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Sample records for roap star hd

  1. Detection of new pulsations in the roAp star HD 177765

    NASA Astrophysics Data System (ADS)

    Holdsworth, Daniel L.

    2016-10-01

    We report the discovery of 2 previously undetected pulsation frequencies in the known roAp star HD 177765. Photometric observations by the Kepler space telescope during K2 Campaign 7 show low-amplitude pulsations (4-11 micro mag) previously unseen in photometry. We show the pulsations to be stable over the observation period, and demonstrate that the separation of the frequencies is not representative of the large frequency separation quantity needed to perform asteroseismic analysis.

  2. Pulsation in the atmosphere of the roAp star HD 24712. I. Spectroscopic observations and radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Ryabchikova, T.; Sachkov, M.; Weiss, W. W.; Kallinger, T.; Kochukhov, O.; Bagnulo, S.; Ilyin, I.; Landstreet, J. D.; Leone, F.; Lo Curto, G.; Lüftinger, T.; Lyashko, D.; Magazzù, A.

    2007-02-01

    Aims:We have investigated the structure of the pulsating atmosphere of one of the best studied rapidly oscillating Ap stars, HD 24712. Methods: For this purpose we analyzed spectra collected during 2001-2004. An extensive data set was obtained in 2004 simultaneously with the photometry of the Canadian MOST mini-satellite. This allows us to connect directly atmospheric dynamics observed as radial velocity variations with light variations seen in photometry. Results: We directly derived for the first time and for different chemical elements, respectively ions, phase shifts between photometric and radial velocity pulsation maxima indicating, as we suggest, different line formation depths in the atmosphere. This allowed us to estimate for the first time the propagation velocity of a pulsation wave in the outer stellar atmosphere of a roAp star to be slightly lower than the sound speed. We confirm large pulsation amplitudes (150-400 m s-1) for REE lines and the Hα core, while spectral lines of the other elements (Mg, Si, Ca, and Fe-peak elements) have nearly constant velocities. We did not find different pulsation amplitudes and phases for the lines of rare-earth elements before and after the Balmer jump, which supports the hypothesis of REE concentration in the upper atmosphere above the hydrogen line-forming layers. We also discuss radial velocity amplitudes and phases measured for individual spectral lines as tools for a 3D tomography of the atmosphere of HD 24712. Based on observations collected at the Canada-France-Hawaii Telescope (CFHT), at the Nordic Optical Telescope (NOT), at the European Southern Observatory, Paranal, Chile, (DDT-274.D-5011), at the Telescopio Nazionale Galileo (TNG), and from MOST, a Canadian Space Agency mission operated jointly by Dynacon, Inc., the University of Toronto Institute of Aerospace Studies, and the University of British Columbia, with assistance from the University of Vienna. Tables 4, 5 and Fig. 9 are only available in

  3. The fundamental parameters of the roAp star HD 24712. A rapidly oscillator at the red edge of the instability strip

    NASA Astrophysics Data System (ADS)

    Perraut, K.; Brandão, I.; Cunha, M.; Shulyak, D.; Mourard, D.; Nardetto, N.; ten Brummelaar, T. A.

    2016-05-01

    Context. There is still a debate about the nature of the mechanism that causes the pulsation excitation of the rapidly oscillating Ap stars that oscillate above the highest theoretically acoustic frequency. HD 24712 is a good test case for such a study because it is bright, its parallax accurately determined, and its frequency spectrum is well known. Aims: Visible long-baseline interferometry is a unique technique for measuring accurate angular diameters of targets as small as the brightest roAp stars, and thus estimating accurate radii by a method as independent as possible of atmosphere models. Methods: We used the visible spectrograph VEGA at the CHARA long-baseline optical array to observe HD 24712, and we derived its limb-darkened diameter. We also estimated its bolometric flux from spectroscopic data in the literature and determined its radius, luminosity, and effective temperature. Results: We determined a limb-darkened angular diameter of 0.335 ± 0.009 mas for HD 24712 and derived a radius of R = 1.772 ± 0.057 R⊙, a luminosity of L = 7.2 ± 1.8 L⊙, and an effective temperature of Teff = 7235 ± 280 K, which is in very close agreement with the values provided by the self-consistent stratified model developed for this star. We used these fundamental parameters to set HD 24712 in the Hertzsprung-Russell diagram. Its position is marginally consistent with the region where high radial order modes are predicted to be excited by the κ-mechanism. Conclusions: We conclude that oscillations in this star are most likely not driven by the κ-mechanism. Based on observations made with the VEGA/CHARA spectro-interferometer.

  4. roAp stars: surface lithium abundance distribution and magnetic field configuration

    NASA Astrophysics Data System (ADS)

    Polosukhina, N.; Shulyak, D.; Shavrina, A.; Lyashko, D.; Drake, N. A.; Glagolevski, Yu.; Kudryavtsev, D.; Smirnova, M.

    2014-08-01

    High-resolution spectra obtained with the 6m BTA telescope, Russia, and with HARPS and VLT/UVES telescopes at ESO, Chile, were used for Doppler Imaging analysis of two roAp stars, HD 12098 and HD 60435, showing strong and variable Li resonance line in their spectra. We found that Li has highly inhomogeneous distribution on the surfaces of these stars. We compared our results with previously obtained Doppler Imaging mapping of two CP2 stars, HD 83368 and HD 3980, and discuss the correlation between the position of the high Li-abundance spots and magnetic field.

  5. Doppler mapping of four roAp stars with anomalous lithium abundance

    NASA Astrophysics Data System (ADS)

    Polosukhina, N.; Shulyak, D.; Shavrina, A.; Lyashko, D.; Drake, N.; Glagolevsky, Y.; Kudryavtsev, D.; Smirnova, M.

    2014-11-01

    We present the first results from Doppler Imaging of two roAp stars, HD 12098 and HD 60435, that show strong and variable Li lines in their spectra. High-resolution spectra were obtained with the Russian 6-m BTA telescope, and with the HARPS and VLT/UVES instruments at ESO. We derived the surface abundance distribution of Li and Pr and analysed the correlation between the positions of the Li-abundance spots and magnetic field. We compare our results with Doppler Imaging mapping previously obtained for two CP2 stars, HD 83668 and HD 3980, and discuss the common properties of the locations of the ``Li spots'' on the surfaces of magnetic chemically peculiar A-type stars.

  6. Lithium and Isotopic Ratio Li6/Li7 in Magnetic roAp Stars as an Indicator of Active Processes

    NASA Astrophysics Data System (ADS)

    Polosukhina, N.; Shavrina, A.; Lyashko, D.; Nesvacil, N.; Drake, N.; Smirnova, M.

    2015-04-01

    The lines of lithium at 6708 Å and 6103 Å are analyzed in high resolution spectra of some sharp-lined and slowly rotating roAp stars. Three spectral synthesis codes— STARSP, ZEEMAN2, and SYNTHM—were used. New lines of rare earth elements (REE) from the DREAM database and the lines calculated on the basis of the NIST energy levels were included. Magnetic splitting and other line broadening processes were taken into account. For both lithium lines, the enhanced abundances of lithium in the atmospheres of the stars studied are obtained. The lithium abundance determined from the Li 6103 Å line is higher than that from the Li 6708 Å for all the stars. This may be evidence of vertical lithium stratification, abnormal temperature distribution, or unidentified blending of the 6103 Å line. Our work on two roAp stars, HD 83368 and HD 60435 (Shavrina et al. 2001) provides evidence of an enhanced lithium abundance near the magnetic-field poles. We can expect similar effects in the sharp-lined roAp stars. High lithium abundance for all the stars and the estimates of the 6Li/7Li ratio (0.2-0.5) can be explained by production of Li in the cosmic ray spallation reactions in the interstellar medium where the stars were born, and by preservation of the original 6Li and 7Li by strong magnetic fields of these stars. The values of the 6Li/7Li ratio expected from production by cosmic rays are about 0.5-0.8 (Knauth et al. 2003; Webber et al. 2002). New laboratory and theoretical gf-values for REE lines are necessary in order to refine our estimates of lithium abundances and the isotopic ratio.

  7. A self-consistent chemically stratified atmosphere model for the roAp star 10 Aquilae

    NASA Astrophysics Data System (ADS)

    Nesvacil, N.; Shulyak, D.; Ryabchikova, T. A.; Kochukhov, O.; Akberov, A.; Weiss, W.

    2013-04-01

    Context. Chemically peculiar A-type (Ap) stars are a subgroup of the CP2 stars that exhibit anomalous overabundances of numerous elements, e.g. Fe, Cr, Sr, and rare earth elements. The pulsating subgroup of Ap stars, the roAp stars, present ideal laboratories to observe and model pulsational signatures, as well as the interplay of the pulsations with strong magnetic fields and vertical abundance gradients. Aims: Based on high-resolution spectroscopic observations and observed stellar energy distributions, we construct a self-consistent model atmosphere for the roAp star 10 Aquilae (HD 176232). It accounts for modulations of the temperature-pressure structure caused by vertical abundance gradients. We demonstrate that such an analysis can be used to determine precisely the fundamental atmospheric parameters required for pulsation modelling. Methods: Average abundances were derived for 56 species. For Mg, Si, Ca, Cr, Fe, Co, Sr, Pr, and Nd, vertical stratification profiles were empirically derived using the DDAFit minimisation routine together with the magnetic spectrum synthesis codeSynthmag. Model atmospheres were computed with the LLmodels code, which accounts for the individual abundances and stratification of chemical elements. Results: For the final model atmosphere, Teff = 7550 K and log (g) = 3.8 were adopted. While Mg, Si, Co, and Cr exhibit steep abundance gradients, Ca, Fe, and Sr showed much wider abundance gradients between logτ5000 = -1.5 and 0.5. Elements Mg and Co were found to be the least stratified, while Ca and Sr showed strong depth variations in abundance of up to ≈ 6 dex. Table 4 and Figs. 10-12 are available in electronic form at http://www.aanda.org

  8. On the spectroscopic nature of the cool evolved Am star HD151878

    NASA Astrophysics Data System (ADS)

    Freyhammer, L. M.; Elkin, V. G.; Kurtz, D. W.

    2008-10-01

    Recently, Tiwari, Chaubey & Pandey detected the bright component of the visual binary HD151878 to exhibit rapid photometric oscillations through a Johnson B filter with a period of 6min (2.78mHz) and a high, modulated amplitude up to 22mmag peak-to-peak, making this star by far the highest amplitude rapidly oscillating Ap (roAp) star known. As a new roAp star, HD151878 is of additional particular interest as a scarce example of the class in the northern sky, and only the second known case of an evolved roAp star - the other being HD116114. We used the FIbre-fed Echelle Spectrograph at the Nordic Optical Telescope to obtain high time-resolution spectra at high dispersion to attempt to verify the rapid oscillations. We show here that the star at this epoch is spectroscopically stable to rapid oscillations of no more than a few tens of ms-1. The high-resolution spectra furthermore show the star to be of type Am rather than Ap and we show the star lacks most of the known characteristics for roAp stars. We conclude that this is an Am star that does not pulsate with a 6-min period. The original discovery of pulsation is likely to be an instrumental artefact. Based on observations collected at the Nordic Optical Telescope as part of programme 36-418. E-mail: lfreyham@gmail.com

  9. Time resolved spectroscopy of the cool Ap star HD 213637*

    NASA Astrophysics Data System (ADS)

    Elkin, V. G.; Kurtz, D. W.; Mathys, G.

    2015-02-01

    We present an analysis of high time resolution spectra of the chemically peculiar Ap star HD 213637. The star shows rapid radial velocity variations with a period close to the photometric pulsation period. Radial velocity pulsation amplitudes vary significantly for different rare earth elements. The highest pulsation amplitudes belong to lines of Tb III (˜360 m s-1), Pr II (˜250 m s-1) and Pr III (˜230 m s-1). We did not detect any pulsations from spectral lines of Eu II and in Hα, in contrast to many other roAp stars. We also did not find radial velocity pulsations using spectral lines of other chemical elements, including Mg, Si, Ca, Sc, Cr, Fe, Ni, Y and Ba. There are phase shifts between the maxima of pulsation amplitudes of different rare earth elements and ions, which is evidence of an outwardly running magneto-acoustic wave propagating through the upper stellar atmosphere.

  10. The roAp star α Circinus as seen by BRITE-Constellation

    NASA Astrophysics Data System (ADS)

    Weiss, W. W.; Fröhlich, H.-E.; Pigulski, A.; Popowicz, A.; Huber, D.; Kuschnig, R.; Moffat, A. F. J.; Matthews, J. M.; Saio, H.; Schwarzenberg-Czerny, A.; Grant, C. C.; Koudelka, O.; Lüftinger, T.; Rucinski, S. M.; Wade, G. A.; Alves, J.; Guedel, M.; Handler, G.; Mochnacki, St.; Orleanski, P.; Pablo, B.; Pamyatnykh, A.; Ramiaramanantsoa, T.; Rowe, J.; Whittaker, G.; Zawistowski, T.; Zocłońska, E.; Zwintz, K.

    2016-04-01

    We report on an analysis of high-precision, multi-colour photometric observations of the rapidly-oscillating Ap (roAp) star α Cir. These observations were obtained with the BRITE-Constellation, which is a coordinated mission of five nanosatellites that collects continuous millimagnitude-precision photometry of dozens of bright stars for up to 180 days at a time in two colours (≈Johnson B and R). BRITE stands for BRight Target Explorer. The object α Cir is the brightest roAp star and an ideal target for such investigations, facilitating the determination of oscillation frequencies with high resolution. This star is bright enough for complementary interferometry and time-resolved spectroscopy. Four BRITE satellites observed α Cir for146 d or 33 rotational cycles. Phasing the photometry according to the 4.4790 d rotational period reveals qualitatively different light variations in the two photometric bands. The phased red-band photometry is in good agreement with previously-published WIRE data, showing a light curve symmetric about phase 0.5 with a strong contribution from the first harmonic. The phased blue-lband data, in contrast, show an essentially sinusoidal variation. We model both light curves with Bayesian Photometric Imaging, which suggests the presence of two large-scale, photometrically bright (relative to the surrounding photosphere) spots. We also examine the high-frequency pulsation spectrum as encoded in the BRITE photometry. Our analysis establishes the stability of the main pulsation frequency over the last ≈20 yr, confirms the presence of frequency f7, which was not detected (or the mode not excited) prior to 2006, and excludes quadrupolar modes for the main pulsation frequency. Based on data collected by the BRITE-Constellation satellite mission, built, launched and operated thanks to support from the Austrian Aeronautics and Space Agency, the University of Vienna, the Canadian Space Agency (CSA), the Foundation for Polish Science

  11. HD 24355 observed by the Kepler K2 mission: a rapidly oscillating Ap star pulsating in a distorted quadrupole mode

    NASA Astrophysics Data System (ADS)

    Holdsworth, Daniel L.; Kurtz, Donald W.; Smalley, Barry; Saio, Hideyuki; Handler, Gerald; Murphy, Simon J.; Lehmann, Holger

    2016-10-01

    We present an analysis of the first Kepler K2 mission observations of a rapidly oscillating Ap (roAp) star, HD 24355 (V = 9.65). The star was discovered in SuperWASP broad-band photometry with a frequency of 224.31 d-1 (2596.18 μHz; P = 6.4 min) and an amplitude of 1.51 mmag, with later spectroscopic analysis of low-resolution spectra showing HD 24355 to be an A5 Vp SrEu star. The high-precision K2 data allow us to identify 13 rotationally split sidelobes to the main pulsation frequency of HD 24355. This number of sidelobes combined with an unusual rotational phase variation show this star to be the most distorted quadrupole roAp pulsator yet observed. In modelling this star, we are able to reproduce well the amplitude modulation of the pulsation, and find a close match to the unusual phase variations. We show this star to have a pulsation frequency higher than the critical cut-off frequency. This is currently the only roAp star observed with the Kepler spacecraft in short cadence mode that has a photometric amplitude detectable from the ground, thus allowing comparison between the mmag amplitude ground-based targets and the μmag spaced-based discoveries. No further pulsation modes are identified in the K2 data, showing this star to be a single-mode pulsator.

  12. KIC 7582608: a new Kepler roAp star with frequency variability

    NASA Astrophysics Data System (ADS)

    Holdsworth, D. L.; Smalley, B.; Kurtz, D. W.; Southworth, J.; Cunha, M. S.; Clubb, K. I.

    2015-09-01

    We analyse the fifth roAp star reported in the Kepler field, KIC 7582608, discovered with the SuperWASP project. The object shows a high frequency pulsation at 181.7324d-1 (P = 7.9 min) with an amplitude of 1.45 mmag, and low frequency rotational modulation corresponding to a period of 20.4339 d. Spectral analysis confirms the Ap nature of the target, with characteristic lines of rare earth elements present. From our spectral observations we derive a lower limit on the mean magnetic field modulus of =3.05 ± 0.23 kG. Long Cadence Kepler observations show a frequency quintuplet split by the rotational period of the star, typical for an oblique pulsator. We suggest the star is a quadrupole pulsator with a geometry such that i ~ 66° and β ~ 33°. We detect frequency variations of the pulsation in both the WASP and Kepler data sets on many time scales. Linear, non-adiabatic stability modelling allows us to constrain a region on the HR diagram where the pulsations are unstable, an area consistent with observations.

  13. Multiplicity among peculiar A stars. I. The AP stars HD 8441 and HD 137909, and the AM stars HD 43478 and HD 96391

    NASA Astrophysics Data System (ADS)

    North, P.; Carquillat, J.-M.; Ginestet, N.; Carrier, F.; Udry, S.

    1998-06-01

    We present the first results of a radial-velocity survey of cool Ap and Am stars. HD 8441 is not only a double system with P = 106.357 days, but is a triple one, the third companion having an orbital period larger than 5000 days. Improved orbital elements are given for the classical Ap star HD 137909 = beta CrB by combining our radial velocities with published ones. We yield new orbital elements of the two Am, SB2 binaries HD 43478 and HD 96391. Good estimates of the individual masses of the components of HD 43478 can be given thanks to the eclipses of this system, for which an approximate photometric solution is also proposed. Based on observations made at the Observatoire de Haute Provence (CNRS), France, at the Jungfraujoch station of Observatoire de Geneve, Switzerland, and on data from the ESA Hipparcos satellite. Tables 6 to 12 are 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/Abstract.html

  14. Four new HgMn stars: HD 18104, HD 30085, HD 32867, and HD 53588

    NASA Astrophysics Data System (ADS)

    Monier, R.; Gebran, M.; Royer, F.

    2015-05-01

    Context. We have discovered four new HgMn stars while monitoring a sample of apparently slowly rotating superficially normal bright late-B and early-A stars in the northern hemisphere. Aims: Important classification lines of Hg ii and Mn ii are found as conspicuous features in the high resolution SOPHIE spectra of these stars (R = 75 000). Methods: Several lines of Hg ii, Mn ii and Fe ii were synthesized using model atmospheres and the spectrum synthesis code SYNSPEC48, including hyperfine structure of various isotopes when relevant. These synthetic spectra were compared to high-resolution observations of these stars that have a high signal-to-noise ratio to derive abundances of these key elements. Results: The four stars are found to have distinct enhancements of Hg and Mn, which shows that they are not superficially normal B and A stars, but are new HgMn stars and need to be reclassified as such.

  15. Chromospherically active stars. I - HD 136905

    NASA Technical Reports Server (NTRS)

    Fekel, F. C.; Hall, D. S.; Africano, J. L.; Gillies, K.; Quigley, R.

    1985-01-01

    The variable star HD 136905, recently designated GX Librae, is a chromospherically active K1 III single-lined spectroscopic binary with a period of 11.1345 days. It has moderate strength Ca II H and K and ultraviolet emission features, while H-alpha is strongly in absorption. The inclination of the system is 58 + or - 17 deg and the unseen secondary is most likely a G or K dwarf. The v sin i of the primary, 32 + or - 2 km/s, results in a minimum radius of 7.0 + or - 0.4 solar radii. Since the star fills a substantial fracture of its Roche lab, the double-peaked limit curve seen by photometric observers is predominantly ellipsoidal in nature. Both the photometry and the spectroscopy yield values for the period and the time of conjunction that are identical within their uncertainties.

  16. Triggered Star Formation Surrounding Wolf-Rayet Star HD 211853

    NASA Astrophysics Data System (ADS)

    Liu, Tie; Wu, Yuefang; Zhang, Huawei; Qin, Sheng-Li

    2012-05-01

    The environment surrounding Wolf-Rayet (W-R) star HD 211853 is studied in molecular, infrared, as well as radio, and H I emission. The molecular ring consists of well-separated cores, which have a volume density of 103 cm-3 and kinematic temperature ~20 K. Most of the cores are under gravitational collapse due to external pressure from the surrounding ionized gas. From the spectral energy distribution modeling toward the young stellar objects, the sequential star formation is revealed on a large scale in space spreading from the W-R star to the molecular ring. A small-scale sequential star formation is revealed toward core "A," which harbors a very young star cluster. Triggered star formations are thus suggested. The presence of the photodissociation region, the fragmentation of the molecular ring, the collapse of the cores, and the large-scale sequential star formation indicate that the "collect and collapse" process functions in this region. The star-forming activities in core "A" seem to be affected by the "radiation-driven implosion" process.

  17. A new HgMn star HD 196821

    NASA Astrophysics Data System (ADS)

    Ćalışkan, Şeyma; Ünal, Özge

    2017-02-01

    In this study, we present the chemical abundance analysis of HD 196821. The spectra of HD 196821 was obtained at the TÜBİTAK National Observatory using the Coudé Echelle spectrograph attached to the 1.5 m telescope. We determined the atmospheric parameters of HD 196821: Teff=10600K, log g=3.6, vmic=0 km/s, and [Fe/H]=0.16 dex. HD 196821 shows an overabundance of 85 times solar for Mn and 208,930 times solar for Hg. This strongly suggests that the star should be classified as an HgMn star.

  18. Stellar Companions to the Exoplanet Host Stars HD 2638 and HD 164509

    NASA Astrophysics Data System (ADS)

    Wittrock, Justin M.; Kane, Stephen R.; Horch, Elliott P.; Hirsch, Lea; Howell, Steve B.; Ciardi, David R.; Everett, Mark E.; Teske, Johanna K.

    2016-11-01

    An important aspect of searching for exoplanets is understanding the binarity of the host stars. It is particularly important, because nearly half of the solar-like stars within our own Milky Way are part of binary or multiple systems. Moreover, the presence of two or more stars within a system can place further constraints on planetary formation, evolution, and orbital dynamics. As part of our survey of almost a hundred host stars, we obtained images at 692 and 880 nm bands using the Differential Speckle Survey Instrument (DSSI) at the Gemini-North Observatory. From our survey, we detect stellar companions to HD 2638 and HD 164509. The stellar companion to HD 2638 has been previously detected, but the companion to HD 164509 is a newly discovered companion. The angular separation for HD 2638 is 0.512 ± 0.″002 and for HD 164509 is 0.697+/- 0\\buildrel{\\prime\\prime}\\over{.} 002. This corresponds to a projected separation of 25.6 ± 1.9 au and 36.5 ± 1.9 au, respectively. By employing stellar isochrone models, we estimate the mass of the stellar companions of HD 2638 and HD 164509 to be 0.483 ± 0.007 M ⊙ and 0.416+/- 0.007 {M}⊙ , respectively, and their effective temperatures to be 3570 ± 8 K and 3450 ± 7 K, respectively. These results are consistent with the detected companions being late-type M dwarfs.

  19. The nature of the late B-type stars HD 67044 and HD 42035

    NASA Astrophysics Data System (ADS)

    Monier, R.; Gebran, M.; Royer, F.

    2016-04-01

    While monitoring a sample of apparently slowly rotating superficially normal bright late B and early A stars in the northern hemisphere, we have discovered that HD 67044 and HD 42035, hitherto classified as normal late B-type stars, are actually respectively a new chemically peculiar star and a new spectroscopic binary containing a very slow rotator HD 42035 S with ultra-sharp lines (v_{{e}}sin i= 3.7 km s^{-1}) and a fast rotator HD 42035 B with broad lines. The lines of Ti ii, Cr ii, Mn ii, Sr ii, Y ii, Zr ii and Ba ii are conspicuous features in the high resolution SOPHIE spectrum (R=75000) of HD 67044. The Hg ii line at 3983.93 Å is also present as a weak feature. The composite spectrum of HD 42035 is characterised by very sharp lines formed in HD 42035 S superimposed onto the shallow and broad lines of HD 42035 B. These very sharp lines are mostly due to light elements from C to Ni, the only heavy species definitely present are strontium and barium. Selected lines of 21 chemical elements from He up to Hg have been synthesized using model atmospheres computed with ATLAS9 and the spectrum synthesis code SYNSPEC48 including hyperfine structure of various isotopes when relevant. These synthetic spectra have been adjusted to high resolution high signal-to-noise spectra of HD 67044 and HD 42035 S in order to derive abundances of these key elements. HD 67044 is found to have distinct enhancements of Ti, Cr, Mn, Sr, Y, Zr, Ba and Hg and underabundances in He, C, O, Ca and Sc which shows that this star is not a superficially normal late B-type star, but actually is a new CP star most likely of the HgMn type. HD 42035 S has provisional underabundances of the light elements from C to Ti and overabundances of heavier elements (except for Fe and Sr which are also underabundant) up to barium. These values are lower limits to the actual abundances as we cannot currently place properly the continuum of HD 42035 S. More accurate fundamental parameters and abundances for HD

  20. HD 69686: A MYSTERIOUS HIGH VELOCITY B STAR

    SciTech Connect

    Huang, Wenjin; Gies, D. R.; McSwain, M. V. E-mail: gies@chara.gsu.ed

    2009-09-20

    We report on the discovery of a high velocity B star, HD 69686. We estimate its space velocity, distance, surface temperature, gravity, and age. With these data, we are able to reconstruct the trajectory of the star and to trace it back to its birthplace. We use evolutionary tracks for single stars to estimate that HD 69686 was born 73 Myr ago in the outer part of our Galaxy (r {approx} 12 kpc) at a position well below the Galactic plane (z {approx} -1.8 kpc), a very unusual birthplace for a B star. Along the star's projected path in the sky, we also find about 12 other stars having similar proper motions, and their photometry data suggest that they are located at the same distance as HD 69686 and probably have the same age. We speculate on the origin of this group by star formation in a high velocity cloud or as a Galactic merger fragment.

  1. The Hot Star Triplet HD 206267A

    NASA Astrophysics Data System (ADS)

    Wojdowski, P. S.; Schulz, N. S.; Ishibashi, K.; Huenemoerder, D. P.

    2002-12-01

    We have observed the triple O star system HD 206267 with Chandra HETGS for the purpose of studying the properties and dynamics of the system's stellar wind. The triple system includes a 3.7 day binary which was observed once at each of the two phases of quadrature. The spectrum contains emission lines from hydrogen and helium-like oxygen, neon, and magnesium, helium-like silicon and the iron L-shell ions XVII, XVIII, and XIX. We have fit this spectrum with a combination of emission-line spectra of the individual ions at the temperatures at which the populations of the ions peak. From this fit we derive a temperature differential emission measure distribution which is cut off at temperatures above ~10 MK. All lines are very broad with HWHM velocities of ~ 1500 - 2000 km/s. The Lyman_alpha lines from O, Ne, and Mg are blue shifted and asymmetric as would be expected from shocks within a line driven wind of considerable continuum opacity. The stellar triplet revealed the main orbital velocity of 320 km/s through shifts in the X-ray lines. So far, we have not found any indications for a colliding wind in the X-ray spectrum.

  2. Why the peculiar δ Scuti star HD 187547 is a superstar

    NASA Astrophysics Data System (ADS)

    Antoci, V.; Cunha, M.; Houdek, G.

    2013-12-01

    The δ Scuti pulsators occupy a region in the Hertzsprung-Russell diagram where several physical processes occur: the subsurface convection layers change from being deep and vigorous to being shallow and ineffective to transport energy. This transition has a large impact not only on pulsational stability but also on stellar evolution, activity, transport of angular momentum, mixing processes, etc.. It is therefore of great interest to understand how exactly the stellar structure changes with increasing temperature and mass. Theoretical models (Houdek et al. 1999; Samadi et al. 2002) predicted that the convection in the outer layers of δ Scuti stars is still efficient enough to excite solar-like oscillations. The Kepler target, HD 187547 (a.k.a. Superstar), was the first δ Scuti star to suggest that solar-like oscillations are indeed present in this type of stars (Antoci et al. 2011). There were several reasons to conclude that HD 187547 is a δ Scuti/solar-like hybrid pulsator. (1) The peaks at high frequencies are modes of pulsations approximately equidistantly spaced, as expected for high radial order pressure modes; these peaks are not combination frequencies as it is sometimes observed in δ Scuti stars. (2) The opacity mechanism cannot excite a continuous frequency range as observed in HD 187547 (Pamyatnykh 2000). (3) The identification as an Am star consistent with the low v sini, makes it very unlikely to be a δ Scuti/roAp hybrid, because strong large-scale magnetic fields, a necessity for roAp pulsators, have never been detected in Am stars (Auriere et al. 2010). (4) Although a large number of Am stars are found in binary systems, we find no evidence in the observed spectra for a companion, i.e. no significant RV shift over 170 days can be detected and the absorption lines can perfectly be reproduced by assuming a slowly-rotating chemically peculiar Am star. This means that the peaks at high frequencies are unlikely to be from a companion, because such a

  3. Cometary Dust in the Debris of HD 31648 and HD163296: Two "Baby" Beta pictoris Stars

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Grady, Carol A.; Lynch, David K.; Russell, Ray W.; Hanner, Martha S.

    1999-01-01

    The debris disks surrounding the pre-main-sequence stars HD 31648 and HD 163296 were observed spectroscopically between 3 and 14 microns. Both stars possess a silicate emission feature at 10 Am that resembles that of the star P Pictoris and those observed in solar system comets. The structure of the band is consistent with a mixture of olivine and pyroxene material, plus an underlying continuum of unspecified origin. The similarity in both size and structure of the silicate band suggests that the material in these systems had a processing history similar to that in our own solar system prior to the time that the grains were incorporated into comets.

  4. Actinides in HD 101065 (Przybylski's Star)

    NASA Astrophysics Data System (ADS)

    Cowley, C. R.; Hubrig, S.; Bord, D. J.

    2003-05-01

    There are many strange things about the abundances in Przybylski's star (HD 101065). The most recent study (MN, 217, 299, 2000) finds that among the elements through copper, the abundances scatter with no apparent pattern. The largest deviations from solar are found for magnesium, which may be deficient by somewhat more than 1 dex, and cobalt, which appears to be in excess by about the same amount. The heavier elements especially those beyond barium, and continuing through the actinides uranium and thorium, show a clear pattern and a remarkable coherence. We plot solar and stellar abundances on a logarithmic plot vs. atomic number Z, and displace the solar points upward by some 3 dex. While individual points do not overlap, there is a remarkable similarity in the overall trends from Z = 58-80, including the maxima caused in the solar case by the third r-process peak. Points for the displaced solar actinides fall near their stellar counterparts. The processes that produced the large enhancements of these heavy elements have not caused large fractionations of adjacent elements. We have new spectra from the ESO UVES spectrograph on UT2. Resolution is 80,000 (blue) and 110,000 (red), with S/N > 300. This material, and new oscillator strengths (AA 381, 1090,2002; AA 382, 368, 2002), allow a more complete analysis of U and Th. We find abundances near +2.5 for both elements (log(H) = 12), but uncertainties at the moment are surely +/- 0.3 dex. We are currently working to improve the accuracy. Current errors preclude the use of these observations for accurate cosmochronometry, even if the chemical differentiation were not relevant. If a U/Th ratio of unity could be taken at face value, it would imply an r-process event some 103 years ago. Thanks to B. Pfeiffer help and advice.

