formation of galaxies similar to our own Milky Way." At the opposite extreme, much nearer to home, LGS-AO observations were made of the active galaxy NGC 4945. The new LGS observations with NACO resolved the central parts into a multitude of individual stars. "It is in galaxies such as these where we can really quantify the star formation history in the vicinity of the nucleus, that we can start to piece together the puzzle of how gas is accreted onto the supermassive black hole, and understand how and when these black holes light up so brightly," says Davies. ESO PR Photo 27e/07 ESO PR Photo 27e/07 Active Galaxy NGC 4945 (NACO-LGS/VLT) Still closer to home, the LGS system can also be applied to solar system objects, such as asteroids or satellites, but also to the study of particular regions of spatially extended bodies like the polar regions of giant planets, where aurora activity is concentrated. During their science verification, the scientists turned the SINFONI instrument with the LGS to a Trans-Neptunian Object, 2003 EL 61. The high image contrast and sensitivity obtained with the use of the LGS mode permit the detection of the two faint satellites known to orbit the TNO. "From such observations one can study the chemical composition of the surface material of the TNO and its satellites (mainly crystalline water ice), estimate their surface properties and constrain their internal structure," explains Christophe Dumas, from ESO. The VLT Laser Guide System is the result of a collaborative work by a team of scientists and engineers from ESO and the Max Planck Institutes for Extraterrestrial Physics in Garching and for Astronomy in Heidelberg, Germany. NACO was built by a Consortium of French and German institutes and ESO. SINFONI was built by a Consortium of German and Dutch Institutes and ESO. More Information Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. This drawback can be surmounted with adaptive optics, allowing the telescope to produce images that are as sharp as if taken from space. This means that finer details in astronomical objects can be studied, and also that fainter objects can be observed. In order to work, adaptive optics needs a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed to a few percent only. To overcome this limitation, astronomers use a powerful laser that creates an artificial star, where and when they need it. The laser beam takes advantage of the layer of sodium atoms that is present in Earth's atmosphere at an altitude of 90 kilometres. Shining at a well-defined wavelength the laser makes it glow. The laser is launched from Yepun, the fourth 8.2-m Unit Telescope of the Very Large Telescope, producing an artificial star. Despite this star being about 20 times fainter than the faintest star that can be seen with the unaided eye, it is bright enough for the adaptive optics to measure and correct the atmosphere's blurring effect. Compared to a normal star, this artificial star has some differing properties that the associated Laser Guide Star (LGS) Adaptive Optics (AO) system has to be able to cope with. A press release, in English and German, is also available from the Max-Planck Institute.

Back on Track

NASA Astrophysics Data System (ADS)

2007-06-01

An artificial, laser-fed star now shines regularly over the sky of Paranal, home of ESO's Very Large Telescope, one of the world's most advanced large ground-based telescopes. This system provides assistance for the adaptive optics instruments on the VLT and so allows astronomers to obtain images free from the blurring effect of the atmosphere, regardless of the brightness and the location on the sky of the observed target. Now that it is routinely offered by the observatory, the skies seem much sharper to astronomers. In order to counteract the blurring effect of Earth's atmosphere, astronomers use the adaptive optics technique. This requires, however, a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed. To surmount this limitation, astronomers now use at Paranal a powerful laser that creates an artificial star, where and when they need it. Two of the Adaptive Optics (AO) science instruments at the Paranal observatory, NACO and SINFONI, have been upgraded to work with the recently installed Laser Guide Star (LGS; see ESO 07/06) and have delivered their first scientific results. This achievement opens astronomers' access to a wealth of new targets to be studied under the sharp eyes of AO. "These unique results underline the advantage of using a Laser Guide Star with Adaptive Optics instruments, since they could not be obtained with Natural Guide Stars," says Norbert Hubin, head of the Adaptive Optics group at ESO. "This is also a crucial milestone towards the multi-laser systems ESO is designing for the VLT and the future E-ELT" (see e.g. ESO 19/07). ESO PR Photo 27a/07 ESO PR Photo 27a/07 An Ultra Luminous Merger (NACO-LGS/VLT) The Laser Guide Star System installed at Paranal uses the PARSEC dye laser developed by MPE-Garching and MPIA-Heidelberg, while the launch telescope and the laser laboratory was developed by ESO. "It is great to see the whole system working so well together," emphasises Richard Davies, project manager of the PARSEC laser. "To test the laser guide star adaptive optics system to its limits, and even beyond, we observed a number of galaxies, ranging from a close neighbour to one that is seen when the universe was very young," explains Markus Kasper, the NACO Instrument Scientist at ESO. The first objects that were observed are interacting galaxies. The images obtained reveal exquisite details, and have a resolution comparable to that of the Hubble Space Telescope. In one case, it was possible to derive for the first time the motion of the stars in two merging galaxies, showing that there are two counter-rotating discs of stars. "The enhanced resolution that laser guide star adaptive optics provides is certain to bring important new discoveries in this exciting area," says Davies ESO PR Photo 27c/07 ESO PR Photo 27c/07 Merging System Arp 220 (SINFONI-LGS/VLT) The astronomers then turned the laser to a galaxy called K20-ID5 which is at a redshift of 2.2 - we are seeing this galaxy when the universe was less than 1/3 of its current age. The image obtained with NACO shows that the stars are concentrated in a much more compact region than the gas. "These observations are both remarkable and exciting," declares Kasper. "They are the first time that it has been possible to trace in such detail the distributions of both the stars and the gas at an epoch where we are witnessing the formation of galaxies similar to our own Milky Way." At the opposite extreme, much nearer to home, LGS-AO observations were made of the active galaxy NGC 4945. The new LGS observations with NACO resolved the central parts into a multitude of individual stars. "It is in galaxies such as these where we can really quantify the star formation history in the vicinity of the nucleus, that we can start to piece together the puzzle of how gas is accreted onto the supermassive black hole, and understand how and when these black holes light up so brightly," says Davies. ESO PR Photo 27e/07 ESO PR Photo 27e/07 Active Galaxy NGC 4945 (NACO-LGS/VLT) Still closer to home, the LGS system can also be applied to solar system objects, such as asteroids or satellites, but also to the study of particular regions of spatially extended bodies like the polar regions of giant planets, where aurora activity is concentrated. During their science verification, the scientists turned the SINFONI instrument with the LGS to a Trans-Neptunian Object, 2003 EL 61. The high image contrast and sensitivity obtained with the use of the LGS mode permit the detection of the two faint satellites known to orbit the TNO. "From such observations one can study the chemical composition of the surface material of the TNO and its satellites (mainly crystalline water ice), estimate their surface properties and constrain their internal structure," explains Christophe Dumas, from ESO. The VLT Laser Guide System is the result of a collaborative work by a team of scientists and engineers from ESO and the Max Planck Institutes for Extraterrestrial Physics in Garching and for Astronomy in Heidelberg, Germany. NACO was built by a Consortium of French and German institutes and ESO. SINFONI was built by a Consortium of German and Dutch Institutes and ESO. More Information Normally, the achievable image sharpness of a ground-based telescope is limited by the effect of atmospheric turbulence. This drawback can be surmounted with adaptive optics, allowing the telescope to produce images that are as sharp as if taken from space. This means that finer details in astronomical objects can be studied, and also that fainter objects can be observed. In order to work, adaptive optics needs a nearby reference star that has to be relatively bright, thereby limiting the area of the sky that can be surveyed to a few percent only. To overcome this limitation, astronomers use a powerful laser that creates an artificial star, where and when they need it. The laser beam takes advantage of the layer of sodium atoms that is present in Earth's atmosphere at an altitude of 90 kilometres. Shining at a well-defined wavelength the laser makes it glow. The laser is launched from Yepun, the fourth 8.2-m Unit Telescope of the Very Large Telescope, producing an artificial star. Despite this star being about 20 times fainter than the faintest star that can be seen with the unaided eye, it is bright enough for the adaptive optics to measure and correct the atmosphere's blurring effect. Compared to a normal star, this artificial star has some differing properties that the associated Laser Guide Star (LGS) Adaptive Optics (AO) system has to be able to cope with. A press release, in English and German, is also available from the Max-Planck Institute.

Something borrowed, something blue: The nature of blue metal-poor stars inferred from their colours and chemical abundances

NASA Astrophysics Data System (ADS)

Hansen, C. J.; Jofré, P.; Koch, A.; McWilliam, A.; Sneden, C. S.

2017-02-01

Blue metal-poor (BMP) stars are main sequence stars that appear bluer and more luminous than normal turnoff stars. They were originally singled out by using B-V and U-B colour cuts.Early studies found that a larger fraction of field BMP stars were binaries compared to normal halo stars. Thus, BMP stars are ideal field blue straggler candidates for investigating internal stellar evolution processes and binary interaction. In particular, the presence or depletion in lithium in their spectra is a powerful indicator of their origin. They are either old, halo blue stragglers experiencing internal mixing processes or mass transfer (Li-depletion), or intermediate-age, single stars of possibly extragalactic origin (2.2 dex halo plateau Li). However, we note that internal mixing processes can lead to an increased level of Li. Hence, this study combines photometry and spectroscopy to unveil the origin of various BMP stars. We first show how to separate binaries from young blue stars using photometry, metallicity and lithium. Using a sample of 80 BMP stars (T > 6300 K), we find that 97% of the BMP binaries have V-Ks0 < 1.08 ± 0.03, while BMP stars that are not binaries lie above this cut in two thirds of the cases. This cut can help classify stars that lack radial velocities from follow-up observations. We then trace the origin of two BMP stars from the photometric sample by conducting a full chemical analysis using new high-resolution and high signal-to-noise spectra. Based on their radial velocities, Li, α and s- and r-process abundances we show that BPS CS22874-042 is a single star (A(Li) = 2.38 ± 0.10 dex) while with A(Li)= 2.23 ± 0.07 dex CD-48 2445 is a binary, contrary to earlier findings. Our analysis emphasises that field blue stragglers can be segregated from single metal-poor stars, using (V-Ks) colours with a fraction of single stars polluting the binary sample, but not vice versa. These two groups can only be properly separated by using information from stellar spectra, illustrating the need for accurate and precise stellar parameters and high-resolution, high-S/N spectra in order to fully understand and classify this intriguing class of stars. Our high-resolution spectrum analysis confirms the findings from the colour cuts and shows that CS 22874-042 is single, while CD -48 2445 is most likely a binary. Moreover, the stellar abundances show that both stars formed in situ; CS 22874-042 carries traces of massive star enrichment and CD -48 2445 shows indications of AGB mass transfer mixed with gases ejected possibly from neutron star mergers. Based on UVES archive data 077.B-0507 and 090.B-0605. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile. Full Table 4 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/598/A54

VizieR Online Data Catalog: GOODS-S CANDELS multiwavelength catalog (Guo+, 2013)

NASA Astrophysics Data System (ADS)

Guo, Y.; Ferguson, H. C.; Giavalisco, M.; Barro, G.; Willner, S. P.; Ashby, M. L. N.; Dahlen, T.; Donley, J. L.; Faber, S. M.; Fontana, A.; Galametz, A.; Grazian, A.; Huang, K.-H.; Kocevski, D. D.; Koekemoer, A. M.; Koo, D. C.; McGrath, E. J.; Peth, M.; Salvato, M.; Wuyts, S.; Castellano, M.; Cooray, A. R.; Dickinson, M. E.; Dunlop, J. S.; Fazio, G. G.; Gardner, J. P.; Gawiser, E.; Grogin, N. A.; Hathi, N. P.; Hsu, L.-T.; Lee, K.-S.; Lucas, R. A.; Mobasher, B.; Nandra, K.; Newman, J. A.; van der Wel, A.

2014-04-01

The Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS; Grogin et al. 2011ApJS..197...35G; Koekemoer et al. 2011ApJS..197...36K) is designed to document galaxy formation and evolution over the redshift range of z=1.5-8. The core of CANDELS is to use the revolutionary near-infrared HST/WFC3 camera, installed on HST in 2009 May, to obtain deep imaging of faint and faraway objects. The GOODS-S field, centered at RAJ2000=03:32:30 and DEJ2000=-27:48:20 and located within the Chandra Deep Field South (CDFS; Giacconi et al. 2002, Cat. J/ApJS/139/369), is a sky region of about 170arcmin2 which has been targeted for some of the deepest observations ever taken by NASA's Great Observatories, HST, Spitzer, and Chandra as well as by other world-class telescopes. The field has been (among others) imaged in the optical wavelength with HST/ACS in F435W, F606W, F775W, and F850LP bands as part of the HST Treasury Program: the Great Observatories Origins Deep Survey (GOODS; Giavalisco et al. 2004, Cat. II/261); in the mid-IR (3.6-24um) wavelength with Spitzer as part of the GOODS Spitzer Legacy Program (PI: M. Dickinson). The CDF-S/GOODS field was observed by the MOSAIC II imager on the CTIO 4m Blanco telescope to obtain deep U-band observations in 2001 September. Another U-band survey in GOODS-S was carried out using the VIMOS instrument mounted at the Melipal Unit Telescope of the VLT at ESO's Cerro Paranal Observatory, Chile. This large program of ESO (168.A-0485; PI: C. Cesarsky) was obtained in service mode observations in UT3 between 2004 August and fall 2006. In the ground-based NIR, imaging observations of the CDFS were carried out in J, H, Ks bands using the ISAAC instrument mounted at the Antu Unit Telescope of the VLT. Data were obtained as part of the ESO Large Programme 168.A-0485 (PI: C. Cesarsky) as well as ESO Programmes 64.O-0643, 66.A-0572, and 68.A-0544 (PI: E. Giallongo) with a total allocation time of ~500 hr from 1999 October to 2007 January. The CANDELS/GOODS-S field was also observed in the NIR as part of the ongoing HAWK-I UDS and GOODS-S survey (HUGS; VLT large program ID 186.A-0898; PI: A. Fontana; A. Fontana et al., in preparation) using the High Acuity Wide field K-band Imager (HAWK-I) on VLT. (1 data file).

Chandra Observations of the Brightest Sunyaev-Zeldovich Effect Cluster

NASA Astrophysics Data System (ADS)

Hughes, John

2011-10-01

We propose deep Chandra observations of ACT-CL J0102-4915, the brightest Sunyaev-Zeldovich effect cluster discovered by the Atacama Cosmology Telescope and South Pole Telescope surveys. These surveys covered approximately 3000 square degrees and are essentially complete to high redshift. Our recent Chandra and VLT optical data reveal ACL-CL J0102-4915 to be undergoing a major merger. It is likely a high redshift {z=0.870} counterpart to the famous A?A?bulletA?A? cluster. New Chandra data will determine the properties of the merger shock and the HST/ACS data will provide a weak lensing mass map.

The deformable secondary mirror of VLT: final electro-mechanical and optical acceptance test results

NASA Astrophysics Data System (ADS)

Briguglio, Runa; Biasi, Roberto; Xompero, Marco; Riccardi, Armando; Andrighettoni, Mario; Pescoller, Dietrich; Angerer, Gerald; Gallieni, Daniele; Vernet, Elise; Kolb, Johann; Arsenault, Robin; Madec, Pierre-Yves

2014-07-01

The Deformable Secondary Mirror (DSM) for the VLT ended the stand-alone electro-mechanical and optical acceptance process, entering the test phase as part of the Adaptive Optics Facility (AOF) at the ESO Headquarter (Garching). The VLT-DSM currently represents the most advanced already-built large-format deformable mirror with its 1170 voice-coil actuators and its internal metrology based on co-located capacitive sensors to control the shape of the 1.12m-diameter 2mm-thick convex shell. The present paper reports the final results of the electro-mechanical and optical characterization of the DSM executed in a collaborative effort by the DSM manufacturing companies (Microgate s.r.l. and A.D.S. International s.r.l.), INAF-Osservatorio Astrofisico di Arcetri and ESO. The electro-mechanical acceptance tests have been performed in the company premises and their main purpose was the dynamical characterization of the internal control loop response and the calibration of the system data that are needed for its optimization. The optical acceptance tests have been performed at ESO (Garching) using the ASSIST optical test facility. The main purpose of the tests are the characterization of the optical shell flattening residuals, the corresponding calibration of flattening commands, the optical calibration of the capacitive sensors and the optical calibration of the mirror influence functions.

Fingerprinting the Milky Way

NASA Astrophysics Data System (ADS)

2007-03-01

Using ESO's Very Large Telescope, an international team of astronomers has shown how to use the chemical composition of stars in clusters to shed light on the formation of our Milky Way. This discovery is a fundamental test for the development of a new chemical tagging technique uncovering the birth and growth of our Galactic cradle. The formation and evolution of galaxies, and in particular of the Milky Way - the 'island universe' in which we live, is one of the major puzzles of astrophysics: indeed, a detailed physical scenario is still missing and its understanding requires the joint effort of observations, theories and complex numerical simulations. ESO astronomer Gayandhi De Silva and her colleagues used the Ultraviolet and Visual Echelle Spectrograph (UVES) on ESO's VLT to find new ways to address this fundamental riddle. ESO PR Photo 15/07 ESO PR Photo 15/07 The Cluster Collinder 261 "We have analysed in great detail the chemical composition of stars in three star-clusters and shown that each cluster presents a high level of homogeneity and a very distinctive chemical signature," says De Silva, who started this research while working at the Mount Stromlo Observatory, Australia. "This paves the way to chemically tagging stars in our Galaxy to common formation sites and thus unravelling the history of the Milky Way," she adds. "Galactic star clusters are witnesses of the formation history of the Galactic disc," says Kenneth Freeman, also from Mount Stromlo and another member of the team. "The analysis of their composition is like studying ancient fossils. We are chasing pieces of galactic DNA!" Open star clusters are among the most important tools for the study of stellar and galactic evolution. They are composed of a few tens up to a few thousands of stars that are gravitationally bound, and they span a wide range of ages. The youngest date from a few million years ago, while the oldest (and more rare) can have ages up to ten billion years. The well-known Pleiades, also called the Seven Sisters, is a young bright open cluster. Conversely, Collinder 261, which was the target of the present team of astronomers, is among the oldest. It can therefore provide useful information on the early days in the existence of our Galaxy. The astronomers used UVES to observe a dozen red giants in the open cluster Collinder 261, located about 25,000 light years from the Galactic Centre. Giants are more luminous, hence they are well suited for high-precision measurements. From these observations, the abundances of a large set of chemical elements could be determined for each star, demonstrating convincingly that all stars in the cluster share the same chemical signature. "This high level of homogeneity indicates that the chemical information survived through several billion years," explains De Silva. "Thus all the stars in the cluster can be associated to the same prehistoric cloud. This corroborates what we had found for two other groups of stars." But this is not all. A comparison with the open cluster called the Hyades, and the group of stars moving with the bright star HR 1614, shows that each of them contains the same elements in different proportions. This indicates that each star cluster formed in a different primordial region, from a different cloud with a different chemical composition. "The consequences of these observations are thrilling," says Freeman. "The ages of open clusters cover the entire life of the Galaxy and each of them is expected to originate from a different patch of 'dough'. Seeing how much sodium, magnesium, calcium, iron and many other elements are present in each star cluster, we are like accurate cooks who can tell the amount of salt, sugar, eggs and flour used in different cookies. Each of them has a unique chemical signature." The astronomers will now aim to measure the chemical abundances in a larger sample of open clusters. Once the "DNA" of each star cluster is inferred, it will be possible to trace the genealogic tree of the Milky Way. This chemical mapping through time and space will be a way to test theoretical models. "The path to an extensive use of chemical tagging is still long," cautions De Silva, "but our study shows that it is possible. When the technique is tested and proven we will be able to get a detailed picture of the way our Galactic cradle formed." More Information The research presented here is discussed in a paper in the Astronomical Journal, volume 133, pages 1161-1175 ("Chemical homogeneity in Collinder 261 and implications for chemical tagging", by G.M. De Silva et al.). The team is composed of Gayandhi De Silva (ESO), Kenneth Freeman, Martin Asplund and Michael Bessell (Mount Stromlo Observatory, Australia), Joss Bland-Hawthorn (Anglo-Australian Observatory, Australia), Remo Collet (Uppsala University, Sweden).

Analysis of molecular hydrogen absorption toward QSO B0642–5038 for a varying proton-to-electron mass ratio

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bagdonaite, J.; Ubachs, W.; Murphy, M. T.