  5. HIGH-PRECISION ORBITAL AND PHYSICAL PARAMETERS OF DOUBLE-LINED SPECTROSCOPIC BINARY STARS-HD78418, HD123999, HD160922, HD200077, AND HD210027

    SciTech Connect

    Konacki, Maciej; Helminiak, Krzysztof G.; Muterspaugh, Matthew W.; Kulkarni, Shrinivas R.

    2010-08-20

    We present high-precision radial velocities (RVs) of double-lined spectroscopic binary stars HD78418, HD123999, HD160922, HD200077, and HD210027. They were obtained based on the high-resolution echelle spectra collected with the Keck I/HIRES, Shane/CAT/Hamspec, and TNG/Sarge telescopes/spectrographs over the years 2003-2008 as part of the TATOOINE search for circumbinary planets. The RVs were computed using our novel iodine cell technique for double-line binary stars, which relies on tomographically disentangled spectra of the components of the binaries. The precision of the RVs is of the order of 1-10 m s{sup -1}, and to properly model such measurements one needs to account for the light-time effect within the binary's orbit, relativistic effects, and RV variations due to tidal distortions of the components of the binaries. With such proper modeling, our RVs combined with the archival visibility measurements from the Palomar Testbed Interferometer (PTI) allow us to derive very precise spectroscopic/astrometric orbital and physical parameters of the binaries. In particular, we derive the masses, the absolute K- and H-band magnitudes, and the parallaxes. The masses together with the absolute magnitudes in the K and H bands enable us to estimate the ages of the binaries. These RVs allow us to obtain some of the most accurate mass determinations of binary stars. The fractional accuracy in msin i only, and hence based on the RVs alone, ranges from 0.02% to 0.42%. When combined with the PTI astrometry, the fractional accuracy in the masses in the three best cases ranges from 0.06% to 0.5%. Among them, the masses of HD210027 components rival in precision the mass determination of the components of the relativistic double pulsar system PSR J0737 - 3039. In the near future, for double-lined eclipsing binary stars we expect to derive masses with a fractional accuracy of the order of up to {approx}0.001% with our technique. This level of precision is an order of magnitude

  6. Frequency analysis and pulsational mode identification of two γ Doradus stars: HD 40745 and HD 189631

    NASA Astrophysics Data System (ADS)

    Maisonneuve, F.; Pollard, K. R.; Cottrell, P. L.; Wright, D. J.; De Cat, P.; Mantegazza, L.; Kilmartin, P. M.; Suárez, J. C.; Rainer, M.; Poretti, E.

    2011-08-01

    Gravity modes present in γ Doradus stars probe the deep stellar interiors and are thus of particular interest in asteroseismology. Mode identification will improve the knowledge of these stars considerably and allow an understanding of the issues with current pulsational models. A frequency analysis followed by a mode identification were done based on the high-resolution spectroscopic data of two γ Doradus stars: HD 189631 and HD 40745. Extensive spectroscopic data sets are obtained by three instruments: HARPS, FEROS and HERCULES. We obtained 422 spectra for HD 189631 and 248 spectra for HD 40745. The pulsational frequencies were determined by four methods: analysis of the variation in equivalent width, variation in radial velocity, asymmetry of the line profile and the pixel-by-pixel frequency analysis. The mode identification was done using the recently developed Fourier Parameter Fit method. Without achieving the same degree of confidence for all results, we report the identification of four pulsational modes in HD 189631: (ℓ= 1; m =+1) at f1= 1.67 d-1; (3; -2) at f2= 1.42 d-1; (2; -2) at f3= 0.07 d-1; and (4; +1) at f4= 1.82 d-1; and two modes in HD 40745: (2; -1) at f1= 0.75 d-1 and (3; -3) at f2= 1.09 d-1. This study provides the first pulsational analysis based on spectroscopy of HD 189631 and HD 40745. We discuss the performance of current methods of analysis and outline the difficulties presented by γ Doradus stars. Based on observations made with the 1-m telescope at the Mount John University Observatory (HERCULES), and with ESO telescopes at the La Silla Observatories under the Normal Programme 081.D-0610 (HARPS) and the Large Programmes 178.D-0361 (FEROS) and 182.D-0356 (HARPS). Mode identification results were obtained with the software package FAMIAS developed in the framework of the FP6 European Coordination Action HELAS ().

  7. 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.

  8. HD 30963: a new HgMn star

    NASA Astrophysics Data System (ADS)

    Monier, R.; Gebran, M.; Royer, F.

    2016-12-01

    Using high dispersion high quality spectra of HD 30963 obtained with the echelle spectrograph SOPHIE at Observatoire de Haute Provence in November 2015, we show that this star, hitherto classified as a B9 III superficially normal star, is actually a new Chemically Peculiar star of the HgMn type. Spectrum synthesis reveals large overabundances of Mn, Sr, Y, Zr , Pt and Hg and pronounced underabundances of He and Ni which are characteristic of HgMn stars. We therefore propose that this interesting object be reclassified as a B9 HgMn star.

  9. HD 38451 - J. R. Hind's star that changed colour

    NASA Astrophysics Data System (ADS)

    Warner, Brian; Sneden, Christopher

    1988-09-01

    In 1851, John Russell Hind announced that a star previously observed by him to be very red had become bluish white in color. It is shown that this star, HD 38451, is a ninth magnitude shell star which presumably was ejecting a shell when Hind first observed it. From high dispersion coude spectra, low dispersion IUE spectra, and ground-based photometry, HD 38451 is found to be a normal A21V shell star. Its current values of E(B-V) of about 0.14 is probably caused by interstellar rather than circumstellar reddening. There remains a problem to reconcile the large amount of reddening present when Hind first observed the star with its evidently small diminution in visual brightness at that time.

  10. Polarized Disk Emission from Herbig Ae/Be Stars Observed Using Gemini Planet Imager: HD 144432, HD 150193, HD 163296, and HD 169142

    NASA Astrophysics Data System (ADS)

    Monnier, John D.; Harries, Tim J.; Aarnio, Alicia; Adams, Fred C.; Andrews, Sean; Calvet, Nuria; Espaillat, Catherine; Hartmann, Lee; Hinkley, Sasha; Kraus, Stefan; McClure, Melissa; Oppenheimer, Rebecca; Perrin, Marshall; Wilner, David

    2017-03-01

    In order to look for signs of ongoing planet formation in young disks, we carried out the first J-band polarized emission imaging of the Herbig Ae/Be stars HD 150193, HD 163296, and HD 169142 using the Gemini Planet Imager, along with new H band observations of HD 144432. We confirm the complex “double ring” structure for the nearly face-on system HD 169142 first seen in H-band, finding the outer ring to be substantially redder than the inner one in polarized intensity. Using radiative transfer modeling, we developed a physical model that explains the full spectral energy distribution and J- and H-band surface brightness profiles, suggesting that the differential color of the two rings could come from reddened starlight traversing the inner wall and may not require differences in grain properties. In addition, we clearly detect an elongated, off-center ring in HD 163296 (MWC 275), locating the scattering surface to be 18 au above the midplane at a radial distance of 77 au, co-spatial with a ring seen at 1.3 mm by ALMA linked to the CO snow line. Lastly, we report a weak tentative detection of scattered light for HD 150193 (MWC 863) and a non-detection for HD 144432 the stellar companion known for each of these targets has likely disrupted the material in the outer disk of the primary star. For HD 163296 and HD 169142, the prominent outer rings we detect could be evidence for giant planet formation in the outer disk or a manifestation of large-scale dust growth processes possibly related to snow-line chemistry.

  11. The chemical abundances of the Ap star HD94660

    SciTech Connect

    Giarrusso, M.

    2014-05-09

    In this work I present the determination of chemical abundances of the Ap star HD94660, a possible rapid oscillating star. As all the magnetic chemically peculiar objects, it presents CNO underabundance and overabundance of iron peak elements of ∼100 times and of rare earths up to 4 dex with respect to the Sun. The determination was based on the conversion of the observed equivalent widths into abundances simultaneously to the determination of effective temperature and gravity. Since the Balmer lines of early type stars are very sensitive to the surface gravity while the flux distribution is sensitive to the effective temperature, I have adopted an iterative procedure to match the H{sub α} line profile and the observed UV-Vis-NIR magnitudes of HD94660 looking for a consistency between the metallicity of the atmosphere model and the derived abundances. From my spectroscopic analysis, this star belongs to the no-rapid oscillating class.

  12. Asteroseismology of the δ Scuti star HD 50844

    NASA Astrophysics Data System (ADS)

    Chen, X. H.; Li, Y.; Lai, X. J.; Wu, T.

    2016-09-01

    Aims: We aim to probe the internal structure and investigate with asteroseismology for more detailed information on the δ Scuti star HD 50844. Methods: We analyse the observed frequencies of the δ Scuti star HD 50844 and search for possible multiplets, which are based on the rotational splitting law of g-mode. We tried to disentangle the frequency spectra of HD 50844 only by means of rotational splitting. We then compare these with theoretical pulsation modes, which correspond to stellar evolutionary models with various sets of initial metallicity and stellar mass, to find the best-fitting model. Results: There are three multiplets, including two complete triplets and one incomplete quintuplet, in which mode identifications for spherical harmonic degree l and azimuthal number m are unique. The corresponding rotational period of HD 50844 is found to be 2.44 days. The physical parameters of HD 50844 are well limited in a small region by three modes that have been identified as nonradial ones (f11, f22, and f29) and by the fundamental radial mode (f4). Our results show that the three nonradial modes (f11, f22, and f29) are all mixed modes, which mainly represent the property of the helium core. The fundamental radial mode (f4) mainly represents the property of the stellar envelope. To fit these four pulsation modes, both the helium core and the stellar envelope need to be matched to the actual structure of HD 50844. Finally, the mass of the helium core of HD 50844 is estimated to be 0.173 ± 0.004 M⊙ for the first time. The physical parameters of HD 50844 are determined to be M = 1.81 ± 0.01 M⊙, Z = 0.008 ± 0.001. Teff = 7508 ± 125 K, log g = 3.658 ± 0.004, R = 3.300 ± 0.023 R⊙, L = 30.98 ± 2.39 L⊙.

  13. UVBY photometry of the chemically peculiar stars HD 15980, HR 1094, 33 Gem, and HD 115708

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.

    1999-01-01

    Differential Strömgren uvby photometry obtained with the Four College Automated Photoelectric Telescope shows that the hot HgMn star 33 Gem is photometrically constant. The Si star HD 15980 is found to be a variable whose period is significantly greater than 2 years. The unusual magnetic chemically peculiar Co star HR 1094 is discovered to be a low amplitude photometric variable with the magnetic field period of Hill & Blake, 2.9761 days. The ephemeris for the magnetic chemically peculiar star HD 115708 of Wade et al. is confirmed with the error in its period of 5.07622 days being greatly reduced. The {u}, {v}, {b}, and {y} light curves for both HR 1094 and HD 115708 exhibit differences which indicate complex elemental photospheric abundance distributions. Tables 3-6 are 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/Abstract.html

  14. A SUBSTELLAR COMPANION TO THE DUSTY PLEIADES STAR HD 23514

    SciTech Connect

    Rodriguez, David R.; Zuckerman, B.; Marois, Christian; Macintosh, Bruce; Melis, Carl

    2012-03-20

    With adaptive optics imaging at Keck observatory, we have discovered a substellar companion to the F6 Pleiades star HD 23514, one of the dustiest main-sequence stars known to date (L{sub IR}/L{sub *} {approx} 2%). This is one of the first brown dwarfs discovered as a companion to a star in the Pleiades. The 0.06 M{sub Sun} late-M secondary has a projected separation of {approx}360 AU. The scarcity of substellar companions to stellar primaries in the Pleiades combined with the extremely dusty environment make this a unique system to study.

  15. UVBY photometry of the magnetic CP stars HD 36668, 36 Lyncis, HD 86592, and HR 8861

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.

    2000-05-01

    Differential Strömgren uvby photometric observations from the Four College Automated Photoelectric Telescope (FCAPT) are presented for the magnetic CP stars HD 36668, 36 Lyn, HD 86592, and HR 8861. Using the FCAPT values, North's period for HD 36668 is refined to 2.11884 days. The 3.834 day period of Shore et al. for 36 Lyn, which was found from magnetic field measurements, is confirmed by photometry. The FCAPT observations also support the 2.8867 day period of Babel & North for HD 86592, demonstrate that this star is a large amplitude variable in v (0.13 mag.), and show that y varies crudely out of phase from u, v, and b which are in phase with one another. The variability of HR 8861 appears to be correlated with the meridional passages of regions of Si over- and underabundance as found by Piskunov et al. Tables~2, 3, 4 and 5 are 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/Abstract.html

  16. CHARACTERIZING THE RIGIDLY ROTATING MAGNETOSPHERE STARS HD 345439 AND HD 23478

    SciTech Connect

    Wisniewski, J. P.; Lomax, J. R.; Chojnowski, S. D.; Davenport, J. R. A.; Bartz, J.; Pepper, J.; Whelan, D. G.; Eikenberry, S. S.; Majewski, S. R.; Skrutskie, M.; Richardson, N. D.

    2015-10-01

    The SDSS III APOGEE survey recently identified two new σ Ori E type candidates, HD 345439 and HD 23478, which are a rare subset of rapidly rotating massive stars whose large (kGauss) magnetic fields confine circumstellar material around these systems. Our analysis of multi-epoch photometric observations of HD 345439 from the Kilodegree Extremely Little Telescope, Wide Angle Search for Planets, and ASAS surveys reveals the presence of a ∼0.7701 day period in each data set, suggesting the system is among the faster known σ Ori E analogs. We also see clear evidence that the strength of Hα, H i Brackett series lines, and He i lines also vary on a ∼0.7701 day period from our analysis of multi-epoch, multi-wavelength spectroscopic monitoring of the system from the APO 3.5 m telescope. We trace the evolution of select emission line profiles in the system, and observe coherent line profile variability in both optical and infrared H i lines, as expected for rigidly rotating magnetosphere stars. We also analyze the evolution of the H i Br-11 line strength and line profile in multi-epoch observations of HD 23478 from the SDSS-III APOGEE instrument. The observed periodic behavior is consistent with that recently reported by Sikora and collaborators in optical spectra.

  17. Magnetic Doppler imaging of the chemically peculiar star HD 125248

    NASA Astrophysics Data System (ADS)

    Rusomarov, N.; Kochukhov, O.; Ryabchikova, T.; Ilyin, I.

    2016-04-01

    Context. Intermediate-mass, chemically peculiar stars with strong magnetic fields provide an excellent opportunity to study the topology of their surface magnetic fields and the interplay between magnetic geometries and abundance inhomogeneities in the atmospheres of these stars. Aims: We reconstruct detailed maps of the surface magnetic field and abundance distributions for the magnetic Ap star HD 125248. Methods: We performed the analysis based on phase-resolved, four Stokes parameter spectropolarimetric observations obtained with the HARPSpol instrument. These data were interpreted with the help of magnetic Doppler imaging techniques and model atmospheres taking the effects of strong magnetic fields and nonsolar chemical composition into account. Results: We improved the atmospheric parameters of the star, Teff = 9850 ± 250 K and log g = 4.05 ± 0.10. We performed detailed abundance analysis, which confirmed that HD 125248 has abundances typical of other Ap stars, and discovered significant vertical stratification effects for the Fe ii and Cr ii ions. We computed LSD Stokes profiles using several line masks corresponding to Fe-peak and rare earth elements, and studied their behavior with rotational phase. Combining previous longitudinal field measurements with our own observations, we improved the rotational period of the star Prot = 9.29558 ± 0.00006 d. Magnetic Doppler imaging of HD 125248 showed that its magnetic field is mostly poloidal and quasi-dipolar with two large spots of different polarity and field strength. The chemical maps of Fe, Cr, Ce, Nd, Gd, and Ti show abundance contrasts of 0.9-3.5 dex. Among these elements, the Fe abundance map does not show high-contrast features. Cr is overabundant around the negative magnetic pole and has 3.5 dex abundance range. The rare earth elements and Ti are overabundant near the positive magnetic pole. Conclusions: The magnetic field of HD 125248 has strong deviations from the classical oblique dipole field

  18. Spectroscopic Analysis of the Supergiant Star HD 54605

    NASA Astrophysics Data System (ADS)

    Peña, L.; Rosenzweig, P.; Guzmán, E.; Hearnshaw, J.

    2009-05-01

    The main purpose of the present study is to analyze a high resolution spectrum of the supergiant star HD 54605, obtained in the year 2003, with a CCD coupled with the spectrograph HERCULES, attached to the 1m reflector telescope of Mt. John Observatory of the University of Canterbury (New Zealand). This spectrum covers the region λλ ≈ 4505-7080Å, with R = 41000 and a dispersion of ≈ 2Å/mm. According to previous spectroscopic observations, of low dispersion, the radial velocity of this star showed that it does not vary in periods of time relatively short. Until the present, we have identified five hundred photospheric lines, from which, with no doubt, we will obtain a satisfactory result that will give an important contribution to the database of the values of the radial velocity of HD 54605. We observe that Hβ, shows a relatively wide and deep profile and is in complete absorption.

  19. HERSCHEL-RESOLVED OUTER BELTS OF TWO-BELT DEBRIS DISKS AROUND A-TYPE STARS: HD 70313, HD 71722, HD 159492, AND F-TYPE: HD 104860

    SciTech Connect

    Morales, F. Y.; Bryden, G.; Werner, M. W.; Stapelfeldt, K. R.

    2013-10-20

    We present dual-band Herschel/Photodetector Array Camera and Spectrometer imaging for four stars whose spectral energy distributions (SEDs) suggest two-ring disk architectures that mirror that of the asteroid-Kuiper Belt geometry of our own solar system. The Herschel observations at 100 μm spatially resolve the cold/outer-dust component for each star-disk system for the first time, finding evidence of planetesimals at >100 AU, i.e., a larger size than assumed from a simple blackbody fit to the SED. By breaking the degeneracy between the grain properties and the dust's radial location, the resolved images help constrain the dust grain-size distribution for each system. Three of the observed stars are A-type and one solar-type. On the basis of the combined Spitzer/IRS+MIPS (5-70 μm), the Herschel/PACS (100 and 160 μm) dataset, and under the assumption of idealized spherical grains, we find that the cold/outer belts of the three A-type stars are well fit with a mixed ice/rock composition rather than pure rocky grains, while the debris around the solar-type star is consistent with either rock or ice/rock grains. For the solar-type star HD 104860, we find that the minimum grain size is larger than expected from the threshold set by radiative blowout. The A-type stars HD 71722 and HD 159492, on the other hand, require minimum grain sizes that are smaller than blowout for inner- and outer-ring populations. In the absence of spectral features for ice, we find that the behavior of the continuum can help constrain the composition of the grains (of icy nature and not pure rocky material) given the Herschel-resolved locations of the cold/outer-dust belts.

  20. An Analysis of the Rapidly Rotating Bp star HD 133880

    NASA Technical Reports Server (NTRS)

    Bailey, J. D.; Grunhut, J.; Shultz, M.; Wade, G.; Landstreet, J. D.; Bohlender, D.; Lim, J.; Wong, K.; Drake, S.; Linsky, J.

    2012-01-01

    HD 133880 is a rapidly rotating chemically peculiar B-type (Bp) star (nu sin i approx = 103km/s) and is host to one of the strongest magnetic fields of any Ap/Bp star. A member of the Upper Centaurus Lupus association, it is a star with a well-determined age of 16 Myr. 12 new spectra, four of which are polarimetric, obtained from the FEROS, ESPaDOnS and HARPS instruments, provide sufficient material from which to re-evaluate the magnetic field and obtain a first approximation to the atmospheric abundance distributions of He, O, Mg, Si, Ti. Cr, Fe, Ni, Pr and Nd. An abundance analysis was carried out using ZEEMAN, a program which synthesizes spectral line profiles for stars with permeating magnetic fields. The magnetic field structure was characterized by a colinear multipole expansion from the observed variations of the longitudinal and surface fields with rotational phase. Both magnetic hemispheres are clearly visible during the stellar rotation, and thus a three-ring abundance distribution model encompassing both magnetic poles and magnetic equator with equal spans in colatitude was adopted. Using the new magnetic field measurements and optical photometry together with previously published data, we refine the period of HD 133880 to P = 0.877 476 +/- 0.000009 d. Our simple axisymmetric magnetic field model is based on a predominantly quadrupolar component that roughly describes the field variations. Using spectrum synthesis, we derived mean abundances for O, Mg, Si, Ti, Cr, Fe and Pr. All elements; except Mg, are overabundant compared to the Son. Mg appears to be approximately uniform over the stellar surface, while all other elements are more abundant in the negative magnetic hemisphere than in the positive magnetic hemisphere. In contrast to most Ap/Bp stars which show an underabundance in 0, in HD 133880 this element is clearly overabundant compared to the solar abundance ratio. In studying the Ha and Paschen lines in the optical spectra, we could not

  1. Acoustic Oscillations in Main-Sequence Stars: HD155543

    NASA Astrophysics Data System (ADS)

    Belmonte, J. A.; Pérez Hernández, F.; Roca Cortés, T.

    High-speed photometric techniques have been found useful as a way to study the acoustic mode signature in low main sequence stars. In this work, the discovery of solar-like oscillations associated to the presence of acoustic modes of pulsation in the F2V star HD155543, located outside of the instability strip, is reported. This finding has been obtained through an analysis of a long series of data (184 hours) obtained in 20 nights of observation with two twin three channel photometers attached to two 1.5 m telescopes sited at two observatories, simultaneously: Teide (OT) at Tenerife (Spain) and San Pedro Mártir (SPM) at Baja California Norte (Mexico). The major results yielded have been: the range of frequencies where p-modes signal is present (1 to 3 mHz); an upper limit of 20 µmag for the amplitude of the modes; the mean spacing between modes of equal degree l and consecutive order n, v o = 97.3 ± 0.6 µHz and two possible values of D o, 1.4 or 1.8 µHz. The values of these parameters agree, within the resolution, with those yielded by standard computed models of main sequence stars compatible with the luminosity and effective temperature already known for HD155543. These results open new perspectives for astero-seismology in the near future.

  2. Chromospherically active stars. X - Spectroscopy and photometry of HD 212280

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Browning, Jared C.; Henry, Gregory W.; Morton, Mary D.; Hall, Douglas S.

    1993-01-01

    The system HD 212280 is a chromospherically active double lined spectroscopic binary with an orbital period of 45.284 days and an eccentricity of 0.50. The spectrum is composite with spectral types of G8 IV and F5-8 V for the components. An estimated inclination of 78 +/- 8 deg results in masses of 1.7 and 1.4 solar mass for the G subgiant and mid-F star, respectively. The distance to the system is estimated to be 112 pc. Photometric observations obtained between 1987 November and 1992 June reveal that HD 212280 is a newly identified variable star with a V amplitude of about 0.15 mag and a mean period of 29.46 days. Our V data were divided into 11 sets and in all but one case two spots were required to fit the data. Lifetimes of 650 days and a minimum of 1350 days have been determined for two of the four spots. The differential rotation coefficient of 0.05 is relatively small. The age of the system is about 1.9 X 10 exp 9 yrs. The G subgiant is rotating slower than pseudosynchronously while the F-type star is rotating faster.

  3. THE NEARBY, YOUNG, ISOLATED, DUSTY STAR HD 166191

    SciTech Connect

    Schneider, Adam; Song, Inseok; Hufford, Tara; Melis, Carl; Zuckerman, B.; Bessell, Mike; Hinkley, Sasha E-mail: song@physast.uga.edu E-mail: cmelis@ucsd.edu E-mail: bessell@mso.anu.edu.au

    2013-11-01

    We report an in-depth study of the F8-type star HD 166191, identified in an ongoing survey for stars exhibiting infrared emission above their expected photospheres in the Wide-field Infrared Survey Explorer all-sky catalog. The fractional IR luminosity measured from 3.5 to 70 μm is exceptionally high (L{sub IR}/L{sub bol} ∼ 10%). Near-diffraction-limited imaging observations with the T-ReCS Si filter set on the Gemini South telescope and adaptive optics imaging with the NIRC2 Lp filter on the Keck II telescope confirmed that the excess emission coincides with the star. Si-band images show a strong solid-state emission feature at ∼10 μm. Theoretical evolutionary isochrones and optical spectroscopic observations indicate a stellar age in the range 10-100 Myr. The large dust mass seen in HD 166191's terrestrial planet zone is indicative of a recent collision between planetary embryos or massive ongoing collisional grinding associated with planet building.

  4. Spectrophotometry of peculiar B and A stars. XIV - 56 Arietis, 41 Tauri, 25 Sextantis, HD 170973, HD 205087, and HD 215441

    NASA Astrophysics Data System (ADS)

    Adelman, S. J.

    1983-03-01

    Optical region spectrophotometry of six relatively hot Ap stars is presented. Additional scans of 56 Ari extend the results of an earlier paper in this series. The data for 41 Tau, 25 Sex, HD 170973, and HD 215441 are studied as a function of phase. The observations of HD 205087 are inconclusive about its variability although they show spectrophotometrically that it is a definite Ap star. The observations of HD 215441 show a prominent λ5200 broad, continuum feature with an unusual shape. However, when the data are corrected for interstellar reddening, the energy distribution resembles those of other silicon stars. The λ5200 feature is found to be variable in phase with the U-B and B-V colors and with the magnetic field strength. This feature is strongest when the Balmer jump is smallest, the Paschen continuum the bluest according to B-V, and the surface magnetic field strength the largest.

  5. Cometary Dust in the Debris Disks of HD 31648 and HD 163296: Two "Baby" (BETA) Pictoris Stars

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Grady, Carol A.; Lynch, David K.; Russell, Ray W.; Hanner, Martha S.; Hanner, Martha S.

    1999-01-01

    The debris disks surrounding the pre-main-sequence stars HD 31648 and HD 163296 were observed spectroscopically between 3 and 14 microns. Both stars possess a silicate emission feature at 10 microns that resembles that of the star beta Pictoris and those observed in solar system comets. The structure of the band is consistent with a mixture of olivine and pyroxene material, plus an underlying continuum of unspecified origin. The similarity in both size and structure of the silicate band suggests that the material in these systems had a processing history similar to that in our own solar system prior to the time that the grains were incorporated into comets.

  6. Far-ultraviolet energy distributions of the metal-poor A stars HD 109995 and HD 161817

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, E.

    1981-01-01

    Low-resolution IUE spectra at wavelengths between 1300 and 3400 A of the metal-poor stars HD 109995 (A1p) and HD 161817 (A4p) have been compared with model-atmosphere energy distributions computed by Kurucz (1979). Good overall agreement is found. Effective temperatures, metal abundances, and angular diameters could be determined. Assuming an absolute visual magnitude of 0.7, the previously determined gravity log = 3 yields masses of 0.5 solar masses for both stars. It is found that the theoretical UBV colors calculated earlier agree reaonably well with the ones observed for these stars.

  7. ARTIST'S CONCEPT -- 'HOT JUPITER' AROUND THE STAR HD 209458

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is an artist's impression of the gas-giant planet orbiting the yellow, Sun-like star HD 209458, 150 light-years from Earth. Astronomers used NASA's Hubble Space Telescope to look at this world and make the first direct detection of an atmosphere around an extrasolar planet. The planet was not directly seen by Hubble. Instead, the presence of sodium was detected in light filtered through the planet's atmosphere when it passed in front of its star as seen from Earth (an event called a transit). The planet was discovered in 1999 by its subtle gravitational pull on the star. The planet is 70 percent the mass of Jupiter, the largest planet in our solar system. Its orbit is tilted nearly edge-on to Earth, which allows repeated transit observations. The planet is merely 4 million miles from the star. The distance between the pair is so close that the yellow star looms in the sky, with an angular diameter 23 times larger than the full Moon's diameter as seen from Earth, and glows 500 times brighter than our Sun. At this precarious distance the planet's atmosphere is heated to 2000 degrees Fahrenheit (1100 degrees Celsius). But the planet is big enough to hold onto its seething atmosphere. Illustration Credit: NASA and Greg Bacon (STScI/AVL)

  8. Magnetic Doppler Imaging of He-strong star HD 184927

    NASA Astrophysics Data System (ADS)

    Yakunin, I.; Wade, G.; Bohlender, D.; Kochukhov, O.; Tsymbal, V.; Tsymbal

    2014-08-01

    We have employed an extensive new timeseries of Stokes I and V spectra obtained with the ESPaDOnS spectropolarimeter at the 3.6-m Canada-France-Hawaii Telescope to investigate the physical parameters, chemical abundance distributions and magnetic field topology of the slowly-rotating He-strong star HD 184927. We infer a rotation period of 9 d .53071 +/- 0.00120 from Hα, Hβ, LSD magnetic measurements and EWs of helium lines. We used an extensive NLTE TLUSTY grid along with the SYNSPEC code to model the observed spectra and find a new value of luminosity. In this poster we present the derived physical parameters of the star and the results of Magnetic Doppler Imaging analysis of the Stokes I and V profiles. Wide wings of helium lines can be described only under the assumption of the presence of a large, very helium-rich spot.

  9. An analysis of the rapidly rotating Bp star HD 133880

    NASA Astrophysics Data System (ADS)

    Bailey, J. D.; Grunhut, J.; Shultz, M.; Wade, G.; Landstreet, J. D.; Bohlender, D.; Lim, J.; Wong, K.; Drake, S.; Linsky, J.

    2012-06-01

    HD 133880 is a rapidly rotating chemically peculiar B-type (Bp) star (v sin i≃ 103 km s-1) and is host to one of the strongest magnetic fields of any Ap/Bp star. A member of the Upper Centaurus Lupus association, it is a star with a well-determined age of 16 Myr. 12 new spectra, four of which are polarimetric, obtained from the FEROS, ESPaDOnS and HARPS instruments, provide sufficient material from which to re-evaluate the magnetic field and obtain a first approximation to the atmospheric abundance distributions of He, O, Mg, Si, Ti, Cr, Fe, Ni, Pr and Nd. An abundance analysis was carried out using ZEEMAN, a program which synthesizes spectral line profiles for stars with permeating magnetic fields. The magnetic field structure was characterized by a colinear multipole expansion from the observed variations of the longitudinal and surface fields with rotational phase. Both magnetic hemispheres are clearly visible during the stellar rotation, and thus a three-ring abundance distribution model encompassing both magnetic poles and magnetic equator with equal spans in colatitude was adopted. Using the new magnetic field measurements and optical photometry together with previously published data, we refine the period of HD 133880 to P= 0.877 476 ± 0.000 009 d. Our simple axisymmetric magnetic field model is based on a predominantly quadrupolar component that roughly describes the field variations. Using spectrum synthesis, we derived mean abundances for O, Mg, Si, Ti, Cr, Fe and Pr. All elements, except Mg, are overabundant compared to the Sun. Mg appears to be approximately uniform over the stellar surface, while all other elements are more abundant in the negative magnetic hemisphere than in the positive magnetic hemisphere. In contrast to most Ap/Bp stars which show an underabundance in O, in HD 133880 this element is clearly overabundant compared to the solar abundance ratio. In studying the Hα and Paschen lines in the optical spectra, we could not unambiguously

  10. STELLAR VARIABILITY OF THE EXOPLANET HOSTING STAR HD 63454

    SciTech Connect

    Kane, Stephen R.; Dragomir, Diana; Ciardi, David R.; Lee, Jae-Woo; Lo Curto, Gaspare; Lovis, Christophe; Naef, Dominique; Udry, Stephane; Mahadevan, Suvrath; Pilyavsky, Genady; Wang Xuesong; Wright, Jason

    2011-08-20

    Of the hundreds of exoplanets discovered using the radial velocity (RV) technique, many are orbiting close to their host stars with periods less than 10 days. One of these, HD 63454, is a young active K dwarf which hosts a Jovian planet in a 2.82 day period orbit. The planet has a 14% transit probability and a predicted transit depth of 1.2%. Here we provide a re-analysis of the RV data to produce an accurate transit ephemeris. We further analyze 8 nights of time series data to search for stellar activity both intrinsic to the star and induced by possible interactions of the exoplanet with the stellar magnetospheres. We establish the photometric stability of the star at the 3 mmag level despite strong Ca II emission in the spectrum. Finally, we rule out photometric signatures of both star-planet magnetosphere interactions and planetary transit signatures. From this we are able to place constraints on both the orbital and physical properties of the planet.

  11. Stellar Variability of the Exoplanet Hosting Star HD 63454

    NASA Astrophysics Data System (ADS)

    Kane, Stephen R.; Dragomir, Diana; Ciardi, David R.; Lee, Jae-Woo; Lo Curto, Gaspare; Lovis, Christophe; Naef, Dominique; Mahadevan, Suvrath; Pilyavsky, Genady; Udry, Stephane; Wang, Xuesong; Wright, Jason

    2011-08-01

    Of the hundreds of exoplanets discovered using the radial velocity (RV) technique, many are orbiting close to their host stars with periods less than 10 days. One of these, HD 63454, is a young active K dwarf which hosts a Jovian planet in a 2.82 day period orbit. The planet has a 14% transit probability and a predicted transit depth of 1.2%. Here we provide a re-analysis of the RV data to produce an accurate transit ephemeris. We further analyze 8 nights of time series data to search for stellar activity both intrinsic to the star and induced by possible interactions of the exoplanet with the stellar magnetospheres. We establish the photometric stability of the star at the 3 mmag level despite strong Ca II emission in the spectrum. Finally, we rule out photometric signatures of both star-planet magnetosphere interactions and planetary transit signatures. From this we are able to place constraints on both the orbital and physical properties of the planet.

  12. Accurate radio and optical positions for the radio star HD 36705 (AB Doradus)

    NASA Technical Reports Server (NTRS)

    White, Graeme L.; Jauncey, David L.; Batty, Michael J.; Peters, W. L.; Gulkis, S.

    1988-01-01

    Arc-second position measurements of the active star HD 36705 (AB Dor) and of the variable radio source found nearby are presented. These measurements show that the radio source is clearly identified with HD 36705 and not with the nearby red-dwarf star Rst 137B.

  13. Stellar activity of planetary host star HD 189 733

    NASA Astrophysics Data System (ADS)

    Boisse, I.; Moutou, C.; Vidal-Madjar, A.; Bouchy, F.; Pont, F.; Hébrard, G.; Bonfils, X.; Croll, B.; Delfosse, X.; Desort, M.; Forveille, T.; Lagrange, A.-M.; Loeillet, B.; Lovis, C.; Matthews, J. M.; Mayor, M.; Pepe, F.; Perrier, C.; Queloz, D.; Rowe, J. F.; Santos, N. C.; Ségransan, D.; Udry, S.

    2009-03-01

    Aims: Extra-solar planet search programs require high-precision velocity measurements. They need to determine how to differentiate between radial-velocity variations due to Doppler motion and the noise induced by stellar activity. Methods: We monitored the active K2V star HD 189 733 and its transiting planetary companion, which has a 2.2-day orbital period. We used the high-resolution spectograph SOPHIE mounted on the 1.93-m telescope at the Observatoire de Haute-Provence to obtain 55 spectra of HD 189 733 over nearly two months. We refined the HD 189 733b orbit parameters and placed limits on both the eccentricity and long-term velocity gradient. After subtracting the orbital motion of the planet, we compared the variability in spectroscopic activity indices with the evolution in the radial-velocity residuals and the shape of spectral lines. Results: The radial velocity, the spectral-line profile, and the activity indices measured in He I (5875.62 Å), Hα (6562.81 Å), and both of the Ca II H&K lines (3968.47 Å and 3933.66 Å, respectively) exhibit a periodicity close to the stellar-rotation period and the correlations between them are consistent with a spotted stellar surface in rotation. We used these correlations to correct for the radial-velocity jitter due to stellar activity. This results in achieving high precision in measuring the orbital parameters, with a semi-amplitude K = 200.56 ± 0.88 m s-1 and a derived planet mass of MP = 1.13 ± 0.03 M_Jup. Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium (program 07A.PNP.CONS).

  14. The physical parameters of the retired a star HD 185351

    SciTech Connect

    Johnson, John Asher; Huber, Daniel; Barclay, Thomas; Boyajian, Tabetha; Brewer, John M.; White, Timothy R.; Von Braun, Kaspar; Maestro, Vicente; Stello, Dennis

    2014-10-10

    We report here an analysis of the physical stellar parameters of the giant star HD 185351 using Kepler short-cadence photometry, optical and near infrared interferometry from CHARA, and high-resolution spectroscopy. Asteroseismic oscillations detected in the Kepler short-cadence photometry combined with an effective temperature calculated from the interferometric angular diameter and bolometric flux yield a mean density ρ{sub *} = 0.0130 ± 0.0003 ρ{sub ☉} and surface gravity log g = 3.280 ± 0.011. Combining the gravity and density we find R {sub *} = 5.35 ± 0.20 R {sub ☉} and M {sub *} = 1.99 ± 0.23 M {sub ☉}. The trigonometric parallax and CHARA angular diameter give a radius R {sub *} = 4.97 ± 0.07 R {sub ☉}. This smaller radius, when combined with the mean stellar density, corresponds to a stellar mass 1.60 ± 0.08 M {sub ☉}, which is smaller than the asteroseismic mass by 1.6σ. We find that a larger mass is supported by the observation of mixed modes in our high-precision photometry, the spacing of which is consistent only for M {sub *} ≳ 1.8 M {sub ☉}. Our various and independent mass measurements can be compared to the mass measured from interpolating the spectroscopic parameters onto stellar evolution models, which yields a model-based mass M {sub *,} {sub model} = 1.87 ± 0.07 M {sub ☉}. This mass agrees well with the asteroseismic value, but is 2.6σ higher than the mass from the combination of asteroseismology and interferometry. The discrepancy motivates future studies with a larger sample of giant stars. However, all of our mass measurements are consistent with HD 185351 having a mass in excess of 1.5 M {sub ☉}.

  15. B fields in OB stars (BOB): FORS 2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD 23478 and HD 345439

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; Schöller, M.; Fossati, L.; Morel, T.; Castro, N.; Oskinova, L. M.; Przybilla, N.; Eikenberry, S. S.; Nieva, M.-F.; Langer, N.

    2015-06-01

    Aims: Massive B-type stars with strong magnetic fields and fast rotation are very rare and pose a mystery for theories of star formation and magnetic field evolution. Only two such stars, called σ Ori E analogues, were known until recently. A team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, announced the discovery of two additional rigidly rotating magnetosphere stars, HD 23478 and HD 345439. The magnetic fields in these newly discovered σ Ori E analogues have not been investigated so far. Methods: In the framework of our ESO Large Programme and one normal ESO programme, we carried out low-resolution FORS 2 spectropolarimetric observations of HD 23478 and HD 345439. Results: In the measurements of hydrogen lines, we discover a rather strong longitudinal magnetic field of up to 1.5 kG in HD 23478 and up to 1.3 kG using the entire spectrum. The analysis of HD 345439 using four subsequent spectropolarimetric subexposures does not reveal a magnetic field at a significance level of 3σ. On the other hand, individual subexposures indicate that HD 345439 may host a strong magnetic field that rapidly varies over 88 min. The fast rotation of HD 345439 is also indicated by the behaviour of several metallic and He i lines in the low-resolution FORS 2 spectra that show profile variations already on this short time-scale. Based on observations obtained in the framework of the ESO Prgs. 191.D-0255(E) and 094.D-0355(B).Appendix A is available in electronic form at http://www.aanda.org

  16. Spectroscopic Monitoring of the Be Star HD 50138

    NASA Astrophysics Data System (ADS)

    Morrison, N. D.; Beaver, M.

    1995-03-01

    HD 50138 has been proposed as a possible pre-main-sequence star with an accretion disk, i.e., as a Herbig Ae/Be star. It has a large infrared excess, and the C IV resonance lines sometimes show absorption from accreting gas (Grady et al. 1994, ASP Conf. Ser. 62, p. 409). In order to test further the hypothesis of an accretion disk, we studied CCD echelle spectra obtained from 1993 Nov. to 1995 Mar. with the 1-m telescope of Ritter Observatory. The spectral resolution of this material is 0.23 Angstroms at lambda 5800, and the SNR ranges from about 20 to about 100. The spectral coverage consists of 9 disjoint 70- Angstroms regions in the yellow and red; features of interest in these spectra are Hα , [O I] lambda 6364 and lambda 5577, the Na D lines, He I lambda 5876, and Si II lambda lambda 6347, 6371. The [O I] lines show little or no variability. Transient, blue-shifted absorption features occasionally occur (not simultaneously) in Hα and the D lines; similar features were observed by Doazan (1965, Ann. d'Ap., 28, 1). Hα is a strong, double-peaked emission feature, with the central absorption approximately at rest with respect to the center of mass of the star. The He I and Si II lines have their absorption minima at this same velocity, but they show weak emission on the short-wavelength shoulder and an extended red wing---in short, an inverse P-Cygni profile. The long-wavelength wing is strongly variable, occasionally disappearing completely to leave a symmetrical absorption feature (although the short-wavelength emission persists at these times). These line profile characteristics support the claim that this star is accreting gas, and they are consistent with a disk geometry. [amount] These observations were carried out as part of a multiwavelength campaign involving several individuals, including C. Grady (CSC), K. Bjorkman (U. Wisc.), and R. Schulte-Ladbeck (U. Pitt.). MB's participation in this research was supported by the REU program of the NSF.

  17. FUSE Observations of the Herbig Be star HD 100546

    NASA Astrophysics Data System (ADS)

    Deleuil, M.; Roberge, A.; Feldman, P. D.; Lecavelier des Etangs, A.; Vidal-Madjar, A.; Bouret, J.-C.; Ferlet, R.; André, M.; Moos, H. W.; Blair, W. P.; FUSE Science Team

    2000-12-01

    The first observation of the Herbig Be star HD100546 in the far UV has been made by the Far Ultraviolet Spectroscopic Explorer (FUSE). The spectra reveal numerous circumstellar absorption lines arising not only from the fine structure levels of refractory species like Fe 2, but also from neutral volatiles: C 1, C 1*, N 1 and N 1*. H2 transitions detected in absorption probe the cold gaseous portion of the circumstellar environment. Strong unexpected emission lines are also observed below 1100 Å, where the stellar continuum flux is very low. In particular, broad C 3 and O 6 emission lines demonstrate the presence of hot, dense, collisionally ionized gas which may be related to an extended chromosphere and/or corona. These features reveal a complex circumstellar environment, with wide range of temperatures and physical conditions. Based on observations obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission. FUSE is operated for NASA by the John Hopkins University under NASA contract NASS-32985.

  18. HD 98800: A Unique Stellar System of Post-T Tauri Stars

    NASA Technical Reports Server (NTRS)

    Soderblom, David R.; King, Jeremy R.; Siess, Lionel; Noll, Keith S.; Gilmore, Diane M.; Henry, Todd J.; Nelan, Edmund; Burrows, Christopher J.; Brown, Robert A.; Perryman, M. A. C.; Benedict, G. Fritz; McArthur, Barbara J.; Franz, Otto G.; Wasserman, Laurence H.; Jones, Burton F.; Latham, David W.; Torres, Guillermo; Stefanik, Robert P.

    1998-01-01

    HD 98800 is a system of four stars, and it has a large infrared excess that is thought to be due to a dust disk within the system. In this paper we present new astrometric observations made with Hipparcos, as well as photometry from Hubble Space Telescope WFPC2 images. Combining these observations and reanalyzing previous work allow us to estimate the age and masses of the stars in the system. Uncertainty in these ages and masses results from uncertainty in the temperatures of the stars and any reddening they may have. We find that HD 98800 is most probably about 10 Myr old, although it may be as young as 5 Myr or as old as 20 Myr old. The stars in HD 98800 appear to have metallicities that are about solar. An age of 10 Myr means that HD 98800 is a member of the post T Tauri class of objects, and we argue that the stars in HD 98800 can help us understand why post T Tauris have been so elusive, HD 98800 may have formed in the Centaurus star-forming region, but it is extraordinary in being so young and yet so far from where it was born.

  19. Optical variability in the unusual K5 V infrared-excess star HD 98800

    NASA Technical Reports Server (NTRS)

    Henry, Gregory W.; Hall, Douglas S.

    1994-01-01

    The dusty infrared-excess star HD 98800 (K5 V) was observed for several weeks in the spring of 1993 by the Vanderbilt/Tennessee State 0.4 m automatic photoelectric telescope. It was found to be a variable star with an amplitude of 0.07 mag in V and a period of 14.7 days. We show, by comparison with other chromospherically active variable stars and constant stars with good observational histories, that the Rossby number for HD 98800, determined to be 0.30, places it well within the regime of stars whose convective envelopes and rotation rates combine to drive a magnetic dynamo strong enough to generate photometrically observable starspots. The light curve suggests at least two large spots at somewhat different longitudes on HD 98800, one of which could be as large as 16 deg in radius.

  20. THE CHEMICAL COMPOSITIONS OF VERY METAL-POOR STARS HD 122563 AND HD 140283: A VIEW FROM THE INFRARED

    SciTech Connect

    Afşar, Melike; Sneden, Christopher; Kim, Hwihyun E-mail: chris@astro.as.utexas.edu E-mail: hwihyun@astro.as.utexas.edu E-mail: afrebel@mit.edu; and others

    2016-03-10

    From high resolution (R ≃ 45,000), high signal-to-noise ratio (S/N > 400) spectra gathered with the Immersion Grating Infrared Spectrograph (IGRINS) in the H and K photometric bands, we have derived elemental abundances of two bright, well-known metal-poor halo stars: the red giant HD 122563 and the subgiant HD 140283. Since these stars have metallicities approaching [Fe/H] = −3, their absorption features are generally very weak. Neutral-species lines of Mg, Si, S and Ca are detectable, as well as those of the light odd-Z elements Na and Al. The derived IR-based abundances agree with those obtained from optical-wavelength spectra. For Mg and Si the abundances from the infrared transitions are improvements to those derived from shorter wavelength data. Many useful OH and CO lines can be detected in the IGRINS HD 122563 spectrum, from which derived O and C abundances are consistent to those obtained from the traditional [O i] and CH features. IGRINS high resolutions H- and K-band spectroscopy offers promising ways to determine more reliable abundances for additional metal-poor stars whose optical features are either not detectable, or too weak, or are based on lines with analytical difficulties.

  1. The Chemical Compositions of Very Metal-poor Stars HD 122563 and HD 140283: A View from the Infrared

    NASA Astrophysics Data System (ADS)

    Afşar, Melike; Sneden, Christopher; Frebel, Anna; Kim, Hwihyun; Mace, Gregory N.; Kaplan, Kyle F.; Lee, Hye-In; Oh, Heeyoung; Sok Oh, Jae; Pak, Soojong; Park, Chan; Pavel, Michael D.; Yuk, In-Soo; Jaffe, Daniel T.

    2016-03-01

    From high resolution (R ≃ 45,000), high signal-to-noise ratio (S/N > 400) spectra gathered with the Immersion Grating Infrared Spectrograph (IGRINS) in the H and K photometric bands, we have derived elemental abundances of two bright, well-known metal-poor halo stars: the red giant HD 122563 and the subgiant HD 140283. Since these stars have metallicities approaching [Fe/H] = -3, their absorption features are generally very weak. Neutral-species lines of Mg, Si, S and Ca are detectable, as well as those of the light odd-Z elements Na and Al. The derived IR-based abundances agree with those obtained from optical-wavelength spectra. For Mg and Si the abundances from the infrared transitions are improvements to those derived from shorter wavelength data. Many useful OH and CO lines can be detected in the IGRINS HD 122563 spectrum, from which derived O and C abundances are consistent to those obtained from the traditional [O i] and CH features. IGRINS high resolutions H- and K-band spectroscopy offers promising ways to determine more reliable abundances for additional metal-poor stars whose optical features are either not detectable, or too weak, or are based on lines with analytical difficulties.

  2. Orbital Configurations and Dynamical Stability of Multiplanet Systems around Sun-like Stars HD 202206, 14 Herculis, HD 37124, and HD 108874

    NASA Astrophysics Data System (ADS)

    Goździewski, Krzysztof; Konacki, Maciej; Maciejewski, Andrzej J.

    2006-07-01

    We perform a dynamical analysis of the recently published radial velocity (RV) measurements of a few solar-type stars that host multiple Jupiter-like planets. In particular, we reanalyze the data for HD 202206, 14 Her, HD 37124, and HD 108874. We derive dynamically stable configurations that reproduce the observed RV signals, using GAMP (the genetic algorithm with MEGNO penalty). GAMP relies on N-body dynamics and makes use of genetic algorithms merged with a stability criterion. For this purpose, we use the maximal Lyapunov exponent computed with the dynamical fast indicator MEGNO. Through a dynamical analysis of the phase space in a neighborhood of the obtained best-fit solutions, we derive meaningful limits on the parameters of the planets. We demonstrate that GAMP is especially well suited to the analysis of the RV data that only partially cover the longest orbital period and/or are related to multiplanet configurations involved in low-order mean motion resonances (MMRs). Our analysis reveals a presence of a second Jupiter-like planet in the 14 Her system (14 Her c) that is involved in a 3:1 or 6:1 MMR with the known companion 14 Her b. We also show that the dynamics of the HD 202206 system may be qualitatively different when coplanar and mutually inclined orbits of the companions are considered. We demonstrate that the two outer planets in the HD 37124 system may reside in a close neighborhood of the 5:2 MMR. Our results confirm that the HD 108874 system may be very close to a, or locked in an exact, 4:1 MMR.

  3. Active phenomena in the pre-main sequence Herbig Ae star HD 163296

    NASA Technical Reports Server (NTRS)

    Catala, C.; Praderie, F.; Simon, T.; Talavera, A.; The, P. S.

    1989-01-01

    Observations by IUE of the short-term variability of the Mg II and Ca II resonance lines in the Herbig Ae star HD 163296 are presented. Evidence that these lines show a phenomenon of rotational modulation, similar to the one observed in AB Aur, another Herbig Ae star is found. The variations in the spectrum of HD 163296 are even more conspicuous than in the spectrum of AB Aur. Magnetically structured winds may thus be a widespread phenomenon among the pre-main sequence Herbig Ae/Be stars.

  4. Variability of Disk Emission in Pre-main-sequence and Related Stars. I. HD 31648 and HD 163296: Isolated Herbig Ae Stars Driving Herbig-Haro Flows

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Carpenter, William J.; Kimes, Robin L.; Wilde, J. Leon; Lynch, David K.; Russell, Ray W.; Rudy, Richard J.; Mazuk, Stephan M.; Venterini, Catherine C.; Puetter, Richard C.; Grady, Carol A.; Polomski, Elisha F.; Wisnewski, John P.; Brafford, Suellen M.; Hammel, H. B.; Perry, R. Brad

    2008-01-01

    Infrared photometry and spectroscopy covering a time span of a quarter-century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically in its inner disk region, with the exception of a major increase in emitted flux in a broad wavelength region centered near 3 micron in 2002. In contrast, HD 31648 has exhibited sporadic changes in the entire 3-13 micron region throughout this span of time. In both stars, the changes in the 1-5 micron flux indicate structural changes in the region of the disk near the dust sublimation zone, possibly causing its distance from the star to vary with time. Repeated thermal cycling through this region will result in the preferential survival of large grains, and an increase in the degree of crystallinity. The variability observed in these objects has important consequences for the interpretation of other types of observations. For example, source variability will compromise models based on interferometry measurements unless the interferometry observations are accompanied by nearly simultaneous photometric data.

  5. Variability of Disk Emission in Pre-Main Sequence and Related Stars. I. HD 31648 and HD 163296 - Isolated Herbig Ae Stars Driving Herbig-Haro Flows

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Carpenter, William J.; Kimes, Robin L.; Lynch, David K.; Russell, Ray W.; Rudy, Richard J.; Mazuk, Stephan M.; Venturini, Catherine C.; Puetter, Richard C.; Grady, Carol A.; Polomski, Elisha F.; Wisnewski, John P.; Brafford, Suellen M.; Hammel, H. B.; Perry, Raleigh B.

    2007-01-01

    Infrared photometry and spectroscopy covering a time span of a quarter century are presented for HD 31648 (MWC 480) and HD 163296 (MWC 275). Both are isolated Herbig Ae stars that exhibit signs of active accretion, including driving bipolar flows with embedded Herbig-Haro (HH) objects. HD 163296 was found to be relatively quiescent photometrically in its inner disk region, with the exception of a major increase in emitted flux in a broad wavelength region centered near 3 pm in 2002. In contrast, HD 31648 has exhibited sporadic changes in the entire 3-13 pm region throughout this span of time. In both stars the changes in the 1-5 pm flux indicate structural changes in the region of the disk near the dust sublimation zone, possibly causing its distance from the star to vary with time. Repeated thermal cycling through this region will result in the preferential survival of large grains, and an increase in the degree of crystallinity. The variability observed in these objects has important consequences for the interpretation of other types of observations. For example, source variability will compromise models based on interferometry measurements unless the interferometry observations are accompanied by nearly-simultaneous photometric data.

  6. Neutron-capture nucleosynthesis in HdC stars: the case of HE 1015-2050

    NASA Astrophysics Data System (ADS)

    Goswami, Aruna; Karinkuzhi, Drisya

    Hydrogen-deficient carbon (HdC) stars and R Coronae Borealis (RCB) type stars form a rare class of carbon-rich supergiants. A fraction of these stars in our Galaxy are known to exhibit strong features of light neutron-capture elements such as Sr, Y and Zr usually attributed to the weak component of the s-process. These stars are believed to be in a very short-lived evolutionary phase; hence, their ejecta could have significantly contributed to chemical enrichment in the Galaxy. From medium-resolution spectral analyses of faint high latitude carbon (FHLC) stars of Hamburg/ESO survey Goswami et al. (2010) have added a new member HE 1015-2050, to this rare class. This object is found to exhibit anomalously strong features of Sr in its spectrum. Possible scenarios that might have led to the formation of this object are discussed in the light of existing scenarios of HdC star formation.

  7. The peculiar A star HD 43819 - A photographic region line-identification study

    NASA Technical Reports Server (NTRS)

    Adelman, S. J.

    1985-01-01

    A line identification study of the sharp-lined silicon star HD 43819 has been performed for the photographic region 3759-4924 A. Comparison of this star's spectrum with those of other silicon stars shows that it shares many of their apparent abundance anomalies. The TiII, CrII, FeI, and FeII spectra are well represented while the singly ionized rare earths are represented by at best a few lines per species.

  8. STEREO observations of HD90386 (RX Sex): a δ-Scuti or a hybrid star?

    NASA Astrophysics Data System (ADS)

    Ozuyar, D.; Stevens, I. R.; Whittaker, G.; Sangaralingam, V.

    2016-04-01

    HD90386 is a rarely studied bright A2V type δ Scuti star (V = 6.66 mag). It displays short-term light curve variations which are originated due to either a beating phenomenon or a non-periodic variation. In this paper, we presented high-precision photometric data of HD90386 taken by the STEREO satellite between 2007 and 2011 to shed light on its internal structure and evolution stage. From the frequency analysis of the four-year data, we detected that HD90386 had at least six different frequencies between 1 and 15 c d-1. The most dominant frequencies were found at around 10.25258 c d-1 (A ∼ 1.92 mmag) and 12.40076 c d-1 (A ∼ 0.61 mmag). Based on the ratio between these frequencies, the star was considered as an overtone pulsator. The variation in pulsation period over 35 years was calculated to be dP/Pdt = 5.39(2) x 10-3 yr-1. Other variabilities at around 1.0 c d-1 in the amplitude spectrum of HD90386 were also discussed. In order to explain these variabilities, possible rotational effects and γ Dor type variations were focused. Consequently, depending on the rotation velocity of HD90386, we speculated that these changes might be related to γ Dor type high-order g-modes shifted to the higher frequencies and that HD90386 might be a hybrid star.

  9. Chromospherically active stars. II - HD 82558, a young single BY Draconis variable

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Bopp, Bernard W.; Africano, John L.; Goodrich, Bret D.; Palmer, Leigh Hunter

    1986-01-01

    It is presently noted that the HD 82558 chromospherically active star is a young and rapidly rotating K2 V single BY Draconis variable with very strong far-UV emission features and an H-alpha line filled to the continuum level by emission. HD 82558 has constant velocity and is not a member of the Hyades Supercluster. Its light curve behavior, which appears to have been stable for several hundred rotation cycles, is reminiscent of that of the young, rapidly rotating, single K V variable H II 1883 in the Pleiades; this stability may be characteristic of young, single, chromospherically active stars.

  10. Radial-Velocity Analysis of the Post-AGB Star, HD101584

    NASA Astrophysics Data System (ADS)

    Díaz, F.; Hearnshaw, J.; Rosenzweig, P.; Guzman, E.; Sivarani, T.; Parthasarathy, M.

    2007-08-01

    This project concerns the analysis of the periodicity of the radial velocity of the peculiar emission-line supergiant star HD 101584 (F0 Ia), and also we propose a physical model to account for the observations. From its peculiarities, HD 101584 is a star that is in the post-AGB phase. This study is considered as a key to clarify the multiple aspects related with the evolution of the circum-stellar layer associated with this star's last phase. The star shows many lines with P Cygni profiles, including H-alpha, Na D lines in the IR Ca triplet, indicating a mass outflow. For HD 101584 we have performed a detailed study of its radial-velocity variations, using both emission and absorption lines over a wide range of wavelength. We have analyzed the variability and found a periodicity for all types of lines of 144 days, which must arise from the star's membership in a binary system. The data span a period of five consecutive years and were obtained using the 1-m telescope of Mt John Observatory, in New Zealand., with the echelle and Hercules high resolution spectrographs and CCD camera. HD101584 is known to be an IRAS source, and our model suggests it is a proto-planetary nebula, probably with a bipolar outflow and surrounded by a dusty disk as part of a binary system. We have found no evidence for HD101584 to contain a B9 star as found by Bakker et al (1996). A low resolution IUE spectrum shows the absence of any strong UV continuum that would be expected for a B star to be in this system.

  11. Is there a compact companion orbiting the late O-type binary star HD 164816?

    NASA Astrophysics Data System (ADS)

    Trepl, L.; Hambaryan, V. V.; Pribulla, T.; Tetzlaff, N.; Chini, R.; Neuhäuser, R.; Popov, S. B.; Stahl, O.; Walter, F. M.; Hohle, M. M.

    2012-12-01

    We present a multi-wavelength (X-ray, γ-ray, optical and radio) study of HD 164816, a late O-type X-ray detected spectroscopic binary. X-ray spectra are analysed and the X-ray photon arrival times are checked for pulsation. In addition, newly obtained optical spectroscopic monitoring data on HD 164816 are presented. They are complemented by available radio data from several large-scale surveys as well as the Fermi γ-ray data from its Large Area Telescope. We report the detection of a low energy excess in the X-ray spectrum that can be described by a simple absorbed blackbody model with a temperature of ˜50 eV as well as a 9.78 s pulsation of the X-ray source. The soft X-ray excess, the X-ray pulsation and the kinematical age would all be consistent with a compact object like a neutron star as companion to HD 164816. The size of the soft X-ray excess emitting area is consistent with a circular region with a radius of about 7 km, typical for neutron stars, while the emission measure (EM) of the remaining harder emission is typical for late O-type single or binary stars. If HD 164816 includes a neutron star born in a supernova, this supernova should have been very recent and should have given the system a kick, which is consistent with the observation that the star HD 164816 has a significantly different radial velocity than the cluster mean. In addition we confirm the binarity of HD 164816 itself by obtaining an orbital period of 3.82 d, projected masses m1sin3i = 2.355(69) M⊙, m2sin3i = 2.103(62) M⊙ apparently seen at low inclination angle, determined from high-resolution optical spectra.

  12. Pulsation tomography of rapidly oscillating Ap stars. Resolving the third dimension in peculiar pulsating stellar atmospheres

    NASA Astrophysics Data System (ADS)

    Ryabchikova, T.; Sachkov, M.; Kochukhov, O.; Lyashko, D.

    2007-10-01

    Aims:We present detailed analysis of the vertical pulsation mode cross-section in ten rapidly oscillating Ap (roAp) stars based on spectroscopic time-series observations. The aim of this analysis is to derive from observations a complete picture of how the amplitude and phase of magnetoacoustic waves depend on depth. Methods: We use the unique properties of roAp stars, in particular chemical stratification, to resolve the vertical structure of p-modes. Our approach consists of characterising pulsational behaviour of a carefully chosen, but extensive sample of spectral lines. We analyse the resulting amplitude-phase diagrams and interpret observations in terms of pulsation wave propagation. Results: We find common features in the pulsational behaviour of roAp stars. Within a sample of representative elements the lowest amplitudes are detected for Eu ii (and Fe in 33 Lib and in HD 19918), then pulsations go through the layers where Hα core, Nd, and Pr lines are formed. There RV amplitude reaches its maximum, and after that decreases in most stars. The maximum RV of the second REE ions is always delayed relative to the first ions. The largest phase shifts are detected in Tb iii and Th iii lines. Pulsational variability of the Th iii lines is detected here for the first time. The Y ii lines deviate from this picture, showing even lower amplitudes than Eu ii lines but half a period phase shift relative to other weakly pulsating lines. We measured an extra broadening, equivalent to a macroturbulent velocity from 4 to 11-12 km s-1 (where maximum values are observed for Tb iii and Th iii lines), for pulsating REE lines. The surface magnetic field strength is derived for the first time for three roAp stars: HD 9289 (2 kG), HD 12932 (1.7 kG), and HD 19918 (1.6 kG). Conclusions: The roAp stars exhibit similarity in the depth-dependence of pulsation phase and amplitude, indicating similar chemical stratification and comparable vertical mode cross-sections. In general

  13. A Search for Planetary Transits of the Star HD 187123 by Spot Filter CCD Differential Photometry

    NASA Technical Reports Server (NTRS)

    Castellano, T.; DeVincenzi, D. (Technical Monitor)

    2000-01-01

    A novel method for performing high precision, time series CCD differential photometry of bright stars using a spot filter, is demonstrated. Results for several nights of observing of the 51 Pegasi b-type planet bearing star HD 187123 are presented. Photometric precision of 0.0015 - 0.0023 magnitudes is achieved. No transits are observed at the epochs predicted from the radial velocity observation. If the planet orbiting HD 187123 at 0.0415 AU is an inflated Jupiter similar in radius to HD 209458b it would have been detected at the greater than 6(sigma), level if the orbital inclination is near 90 degrees and at the greater than 3(sigma), level if the orbital inclination is as small as 82.7 degrees.

  14. The compact Hα emitting regions of the Herbig Ae/Be stars HD 179218 and HD 141569 from CHARA spectro-interferometry

    NASA Astrophysics Data System (ADS)

    Mendigutía, I.; Oudmaijer, R. D.; Mourard, D.; Muzerolle, J.