2014-02-10

Rovibronic molecular hydrogen (H{sub 2}) transitions at redshift z {sub abs} ≅ 2.659 toward the background quasar B0642–5038 are examined for a possible cosmological variation in the proton-to-electron mass ratio μ. We utilize an archival spectrum from the Very Large Telescope/Ultraviolet and Visual Echelle Spectrograph (UVES) with a signal-to-noise ratio of ∼35 per 2.5 km s{sup –1} pixel at the observed H{sub 2} wavelengths (335-410 nm). Some 111 H{sub 2} transitions in the Lyman and Werner bands have been identified in the damped Lyα system for which a kinetic gas temperature of ∼84 K and a molecular fraction log fmore » = –2.18 ± 0.08 are determined. The H{sub 2} absorption lines are included in a comprehensive fitting method, which allows us to extract a constraint on a variation of the proton-electron mass ratio Δμ/μ from all transitions at once. We obtain Δμ/μ = (17.1 ± 4.5{sub stat} ± 3.7{sub sys}) × 10{sup –6}. However, we find evidence that this measurement has been affected by wavelength miscalibration errors recently identified in UVES. A correction based on observations of objects with solar-like spectra gives a smaller Δμ/μ value and contributes to a larger systematic uncertainty: Δμ/μ = (12.7 ± 4.5{sub stat} ± 4.2{sub sys}) × 10{sup –6}.« less

Exploring the multifaceted circumstellar environment of the luminous blue variable HR Carinae

NASA Astrophysics Data System (ADS)

Buemi, C. S.; Trigilio, C.; Leto, P.; Umana, G.; Ingallinera, A.; Cavallaro, F.; Cerrigone, L.; Agliozzo, C.; Bufano, F.; Riggi, S.; Molinari, S.; Schillirò, F.

2017-03-01

We present a multiwavelength study of the Galactic luminous blue variable HR Carinae, based on new high-resolution mid-infrared (IR) and radio images obtained with the Very Large Telescope (VLT) and the Australia Telescope Compact Array (ATCA), which have been complemented by far-infrared Herschel-Photodetector Array Camera and Spectrometer (PACS) observations and ATCA archive data. The Herschel images reveal the large-scale distribution of the dusty emitting nebula, which extends mainly to the north-east direction, up to 70 arcsec from the central star, and is oriented along the direction of the space motion of the star. In the mid-infrared images, the brightness distribution is characterized by two arc-shaped structures, tracing an inner envelope surrounding the central star more closely. At radio wavelengths, the ionized gas emission lies on the opposite side of the cold dust with respect to the position of the star, as if the ionized front were confined by the surrounding medium in the north-south direction. Comparison with previous data indicates significant changes in the radio nebula morphology and in the mass-loss rate from the central star, which has increased from 6.1 × 10-6 M⊙ yr-1 in 1994-1995 to 1.17 × 10-5 M⊙ yr-1 in 2014. We investigate possible scenarios that could have generated the complex circumstellar environment revealed by our multiwavelength data.

Tiempo para un cambio

NASA Astrophysics Data System (ADS)

Woltjer, L.

1987-06-01

En la reunion celebrada en diciembre dei ano pasado informe al Consejo de mi deseo de terminar mi contrato como Director General de la ESO una vez que fuera aprobado el proyecto dei VLT, que se espera sucedera hacia fines de este aAo. Cuando fue renovada mi designacion hace tres aAos, el Consejo conocia mi intencion de no completar los cinco aAos dei contrato debido a mi deseo de disponer de mas tiempo para otras actividades. Ahora, una vez terminada la fase preparatoria para el VLT, Y habiendose presentado el proyecto formalmente al Consejo el dia 31 de marzo, y esperando su muy probable aprobacion antes dei termino de este ano, me parece que el 10 de enero de 1988 presenta una excelente fecha para que se produzca un cambio en la administracion de la ESO.

Manufacturing of glassy thin shell for adaptive optics: results achieved

NASA Astrophysics Data System (ADS)

Poutriquet, F.; Rinchet, A.; Carel, J.-L.; Leplan, H.; Ruch, E.; Geyl, R.; Marque, G.

2012-07-01

Glassy thin shells are key components for the development of adaptive optics and are part of future & innovative projects such as ELT. However, manufacturing thin shells is a real challenge. Even though optical requirements for the front face - or optical face - are relaxed compared to conventional passive mirrors, requirements concerning thickness uniformity are difficult to achieve. In addition, process has to be completely re-defined as thin mirror generates new manufacturing issues. In particular, scratches and digs requirement is more difficult as this could weaken the shell, handling is also an important issue due to the fragility of the mirror. Sagem, through REOSC program, has recently manufactured different types of thin shells in the frame of European projects: E-ELT M4 prototypes and VLT Deformable Secondary Mirror (VLT DSM).

The Scientific Return of VLT Programmes

NASA Astrophysics Data System (ADS)

Sterzik, M.; Dumas, C.; Grothkopf, U.; Kaufer, A.; Leibundgut, B.; Marteau, S.; Meakins, S.; Patat, F.; Primas, F.; Rejkuba, M.; Romaniello, M.; Stoehr, F.; Tacconi-Garman, L.; Vera, I.

2015-12-01

An in-depth analysis of the publications from 8414 distinct scheduled VLT observing programmes between April 1999 and March 2015 (Periods 63 to 94) is presented. The productivity by mode (Visitor or Service Mode) and type (Normal and Large, Guaranteed Time, Target of Opportunity, Director's Discretionary Time) are examined through their publication records. We investigate how Service Mode rank classes impact the scientific return. Several results derive from this study: Large Programmes result in the highest productivity, whereas only about half of all scheduled observing programmes produce a refereed publication. Programmes that result in a publication yield on average two refereed papers. B rank class Service Mode Programmes appear to be slightly less productive. Follow-up studies will investigate in more detail the parameters that influence the productivity of the Observatory.

Simplified Quantum Logic with Trapped Ions

DTIC Science & Technology

2016-06-23

j !52mj•E~z !52\\g j~S1~ j !1S2~ j !!~ei~k•z2vLt2f! 1e2i~k•z2vLt2f!). ~2! In this expression, g j5mj•E0 /2\\ is the resonant Rabi fre- quency...by g j ,1g j ,2 /D , where g j ,1 and g j ,2 are the individual Rabi fre- quencies of the two beams when resonantly coupled to the virtual level and D...couples the states un&u↓& and un&u↑& with Rabi frequency @13,14# Vn ,n5 1 \\ u^n z^↑uHI~ j !u↓& zn&u 5g jz^nueih~a1a †!un& z 5g je 2h2/2Ln~h 2!, ~4

Dutch Minister of Science Visits ESO Facilities in Chile

NASA Astrophysics Data System (ADS)

2005-05-01

Mrs. Maria van der Hoeven, the Dutch Minister of Education, Culture and Science, who travelled to the Republic of Chile, arrived at the ESO Paranal Observatory on Friday afternoon, May 13, 2005. The Minister was accompanied, among others, by the Dutch Ambassador to Chile, Mr. Hinkinus Nijenhuis, and Mr. Cornelis van Bochove, the Dutch Director of Science. The distinguished visitors were able to acquaint themselves with one of the foremost European research facilities, the ESO Very Large Telescope (VLT), during an overnight stay at this remote site, and later, with the next major world facility in sub-millimetre and millimetre astronomy, the Atacama Large Millimeter Array (ALMA). At Paranal, the guests were welcomed by the ESO Director General, Dr. Catherine Cesarsky; the ESO Council President, Prof. Piet van der Kruit; the ESO Representative in Chile, Prof. Felix Mirabel; the Director of the La Silla Paranal Observatory, Dr. Jason Spyromilio; by one of the Dutch members of the ESO Council, Prof. Tim de Zeeuw; by the renowned astrophysicist from Leiden, Prof. Ewine van Dishoek, as well as by ESO staff members. The visitors were shown the various high-tech installations at the observatory, including many of the large, front-line VLT astronomical instruments that have been built in collaboration between ESO and European research institutes. Explanations were given by ESO astronomers and engineers and the Minister gained a good impression of the wide range of exciting research programmes that are carried out with the VLT. Having enjoyed the spectacular sunset over the Pacific Ocean from the Paranal deck, the Minister visited the VLT Control Room from where the four 8.2-m Unit Telescopes and the VLT Interferometer (VLTI) are operated. Here, the Minister was invited to follow an observing sequence at the console of the Kueyen (UT2) and Melipal (UT3) telescopes. "I was very impressed, not just by the technology and the science, but most of all by all the people involved," expressed Mrs. Maria van der Hoeven during her visit. "An almost unique level of international cooperation is achieved at ESO, and everything is done by those who can do it best, irrespective of their country or institution. This spirit of excellence is an example for all Europe, notably for the new European Research Council." Catherine Cesarsky, ESO Director General, remarked that Dutch astronomers have been part of ESO from the beginning: "The Dutch astronomy community and industry play a major role in various aspects of the Very Large Telescope, and more particularly in its interferometric mode. With their long-based expertise in radio astronomy, Dutch astronomers greatly contribute in this field, and are now also playing a major role in the construction of ALMA. It is thus a particularly great pleasure to receive Her Excellency, Mrs. Maria van der Hoeven." ESO PR Photo 16d/05 ESO PR Photo 16d/05 Dutch Minister Maria van der Hoeven at Chajnantor - I [Preview - JPEG: 400 x 480 pix - 207k] [Normal - JPEG: 800 x 959 pix - 617k] ESO PR Photo 16e/05 ESO PR Photo 16e/05 Dutch Minister Maria van der Hoeven at Chajnantor - II [Preview - JPEG: 400 x 605 pix - 179k] [Normal - JPEG: 800 x 1210 pix - 522k] Caption: ESO PR Photo 16d/05: In front of the APEX antenna at Chajnantor. From left to right: Prof. Piet van der Kruit, Mrs. Maria van der Hoeven, Prof. Tim de Zeeuw, and Prof. Ewine van Dishoeck. ESO PR Photo 16e/05 shows the Delegation on the 5000m high Llano de Chajnantor plateau. From left to right: Dr. Leo Le Duc, Prof. Felix Mirabel, Prof. Tim de Zeeuw, Prof. Ewine van Dishoeck, Dr. Cornelius van Bochove, Mrs. Maria van der Hoeven, Mr. Hans van der Vlies, Dr. Joerg Eschwey, Mr. Hinkinus Nijenhuis, Prof. Piet van der Kruit, Mr. Hans van den Broek, and Mr. Eduardo Donoso. The delegation spent the night at the Observatory before heading further North in the Chilean Andes to San Pedro de Atacama and from there to the Operation Support Facility of the future ALMA Observatory. On Sunday, May 15, the delegation went to the 5000m Llano de Chajnantor, the future site of the large array of 12m antennas that is being build there and should be completed by 2013. The Minister in particular could visit the 12m APEX (Atacama Pathfinder Experiment) telescope and see the technical infrastructure. "I am fully confident that the worldwide cooperation in ALMA will be equally successful as the VLT, and I am convinced that the discoveries to be made here are meaningful for the Earth we live in", said Mrs. van der Hoeven. "History and future are coming together in the north of Chile, in a very special way," she added. "In the region of the ancient Atacamenos, scientists from all over the world are discovering more and more about the universe and the birth and death of stars. They even find new planets. They do that on Paranal with the VLT and soon will be doing that on the ALMA site." The Minister and her delegation left for Santiago in the afternoon.

Geochemistry of HASP, VLT, and other glasses from double drive tube 79001/2

NASA Technical Reports Server (NTRS)

Lindstrom, D. J.; Wentworth, S. J.; Martinez, R. R.; Mckay, D. S.

1992-01-01

The Apollo 17 double drive tube 79001/2 (station 9, Van Serg Crater) is distinctive because of its extreme maturity, abundance, and variety of glass clasts. It contains mare glasses of both high Ti and very low Ti (VLT) compositions, and highland glasses of all compositions common in lunar regolith samples: highland basalt (feldspathic; Al2O3 greater than 23 wt percent), KREEP (Al2O3 less than 23 wt percent, K2O greater than 0.25 wt percent), and low-K Fra Mauro (LKFM; Al2O3 less than 23 wt percent, K2O less than 0.25 wt percent). It also contains rare specimens of high-alumina, silica-poor (HASP), and ultra Mg glasses. HASP glasses contain insufficient SiO2 to permit the calculation of a standard norm, and are thought to be the product of volatilization during impact melting. They have been studied by electron microprobe major-element analysis techniques but have not previously been analyzed for trace elements. The samples analyzed for this study were polished grain mounts of the 90-160 micron fraction of four sieved samples from the 79001/2 core (depth range 2.3-11.5 cm). A total of 80 glasses were analyzed by SEM/EDS and electron microprobe, and a subset of 33 of the glasses, representing a wide range of compositional types, was chosen for high-sensitivity INAA. A microdrilling device removed disks (mostly 50-100 micron diameter, weighing approx. 0.1-0.5 micro-g) for INAA. Preliminary data reported here are based only on short counts done within two weeks of irradiation.

Eso's Situation in Chile

NASA Astrophysics Data System (ADS)

1995-02-01

ESO, the European Southern Observatory, in reply to questions raised by the international media, as well as an ongoing debate about the so-called "Paranal case" in Chilean newspapers, would like to make a number of related observations concerning its status and continued operation in that country [1]. THE ESO OBSERVATORY SITES IN CHILE The European Southern Observatory, an international organisation established and supported by eight European countries, has been operating more than 30 years in the Republic of Chile. Here ESO maintains one of the world's prime astronomical observatories on the La Silla mountain in the southern part of the Atacama desert. This location is in the Fourth Chilean Region, some 600 km north of Santiago de Chile. In order to protect the La Silla site against dust and light pollution from possible future mining industries, roads and settlements, ESO early acquired the territory around this site. It totals about 825 sq. km and has effectively contributed to the preservation of its continued, excellent "astronomical" quality. Each year, more than 500 astronomers from European countries, Chile and elsewhere profit from this when they come to La Silla to observe with one or more of the 15 telescopes now located there. In 1987, the ESO Council [2] decided to embark upon one of the most prestigious and technologically advanced projects ever conceived in astronomy, the Very Large Telescope (VLT). It will consist of four interconnected 8.2-metre telescopes and will become the largest optical telescope in the world when it is ready. It is safe to predict that many exciting discoveries will be made with this instrument, and it will undoubtedly play a very important role in our exploration of the distant universe and its many mysteries during the coming decades. THE VLT AND PARANAL In order to find the best site for the VLT, ESO performed a thorough investigation of many possible mountain tops, both near La Silla and in Northern Chile. They showed that the best VLT site would be the Paranal Mountain, 700 km north of La Silla and 130 km south of Antofagasta, the capital of the Second Region in Chile. In October 1988, the Chilean Government by an official act donated the land surrounding Paranal (in all 725 sq. km) to ESO. As is the case for La Silla, this would serve to protect the planned, incredibly sensitive mega-telescope against all possible future sources of outside interference. The donation was made on the condition that ESO would indeed proceed with the construction of the VLT at Paranal within the next five years. The corresponding decision was taken by the ESO Council in December 1990. The construction of the VLT observatory site at Paranal started immediately thereafter, thus fulfilling the condition attached to the donation. The construction of the VLT is now well advanced. In Europe, the main parts of the first VLT unit 8.2-metre telescope will be pre-assembled later this year and the first two of the enormous mirrors are being polished. In Chile, the extensive landscaping of the Paranal peak was finished in 1993, during which around 300,000 cubic metres of rock and soil was removed to provide a 100x100 sq. metres platform for the VLT, and the concrete foundations are now ready. The installation of the first telescope enclosure can now begin and the next will start later this year. The first of the four telescopes is expected to start observations in late 1997. All in all, ESO has until now committed about 70 percent of the expected total investment for the VLT, estimated to be approximately 570 million DEM. THE OWNERSHIP OF PARANAL According to information later received, the Chilean Ministry of National Properties ("Bienes Nacionales") inscribed in 1977 in its name various lands in the commune of Taltal, including the area of the Paranal peak. At that time, i.e. ten years before ESO decided to construct the VLT, nobody in this Organisation could imagine that this telescope would one day be constructed at that site. It was only seven years later, in 1984, that ESO initiated the search for a future VLT site that ultimately led to the recommendation in favour of Paranal, the subsequent donation by the Chilean Government and the beginning of the construction, as described above. ESO has never had any doubt on the legality of this donation by the Chilean Government. The Organisation started the work at Paranal in full confidence that this generous act was correct and respected its condition, i.e. to start construction of the VLT observatory within a given time frame. However, in April 1993, when the work at Paranal was already quite advanced, a Chilean family brought a lawsuit against the Chilean State and ESO, claiming that a small part of the land (about 22 sq. km, including the very peak of Paranal) that was inscribed by the state in 1977, had been property of this family. The lawsuit is presently pending with the competent Chilean courts and it is not known when a final judgement will be given. In keeping with its status as an International Organisation and conforming to the international practice of such organisations, ESO decided not to become a party in this lawsuit. The Organisation, therefore, has restricted its involvement to merely invoking the immunity from lawsuit and jurisdiction to which it is entitled (see below). ESO believes that the issue of past ownership is an internal Chilean matter. Nevertheless, it has been widely reported that on January 30, 1995, in response to an appeal by the claimants, a Chambre of the Chilean Supreme Court issued a preliminary decision that may be interpreted as ordering to stop the construction of the VLT during an undetermined period of time. This would seriously delay the entire project and necessarily entail additional, substantial costs. ESO'S IMMUNITIES ESO's relations with its host state, the Republic of Chile, is governed by an international Convention ("Convenio"), signed in 1963 and ratified by the Chilean Congress (Parliament) in 1964. According to this, the Chilean Government "grants to ESO the same immunities, prerogatives, privileges and facilities as the Government applies to the United Nations Economic Commission for Latin America (CEPAL), as granted in the Convention signed in Santiago on 16 February 1953" (Article 4 of the Chile-ESO Convention). Through this, the Chilean Government has in particular recognized that "the possessions and properties of (ESO) wherever they may be, and whoever may have them in his possession, shall be exempt of registration, requisition, confiscation, expropriation and of whatever interference, may it be through executive, administrative, judicial or legislative action" (Art. 4, Sec. 8, CEPAL Convention). Such privileges and immunities are not peculiar to the relations between Chile and ESO. They apply, as already mentioned, to CEPAL as well as to all other United Nations' Agencies and they are today typically recognized by the host states of International Organisations throughout the world. The Chilean Government and ESO agreed in 1983-84 by an exchange of diplomatic notes that these privileges and immunities apply not only to the La Silla observatory, but equally to any other observatory site that the Organisation may establish in the future in the Republic of Chile. It is obvious that, in order to exclude a possible breach of international law, the reported preliminary decision requires to be considered and interpreted in the light of these privileges and immunities. ESO trusts that the competent Chilean authorities will take the appropriate action and decisions which are required for ensuring the Organisation's international status and its protection from any public interference into its possessions and properties. In a Press Conference at the ESO Headquarters in Santiago de Chile on February 13, 1995, Mr. Daniel Hofstadt, ESO's highest-ranking representative in Chile, stated on behalf of the Organisation that "ESO is in Chile with the purpose to do science and not to participate in polemics or litigations. For this reason, ESO has until now been silent in these matters, but we have now become obliged to make our opinion known". The ESO representative also made it clear, that "ESO does not question the rights of the claimants to recur to the Chilean Tribunals which must decide on the matter of ownership, and that ESO cannot be party to this lawsuit". He added that "ESO fully trusts that the Chilean Government will do whatever is necessary to defend the immunity of ESO". THE CURRENT SITUATION During the past few days, declarations from high officials at the Chilean Ministry of Foreign Affairs have been made which clearly confirm ESO's immunity of jurisdiction from Chilean Courts. The same opinion has been ventured by Chilean experts in international law, quoted in various Chilean newspapers. On Friday, February 17, the Chilean Minister of Foreign Affairs, Mr. Jose M. Insulza, made a similar, very eloquent statement. ESO welcomes these articulate expressions that support its official position and trusts that the current situation will be speedily resolved by the competent Chilean authorities, so that the construction work at Paranal will not be stopped. During the past three decades, ESO's presence in Chile has been characterised by good relations to all sides. The development of astronomy in Chile during the past decades has reached such a level that it will now benefit from a new quality of cooperation. In addition to its past and numerous services to Chilean astronomy, ESO has recently considered to establish a "guaranteed" observing time for astronomers from this country, both at La Silla and the future VLT observatory on Paranal. With a proposed 10 percent quota for the VLT, Chilean astronomers will in fact have free access to the equivalent of 40 percent of one 8.2-metre telescope; the associated, not insignificant cost is entirely carried by ESO. ESO has also considered to incorporate elements of Chilean labour legislation into its rules and regulations for local staff. These proposed actions are contained in an Amendment to the Convention which was initialled late last year and is now awaiting signature by the Chilean Government and ratification by the Chilean Congress, as well as by the ESO Council. FUTURE INFORMATION In conjunction with the present Press Release ESO has prepared a pre-edited video-news reel with video-clips (approx. 4 minutes) about Paranal and the current work there. It is available for TV channels in the usual formats (Beta-SP and M II). Please fax your request to the ESO Information Service (+4989-3202362). ESO will continue to keep the media informed about further important developments around the VLT Project, in addition to the usual scientific and technological news, available through Press Releases and the ESO house journal, "The Messenger/El Mensajero". ----- Notes: [1] See also the following ESO Press Releases: PR 14/94 of 29 September 1994, PR 13/94 of 9 August 1994; PR 12/94 of 10 June 1994; PR 08/94 of 5 May 1994, and PR 07/94 of 21 April 1994. [2] The Council of ESO consists of two representatives from each of the eight member states. It is the highest legislative authority of the organisation and normally meets twice a year. ----- ESO Press Information is made available on the World-Wide Web (URL: http://www.hq.eso.org/) and on CompuServe (space science and astronomy area, GO SPACE).

ERIS: preliminary design phase overview

NASA Astrophysics Data System (ADS)

Kuntschner, Harald; Jochum, Lieselotte; Amico, Paola; Dekker, Johannes K.; Kerber, Florian; Marchetti, Enrico; Accardo, Matteo; Brast, Roland; Brinkmann, Martin; Conzelmann, Ralf D.; Delabre, Bernard A.; Duchateau, Michel; Fedrigo, Enrico; Finger, Gert; Frank, Christoph; Rodriguez, Fernando G.; Klein, Barbara; Knudstrup, Jens; Le Louarn, Miska; Lundin, Lars; Modigliani, Andrea; Müller, Michael; Neeser, Mark; Tordo, Sebastien; Valenti, Elena; Eisenhauer, Frank; Sturm, Eckhard; Feuchtgruber, Helmut; George, Elisabeth M.; Hartl, Michael; Hofmann, Reiner; Huber, Heinrich; Plattner, Markus P.; Schubert, Josef; Tarantik, Karl; Wiezorrek, Erich; Meyer, Michael R.; Quanz, Sascha P.; Glauser, Adrian M.; Weisz, Harald; Esposito, Simone; Xompero, Marco; Agapito, Guido; Antichi, Jacopo; Biliotti, Valdemaro; Bonaglia, Marco; Briguglio, Runa; Carbonaro, Luca; Cresci, Giovanni; Fini, Luca; Pinna, Enrico; Puglisi, Alfio T.; Quirós-Pacheco, Fernando; Riccardi, Armando; Di Rico, Gianluca; Arcidiacono, Carmelo; Dolci, Mauro

2014-07-01

The Enhanced Resolution Imager and Spectrograph (ERIS) is the next-generation adaptive optics near-IR imager and spectrograph for the Cassegrain focus of the Very Large Telescope (VLT) Unit Telescope 4, which will soon make full use of the Adaptive Optics Facility (AOF). It is a high-Strehl AO-assisted instrument that will use the Deformable Secondary Mirror (DSM) and the new Laser Guide Star Facility (4LGSF). The project has been approved for construction and has entered its preliminary design phase. ERIS will be constructed in a collaboration including the Max- Planck Institut für Extraterrestrische Physik, the Eidgenössische Technische Hochschule Zürich and the Osservatorio Astrofisico di Arcetri and will offer 1 - 5 μm imaging and 1 - 2.5 μm integral field spectroscopic capabilities with a high Strehl performance. Wavefront sensing can be carried out with an optical high-order NGS Pyramid wavefront sensor, or with a single laser in either an optical low-order NGS mode, or with a near-IR low-order mode sensor. Due to its highly sensitive visible wavefront sensor, and separate near-IR low-order mode, ERIS provides a large sky coverage with its 1' patrol field radius that can even include AO stars embedded in dust-enshrouded environments. As such it will replace, with a much improved single conjugated AO correction, the most scientifically important imaging modes offered by NACO (diffraction limited imaging in the J to M bands, Sparse Aperture Masking and Apodizing Phase Plate (APP) coronagraphy) and the integral field spectroscopy modes of SINFONI, whose instrumental module, SPIFFI, will be upgraded and re-used in ERIS. As part of the SPIFFI upgrade a new higher resolution grating and a science detector replacement are envisaged, as well as PLC driven motors. To accommodate ERIS at the Cassegrain focus, an extension of the telescope back focal length is required, with modifications of the guider arm assembly. In this paper we report on the status of the baseline design. We will also report on the main science goals of the instrument, ranging from exoplanet detection and characterization to high redshift galaxy observations. We will also briefly describe the SINFONI-SPIFFI upgrade strategy, which is part of the ERIS development plan and the overall project timeline.

The VLT-FLAMES Tarantula Survey. XVII. Physical and wind properties of massive stars at the top of the main sequence

NASA Astrophysics Data System (ADS)

Bestenlehner, J. M.; Gräfener, G.; Vink, J. S.; Najarro, F.; de Koter, A.; Sana, H.; Evans, C. J.; Crowther, P. A.; Hénault-Brunet, V.; Herrero, A.; Langer, N.; Schneider, F. R. N.; Simón-Díaz, S.; Taylor, W. D.; Walborn, N. R.

2014-10-01

The evolution and fate of very massive stars (VMS) is tightly connected to their mass-loss properties. Their initial and final masses differ significantly as a result of mass loss. VMS have strong stellar winds and extremely high ionising fluxes, which are thought to be critical sources of both mechanical and radiative feedback in giant H ii regions. However, how VMS mass-loss properties change during stellar evolution is poorly understood. In the framework of the VLT-Flames Tarantula Survey (VFTS), we explore the mass-loss transition region from optically thin O star winds to denser WNh Wolf-Rayet star winds, thereby testing theoretical predictions. To this purpose we select 62 O, Of, Of/WN, and WNh stars, an unprecedented sample of stars with the highest masses and luminosities known. We perform a spectral analysis of optical VFTS as well as near-infrared VLT/SINFONI data using the non-LTE radiative transfer code CMFGEN to obtain both stellar and wind parameters. For the first time, we observationally resolve the transition between optically thin O star winds and optically thick hydrogen-rich WNh Wolf-Rayet winds. Our results suggest the existence of a "kink" between both mass-loss regimes, in agreement with recent Monte Carlo simulations. For the optically thick regime, we confirm the steep dependence on the classical Eddington factor Γe from previous theoretical and observational studies. The transition occurs on the main sequence near a luminosity of 106.1L⊙, or a mass of 80 ... 90 M⊙. Above this limit, we find that - even when accounting for moderate wind clumping (with fv = 0.1) - wind mass-loss rates are enhanced with respect to standard prescriptions currently adopted in stellar evolution calculations. We also show that this results in substantial helium surface enrichment. Finally, based on our spectroscopic analyses, we are able to provide the most accurate ionising fluxes for VMS known to date, confirming the pivotal role of VMS in ionising and shaping their environments. Appendices are available in electronic form at http://www.aanda.org

Physiological correlates of 2-mile run performance as determined using a novel on-demand treadmill.

PubMed

Tolfrey, Keith; Hansen, Simon A; Dutton, Katie; McKee, Tom; Jones, Andrew M

2009-08-01

The purpose of this study was to assess the reproducibility of an on-demand motorised treadmill to measure 2-mile (3.2 km) race performance and to examine the physiological variables that best predict this free-running performance in active men. Twelve men (mean (SD): age, 28 (9) years; stature, 1.79 (0.05) m; body mass, 72 (9) kg) completed the study in which maximum oxygen uptake (VO2 max), running economy, and running speedin the abstract section. They appear in the rest of the paper.), running economy, and running speed at VO2 max (vVO2 max), lactate threshold (vLT), and 4 mmol.L-1 fixed blood lactate concentration (v4) were measured. Subsequently, the maximal lactate steady state (MLSS) was identified using a series of 30-min treadmill runs. Finally, each participant completed a 2-mile running performance trial on 2 separate occasions, using an on-demand treadmill that adjusts belt speed according to the participant's position on the moving belt. The average 2-mile run speed was 15.7 (SD, 1.9) km.h-1, with small individual differences between repeat-performance trials (intraclass correlation coefficient = 0.99, 95% CI 0.953 to 0.996; standard error of measurement as coefficient of variation = 1.5%, 95% CI 1.0% to 2.5%). Bivariate regression analyses identified VO2 max, vVO2 max, VO2 (mL.kg-1.min-1) at MLSS, vLT, v4, and velocity at MLSS (vMLSS) as the strongest individual predictor variables (r2 = 0.69 to 0.87; standard error of the estimate = 1.08 to 0.72 km.h-1) for 2-mile running performance. The vLT and vMLSS explained 85% and 87% of the variance in running performance, respectively, suggesting that there is considerable shared variance between these parameters. In conclusion, the on-demand treadmill system provided a reliable measure of distance running performance. Both vLT and vMLSS were strong predictors of 2-mile running performance, with vMLSS explaining marginally more of the variance.

Telemedicine-guided, very low-dose international normalized ratio self-control in patients with mechanical heart valve implants.

PubMed

Koertke, Heinrich; Zittermann, Armin; Wagner, Otto; Secer, Songuel; Sciangula, Alfonso; Saggau, Werner; Sack, Falk-Udo; Ennker, Jürgen; Cremer, Jochen; Musumeci, Francesco; Gummert, Jan F

2015-06-01

To study in patients performing international normalized ratio (INR) self-control the efficacy and safety of an INR target range of 1.6-2.1 for aortic valve replacement (AVR) and 2.0-2.5 for mitral valve replacement (MVR) or double valve replacement (DVR). In total, 1304 patients undergoing AVR, 189 undergoing MVR and 78 undergoing DVR were randomly assigned to low-dose INR self-control (LOW group) (INR target range, AVR: 1.8-2.8; MVR/DVR: 2.5-3.5) or very low-dose INR self-control once a week (VLO group) and twice a week (VLT group) (INR target range, AVR: 1.6-2.1; MVR/DVR: 2.0-2.5), with electronically guided transfer of INR values. We compared grade III complications (major bleeding and thrombotic events; primary end-points) and overall mortality (secondary end-point) across the three treatment groups. Two-year freedom from bleedings in the LOW, VLO, and VLT groups was 96.3, 98.6, and 99.1%, respectively (P = 0.008). The corresponding values for thrombotic events were 99.0, 99.8, and 98.9%, respectively (P = 0.258). The risk-adjusted composite of grade III complications was in the per-protocol population (reference: LOW-dose group) as follows: hazard ratio = 0.307 (95% CI: 0.102-0.926; P = 0.036) for the VLO group and = 0.241 (95% CI: 0.070-0.836; P = 0.025) for the VLT group. The corresponding values of 2-year mortality were = 1.685 (95% CI: 0.473-5.996; P = 0.421) for the VLO group and = 4.70 (95% CI: 1.62-13.60; P = 0.004) for the VLT group. Telemedicine-guided very low-dose INR self-control is comparable with low-dose INR in thrombotic risk, and is superior in bleeding risk. Weekly testing is sufficient. Given the small number of MVR and DVR patients, results are only valid for AVR patients. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2014. For permissions please email: journals.permissions@oup.com.

Expectations Increase as VLT First Light Approaches

NASA Astrophysics Data System (ADS)

1998-05-01

Two weeks before the moment of "First Light" of Unit Telescope no. 1 of the Very Large Telescope (VLT) , the ESO Team at the Paranal Observatory reports good progress of the preparatory work. The crucial optimization of the world's first, thin 8.2-metre mirror proceeds according to the established plan. It is thus expected that this important event will take place as foreseen, i.e. during the night of May 25-26, 1998 . If no unforeseen obstacles are encountered, the first scientific images will then be presented during a series of near-simultaneous Press Conferences in the ESO member countries on May 27 . The photos will be published on the WWW the same day, together with explanatory texts. In preliminary optical tests at the first VLT Unit Telescope (UT1), the initial adjustment of the active optics system that controls the telescope optics has demonstrated excellent results. In particular, the first tests have verified the fine optical performance of the 8.2-m primary mirror and of the complex control system that maintains the shape of this thin and flexible Zerodur mirror. In short test exposures with the guide probe (the technical device that is used to steer the telescope) - i.e., not yet with the scientific CCD-camera that will be used for the First Light images - the telescope has been following the external seeing provided by the Paranal site. Image quality of better than 0.5 arcsec has been achieved routinely. "We are pleased with the progress and confident that the telescope will live up to the expectations", says Riccardo Giacconi , Director General of ESO. "The team at Paranal is doing a great job." For more details about the various media activities surrounding the VLT First Light event, please consult the First Light homepage. A list of locations, times and contact addresses for the Press Conferences is available on the web. How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), a new-generation of 3D spectro-imager dedicated to night astronomy

NASA Astrophysics Data System (ADS)

Sayède, Frédéric; Puech, Mathieu; Mein, Pierre; Bonifacio, Piercarlo; Malherbe, Jean-Marie; Galicher, Raphaël.; Amans, Jean-Philippe; Fasola, Gilles

2014-07-01

Multichannel Subtractive Double Pass (MSDP) spectrographs have been widely used in solar spectroscopy because of their ability to provide an excellent compromise between field of view and spatial and spectral resolutions. Compared with other types of spectrographs, MSDP can deliver simultaneous monochromatic images at higher spatial and spectral resolutions without any time-scanning requirement (as with Fabry-Perot spectrographs), and with limited loss of flux. These performances are obtained thanks to a double pass through the dispersive element. Recent advances with VPH (Volume phase holographic) Grisms as well as with image slicers now make MSDP potentially sensitive to much smaller fluxes. We present S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), which is a new concept for extending MSDP to night-time astronomy. It is based on new generation reflecting plane image slicers working with large apertures specific to night-time telescopes. The resulting design could be potentially very attractive and innovative for different domains of astronomy, e.g., the simultaneous spatial mapping of accurately flux-calibrated emission lines between OH sky lines in extragalactic astronomy or the simultaneous imaging of stars, exoplanets and interstellar medium. We present different possible MSDP/S4EI configurations for these science cases and expected performances on telescopes such as the VLT.

VizieR Online Data Catalog: Arches cluster: IR phot., extinction and masses (Habibi+, 2013)

NASA Astrophysics Data System (ADS)

Habibi, M.; Stolte, A.; Brandner, W.; Hussmann, B.; Motohara, K.

2013-05-01

We observed the Arches cluster out to its tidal radius using Ks-band and H-band imaging obtained on June 6-10 2008 with NAOS/CONICA at the VLT combined with Subaro/Cisco J-band data to gain a full understanding of the cluster mass distribution. The acquired Ks-band images cover four fields of 27.8*27.8(arcsec) each, provided by the medium resolution camera (S27) with a pixel scale of 0.027(arcsec). During the Ks-band observations, the natural visual seeing varied from 0.61" to 0.98". We achieved typical spatial resolutions of 0.081-0.135(arcsec) on individual frames using this AO setup. Seeing-limited J-band observations, on July 17, 2000, were performed with the CISCO spectrograph and camera which provided a pixel scale of 0.116(arcsec) and a field of view of 2*2(arcmin). An average seeing of 0.49(arcsec) resulted into a Full Width at Half Maximum (FWHM) of the point-spread function (PSF) of 0.39(arcsec) on the combined image. The catalogue includes derived infrared-photometry in J, H and Ks bands as well as derived individual extinction value and stellar masses. We used the NAOS-CONICA observations obtained in March 2002 in the central part of the Arches cluster to cover the whole cluster area. (1 data file).

Model-independent Exoplanet Transit Spectroscopy

NASA Astrophysics Data System (ADS)

Aronson, Erik; Piskunov, Nikolai

2018-05-01

We propose a new data analysis method for obtaining transmission spectra of exoplanet atmospheres and brightness variation across the stellar disk from transit observations. The new method is capable of recovering exoplanet atmosphere absorption spectra and stellar specific intensities without relying on theoretical models of stars and planets. We simultaneously fit both stellar specific intensity and planetary radius directly to transit light curves. This allows stellar models to be removed from the data analysis. Furthermore, we use a data quality weighted filtering technique to achieve an optimal trade-off between spectral resolution and reconstruction fidelity homogenizing the signal-to-noise ratio across the wavelength range. Such an approach is more efficient than conventional data binning onto a low-resolution wavelength grid. We demonstrate that our analysis is capable of reproducing results achieved by using an explicit quadratic limb-darkening equation and that the filtering technique helps eliminate spurious spectral features in regions with strong telluric absorption. The method is applied to the VLT FORS2 observations of the exoplanets GJ 1214 b and WASP-49 b, and our results are in agreement with previous studies. Comparisons between obtained stellar specific intensity and numerical models indicates that the method is capable of accurately reconstructing the specific intensity. The proposed method enables more robust characterization of exoplanetary atmospheres by separating derivation of planetary transmission and stellar specific intensity spectra (that is model-independent) from chemical and physical interpretation.

Environmental Considerations and Sustainability of Base Camps in Contingency Operations

DTIC Science & Technology

2011-05-12

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CO emission tracing a warp or radial flow within ≲100 au in the HD 100546 protoplanetary disk

NASA Astrophysics Data System (ADS)

Walsh, Catherine; Daley, Cail; Facchini, Stefano; Juhász, Attila

2017-11-01

We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) images of 12CO J = 3-2 emission from the protoplanetary disk around the Herbig Ae star, HD 100546. We expand upon earlier analyses of this data and model the spatially-resolved kinematic structure of the CO emission. Assuming a velocity profile which prescribes a flat or flared emitting surface in Keplerian rotation, we uncover significant residuals with a peak of ≈7δv, where δv = 0.21 km s-1 is the width of a single spectral resolution element. The shape and extent of the residuals reveal the possible presence of a severely warped and twisted inner disk extending to at most 100 au. Adapting the model to include a misaligned inner gas disk with (I) an inclination almost edge-on to the line of sight, and (II) a position angle almost orthogonal to that of the outer disk reduces the residuals to <3δv. However, these findings are contrasted by recent VLT/SPHERE, MagAO/GPI, and VLTI/PIONIER observations of HD 100546 that show no evidence of a severely misaligned inner dust disk down to spatial scales of 1 au. An alternative explanation for the observed kinematics are fast radial flows mediated by (proto)planets. Inclusion of a radial velocity component at close to free-fall speeds and inwards of ≈50 au results in residuals of ≈4δv. Hence, the model including a radial velocity component only does not reproduce the data as well as that including a twisted and misaligned inner gas disk. Molecular emission data at a higher spatial resolution (of order 10 au) are required to further constrain the kinematics within ≲100 au. HD 100546 joins several other protoplanetary disks for which high spectral resolution molecular emission shows that the gas velocity structure cannot be described by a purely Keplerian velocity profile with a universal inclination and position angle. Regardless of the process, the most likely cause is the presence of an unseen planetary companion.

Spectroscopic Evolution of Disintegrating Planetesimals: Minute to Month Variability in the Circumstellar Gas Associated with WD 1145+017

DOE Office of Scientific and Technical Information (OSTI.GOV)

Redfield, Seth; Cauley, P. Wilson; Duvvuri, Girish M.