    2017-01-01

    This work presents CHARA/VEGA Hα spectro-interferometry (R ˜ 6000, and λ/2B ˜ 1 mas) of HD 179218 and HD 141569, doubling the sample of Herbig Ae/Be (HAeBe) stars for which this type of observations is available so far. The observed Hα emission is spatially unresolved, indicating that the size of the Hα emitting region is smaller than ˜0.21 and 0.12 au for HD 179218 and HD 141529 (˜15 and 16 R*, respectively). This is smaller than for the two other HAeBes previously observed with the same instrumentation. Two different scenarios have been explored in order to explain the compact line emitting regions. A hot, several thousand K, blackbody disc is consistent with the observations of HD 179218 and HD 141569. Magnetospheric accretion (MA) is able to reproduce the bulk of the Hα emission shown by HD 179218, confirming previous estimates from MA shock modelling with a mass accretion rate of 10-8 M⊙ yr-1, and an inclination to the line of sight between 30° and 50°. The Hα profile of HD 141569 cannot be fitted from MA due to the high rotational velocity of this object. Putting the CHARA sample together, a variety of scenarios is required to explain the Hα emission in HAeBe stars - compact or extended, discs, accretion, and winds - in agreement with previous Brγ spectro-interferometric observations.

  15. Recent photometric behavior of the unusual Be star HD 45677 = FS Canis Majoris

    NASA Astrophysics Data System (ADS)

    Halbedel, Elaine M.

    1989-11-01

    Four years of recent photometry for the unusual Be star HD 45677 = FS CMa is presented. The star is shown to vary actively during the time period observed. A quasi-periodicity of 296.5 days has been found for the recent data but does not entirely satisfy historical magnitudes. The feasibility of several models is discussed and a spectrum centered on H-alpha is presented.

  16. Stellar diameters and temperatures - VI. High angular resolution measurements of the transiting exoplanet host stars HD 189733 and HD 209458 and implications for models of cool dwarfs

    NASA Astrophysics Data System (ADS)

    Boyajian, Tabetha; von Braun, Kaspar; Feiden, Gregory A.; Huber, Daniel; Basu, Sarbani; Demarque, Pierre; Fischer, Debra A.; Schaefer, Gail; Mann, Andrew W.; White, Timothy R.; Maestro, Vicente; Brewer, John; Lamell, C. Brooke; Spada, Federico; López-Morales, Mercedes; Ireland, Michael; Farrington, Chris; van Belle, Gerard T.; Kane, Stephen R.; Jones, Jeremy; ten Brummelaar, Theo A.; Ciardi, David R.; McAlister, Harold A.; Ridgway, Stephen; Goldfinger, P. J.; Turner, Nils H.; Sturmann, Laszlo

    2015-02-01

    We present direct radii measurements of the well-known transiting exoplanet host stars HD 189733 and HD 209458 using the CHARA Array interferometer. We find the limb-darkened angular diameters to be θLD = 0.3848 ± 0.0055 and 0.2254 ± 0.0072 mas for HD 189733 and HD 209458, respectively. HD 189733 and HD 209458 are currently the only two transiting exoplanet systems where detection of the respective planetary companion's orbital motion from high-resolution spectroscopy has revealed absolute masses for both star and planet. We use our new measurements together with the orbital information from radial velocity and photometric time series data, Hipparcos distances, and newly measured bolometric fluxes to determine the stellar effective temperatures (Teff = 4875 ± 43, 6092 ± 103 K), stellar linear radii (R* = 0.805 ± 0.016, 1.203 ± 0.061 R⊙), mean stellar densities (ρ* = 1.62 ± 0.11, 0.58 ± 0.14 ρ⊙), planetary radii (Rp = 1.216 ± 0.024, 1.451 ± 0.074 RJup), and mean planetary densities (ρp = 0.605 ± 0.029, 0.196 ± 0.033 ρJup) for HD 189733b and HD 209458b, respectively. The stellar parameters for HD 209458, an F9 dwarf, are consistent with indirect estimates derived from spectroscopic and evolutionary modelling. However, we find that models are unable to reproduce the observational results for the K2 dwarf, HD 189733. We show that, for stellar evolutionary models to match the observed stellar properties of HD 189733, adjustments lowering the solar-calibrated mixing-length parameter to αMLT =1.34 need to be employed.

  17. The Environment of the Optically Brightest Herbig Ae Star, HD 104237

    NASA Astrophysics Data System (ADS)

    Grady, C. A.; Woodgate, B.; Torres, Carlos A. O.; Henning, Th.; Apai, D.; Rodmann, J.; Wang, Hongchi; Stecklum, B.; Linz, H.; Williger, G. M.; Brown, A.; Wilkinson, E.; Harper, G. M.; Herczeg, G. J.; Danks, A.; Vieira, G. L.; Malumuth, E.; Collins, N. R.; Hill, R. S.

    2004-06-01

    We investigate the environment of the nearest Herbig Ae star, HD 104237, with a multiwavelength combination of optical coronagraphic, near-IR, and mid-IR imaging supported by optical, UV, and far-ultraviolet spectroscopy. We confirm the presence of T Tauri stars associated with the Herbig Ae star HD 104237, noted by Feigelson et al. We find that two of the stars within 15" of HD 104237 have IR excesses, potentially indicating the presence of circumstellar disks, in addition to the Herbig Ae star itself. We derive a new spectral type of A7.5Ve-A8Ve for HD 104237 and find log(L/Lsolar)=1.39. With these data, HD 104237 has an age of t~5 Myr, in agreement with the estimates for the other members of the association. HD 104237 is still actively accreting, with a conspicuous UV/far-UV excess seen down to 1040 Å, and is driving a bipolar microjet termed HH 669. This makes it the second, older Herbig Ae star now known to have a microjet. The presence of the microjet enables us to constrain the circumstellar disk to r<=0.6" (70 AU) with an inclination angle of i=18deg+14-11 from pole-on. The absence of a spatially extended continuum and fluorescent H2 emission near Lyα is in agreement with the prediction of shadowed disk models for the IR spectral energy distribution. With the high spatial density of disks in this group of stars, proximity, and minimal reddening, HD 104237 and its companions should serve as ideal laboratories for probing the comparative evolution of planetary systems. Based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA Contract NAS5-26555. Based on observations made with ESO's TIMMI2 camera on La Silla, Chile, under program ID 71.C-0438. Based on observations made with the ESO VLT and the Near-IR Adaptive Optics System+Conica, under program ID 71.C-0143. Based on observations made under the ON-ESO agreement for the joint operation of the 1.52 m

  18. First discovery of a magnetic field in a main-sequence δ Scuti star: the Kepler star HD 188774

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Lampens, P.

    2015-11-01

    The Kepler space mission provided a wealth of δ Sct-γ Dor hybrid candidates. While some may be genuine hybrids, others might be misclassified due to the presence of a binary companion or to rotational modulation caused by magnetism and related surface inhomogeneities. In particular, the Kepler δ Sct-γ Dor hybrid candidate HD 188774 shows a few low frequencies in its light and radial velocity curves, whose origin is unclear. In this work, we check for the presence of a magnetic field in HD 188774. We obtained two spectropolarimetric measurements with an Echelle SpectroPolarimetric Device for the Observation of Stars (ESPaDOnS) at Canada-France-Hawaii Telescope. The data were analysed with the least-squares deconvolution (LSD) method. We detected a clear magnetic signature in the Stokes V LSD profiles. The origin of the low frequencies detected in HD 188774 is therefore most probably the rotational modulation of surface spots possibly related to the presence of a magnetic field. Consequently, HD 188774 is not a genuine hybrid δ Sct-γ Dor star, but the first known magnetic main-sequence δ Sct star. This makes it a prime target for future asteroseismic and spot modelling. This result casts new light on the interpretation of the Kepler results for other δ Sct-γ Dor hybrid candidates.

  19. HOST STAR PROPERTIES AND TRANSIT EXCLUSION FOR THE HD 38529 PLANETARY SYSTEM

    SciTech Connect

    Henry, Gregory W.; Kane, Stephen R.; Von Braun, Kaspar; Ciardi, David R.; Hinkel, Natalie R.; Wang, Sharon X.; Wright, Jason T.; Mahadevan, Suvrath; Pilyavsky, Genady; Boyajian, Tabetha S.; Fischer, Debra A.; Dragomir, Diana; Farrington, Chris; Howard, Andrew W.; Jensen, Eric; Laughlin, Gregory

    2013-05-10

    The transit signature of exoplanets provides an avenue through which characterization of exoplanetary properties may be undertaken, such as studies of mean density, structure, and atmospheric composition. The Transit Ephemeris Refinement and Monitoring Survey is a program to expand the catalog of transiting planets around bright host stars by refining the orbits of known planets discovered with the radial velocity technique. Here we present results for the HD 38529 system. We determine fundamental properties of the host star through direct interferometric measurements of the radius and through spectroscopic analysis. We provide new radial velocity measurements that are used to improve the Keplerian solution for the two known planets, and we find no evidence for a previously postulated third planet. We also present 12 years of precision robotic photometry of HD 38529 that demonstrate the inner planet does not transit and the host star exhibits cyclic variations in seasonal mean brightness with a timescale of approximately six years.

  20. The nature of the light variability of magnetic Of?p star HD 191612

    NASA Astrophysics Data System (ADS)

    Krtička, J.

    2016-10-01

    Context. A small fraction of hot OBA stars host global magnetic fields with field strengths of the order of 0.1-10 kG. This leads to the creation of persistent surface structures (spots) in stars with sufficiently weak winds as a result of the radiative diffusion. These spots become evident in spectroscopic and photometric variability. This type of variability is not expected in stars with strong winds, where the wind inhibits the radiative diffusion. Therefore, a weak photometric variability of the magnetic Of?p star HD 191612 is attributed to the light absorption in the circumstellar clouds. Aims: We study the nature of the photometric variability of HD 191612. We assume that the variability results from variable wind blanketing induced by surface variations of the magnetic field tilt and modulated by stellar rotation. Methods: We used our global kinetic equilibrium (NLTE) wind models with radiative force determined from the radiative transfer equation in the comoving frame (CMF) to predict the stellar emergent flux. Our models describe the stellar atmosphere in a unified manner and account for the influence of the wind on the atmosphere. The models are calculated for different wind mass-loss rates to mimic the effect of magnetic field tilt on the emergent fluxes. We integrate the emergent fluxes over the visible stellar surface for individual rotational phases, and calculate the rotationally modulated light curve of HD 191612. Results: The wind blanketing that varies across surface of HD 191612 is able to explain a part of the observed light variability in this star. The mechanism is able to operate even at relatively low mass-loss rates. The remaining variability is most likely caused by the flux absorption in circumstellar clouds. Conclusions: The variable wind blanketing is an additional source of the light variability in massive stars. The presence of the rotational light variability may serve as a proxy for the magnetic field.

  1. The CoRoT chemical peculiar target star HD 49310

    NASA Astrophysics Data System (ADS)

    Paunzen, E.; Fröhlich, H.-E.; Netopil, M.; Weiss, W. W.; Lüftinger, T.

    2015-02-01

    Context. The magnetic chemically peculiar (CP) stars of the upper main sequence are well-suited laboratories for investigating the influence of local magnetic fields on the stellar surface because they produce inhomogeneities (spots) that can be investigated in detail as the star rotates. Aims: We studied the inhomogeneous surface structure of the CP2 star HD 49310 based on high-quality CoRoT photometry obtained during 25 days. The data have nearly no gaps. This analysis is similar to a spectroscopic Doppler-imaging analysis, but it is not a tomographic method. Methods: We performed detailed light-curve fitting in terms of stationary circular bright spots. Furthermore, we derived astrophysical parameters with which we located HD 49310 within the Hertzsprung-Russell diagram. We also investigated the possible connection of this star to the nearby young open cluster NGC 2264. Results: With a Bayesian technique, we produced a surface map that shows six bright spots. After removing some artefacts, the residuals of the observed and synthetic photometric data are ± 0.123 mmag. The rotational period of the star is P = 1.91909 ± 0.00001 days. Our photometric observations therefore cover about 13 full rotational cycles. Three spots are very large with diameters of ≃ 40deg. The spots are brighter by 40% than the unperturbed stellar photosphere. Conclusions: HD 49310 is a classical silicon (CP2) star with a mass of about 3 M⊙. It is not a member of NGC 2264. Our analysis shows the potential of using high-quality photometric data to analyse the surface structure of CP stars. A comprehensive analysis of similar archival data, preferrably from space missions, would contribute significantly to our understanding of surface phenomena of CP stars and their temporal evolution. The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria, Belgium, Brazil, Germany, and Spain.

  2. The new Be-type star HD 147196 in the Rho Ophiuchi dark cloud region

    NASA Technical Reports Server (NTRS)

    The, P. S.; Perez, M. R.; De Winter, D.; Van Den Ancker, M. E.

    1993-01-01

    The newly discovered hot-emission line star, HD 147196 in the Rho Oph dark cloud region was observed spectroscopically and photometrically and high and low resolution IUE spectra were obtained. The finding of Irvine (1990) that this relatively bright star show its H-alpha-line in emission is confirmed. Previous H-alpha-surveys of the Rho Oph star-forming region did not detect HD 147196 as an H-alpha-emission star, meaning that it must recently be very active and has perhaps transformed itself from a B-type star at shell phase to a Be-phase. The Mg II h + k resonance lines are in absorption and they appear to be interstellar in nature, which means that either the abundance of Mg in the extended atmosphere of the star is low or that the shell is not extended enough to produce emission lines of Mg II. Photometric observations of this B8 V type star do not show any variations during at least the years covered by our monitoring or any excess of NIR radiation in its spectral energy distribution up to the M-passband at 4.8 microns.

  3. Radio continuum observations of the Herbig Ae/Be stars HD 163296 and HR 5999

    NASA Technical Reports Server (NTRS)

    Brown, D. A.; Perez, M. R.; Yusef-Zadeh, F.

    1993-01-01

    Very Large Array (VLA) observations of the two bright Herbig Ae/Be stars HD 163296 and HR 5999 have been carried out at lambda 3.6 and 20 cm. We report the detection of a radio source at lambda 3.6 cm that may be associated with HD 163296. From the peak flux density of 0.39 mJy/beam area, we estimate a mass-loss rate of 1.8 x 10(exp -8) solar mass/yr if the flux is due to free-free emission in an ionized wind with spherical symmetry, assuming a terminal wind velocity of 200 km/s. HR 5999 was not detected at either wavelength. We discuss the results in terms of the stellar-driven and accretion-driven scenarios for line and wind formation in Herbig Ae/Be stars.

  4. Abundances in the atmosphere of the metal-rich planet-host star HD 77338

    NASA Astrophysics Data System (ADS)

    Kushniruk, I. O.; Pavlenko, Ya. V.; Jenkins, J. S.; Jones, H. R. A.

    2014-12-01

    Abundances of Fe, Si, Ni, Ti, Na, Mg, Cu, Zn, Mn, Cr and Ca in the atmosphere of the K-dwarf HD 77338 are determined and discussed. HD 77338 hosts a hot Uranus-like planet and is currently the most metal-rich single star to host any planet. Determination of abundances was carried out in the framework of a self-consistent approach developed by Pavlenko et al. (2012). Abundances were computed iteratively by the ABEL8 code, and the process converged after 4 iterations. We find that most elements follow the iron abundance, however some of the iron peak elements are found to be over-abundant in this star.

  5. Different regions of line formation in the envelope of the early emission line star HD 190073

    NASA Technical Reports Server (NTRS)

    Ringuelet, A. E.; Rovira, M.; Cidale, L.; Sahade, J.

    1987-01-01

    A description is presented of the spectral features that characterize the spectrum of HD 190073 both in the photographic region (360-660 nm), and in the IUE UV (115-320 nm). A number of different types of profiles can be distinguished, and this seems to imply that many different 'broad' regions of line formation coexist in the extended envelope of the star, including regions with densities differing in several orders of magnitude.

  6. Fe-Group Elements in the Metal-Poor Star HD 84937: Abundances and their Implications

    NASA Astrophysics Data System (ADS)

    Sneden, Chris; Cowan, John J.; Kobayashi, Chiaki; Pignatari, Marco; Lawler, James E.; Den Hartog, Elizabeth; Wood, Michael P.

    2016-01-01

    We have derived accurate relative abundances of the Fe-group elements Sc through Zn in the very metal-poor main-sequence turnoff star HD 84937. For this study we analyzed high resolution, high signal-to-noise HST/STIS and VLT/UVES spectra over a total wavelength range 2300-7000 Å. We employed only recent or newly-applied reliable laboratory transition data for all species. Abundances from more than 600 lines of non-Fe species were combined with about 550 Fe lines in HD 84937 to yield abundance ratios of high precision. From parallel analyses of solar photospheric spectra we also derived new solar abundances of these elements. This in turn yielded internally-consistent relative HD 84937 abundances with respect to the Sun. For seven of the ten Fe-group elements the HD 84937 abundances were from both neutral and ionized transitions. In all of these cases the neutral and ionized species yield the same abundances within the measurement uncertainties. Therefore standard Saha ionization balance appears to hold in the HD 84937 atmosphere. We derived metallicity [Fe/H] = -2.32 with sample standard deviation of 0.06. Solid evidence is seen for departures from the solar abundance mix in HD 84937, for example [Co/Fe] = +0.14, [Cu/Fe] = -0.83, and <[Sc,Ti,V/Fe]> = +0.31. Combining our Sc, Ti, and V abundances for this star with those from large-sample spectroscopic surveys suggests that these elements are positively correlated in stars with [Fe/H] < -2. HD 84937 is unusually enriched in Sc, Ti, and V. Our analysis strongly suggests that different types of supernovae with a large scatter of explosion energies and asymmetries contributed to the creation of the Fe-group elements early in the Galaxy's history.This work has been supported in part by NASA grant NNX10AN93G (J.E.L.), by NSF grants AST-1211055 (J.E.L.), AST-1211585 (C.S.), PHY-1430152 (through JINA, J.J.C. and M.P.), EU MIRGCT-2006-046520 (M.P.), and by the ``Lendlet-2014'' Programme of the Hungarian Academy of

  7. Observational survey of the puzzling star HD 179821: Photometric variations and period analysis

    NASA Astrophysics Data System (ADS)

    Le Coroller, H.; Lèbre, A.; Gillet, D.; Chapellier, E.

    2003-03-01

    From new photometric observations (UBVRI), we present the characteristic features of the light variations of the evolved star HD 179821 (= SAO 124414 = IRAS 19114+0002). Our data, collected through 1999 and 2000, have been combined together with previous photometric measurements available in the literature. Thus, a long term V-light curve (gathering more than 10 years of observations for HD 179821) has been composed. We have analysed it with the Fourier transform method. Two main frequencies are present in the resulting power spectrum, reflecting a dominant bimodal pulsator behavior. A long term phenomenon is also found, but it is not possible to decide whether it is periodic. The Fourier analysis has also been applied on two other filters (U and B) and confirms the detected frequencies. On the basis of our period analysis, we discuss the nature of HD 179821: low-mass post-AGB star or high-mass star. based on observations carried out at the Observatoire de Haute Provence, France, operated by the Centre National de la Recherche Scientifique (CNRS).

  8. Detection of a white dwarf companion to the Hyades stars HD 27483

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1993-01-01

    We observed with IUE a white dwarf (WD) companion to the Hyades F6 V binary stars HD 27483. This system is known to be a close binary of two nearly equal stars with an orbital period of 3.05 days. Our IUE observations revealed the presence of a third star, a white dwarf with an effective temperature of 23,000 +/- 1000 K and a mass of approximately 0.6 solar mass. Its presence in the Hyades cluster with a known age permits me to derive the mass of its progenitor, which must have been about 2.3 solar masses. The presence of the white dwarf in a binary system opens the possibility that some of the envelope material, which was expelled by the WD progenitor, may have been collected by the F6 stars. We may thus be able to study abundance anomalies of the WD progenitor with known mass on the surface of the F6 companions.

  9. The peculiar O6f star HD 148937 and the symmetrically surrounding nebulae

    NASA Technical Reports Server (NTRS)

    Johnson, H. M.

    1972-01-01

    The ultraviolet continuum of the star is observed and, after standard reddening corrections are applied, it is found to be hotter than a model 05 V star. The Of star and its two companions are photometered around wavelength 4640, 4686, and 4861 A. The results confirm Westerlund's (1960) absolute visual magnitude of about -6 for the Of star and confirm his rejection of NGC 6164-5 as a planetary nebula. Peculiarities of the system of nebular shells around HD 148937, of which NGC 6164-5 are the innermost, are discussed with reference to radiofrequency data. A standard extrapolation from the optical flux density of NGC 6164-5 predicts a detectable radio source but it does not appear in the relevant surveys.

  10. The challenge of measuring magnetic fields in strongly pulsating stars: the case of HD 96446

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    Among the early B-type stars, He-rich Bp stars exhibit the strongest large-scale organized magnetic fields with a predominant dipole contribution. The presence of β Cep-like pulsations in the typical magnetic early Bp-type star HD 96446 was announced a few years ago, but the analysis of the magnetic field geometry was hampered by the absence of a reliable rotation period and a sophisticated procedure for accounting for the impact of pulsations on the magnetic field measurements. Using new spectropolarimetric observations and a recently determined rotation period based on an extensive spectroscopic time series, we investigate the magnetic field model parameters of this star under more detailed considerations of the pulsation behaviour of line profiles.

  11. Radial velocity measurements of the chromospherically-active stars (2): HD 28591 = V492 Per

    NASA Technical Reports Server (NTRS)

    Dadonas, V.; Sperauskas, J.; Fekel, F. C.; Morton, M. D.

    1994-01-01

    From two sets of the spectroscopic observations covering a ten year period we have obtained 59 radial velocities of the chromospherically-active star HD 28591 = V492 Per. It is a G9III single-lined spectroscopic binary with a period of 21.2910 days and a circular orbit. The upsilon sin i of 24.6 km/sec, results in a minimum radius 10.3 solar radii. We estimate a distance of 165 +/- 40 pc and an orbital inclination of 65 +/- 25 degrees. The secondary is probably a mid to late-type K dwarf. The star is brighter than the limiting magnitude of the Bright Star Catalogue. The mean photometric and the orbital periods are identical within their uncertainties. Since the star fills a significant fraction of its Roche lobe, about 62%, the photometric light curve may be the result of starspots and a modest ellipticity effect.

  12. THE GEMINI NICI PLANET-FINDING CAMPAIGN: DISCOVERY OF A MULTIPLE SYSTEM ORBITING THE YOUNG A STAR HD 1160

    SciTech Connect

    Nielsen, Eric L.; Liu, Michael C.; Wahhaj, Zahed; Bowler, Brendan; Kraus, Adam; Chun, Mark; Ftaclas, Christ; Biller, Beth A.; Hayward, Thomas L.; Shkolnik, Evgenya L.; Tecza, Matthias; Clarke, Fraser; Close, Laird M.; Hartung, Markus; Males, Jared R.; Skemer, Andrew J.; Reid, I. Neill; Alencar, Silvia H. P.; Burrows, Adam; and others

    2012-05-01

    We report the discovery of two low-mass companions to the young A0V star HD 1160 at projected separations of 81 {+-} 5 AU (HD 1160 B) and 533 {+-} 25 AU (HD 1160 C) by the Gemini NICI Planet-Finding Campaign. Very Large Telescope images of the system taken over a decade for the purpose of using HD 1160 A as a photometric calibrator confirm that both companions are physically associated. By comparing the system to members of young moving groups and open clusters with well-established ages, we estimate an age of 50{sup +50}{sub -40} Myr for HD 1160 ABC. While the UVW motion of the system does not match any known moving group, the small magnitude of the space velocity is consistent with youth. Near-IR spectroscopy shows HD 1160 C to be an M3.5 {+-} 0.5 star with an estimated mass of 0.22{sup +0.03}{sub -0.04} M{sub Sun }, while NIR photometry of HD 1160 B suggests a brown dwarf with a mass of 33{sup +12}{sub -9} M{sub Jup}. The very small mass ratio (0.014) between the A and B components of the system is rare for A star binaries, and would represent a planetary-mass companion were HD 1160 A to be slightly less massive than the Sun.

  13. HD 140283: A STAR IN THE SOLAR NEIGHBORHOOD THAT FORMED SHORTLY AFTER THE BIG BANG

    SciTech Connect

    Bond, Howard E.; Nelan, Edmund P.; VandenBerg, Don A.; Schaefer, Gail H.; Harmer, Dianne E-mail: nelan@stsci.edu E-mail: schaefer@chara-array.org

    2013-03-01

    HD 140283 is an extremely metal-deficient and high-velocity subgiant in the solar neighborhood, having a location in the Hertzsprung-Russell diagram where absolute magnitude is most sensitive to stellar age. Because it is bright, nearby, unreddened, and has a well-determined chemical composition, this star avoids most of the issues involved in age determinations for globular clusters. Using the Fine Guidance Sensors on the Hubble Space Telescope, we have measured a trigonometric parallax of 17.15 {+-} 0.14 mas for HD 140283, with an error one-fifth of that determined by the Hipparcos mission. Employing modern theoretical isochrones, which include effects of helium diffusion, revised nuclear reaction rates, and enhanced oxygen abundance, we use the precise distance to infer an age of 14.46 {+-} 0.31 Gyr. The quoted error includes only the uncertainty in the parallax, and is for adopted surface oxygen and iron abundances of [O/H] = -1.67 and [Fe/H] = -2.40. Uncertainties in the stellar parameters and chemical composition, especially the oxygen content, now contribute more to the error budget for the age of HD 140283 than does its distance, increasing the total uncertainty to about {+-}0.8 Gyr. Within the errors, the age of HD 140283 does not conflict with the age of the Universe, 13.77 {+-} 0.06 Gyr, based on the microwave background and Hubble constant, but it must have formed soon after the big bang.

  14. Line identifications and preliminary abundances from the red spectrum of HD 101065 (Przybylski's star)

    NASA Astrophysics Data System (ADS)

    Cowley, C. R.; Mathys, G.

    1998-11-01

    We have made a line identification list and derived preliminary abundances for the extreme peculiar star HD 101065 (Przybylski's star), based on a spectrum recorded at ESO with the CASPEC spectrograph. The line list covers the range 5445-6587 Angstroms. We find iron to be mildly deficient, possibly not as much as an order of magnitude, while the lanthanide rare earths are enhanced by some 4 dex. Abundances rather like this are found in the hotter Ap stars. However, spectra of the latter are quite different in appearance from HD 101065. Insight into how this can be is illustrated from a synthesis of the region containing the strong iron lines lambda lambda 4383, 4404, and 4415. Advantage is taken of the achieved line identifications to determine the longitudinal magnetic field of the star from the analysis of the Nd scriptstyleII lines of its spectrum: (-1408+/-50) G. Based on observations obtained at the European Southern Observatory, La Silla, Chile (ESO programme No.~49.7-029)

  15. FUV spectroscopic study of the circumstellar environment of the Herbig Be star HD 250550.

    NASA Astrophysics Data System (ADS)

    Martin, C.; Bouret, J.-C.; Deleuil, M.; Simon, T.; Catala, C.; Roberge, A.

    2002-12-01

    We present FUSE observations of the Herbig Ae/Be star HD 250550, a well known analog to the prototype of the whole class, AB Aurigae. Previous optical and UV (IUE) observations showed that HD 250550 possesses a strong stellar wind and a dense chromosphere. Quite unexpectedly, the FUSE spectra of HD 250550 show only a faint emission feature at 977 Å, and emission from O VI resonance lines is barely visible, contrary to what was observed for AB Aurigae by FUSE. Several absorption features from molecular hydrogen are observed and show that H2 is thermalized up to J=3 and its radial velocity is identical to that of the surrounding molecular cloud's velocity. Similar velocities are measured on absorption features arising from excited levels of atomic species like N I, Cl I and Cl II, P II, Fe II and Fe III. This strongly favours a circumstellar origin for these gazeous components. Besides, the spectra also contains several other absorption features of interstellar origin (Ar I, Fe II, ...) as demonsrated by the lower radial velocities and excitation temperatures. Our results reveal a complex circumstellar environment with unxepected characteritics, and suggest that quite a large part of the original molecular cloud that collapsed to form the star is still present, though its spatial distribution is still unknown. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.

  16. Testing stellar evolution models with the retired A star HD 185351

    NASA Astrophysics Data System (ADS)

    Hjørringgaard, J. G.; Silva Aguirre, V.; White, T. R.; Huber, D.; Pope, B. J. S.; Casagrande, L.; Justesen, A. B.; Christensen-Dalsgaard, J.

    2017-01-01

    The physical parameters of the retired A star HD 185351 were analysed in great detail by Johnson et al. using interferometry, spectroscopy, and asteroseismology. Results from all independent methods are consistent with HD 185351 having a mass in excess of 1.5 M⊙. However, the study also showed that not all observational constraints could be reconciled in stellar evolutionary models, leading to mass estimates ranging from ˜1.6 to 1.9 M⊙ and casting doubts on the accuracy of stellar properties determined from asteroseismology. Here, we solve this discrepancy and construct a theoretical model in agreement with all observational constraints on the physical parameters of HD 185351. The effects of varying input physics are examined as well as the additional constraint of the observed g-mode period spacing is considered. This quantity is found to be sensitive to the inclusion of additional mixing from the convective core during the main sequence, and can be used to calibrate the overshooting efficiency using low-luminosity red giant stars. A theoretical model with metallicity [Fe/H] = 0.16 dex, mixing-length parameter αMLT = 2.00, and convective overshooting efficiency parameter f = 0.030 is found to be in complete agreement with all observational constraints for a stellar mass of M ≃ 1.60 M⊙.

  17. Abundances in Przybylski's star

    NASA Astrophysics Data System (ADS)

    Cowley, C. R.; Ryabchikova, T.; Kupka, F.; Bord, D. J.; Mathys, G.; Bidelman, W. P.

    2000-09-01

    We have derived abundances for 54 elements in the extreme roAp star HD101065. ESO spectra with a resolution of about 80000, and S/N of 200 or more were employed. The adopted model has Teff=6600K, and log(g)=4.2. Because of the increased line opacity and consequent low gas pressure, convection plays no significant role in the temperature structure. Lighter elemental abundances through the iron group scatter about standard abundance distribution (SAD) (solar) values. Iron and nickel are about one order of magnitude deficient while cobalt is enhanced by 1.5dex. Heavier elements, including the lanthanides, generally follow the solar pattern but enhanced by 3 to 4dex. Odd-Z elements are generally less abundant than their even-Z neighbours. With a few exceptions (e.g. Yb), the abundance pattern among the heavy elements is remarkably coherent, and resembles a displaced solar distribution.

  18. HD 179821 (V1427 Aql, IRAS 19114+0002) - a massive post-red supergiant star?

    NASA Astrophysics Data System (ADS)

    Şahin, T.; Lambert, David L.; Klochkova, Valentina G.; Panchuk, Vladimir E.