With the recent discovery of transiting planetary material around WD 1145+017, a critical target has been identified that links the evolution of planetary systems with debris disks and their accretion onto the star. We present a series of observations, five epochs over a year, taken with Keck and the VLT, which for the first time show variability of circumstellar absorption in the gas disk surrounding WD 1145+017 on timescales of minutes to months. Circumstellar absorption is measured in more than 250 lines of 14 ions among 10 different elements associated with planetary composition, e.g., O, Mg, Ca, Ti, Cr, Mn,more » Fe, and Ni. Broad circumstellar gas absorption with a velocity spread of 225 km s{sup −1} is detected, but over the course of a year blueshifted absorption disappears, while redshifted absorption systematically increases. A correlation of equivalent width and oscillator strength indicates that the gas is not highly optically thick (median τ ≈ 2). We discuss simple models of an eccentric disk coupled with magnetospheric accretion to explain the basic observed characteristics of these high-resolution and high signal-to-noise observations. Variability is detected on timescales of minutes in the two most recent observations, showing a loss of redshifted absorption for tens of minutes, coincident with major transit events and consistent with gas hidden behind opaque transiting material. This system currently presents a unique opportunity to learn how the gas causing the spectroscopic, circumstellar absorption is associated with the ongoing accretion evidenced by photospheric contamination, as well as the transiting planetary material detected in photometric observations.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sajadian, Sedighe; Hundertmark, Markus, E-mail: s.sajadian@cc.iut.ac.ir

A close-in giant planetary (CGP) system has a net polarization signal whose value varies depending on the orbital phase of the planet. This polarization signal is either caused by the stellar occultation or by reflected starlight from the surface of the orbiting planet. When the CGP system is located in the Galactic bulge, its polarization signal becomes too weak to be measured directly. One method for detecting and characterizing these weak polarization signatures due to distant CGP systems is gravitational microlensing. In this work, we focus on potential polarimetric observations of highly magnified microlensing events of CGP systems. When themore » lens is passing directly in front of the source star with its planetary companion, the polarimetric signature caused by the transiting planet is magnified. As a result, some distinct features in the polarimetry and light curves are produced. In the same way, microlensing amplifies the reflection-induced polarization signal. While the planet-induced perturbations are magnified whenever these polarimetric or photometric deviations vanish for a moment, the corresponding magnification factor of the polarization component(s) is related to the planet itself. Finding these exact times in the planet-induced perturbations helps us to characterize the planet. In order to evaluate the observability of such systems through polarimetric or photometric observations of high-magnification microlensing events, we simulate these events by considering confirmed CGP systems as their source stars and conclude that the efficiency for detecting the planet-induced signal with the state-of-the-art polarimetric instrument (FORS2/VLT) is less than 0.1%. Consequently, these planet-induced polarimetry perturbations can likely be detected under favorable conditions by the high-resolution and short-cadence polarimeters of the next generation.« less

Polarimetry Microlensing of Close-in Planetary Systems

NASA Astrophysics Data System (ADS)

Sajadian, Sedighe; Hundertmark, Markus

2017-04-01

A close-in giant planetary (CGP) system has a net polarization signal whose value varies depending on the orbital phase of the planet. This polarization signal is either caused by the stellar occultation or by reflected starlight from the surface of the orbiting planet. When the CGP system is located in the Galactic bulge, its polarization signal becomes too weak to be measured directly. One method for detecting and characterizing these weak polarization signatures due to distant CGP systems is gravitational microlensing. In this work, we focus on potential polarimetric observations of highly magnified microlensing events of CGP systems. When the lens is passing directly in front of the source star with its planetary companion, the polarimetric signature caused by the transiting planet is magnified. As a result, some distinct features in the polarimetry and light curves are produced. In the same way, microlensing amplifies the reflection-induced polarization signal. While the planet-induced perturbations are magnified whenever these polarimetric or photometric deviations vanish for a moment, the corresponding magnification factor of the polarization component(s) is related to the planet itself. Finding these exact times in the planet-induced perturbations helps us to characterize the planet. In order to evaluate the observability of such systems through polarimetric or photometric observations of high-magnification microlensing events, we simulate these events by considering confirmed CGP systems as their source stars and conclude that the efficiency for detecting the planet-induced signal with the state-of-the-art polarimetric instrument (FORS2/VLT) is less than 0.1%. Consequently, these planet-induced polarimetry perturbations can likely be detected under favorable conditions by the high-resolution and short-cadence polarimeters of the next generation.

Artificial intelligence applied to the automatic analysis of absorption spectra. Objective measurement of the fine structure constant

NASA Astrophysics Data System (ADS)

Bainbridge, Matthew B.; Webb, John K.

2017-06-01

A new and automated method is presented for the analysis of high-resolution absorption spectra. Three established numerical methods are unified into one `artificial intelligence' process: a genetic algorithm (Genetic Voigt Profile FIT, gvpfit); non-linear least-squares with parameter constraints (vpfit); and Bayesian model averaging (BMA). The method has broad application but here we apply it specifically to the problem of measuring the fine structure constant at high redshift. For this we need objectivity and reproducibility. gvpfit is also motivated by the importance of obtaining a large statistical sample of measurements of Δα/α. Interactive analyses are both time consuming and complex and automation makes obtaining a large sample feasible. In contrast to previous methodologies, we use BMA to derive results using a large set of models and show that this procedure is more robust than a human picking a single preferred model since BMA avoids the systematic uncertainties associated with model choice. Numerical simulations provide stringent tests of the whole process and we show using both real and simulated spectra that the unified automated fitting procedure out-performs a human interactive analysis. The method should be invaluable in the context of future instrumentation like ESPRESSO on the VLT and indeed future ELTs. We apply the method to the zabs = 1.8389 absorber towards the zem = 2.145 quasar J110325-264515. The derived constraint of Δα/α = 3.3 ± 2.9 × 10-6 is consistent with no variation and also consistent with the tentative spatial variation reported in Webb et al. and King et al.

Optomechanical design and testing of the VLT tertiary mirrors

NASA Astrophysics Data System (ADS)

Bollinger, Wolfgang; Juranek, Hans J.; Schulte, Stefan; May, K.; Michel, Alain

2000-07-01

The Tertiary Mirrors for the ESO Very Large Telescope project consist of four optical flats (elliptical, 890 X 1260 mm2). The achieved opto-mechanical design is challenging since it provides high optical overall quality combined with high stiffness (70 Hz Eigenfrequency) and low mass (total mass of 180 kg for the complete unit). Schott (Mainz, Germany) produces the lightweight Zerodur blanks. Carl Zeiss has designed and manufactured the mirror and its support cell. Last not least it became necessary to install the biggest testing equipment for flats in Europe to guarantee for a scientifically correct verification of the quality of the complete unit. All four mirrors have been delivered to ESO.

40+ Years of Instrumentation for the La Silla Paranal Observatory

NASA Astrophysics Data System (ADS)

D'Odorico, S.

2018-03-01

As ESO Period 100 comes to a close, I look back at the development of ESO's instrumentation programme over more than 40 years. Instrumentation and detector activities were initially started by a small group of designers, engineers, technicians and astronomers while ESO was still at CERN in Geneva in the late 1970s. They have since led to the development of a successful suite of optical and infrared instruments for the La Silla Paranal Observatory, as testified by the continuous growth in the number of proposals for observing time and in the publications based on data from ESO telescopes. The instrumentation programme evolved significantly with the VLT and most instruments were developed by national institutes in close cooperation with ESO. This policy was a cornerstone of the VLT programme from the beginning and a key to its success.

Operational metrics for the ESO Very Large Telescope: lessons learned and future steps

NASA Astrophysics Data System (ADS)

Primas, F.; Marteau, S.; Tacconi-Garman, L. E.; Mainieri, V.; Mysore, S.; Rejkuba, M.; Hilker, M.; Patat, F.; Sterzik, M.; Kaufer, A.; Mieske, S.

2016-07-01

When ESO's Very Large Telescope opened its first dome in April 1999 it was the first ground-based facility to offer to the scientific community access to an 8-10m class telescope with both classical and queue observing. The latter was considered to be the most promising way to ensure the observing flexibility necessary to execute the most demanding scientific programmes under the required, usually very well defined, conditions. Since then new instruments have become operational and 1st generation ones replaced, filling the 12 VLT foci and feeding the VLT Interferometer and its four Auxiliary Telescopes. Operating efficiently such a broad range of instruments installed and available every night of the year on four 8-metre telescopes offers many challenges. Although it may appear that little has changed since 1999, the underlying VLT operational model has evolved in order to accommodate different requirements from the user community and features of new instruments. Did it fulfil its original goal and, if so, how well? How did it evolve? What are the lessons learned after more than 15 years of operations? A careful analysis and monitoring of statistics and trends in Phase 1 and Phase 2 has been deployed under the DOME (Dashboard for Operational Metrics at ESO) project. The main goal of DOME is to provide robust metrics that can be followed with time in a user-friendly manner. Here, we summarize the main findings on the handling of service mode observations and present the most recent developments.

Revisiting the variable star population in NGC 6229 and the structure of the horizontal branch

NASA Astrophysics Data System (ADS)

Arellano Ferro, A.; Mancera Piña, P. E.; Bramich, D. M.; Giridhar, Sunetra; Ahumada, J. A.; Kains, N.; Kuppuswamy, K.

2015-09-01

We report an analysis of new V and I CCD time series photometry of the distant globular cluster NGC 6229. The principal aims were to explore the field of the cluster in search of new variables, and to Fourier decompose the RR Lyrae light curves in pursuit of physical parameters. We found 25 new variables: 10 RRab, 5 RRc, 6 SR, 1 CW, 1 SX Phe, and 2 that we were unable to classify. Secular period changes were detected and measured in some favourable cases. The classifications of some of the known variables were rectified. The Fourier decomposition of RRab and RRc light curves was used to independently estimate the mean cluster value of [Fe/H] and distance. From the RRab stars we found [Fe/H]UVES = -1.31 ± 0.01(statistical) ± 0.12(systematic) ([Fe/H]ZW = -1.42) and a distance of 30.0 ± 1.5 kpc, and from the RRc stars we found [Fe/H]UVES = -1.29 ± 0.12 and a distance of 30.7 ± 1.1 kpc, respectively. Absolute magnitudes, radii and masses are also reported for individual RR Lyrae stars. Also discussed are the independent estimates of the cluster distance from the tip of the red giant branch, 34.9 ± 2.4 kpc and from the period-luminosity relation of SX Phe stars, 28.9 ± 2.2 kpc. The distribution of RR Lyrae stars in the horizontal branch shows a clear empirical border between stable fundamental and first overtone pulsators which has been noted in several other clusters; we interpret it as the red edge of the first overtone instability strip.

Retirement of Massimo Tarenghi

NASA Astrophysics Data System (ADS)

Madsen, C.

2013-09-01

Massimo Tarenghi, chronologically MPG/ESO project scientist, NTT project manager, VLT programme manager and first Director, ALMA Director and ESO Representative in Chile, has retired after 35 years at ESO. A brief summary of his achievements is presented.

VizieR Online Data Catalog: Reflectance spectra of 12 Trojans and Hildas (Marsset+, 2014)

NASA Astrophysics Data System (ADS)

Marsset, M.; Vernazza, P.; Gourgeot, F.; Dumas, C.; Birlan, M.; Lamy, P.; Binzel, R. P.

2014-07-01

We present 17 reflectance spectra of 12 high albedo (pv>0.14) Trojans (8 objects) and Hildas (4 objects) obtained with the ESO/VLT Echelle spectrograph X-SHOOTER in the 0.3-2.2um spectral range (14 spectra) and with the NASA/IRTF spectrograph SpeX in the 0.8-2.5um spectral range (3 spectra). X-SHOOTER spectra were normalized to unity at 0.55um and SpeX spectra were normalized to unity at 2.2um . The spectra presented in this work were collected between April and December 2013. (18 data files).

ESO PR Highlights in 2007

NASA Astrophysics Data System (ADS)

2008-01-01

Another great year went by for ESO, the European Organisation for Astronomical Research in the Southern Hemisphere. From 1 January 2007, with the official joining of the Czech Republic, ESO has 13 member states, and since September, ESO has a new Director General, Tim de Zeeuw (ESO 03/07 and 38/07). Many scientific discoveries were made possible with ESO's telescopes. Arguably, the most important is the discovery of the first Earth-like planet in the habitable zone of a low-mass red dwarf (ESO 22/07). If there is water on this planet, then it should be liquid! ESO PR Highlights 2007 This is a clickable map. These are only some of the press releases issued by ESO in 2007. For a full listing, please go to ESO 2007 page. In our own Solar System also, astronomers made stunning breakthroughs with ESO's telescopes, observing the effect of the light from the Sun on an asteroid's rotation (ESO 11/07), describing in unprecedented detail the double asteroid Antiope (ESO 18/07), peering at the rings of Uranus (ESO 37/07), discovering a warm south pole on Neptune (ESO 41/07), showing a widespread and persistent morning drizzle of methane over the western foothills of Titan's major continent (ESO 47/07), and studying in the greatest details the wonderful Comet McNaught (ESO 05/07 and 07/07). In the study of objects slightly more massive than planets, the VLT found that brown dwarfs form in a similar manner to normal stars (ESO 24/07). The VLT made it also possible to measure the age of a fossil star that was clearly born at the dawn of time (ESO 23/07). Other discoveries included reconstructing the site of a flare on a solar-like star (ESO 53/07), catching a star smoking (ESO 34/07), revealing a reservoir of dust around an elderly star (ESO 43/07), uncovering a flat, nearly edge-on disc of silicates in the heart of the magnificent Ant Nebula (ESO 42/07), finding material around a star before it exploded (ESO 31/07), fingerprinting the Milky Way (ESO 15/07), revealing a rich circular cluster of stars (ESO 12/07), hunting galaxies (ESO 40/07), discovering teenage galaxies (ESO 52/07), and finding the first known triplet of supermassive black holes (ESO 02/07). On the instrumentation side, the VLT has been equipped with a new 'eye' to study the Universe in the near-infrared, Hawk-I (ESO 36/07), while the Laser Guide Star used at the VLT to create an artificial star appears to fulfil all its promises (ESO 27/07 and 33/07). Successful tests were also done of a crucial technology for Extremely Large Telescopes (ESO 19/07). The VLT Rapid Response Mode showed it unique capabilities in the study of gamma-ray bursts (ESO 17/07), as did the REM, a robotic telescope at La Silla, that allowed astronomers to measure for the first time the speed of matter ejected in these tremendous explosions (ESO 26/07). The world's largest bolometer camera for submillimetre astronomy, LABOCA, is now in service at the 12-m APEX telescope (ESO 35/07), while the construction of ALMA moves forwards. Two 12-m ALMA prototype antennas were first linked together as an integrated system to observe an astronomical object (ESO 10/07), the ALMA Operations Support Facility is almost completed (ESO 13/07), and the ALMA transporters were shipped to Chile (ESO 32/07 and 45/07). ESO is also present on the educational front with, for example, its annual international contest for students, Catch a Star (ESO 21/07 and 46/07). In April 2007, ESO organised with its partners the second EIROforum Science on Stage festival, a unique event, showcasing the very best of today's science education and to which participated the European Commissioner for Science and Research, Janez Potočnik. The Commissioner also visited the Paranal observatory (ESO 48/07) and took part in the observation of a beautiful galaxy (ESO 49/07). This was not the only nice image coming out from ESO telescopes. A rather amazing Cosmic Bird - or a gigantic Tinker Bell - was photographed (ESO 55/07), as well as a Purple Rose (ESO 16/07) and a stellar firework (ESO 39/07). And last but least, at the end of the year, the United Nations passed a resolution proclaiming 2009 the International Year of Astronomy (ESO 54/07).

First Results from the UT1 Science Verification Programme

NASA Astrophysics Data System (ADS)

1998-11-01

Performance verification is a step which has regularly been employed in space missions to assess and qualify the scientific capabilities of an instrument. Within this framework, it was the goal of the Science Verification program to submit the VLT Unit Telescope No. 1 (UT1) to the scrutiny that can only be achieved in an actual attempt to produce scientifically valuable results. To this end, an attractive and diversified set of observations were planned in advance to be executed at the VLT. These Science Verification observations at VLT UT1 took place as planned in the period from August 17 to September 1, 1998, cf. the September issue of the ESO Messenger ( No. 93, p. 1 ) and ESO PR 12/98 for all details. Although the meteorological conditions on Paranal were definitely below average, the telescope worked with spectacular efficiency and performance throughout the entire period, and very valuable data were gathered. After completion of all observations, the Science Verification Team started to prepare all of the datasets for the public release that took place on October 2, 1998. The data related to the Hubble Deep Field South (now extensively observed by the Hubble Space Telescope) were made public world-wide, while the release of other data was restricted to ESO member states. With this public release ESO intended to achieve two specific goals: offer to the scientific community an early opportunity to work on valuable VLT data, and in the meantime submit the VLT to the widest possible scrutiny. With the public release, many scientists started to analyse scientifically the VLT data, and the following few examples of research programmes are meant to give a sample of the work that has been carried out on the Science Verification data during the past two months. They represent typical investigations that will be carried out in the future with the VLT. Many of these will be directed towards the distant universe, in order to gather insight on the formation and evolution of galaxies, galaxy clusters, and large scale structure. Others will concentrate on more nearby objects, including stars and nebulae in the Milky Way galaxy, and some will attempt to study our own solar system. The following six research programmes were presented at the Press Conference that took place at the ESO Headquarters in Garching (Germany) today. Deep Galaxy Counts and Photometric Redshifts in the HDF-S NIC3 Field The goal of this programme was to verify the capability of the VLT by obtaining the deepest possible ground-based images and using multicolour information to derive the redshifts (and hence the distances) of the faintest galaxies. The space distribution, luminosity and colour of these extreme objects may provide crucial information on the initial phases of the evolution of the universe. The method is known as photometric redshift determination . The VLT Test Camera was used to collect CCD images for a total of 16.6 hours in five spectral filters (U, B, V, R and I) in the so-called HDF-S NIC3 field. This is a small area (about 1 arcmin square) of the southern sky where very deep observations in the infrared bands J, H and K (1.1, 1.6 and 2.2µm, respectively) have been obtained by the Hubble Space Telescope (HST). The observations were combined and analyzed by a team of astronomers at ESO and the Observatory of Rome (Italy). Galaxies were detected in the field down to magnitude ~ 27-28. In most colours, the planned limiting values of the fluxes were successfully reached. ESO PR Photo 48a/98 ESO PR Photo 48a/98 [Preview - JPEG: 800 x 856 pix - 144k] [High-Res - JPEG: 3000 x 3210 pix - 728k] PR Photo 48a/98 shows some examples of photometric redshift determination for faint galaxies in the HDF-S NIC3 field. The filled points are the fluxes measured in the five colors observed with the VLT Test Camera (U, B, V, R and I) and in the infrared H spectral band with the NICMOS instrument on the Hubble Space Telescope. The curves constitute the best fit to the points obtained from a library of more than 400,000 synthetic spectra of galaxies at various redshifts (Fontana et al., in preparation). For most of these very faint sources, it is not possible to collect enough photons to measure the recession velocity (the redshift) by spectroscopy, even with an 8-m telescope. The redshifts and the main galaxy properties are then determined by comparing the colour observations with synthetic spectra (see PR Photo 48a/98 ). This has been done for more than one hundred galaxies in the field brighter than magnitude 26.5. Around 20 are found to be at redshifts larger than 2. The brighter ones are excellent candidates for future detailed studies with the UT1 instruments FORS1 and ISAAC. The scientists involved in this study are: Sandro D'Odorico, Richard Hook, Alvio Renzini, Piero Rosati, Rodolfo Viezzer (ESO) and Adriano Fontana, Emanuele Giallongo, Francesco Poli (Rome Observatory, Italy). A Gravitational Einstein Ring Because the gravitational pull of matter bends the path of light rays, astronomical objects - stars, galaxies and galaxy clusters - can act like lenses, which magnify and severely distort the images of galaxies behind them, producing weird pictures as in a hall of mirrors. In the most extreme case, where the foreground lensing galaxy and the background galaxy are perfectly lined up, the image of the background galaxy is stretched into a ring. Such an image is known as an Einstein ring , because the correct formula for the bending of light was first described by the famous phycisist Albert Einstein . ESO PR Photo 48b/98 ESO PR Photo 48b/98 [Preview - JPEG: 800 x 1106 pix - 952k] [High-Res - JPEG: 3000 x 4148 pix - 5.4Mb] ESO PR Photo 48c/98 ESO PR Photo 48c/98 [Preview - JPEG: 800 x 977 pix - 272k] [High-Res - JPEG: 3000 x 3664 pix - 1.4Mb] PR Photo 48b/98 (left) shows a new, true colour image of an Einstein ring (upper centre of photo), first discovered at ESO in 1995. The ring, which is the stretched image of a galaxy far out in the Universe, stands out clearly in green, and the red galaxy inside the ring is the lens. The discovery image was very faint, but this new picture, taken with the VLT during the Science Verification Programme allows a much clearer view of the ring because of the great light-gathering capacity of the telescope and, not least, because of the superb image quality. In Photo 48c/98 (right), four images illustrate the deduced model of the lensing effect. In the upper left, the observed ring has been enlarged and the image of the lensing galaxy removed by image processing. Below it is a model of the gravitational field (potential) around this galaxy along with the "true" image of the background galaxy shown. At the lower right is the resulting gravitationally magnified and distorted image of the background galaxy, which to the upper right has been de-sharpened to the same image quality as the observed image. The similarity between the two is most convincing. The picture shows a new, true colour image of an Einstein ring, first discovered at ESO in 1995. The ring, which is the stretched image of a galaxy far out in the Universe, stands out clearly in green, and the red galaxy inside the ring is the lens. The discovery image was very faint, but this new picture, taken with the VLT during the Science Verification Programme allows a much clearer view of the ring because of the great light-gathering capacity the telescope and, not least, because of the superb image quality. Gravitational lensing provides a very useful tool with which to study the Universe. As "weighing scales", it provides a measure of the mass within the lensing body, and as a "magnifying glass", it allows us to see details in objects which would otherwise be beyond the reach of current telescopes. This new detailed picture has allowed a much more accurate measurement of the mass of the lensing galaxy, revealing the presence of vast quantities of "unseen" matter, five times more than if just the light from the galaxy is taken into account. This additional material represents some of the Universe's dark matter . The gravitational lens action is also magnifying the background object by a factor of ten, providing an unparalleled view of this very distant galaxy which is in a stage of active star-formation. The scientists involved in this study are : Palle Møller (ESO), Stephen J. Warren (Blackett Laboratory, Imperial College, UK), Paul C. Hewett (Institute of Astronomy, Cambridge, UK) and Geraint F. Lewis (Dept. of Physics and Astronomy, University of Victoria, Canada). An Extremely Red Galaxy One of the main goals of modern cosmology is to understand when and how the galaxies formed. In the very last years, many high-redshift (i.e. very distant) galaxies have been found, suggesting that some galaxies were already assembled, when the Universe was much younger than now. None of these high-redshift galaxies have ever been found to be a bona-fide red elliptical galaxy . The VLT, however, with its very good capabilities for infrared observations, is an ideal instrument to investigate when and how the red elliptical galaxies formed. The VLT Science Verification images have provided unique multicolour information about an extremely red galaxy that was originally (Treu et al., 1998, A&A Letters, Vol. 340, p. 10) identified on the Hubble Deep Field South (HDF-S) Test Image. This galaxy is shown in PR Photo 48d/98 that is an enlargment from ESO PR Photo 35b/98. It was detected on Near-IR images and also on images obtained in the optical part of the spectrum, at the very faint limit of magnitude B ~ 29 in the blue. However, this galaxy has not been detected in the near-ultraviolet band. ESO PR Photo 48d/98 ESO PR Photo 48d/98 [Preview - JPEG: 800 x 594 pix - 264k] [High-Res - JPEG: 3000 x 2229 pix - 1.8Mb] ESO PR Photo 48e/98 ESO PR Photo 48e/98 [Preview - JPEG: 800 x 942 pix - 96k] [High-Res - JPEG: 3000 x 3533 pix - 576k] PR Photo 48d/98 (left) shows the very red galaxy (at the arrow) in the Hubble Deep Field South , discussed here. Photo 48e/98 (right) is the spectrum of a typical elliptical galaxy, redshifted to z = 1.8 and compared with the brightness of the galaxy in different wavebands (crosses), as measured during the VLT SV programme and the Hubble Deep Field South Test Program (the cross to the right). The arrow indicates the upper limit by the VLT SV in the ultraviolet band. It can be seen that these observations are fully consistent with the object being an old, elliptical galaxy at the high redshift of z=1.8 , i.e. at an epoch, when the Universe was much younger than now. The new ISAAC instrument at VLT UT1 will be able to obtain an infrared spectrum of this galaxy and thus to affirm or refute this provisional conclusion. The colours measured at the VLT and on the HST Test Image are very well matched by those of an old elliptical galaxy at redshift z ~ 1.8 ; see Photo 48e/98 . All the available evidence is thus consistent with this object being an elliptical galaxy with the highest-known redshift for this galaxy type. A preliminary analysis of Hubble Deep Field South data, just released, seems to support this hypothesis. If these conclusions are confirmed by direct measurement of its spectrum, this galaxy must already have been "old" (i.e. significantly evolved) when the Universe had an age of only about one fifth of its present value. A spectroscopic confirmation is still outstanding, but is now possible with the ISAAC instrument at VLT UT1. A positive result would demonstrate that elliptical galaxies can form very early in the history of the Universe. The scientists involved in this study are: Massimo Stiavelli, Tommaso Treu (also Scuola Normale Superiore, Italy), Stefano Casertano, Mark Dickinson, Henry Ferguson, Andrew Fruchter, Crystal Martin (STSci, Baltimore, USA), Piero Rosati and Rodolfo Viezzer (ESO), Marcella Carollo (Johns Hopkins University, Baltimore, USA) and Henry Tieplitz (NASA, Goddard Space Flight Center, Greenbelt, USA). Lyman-alpha Companions and Extended Nebulosity around a Quasar at Redshift z=2.2 In current theories of galaxy formation, luminous galaxies we see to-day were built up through repeated merging of smaller protogalactic clumps. Quasars, prodigious sources pouring out 100 to 1000 times as much light as an entire galaxy, have been used as markers of galaxy formation activity and have guided astronomers in their hunting of primeval galaxies and large-scale structures at high redshift. A supermassive black-hole, swallowing stars, gas and dust, is thought to be the engine powering a quasar and the interaction of the galaxy hosting the black-hole with neighboring galaxies is expected to play a key role in "feeding the monster". At intermediate redshift, a large fraction of radio-loud quasars and radio galaxies inhabit rich clusters of galaxies, whereas radio-quiet quasars are rarely found in very rich environments. Furthermore, tidal interaction between quasars and their nearby companions is also the favoured explanation for the presence of large gaseous nebulosities associated with radio-loud quasars and radio galaxies. At high redshift, searches for Lyman-alpha quasar companions and emission-line nebulosities show strong similarities with those seen at lower redshift, although the detection rate is lower. ESO PR Photo 48f/98 ESO PR Photo 48f/98 [Preview - JPEG: 800 x 977 pix - 184k] [High-Res - JPEG: 3000 x 3662 pix - 1.1Mb] ESO PR Photo 48g/98 ESO PR Photo 48g/98 [Preview - JPEG: 800 x 966 pix - 328k] [High-Res - JPEG: 3000 x 3621 pix - 1.8Mb] PR Photo 48f/98 (left) is a false-colour reproduction of a B-band image of the field around the radio-weak quasar J2233-606 in the Hubble Deep Field South (HDF-S) . Photo 48g/98 (right) represents emission from the same direction at a wavelength that corresponds to Lyman-alpha emission at the redshift ( z = 2.2 ) of the quasar. Three Lyman-alpha candidate companions are indicated with arrows. Note also the extended nebulosity around the quasar. A search for Lyman-alpha companions to the radio-weak quasar J2233-606 in the Hubble Deep Field South (HDF-S) was conducted during the VLT UT1 SV programme in a small field of 1.2 x 1.3 arcmin 2 , centered on the quasar. Candidate Lyman-alpha companions were identified by subtracting a broad-band B (blue) image, that traces the galaxy stellar populations, from a narrow-band image, spectrally centered on the redshifted, narrow Lyman-alpha emission line of the quasar ( z = 2.2 ). Three Lyman-alpha candidate companions were discovered at angular distances of 15 to 23 arcsec, or 200 to 300 kpc (650,000 to 1,000,000 light-years) at the distance corresponding to the quasar redshift. The emission lines are very strong, relative to the continuum emission of the galaxies - this could be a consequence of the strong ionizing radiation field of the quasar. These companions to the quasar may trace a large-scale structure which would extend over larger distances beyond the observed, small field. Even more striking is the presence of a very extended nebulosity whose size (120 kpc x 160 kpc) and Lyman-alpha luminosity (3 x 10 44 erg/cm 2 /s) are among the largest observed around radio galaxies and radio-loud quasars, but rarely seen around a radio-weak quasar. Tidal interaction between the northern, very nearby companion and the quasar is clearly present: the companion is embedded in the quasar nebulosity, most of its gas has been stripped and lies in a tail westwards of the galaxy. The scientists involved in this study are: Jacqueline Bergeron (ESO), Stefano Cristiani, Stephane Arnouts, Gianni Fasano (Padova, Italy) and Patrick Petitjean (Institut d'Astrophysique, Paris, France). Very Distant Galaxy Clusters During the past years, it has become possible to detect and subsequently study progressively more distant clusters of galaxies. For this research programme, UT1 Science Verification data were used, in combination with data obtained with the SOFI instrument at the ESO New Technology Telescope (NTT) at La Silla, to confirm the existence of two very distant galaxy clusters at redshift z ~ 1 , that had originally been detected in the ESO Imaging Survey. This redshift corresponds to an epoch when the age of the Universe was only two-thirds of the present. ESO PR Photo 48h/98 ESO PR Photo 48h/98 [Preview - JPEG: 800 x 917 pix - 896k] [High-Res - JPEG: 3000 x 3438 pix - 6.0Mb] PR Photo 48h/98 (left) is a colour composite that shows the now confirmed cluster EIS0046-2930 . The image has been produced by combining the V (green-yellow), R (red) and I (Near-IR) exposures with the Test Camera obtained during the VLT-UT1 Science Verification. The yellow-orange galaxies are the cluster members and the bluer objects are galaxies belonging to the general field population. The cluster center is at the location of the largest (yellow-orange) cluster galaxy to the left of the center of the image. The field measures 90 x 90 arcsec. This was achieved by the detection of a spatial excess density of galaxies, with measured colour equal to that of elliptical galaxies at this redshift, as established by counts in the respective sky areas. The field of one these clusters is shown in PR Photo 48h/98 . These new data show that the VLT will most certainly play a major role in the studies of the cluster galaxy population in such distant systems. This will contribute to shed important new light on the evolution of galaxies. Furthermore, the VLT clearly has the potential to identify and confirm the reality of many more such clusters and thereby to increase considerably the number of known objects. This will be important in order to determine more accurate values of the basic cosmological constants, and thus for our understanding of the evolution of the Universe as a whole. The presentation was made by Lisbeth Fogh Olsen (Copenhagen Observatory, Denmark, and ESO) on behalf of the scientists involved in this study. Icy Planets in the Outer Solar System Observations with large optical telescopes during the past years have begun to cast more light on the still very little known, distant icy planets in the outer solar system. Until November 1998, about 70 of these have been discovered outside the orbit of Neptune (between 30 and 50 AU, or 4,500 to 7,500 million km, from the Sun). They are accordingly referred to as Trans-Neptunian Objects (TNOs) . Those found so far are believed to represent the "tip of the iceberg" of a large population of such objects belonging to the so-called Kuiper Belt . This is a roughly disk-shaped region between about 50 and 120 AU (about 7,500 to 18,000 million km) from the Sun, in which remnant bodies from the formation of the solar system are thought to be present. From their measured brightness and the distance, it is found that most known TNOs have diameters of the order of a few hundred kilometres. About half of those known move in elongated Pluto-like orbits, the others move somewhat further out in stable, circular orbits. During the two-week Science Verification programme, approximately 200 minutes were spent on a small observing programme aimed at obtaining images of some TNOs in different wavebands (B, V, R and I). Since this programme was primarily designed as a back-up to be executed during less favourable atmospheric conditions, some of the observations could not be used. However, images of three faint TNOs were recorded during an excellent series of 1-10 min exposures. From these data, it was possible to measure quite accurate magnitudes (and thus approximate sizes) and to determine their colours. One of them, 1996 TL66, was among the bluest TNOs ever observed. It is believed that this is because its surface has undergone recent transformation, possibly due to collisions with other objects or the breaking-off of small pieces from the surface, in both cases revealing "fresh" layers below. The combination of all available exposures made it possible to look for faint and tenous atmospheres around these TNOs, but none were found. These results show that it is possible, with little effort and even under quite unfavourable observing conditions, to obtain valuable information with the VLT about icy objects in the outer solar system. Of even greater interest will be future spectroscopic observations with FORS and ISAAC that will allow to study the surface composition in some detail, with the potential of providing direct information about (nearly?) pristine material from the early phases of the solar system. The scientists involved in this study are: Olivier Hainaut, Hermann Boehnhardt, Catherine Delahodde and Richard West (ESO) and Karen Meech (Institute of Astronomy, Hawaii, USA). How to obtain ESO Press Information ESO Press Information is made available on the World-Wide Web (URL: http://www.eso.org ). ESO Press Photos may be reproduced, if credit is given to the European Southern Observatory.

Detection of Atmospheric CO on Pluto with ALMA

NASA Astrophysics Data System (ADS)

Gurwell, Mark; Lellouch, Emmanuel; Butler, Bryan; Moullet, Arielle; Moreno, Raphael; Bockelée-Morvan, Dominique; Biver, Nicolas; Fouchet, Thierry; Lis, Darek; Stern, Alan; Young, Leslie; Young, Eliot; Weaver, Hal; Boissier, Jeremie; Stansberry, John

2015-11-01

We observed Pluto and Charon using the Atacama Large Millimeter/submillimeter Array (ALMA) interferometer in Northern Chile on June 12.2 and June 13.15, 2015, just one month prior to the New Horizons flyby of the system. The configuration of ALMA at the time provided ~0.3" resolution, allowing separation of emission from Pluto and Charon. This project targeted multiple science goals, including a search for HCN in Pluto's atmosphere [1] and high precision measurements of the individual brightness temperatures of Pluto and Charon [2], also presented at this meeting. Here we report the high SNR detection of carbon monoxide in the atmosphere of Pluto. The CO(3-2) rotational line, at 345.796 GHz (867 μm), was observed with 117 kHz spectral resolution for 45 min (on-source) on each date, providing ~3.5mJy/channel RMS. CO emission was clearly detected on both days, with a contrast of ~65 mJy above the Pluto continuum, and ~1.8 MHz FWHM linewidth, with the combined integrated line SNR >50. The presence of CO in Pluto's atmosphere is expected due to it's presence as ice on the surface in vapor pressure equilibrium with the atmosphere (e.g. [3],[4]), and it was previously detected at modest SNR in the near-IR using the VLT [5]. A preliminary assessment based upon the CO line wings shows the fractional abundance of CO is 500-750 ppm, consistent with that found in [5]. Further, the shape of the line core emission (assuming a constant CO mixing ratio), suggests that the atmospheric temperature rises quickly from the surface to ~100-110 K in the altitude range 20-70 km but decreases above that, falling to about 70 K by 200 km altitude. A detailed line inversion analysis will be performed and results presented.[1] Lellouch et al, this meeting. [2] Butler et al., this meeting. [3] Owen et al (1993), Science, 261, pp. 745-748. [4] Spencer et al (1993), In Pluto and Charon, pp. 435-473. Univ. of Arizona Press, Tucson. [5] Lellouch et al (2011), A&A, 530, L4.

Evolution of protoplanetary disks from their taxonomy in scattered light: Group I vs. Group II

NASA Astrophysics Data System (ADS)

Garufi, A.; Meeus, G.; Benisty, M.; Quanz, S. P.; Banzatti, A.; Kama, M.; Canovas, H.; Eiroa, C.; Schmid, H. M.; Stolker, T.; Pohl, A.; Rigliaco, E.; Ménard, F.; Meyer, M. R.; van Boekel, R.; Dominik, C.

2017-07-01

Context. High-resolution imaging reveals a large morphological variety of protoplanetary disks. To date, no constraints on their global evolution have been found from this census. An evolutionary classification of disks was proposed based on their IR spectral energy distribution, with the Group I sources showing a prominent cold component ascribed to an earlier stage of evolution than Group II. Aims: Disk evolution can be constrained from the comparison of disks with different properties. A first attempt at disk taxonomy is now possible thanks to the increasing number of high-resolution images of Herbig Ae/Be stars becoming available. Methods: Near-IR images of six Group II disks in scattered light were obtained with VLT/NACO in polarimetric differential imaging, which is the most efficient technique for imaging the light scattered by the disk material close to the stars. We compare the stellar/disk properties of this sample with those of well-studied Group I sources available from the literature. Results: Three Group II disks are detected. The brightness distribution in the disk of HD 163296 indicates the presence of a persistent ring-like structure with a possible connection with the CO snowline. A rather compact (<100 AU) disk is detected around HD 142666 and AK Sco. A taxonomic analysis of 17 Herbig Ae/Be sources reveals that the difference between Group I and Group II is due to the presence or absence of a large disk cavity (≳5 AU). There is no evidence supporting the evolution from Group I to Group II. Conclusions: Group II disks are not evolved versions of the Group I disks. Within the Group II disks, very different geometries exist (both self-shadowed and compact). HD 163296 could be the primordial version of a typical Group I disk. Other Group II disks, like AK Sco and HD 142666, could be smaller counterparts of Group I unable to open cavities as large as those of Group I. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under program number 095.C-0658(A).

Discovery of a Metal-poor, Luminous Post-AGB Star that Failed the Third Dredge-up

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamath, D.; Winckel, H. Van; Wood, P. R.

Post-asymptotic giant branch (post-AGB) stars are known to be chemically diverse. In this paper we present the first observational evidence of a star that has failed the third dredge-up (TDU). J005252.87-722842.9 is an A-type ( T {sub eff} = 8250 ± 250 K) luminous (8200 ± 700 L {sub ⊙}) metal-poor ([Fe/H] = −1.18 ± 0.10) low-mass ( M {sub initial} ≈ 1.5–2.0 M {sub ⊙}) post-AGB star in the Small Magellanic Cloud. Through a systematic abundance study, using high-resolution optical spectra from UVES, we found that this likely post-AGB object shows an intriguing photospheric composition with no confirmed carbon-enhancementmore » (upper limit of [C/Fe] < 0.50) nor enrichment of s -process elements. We derived an oxygen abundance of [O/Fe] = 0.29 ± 0.1. For Fe and O, we took the effects of nonlocal thermodynamic equilibrium into account. We could not derive an upper limit for the nitrogen abundance as there are no useful nitrogen lines within our spectral coverage. The chemical pattern displayed by this object has not been observed in single or binary post-AGBs. Based on its derived stellar parameters and inferred evolutionary state, single-star nucleosynthesis models predict that this star should have undergone TDU episodes while on the AGB, and it should be carbon enriched. However, our observations are in contrast with these predictions. We identify two possible Galactic analogs that are likely to be post-AGB stars, but the lack of accurate distances (hence luminosities) to these objects does not allow us to confirm their post-AGB status. If they have low luminosities, then they are likely to be dusty post-RGB stars. The discovery of J005252.87-722842.9 reveals a new stellar evolutionary channel whereby a star evolves without any TDU episodes.« less

Multiple origins for the DLA at zabs = 0.313 toward PKS 1127-145 indicated by a complex dust depletion pattern of Ca, Ti, and Mn

NASA Astrophysics Data System (ADS)

Guber, C. R.; Richter, P.; Wendt, M.

2018-01-01

Aims: We aim to investigate the dust depletion properties of optically thick gas in and around galaxies and its origin we study in detail the dust depletion patterns of Ti, Mn, and Ca in the multi-component damped Lymanα (DLA) absorber at zabs = 0.313 toward the quasar PKS 1127-145. Methods: We performed a detailed spectral analysis of the absorption profiles of Ca II, Mn II, Ti II, and Na I associated with the DLA toward PKS 1127-145, based on optical high-resolution data obtained with the UVES instrument at the Very Large Telescope. We obtained column densities and Doppler-parameters for the ions listed above and determine their gas-phase abundances, from which we conclude on their dust depletion properties. We compared the Ca and Ti depletion properties of this DLA with that of other DLAs. Results: One of the six analyzed absorption components (component 3) shows a striking underabundance of Ti and Mn in the gas-phase, indicating the effect of dust depletion for these elements and a locally enhanced dust-to-gas ratio. In this DLA and in other similar absorbers, the Mn II abundance follows that of Ti II very closely, implying that both ions are equally sensitive to the dust depletion effects. Conclusions: Our analysis indicates that the DLA toward PKS 1127-145 has multiple origins. With its narrow line width and its strong dust depletion, component 3 points toward the presence of a neutral gas disk from a faint LSB galaxy in front of PKS 1127-145, while the other, more diffuse and dust-poor, absorption components possibly are related to tidal gas features from the interaction between the various, optically confirmed galaxy-group members. In general, the Mn/Ca II ratio in sub-DLAs and DLAs possibly serves as an important indicator to discriminate between dust-rich and dust-poor in neutral gas in and around galaxies.