    2016-10-01

    We have derived elemental abundances of a remarkable star, HD 179821, with unusual composition (e.g. [Na/Fe] = 1.0 ± 0.2 dex) and extra-ordinary spectral characteristics. Its metallicity at [Fe/H] = 0.4 dex places it among the most metal-rich stars yet analysed. The abundance analysis of this luminous star is based on high-resolution and high-quality (S/N ≈ 120-420) optical echelle spectra from McDonald Observatory and Special Astronomy Observatory. The data includes five years of observations over 21 epochs. Standard 1D local thermodynamic equilibrium analysis provides a fresh determination of the atmospheric parameters over all epochs: Teff = 7350 ± 200 K, log g= +0.6 ± 0.3, and a microturbulent velocity ξ = 6.6 ± 1.6 km s-1 and [Fe/H] = 0.4 ± 0.2, and a carbon abundance [C/Fe] = -0.19 ± 0.30. We find oxygen abundance [O/Fe] = -0.25 ± 0.28 and an enhancement of 0.9 dex in N. A supersonic macroturbulent velocity of 22.0 ± 2.0 km s-1 is determined from both strong and weak Fe I and Fe II lines. Elemental abundances are obtained for 22 elements. HD 179821 is not enriched in s-process products. Eu is overabundant relative to the anticipated [X/Fe] ≈ 0.0. Some peculiarities of its optical spectrum (e.g. variability in the spectral line shapes) is noticed. This includes the line profile variations for H α line. Based on its estimated luminosity, effective temperature and surface gravity, HD 179821 is a massive star evolving to become a red supergiant and finally a Type II supernova.

  19. Determining the atmospheric structure and dynamics of the FK Comae Star HD32918

    NASA Technical Reports Server (NTRS)

    Robinson, R. D.

    1995-01-01

    The results of UV observations taken with the International Ultraviolet Explorer (IUE) satellite and microwave observations obtained with the Australia Telescope during an observing campaign of the rapidly rotating K0 dwarf star HD 197890, nicknamed 'Speedy Mic' are presented. This star was recently recognized as a powerful, transient EUV source by the ROSAT WFC, and subsequent investigation showed it to be a ZAMS or possibly a PMS dwarf which may be a member of the Local Association. Our observations show it to have strong, variable UV emission lines near the 'saturation' levels. The radio observations show a level of 'quiescent' emission consistent with other rapidly rotating stars, but there is no evidence for the large flux variations that normally characterize the time history of such objects.

  20. X-Ray Spectroscopy of the O2 If* Star HD 93129A

    NASA Astrophysics Data System (ADS)

    Cohen, D. H.

    2012-12-01

    The O2 If* star, HD 93129A, is among the earliest in the Galaxy and has one of the strongest winds of any O star. In this paper, we show that its hard and strong X-ray emission can be understood in terms of the standard embedded wind shock paradigm for effectively single, hot, massive stars. Wind attenuation of the intrinsically soft X-ray emission is an important effect, which explains the hardness of the observed X-rays. We measure the degree of wind absorption in two different ways in order to derive a mass-loss rate of roughly 6 × 10-6 Msun; yr-1. This value is consistent with the observed Hα line if a clumping factor of fcl = 12 is assumed.

  1. A NEW SUB-STELLAR COMPANION AROUND THE YOUNG STAR HD 284149

    SciTech Connect

    Bonavita, Mariangela; Desidera, Silvano; Daemgen, Sebastian; Jayawardhana, Ray; Janson, Markus; Lafrenière, David

    2014-08-20

    Even though only a handful of sub-stellar companions have been found via direct imaging, each of these discoveries has had a tremendous impact on our understanding of the star formation process and the physics of cool atmospheres. Young stars are prime targets for direct imaging searches for planets and brown dwarfs due to the favorable brightness contrast expected at such ages and also because it is often possible to derive relatively good age estimates for these primaries. Here we present the direct imaging discovery of HD 284149 b, a 18-50 M {sub Jup} companion at a projected separation of 400 AU from a young (25{sub 10}{sup +25} Myr) F8 star, with which it shares common proper motion.

  2. The photometric variability of the chromospherically active binary star HD 80715

    NASA Technical Reports Server (NTRS)

    Strassmeier, Klaus G.; Hooten, James T.; Hall, Douglas S.; Fekel, Francis C.

    1989-01-01

    Differential UBVRI photometry of the double-lined BY Dra system HD 80715 (K3 V + K3 V) obtained in December 1987 is presented. The star is found to be a variable with a full amplitude of 0.06 mag in V and a period similar or equal to the orbital period of 3.804 days. The mechanism of the variability is interpreted as rotational modulation due to dark starspots. In an attempt to detect chromospheric activity, high-resolution CCD spectra were obtained at Ca II H and K and at Fe I 6430 A and Ca I 6439 A, the photospheric lines normally used for Doppler imaging. HD 80715 shows double H and K emission features at a constant flux level for each component.

  3. VizieR Online Data Catalog: HST photometry of stars in HD 97950 (Pang+, 2016)

    NASA Astrophysics Data System (ADS)

    Pang, X.; Pasquali, A.; Grebel, E. K.

    2016-07-01

    The HD97950 cluster and its immediate surroundings in the giant HII region NGC3603 were observed with the Hubble Space Telescope (HST). The ultraviolet (UV) data were taken with the High Resolution Channel (HRC) of the Advanced Camera for Surveys (ACS) in 2005 (GO 10602, PI: Jesus Maiz Apellaniz) through the F220W, F250W, F330W, and F435W filters. The HRC is characterized by a spatial resolution of 0.03"/pixel and a field of view of 29''*25''. The optical observations were carried out with the Wide Field and Planetary Camera 2 (WFPC2) in two epochs: 1997 (GO 6763, PI: Laurent Drissen) and 2007 (GO 11193, PI: Wolfgang Brandner) through the F555W, F675W, and F814W filters. The Planetary Camera (PC) chip was centered on the cluster (0.045"/pixel, 40''*40'') for both programs. Pang et al. 2013 (cat. J/ApJ/764/73) reduced the two-epoch WFPC2 data and identified more than 400 member stars on the PC chip via relative proper motions. Of these member stars, 142 are in common between the HRC and PC images and thus have UV and optical photometry available (see Table1). Among the HD97950 cluster member stars determined from relative proper motions (Pang et al. 2013, cat. J/ApJ/764/73, Table2), there are five main-sequence (MS) stars located in the cluster with projected distances of r<0.7pc from the center, for which there are also spectral types available from Table3 of Melena et al. (2008AJ....135..878M). The photometry of these five MS stars is presented in Table2. The individual color excesses and extinctions of the member main sequence stars are listed in Table3. (3 data files).

  4. Discovery of a low-mass companion to the F7V star HD 984

    NASA Astrophysics Data System (ADS)

    Meshkat, T.; Bonnefoy, M.; Mamajek, E. E.; Quanz, S. P.; Chauvin, G.; Kenworthy, M. A.; Rameau, J.; Meyer, M. R.; Lagrange, A.-M.; Lannier, J.; Delorme, P.

    2015-11-01

    We report the discovery of a low-mass companion to the nearby (d = 47 pc) F7V star HD 984. The companion is detected 0.19 arcsec away from its host star in the L' band with the Apodized Phase Plate on NaCo/Very Large Telescope and was recovered by L'-band non-coronagraphic imaging data taken a few days later. We confirm the companion is comoving with the star with SINFONI integral field spectrograph H + K data. We present the first published data obtained with SINFONI in pupil-tracking mode. HD 984 has been argued to be a kinematic member of the 30 Myr-old Columba group, and its HR diagram position is not altogether inconsistent with being a zero-age main sequence star of this age. By consolidating different age indicators, including isochronal age, coronal X-ray emission, and stellar rotation, we independently estimate a main-sequence age of 115 ± 85 Myr (95 per cent CL) which does not rely on this kinematic association. The mass of directly imaged companions are usually inferred from theoretical evolutionary tracks, which are highly dependent on the age of the star. Based on the age extrema, we demonstrate that with our photometric data alone, the companion's mass is highly uncertain: between 33 and 96 MJup (0.03-0.09 M⊙) using the COND evolutionary models. We compare the companion's SINFONI spectrum with field dwarf spectra to break this degeneracy. Based on the slope and shape of the spectrum in the H band, we conclude that the companion is an M6.0 ± 0.5 dwarf. The age of the system is not further constrained by the companion, as M dwarfs are poorly fit on low-mass evolutionary tracks. This discovery emphasizes the importance of obtaining a spectrum to spectral type companions around F-stars.

  5. Evidence for wind and accretion in the Herbig Be star HD 100546 from FUSE observations

    NASA Astrophysics Data System (ADS)

    Deleuil, M.; Lecavelier des Etangs, A.; Bouret, J.-C.; Roberge, A.; Vidal-Madjar, A.; Martin, C.; Feldman, P. D.; Ferlet, R.

    2004-05-01

    We present the first far-UV spectra of the Herbig Be star HD 100546, observed by the Far Ultraviolet Spectroscopic Explorer (FUSE) as part of the Circumstellar Disks team program. We identified and analyzed numerous narrow absorption lines of circumstellar origin. Intense, broad and fairly asymmetric emission lines of C II, C III, O VI and S II were also detected, spanning temperatures up to 3× 105 K. Comparison of the spectra recorded two years apart reveals strong spectral variations, not only in the emission lines but also in the circumstellar lines of N I, N II, O I, Ar I and Fe II. The varying absorption lines of N I and O I exhibit the largest velocity width, from -200 to +320 km s-1, relative to the star's rest-frame. Variations on a timescale of an hour occurred only in the N I resonance triplet and O I (1D) lines. The spectroscopic variability highlighted by these two observations and the line profile analysis reveal signatures of both outflow and infall processes, which appear to be related in this system. We suggest that these spectral signatures originate in a stellar magnetosphere, which likely interacts with the innermost part of the star's circumstellar disk. This interpretation can account for the main features observed in the spectrum of HD 100546: variable emission and absorption lines as well as suspected continuum variation.

  6. Pulsational frequencies of the eclipsing δ Scuti star HD 172189. Results of the STEPHI XIII campaign

    NASA Astrophysics Data System (ADS)

    Costa, J. E. S.; Michel, E.; Peña, J.; Creevey, O.; Li, Z. P.; Chevreton, M.; Belmonte, J. A.; Alvarez, M.; Fox Machado, L.; Parrao, L.; Pérez Hernández, F.; Fernández, A.; Fremy, J. R.; Pau, S.; Alonso, R.

    2007-06-01

    Context: The eclipsing δ Scuti star HD 172189 is a probable member of the open cluster IC 4756 and a promising candidate target for the CoRoT mission. Aims: The detection of pulsation modes is the first step in the asteroseismological study of the star. Further, the calculation of the orbital parameters of the binary system allows us to make a dynamical determination of the mass of the star, which works as an important constraint to test and calibrate the asteroseismological models. Methods: We performed a detailed frequency analysis of 210 hours of photometric data of HD 172189 obtained from the STEPHI XIII campaign. Results: We have identified six pulsation frequencies with a confidence level of 99% and a seventh with a 65% confidence level of 65%, in the range between 100-300 μHz. In addiction, three eclipses were observed during the campaign, allowing us to improve the determination of the orbital period of the system. Table 1 is only available in electronic form at http://www.aanda.org

  7. The immediate environments of two Herbig Be stars: MWC 1080 and HD 259431

    SciTech Connect

    Li, Dan; Mariñas, Naibí; Telesco, Charles M.

    2014-12-01

    Deep mid-infrared (10-20 μm) images with sub-arcsecond resolution were obtained for two Herbig Be stars, MWC 1080 and HD 259431, to probe their immediate environments. Our goal is to understand the origin of the diffuse nebulosities observed around these two very young objects. By analyzing our new mid-IR images and comparing them to published data at other wavelengths, we demonstrate that the well-extended emission around MWC 1080 traces neither a disk nor an envelope, but rather the surfaces of a cavity created by the outflow from MWC 1080A, the primary star of the MWC 1080 system. In the N-band images, the filamentary nebulosities trace the hourglass-shaped gas cavity wall out to ∼0.15 pc. This scenario reconciles the properties of the MWC 1080 system revealed by a wide range of observations. Our finding confirms that the environment around MWC 1080, where a small cluster is forming, is strongly affected by the outflow from the central Herbig Be star. Similarities observed between the two subjects of this study suggest that the filamentary emission around HD 259431 may also arise from a similar outflow cavity structure.

  8. A RESOLVED DEBRIS DISK AROUND THE CANDIDATE PLANET-HOSTING STAR HD 95086

    SciTech Connect

    Moór, A.; Ábrahám, P.; Szabó, Gy. M.; Kiss, Cs.; Kóspál, Á.; Apai, D.; Pascucci, I.; Balog, Z.; Henning, Th.; Csengeri, T.; Grady, C.; Juhász, A.; Szulágyi, J.; Vavrek, R.

    2013-10-01

    Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD 95086. The strong infrared excess of the system indicates that, similar to HR8799, β Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD 95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared, and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of ∼6.''0 × 5.''4 (540 × 490 AU) and disk inclination of ∼25°. Assuming the same inclination for the planet candidate's orbit, its reprojected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD 95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modeling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks coexist.

  9. A Resolved Debris Disk Around the Candidate Planet-hosting Star HD 95086

    NASA Technical Reports Server (NTRS)

    Moor, A.; Abraham, P.; Kospal, A.; Szabo, Gy. M.; Apai, D.; Balog, Z.; Csengeri, T.; Grady, C.; Henning, Th.; Juhasz, J.; Kiss, Cs.; Pasucci, I.; Szulagyi, J.; Vavrek, R.

    2013-01-01

    Recently, a new planet candidate was discovered on direct images around the young (10-17 Myr) A-type star HD 95086. The strong infrared excess of the system indicates that, similar to HR8799, Beta Pic, and Fomalhaut, the star harbors a circumstellar disk. Aiming to study the structure and gas content of the HD 95086 disk, and to investigate its possible interaction with the newly discovered planet, here we present new optical, infrared, and millimeter observations. We detected no CO emission, excluding the possibility of an evolved gaseous primordial disk. Simple blackbody modeling of the spectral energy distribution suggests the presence of two spatially separate dust belts at radial distances of 6 and 64 AU. Our resolved images obtained with the Herschel Space Observatory reveal a characteristic disk size of approx. 6.0 × 5.4 (540 × 490 AU) and disk inclination of approx 25 deg. Assuming the same inclination for the planet candidate's orbit, its reprojected radial distance from the star is 62 AU, very close to the blackbody radius of the outer cold dust ring. The structure of the planetary system at HD 95086 resembles the one around HR8799. Both systems harbor a warm inner dust belt and a broad colder outer disk and giant planet(s) between the two dusty regions. Modeling implies that the candidate planet can dynamically excite the motion of planetesimals even out to 270 AU via their secular perturbation if its orbital eccentricity is larger than about 0.4. Our analysis adds a new example to the three known systems where directly imaged planet(s) and debris disks coexist.

  10. A comprehensive analysis of the magnetic standard star HD 94660: Host of a massive compact companion?

    NASA Astrophysics Data System (ADS)

    Bailey, J. D.; Grunhut, J.; Landstreet, J. D.

    2015-03-01

    Aims: Detailed information about the magnetic geometry, atmospheric abundances and radial velocity variations has been obtained for the magnetic standard star HD 94660 based on high-dispersion spectroscopic and spectropolarimetric observations from the UVES, HARPSpol and ESPaDOnS instruments. Methods: We perform a detailed chemical abundance analysis using the spectrum synthesis code ZEEMAN for a total of 17 elements. Using both line-of-sight and surface magnetic field measurements, we derive a simple magnetic field model that consists of dipole, quadrupole and octupole components. Results: The observed magnetic field variations of HD 94660 are complex and suggest an inhomogeneous distribution of chemical elements over the stellar surface. This inhomogeneity is not reflected in the abundance analysis, from which all available spectra are modelled, but only a mean abundance is reported for each element. The derived abundances are mostly non-solar, with striking overabundances of Fe-peak and rare-earth elements. Of note are the clear signatures of vertical chemical stratification throughout the stellar atmosphere, most notably for the Fe-peak elements. We also report on the detection of radial velocity variations with a total range of 35 km s-1 in the spectra of HD 94660. A preliminary analysis shows the most likely period of these variations to be of order 840 d and, based on the derived orbital parameters of this star, suggests the first detection of a massive compact companion for a main sequence magnetic star. Conclusions: HD 94660 exhibits interestingly complex magnetic field variations and remarkable radial velocity variations. Long term monitoring is necessary to provide further constraints on the nature of these radial velocity variations. Detection of a companion will help establish the role of binarity in the origin of magnetism in stars with radiative envelopes. Based in part on our own observations made with the European Southern Observatory (ESO

  11. Low-frequency GMRT observations of the magnetic Bp star HR Lup (HD 133880)

    NASA Astrophysics Data System (ADS)

    George, Samuel J.; Stevens, Ian R.

    2012-06-01

    We present radio observations of the magnetic chemically peculiar Bp star HR Lup (HD 133880) at 647 and 277 MHz with the GMRT. At both frequencies the source is not detected but we are able to determine upper limits to the emission. The 647 MHz limits are particularly useful, with a 5σ value of 0.45 mJy. Also, no large enhancements of the emission were seen. The non-detections, along with previously published higher frequency detections, provide evidence that an optically thick gyrosynchrotron model is the correct mechanism for the radio emission of HR Lup.

  12. The narrow, inner CO ring around the magnetic Herbig Ae star HD 101412

    NASA Astrophysics Data System (ADS)

    Cowley, C. R.; Hubrig, S.; Castelli, F.; Wolff, B.

    2012-01-01

    We describe and model emission lines in the first overtone band of CO in the magnetic Herbig Ae star HD 101412. High-resolution CRIRES spectra reveal unusually sharp features which suggest the emission is formed in a thin disk centered at 1 AU with a width 0.32 AU or less. A wider disk will not fit the observations. Previous observations have reached similar conclusions, but the crispness of the new material brings the emitting region into sharp focus. Based on observations obtained at the European Southern Observatory (ESO programme 087.C-0124(A)).

  13. A study of Herbig Ae Be star HD 163296: variability in co and oh

    NASA Astrophysics Data System (ADS)

    Yoder, Diana Lyn Hubis

    Spectra of the Herbig Ae Be star HD 163296 show variability in the CO and OH ro-vibrational emission lines. Documented here is the variance of OH emission lines between measurements separated by a period of three years. By comparing this variability to the variability of CO, we aim to determine whether the two are linked through an event such as disk winds. We find the profiles of OH and CO taken within three months of each other to have exceedingly similar profile shapes. However, the variability seen between the OH data sets needs further work to verify whether the changes we see are reproducible.

  14. The remarkably unremarkable global abundance variations of the magnetic Bp star HD 133652

    NASA Astrophysics Data System (ADS)

    Bailey, J. D.; Landstreet, J. D.

    2015-08-01

    Context. In recent years, significant effort has been made to understand how the magnetic field strengths and atmospheric chemical abundances of Ap/Bp stars evolve during their main sequence lifetime by identifying a large number of Ap/Bp stars with accurately known ages. As a next step, these stars should be studied individually and in detail to offer further insight into the physics of how such main sequence stars evolve. Aims: We have obtained high resolution spectra using the ESPaDOnS spectropolarimeter and FEROS spectrograph of the chemically peculiar, magnetic Bp star HD 133652. Using these data, we present a simple magnetic field model and abundance determinations of He, O, Mg, Si, Ti, Cr, Fe, Pr, and Nd. Methods: Abundance analysis was performed using zeeman.f, a spectral synthesis program that includes the effects of magnetic fields on line formation. The magnetic field structure is approximated as a simple, co-linear multipole expansion that reproduces the observed variations of the line-of-sight magnetic field with phase. The abundance distribution of each element was modelled using a uniform abundance in each of the two magnetic hemispheres. Results: Using the new magnetic field measurements, we were able to refine the rotation period of HD 133652 to P = 2.30405 ± 0.00002 d. The abundance analysis reveals that the elements modelled (except He, O and Mg) are overabundant compared to the Sun; however most elements studied do not show substantial differences in the large-scale mean abundances between the two magnetic hemispheres. The individual line profiles are very complex and clearly indicate the presence of significant small-scale abundance variations on the stellar surface. Conclusions: These data are adequate to perform a useful investigation of the magnetic field structure and abundance distribution over the stellar surface. HD 133652 is now one of a growing list of hotter Bp stars of known age for which this type of analysis has been performed

  15. Elemental abundances of the B and A stars. 2: Gamma Geminorum, HD 60825, 7 Sextantis, HR 4817, and HR 5780

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.; Philip, A. G. Davis

    1994-01-01

    We extend fine analyses of the B and A stars, gamma Geminorum, 7 Sextantis, HR 4817, and HR 5780 using additional spectroscopic data from the Kitt Peak National Observatory (KPNO) coude feed telescope with a TI CCD, camera 5, and grating A, and ATLAS9 model atmospheres. In addition we study HD 60825, which had colors similar to the FHB A stars, but was found to be a Population I star. HD 60825, as is gamma Gem, is a sharp-lined early-A star with nearly solar derived abundances. HR 5780 and 7 Sex are also examples of stars which for the most part have solar abundances. The newly derived abundances for HR 4817 reveal important differences with respect to 53 Tau, a somewhat similar HgMn star.

  16. Orbital motion of the binary brown dwarf companions HD 130948 BC around their host star

    NASA Astrophysics Data System (ADS)

    Ginski, C.; Neuhäuser, R.; Mugrauer, M.; Schmidt, T. O. B.; Adam, C.

    2013-09-01

    Evolutionary models and mass estimates for brown dwarfs remain uncertain, hence determining the masses of brown dwarfs by model-independent methods is important to test and constrain such theories. Following the orbital motion of brown dwarf companions around their primaries gives us the opportunity to dynamically calculate the masses of these systems. In addition, detecting curvature (acceleration or deceleration) in the orbit would confirm that the companion is physically associated with its primary, thus eliminating the possibility of a by-chance alignment of the primary's and the companion's proper motions and positions. Furthermore, the orbit parameters can be important indicators for the formation process of such wide, massive substellar companions. The binary brown dwarf companions to HD 130948 were discovered by Potter et al. We present various observations of this triple system over the course of 7 yr. With these data points we can show that HD 130948 BC are indeed comoving with HD 130948 A with higher significance than before (˜32.4σ), and also for the first time that the BC pair shows differential motion relative to A (˜2.2σ). We introduce an orbit fitting approach and constrain the orbit parameters for the orbit of the BC binary around their host star.

  17. Multiwavelength study of the magnetically active T Tauri star HD 283447

    NASA Technical Reports Server (NTRS)

    Feigelson, Eric D.; Welty, Alan D.; Imhoff, Catherine; Hall, Jeffrey C.; Etzel, Paul B.; Phillips, Robert B.; Lonsdale, Colin J.

    1994-01-01

    We observed the luminous T Tauri star HD 283447 = V773 Tauri simultaneously at X-ray, ultraviolet, optical photometric and spectroscopic, and radio wavelengths for several hours on UT 1992 September 11. ROSAT, IUE, Very Large Array (VLA) and an intercontinental Very Long Baseline Interferometry (VLBI) network, and three optical observatories participated in the campaign. The star is known for its unusually high and variable nonthermal radio continuum emission. High levels of soft X-ray and Mg II line emission are discovered, with luminosity L(sub x) = 5.5 x 10(exp 30) ergs/s (0.2 - 2 keV) and L(sub Mg II) = 1 x 10(exp 29) ergs/s, respectively. Optically, the spectrum exhibits rather weak characteristics of `classical' T Tauri stars. A faint, broad emission line component, probably due to a collimated wind or infall, is present. During the campaign, the radio luminosity decreased by a factor of 4, while optical/UV lines and X-ray emission remained strong but constant. The large gyrosynchrotron-emitting regions are therefore decoupled from the chromospheric and coronal emission. Five models for the magnetic geometry around the star are discussed; solar-type activity, dipole magnetosphere, star-disk magnetic coupling, disk magnetic fields, and close binary interaction. The data suggest that two magnetic geometries are simultaneously present: complex multipolar fields like those on the Sun, and a large-scale field possibly associated with the circumstellar disk.

  18. Spectrophotometry of peculiar B and A stars. XVIII - The helium rich variable stars HR 1890, Sigma Orionis E, and HD 37776

    NASA Technical Reports Server (NTRS)

    Adelman, S. J.; Pyper, D. M.

    1985-01-01

    Optical region spectrophotometry at 3300-7850 A has been obtained for three helium rich stars, HR 1890, Sigma Ori E, and HD 37776, of the Orion OB1 Association. New uvby-beta photometry of HR 1890 and HD 37776 as well as published data are also used to investigate the variability of these stars. A new period of 1.53862 days was determined for HD 37776. For all three stars H-beta varies in antiphase with strong He I lines. The spectrophotometric bandpass containing the strong He I line at 4471 A varies in phase with the R index of Pedersen and Thomsen (1977). Evidence is found for weak absorption features which appear to be an extension of the 5200 A feature seen in cooler CP stars.

  19. A SUB-STELLAR COMPANION AROUND THE F7 V STAR HD 8673

    SciTech Connect

    Hartmann, Michael; Guenther, Eike W.; Hatzes, Artie P.

    2010-07-01

    In order to investigate the dependence of planet formation on stellar mass, we have been monitoring a sample of F-type main-sequence stars with the 2.0 m Alfred-Jensch telescope of the Thueringer Landessternwarte Tautenburg. This survey is based on high-precision radial velocity (RV) measurements using the coude echelle spectrograph and an iodine absorption cell. We present RV measurements of the F7 V star HD 8673 that show a long-term variability of 1634 days with a semi-amplitude K = 288 m s{sup -1} that can be explained most reasonably by an orbiting sub-stellar companion with a minimum mass of 14.2 M{sub Jup} in a high-eccentricity (e = 0.723) Keplerian orbit.

  20. A DOUBLE PLANETARY SYSTEM AROUND THE EVOLVED INTERMEDIATE-MASS STAR HD 4732

    SciTech Connect

    Sato, Bun'ei; Omiya, Masashi; Harakawa, Hiroki; Nagasawa, Makiko; Ida, Shigeru; Wittenmyer, Robert A.; Izumiura, Hideyuki; Kambe, Eiji; Takeda, Yoichi; Kokubo, Eiichiro; Yoshida, Michitoshi; Itoh, Yoichi; Ando, Hiroyasu

    2013-01-01

    We report the detection of a double planetary system orbiting around the evolved intermediate-mass star HD 4732 from precise Doppler measurements at Okayama Astrophysical Observatory and Australian Astronomical Observatory. The star is a K0 subgiant with a mass of 1.7 M {sub Sun} and solar metallicity. The planetary system is composed of two giant planets with minimum mass of msin i = 2.4 M {sub J}, orbital period of 360.2 days and 2732 days, and eccentricity of 0.13 and 0.23, respectively. Based on dynamical stability analysis for the system, we set the upper limit on the mass of the planets to be about 28 M {sub J} (i > 5 Degree-Sign ) in the case of coplanar prograde configuration.

  1. The galactic unclassified B[e] star HD 50138. I. A possible new shell phase

    NASA Astrophysics Data System (ADS)

    Borges Fernandes, M.; Kraus, M.; Chesneau, O.; Domiciano de Souza, A.; de Araújo, F. X.; Stee, P.; Meilland, A.

    2009-12-01

    Context: The observed spectral variation of HD 50138 has led different authors to classify it in a very wide range of spectral types and luminosity classes (from B5 to A0 and III to Ia) and at different evolutionary stages as either HAeBe star or classical Be. Aims: Based on new high-resolution optical spectroscopic data from 1999 and 2007 associated to a photometric analysis, the aim of this work is to provide a deep spectroscopic description and a new set of parameters for this unclassified southern B[e] star and its interstellar extinction. Methods: From our high-resolution optical spectroscopic data separated by 8 years, we perform a detailed spectral description, presenting the variations seen and discussing their possible origin. We derive the interstellar extinction to HD 50138 by taking the influences of the circumstellar matter in the form of dust and an ionized disk into account. Based on photometric data from the literature and the new Hipparcos distance, we obtain a revised set of parameters for HD 50138. Results: Because of the spectral changes, we tentatively suggest that a new shell phase could have taken place prior to our observations in 2007. We find a color excess value of E(B-V) = 0.08 mag, and from the photometric analysis, we suggest that HD 50138 is a B6-7 III-V star. A discussion of the different evolutionary scenarios is also provided. Based on observations: (i) with the 1.52-m and 2.2-m telescopes at the European Southern Observatory (La Silla, Chile), under agreement with the Observatório Nacional-MCT (Brazil); and (ii) with the Telescope Bernard Lyot, Observatory of Pic du Midi (France). Table 1 is 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/508/309 It is with great sadness that we have to report that, during the final stages of this paper, we had a deep loss when Francisco X. de Araújo passed away.

  2. Vertical abundance stratification in the blue horizontal branch star HD 135485

    NASA Astrophysics Data System (ADS)

    Khalack, V. R.; Leblanc, F.; Bohlender, D.; Wade, G. A.; Behr, B. B.

    2007-05-01

    Context: It is commonly believed that the observed overabundances of many chemical species relative to the expected cluster metallicity in blue horizontal branch (BHB) stars appear as a result of atomic diffusion in the photosphere. The slow rotation of BHB stars (with T_eff > 11 500 K), typically v sin{i} < 10 km s-1, is consistent with this idea. Aims: In this work we search for observational evidence of vertical chemical stratification in the atmosphere of HD 135485. If this evidence exists, it will demonstrate the importance of atomic diffusion processes in the atmospheres of BHB stars. Methods: We undertake an extensive abundance stratification analysis of the atmosphere of HD 135485, based on recently acquired high resolution and S/N CFHT ESPaDOnS spectra and a McDonald-CE spectrum. Results: Our numerical simulations show that nitrogen and sulfur reveal signatures of vertical abundance stratification in the stellar atmosphere. It appears that the abundances of these elements increase toward the upper atmosphere. This fact cannot be explained by the influence of microturbulent velocity, because oxygen, carbon, neon, argon, titanium and chromium do not show similar behavior and their abundances remain constant throughout the atmosphere. It seems that the iron abundance may increase marginally toward the lower atmosphere. This is the first demonstration of vertical abundance stratification of metals in a BHB star. Based on observations made with ESPaDOnS at the Canada-France-Hawaii Telescope (CFHT) operated by the National Research Council (NRC) of Canada, the Institut des Sciences de l'Univers of the Centre National de la Recherche Scientifique (CNRS) and the University of Hawaii and on observations made with Echelle Spectrograph on the McDonald Observatory 2.1-m Otto Struve Telescope. Full Table 2 is only available in electronic form at http://www.aanda.org

  3. Stellar Parameters for HD 69830, a Nearby Star with Three Neptune Mass Planets and an Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Tanner, Angelle M.; Boyajian, T. S.; von Braun, K.; van Belle, G.; Beichman, C. A.; Fischer, D.; Brewer, J. M.; GSU CHARA Team

    2014-01-01

    We have used the GSU CHARA telescope to directly measure the diameter of HD 69830, home to three Neptune mass planets and an asteroid belt. Our estimate for the limb-darkened angular diameter of this star leads to its physical radius and luminosity when combined with a fit to its observed optical to infrared spectral energy distribution. With precise values of the luminosity and effective temperature, we can then place HD 69830 on an HR diagram along with isochrones from the latest stellar formation models to determine the age of the star. Finally, the new value of stellar luminosity also leads to a refined estimate of the location of the habitable zone and the ice line for HD 69830. In this poster, we will report the newly determined stellar parameters for this high profile star and discuss how they influence our knowledge of the properties of its solar system.

  4. Time-Dependent Spectral Feature Variations of the FS CMa Star HD 50138

    NASA Astrophysics Data System (ADS)

    Jeřábková, T.; Korčáková, D.; Miroshnichenko, A. S.; Danford, S.; Zharikov, S. V.; Kříček, R.; Zasche, P.; Votruba, V.; Šlechta, M.; Škoda, P.; Janík, J.

    2017-02-01

    HD 50138 (V743 Mon, MWC 158, or IRAS 06491-0654) is a B[e] star of the FS CMa type. It is supposed to be a post-main-sequence star, which is still not highly evolved. The presence of a gaseous and dusty envelope precludes direct observations of the central object, and the possible binarity and physical nature of HD 50138 remains unclear. We present a long-term spectroscopic monitoring of this object over the last 20 years (Jeřábková et al. 2016). Based on the obtained data, we confirm a quasi-periodic behavior of the object's spectral variability with two newly found long periods manifested in the Hα and forbidden [O I] lines. The rotating structures around the object are supported by the detection of moving humps in the Hα profile. Our results are consistent with either mass transfer in a binary system or the presence of an outflowing disk. Since our data cannot confirm the presence of a binary companion, the origin of such systems remains an interesting problem for further investigation.

  5. THE ABSENCE OF COLD DUST AROUND WARM DEBRIS DISK STAR HD 15407A

    SciTech Connect

    Fujiwara, Hideaki; Onaka, Takashi; Takita, Satoshi; Kataza, Hirokazu; Murakami, Hiroshi; Yamashita, Takuya; Fukagawa, Misato; Ishihara, Daisuke

    2012-11-01

    We report Herschel and AKARI photometric observations at far-infrared (FIR) wavelengths of the debris disk around the F3V star HD 15407A, in which the presence of an extremely large amount of warm dust ({approx}500-600 K) has been suggested by mid-infrared (MIR) photometry and spectroscopy. The observed flux densities of the debris disk at 60-160 {mu}m are clearly above the photospheric level of the star, suggesting excess emission at FIR as well as at MIR wavelengths previously reported. The observed FIR excess emission is consistent with the continuum level extrapolated from the MIR excess, suggesting that it originates in the inner warm debris dust and cold dust ({approx}50-130 K) is absent in the outer region of the disk. The absence of cold dust does not support a late-heavy-bombardment-like event as the origin of the large amount of warm debris dust around HD 15047A.

  6. A SUPER-EARTH ORBITING THE NEARBY SUN-LIKE STAR HD 1461

    SciTech Connect

    Rivera, Eugenio J.; Vogt, Steven S.; Laughlin, Gregory; Meschiari, Stefano; Henry, Gregory W.

    2010-01-10

    We present precision radial velocity (RV) data that reveal a Super-Earth mass planet and two probable additional planets orbiting the bright nearby G0V star HD 1461. Our 12.8 years of Keck High Resolution Echelle Spectrometer precision RVs indicate the presence of a 7.4 M{sub +} planet on a 5.77 day orbit. The data also suggest, but cannot yet confirm, the presence of outer planets on low-eccentricity orbits with periods of 446.1 and 5017 days, and projected masses (Msin i) of 27.9 and 87.1 M{sub +}, respectively. Test integrations of systems consistent with the RV data suggest that the configuration is dynamically stable. We present a 12.2 year time series of photometric observations of HD 1461, which comprise 799 individual measurements, and indicate that it has excellent long-term photometric stability. However, there are small amplitude variations with periods comparable to those of the suspected second and third signals in the RVs near 5000 and 446 days, thus casting some suspicion on those periodicities as Keplerian signals. If the 5.77 day companion has a Neptune-like composition, then its expected transit depth is of order dapprox0.5 mmag. The geometric a priori probability of transits is approx8%. Phase folding of the ground-based photometry shows no indication that transits of the 5.77 day companion are occurring, but high-precision follow-up of HD 1461 during upcoming transit phase windows will be required to definitively rule out or confirm transits. This new system joins a growing list of solar-type stars in the immediate galactic neighborhood that are accompanied by at least one Neptune (or lower) mass planets having orbital periods of 50 days or less.

  7. HD 18078: A very slowly rotating Ap star with an unusual magnetic field structure

    NASA Astrophysics Data System (ADS)

    Mathys, G.; Romanyuk, I. I.; Kudryavtsev, D. O.; Landstreet, J. D.; Pyper, D. M.; Adelman, S. J.

    2016-02-01

    Context. The existence of a significant population of Ap stars with very long rotation periods (up to several hundred years) has progressively emerged over the past two decades. However, only lower limits of the periods are known for most of them because their variations have not yet been observed over a sufficient timebase. Aims: We determine the rotation period of the slowly rotating Ap star HD 18078 and we derive constraints on the geometrical structure of its magnetic field. Methods: We combine measurements of the mean magnetic field modulus obtained from 1990 to 1997 with determinations of the mean longitudinal magnetic field spanning the 1999-2007 time interval to derive an unambiguous value of the rotation period. We show that this value is consistent with photometric variations recorded in the Strömgren uvby photometric system between 1995 and 2004. We fit the variations of the two above-mentioned field moments with a simple model to constrain the magnetic structure. Results: The rotation period of HD 18078 is (1358 ± 12) d. The geometrical structure of its magnetic field is consistent to first order with a colinear multipole model whose axis is offset from the centre of the star. Conclusions: HD 18078 is only the fifth Ap star with a rotation period longer than 1000 d for which the exact value of that period (as opposed to a lower limit) could be determined. The strong anharmonicity of the variations of its mean longitudinal magnetic field and the shift between their extrema and those of the mean magnetic field modulus are exceptional and indicative of a very unusual magnetic structure. Based in part on observations made at Observatoire de Haute Provence (CNRS), France; at Kitt Peak National Observatory, National Optical Astronomy Observatory (NOAO Prop. ID: KP2442; PI: T. Lanz), which is operated by the Association of Universities for Research in Astronomy (AURA) under cooperative agreement with the National Science Foundation; at the Canada

  8. Stellar parameters and accretion rate of the transition disk star HD 142527 from X-shooter

    SciTech Connect

    Mendigutía, I.; Fairlamb, J.; Oudmaijer, R. D.; Montesinos, B.; Najita, J. R.; Brittain, S. D.; Van den Ancker, M. E.

    2014-07-20

    HD 142527 is a young pre-main-sequence star with properties indicative of the presence of a giant planet and/or a low-mass stellar companion. We have analyzed an X-Shooter/Very Large Telescope spectrum to provide accurate stellar parameters and accretion rate. The analysis of the spectrum, together with constraints provided by the spectral energy distribution fitting, the distance to the star (140 ± 20 pc), and the use of evolutionary tracks and isochrones, led to the following set of parameters: T{sub eff} = 6550 ± 100 K, log g = 3.75 ± 0.10, L{sub *}/L{sub ☉} = 16.3 ± 4.5, M{sub *}/M{sub ☉} = 2.0 ± 0.3, and an age of 5.0 ± 1.5 Myr. This stellar age provides further constraints to the mass of the possible companion estimated by Biller et al., being between 0.20 and 0.35 M{sub ☉}. Stellar accretion rates obtained from UV Balmer excess modeling and optical photospheric line veiling, and from the correlations with several emission lines spanning from the UV to the near-IR, are consistent with each other. The mean value from all previous tracers is 2 (±1) × 10{sup –7} M{sub ☉} yr{sup –1}, which is within the upper limit gas flow rate from the outer to the inner disk recently provided by Cassasus et al.. This suggests that almost all gas transferred between both components of the disk is not trapped by the possible planet(s) in between but fall onto the central star, although it is discussed how the gap flow rate could be larger than previously suggested. In addition, we provide evidence showing that the stellar accretion rate of HD 142527 has increased by a factor ∼7 on a timescale of 2 to 5 yr.

  9. Multi-element Doppler imaging of the CP2 star HD 3980

    NASA Astrophysics Data System (ADS)

    Nesvacil, N.; Lüftinger, T.; Shulyak, D.; Obbrugger, M.; Weiss, W.; Drake, N. A.; Hubrig, S.; Ryabchikova, T.; Kochukhov, O.; Piskunov, N.; Polosukhina, N.

    2012-01-01

    Context. In atmospheres of magnetic main-sequence stars, the diffusion of chemical elements leads to a number of observed anomalies, such as abundance spots across the stellar surface. Aims: The aim of this study was to derive a detailed picture of the surface abundance distribution of the magnetic chemically peculiar star HD 3980. Methods: Based on high-resolution, phase-resolved spectroscopic observations of the magnetic A-type star HD 3980, the inhomogeneous surface distribution of 13 chemical elements (Li, O, Si, Ca, Cr, Mn, Fe, La, Ce, Pr, Nd, Eu, and Gd) has been reconstructed. The INVERS12 code was used to invert the rotational variability in line profiles to elemental surface distributions. Results: Assuming a centered, dominantly dipolar magnetic field configuration, we find that Li, O, Mg, Pr, and Nd are mainly concentrated in the area of the magnetic poles and depleted in the regions around the magnetic equator. The high abundance spots of Si, La, Ce, Eu, and Gd are located between the magnetic poles and the magnetic equator. Except for La, which is clearly depleted in the area of the magnetic poles, no obvious correlation with the magnetic field has been found for these elements otherwise. Ca, Cr, and Fe appear enhanced along the rotational equator and the area around the magnetic poles. The intersection between the magnetic and the rotational equator constitutes an exception, especially for Ca and Cr, which are depleted in that region. Conclusions: No obvious correlation between the theoretically predicted abundance patterns and those determined in this study could be found. This can be attributed to a lack of up-to-date theoretical models, especially for rare earth elements. Table 1 is available in electronic form at http://www.aanda.org

  10. Transit confirmation and improved stellar and planet parameters for the super-Earth HD 97658 b and its host star

    SciTech Connect

    Van Grootel, V.; Gillon, M.; Scuflaire, R.; Valencia, D.; Madhusudhan, N.; Demory, B.-O.; Queloz, D.; Dragomir, D.; Howe, A. R.; Burrows, A. S.; Deming, D.; Ehrenreich, D.; Lovis, C.; Mayor, M.; Pepe, F.; Segransan, D.; Udry, S.; Seager, S.

    2014-05-01

    Super-Earths transiting nearby bright stars are key objects that simultaneously allow for accurate measurements of both their mass and radius, providing essential constraints on their internal composition. We present here the confirmation, based on Spitzer transit observations, that the super-Earth HD 97658 b transits its host star. HD 97658 is a low-mass (M {sub *} = 0.77 ± 0.05 M {sub ☉}) K1 dwarf, as determined from the Hipparcos parallax and stellar evolution modeling. To constrain the planet parameters, we carry out Bayesian global analyses of Keck-High Resolution Echelle Spectrometer (Keck-HIRES) radial velocities and Microvariability and Oscillations of STars (MOST) and Spitzer photometry. HD 97658 b is a massive (M{sub P}=7.55{sub −0.79}{sup +0.83} M{sub ⊕}) and large (R{sub P}=2.247{sub −0.095}{sup +0.098}R{sub ⊕} at 4.5 μm) super-Earth. We investigate the possible internal compositions for HD 97658 b. Our results indicate a large rocky component, of at least 60% by mass, and very little H-He components, at most 2% by mass. We also discuss how future asteroseismic observations can improve the knowledge of the HD 97658 system, in particular by constraining its age. Orbiting a bright host star, HD 97658 b will be a key target for upcoming space missions such as the Transiting Exoplanet Survey Satellite (TESS), the Characterizing Exoplanet Satellite (CHEOPS), the Planetary Transits and Oscillations of stars (PLATO), and the James Webb Space Telescope to characterize thoroughly its structure and atmosphere.

  11. NEW PRECISION ORBITS OF BRIGHT DOUBLE-LINED SPECTROSCOPIC BINARIES. V. THE AM STARS HD 434 AND 41 SEXTANTIS

    SciTech Connect

    Fekel, Francis C.; Williamson, Michael H.

    2010-11-15

    We have detected the secondary component in two previously known spectroscopic binaries, HD 434 and 41 Sex, and for the first time determined double-lined orbits for them. Despite the relatively long period of 34.26 days and a moderate eccentricity of 0.32, combined with the components' rotationally broadened lines, measurement of the primary and secondary radial velocities of HD 434 has enabled us to obtain significantly improved orbital elements. While the 41 Sex system has a much shorter period of 6.167 days and a circular orbit, the estimated V mag difference of 3.2 between its components also makes this a challenging system. The new orbital dimensions (a{sub 1} sin i and a{sub 2} sin i) and minimum masses (m{sub 1} sin{sup 3} i and m{sub 2} sin{sup 3} i) of HD 434 have accuracies of 0.8% or better, while the same quantities for 41 Sex are good to 0.5% or better. Both components of HD 434 are Am stars while the Am star primary of 41 Sex has a late-F or early-G companion. All four stars are on the main sequence. The two components of HD 434 are rotating much faster than their predicted pseudosynchronous velocities, while both components of 41 Sex are synchronously rotating. For the primary of 41 Sex, the spectrum line depth changes noted by Sreedhar Rao et al. were not detected.

  12. KNOW THE STAR, KNOW THE PLANET. V. CHARACTERIZATION OF THE STELLAR COMPANION TO THE EXOPLANET HOST STAR HD 177830

    SciTech Connect

    Roberts, Lewis C. Jr.; Beichman, Charles; Burruss, Rick; Cady, Eric; Lockhart, Thomas G.; Oppenheimer, Rebecca; Brenner, Douglas; Luszcz-Cook, Statia; Nilsson, Ricky; Crepp, Justin R.; Baranec, Christoph; Dekany, Richard; Hillenbrand, Lynne; Hinkley, Sasha; King, David; Parry, Ian R.; Pueyo, Laurent; Sivaramakrishnan, Anand; Soummer, Rémi; Rice, Emily L.; and others

    2015-10-15

    HD 177830 is an evolved K0IV star with two known exoplanets. In addition to the planetary companions it has a late-type stellar companion discovered with adaptive optics imagery. We observed the binary star system with the PHARO near-IR camera and the Project 1640 coronagraph. Using the Project 1640 coronagraph and integral field spectrograph we extracted a spectrum of the stellar companion. This allowed us to determine that the spectral type of the stellar companion is a M4 ± 1 V. We used both instruments to measure the astrometry of the binary system. Combining these data with published data, we determined that the binary star has a likely period of approximately 800 years with a semimajor axis of 100–200 AU. This implies that the stellar companion has had little or no impact on the dynamics of the exoplanets. The astrometry of the system should continue to be monitored, but due to the slow nature of the system, observations can be made once every 5–10 years.

  13. Spectroscopic pulsational frequency identification and mode determination of γ Doradus star HD 12901

    NASA Astrophysics Data System (ADS)

    Brunsden, E.; Pollard, K. R.; Cottrell, P. L.; Wright, D. J.; De Cat, P.

    2012-12-01

    Using multisite spectroscopic data collected from three sites, the frequencies and pulsational modes of the γ Doradus star HD 12901 were identified. A total of six frequencies in the range 1-2 d-1 were observed, their identifications supported by multiple line-profile measurement techniques and previously published photometry. Five frequencies were of sufficient signal-to-noise ratio for mode identification, and all five displayed similar three-bump standard deviation profiles which were fitted well with (l,m) = (1,1) modes. These fits had reduced χ2 values of less than 18. We propose that this star is an excellent candidate to test models of non-radially pulsating γ Doradus stars as a result of the presence of multiple (1,1) modes. This paper includes data taken at the Mount John University Observatory of the University of Canterbury (New Zealand), the McDonald Observatory of the University of Texas at Austin (Texas, USA) and the European Southern Observatory at La Silla (Chile).

  14. Activity and magnetic field structure of the Sun-like planet-hosting star HD 1237

    NASA Astrophysics Data System (ADS)

    Alvarado-Gómez, J. D.; Hussain, G. A. J.; Grunhut, J.; Fares, R.; Donati, J.-F.; Alecian, E.; Kochukhov, O.; Oksala, M.; Morin, J.; Redfield, S.; Cohen, O.; Drake, J. J.; Jardine, M.; Matt, S.; Petit, P.; Walter, F. M.

    2015-10-01

    We analyse the magnetic activity characteristics of the planet-hosting Sun-like star, HD 1237, using HARPS spectro-polarimetric time-series data. We find evidence of rotational modulation of the magnetic longitudinal field measurements that is consistent with our ZDI analysis with a period of 7 days. We investigate the effect of customising the LSD mask to the line depths of the observed spectrum and find that it has a minimal effect on the shape of the extracted Stokes V profile but does result in a small increase in the S/N (~7%). We find that using a Milne-Eddington solution to describe the local line profile provides a better fit to the LSD profiles in this slowly rotating star, which also affects the recovered ZDI field distribution. We also introduce a fit-stopping criterion based on the information content (entropy) of the ZDI map solution set. The recovered magnetic field maps show a strong (+90 G) ring-like azimuthal field distribution and a complex radial field dominating at mid latitudes (~45 degrees). Similar magnetic field maps are recovered from data acquired five months apart. Future work will investigate how this surface magnetic field distribution affeccts the coronal magnetic field and extended environment around this planet-hosting star.

  15. Spectroscopic signatures of magnetospheric accretion in Herbig Ae/Be stars. I. The case of HD 101412

    NASA Astrophysics Data System (ADS)

    Schöller, M.; Pogodin, M. A.; Cahuasquí, J. A.; Drake, N. A.; Hubrig, S.; Petr-Gotzens, M. G.; Savanov, I. S.; Wolff, B.; González, J. F.; Mysore, S.; Ilyin, I.; Järvinen, S. P.; Stelzer, B.

    2016-07-01

    Context. Models of magnetically-driven accretion and outflows reproduce many observational properties of T Tauri stars. This concept is not well established for the more massive Herbig Ae/Be stars. Aims: We intend to examine the magnetospheric accretion in Herbig Ae/Be stars and search for rotational modulation using spectroscopic signatures, in this first paper concentrating on the well-studied Herbig Ae star HD 101412. Methods: We used near-infrared spectroscopic observations of the magnetic Herbig Ae star HD 101412 to test the magnetospheric character of its accretion disk/star interaction. We reduced and analyzed 30 spectra of HD 101412, acquired with the CRIRES and X-shooter spectrographs installed at the VLT (ESO, Chile). The spectroscopic analysis was based on the He iλ10 830 and Paγ lines, formed in the accretion region. Results: We found that the temporal behavior of these diagnostic lines in the near-infrared spectra of HD 101412 can be explained by rotational modulation of line profiles generated by accreting gas with a period P = 20.53d±1.68d. The discovery of this period, about half of the magnetic rotation period Pm = 42.076d previously determined from measurements of the mean longitudinal magnetic field, indicates that the accreted matter falls onto the star in regions close to the magnetic poles intersecting the line-of-sight two times during the rotation cycle. We intend to apply this method to a larger sample of Herbig Ae/Be stars. Based on observations made with ESO Telescopes at the La Silla Paranal Observatory under programme IDs 087.C-0124(A), 088.C-0218(A,B,C,E), 090.C-0331(A), and 092.C-0126(A).

  16. Chromospherically active stars. 13: HD 30957: A double lined K dwarf binary

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Dadonas, Virgilijus; Sperauskas, Julius; Vaccaro, Todd R.; Patterson, L. Ronald

    1994-01-01

    HD 30957 is a double-lined spectroscopic binary with a period of 44.395 days and a modest eccentricity of 0.09. The spectral types of the components are K2-3 V and K5 V. The measured v sin i for both components is less than or equal to 3 km/s and the orbital inclination is estimated to be 69 deg. The system is relatively nearby with a parallax of 0.025 sec or a distance of 40 pc. Space motions of the system indicate that it does not belong to any of the known moving groups. Absolute surface fluxes of the Ca II H and K lines have been recomputed and indicate only modest chromospheric activity. If the stars are rotating pseudosynchronously, the lack of light variability is consistent with the value of the critical Rossby number for starspot activity.

  17. An Icy Kuiper Belt Around the Young Solar-type Star HD 181327

    NASA Technical Reports Server (NTRS)

    Lebreton, J.; Augereau, J.-C.; Thi, W.-F.; Roberge, A.; Donaldson, J; Schneider, G.; Maddison, S. T.; Menard, F.; Riviere-Marichalar, P.; Matthews, G. S.; Kamp, I.; Pinte, C.; Dent, W. R. F.; Barrado, D.; Duchene, G.; Gonzalez, J.-F.; Grady C. A.; Meeus,G.; Pantin, E.; Williams, J. P.; Woitke, P.

    2012-01-01

    Context. HD 181327 is a young main sequence F5/F6 V star belonging to the Beta Pictoris moving group (age approx.. 12 Myr). It harbors an optically thin belt of circumstellar material at radius approx.. 90 AU, presumed to result from collisions in a population of unseen planetesimals. Aims. We aim to study the dust properties in the belt in details, and to constrain the gas-to-dust ratio. Methods. We obtained far-infrared photometric observations of HD 181327 with the PACS instrument onboard the Herschel Space Observatory, complemented by new 3.2 mm observations carried with the ATCA array. The geometry of the belt is constrained with newly reduced HST/NICMOS scattered light images that allow the degeneracy between the disk geometry and the dust properties to be broken. We then use the radiative transfer code GRaTeR to compute a large grid of models, and we identify the grain models that best reproduce the spectral energy distribution (SED) through a Bayesian analysis. We attempt to detect the oxygen and ionized carbon fine-structure lines with Herschel/PACS spectroscopy, providing observables to our photochemical code ProDiMo. Results. The HST observations confirm that the dust is confined in a narrow belt. The continuum is detected with Herschel/PACS completing nicely the SED in the far-infrared. The disk is marginally resolved with both PACS and ATCA. A medium integration of the gas spectral lines only provides upper limits on the [OI] and [CII] line fluxes.We show that the HD 181327 dust disk consists of micron-sized grains of porous amorphous silicates and carbonaceous material surrounded by an important layer of ice, for a total dust mass of approx.. 0.05 Solar Mass (in grains up to 1 mm). We discuss evidences that the grains consists of fluffy aggregates. The upper limits on the gas atomic lines do not provide unambiguous constraints: only if the PAH abundance is high, the gas mass must be lower than approx. 17 Solar Mass. Conclusions. Despite the weak

  18. An Icy Kuiper-Belt Around the Young Solar-Type Star HD 181327

    NASA Technical Reports Server (NTRS)

    Lebreton, J.; Augereau, J.-C.; Thi, W.-F.; Roberge, A.; Donaldson, J.; Schneider, G.; Maddison, S. T.; Menard, F.; Riviere-Marichalar, P.; Mathews, G. S.; Kamp, I.; Pinte, C.; Dent, W. R. F.; Barrado, D.; Duchene, G.; Gonzalez, J.-F.; Grady, C. A.; Meeus, G.; Pantin, E.; Williams, J. P.; Woitke, P.

    2011-01-01

    HD 181327 is a young Main Sequence F5/F6 V star belonging to the Beta Pictoris moving group (age approx 12 Myr). It harbors an optically thin belt of circumstellar material at approx90 AU, presumed to result from collisions in a populat.ion of unseen planetesimals. Aims. We aim to study the dust properties in the belt in great details, and to constrain the gas-to-dust ratio. Methods. We obtained far-IR photometric observations of HD 181327 with the PACS instrument onboard the Herschel Space Observatory, complemented by new 3.2 nun observations carried with the ATCA array. The geometry of the belt is constrained with newly reduced HST /NICMOS scattered light images that break the degeneracy between the disk geometry and the dust properties. We then use the radiative transfer code GRaTer to compute a large grid of dust models, and we apply a Bayesian inference method to identify the grain models that best reproduce the SED. We attempt to detect the oxygen and ionized carbon fine-structure lines with Herschel/PACS spectroscopy, providing observables to our photochemical code ProDiMo. Results. The HST observations confirm that the dust is confined in a narrow belt. The continuum is detected with Herschel/PACS completing nicely the SED in the far-infrared. The disk is marginally resolved with both PACS and ATCA. A medium integration of the gas spectral lines only provides upper limits on the [OI] and [CII] line fluxes. We show that the HD 181327 dust disk consists of micron-sized grains of porous amorphous silicates and carbonaceous material surrounded by an import.ant layer of ice for a total dust mass of approx 0.05 stellar Mass. We discuss evidences that the grains consists of fluffy aggregates. The upper limits on the gas atomic lines do not provide unambiguous constraints: only if the PAH abundance is high, the gas mass must be lower than approx 17 Stellar Mass Conclusions. Despite the weak constraints on the gas disk, the age of HD 181327 and the properties of the

  19. INTEGRAL Observations of the Enigmatic Be Stars (gamma) Cassiopeiae and HD 110432

    NASA Technical Reports Server (NTRS)

    Sturner, S. J.; Shrader, C. R.

    2007-01-01

    We present the results of a hard X-ray study of the Be stars gamma Cassiopeiae and HD 110432 based on observations made with the INTEGRAL observatory. These stars are known to be moderately strong, X-ray sources (L(sub x) approx. equal to = 10(sup 32)-10(sup 33) erg per second). These values are at the extreme high end of the known luminosity distribution for active coronal systems, but several orders of magnitude below typical X-ray binaries. The hard X-ray spectra for these systems are quite similar. They can be well fitted by either optically thin thermal plasma models with kT = 12.5 - 14 keV or a cutoff powerlaw + gaussian line model with photon indices in the 1.3 - 1.5 range and a line energy of 6.7 keV. The 20-50 keV light curves show no evidence for flaring and no significant evidence for periodic variability. It has been proposed that the X-ray emission is due to either accretion onto a white dwarf companion or magnetic activity near the surface of the Be star. We discuss in detail the pros and cons of each scenario towards explaining our spectral and temporal results. Given that both thermal and nonthermal models fit the data equally well, we cannot use the spectra to delineate between these two scenarios. Recent observations indicate that gamma Cas has a approx. 1 solar mass companion in a 203.59 day orbit. This is consistent with the white dwarf - Be star binary model but the lack of periodic modulation of the flux on this timescale calls this conclusion into question. On the other hand the lack of flaring activity may rule against the magnetic activity model. We discuss advances in observations and theory that need to be made to resolve the origin of these systems.

  20. INTEGRAL Observations of the Enigmatic Be Stars γ Cassiopeiae and HD 110432

    NASA Astrophysics Data System (ADS)

    Sturner, Steven J.; Shrader, C. R.

    2006-09-01

    We present the results of a hard X-ray study of the Be stars γ Cassiopeiae and HD 110432 based on observations made with the INTEGRAL observatory. These stars are known to be moderately strong, X-ray sources (Lx 1032-1033 erg s-1). These values are at the extreme high end of the known luminosity distribution for active coronal systems, but several orders of magnitude below typical X-ray binaries. The hard X-ray spectra for these systems are quite similar. They can be well fitted by either optically thin thermal plasma models with kT = 12.5 - 14 keV or a cutoff powerlaw + gaussian line model with photon indices in the 1.3 - 1.5 range and a line energy of 6.7 keV. The 20-50 keV light curves show no evidence for flaring and no significant evidence for periodic variability. It has been proposed that the X-ray emission is due to either accretion onto a white dwarf companion or magnetic activity near the surface of the Be star. We discuss in detail the pros and cons of each scenario towards explaining our spectral and temporal results. Given that both thermal and nonthermal models fit the data equally well, we cannot use the spectra to delineate between these two scenarios. Recent observations indicate that γ Cas has a 1 solar mass companion in a 203.59 day orbit. This is consistent with the white dwarf - Be star binary model but the lack of periodic modulation of the flux on this timescale calls this conclusion into question. On the other hand the lack of flaring activity may rule against the magnetic activity model. We discuss advances in observations and theory that need to be made to resolve the origin of these systems.

  1. Benchmark stars for Gaia Fundamental properties of the Population II star HD 140283 from interferometric, spectroscopic, and photometric data

    NASA Astrophysics Data System (ADS)

    Creevey, O. L.; Thévenin, F.; Berio, P.; Heiter, U.; von Braun, K.; Mourard, D.; Bigot, L.; Boyajian, T. S.; Kervella, P.; Morel, P.; Pichon, B.; Chiavassa, A.; Nardetto, N.; Perraut, K.; Meilland, A.; Mc Alister, H. A.; ten Brummelaar, T. A.; Farrington, C.; Sturmann, J.; Sturmann, L.; Turner, N.

    2015-03-01

    Metal-poor halo stars are important astrophysical laboratories that allow us to unravel details about many aspects of astrophysics, including the chemical conditions at the formation of our Galaxy, understanding the processes of diffusion in stellar interiors, and determining precise effective temperatures and calibration of colour-effective temperature relations. To address any of these issues the fundamental properties of the stars must first be determined. HD 140283 is the closest and brightest metal-poor Population II halo star (distance = 58 pc and V = 7.21), an ideal target that allows us to approach these questions, and one of a list of 34 benchmark stars defined for Gaia astrophysical parameter calibration. In the framework of characterizing these benchmark stars, we determined the fundamental properties of HD 140283 (radius, mass, age, and effective temperature) by obtaining new interferometric and spectroscopic measurements and combining them with photometry from the literature. The interferometric measurements were obtained using the visible interferometer VEGA on the CHARA array and we determined a 1D limb-darkened angular diameter of θ1D = 0.353 ± 0.013 milliarcsec. Using photometry from the literature we derived the bolometric flux in two ways: a zero reddening solution (AV = 0.0 mag) of Fbol of 3.890 ± 0.066 × 10-8 erg s-1 cm-2, and a maximum of AV = 0.1 mag solution of 4.220 ± 0.067 × 10-8 erg s-1 cm-2. The interferometric Teff is thus between 5534 ± 103 K and 5647 ± 105 K and its radius is R = 2.21 ± 0.08R⊙. Spectroscopic measurements of HD 140283 were obtained using HARPS, NARVAL, and UVES and a 1D LTE analysis of Hα line wings yielded Teffspec = 5626 ± 75 K. Using fine-tuned stellar models including diffusion of elements we then determined the mass M and age t of HD 140283. Once the metallicity has been fixed, the age of the star depends on M, initial helium abundance Yi, andmixing-length parameter α, only two of which are

  2. FCAPT uvby Photometry of the mCP Stars HD 86592, HR 4330, HR 6958, and HR 7786

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.

    2008-04-01

    New differential Strömgren uvby Four College Automated Photoelectric Telescope (FCAPT) observations of four magnetic CP stars HD 86592, HR 4330, HR 6958, and HR 7786 are presented. These observations are analyzed along with published FCAPT data to improve the periods and the light curves. The period of HD 86592 is that of Babel & North, 2.886669 days. The new periods of HR 4330, HR 6958, and HR 7786 are 3.152, 18.0642, and 8.5295 days, respectively, almost the same as their previous values from FCAPT data. The first three stars can be characterized as having constant light curves and periods. However, the small differences among the seasonal light curves of HR 7786 indicate it is a star whose rotational axis is precessing about its magnetic axis.

  3. Long Baseline Interferometry, a Powerful Tool to Study Stars with the B[e] Phenomenon: The Case of HD 50138*

    NASA Astrophysics Data System (ADS)

    Borges Fernandes, M.

    2012-12-01

    HD 50138 is one of the closest stars with the B[e] phenomenon. However, up to now its evolutionary stage is not well known. Thanks to optical high-resolution data from the FEROS spectrograph (ESO, La Silla), it was possible to derive the physical parameters of this star (B6-7 III-V) and the circum- and interstellar extinction. This object can represent a link between Be and B[e] stars, and based on its intense spectral variations, we tentatively suggest that a new shell phase could have taken place prior to our observations in 2007. From the high spatial resolution provided by AMBER and MIDI (VLTI/ESO), we have identified the presence of a gaseous and dusty circumstellar disk. In addition, we could also derive the structure, inclination related to line of sight, and orientation onto the sky-plane of the circumstellar disk of HD 50138.

  4. The unstable fate of the planet orbiting the A star in the HD 131399 triple stellar system

    NASA Astrophysics Data System (ADS)

    Veras, Dimitri; Mustill, Alexander J.; Gänsicke, Boris T.