Fourth Light at Paranal!

NASA Astrophysics Data System (ADS)

2000-09-01

VLT YEPUN Joins ANTU, KUEYEN and MELIPAL It was a historical moment last night (September 3 - 4, 2000) in the VLT Control Room at the Paranal Observatory , after nearly 15 years of hard work. Finally, four teams of astronomers and engineers were sitting at the terminals - and each team with access to an 8.2-m telescope! From now on, the powerful "Paranal Quartet" will be observing night after night, with a combined mirror surface of more than 210 m 2. And beginning next year, some of them will be linked to form part of the unique VLT Interferometer with unparalleled sensitivity and image sharpness. YEPUN "First Light" Early in the evening, the fourth 8.2-m Unit Telescope, YEPUN , was pointed to the sky for the first time and successfully achieved "First Light". Following a few technical exposures, a series of "first light" photos was made of several astronomical objects with the VLT Test Camera. This instrument was also used for the three previous "First Light" events for ANTU ( May 1998 ), KUEYEN ( March 1999 ) and MELIPAL ( January 2000 ). These images served to evaluate provisionally the performance of the new telescope, mainly in terms of mechanical and optical quality. The ESO staff were very pleased with the results and pronounced YEPUN fit for the subsequent commissioning phase. When the name YEPUN was first given to the fourth VLT Unit Telescope, it was supposed to mean "Sirius" in the Mapuche language. However, doubts have since arisen about this translation and a detailed investigation now indicates that the correct meaning is "Venus" (as the Evening Star). For a detailed explanation, please consult the essay On the Meaning of "YEPUN" , now available at the ESO website. The first images At 21:39 hrs local time (01:39 UT), YEPUN was turned to point in the direction of a dense Milky Way field, near the border between the constellations Sagitta (The Arrow) and Aquila (The Eagle). A guide star was acquired and the active optics system quickly optimized the mirror system. At 21:44 hrs (01:44 UT), the Test Camera at the Cassegrain focus within the M1 mirror cell was opened for 30 seconds, with the planetary nebula Hen 2-428 in the field. The resulting "First Light" image was immediately read out and appeared on the computer screen at 21:45:53 hrs (01:45:53 UT). "Not bad! - "Very nice!" were the first, "business-as-usual"-like comments in the room. The zenith distance during this observation was 44° and the image quality was measured as 0.9 arcsec, exactly the same as that registered by the Seeing Monitoring Telescope outside the telescope building. There was some wind. ESO PR Photo 22a/00 ESO PR Photo 22a/00 [Preview - JPEG: 374 x 400 pix - 128k] [Normal - JPEG: 978 x 1046 pix - 728k] Caption : ESO PR Photo 22a/00 shows a colour composite of some of the first astronomical exposures obtained by YEPUN . The object is the planetary nebula Hen 2-428 that is located at a distance of 6,000-8,000 light-years and seen in a dense sky field, only 2° from the main plane of the Milky Way. As other planetary nebulae, it is caused by a dying star (the bluish object at the centre) that shreds its outer layers. The image is based on exposures through three optical filtres: B(lue) (10 min exposure, seeing 0.9 arcsec; here rendered as blue), V(isual) (5 min; 0.9 arcsec; green) and R(ed) (3 min; 0.9 arcsec; red). The field measures 88 x 78 arcsec 2 (1 pixel = 0.09 arcsec). North is to the lower right and East is to the lower left. The 5-day old Moon was about 90° away in the sky that was accordingly bright. The zenith angle was 44°. The ESO staff then proceeded to take a series of three photos with longer exposures through three different optical filtres. They have been combined to produce the image shown in ESO PR Photo 22a/00 . More astronomical images were obtained in sequence, first of the dwarf galaxy NGC 6822 in the Local Group (see PR Photo 22f/00 below) and then of the spiral galaxy NGC 7793 . All 8.2-m telescopes now in operation at Paranal The ESO Director General, Catherine Cesarsky , who was present on Paranal during this event, congratulated the ESO staff to the great achievement, herewith bringing a major phase of the VLT project to a successful end. She was particularly impressed by the excellent optical quality that was achieved at this early moment of the commissioning tests. A measurement showed that already now, 80% of the light is concentrated within 0.22 arcsec. The manager of the VLT project, Massimo Tarenghi , was very happy to reach this crucial project milestone, after nearly fifteen years of hard work. He also remarked that with the M2 mirror already now "in the active optics loop", the telescope was correctly compensating for the somewhat mediocre atmospheric conditions on this night. The next major step will be the "first light" for the VLT Interferometer (VLTI) , when the light from two Unit Telescopes is combined. This event is expected in the middle of next year. Impressions from the YEPUN "First Light" event First Light for YEPUN - ESO PR VC 06/00 ESO PR Video Clip 06/00 "First Light for YEPUN" (5650 frames/3:46 min) [MPEG Video+Audio; 160x120 pix; 7.7Mb] [MPEG Video+Audio; 320x240 pix; 25.7 Mb] [RealMedia; streaming; 34kps] [RealMedia; streaming; 200kps] ESO Video Clip 06/00 shows sequences from the Control Room at the Paranal Observatory, recorded with a fixed TV-camera in the evening of September 3 at about 23:00 hrs local time (03:00 UT), i.e., soon after the moment of "First Light" for YEPUN . The video sequences were transmitted via ESO's dedicated satellite communication link to the Headquarters in Garching for production of the clip. It begins at the moment a guide star is acquired to perform an automatic "active optics" correction of the mirrors; the associated explanation is given by Massimo Tarenghi (VLT Project Manager). The first astronomical observation is performed and the first image of the planetary nebula Hen 2-428 is discussed by the ESO Director General, Catherine Cesarsky . The next image, of the nearby dwarf galaxy NGC 6822 , arrives and is shown and commented on by the ESO Director General. Finally, Massimo Tarenghi talks about the next major step of the VLT Project. The combination of the lightbeams from two 8.2-m Unit Telescopes, planned for the summer of 2001, will mark the beginning of the VLT Interferometer. ESO Press Photo 22b/00 ESO Press Photo 22b/00 [Preview; JPEG: 400 x 300; 88k] [Full size; JPEG: 1600 x 1200; 408k] The enclosure for the fourth VLT 8.2-m Unit Telescope, YEPUN , photographed at sunset on September 3, 2000, immediately before "First Light" was successfully achieved. The upper part of the mostly subterranean Interferometric Laboratory for the VLTI is seen in front. (Digital Photo). ESO Press Photo 22c/00 ESO Press Photo 22c/00 [Preview; JPEG: 400 x 300; 112k] [Full size; JPEG: 1280 x 960; 184k] The initial tuning of the YEPUN optical system took place in the early evening of September 3, 2000, from the "observing hut" on the floor of the telescope enclosure. From left to right: Krister Wirenstrand who is responsible for the VLT Control Software, Jason Spyromilio - Head of the Commissioning Team, and Massimo Tarenghi , VLT Manager. (Digital Photo). ESO Press Photo 22d/00 ESO Press Photo 22d/00 [Preview; JPEG: 400 x 300; 112k] [Full size; JPEG: 1280 x 960; 184k] "Mission Accomplished" - The ESO Director General, Catherine Cesarsky , and the Paranal Director, Roberto Gilmozzi , face the VLT Manager, Massimo Tarenghi at the YEPUN Control Station, right after successful "First Light" for this telescope. (Digital Photo). An aerial image of YEPUN in its enclosure is available as ESO PR Photo 43a/99. The mechanical structure of YEPUN was first pre-assembled at the Ansaldo factory in Milan (Italy) where it served for tests while the other telescopes were erected at Paranal. An early photo ( ESO PR Photo 37/95 ) is available that was obtained during the visit of the ESO Council to Milan in December 1995, cf. ESO PR 18/95. Paranal at sunset ESO Press Photo 22e/00 ESO Press Photo 22e/00 [Preview; JPEG: 400 x 200; 14kb] [Normal; JPEG: 800 x 400; 84kb] [High-Res; JPEG: 4000 x 2000; 4.0Mb] Wide-angle view of the Paranal Observatory at sunset. The last rays of the sun illuminate the telescope enclosures at the top of the mountain and some of the buildings at the Base Camp. The new "residencia" that will provide living space for the Paranal staff and visitors from next year is being constructed to the left. The "First Light" observations with YEPUN began soon after sunset. This photo was obtained in March 2000. Additional photos (September 6, 2000) ESO PR Photo 22f/00 ESO PR Photo 22f/00 [Preview - JPEG: 400 x 487 pix - 224k] [Normal - JPEG: 992 x 1208 pix - 1.3Mb] Caption : ESO PR Photo 22f/00 shows a colour composite of three exposures of a field in the dwarf galaxy NGC 6822 , a member of the Local Group of Galaxies at a distance of about 2 million light-years. They were obtained by YEPUN and the VLT Test Camera at about 23:00 hrs local time on September 3 (03:00 UT on September 4), 2000. The image is based on exposures through three optical filtres: B(lue) (10 min exposure; here rendered as blue), V(isual) (5 min; green) and R(ed) (5 min; red); the seeing was 0.9 - 1.0 arcsec. Individual stars of many different colours (temperatures) are seen. The field measures about 1.5 x 1.5 arcmin 2. Another image of this galaxy was obtained earlier with ANTU and FORS1 , cf. PR Photo 10b/99. ESO Press Photo 22g/00 ESO Press Photo 22g/00 [Preview; JPEG: 400 x 300; 136k] [Full size; JPEG: 1280 x 960; 224k] Most of the crew that put together YEPUN is here photographed after the installation of the M1 mirror cell at the bottom of the mechanical structure (on July 30, 2000). Back row (left to right): Erich Bugueno (Mechanical Supervisor), Erito Flores (Maintenance Technician); front row (left to right) Peter Gray (Mechanical Engineer), German Ehrenfeld (Mechanical Engineer), Mario Tapia (Mechanical Engineer), Christian Juica (kneeling - Mechanical Technician), Nelson Montano (Maintenance Engineer), Hansel Sepulveda (Mechanical Technican) and Roberto Tamai (Mechanical Engineer). (Digital Photo). ESO PR Photos may be reproduced, if credit is given to the European Southern Observatory. The ESO PR Video Clips service to visitors to the ESO website provides "animated" illustrations of the ongoing work and events at the European Southern Observatory. The most recent clip was: ESO PR Video Clip 05/00 ("Portugal to Accede to ESO (27 June 2000). Information is also available on the web about other ESO videos.

Mood and audience effects on video lottery terminal gambling.

PubMed

Mishra, Sandeep; Morgan, Michael; Lalumière, Martin L; Williams, Robert J

2010-09-01

Little is known about the situational factors associated with gambling behavior. We induced 180 male participants (mean age: 21.6) into a positive, negative, or neutral mood prior to gambling on a video lottery terminal (VLT). While gambling, participants were observed by either a male peer, female peer, or no one. Induced mood had no effect on gambling behavior. Participants induced into a negative mood prior to gambling, however, reported more positive moods after gambling, whereas those with positive and neutral moods reported more negative moods after gambling. Participants observed by either a male or female peer spent less time gambling on the VLT compared to those not observed. Participants observed by a female peer lost less money relative to the other observer conditions. Degree of problem gambling in the last year had little influence on these effects. Some practical implications of these findings are discussed.

VLT/SPHERE- and ALMA-based shape reconstruction of asteroid (3) Juno

NASA Astrophysics Data System (ADS)

Viikinkoski, M.; Kaasalainen, M.; Ďurech, J.; Carry, B.; Marsset, M.; Fusco, T.; Dumas, C.; Merline, W. J.; Yang, B.; Berthier, J.; Kervella, P.; Vernazza, P.

2015-09-01

We use the recently released Atacama Large Millimeter Array (ALMA) and VLT/SPHERE science verification data, together with earlier adaptive-optics images, stellar occultation, and lightcurve data to model the 3D shape and spin of the large asteroid (3) Juno with the all-data asteroid modelling (ADAM) procedure. These data set limits on the plausible range of shape models, yielding reconstructions suggesting that, despite its large size, Juno has sizable unrounded features moulded by non-gravitational processes such as impacts. Based on observations collected at the European Southern Observatory, Paranal, Chile (prog. ID: 60.A-9379, 086.C-0785), and at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

PRIMA: study for a dual-beam instrument for the VLT Interferometer

NASA Astrophysics Data System (ADS)

Quirrenbach, Andreas; Coudé du Foresto, Vincent; Daigne, Gerard; Hofmann, Karl H.; Hofmann, Reiner; Lattanzi, Mario; Osterbart, R.; Le Poole, Rudolf S.; Queloz, Didier; Vakili, Farrokh

1998-07-01

PRIMA is a conceptual study for a single-baseline dual-feed instrument for the very large telescope interferometer, which is under construction by the European Southern Observatory on Cerro Paranal in Chile. The goals of PRIMA include narrow-angle astrometry with a precision of 10 (mu) as over an arc of 10 inches, and imaging of faint sources with the full sensitivity of the 8m telescopes in the VLT array. Key scientific programs that can be carried out with PRIMA in imaging mode include observations of active galactic nuclei, the Galactic Center, stars, and circumstellar matter. Scientific drivers for the astrometry are searches for planets and low-mass stellar companions, binary stars, dynamics of clusters, and parallaxes. We list the main performance requirements for PRIMA, present system architectures for the dual-beam system, and discuss limitations of the interferometric field-of-view.

VizieR Online Data Catalog: Massive stars in 30 Dor (Schneider+, 2018)

NASA Astrophysics Data System (ADS)

Schneider, F. R. N.; Sana, H.; Evans, C. J.; Bestenlehner, J. M.; Castro, N.; Fossati, L.; Grafener, G.; Langer, N.; Ramirez-Agudelo, O. H.; Sabin-Sanjulian, C.; Simon-Diaz, S.; Tramper, F.; Crowther, P. A.; de Koter, A.; de Mink, S. E.; Dufton, P. L.; Garcia, M.; Gieles, M.; Henault-Brunet, V.; Herrero, A.; Izzard, R. G.; Kalari, V.; Lennon, D. J.; Apellaniz, J. M.; Markova, N.; Najarro, F.; Podsiadlowski, P.; Puls, J.; Taylor, W. D.; van Loon, J. T.; Vink, J. S.; Norman, C.

2018-02-01

Through the use of the Fibre Large Array Multi Element Spectrograph (FLAMES) on the Very Large Telescope (VLT), the VLT-FLAMES Tarantula Survey (VFTS) has obtained optical spectra of ~800 massive stars in 30 Dor, avoiding the core region of the dense star cluster R136 because of difficulties with crowding. Repeated observations at multiple epochs allow determination of the orbital motion of potentially binary objects. For a sample of 452 apparently single stars, robust stellar parameters-such as effective temperatures, luminosities, surface gravities, and projected rotational velocities-are determined by modeling the observed spectra. Composite spectra of visual multiple systems and spectroscopic binaries are not considered here because their parameters cannot be reliably inferred from the VFTS data. To match the derived atmospheric parameters of the apparently single VFTS stars to stellar evolutionary models, we use the Bayesian code Bonnsai. (2 data files).

Active Optics: stress polishing of toric mirrors for the VLT SPHERE adaptive optics system.

PubMed

Hugot, Emmanuel; Ferrari, Marc; El Hadi, Kacem; Vola, Pascal; Gimenez, Jean Luc; Lemaitre, Gérard R; Rabou, Patrick; Dohlen, Kjetil; Puget, Pascal; Beuzit, Jean Luc; Hubin, Norbert

2009-05-20

The manufacturing of toric mirrors for the Very Large Telescope-Spectro-Polarimetric High-Contrast Exoplanet Research instrument (SPHERE) is based on Active Optics and stress polishing. This figuring technique allows minimizing mid and high spatial frequency errors on an aspherical surface by using spherical polishing with full size tools. In order to reach the tight precision required, the manufacturing error budget is described to optimize each parameter. Analytical calculations based on elasticity theory and finite element analysis lead to the mechanical design of the Zerodur blank to be warped during the stress polishing phase. Results on the larger (366 mm diameter) toric mirror are evaluated by interferometry. We obtain, as expected, a toric surface within specification at low, middle, and high spatial frequencies ranges.

VizieR Online Data Catalog: COSMOS field variability-selected AGN nuclei (De Cicco+, 2015)

NASA Astrophysics Data System (ADS)

de Cicco, D.; Paolillo, M.; Covone, G.; Falocco, S.; Longo, G.; Grado, A.; Limatola, L.; Botticella, M. T.; Pignata, G.; Cappellaro, E.; Vaccari, M.; Trevese, D.; Vagnetti, F.; Salvato, M.; Radovich, M.; Brandt, W. N.; Capaccioli, M.; Napolitano, N. R.; Schipani, P.

2015-03-01

The VLT Survey Telescope (VST) is located at Cerro Paranal Observatory; it is a joint venture between the European Southern Observatory (ESO) and the INAF-Osservatorio Astronomico di Capodimonte (OAC) in Napoli. The telescope is 2.65m in diameter and is equipped with the single focal plane detector OmegaCAM: a mosaic of 32 CCD detectors made up of 268 megapixels in total, corresponding to a 26cmx26cm area and a 1°x1° FoV, the resolution being 0.214"/pixel. The VST is dedicated to surveys in the wavelength range 0.3-1.0um. The survey provides data in the g, r, and i bands, with an observing frequency of approximately ten days for the g and i bands and three days for the r band, depending on the various observational constraints. We discuss here the analysis of 28 epochs in the r band, for which we have the best temporal sampling. The observations cover the period from December 2011 to May 2012. (1 data file).

Astronomical Optical Interferometry. I. Methods and Instrumentation

NASA Astrophysics Data System (ADS)

Jankov, S.

2010-12-01

Previous decade has seen an achievement of large interferometric projects including 8-10m telescopes and 100m class baselines. Modern computer and control technology has enabled the interferometric combination of light from separate telescopes also in the visible and infrared regimes. Imaging with milli-arcsecond (mas) resolution and astrometry with micro-arcsecond (muas) precision have thus become reality. Here, I review the methods and instrumentation corresponding to the current state in the field of astronomical optical interferometry. First, this review summarizes the development from the pioneering works of Fizeau and Michelson. Next, the fundamental observables are described, followed by the discussion of the basic design principles of modern interferometers. The basic interferometric techniques such as speckle and aperture masking interferometry, aperture synthesis and nulling interferometry are disscused as well. Using the experience of past and existing facilities to illustrate important points, I consider particularly the new generation of large interferometers that has been recently commissioned (most notably, the CHARA, Keck, VLT and LBT Interferometers). Finally, I discuss the longer-term future of optical interferometry, including the possibilities of new large-scale ground-based projects and prospects for space interferometry.

Galaxy Mass Assembly with VLT & HST and lessons for E-ELT/MOSAIC

NASA Astrophysics Data System (ADS)

Hammer, François; Flores, Hector; Puech, Mathieu

2015-02-01

The fraction of distant disks and mergers is still debated, while 3D-spectroscopy is revolutionizing the field. However its limited spatial resolution imposes a complimentary HST imagery and a robust analysis procedure. When applied to observations of IMAGES galaxies at z = 0.4-0.8, it reveals that half of the spiral progenitors were in a merger phase, 6 billion year ago. The excellent correspondence between methodologically-based classifications of morphologies and kinematics definitively probes a violent origin of disk galaxies as proposed by Hammer et al. (2005). Examination of nearby galaxy outskirts reveals fossil imprints of such ancient merger events, under the form of well organized stellar streams. Perhaps our neighbor, M31, is the best illustration of an ancient merger, which modeling in 2010 leads to predict the gigantic plane of satellites discovered by Ibata et al. (2013). There are still a lot of discoveries to be done until the ELT era, which will open an avenue for detailed and accurate 3D-spectroscopy of galaxies from the earliest epochs to the present.

X-shooter Finds an Extremely Primitive Star

NASA Astrophysics Data System (ADS)

Caffau, E.; Bonifacio, P.; François, P.; Sbordone, L.; Monaco, L.; Spite, M.; Spite, F.; Ludwig, H.-G.; Cayrel, R.; Zaggia, S.; Hammer, F.; Randich, S.; Molaro, P.; Hill, V.

2011-12-01

Low-mass extremely metal-poor (EMP) stars hold the fossil record of the chemical composition of the early phases of the Universe in their atmospheres. Chemical analysis of such objects provides important constraints on these early phases. EMP stars are rather rare objects: to dig them out, large amounts of data have to be considered. We have analysed stars from the Sloan Digital Sky Survey using an automatic procedure and selected a sample of good candidate EMP stars, which we observed with the spectrographs X-shooter and UVES. We could confirm the low metallicity of our sample of stars, and we succeeded in finding a record metal-poor star.

The SpeX Prism Library Analysis Toolkit: Design Considerations and First Results

NASA Astrophysics Data System (ADS)

Burgasser, Adam J.; Aganze, Christian; Escala, Ivana; Lopez, Mike; Choban, Caleb; Jin, Yuhui; Iyer, Aishwarya; Tallis, Melisa; Suarez, Adrian; Sahi, Maitrayee

2016-01-01

Various observational and theoretical spectral libraries now exist for galaxies, stars, planets and other objects, which have proven useful for classification, interpretation, simulation and model development. Effective use of these libraries relies on analysis tools, which are often left to users to develop. In this poster, we describe a program to develop a combined spectral data repository and Python-based analysis toolkit for low-resolution spectra of very low mass dwarfs (late M, L and T dwarfs), which enables visualization, spectral index analysis, classification, atmosphere model comparison, and binary modeling for nearly 2000 library spectra and user-submitted data. The SpeX Prism Library Analysis Toolkit (SPLAT) is being constructed as a collaborative, student-centered, learning-through-research model with high school, undergraduate and graduate students and regional science teachers, who populate the database and build the analysis tools through quarterly challenge exercises and summer research projects. In this poster, I describe the design considerations of the toolkit, its current status and development plan, and report the first published results led by undergraduate students. The combined data and analysis tools are ideal for characterizing cool stellar and exoplanetary atmospheres (including direct exoplanetary spectra observations by Gemini/GPI, VLT/SPHERE, and JWST), and the toolkit design can be readily adapted for other spectral datasets as well.This material is based upon work supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G. SPLAT code can be found at https://github.com/aburgasser/splat.

The 4MOST facility control software

NASA Astrophysics Data System (ADS)

Pramskiy, Alexander; Mandel, Holger; Rothmaier, Florian; Stilz, Ingo; Winkler, Roland; Hahn, Thomas

2016-07-01

The 4-m Multi-Object Spectrographic Telescope (4MOST) is one high-resolution (R 18000) and two lowresolution (R fi 5000) spectrographs covering the wavelength range between 390 and 950 nm. The spectrographs will be installed on ESO VISTA telescope and will be fed by approximately 2400 fibres. The instrument is capable to simultaneously obtain spectra of about 2400 objects distributed over an hexagonal field-of-view of four square degrees. This paper aims at giving an overview of the control software design, which is based on the standard ESO VLT software architecture and customised to fit the needs of the 4MOST instrument. In particular, the facility control software is intended to arrange the precise positioning of the fibres, to schedule and observe many surveys in parallel, and to combine the output from the three spectrographs. Moreover, 4MOST's software will include user-friendly graphical user interfaces that enable users to interact with the facility control system and to monitor all data-taking and calibration tasks of the instrument. A secondary guiding system will be implemented to correct for any fibre exure and thus to improve 4MOST's guiding performance. The large amount of fibres requires the custom design of data exchange to avoid performance issues. The observation sequences are designed to use spectrographs in parallel with synchronous points for data exchange between subsystems. In order to control hardware devices, Programmable Logic Controller (PLC) components will be used, the new standard for future instruments at ESO.

Ultraluminous Infrared Mergers: Elliptical Galaxies in Formation?

NASA Astrophysics Data System (ADS)

Genzel, R.; Tacconi, L. J.; Rigopoulou, D.; Lutz, D.; Tecza, M.

2001-12-01

We report high-quality near-IR spectroscopy of 12 ultraluminous infrared galaxy mergers (ULIRGs). Our new VLT and Keck data provide ~0.5" resolution, stellar and gas kinematics of these galaxies, most of which are compact systems in the last merger stages. We confirm that ULIRG mergers are ``ellipticals in formation.'' Random motions dominate their stellar dynamics, but significant rotation is common. Gasdynamics and stellar dynamics are decoupled in most systems. ULIRGs fall on or near the fundamental plane of hot stellar systems, and especially on its less evolution-sensitive, reff-σ projection. The ULIRG velocity dispersion distribution, their location in the fundamental plane, and their distribution of vrotsini/σ closely resemble those of intermediate-mass (~L*), elliptical galaxies with moderate rotation. As a group ULIRGs do not resemble giant ellipticals with large cores and little rotation. Our results are in good agreement with other recent studies indicating that disky ellipticals with compact cores or cusps can form through dissipative mergers of gas-rich disk galaxies while giant ellipticals with large cores have a different formation history. Based on observations at the European Southern Observatory, Chile (ESO 65.N-0266, 65.N-0289), and on observations at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, The University of California, and the National Aeronautics and Space Administration. The Keck Observatory was made possible by the general financial support by the W. M. Keck Foundation.

The VLT LBG redshift survey - VI. Mapping H I in the proximity of z ˜ 3 LBGs with X-Shooter

NASA Astrophysics Data System (ADS)

Bielby, R. M.; Shanks, T.; Crighton, N. H. M.; Bornancini, C. G.; Infante, L.; Lambas, D. G.; Minniti, D.; Morris, S. L.; Tummuangpak, P.

2017-10-01

We present an analysis of the spatial distribution and dynamics of neutral hydrogen gas around galaxies using new X-Shooter observations of z ˜ 2.5-4 quasars. Adding the X-Shooter data to our existing data set of high-resolution quasar spectroscopy, we use a total sample of 29 quasars alongside ˜1700 Lyman Break Galaxies (LBGs) in the redshift range 2 ≲ z ≲ 3.5. We measure the Lyα forest auto-correlation function, finding a clustering length of s0 = 0.081 ± 0.006 h-1 Mpc, and the cross-correlation function with LBGs, finding a cross-clustering length of s0 = 0.27 ± 0.14 h-1 Mpc and power-law slope γ = 1.1 ± 0.2. Our results highlight the weakly clustered nature of neutral hydrogren systems in the Lyα forest. Building on this, we make a first analysis of the dependence of the clustering on absorber strength, finding a clear preference for stronger Lyα forest absorption features to be more strongly clustered around the galaxy population, suggesting that they trace on average higher mass haloes. Using the projected and 2-D cross-correlation functions, we constrain the dynamics of Lyα forest clouds around z ˜ 3 galaxies. We find a significant detection of large-scale infall of neutral hydrogen, with a constraint on the Lyα forest infall parameter of βF = 1.02 ± 0.22.

Supervised detection of exoplanets in high-contrast imaging sequences

NASA Astrophysics Data System (ADS)

Gomez Gonzalez, C. A.; Absil, O.; Van Droogenbroeck, M.

2018-06-01

Context. Post-processing algorithms play a key role in pushing the detection limits of high-contrast imaging (HCI) instruments. State-of-the-art image processing approaches for HCI enable the production of science-ready images relying on unsupervised learning techniques, such as low-rank approximations, for generating a model point spread function (PSF) and subtracting the residual starlight and speckle noise. Aims: In order to maximize the detection rate of HCI instruments and survey campaigns, advanced algorithms with higher sensitivities to faint companions are needed, especially for the speckle-dominated innermost region of the images. Methods: We propose a reformulation of the exoplanet detection task (for ADI sequences) that builds on well-established machine learning techniques to take HCI post-processing from an unsupervised to a supervised learning context. In this new framework, we present algorithmic solutions using two different discriminative models: SODIRF (random forests) and SODINN (neural networks). We test these algorithms on real ADI datasets from VLT/NACO and VLT/SPHERE HCI instruments. We then assess their performances by injecting fake companions and using receiver operating characteristic analysis. This is done in comparison with state-of-the-art ADI algorithms, such as ADI principal component analysis (ADI-PCA). Results: This study shows the improved sensitivity versus specificity trade-off of the proposed supervised detection approach. At the diffraction limit, SODINN improves the true positive rate by a factor ranging from 2 to 10 (depending on the dataset and angular separation) with respect to ADI-PCA when working at the same false-positive level. Conclusions: The proposed supervised detection framework outperforms state-of-the-art techniques in the task of discriminating planet signal from speckles. In addition, it offers the possibility of re-processing existing HCI databases to maximize their scientific return and potentially improve the demographics of directly imaged exoplanets.

The water vapour radiometer of Paranal: homogeneity of precipitable water vapour from two years of operations

NASA Astrophysics Data System (ADS)

Kerber, Florian; Querel, Richard R.; Neureiter, Bianca

2015-04-01

A Low Humidity and Temperature Profiling (LHATPRO) microwave radiometer, manufactured by Radiometer Physics GmbH (RPG), is used to monitor sky conditions over ESO's Paranal observatory in support of VLT science operations. The unit measures several channels across the strong water vapour emission line at 183 GHz, necessary for resolving the low levels of precipitable water vapour (PWV) that are prevalent on Paranal (median ∼2.4 mm). The instrument consists of a humidity profiler (183-191 GHz), a temperature profiler (51-58 GHz), and an infrared camera (∼10 μm) for cloud detection. We present a statistical analysis of the homogeneity of all-sky PWV using 24 months of PWV observations. The question we tried to address was whether PWV is homogeneous enough across the sky such that service mode observations with the VLT can routinely be conducted with a user-provided constraint for PWV measured at zenith. We find the PWV over Paranal to be remarkably homogeneous across the sky down to 27.5° elevation with a median variation of 0.07 mm (rms). The homogeneity is a function of the absolute PWV but the relative variation is fairly constant at 2 to 3% (rms). Such variations will not be a significant issue for analysis of astronomical data. Users at ESO can specify PWV - measured at zenith - as an ambient constraint in service mode to enable, for instance, very demanding observations in the infrared. We conclude that in general it will not be necessary to add another observing constraint for PWV homogeneity to ensure integrity of observations. For demanding observations requiring very low PWV, where the relative variation is higher, the optimum support could be provided by observing with the LHATPRO in the same line-of-sight simultaneously. Such a mode of operations has already been tested but will have to be justified in terms of scientific gain before implementation can be considered. We plan to extend our analysis of PWV variations covering a larger parameters space for temporal and spatial resolution in the future. Also for climate studies such data sets will be relevant.

The flared inner disk of the Herbig Ae star AB Aurigae revealed by VLTI/MIDI in the N-band

NASA Astrophysics Data System (ADS)

di Folco, E.; Dutrey, A.; Chesneau, O.; Wolf, S.; Schegerer, A.; Leinert, Ch.; Lopez, B.

2009-06-01

Aims: We aim at using the long baselines of the VLT Interferometer and the mid-IR combiner MIDI (8-13 μm) to derive the morphology of the protoplanetary disk surrounding the Herbig Ae star AB Aurigae Methods: We present the first N-band analysis of AB Aur performed with a maximum angular resolution of 17 mas (2.5 AU at the Taurus-Auriga distance). We used the radiative transfer code MC3D and a silicate-dominated dust grain mixture to fit the spectral energy distribution (SED), together with the N-band dispersed visibilities (λ / δλ ~ 30) and to constrain the inner-disk spatial structure. Results: The silicate band is prominent in the ~ 300 mas FOV of the MIDI instrument, the emission reaches 70 to 90% of the total flux measured by ISO. The circumstellar emission (CSE) is resolved even at the shortest baselines. The spectrally dispersed visibilities show a steep drop between 8 and 9.5 μm, followed by a plateau between 10 and 13 μm. Our modelling shows that the observed SED and visibilities can be reproduced with a simple passive disk model. For such a weakly inclined disk (i ~ 30 deg), the mid-IR visibilities can directly determine the flaring index, while the scale height can be subsequently and unambiguously derived from the combination of the spectral and interferometric constraints. The modelling yields typical values for the scale height of about 8 AU at a radial distance of 100 AU and a flaring index in the range 1.25-1.30 for the explored range of model input parameters. Conclusions: The radial structure of the circumstellar inner disk around AB Aur is directly determined by MIDI. The radiative transfer modelling demonstrates the powerful synergy of interferometry and spectro-photometry to alleviate the degeneracy, which may hamper determining the disk morphology. Our analysis supports the classification of AB Aur among the flared disks of the first group in the Meeus classification. Based on observations collected at ESO (Paranal Observatory) with the VLT Interferometer - Prog ID: 074.C-552 & 076.C-252.

Binary energy source of the HH 250 outflow and its circumstellar environment

NASA Astrophysics Data System (ADS)

Comerón, Fernando; Reipurth, Bo; Yen, Hsi-Wei; Connelley, Michael S.

2018-04-01

Aims: Herbig-Haro flows are signposts of recent major accretion and outflow episodes. We aim to determine the nature and properties of the little-known outflow source HH 250-IRS, which is embedded in the Aquila clouds. Methods: We have obtained adaptive optics-assisted L-band images with the NACO instrument on the Very Large Telescope (VLT), together with N- and Q-band imaging with VISIR also on the VLT. Using the SINFONI instrument on the VLT we carried out H- and K-band integral field spectroscopy of HH 250-IRS, complemented with spectra obtained with the SpeX instrument at the InfraRed Telescope Facility (IRTF) in the JHKL bands. Finally, the SubMillimeter Array (SMA) interferometer was used to study the circumstellar environment of HH 250-IRS at 225 and 351 GHz with CO (2-1) and CO (3-2) maps and 0.9 mm and 1.3 mm continuum images. Results: The HH 250-IRS source is resolved into a binary with 0.''53 separation, corresponding to 120 AU at the adopted distance of 225 pc. The individual components show heavily veiled spectra with weak CO absorption indicative of late-type stars. Both are Class I sources, but their spectral energy distributions between 1.5 μm and 19 μm differ markedly and suggest the existence of a large cavity around one of the components. The millimeter interferometric observations indicate that the gas mainly traces a circumbinary envelope or disk, while the dust emission is dominated by one of the circumstellar envelopes. Conclusions: HH 250-IRS is a new addition to the handful of multiple systems where the individual stellar components, the circumstellar disks and a circumbinary disk can be studied in detail, and a rare case among those systems in which a Herbig-Haro flow is present. Based on observations obtained with the VLT (Cerro Paranal, Chile) in programs 089.C-0196(A), 095.C-0488(A), and 095.C-0488(B), as well as with IRTF (Mauna Kea, Hawaii), SMA (Mauna Kea, Hawaii), and the Nordic Optical Telescope (La Palma, Canary Islands, Spain).Staff Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration.

Portugal to Accede to ESO

NASA Astrophysics Data System (ADS)

2000-06-01

The Republic of Portugal will become the ninth member state of the European Southern Observatory (ESO) [1]. Today, during a ceremony at the ESO Headquarters in Garching (Germany), a corresponding Agreement was signed by the Portuguese Minister of Science and Technology, José Mariano Gago and the ESO Director General, Catherine Cesarsky , in the presence of other high officials from Portugal and the ESO member states (see Video Clip 05/00 below). Following subsequent ratification by the Portuguese Parliament of the ESO Convention and the associated protocols [2], it is foreseen that Portugal will formally join this organisation on January 1, 2001. Uniting European Astronomy ESO PR Photo 16/00 ESO PR Photo 16/00 [Preview - JPEG: 400 x 405 pix - 160k] [Normal - JPEG: 800 x 809 pix - 408k] Caption : Signing of the Portugal-ESO Agreement on June 27, 2000, at the ESO Headquarters in Garching (Germany). At the table, the ESO Director General, Catherine Cesarsky , and the Portuguese Minister of Science and Technology, José Mariano Gago . In his speech, the Portuguese Minister of Science and Technology, José Mariano Gago , stated that "the accession of Portugal to ESO is the result of a joint effort by ESO and Portugal during the last ten years. It was made possible by the rapid Portuguese scientific development and by the growth and internationalisation of its scientific community." He continued: "Portugal is fully committed to European scientific and technological development. We will devote our best efforts to the success of ESO". Catherine Cesarsky , ESO Director General since 1999, warmly welcomed the Portuguese intention to join ESO. "With the accession of their country to ESO, Portuguese astronomers will have great opportunities for working on research programmes at the frontiers of modern astrophysics." "This is indeed a good time to join ESO", she added. "The four 8.2-m VLT Unit Telescopes with their many first-class instruments are nearly ready, and the VLT Interferometer will soon follow. With a decision about the intercontinental millimetre-band ALMA project expected next year and the first concept studies for gigantic optical/infrared telescopes like OWL now well under way at ESO, there is certainly no lack of perspectives, also for coming generations of European astronomers!" Portuguese astronomy: a decade of progress The beginnings of the collaboration between Portugal and ESO, now culminating in the imminent accession of that country to the European research organisation, were almost exactly ten years ago. On July 10, 1990, the Republic of Portugal and ESO signed a Co-operation Agreement , aimed at full Portuguese membership of the ESO organisation within the next decade. During the interim period, Portuguese astronomers were granted access to ESO facilities while the Portuguese government would provide support towards the development of astronomy and the associated infrastructure in this country. A joint Portuguese/ESO Advisory Body was set up to monitor the development of Portuguese astronomy and its interaction with ESO. Over the years, an increasing number of measures to strengthen the Portuguese research infrastructure within astrophysics and related fields were proposed and funded. More and more, mostly young Portuguese astronomers began to make use of ESO's facilities at the La Silla observatory and recently, of the Very Large Telescope (VLT) at Paranal. Now, ten years later, the Portuguese astronomical community is the youngest in Europe with more than 90% of its PhD's awarded during the last eight years. As expected, the provisional access to ESO telescopes - especially the Very Large Telescope (VLT) with its suite of state-of-the-art instruments for observations at wavelengths ranging from the UV to the mid-infrared - has proven to be a great incentive to the Portuguese scientists. As a clear demonstration of these positive developments, a very successful Workshop entitled "Portugal - ESO - VLT" was held in Lisbon on April 17-18, 2000. It was primarily directed towards young Portuguese scientists and served to inform them about the ESO Very Large Telescope (VLT) and the steadily evolving, exciting research possibilities with this world-class facility. Notes [1]: Current ESO member countries are Belgium, Denmark, France, Germany, Italy, the Netherlands, Sweden and Switzerland. [2]: The ESO Convention was established in 1962 and specifies the goals of ESO and the means to achieve these, e.g., "The Governments of the States parties to this convention... desirous of jointly creating an observatory equipped with powerful instruments in the Southern hemisphere and accordingly promoting and organizing co-operation in astronomical research..." (from the Preamble to the ESO Convention). Video Clip from the Signing Ceremony

VizieR Online Data Catalog: NGC253 near-infrared H2 emission (Rosenberg+,

NASA Astrophysics Data System (ADS)

Rosenberg, M. J. F.; van der Werf, P. P.; Israel, F. P.

2012-11-01

All observations were made with SINFONI at the ESO VLT. We observed in the H, and K bands using a spatial pixel scale of 0.25" corresponding to a field of view of 8" by 8" per frame and a spectral resolution of 2000, 3000 and 4000 respectively, which corresponds to a velocity resolution of 149.8, 99.9 and 74.9km/s. All science observations were taken in the ABA'nodding mode (300s of object, 300s of sky, 300s of object), where A' is slightly offset from A. The object exposures are aligned and averaged during the reconstruction of the data cube. The observations of NGC 253 were made in visitor mode on August 28th, 2005. In order to capture the full extent of the H2 emission, consecutive frames were taken in the K band moving further away from the center, along the disk until H2 was no longer detected. This resulted in 6 separate pointings. Since there are also H2 transitions in the H band, a similar strategy was used, resulting in 4 separate pointings. We used the standard reduction techniques of the SINFONI pipeline on all observations, including corrections for flat field, dark current, nonlinearity of pixels, distortion, and wavelength calibration. We obtained the flux calibration and atmospheric corrections from observations of a standard star, namely HR 2058 in the H band and HD 20001 in the K band (2 data files).