    2017-02-01

    Validated planet candidates need not lie on long-term stable orbits, and instability triggered by post-main-sequence stellar evolution can generate architectures which transport rocky material to white dwarfs, hence polluting them. The giant planet HD 131399Ab orbits its parent A star at a projected separation of about 50-100 au. The host star, HD 131399A, is part of a hierarchical triple with HD 131399BC being a close binary separated by a few hundred au from the A star. Here, we determine the fate of this system, and find the following: (i) Stability along the main sequence is achieved only for a favourable choice of parameters within the errors. (ii) Even for this choice, in almost every instance, the planet is ejected during the transition between the giant branch and white dwarf phases of HD 131399A. This result provides an example of both how the free-floating planet population may be enhanced by similar systems and how instability can manifest in the polluted white dwarf progenitor population.

  5. Probing the circumstellar environment of the Herbig Be star HD 100546 with FUSE.

    NASA Astrophysics Data System (ADS)

    Deleuil, M.; Lecavelier des Etangs, A.; Bouret, J.-C.; Roberge, A.; Vidal-Madjar, A.; Feldman, P. D.; Ferlet, R.; Martin, C.

    2002-12-01

    We present an analysis of Far Ultraviolet Spectroscopic Explorer (FUSE) spectra probing the gaseous circumstellar environment of the Herbig Be star HD 100546. Numerous narrow absorption lines of circumstellar origin are observed from molecular and atomic gas, neutral and weakly ionized. At short wavelengths where the stellar flux is undetected, strong and broad emission lines due to highly ionised species such as C III and O VI are present. These lines formed in a dense and hot gas, collisionally heated, probe a region which extends over a few stellar radii above the star's surface. Comparison of two spectra recorded two years apart, reveal strong variations not limited to the atomic circumstellar lines as previously reported but which also affect the photospheric flux itself as well as the emission lines at short wavelengths. Our results highlight a complex circumstellar environment with evidences of a high temperature emission gas related to a chromospheric complex close to the stellar surface, sporadic wind and accretion phenomena which affect mainly volatile species like N I and O I(1D). Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.

  6. THE LICK-CARNEGIE SURVEY: A NEW TWO-PLANET SYSTEM AROUND THE STAR HD 207832

    SciTech Connect

    Haghighipour, Nader; Butler, R. Paul; Rivera, Eugenio J.; Vogt, Steven S.

    2012-09-01

    Keck/HIRES precision radial velocities of HD 207832 indicate the presence of two Jovian-type planetary companions in Keplerian orbits around this G star. The planets have minimum masses of Msin i = 0.56 M{sub Jup} and 0.73 M{sub Jup}, with orbital periods of {approx}162 and {approx}1156 days, and eccentricities of 0.13 and 0.27, respectively. Stroemgren b and y photometry reveals a clear stellar rotation signature of the host star with a period of 17.8 days, well separated from the period of the radial velocity variations, reinforcing their Keplerian origin. The values of the semimajor axes of the planets suggest that these objects have migrated from the region of giant planet formation to closer orbits. In order to examine the possibility of the existence of additional (small) planets in the system, we studied the orbital stability of hypothetical terrestrial-sized objects in the region between the two planets and interior to the orbit of the inner body. Results indicated that stable orbits exist only in a small region interior to planet b. However, the current observational data offer no evidence for the existence of additional objects in this system.

  7. Magnetic fields on young, moderately rotating Sun-like stars - II. EK Draconis (HD 129333)

    NASA Astrophysics Data System (ADS)

    Waite, I. A.; Marsden, S. C.; Carter, B. D.; Petit, P.; Jeffers, S. V.; Morin, J.; Vidotto, A. A.; Donati, J.-F.; BCool Collaboration

    2017-02-01

    The magnetic fields, activity and dynamos of young solar-type stars can be empirically studied using time series of spectropolarimetric observations and tomographic imaging techniques such as Doppler imaging and Zeeman-Doppler imaging. In this paper, we use these techniques to study the young Sun-like star EK Draconis (SpType: G1.5V, HD 129333) using ESPaDOnS at the Canada-France-Hawaii Telescope and NARVAL at the Télescope Bernard Lyot. This multi-epoch study runs from late 2006 until early 2012. We measure high levels of chromospheric activity indicating an active, and varying, chromosphere. Surface brightness features were constructed for all available epochs. The 2006/2007 and 2008 data show large spot features appearing at intermediate latitudes. However, the 2012 data indicate a distinctive polar spot. We observe a strong, almost unipolar, azimuthal field during all epochs, which is similar to that observed on other Sun-like stars. Using magnetic features, we determined an average equatorial rotational velocity, Ωeq, of ∼2.50 ± 0.08 rad d- 1. High levels of surface differential rotation were measured with an average rotational shear, ΔΩ, of {˜ }0.27_{-0.26}^{+0.24} rad d- 1. During an intensively observed 3-month period, from 2006 December until 2007 February, the magnetic field went from predominantly toroidal (∼80 per cent) to a more balanced poloidal-toroidal (∼40-60 per cent) field. Although the large-scale magnetic field evolved over the epochs of our observations, no polarity reversals were found in our data.

  8. A resolved, au-scale gas disk around the B[e] star HD 50138

    NASA Astrophysics Data System (ADS)

    Ellerbroek, L. E.; Benisty, M.; Kraus, S.; Perraut, K.; Kluska, J.; le Bouquin, J. B.; Borges Fernandes, M.; Domiciano de Souza, A.; Maaskant, K. M.; Kaper, L.; Tramper, F.; Mourard, D.; Tallon-Bosc, I.; ten Brummelaar, T.; Sitko, M. L.; Lynch, D. K.; Russell, R. W.

    2015-01-01

    HD 50138 is a B[e] star surrounded by a large amount of circumstellar gas and dust. Its spectrum shows characteristics which may indicate either a pre- or a post-main-sequence system. Mapping the kinematics of the gas in the inner few au of the system contributes to a better understanding of its physical nature. We present the first high spatial and spectral resolution interferometric observations of the Brγ line of HD 50138, obtained with VLTI/AMBER. The line emission originates in a region more compact (up to 3 au) than the continuum-emitting region. Blue- and red-shifted emission originates from the two different hemispheres of an elongated structure perpendicular to the polarization angle. The velocity of the emitting medium decreases radially. An overall offset along the NW direction between the line- and continuum-emitting regions is observed. We compare the data with a geometric model of a thin Keplerian disk and a spherical halo on top of a Gaussian continuum. Most of the data are well reproduced by this model, except for the variability, the global offset and the visibility at the systemic velocity. The evolutionary state of the system is discussed; most diagnostics are ambiguous and may point either to a post-main-sequence or a pre-main-sequence nature. Based on observations performed with X-Shooter (program 090.D-0212) and CRIRES (program 084.C-0668), mounted on the ESO Very Large Telescope, on Cerro Paranal, Chile, and AMBER mounted on the Very Large Telescope Interferometer (programs 082.C-0621, 082.C-0657, 083.C-0144, 084.C-0187, 084.C-0668, 084.C-0983, 384.D-0482, and 092.C-0376(B)).Figure 4 and Appendix A are available in electronic form at http://www.aanda.org

  9. The discovery of a planetary candidate around the evolved low-mass Kepler giant star HD 175370

    NASA Astrophysics Data System (ADS)

    Hrudková, M.; Hatzes, A.; Karjalainen, R.; Lehmann, H.; Hekker, S.; Hartmann, M.; Tkachenko, A.; Prins, S.; Van Winckel, H.; De Nutte, R.; Dumortier, L.; Frémat, Y.; Hensberge, H.; Jorissen, A.; Lampens, P.; Laverick, M.; Lombaert, R.; Pápics, P. I.; Raskin, G.; Sódor, Á.; Thoul, A.; Van Eck, S.; Waelkens, C.

    2017-01-01

    We report on the discovery of a planetary companion candidate with a minimum mass M sin i = 4.6 ± 1.0 MJupiter orbiting the K2 III giant star HD 175370 (KIC 007940959). This star was a target in our programme to search for planets around a sample of 95 giant stars observed with Kepler. This detection was made possible using precise stellar radial velocity measurements of HD 175370 taken over five years and four months using the coudé echelle spectrograph of the 2-m Alfred Jensch Telescope and the fibre-fed echelle spectrograph High Efficiency and Resolution Mercator Echelle Spectrograph of the 1.2-m Mercator Telescope. Our radial velocity measurements reveal a periodic (349.5 ± 4.5 d) variation with a semi-amplitude K = 133 ± 25 m s- 1, superimposed on a long-term trend. A low-mass stellar companion with an orbital period of ˜88 yr in a highly eccentric orbit and a planet in a Keplerian orbit with an eccentricity e = 0.22 are the most plausible explanation of the radial velocity variations. However, we cannot exclude the existence of stellar envelope pulsations as a cause for the low-amplitude radial velocity variations and only future continued monitoring of this system may answer this uncertainty. From Kepler photometry, we find that HD 175370 is most likely a low-mass red giant branch or asymptotic giant branch star.

  10. Chandra Characterization of X-Ray Emission in the Young F-Star Binary System HD 113766

    NASA Astrophysics Data System (ADS)

    Lisse, C. M.; Christian, D. J.; Wolk, S. J.; Günther, H. M.; Chen, C. H.; Grady, C. A.

    2017-02-01

    Using Chandra, we have obtained imaging X-ray spectroscopy of the 10–16 Myr old F-star binary HD 113766. We individually resolve the 1.″4 separation binary components for the first time in the X-ray and find a total 0.3–2.0 keV luminosity of 2.2 × 1029 erg s‑1, consistent with previous RASS estimates. We find emission from the easternmost, infrared-bright, dusty member HD 113766A to be only ∼10% that of the western, infrared-faint member HD 113766B. There is no evidence for a 3rd late-type stellar or substellar member of HD 113766 with Lx > 6 × 1025 erg s‑1 within 2‧ of the binary pair. The ratio of the two stars’ X-ray luminosity is consistent with their assignments as F2V and F6V by Pecaut et al. The emission is soft for both stars, kTApec = 0.30–0.50 keV, suggesting X-rays produced by stellar rotation and/or convection in young dynamos, but not accretion or outflow shocks, which we rule out. A possible 2.8 ± 0.15 (2σ) hr modulation in the HD 113766B X-ray emission is seen, but at very low confidence and of unknown provenance. Stellar wind drag models corresponding to Lx ∼ 2 × 1029 erg s‑1 argue for a 1 mm dust particle lifetime around HD 113766B of only ∼90,0000 years, suggesting that dust around HD 113766B is quickly removed, whereas 1 mm sized dust around HD 113766A can survive for >1.5 × 106 years. At 1028–1029 erg s‑1 X-ray luminosity, astrobiologically important effects, like dust warming and X-ray photolytic organic synthesis, are likely for any circumstellar material in the HD 113766 systems.

  11. Elemental abundance analyses with coadded DAO spectrograms. I - The field horizontal-branch stars HD-64488, 109995 and 161817

    NASA Technical Reports Server (NTRS)

    Adelman, Saul J.; Hill, Graham

    1987-01-01

    It is possible to improve the quality of elemental-abundance analyses by using higher-S/N data than has been the practice at high resolution. The procedures developed at the Dominion Astrophysical Observatory to coadd high-dispersion coude spectrograms are used with a minimum of 10 6.5-A/mm IIa-O spectrograms of each of three field hoorizontal-branch (FHB) A stars to increase the S/N of the photographic data over a considerable wavelength region. Fine analyses of the sharp-lined prototype FHB stars HD 109995 and 161817 show an internal consistency which justifies this effort. Their photospheric elemental abundances are similar to those of Population II globular cluster giants. As their photometric and spectrophotometric properties are similar to blue HB stars in such clusters, they are confirmed to be the brighter analogs of such stars. HD 64488, which is photometrically and spectrophotometrically similar to the FHB stars, is found to be metal-poor (Fe/H = -1) with much broader lines (v sin i = 147 km/s). The implications of the abundance anomalies of all three stars are discussed.

  12. HD 50844: a new look at δ Scuti stars from CoRoT space photometry

    NASA Astrophysics Data System (ADS)

    Poretti, E.; Michel, E.; Garrido, R.; Lefèvre, L.; Mantegazza, L.; Rainer, M.; Rodríguez, E.; Uytterhoeven, K.; Amado, P. J.; Martín-Ruiz, S.; Moya, A.; Niemczura, E.; Suárez, J. C.; Zima, W.; Baglin, A.; Auvergne, M.; Baudin, F.; Catala, C.; Samadi, R.; Alvarez, M.; Mathias, P.; Paparò, M.; Pápics, P.; Plachy, E.

    2009-10-01

    Context: Aims: This work presents the results obtained by CoRoT on HD 50844, the only δ Sct star observed in the CoRoT initial run (57.6 d). The aim of these CoRoT observations was to investigate and characterize for the first time the pulsational behaviour of a δ Sct star, when observed at a level of precision and with a much better duty cycle than from the ground. Methods: The 140 016 datapoints were analysed using independent approaches (SigSpec software and different iterative sine-wave fittings) and several checks performed (splitting of the timeseries in different subsets, investigation of the residual light curves and spectra). A level of 10-5 mag was reached in the amplitude spectra of the CoRoT timeseries. The space monitoring was complemented by ground-based high-resolution spectroscopy, which allowed the mode identification of 30 terms. Results: The frequency analysis of the CoRoT timeseries revealed hundreds of terms in the frequency range 0-30 d-1. All the cross-checks confirmed this new result. The initial guess that δ Sct stars have a very rich frequency content is confirmed. The spectroscopic mode identification gives theoretical support since very high-degree modes (up to ℓ=14) are identified. We also prove that cancellation effects are not sufficient in removing the flux variations associated to these modes at the noise level of the CoRoT measurements. The ground-based observations indicate that HD 50844 is an evolved star that is slightly underabundant in heavy elements, located on the Terminal Age Main Sequence. Probably due to this unfavourable evolutionary status, no clear regular distribution is observed in the frequency set. The predominant term (f_1=6.92 d-1) has been identified as the fundamental radial mode combining ground-based photometric and spectroscopic data. Conclusions: The CoRoT space mission was developed and is operated by the French space agency CNES, with participation of ESA's RSSD and Science Programmes, Austria

  13. Imaging an 80 au Radius Dust Ring around the F5V Star HD 157587

    NASA Astrophysics Data System (ADS)

    Millar-Blanchaer, Maxwell A.; Wang, Jason J.; Kalas, Paul; Graham, James R.; Duchêne, Gaspard; Nielsen, Eric L.; Perrin, Marshall; Moon, Dae-Sik; Padgett, Deborah; Metchev, Stanimir; Ammons, S. Mark; Bailey, Vanessa P.; Barman, Travis; Bruzzone, Sebastian; Bulger, Joanna; Chen, Christine H.; Chilcote, Jeffrey; Cotten, Tara; De Rosa, Robert J.; Doyon, Rene; Draper, Zachary H.; Esposito, Thomas M.; Fitzgerald, Michael P.; Follette, Katherine B.; Gerard, Benjamin L.; Greenbaum, Alexandra Z.; Hibon, Pascale; Hinkley, Sasha; Hung, Li-Wei; Ingraham, Patrick; Johnson-Groh, Mara; Konopacky, Quinn; Larkin, James E.; Macintosh, Bruce; Maire, Jérôme; Marchis, Franck; Marley, Mark S.; Marois, Christian; Matthews, Brenda C.; Oppenheimer, Rebecca; Palmer, David; Patience, Jennifer; Poyneer, Lisa; Pueyo, Laurent; Rajan, Abhijith; Rameau, Julien; Rantakyrö, Fredrik T.; Savransky, Dmitry; Schneider, Adam C.; Sivaramakrishnan, Anand; Song, Inseok; Soummer, Remi; Thomas, Sandrine; Vega, David; Wallace, J. Kent; Ward-Duong, Kimberly; Wiktorowicz, Sloane; Wolff, Schuyler

    2016-11-01

    We present H-band near-infrared polarimetric imaging observations of the F5V star HD 157587 obtained with the Gemini Planet Imager (GPI) that reveal the debris disk as a bright ring structure at a separation of ˜80-100 au. The new GPI data complement recent Hubble Space Telescope/STIS observations that show the disk extending out to over 500 au. The GPI image displays a strong asymmetry along the projected minor axis as well as a fainter asymmetry along the projected major axis. We associate the minor and major axis asymmetries with polarized forward scattering and a possible stellocentric offset, respectively. To constrain the disk geometry, we fit two separate disk models to the polarized image, each using a different scattering phase function. Both models favor a disk inclination of ˜70° and a 1.5 ± 0.6 au stellar offset in the plane of the sky along the projected major axis of the disk. We find that the stellar offset in the disk plane, perpendicular to the projected major axis is degenerate with the form of the scattering phase function and remains poorly constrained. The disk is not recovered in total intensity due in part to strong adaptive optics residuals, but we recover three point sources. Considering the system’s proximity to the galactic plane and the point sources’ positions relative to the disk, we consider it likely that they are background objects and unrelated to the disk’s offset from the star.

  14. Frequency Determination for the Slowly Pulsating B Star, HD21071, From Combined Geneva and Stromgren Photometry

    NASA Astrophysics Data System (ADS)

    Sims, Melissa; Dukes, R. J., Jr.

    2006-12-01

    This project is comparison of several studies done on the variable star HD21071, which was previously determined to be Slowly Pulsating B star by Waelkens, et. al. (Astron. Astrophys. 330, 215-221, 1998) with a suggested period of .841 day (1.19 c d-1). Several later studies including Mills, L. R., et. al. (BAAS 31, 1482, 1999) and Andrews, J. E, et. al. (AAS Meeting 203, #83.14, 2003) confirmed the .841 period and tentatively suggested other possible periods based on new data, including 0.704 day (1.42 c d-1), 0.775 day (1.29 c d-1), and 1.14 day (0.878 c d-1) periods. This project merges Geneva V data and data from the y filter from the FCAPT data in the Stromgren uvby system by using a bilinear transformation from Harmanec et. al. (Astron. Astrophys. 369, 1140, 2001). Frequencies were determined using the Period04 program, which utilizes a least square fitting technique, to determine frequencies in the two data sets separately. We then analyzed the merged data set resulting in confirmation of the periods found in the individual data sets. The reality of the these frequencies was tested using multiple methods including least squares analysis and a check of the signal to noise ratio. We would like to thank Connie Aerts and Peter De Cat for providing the Geneva data as well as a copy of their preliminary analysis of this data. This work has been supported by NSF Grant AST-0071260 & AST-050755

  15. A four-planet system orbiting the K0V star HD 141399

    SciTech Connect

    Vogt, Steven S.; Rivera, Eugenio J.; Kibrick, Robert; Burt, Jennifer; Hanson, Russell; Laughlin, Gregory; Meschiari, Stefano; Henry, Gregory W.

    2014-06-01

    We present precision radial velocity (RV) data sets from Keck-HIRES and from Lick Observatory's new Automated Planet Finder Telescope and Levy Spectrometer on Mt. Hamilton that reveal a multiple-planet system orbiting the nearby, slightly evolved, K-type star HD 141399. Our 91 observations over 10.5 yr suggest the presence of four planets with orbital periods of 94.35, 202.08, 1070.35, and 3717.35 days and minimum masses of 0.46, 1.36, 1.22, and 0.69 M{sub J} , respectively. The orbital eccentricities of the three inner planets are small, and the phase curves are well sampled. The inner two planets lie just outside the 2:1 resonance, suggesting that the system may have experienced dissipative evolution during the protoplanetary disk phase. The fourth companion is a Jupiter-like planet with a Jupiter-like orbital period. Its orbital eccentricity is consistent with zero, but more data will be required for an accurate eccentricity determination.

  16. Zeeman effect in the X-ray star candidates HD 77581 and theta super 2 Orionis.

    NASA Technical Reports Server (NTRS)

    Kemp, J. C.; Wolstencroft, R. D.

    1973-01-01

    The discovery of Zeeman effects is reported in HD 77581 and theta super 2 Orionis, optical candidates for the X-ray sources Vela XR-1 and 2U 0525-06, respectively. The maximum longitudinal magnetic fields recorded were -10,000 G in HD 77581 and +1500 G in theta super 2 Ori. Various polarimetric data are also given, including evidence for a variable linear polarization in HD 77581.

  17. The C2H, C2, and CN electronic absorption bands in the carbon star HD 19557

    NASA Technical Reports Server (NTRS)

    Goebel, J. H.; Bregman, J. D.; Cooper, D. M.; Goorvitch, D.; Langhoff, S. R.; Witteborn, F. C.

    1983-01-01

    Infrared spectrophotometry of the R-type carbon star HD 19557 is presented. Two unusual spectroscopic features are seen: a 3.1 micron band is lacking and a 2.8 micron band is present. Identifications are proposed for three previously unreported stellar absorption bands with electronic sequences of C2, CN, and C2H. The latter is proposed to be responsible for the 2.8 micron feature. The atmospheric structure of the star is studied with synthetic spectra, and an effective temperature between 2600 K and 3000 K is suggested. No SiC emission is seen at 11.3 microns, indicating that grain formation is not a viable process around the star. The lack of dust in R stars may suggest a salient difference between R and N types.

  18. Discovery of a 14.5 kG magnetic field in the NGC 2516 star HD 66318

    NASA Astrophysics Data System (ADS)

    Bagnulo, S.; Landstreet, J. D.; Lo Curto, G.; Szeifert, T.; Wade, G. A.

    2003-05-01

    We have been searching for magnetic Ap stars in open clusters, in order to clarify the time evolution of magnetic fields in middle main sequence stars from the ZAMS to the TAMS. We have discovered that the star HD 66318 in the open cluster NGC 2516 has an extraordinarily large magnetic field: the measured mean longitudinal component Bl ~ 4.5 kG, and the mean field modulus Bs ~ 14.5 kG. This star thus has one of the largest fields so far discovered in a non-degenerate star, and the largest field known in a current Ap star cluster member. We estimate that HD 66318 has completed about 16 +/- 5% of its main sequence life. It thus appears to contradict the hypothesis of Hubrig et al. that magnetic fields are only found in stars that have completed at least 30% of their main sequence lifetimes. There is no indication that the spectrum or brightness of the star is variable, and the spectral lines are very sharp. The star probably has a very long rotation period (years). We have modelled some parts of the observed spectrum, assuming that the chemical composition is uniform both horizontally and vertically, and using a simple multipolar expansion for the field structure; although our model does not reproduce exactly the observed spectrum, it is clear that the atmospheric chemical composition of the star is very peculiar, with Ti, Cr and Fe overabundant by between 1.5 and 2.5 dex. Both La II and III are apparently about 4 dex overabundant. In contrast, evidence for the presence of other rare earths is difficult to find in the spectrum. It appears that Ce III, Pr III, Nd II and III, and Eu II are detected with inferred overabundances ranging between 1.5 and 5 dex, but for most of these elements, the abundance of the non-detected ionization state is significantly lower than that inferred for the detected state. HD 66318 thus seems to exhibit strong discrepancies between abundances deduced for different ionization states of rare earths, a phenomenon so far found only in

  19. THE DISCOVERY OF A STRONG MAGNETIC FIELD AND COROTATING MAGNETOSPHERE IN THE HELIUM-WEAK STAR HD 176582

    SciTech Connect

    Bohlender, David A.; Monin, Dmitry

    2011-05-15

    We report the detection of a strong, reversing magnetic field and variable H{alpha} emission in the bright helium-weak star HD 176582 (HR 7185). Spectrum, magnetic, and photometric variability of the star are all consistent with a precisely determined period of 1.5819840 {+-} 0.0000030 days which we assume to be the rotation period of the star. From the magnetic field curve, and assuming a simple dipolar field geometry, we derive a polar field strength of approximately 7 kG and a lower limit of 52 deg. for the inclination of the rotation axis. However, based on the behavior of the H{alpha} emission, we adopt a large inclination angle of 85 deg. and this leads to a large magnetic obliquity of 77{sup 0}. The H{alpha} emission arises from two distinct regions located at the intersections of the magnetic and rotation equators and which corotate with the star at a distance of about 3.5 R{sub *} above its surface. We estimate that the emitting regions have radial and meridional sizes on the order of 2 R{sub *} and azimuthal extents (perpendicular to the magnetic equator) of less than approximately 0.6 R{sub *}. HD 176582 therefore appears to show many of the cool magnetospheric phenomena as that displayed by other magnetic helium-weak and helium-strong stars such as the prototypical helium-strong star {sigma} Ori E. The observations are consistent with current models of magnetically confined winds and rigidly rotating magnetospheres for magnetic Bp stars.

  20. Abundances of the light elements from UV (HST) and red (ESO) spectra in the very old star HD 84937

    NASA Astrophysics Data System (ADS)

    Spite, M.; Peterson, R. C.; Gallagher, A. J.; Barbuy, B.; Spite, F.

    2017-03-01

    Aims: In order to provide a better basis for the study of mechanisms of nucleosynthesis of the light elements beyond hydrogen and helium in the oldest stars, the abundances of C, O, Mg, Si, P, S, K, and Ca have been derived from UV-HST and visible-ESO high resolution spectra in the old, very metal-poor star HD 84937, at a metallicity that is 1/200 that of the Sun's. For this halo main-sequence turnoff star, the abundance determination of P and S are the first published determinations. Methods: The LTE profiles of the lines were computed and fitted to the observed spectra. Wherever possible, we compared the abundances derived from the UV spectrum to abundances derived from the visible or near-infrared spectra, and also corrected the derived abundances for non-LTE effects. Three-dimensional (3D) CO5BOLD model atmospheres have been used to determine the abundances of C and O from molecular CH and OH bands. Results: The abundances of these light elements relative to iron in HD 84937 are found to agree well with the abundances of these elements in classical metal-poor stars. Our HD 84937 carbon abundance determination points toward a solar (or mildly enhanced above solar) value of [C/Fe]. The modest overabundance of the α elements of even atomic number Z, typical of halo turnoff stars, is confirmed in this example. The odd-Z element P is found to be somewhat deficient in HD 84937, at [P/Fe] = -0.32, which is again consistent with the handful of existing determinations for turnoff stars of such low metallicity. We show that the abundance of oxygen, deduced from the OH band from 3D computations, is not compatible with the abundance deduced from the red oxygen triplet. This incompatibility is explained by the existence of a chromosphere heating the shallow layers of the atmosphere where the OH band, in 3D computations, is mainly formed. Conclusions: The abundance ratios are compared to the predictions of models of galactic nucleosynthesis and evolution. Based on

  1. Low-amplitude variations detected by CoRoT in the B8IIIe star HD 175869

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Soto, J.; Floquet, M.; Samadi, R.; Neiner, C.; Garrido, R.; Fabregat, J.; Frémat, Y.; Diago, P. D.; Huat, A.-L.; Leroy, B.; Emilio, M.; Hubert, A.-M.; Andrade, O. Thizy L.; de Batz, B.; Janot-Pacheco, E.; Espinosa Lara, F.; Martayan, C.; Semaan, T.; Suso, J.; Auvergne, M.; Chaintreuil, S.; Michel, E.; Catala, C.

    2009-10-01

    Context: The origin of the short-term variability in Be stars remains a matter of controversy. Pulsations and rotational modulation are the components of the favored hypothesis. Aims: We present our analysis of CoRoT data of the B8IIIe star HD 175869 observed during the first short run in the center direction (SRC1). Methods: We review both the instrumental effects visible in the CoRoT light curve and the analysis methods used by the CoRoT Be team. We applied these methods to the CoRoT light curve of the star HD 175869. A search for line-profile variations in the spectroscopic data was also performed. We also searched for a magnetic field, by applying the LSD technique to spectropolarimetric data. Results: The light curve exhibits low-amplitude variations of the order of 300 μmag with a double wave shape. A frequency within the range determined for the rotational frequency and 6 of its harmonics are detected. The main frequency and its first harmonic exhibit amplitude variations of a few days. Other significant frequencies of low-amplitude from 25 to a few μmag are also found. The analysis of line profiles from ground-based spectroscopic data does not detect any variation. In addition, no Zeeman signature was found. Conclusions: Inhomogeneities caused by stellar activity in or just above the photosphere are proposed to produce the photometric variability detected by CoRoT in the Be star HD 175869. The hypothesis that non-radial pulsations are the origin of these variations cannot be excluded.

  2. Optical and X-ray studies of chromospherically active stars: FR Cancri, HD 95559 and LO Pegasi

    NASA Technical Reports Server (NTRS)

    Pandey, J. C.; Singh, K. P.; Drake, S. A.; Sagar, R.

    2005-01-01

    We present a multiwavelength study of three chromospherically active stars, namely FR Cnc (= BD +16 degrees 1753), HD 95559 and LO Peg (=BD +22 degrees 4409), including newly obtained optical photometry, (for FR Cnc) low-resolution optical spectroscopy, as well as archival IR and X-ray observations. The BVR photometry carried out during the years 2001 - 2004 has found significant photometric variability to be present in all three stars. For FR Cnc, a photometric period 0.826685 +/- 0.000034 d has been established. The strong variation in the phase and amplitude of the FR Cnc light curves when folded on this period implies the presence of evolving and migrating spots or spot groups on its surface. Two independent spots with migration periods of 0.97 and 0.93 years respectively are inferred. The photometry of HD 95559 suggests the formation of a spot (group) during the interval of our observations. We infer the existence of two independent spots or groups in the photosphere of LO Peg, one of which has a migration period of 1.12 years. The optical spectroscopy of FR Cnc carried out during 2002-2003, reveals the presence of strong and variable Ca I1 H and K, H(sub beta) and H(sub alpha) emission features indicative of high level of chromospheric activity. The value of 5.3 for the ratio of the excess emission in H(sub alpha) to H(sub beta), EH(sub alpha)/EH(sub beta), suggests that the chromospheric emission may arise from an extended off-limb region. We have searched for the presence of color excesses in the near-IR JHK bands of these stars using 2MASS data, but none of them appear to have any significant color excess. We have also analyzed archival X-ray observations of HD 95559 and LO Peg carried out by with the ROSAT observatory. The best fit models to their X-ray spectra imply the presence of two coronal plasma components of differing temperatures and with sub-solar metal abundances. The inferred emission measures and temperatures of these systems are similar to

  3. Evolutionary status of the Of?p star HD 148937 and of its surrounding nebula NGC 6164/5

    NASA Astrophysics Data System (ADS)

    Mahy, L.; Hutsemékers, D.; Nazé, Y.; Royer, P.; Lebouteiller, V.; Waelkens, C.

    2017-03-01

    Aims: The magnetic star HD 148937 is the only Galactic Of?p star surrounded by a nebula. The structure of this nebula is particularly complex and is composed, from the center out outwards, of a close bipolar ejecta nebula (NGC 6164/5), an ellipsoidal wind-blown shell, and a spherically symmetric Strömgren sphere. The exact formation process of this nebula and its precise relation to the star's evolution remain unknown. Methods: We analyzed infrared Spitzer IRS and far-infrared Herschel/PACS observations of the NGC 6164/5 nebula. The Herschel imaging allowed us to constrain the global morphology of the nebula. We also combined the infrared spectra with optical spectra of the central star to constrain its evolutionary status. We used these data to derive the abundances in the ejected material. To relate this information to the evolutionary status of the star, we also determined the fundamental parameters of HD 148937 using the CMFGEN atmosphere code. Results: The Hα image displays a bipolar or "8"-shaped ionized nebula, whilst the infrared images show dust to be more concentrated around the central object. We determine nebular abundance ratios of N/O = 1.06 close to the star, and N/O = 1.54 in the bright lobe constituting NGC 6164. Interestingly, the parts of the nebula located further from HD 148937 appear more enriched in stellar material than the part located closer to the star. Evolutionary tracks suggest that these ejecta have occured 1.2-1.3 and 0.6 Myr ago, respectively. In addition, we derive abundances of argon for the nebula compatible with the solar values and we find a depletion of neon and sulfur. The combined analyses of the known kinematics and of the new abundances of the nebula suggest either a helical morphology for the nebula, possibly linked to the magnetic geometry, or the occurrence of a binary merger. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important

  4. ALMA Observations of the Molecular Gas in the Debris Disk of the 30 Myr Old Star HD 21997

    NASA Technical Reports Server (NTRS)

    Kospal, A.; Moor, A.; Juhasz, A.; Abraham, P.; Apai, D.; Csengeri, T.; Grady, C. A.; Henning, Th.; Hughes, A. M.; Kiss, Cs.; Pascucci, I.; Schmalzl, M.