VLT/X-Shooter spectroscopy of the afterglow of the Swift GRB 130606A. Chemical abundances and reionisation at z ~ 6

NASA Astrophysics Data System (ADS)

Hartoog, O. E.; Malesani, D.; Fynbo, J. P. U.; Goto, T.; Krühler, T.; Vreeswijk, P. M.; De Cia, A.; Xu, D.; Møller, P.; Covino, S.; D'Elia, V.; Flores, H.; Goldoni, P.; Hjorth, J.; Jakobsson, P.; Krogager, J.-K.; Kaper, L.; Ledoux, C.; Levan, A. J.; Milvang-Jensen, B.; Sollerman, J.; Sparre, M.; Tagliaferri, G.; Tanvir, N. R.; de Ugarte Postigo, A.; Vergani, S. D.; Wiersema, K.; Datson, J.; Salinas, R.; Mikkelsen, K.; Aghanim, N.

2015-08-01

Context. The reionisation of the Universe is a process that is thought to have ended around z ~ 6, as inferred from spectroscopy of distant bright background sources, such as quasars (QSO) and gamma-ray burst (GRB) afterglows. Furthermore, spectroscopy of a GRB afterglow provides insight in its host galaxy, which is often too dim and distant to study otherwise. Aims: For the Swift GRB 130606A at z = 5.913 we have obtained a high S/N spectrum covering the full optical and near-IR wavelength region at intermediate spectral resolution with VLT/X-Shooter. We aim to measure the degree of ionisation of the intergalactic medium (IGM) between z = 5.02-5.84 and to study the chemical abundance pattern and dust content of its host galaxy. Methods: We estimated the UV continuum of the GRB afterglow using a power-law extrapolation, then measured the flux decrement due to absorption at Lyα,β, and γ wavelength regions. Furthermore, we fitted the shape of the red damping wing of Lyα. The hydrogen and metal absorption lines formed in the host galaxy were fitted with Voigt profiles to obtain column densities. We investigated whether ionisation corrections needed to be applied. Results: Our measurements of the Lyα-forest optical depth are consistent with previous measurements of QSOs, but have a much smaller uncertainty. The analysis of the red damping wing yields a neutral fraction xH i< 0.05 (3σ). We obtain column density measurements of H, Al, Si, and Fe; for C, O, S and Ni we obtain limits. The ionisation due to the GRB is estimated to be negligible (corrections <0.03 dex), but larger corrections may apply due to the pre-existing radiation field (up to 0.4 dex based on sub-DLA studies). Assuming that [ Si/Fe ] = +0.79 ± 0.13 is due to dust depletion, the dust-to-metal ratio is similar to the Galactic value. Conclusions: Our measurements confirm that the Universe is already predominantly ionised over the redshift range probed in this work, but was slightly more neutral at z> 5.6. GRBs are useful probes of the ionisation state of the IGM in the early Universe, but because of internal scatter we need a larger statistical sample to draw robust conclusions. The high [Si/Fe] in the host can be due to dust depletion, α-element enhancement, or a combination of both. The very high value of [ Al/Fe ] = 2.40 ± 0.78 might be due to a proton capture process and is probably connected to the stellar population history. We estimate the host metallicity to be -1.7 < [ M/H ] < -0.9 (2%-13% of solar). Based on observations carried out under prog. ID 091.C-0934(C) with the X-Shooter spectrograph installed at the Cassegrain focus of the Very Large Telescope (VLT), Unit 2 - Kueyen, operated by the European Southern Observatory (ESO) on Cerro Paranal, Chile. Partly based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias. Partly based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias, under programme A26TAC_63.Appendix A is available in electronic form at http://www.aanda.orgThe reduced spectrum (FITS file) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A139

Star Formation Histories of z ∼ 1 Galaxies in LEGA-C

NASA Astrophysics Data System (ADS)

Chauke, Priscilla; van der Wel, Arjen; Pacifici, Camilla; Bezanson, Rachel; Wu, Po-Feng; Gallazzi, Anna; Noeske, Kai; Straatman, Caroline; Muños-Mateos, Juan-Carlos; Franx, Marijn; Barišić, Ivana; Bell, Eric F.; Brammer, Gabriel B.; Calhau, Joao; van Houdt, Josha; Labbé, Ivo; Maseda, Michael V.; Muzzin, Adam; Rix, Hans-Walter; Sobral, David

2018-07-01

Using high-resolution spectra from the VLT Large Early Galaxy Astrophysics Census (LEGA-C) program, we reconstruct the star formation histories (SFHs) of 607 galaxies at redshifts z = 0.6–1.0 and stellar masses ≳1010 M ⊙ using a custom full spectrum fitting algorithm that incorporates the emcee and FSPS packages. We show that the mass-weighted age of a galaxy correlates strongly with stellar velocity dispersion (σ *) and ongoing star formation (SF) activity, with the stellar content in higher-σ * galaxies having formed earlier and faster. The SFHs of quiescent galaxies are generally consistent with passive evolution since their main SF epoch, but a minority show clear evidence of a rejuvenation event in their recent past. The mean age of stars in galaxies that are star-forming is generally significantly younger, with SF peaking after z < 1.5 for almost all star-forming galaxies in the sample: many of these still have either constant or rising SFRs on timescales >100 Myr. This indicates that z > 2 progenitors of z ∼ 1 star-forming galaxies are generally far less massive. Finally, despite considerable variance in the individual SFHs, we show that the current SF activity of massive galaxies (>L *) at z ∼ 1 correlates with SF levels at least 3 Gyr prior: SFHs retain “memory” on a large fraction of the Hubble time. Our results illustrate a novel approach to resolve the formation phase of galaxies, and, by identifying their individual evolutionary paths, one can connect progenitors and descendants across cosmic time. This is uniquely enabled by the high-quality continuum spectroscopy provided by the LEGA-C survey.

Extragalactic background light: a measurement at 400 nm using dark cloud shadow*†- I. Low surface brightness spectrophotometry in the area of Lynds 1642

NASA Astrophysics Data System (ADS)

Mattila, K.; Lehtinen, K.; Väisänen, P.; von Appen-Schnur, G.; Leinert, Ch.

2017-09-01

We present the method and observations for the measurement of the Extragalactic Background Light (EBL) utilizing the shadowing effect of a dark cloud. We measure the surface brightness difference between the opaque cloud core and its unobscured surroundings. In the difference the large atmospheric and Zodiacal light components are eliminated and the only remaining foreground component is the scattered starlight from the cloud itself. Although much smaller, its separation is the key problem in the method. For its separation we use spectroscopy. While the scattered starlight has the characteristic Fraunhofer lines and 400 nm discontinuity, the EBL spectrum is smooth and without these features. Medium resolution spectrophotometry at λ = 380-580 nm was performed with VLT/FORS at ESO of the surface brightness in and around the high-galactic-latitude dark cloud Lynds 1642. Besides the spectrum for the core with AV ≳ 15 mag, further spectra were obtained for intermediate-opacity cloud positions. They are used as proxy for the spectrum of the impinging starlight spectrum and to facilitate the separation of the scattered starlight (cf. Paper II; Mattila et al.). Our spectra reach a precision of ≲ 0.5 × 10-9 erg cm-2 s-1 sr-1 Å-1 as required to measure an EBL intensity in range of ˜1 to a few times 10-9 erg cm-2 s-1 sr-1 Å-1. Because all surface brightness components are measured using the same equipment, the method does not require unusually high absolute calibration accuracy, a condition that has been a problem for some previous EBL projects.

Nebular line emission from z > 7 galaxies in a cosmological simulation: rest-frame UV to optical lines

NASA Astrophysics Data System (ADS)

Shimizu, Ikkoh; Inoue, Akio K.; Okamoto, Takashi; Yoshida, Naoki

2016-10-01

We have performed very large and high-resolution cosmological hydrodynamic simulations in order to investigate detectability of nebular lines in the rest-frame ultraviolet (UV) to optical wavelength range from galaxies at z > 7. We find that the expected line fluxes are very well correlated with the apparent UV magnitudes. The C IV 1549 Å and C III] 1909 Å lines of galaxies brighter than 26 AB magnitudes are detectable with current facilities such as the Very Large Telescope (VLT) XShooter and the Keck Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE). Metal lines such as C IV 1549 Å, C III] 1909 Å, [O II] 3727 Å and [O III] 4959/5007 Å are good targets for spectroscopic observation with the Thirty-Metre Telescope (TMT), European Extremely Large Telescope (E-ELT), Giant Magellan Telescope (GMT) and James Webb Space Telescope (JWST). We also expect Hα and Hβ lines to be detectable with these telescopes. Additionally, we predict the detectability of nebular lines for z > 10 galaxies, which will be found with JWST, the Wide-Field Infrared Survey Telescope (WFIRST) and First Light And Reionization Explorer (FLARE) (11 ≤ z ≤ 15). We conclude that the C IV 1549 Å, C III] 1909 Å, [O III] 4959/5007 Å and Hβ lines from even z ˜15 galaxies could be strong targets for TMT, E-ELT and JWST. We also find that magnification by gravitational lensing is of great help in detecting such high-z galaxies. According to our model, the C III] 1909 Å line in z > 9 galaxy candidates is detectable even using current facilities.

The nature of extreme emission line galaxies at z = 1-2: kinematics and metallicities from near-infrared spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maseda, Michael V.; Van der Wel, Arjen; Rix, Hans-Walter

2014-08-10

We present near-infrared spectroscopy of a sample of 22 Extreme Emission Line Galaxies at redshifts 1.3 < z < 2.3, confirming that these are low-mass (M{sub *} = 10{sup 8}-10{sup 9} M{sub ☉}) galaxies undergoing intense starburst episodes (M{sub *}/SFR ∼ 10-100 Myr). The sample is selected by [O III] or Hα emission line flux and equivalent width using near-infrared grism spectroscopy from the 3D-HST survey. High-resolution NIR spectroscopy is obtained with LBT/LUCI and VLT/X-SHOOTER. The [O III]/Hβ line ratio is high (≳ 5) and [N II]/Hα is always significantly below unity, which suggests a low gas-phase metallicity. We aremore » able to determine gas-phase metallicities for seven of our objects using various strong-line methods, with values in the range 0.05-0.30 Z{sub ☉} and with a median of 0.15 Z{sub ☉}; for three of these objects we detect [O III] λ4363, which allows for a direct constraint on the metallicity. The velocity dispersion, as measured from the nebular emission lines, is typically ∼50 km s{sup –1}. Combined with the observed star-forming activity, the Jeans and Toomre stability criteria imply that the gas fraction must be large (f{sub gas} ≳ 2/3), consistent with the difference between our dynamical and stellar mass estimates. The implied gas depletion timescale (several hundred Myr) is substantially longer than the inferred mass-weighted ages (∼50 Myr), which further supports the emerging picture that most stars in low-mass galaxies form in short, intense bursts of star formation.« less

Characterization of the Infrared/X-ray sub-second variability for the black-hole transient GX 339-4

NASA Astrophysics Data System (ADS)

Vincentelli, F. M.; Casella, P.; Maccarone, T. J.; Uttley, P.; Gandhi, P.; Belloni, T.; De Marco, B.; Russell, D. M.; Stella, L.; O'Brien, K.

2018-03-01

We present a detailed analysis of the X-ray/IR fast variability of the Black-Hole Transient GX 339-4 during its low/hard state in August 2008. Thanks to simultaneous high time-resolution observations made with the VLT and RXTE, we performed the first characterisation of the sub-second variability in the near-infrared band - and of its correlation with the X-rays - for a low-mass X-ray binary, using both time- and frequency-domain techniques. We found a power-law correlation between the X-ray and infrared fluxes when measured on timescales of 16 seconds, with a marginally variable slope, steeper than the one found on timescales of days at similar flux levels. We suggest the variable slope - if confirmed - could be due to the infrared flux being a non-constant combination of both optically thin and optically thick synchrotron emission from the jet, as a result of a variable self-absorption break. From cross spectral analysis we found an approximately constant infrared time lag of ≈0.1s, and a very high coherence of ˜90 per cent on timescales of tens of seconds, slowly decreasing toward higher frequencies. Finally, we report on the first detection of a linear rms-flux relation in the emission from a low-mass X-ray binary jet, on timescales where little correlation is found between the X-rays and the jet emission itself. This suggests that either the inflow variations and jet IR emission are coupled by a non-linear or time-variable transform, or that the IR rms-flux relation is not transferred from the inflow to the jet, but is an intrinsic property of emission processes in the jet.

Characterization of the infrared/X-ray subsecond variability for the black hole transient GX 339-4

NASA Astrophysics Data System (ADS)

Vincentelli, F. M.; Casella, P.; Maccarone, T. J.; Uttley, P.; Gandhi, P.; Belloni, T.; De Marco, B.; Russell, D. M.; Stella, L.; O'Brien, K.

2018-07-01

We present a detailed analysis of the X-ray/IR fast variability of the Black-Hole Transient GX 339-4 during its low/hard state in 2008 August. Thanks to simultaneous high time resolution observations made with the VLT and RXTE, we performed the first characterization of the subsecond variability in the near-infrared band - and of its correlation with the X-rays - for a low-mass X-ray binary, using both time- and frequency-domain techniques. We found a power-law correlation between the X-ray and infrared fluxes when measured on time-scales of 16 s, with a marginally variable slope, steeper than the one found on time-scales of days at similar flux levels. We suggest the variable slope - if confirmed - could be due to the infrared flux being a non-constant combination of both optically thin and optically thick synchrotron emission from the jet, as a result of a variable self-absorption break. From cross spectral analysis, we found an approximately constant infrared time lag of ≈0.1 s, and a very high coherence of ˜90 per cent on time-scales of tens of seconds, slowly decreasing towards higher frequencies. Finally, we report on the first detection of a linear rms-flux relation in the emission from a low-mass X-ray binary jet, on time-scales where little correlation is found between the X-rays and the jet emission itself. This suggests that either the inflow variations and jet IR emission are coupled by a non-linear or time-variable transform, or that the IR rms-flux relation is not transferred from the inflow to the jet, but is an intrinsic property of emission processes in the jet.

Northwest Africa 773: Lunar Mare Breccia with a Shallow-formed Olivine-Cumulate Component, Very-Low-Ti Heritage, and a KREEP Connection

NASA Technical Reports Server (NTRS)

Jolliff, B. L.; Korotev, R. L.; Zeigler, R. A.; Floss, C.; Haskin, L. A.

2003-01-01

Northwest Africa 773 is one of the more unusual lunar meteorites found in recent years because it contains a prominent clast lithology, which appears to be an olivine-rich cumulate and because it is a very-low-Ti (VLT) mare breccia with relatively high incompatible-trace-element concentrations and LREE/HREE enrichment. A lunar origin was verified by Fagan and coworkers on the basis of noble-gas contents, oxygen isotopes, and mineral compositions. Fagan et al. described two lithologies: (1) heterolithic impact breccia with a regolith component and (2) cumulus olivine gabbronorite. Here, we refer to these as the breccia (Bx) lithology and the olivine-cumulate (OC) lithology. The impact breccia components are predominantly volcanic (basaltic), and, in this context, the occurrence of the cumulus lithology is especially significant: is it related to the volcanic components or does it represent a deep-seated rock entrained by the basaltic magma as it rose to the surface? Elevated incompatible-element concentrations with more or less KREEP-like inter-element ratios and very-low-Ti concentrations distinguish both lithologies of this meteorite from Apollo mare basalts. Here, we summarize key compositional information (bulk and mineral), especially related to the OC lithology, to show that it formed at shallow depth and comes from a VLT ultramafic precursor that mixed with a KREEP-like trace-element component deep in the crust or upper mantle.

Evidence That the Directly Imaged Planet HD 131399 Ab Is a Background Star

NASA Astrophysics Data System (ADS)

Nielsen, Eric L.; De Rosa, Robert J.; Rameau, Julien; Wang, Jason J.; Esposito, Thomas M.; Millar-Blanchaer, Maxwell A.; Marois, Christian; Vigan, Arthur; Ammons, S. Mark; Artigau, Etienne; Bailey, Vanessa P.; Blunt, Sarah; Bulger, Joanna; Chilcote, Jeffrey; Cotten, Tara; Doyon, René; Duchêne, Gaspard; Fabrycky, Daniel; Fitzgerald, Michael P.; Follette, Katherine B.; Gerard, Benjamin L.; Goodsell, Stephen J.; Graham, James R.; Greenbaum, Alexandra Z.; Hibon, Pascale; Hinkley, Sasha; Hung, Li-Wei; Ingraham, Patrick; Jensen-Clem, Rebecca; Kalas, Paul; Konopacky, Quinn; Larkin, James E.; Macintosh, Bruce; Maire, Jérôme; Marchis, Franck; Metchev, Stanimir; Morzinski, Katie M.; Murray-Clay, Ruth A.; Oppenheimer, Rebecca; Palmer, David; Patience, Jennifer; Perrin, Marshall; Poyneer, Lisa; Pueyo, Laurent; Rafikov, Roman R.; Rajan, Abhijith; Rantakyrö, Fredrik T.; Ruffio, Jean-Baptiste; Savransky, Dmitry; Schneider, Adam C.; Sivaramakrishnan, Anand; Song, Inseok; Soummer, Remi; Thomas, Sandrine; Wallace, J. Kent; Ward-Duong, Kimberly; Wiktorowicz, Sloane; Wolff, Schuyler

2017-12-01

We present evidence that the recently discovered, directly imaged planet HD 131399 Ab is a background star with nonzero proper motion. From new JHK1L‧ photometry and spectroscopy obtained with the Gemini Planet Imager, VLT/SPHERE, and Keck/NIRC2, and a reanalysis of the discovery data obtained with VLT/SPHERE, we derive colors, spectra, and astrometry for HD 131399 Ab. The broader wavelength coverage and higher data quality allow us to reinvestigate its status. Its near-infrared spectral energy distribution excludes spectral types later than L0 and is consistent with a K or M dwarf, which are the most likely candidates for a background object in this direction at the apparent magnitude observed. If it were a physically associated object, the projected velocity of HD 131399 Ab would exceed escape velocity given the mass and distance to HD 131399 A. We show that HD 131399 Ab is also not following the expected track for a stationary background star at infinite distance. Solving for the proper motion and parallax required to explain the relative motion of HD 131399 Ab, we find a proper motion of 12.3 mas yr-1. When compared to predicted background objects drawn from a galactic model, we find this proper motion to be high but consistent with the top 4% fastest-moving background stars. From our analysis, we conclude that HD 131399 Ab is a background K or M dwarf.

Compositional Evidence for Launch Pairing of the YQ and Elephant Moraine Lunar Meteorites

NASA Technical Reports Server (NTRS)

Korotev, R. L.; Jollitt, B. L.; Zeigler, R. A.; Haskin, L. A.

2003-01-01

Arai and Warren provide convincing evidence that QUE (Queen Alexandra Range) 94281 derives from the same regolith as Y (Yamato) 793274 and, therefore, that the two meteorites were likely ejected from the Moon by the same impact. Recently discovered Y981031 is paired with Y793274. The "YQ" meteorites (Y793274/Y981031 and QUE 94281 are unique among lunar meteorites in being regolith breccias composed of subequal amounts of mare volcanic material (a VLT [very-low-Ti] basalt or gabbro) and feldspathic highland material. EET (Elephant Moraine) 87521 and its pair EET 96008 are fragmental breccias composed mainly of VLT basalt or gabbro. Warren, Arai, and colleagues note that the volcanic components of the YQ and EET meteorites are texturally similar more similar to each other than either is to mare basalts of the Apollo collection. Warren and colleagues address the issue of possible launch pairing of YQ and EET, but note compositional differences between EET and the volcanic component of YQ, as inferred from extrapolations of regressions to high FeO concentration. We show here that: (1) EET 87/96 consists of fragments of a differentiated magma body, (2) subsamples of EET represent a mixing trend between Fe-rich and Mg-rich differentiates, and (3) the inferred volcanic component of YQ is consistent with a point on the EET mixing line. Thus, there is no compositional impediment to the hypothesis that YQ is launch paired with EET.