    2013-01-01

    The 30 Myr old A3-type star HD 21997 is one of the two known debris dust disks having a measurable amount of cold molecular gas. With the goal of understanding the physical state, origin, and evolution of the gas in young debris disks, we obtained CO line observations with the Atacama Large Millimeter/submillimeter Array (ALMA). Here, we report on the detection of (12)CO and (13)CO in the J = 2-1 and J = 3-2 transitions and C(18)O in the J = 2-1 line. The gas exhibits a Keplerian velocity curve, one of the few direct measurements of Keplerian rotation in young debris disks. The measured CO brightness distribution could be reproduced by a simple star+disk system, whose parameters are r(sub in) < 26 AU, r(sub out) = 138 +/- 20 AU, Stellar M = 1.8 +0.5/-0.2 Solar M, and i = 32. Deg. 6 +/- 3 deg..1. The total CO mass, as calculated from the optically thin C(18)O line, is about (4-8) ×10(exp -2 ) Solar M, while the CO line ratios suggest a radiation temperature on the order of 6-9 K. Comparing our results with those obtained for the dust component of the HD 21997 disk from ALMA continuum observations by Moor et al., we conclude that comparable amounts of CO gas and dust are present in the disk. Interestingly, the gas and dust in the HD 21997 system are not colocated, indicating a dust-free inner gas disk within 55 AU of the star. We explore two possible scenarios for the origin of the gas. A secondary origin, which involves gas production from colliding or active planetesimals, would require unreasonably high gas production rates and would not explain why the gas and dust are not colocated. We propose that HD 21997 is a hybrid system where secondary debris dust and primordial gas coexist. HD 21997, whose age exceeds both the model predictions for disk clearing and the ages of the oldest T Tauri-like or transitional gas disks in the literature, may be a key object linking the primordial and the debris phases of disk evolution.

  5. ALMA OBSERVATIONS OF THE MOLECULAR GAS IN THE DEBRIS DISK OF THE 30 Myr OLD STAR HD 21997

    SciTech Connect

    Kóspál, Á.; Moór, A.; Ábrahám, P.; Kiss, Cs.; Juhász, A.; Schmalzl, M.; Apai, D.; Csengeri, T.; Grady, C. A.; Henning, Th.; Hughes, A. M.; Pascucci, I.

    2013-10-20

    The 30 Myr old A3-type star HD 21997 is one of the two known debris dust disks having a measurable amount of cold molecular gas. With the goal of understanding the physical state, origin, and evolution of the gas in young debris disks, we obtained CO line observations with the Atacama Large Millimeter/submillimeter Array (ALMA). Here, we report on the detection of {sup 12}CO and {sup 13}CO in the J = 2-1 and J = 3-2 transitions and C{sup 18}O in the J = 2-1 line. The gas exhibits a Keplerian velocity curve, one of the few direct measurements of Keplerian rotation in young debris disks. The measured CO brightness distribution could be reproduced by a simple star+disk system, whose parameters are r{sub in} < 26 AU, r{sub out} = 138 ± 20 AU, M{sub *}=1.8{sup +0.5}{sub -0.2} M{sub ☉}, and i = 32.°6 ± 3.°1. The total CO mass, as calculated from the optically thin C{sup 18}O line, is about (4-8) × 10{sup –2} M{sub ⊕}, while the CO line ratios suggest a radiation temperature on the order of 6-9 K. Comparing our results with those obtained for the dust component of the HD 21997 disk from ALMA continuum observations by Moór et al., we conclude that comparable amounts of CO gas and dust are present in the disk. Interestingly, the gas and dust in the HD 21997 system are not colocated, indicating a dust-free inner gas disk within 55 AU of the star. We explore two possible scenarios for the origin of the gas. A secondary origin, which involves gas production from colliding or active planetesimals, would require unreasonably high gas production rates and would not explain why the gas and dust are not colocated. We propose that HD 21997 is a hybrid system where secondary debris dust and primordial gas coexist. HD 21997, whose age exceeds both the model predictions for disk clearing and the ages of the oldest T Tauri-like or transitional gas disks in the literature, may be a key object linking the primordial and the debris phases of disk evolution.

  6. DETECTION OF ELEMENTS AT ALL THREE r-PROCESS PEAKS IN THE METAL-POOR STAR HD 160617

    SciTech Connect

    Roederer, Ian U.; Lawler, James E. E-mail: jelawler@wisc.edu

    2012-05-01

    We report the first detection of elements at all three r-process peaks in the metal-poor halo star HD 160617. These elements include arsenic and selenium, which have not been detected previously in halo stars, and the elements tellurium, osmium, iridium, and platinum, which have been detected previously. Absorption lines of these elements are found in archive observations made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. We present up-to-date absolute atomic transition probabilities and complete line component patterns for these elements. Additional archival spectra of this star from several ground-based instruments allow us to derive abundances or upper limits of 45 elements in HD 160617, including 27 elements produced by neutron-capture reactions. The average abundances of the elements at the three r-process peaks are similar to the predicted solar system r-process residuals when scaled to the abundances in the rare earth element domain. This result for arsenic and selenium may be surprising in light of predictions that the production of the lightest r-process elements generally should be decoupled from the heavier r-process elements.

  7. Quantitative spectral analysis of the sdB star HD 188112: A helium-core white dwarf progenitor

    NASA Astrophysics Data System (ADS)

    Latour, M.; Heber, U.; Irrgang, A.; Schaffenroth, V.; Geier, S.; Hillebrandt, W.; Röpke, F. K.; Taubenberger, S.; Kromer, M.; Fink, M.

    2016-01-01

    Context. HD 188112 is a bright (V = 10.2 mag) hot subdwarf B (sdB) star with a mass too low to ignite core helium burning and is therefore considered a pre-extremely low-mass (ELM) white dwarf (WD). ELM WDs (M ≲ 0.3 M⊙) are He-core objects produced by the evolution of compact binary systems. Aims: We present in this paper a detailed abundance analysis of HD 188112 based on high-resolution Hubble Space Telescope (HST) near- and far-ultraviolet spectroscopy. We also constrain the mass of the star's companion. Methods: We use hybrid non-LTE model atmospheres to fit the observed spectral lines, and to derive the abundances of more than a dozen elements and the rotational broadening of metallic lines. Results: We confirm the previous binary system parameters by combining radial velocities measured in our UV spectra with the previously published values. The system has a period of 0.60658584 days and a WD companion with M ≥ 0.70 M⊙. By assuming a tidally locked rotation combined with the projected rotational velocity (v sin i = 7.9 ± 0.3 km s-1), we constrain the companion mass to be between 0.9 and 1.3 M⊙. We further discuss the future evolution of the system as a potential progenitor of an underluminous type Ia supernova. We measure abundances for Mg, Al, Si, P, S, Ca, Ti, Cr, Mn, Fe, Ni, and Zn, and for the trans-iron elements Ga, Sn, and Pb. In addition, we derive upper limits for the C, N, O elements and find HD 188112 to be strongly depleted in carbon. We find evidence of non-LTE effects on the line strength of some ionic species such as Si ii and Ni ii. The metallic abundances indicate that the star is metal-poor, with an abundance pattern most likely produced by diffusion effects.

  8. An extreme planetary system around HD 219828. One long-period super Jupiter to a hot-Neptune host star

    NASA Astrophysics Data System (ADS)

    Santos, N. C.; Santerne, A.; Faria, J. P.; Rey, J.; Correia, A. C. M.; Laskar, J.; Udry, S.; Adibekyan, V.; Bouchy, F.; Delgado-Mena, E.; Melo, C.; Dumusque, X.; Hébrard, G.; Lovis, C.; Mayor, M.; Montalto, M.; Mortier, A.; Pepe, F.; Figueira, P.; Sahlmann, J.; Ségransan, D.; Sousa, S. G.

    2016-07-01

    Context. With about 2000 extrasolar planets confirmed, the results show that planetary systems have a whole range of unexpected properties. This wide diversity provides fundamental clues to the processes of planet formation and evolution. Aims: We present a full investigation of the HD 219828 system, a bright metal-rich star for which a hot Neptune has previously been detected. Methods: We used a set of HARPS, SOPHIE, and ELODIE radial velocities to search for the existence of orbiting companions to HD 219828. The spectra were used to characterise the star and its chemical abundances, as well as to check for spurious, activity induced signals. A dynamical analysis is also performed to study the stability of the system and to constrain the orbital parameters and planet masses. Results: We announce the discovery of a long period (P = 13.1 yr) massive (m sini = 15.1 MJup) companion (HD 219828 c) in a very eccentric orbit (e = 0.81). The same data confirms the existence of a hot Neptune, HD 219828 b, with a minimum mass of 21 M⊕ and a period of 3.83 days. The dynamical analysis shows that the system is stable, and that the equilibrium eccentricity of planet b is close to zero. Conclusions: The HD 219828 system is extreme and unique in several aspects. First, ammong all known exoplanet systems it presents an unusually high mass ratio. We also show that systems like HD 219828, with a hot Neptune and a long-period massive companion are more frequent than similar systems with a hot Jupiter instead. This suggests that the formation of hot Neptunes follows a different path than the formation of their hot jovian counterparts. The high mass, long period, and eccentricity of HD 219828 c also make it a good target for Gaia astrometry as well as a potential target for atmospheric characterisation, using direct imaging or high-resolution spectroscopy. Astrometric observations will allow us to derive its real mass and orbital configuration. If a transit of HD 219828 b is detected

  9. Pulsations in the late-type Be star HD 50 209 detected by CoRoT

    NASA Astrophysics Data System (ADS)

    Diago, P. D.; Gutiérrez-Soto, J.; Auvergne, M.; Fabregat, J.; Hubert, A.-M.; Floquet, M.; Frémat, Y.; Garrido, R.; Andrade, L.; de Batz, B.; Emilio, M.; Espinosa Lara, F.; Huat, A.-L.; Janot-Pacheco, E.; Leroy, B.; Martayan, C.; Neiner, C.; Semaan, T.; Suso, J.; Catala, C.; Poretti, E.; Rainer, M.; Uytterhoeven, K.; Michel, E.; Samadi, R.

    2009-10-01

    Context: The presence of pulsations in late-type Be stars is still a matter of controversy. It constitutes an important issue to establish the relationship between non-radial pulsations and the mass-loss mechanism in Be stars. Aims: To contribute to this discussion, we analyse the photometric time series of the B8IVe star HD 50 209 observed by the CoRoT mission in the seismology field. Methods: We use standard Fourier techniques and linear and non-linear least squares fitting methods to analyse the CoRoT light curve. In addition, we applied detailed modelling of high-resolution spectra to obtain the fundamental physical parameters of the star. Results: We have found four frequencies which correspond to gravity modes with azimuthal order m=0,-1,-2,-3 with the same pulsational frequency in the co-rotating frame. We also found a rotational period with a frequency of 0.679 cd-1 (7.754 μHz). Conclusions: HD 50 209 is a pulsating Be star as expected from its position in the HR diagram, close to the SPB instability strip. Based on observations made with the CoRoT satellite, with FEROS at the 2.2 m telescope of the La Silla Observatory under the ESO Large Programme LP178.D-0361 and with Narval at the Télescope Bernard Lyot of the Pic du Midi Observatory. Current address: Valencian International University (VIU), José Pradas Gallen s/n, 12006 Castellón, Spain. Current address: Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot; CEA, IRFU, SAp, centre de Saclay, 91191 Gif-sur-Yvette, France.

  10. Evidence for a bipolar nebula around the peculiar B(e) star HD 45677 from ultraviolet spectropolarimetry

    NASA Technical Reports Server (NTRS)

    Schulte-Ladbeck, R. E.; Shepherd, D. S.; Nordsieck, K. H.; Code, A. D.; Anderson, C. M.; Babler, B. L.; Bjorkman, K. S.; Clayton, G. C.; Magalhaes, A. M.; Meade, M. R.

    1992-01-01

    We report the first ultraviolet spectropolarimetry of the peculiar B-type emission-line star with infrared excess HD 45677. The observations were obtained during the 1990 December Astro-l space shuttle mission with the Wisconsin Ultraviolet Photo-Polarimeter Experiment, and cover the spectral range 1400-3220 A. We also present the first optical spectropolarimetry, extending from the atmospheric cutoff to about 7600 A. The observed UV/optical linear polarization displays a strong increase toward shorter wavelengths indicative of scattering by circumstellar dust. The position angle of the intrinsic polarization flips by 90 deg in the near-UV as expected from a bipolar reflection nebula.

  11. A HOT URANUS ORBITING THE SUPER METAL-RICH STAR HD 77338 AND THE METALLICITY-MASS CONNECTION

    SciTech Connect

    Jenkins, J. S.; Hoyer, S.; Jones, M. I.; Rojo, P.; Day-Jones, A. C.; Ruiz, M. T.; Jones, H. R. A.; Tuomi, M.; Barnes, J. R.; Pavlenko, Y. V.; Pinfield, D. J.; Murgas, F.; Ivanyuk, O.; Jordan, A.

    2013-04-01

    We announce the discovery of a low-mass planet orbiting the super metal-rich K0V star HD 77338 as part of our ongoing Calan-Hertfordshire Extrasolar Planet Search. The best-fit planet solution has an orbital period of 5.7361 {+-} 0.0015 days and with a radial velocity semi-amplitude of only 5.96 {+-} 1.74 ms{sup -1}, we find a minimum mass of 15.9{sup +4.7}{sub -5.3} M{sub Circled-Plus }. The best-fit eccentricity from this solution is 0.09{sup +0.25}{sub -0.09}, and we find agreement for this data set using a Bayesian analysis and a periodogram analysis. We measure a metallicity for the star of +0.35 {+-} 0.06 dex, whereas another recent work finds +0.47 {+-} 0.05 dex. Thus HD 77338b is one of the most metal-rich planet-host stars known and the most metal-rich star hosting a sub-Neptune-mass planet. We searched for a transit signature of HD 77338b but none was detected. We also highlight an emerging trend where metallicity and mass seem to correlate at very low masses, a discovery that would be in agreement with the core accretion model of planet formation. The trend appears to show that for Neptune-mass planets and below, higher masses are preferred when the host star is more metal-rich. Also a lower boundary is apparent in the super metal-rich regime where there are no very low mass planets yet discovered in comparison to the sub-solar metallicity regime. A Monte Carlo analysis shows that this low-mass planet desert is statistically significant with the current sample of 36 planets at the {approx}4.5{sigma} level. In addition, results from Kepler strengthen the claim for this paucity of the lowest-mass planets in super metal-rich systems. Finally, this discovery adds to the growing population of low-mass planets around low-mass and metal-rich stars and shows that very low mass planets can now be discovered with a relatively small number of data points using stable instrumentation.

  12. A Hot Uranus Orbiting the Super Metal-rich Star HD 77338 and the Metallicity-Mass Connection

    NASA Astrophysics Data System (ADS)

    Jenkins, J. S.; Jones, H. R. A.; Tuomi, M.; Murgas, F.; Hoyer, S.; Jones, M. I.; Barnes, J. R.; Pavlenko, Y. V.; Ivanyuk, O.; Rojo, P.; Jordán, A.; Day-Jones, A. C.; Ruiz, M. T.; Pinfield, D. J.

    2013-04-01

    We announce the discovery of a low-mass planet orbiting the super metal-rich K0V star HD 77338 as part of our ongoing Calan-Hertfordshire Extrasolar Planet Search. The best-fit planet solution has an orbital period of 5.7361 ± 0.0015 days and with a radial velocity semi-amplitude of only 5.96 ± 1.74 ms-1, we find a minimum mass of 15.9^{+4.7}_{-5.3} M ⊕. The best-fit eccentricity from this solution is 0.09^{+0.25}_{-0.09}, and we find agreement for this data set using a Bayesian analysis and a periodogram analysis. We measure a metallicity for the star of +0.35 ± 0.06 dex, whereas another recent work finds +0.47 ± 0.05 dex. Thus HD 77338b is one of the most metal-rich planet-host stars known and the most metal-rich star hosting a sub-Neptune-mass planet. We searched for a transit signature of HD 77338b but none was detected. We also highlight an emerging trend where metallicity and mass seem to correlate at very low masses, a discovery that would be in agreement with the core accretion model of planet formation. The trend appears to show that for Neptune-mass planets and below, higher masses are preferred when the host star is more metal-rich. Also a lower boundary is apparent in the super metal-rich regime where there are no very low mass planets yet discovered in comparison to the sub-solar metallicity regime. A Monte Carlo analysis shows that this low-mass planet desert is statistically significant with the current sample of 36 planets at the ~4.5σ level. In addition, results from Kepler strengthen the claim for this paucity of the lowest-mass planets in super metal-rich systems. Finally, this discovery adds to the growing population of low-mass planets around low-mass and metal-rich stars and shows that very low mass planets can now be discovered with a relatively small number of data points using stable instrumentation. Based on observations collected at the La Silla Paranal Observatory, ESO (Chile) with the HARPS spectrograph on the ESO 3.6 m telescope

  13. Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon. III. HD 50138

    NASA Astrophysics Data System (ADS)

    Jeřábková, T.; Korčáková, D.; Miroshnichenko, A.; Danford, S.; Zharikov, S. V.; Kříček, R.; Zasche, P.; Votruba, V.; Šlechta, M.; Škoda, P.; Janík, J.

    2016-02-01

    Context. B[e] stars are anomalous objects around which extended circumstellar matter is present. The observed properties of the central star are significantly affected by the surrounding material. Therefore, the use of standard synthetic spectra is disputable in this case and our capability to study these objects is limited. One of the possibilities is to analyse variations of the spectral features. Long-term spectroscopic observations are required for this, but are not found in the literature. For our study we choose the B[e] star HD 50138 of the FS CMa type because of the indication that this star is a post-main-sequence star, although still not highly evolved. Therefore, it can be a good object for testing evolutionary models. Currently, HD 50138 is the most extensively observed FS CMa star which makes it an ideal object for modelling. Our observations fill the gap in the available data. Aims: To describe the variability of HD 50138 we have monitored this star spectroscopically over the last twenty years. To search for the periodicity on short-term scales, series of night-to-night observations were also obtained. We were able to obtain 130 spectra from four different telescopes - 1.06 m at Ritter Observatory (échelle, R ~ 26 000, 32 spectra, 1994-2003), the Perek 2 m telescope at Ondřejov Observatory (slit, R ~ 12 500, 56 spectra, 2004-2013), the 2.12 m telescope at Observatorio Astronomico Nacional San Pedro Martir (échelle, R ~ 18 000, 16 spectra, 2005-2013), and the 0.81 m telescope at Three College Observatory (échelle, R ~ 12 000, 26 spectra, 2013-2014). Methods: We describe and analyse variations of the chosen lines. The measurements of the equivalent widths and radial velocities of the Hα, Hβ, and [O i] λλ 6300, 6364 Å lines are presented. The set of obtained spectra allows us to describe the changes on timescales from days to years. Results: The long-term quasi-periodic trend was found in the variations of the Hα equivalent width and confirmed

  14. Discovery of multiple pulsations in the new δ Scuti star HD 92277: Asteroseismology from Dome A, Antarctica

    SciTech Connect

    Zong, Weikai; Fu, Jian-Ning; Niu, Jia-Shu; Zhu, Zonghong; Charpinet, S.; Vauclair, G.; Ashley, Michael C. B.; Lawrence, Jon S.; Luong-Van, Daniel; Cui, Xiangqun; Gong, Xuefei; Feng, Longlong; Wang, Lifan; Yuan, Xiangyan; Zhu, Zhenxi; Liu, Qiang; Wang, Lingzhi; Zhou, Xu; Pennypacker, Carl R.; York, Donald G.

    2015-02-01

    We report the discovery of low-amplitude oscillations in the star HD 92277 from long, continuous observations in the r and g bands using the CSTAR telescopes in Antarctica. A total of more than 1950 hours of high-quality light curves were used to categorize HD 92277 as a new member of the δ Scuti class. We have detected 21 (20 frequencies are independent and one is the linear combination) and 14 (13 frequencies are independent and one is the linear combination) pulsation frequencies in the r and g bands, respectively, indicating a multi-periodic pulsation behavior. The primary frequency f{sub 1} = 10.810 days{sup −1} corresponds to a period of 0.0925 days and is an l = 1 mode. We estimate a B − V index of 0.39 and derive an effective temperature of 6800 K for HD 92277. We conclude that long, continuous and uninterrupted time-series photometry can be performed from Dome A, Antarctica, and that this is especially valuable for asteroseismology where multi-color observations (often not available from space-based telescopes) assist with mode identification.

  15. DISCOVERY OF A TWO-ARMED SPIRAL STRUCTURE IN THE GAPPED DISK AROUND HERBIG Ae STAR HD 100453

    SciTech Connect

    Wagner, Kevin; Apai, Daniel; Robberto, Massimo

    2015-11-01

    We present Very Large Telescope (VLT)/SPHERE adaptive optics imaging in the Y-, J-, H-, and K-bands of the HD 100453 system and the discovery of a two-armed spiral structure in a disk extending to 0.″37 (∼42 AU) from the star, with highly symmetric arms to the northeast and southwest. Inside of the spiral arms, we resolve a ring of emission from 0.″18 to 0.″25 (∼21–29 AU). By assuming that the ring is intrinsically circular we estimate an inclination of ∼34° from face on. We detect dark crescents on opposite sides (NW and SE) that begin at 0.″18 and continue to radii smaller than our inner working angle of 0.″15, which we interpret as the signature of a gap at ≲21 AU that has likely been cleared by forming planets. We also detect the ∼120 AU companion HD 100453 B, and by comparing our data to 2003 Hubble Space Telescope and VLT/NACO images we estimate an orbital period of ∼850 year. We discuss what implications the discovery of the spiral arms and finer structures of the disk may have on our understanding of the possible planetary system in HD 100453 and how the morphology of this disk compares to other related objects.

  16. The Lick-Carnegie Exoplanet Survey: HD 32963—A New Jupiter Analog Orbiting a Sun-like Star

    NASA Astrophysics Data System (ADS)

    Rowan, Dominick; Meschiari, Stefano; Laughlin, Gregory; Vogt, Steven S.; Butler, R. Paul; Burt, Jennifer; Wang, Songhu; Holden, Brad; Hanson, Russell; Arriagada, Pamela; Keiser, Sandy; Teske, Johanna; Diaz, Matias

    2016-02-01

    We present a set of 109 new, high-precision Keck/HIRES radial velocity (RV) observations for the solar-type star HD 32963. Our data set reveals a candidate planetary signal with a period of 6.49 ± 0.07 years and a corresponding minimum mass of 0.7 ± 0.03 Jupiter masses. Given Jupiter's crucial role in shaping the evolution of the early Solar System, we emphasize the importance of long-term RV surveys. Finally, using our complete set of Keck radial velocities and correcting for the relative detectability of synthetic planetary candidates orbiting each of the 1122 stars in our sample, we estimate the frequency of Jupiter analogs across our survey at approximately 3%.

  17. High azimuthal number pulsation modes in fast rotating δ Scuti stars: the case of HD 101158 = V837 Cen.

    NASA Astrophysics Data System (ADS)

    Mantegazza, L.

    1997-07-01

    The frequency analysis of the line profile variations of the fast rotating (vsini=132km/s) δ Scuti star HD 101158, observed for three consecutive nights, shows the presence of two high azimuthal number non radial pulsation modes. The star is probably seen almost equator-on and both modes (ν_i_=12.9c/d and ν_2_=18.5 c/d) are prograde with m=-10 and m=-14 or -15 respectively; their frequencies are different with respect to the three frequencies identified in photometric data (Poretti 1991), which probably owe due to low l modes. Indications of the presence of these photometric modes have been found from the frequency analysis of the first two line moments. The line profile variations also show the possible presence of further modes with frequencies of 16.2, 20.3 and 21.1c/d and small amplitudes.

  18. Pulsational frequencies in the delta Scuti stars V624 Tauri and HD 23194. Results of the STEPHI X campaign on the Pleiades cluster

    NASA Astrophysics Data System (ADS)

    Fox-Machado, L.; Álvarez, M.; Michel, E.; Li, Z. P.; Pérez Hernández, F.; Chevreton, M.; Barban, C.; Belmonte, J. A.; Dolez, N.; Fernandez, A.; Guo, J. P.; Haywood, M.; Liu, Y. Y.; Pau, S.; Planas, H.; Servan, B.

    2002-02-01

    The results of the tenth multi-site campaign of the STEPHI network are reported. The delta Scuti stars V624 Tau (HD 23156) and HD 23194, belonging to the Pleiades cluster, were observed photometrically for 34 days on three continents during 1999 November-December. An overall run of 343 hours of data was collected. Seven frequencies for V624 Tau and two frequencies for HD 23194 have been found above a 99% confidence level. These results greatly improve those found in previous studies with much less data. A preliminary comparison of observed and theoretical frequencies suggests that both stars may oscillate with radial and non-radial p modes of radial orders typical among delta Scuti stars.

  19. A LIKELY CLOSE-IN LOW-MASS STELLAR COMPANION TO THE TRANSITIONAL DISK STAR HD 142527

    SciTech Connect

    Biller, Beth; Benisty, Myriam; Chauvin, Gael; Olofsson, Johan; Pott, Joerg-Uwe; Mueller, Andre; Bonnefoy, Mickaeel; Henning, Thomas; Lacour, Sylvestre; Thebault, Philippe; Sicilia-Aguilar, Aurora; Tuthill, Peter; Crida, Aurelien

    2012-07-10

    With the uniquely high contrast within 0.''1 ({Delta}mag(L') = 5-6.5 mag) available using Sparse Aperture Masking with NACO at Very Large Telescope, we detected asymmetry in the flux from the Herbig Fe star HD 142527 with a barycenter emission situated at a projected separation of 88 {+-} 5 mas (12.8 {+-} 1.5 AU at 145 pc) and flux ratios in H, K, and L' of 0.016 {+-} 0.007, 0.012 {+-} 0.008, and 0.0086 {+-} 0.0011, respectively (3{sigma} errors), relative to the primary star and disk. After extensive closure-phase modeling, we interpret this detection as a close-in, low-mass stellar companion with an estimated mass of {approx}0.1-0.4 M{sub Sun }. HD 142527 has a complex disk structure, with an inner gap imaged in both the near and mid-IR as well as a spiral feature in the outer disk in the near-IR. This newly detected low-mass stellar companion may provide a critical explanation of the observed disk structure.

  20. Stellar Parameters for HD 69830, a Nearby Star with Three Neptune Mass Planets and an Asteroid Belt

    NASA Astrophysics Data System (ADS)

    Tanner, Angelle; Boyajian, Tabetha S.; von Braun, Kaspar; Kane, Stephen; Brewer, John M.; Farrington, Chris; van Belle, Gerard T.; Beichman, Charles A.; Fischer, Debra; ten Brummelaar, Theo A.; McAlister, Harold A.; Schaefer, Gail

    2015-02-01

    We used the CHARA Array to directly measure the angular diameter of HD 69830, home to three Neptune mass planets and an asteroid belt. Our measurement of 0.674 ± 0.014 mas for the limb-darkened angular diameter of this star leads to a physical radius of R * = 0.9058 ± 0.0190 R ⊙ and luminosity of L * = 0.622 ± 0.014 L ⊙ when combined with a fit to the spectral energy distribution of the star. Placing these observed values on an Hertzsprung-Russel diagram along with stellar evolution isochrones produces an age of 10.6 ± 4 Gyr and mass of 0.863 ± 0.043 M ⊙. We use archival optical echelle spectra of HD 69830 along with an iterative spectral fitting technique to measure the iron abundance ([Fe/H] = -0.04 ± 0.03), effective temperature (5385 ± 44 K), and surface gravity (log g = 4.49 ± 0.06). We use these new values for the temperature and luminosity to calculate a more precise age of 7.5 ± 3 Gyr. Applying the values of stellar luminosity and radius to recent models on the optimistic location of the habitable zone produces a range of 0.61-1.44 AU partially outside the orbit of the furthest known planet (d) around HD 69830. Finally, we estimate the snow line at a distance of 1.95 ± 0.19 AU, which is outside the orbit of all three planets and its asteroid belt.

  1. Precise radial velocities of giant stars. IX. HD 59686 Ab: a massive circumstellar planet orbiting a giant star in a 13.6 au eccentric binary system

    NASA Astrophysics Data System (ADS)

    Ortiz, Mauricio; Reffert, Sabine; Trifonov, Trifon; Quirrenbach, Andreas; Mitchell, David S.; Nowak, Grzegorz; Buenzli, Esther; Zimmerman, Neil; Bonnefoy, Mickaël; Skemer, Andy; Defrère, Denis; Lee, Man Hoi; Fischer, Debra A.; Hinz, Philip M.

    2016-10-01

    Context. For over 12 yr, we have carried out a precise radial velocity (RV) survey of a sample of 373 G- and K-giant stars using the Hamilton Échelle Spectrograph at the Lick Observatory. There are, among others, a number of multiple planetary systems in our sample as well as several planetary candidates in stellar binaries. Aims: We aim at detecting and characterizing substellar and stellar companions to the giant star HD 59686 A (HR 2877, HIP 36616). Methods: We obtained high-precision RV measurements of the star HD 59686 A. By fitting a Keplerian model to the periodic changes in the RVs, we can assess the nature of companions in the system. To distinguish between RV variations that are due to non-radial pulsation or stellar spots, we used infrared RVs taken with the CRIRES spectrograph at the Very Large Telescope. Additionally, to characterize the system in more detail, we obtained high-resolution images with LMIRCam at the Large Binocular Telescope. Results: We report the probable discovery of a giant planet with a mass of mp sin i = 6.92-0.24+0.18 MJup orbiting at ap = 1.0860-0.0007+0.0006 au from the giant star HD 59686 A. In addition to the planetary signal, we discovered an eccentric (eB = 0.729-0.003+0.004) binary companion with a mass of mB sin i = 0.5296-0.0008+0.0011 M⊙ orbiting at a close separation from the giant primary with a semi-major axis of aB = 13.56-0.14+0.18 au. Conclusions: The existence of the planet HD 59686 Ab in a tight eccentric binary system severely challenges standard giant planet formation theories and requires substantial improvements to such theories in tight binaries. Otherwise, alternative planet formation scenarios such as second-generation planets or dynamical interactions in an early phase of the system's lifetime need to be seriously considered to better understand the origin of this enigmatic planet. Based on observations collected at the Lick Observatory, University of California.Based on observations collected at the

  2. KEPLER-21b: A 1.6 R{sub Earth} PLANET TRANSITING THE BRIGHT OSCILLATING F SUBGIANT STAR HD 179070

    SciTech Connect

    Howell, Steve B.; Rowe, Jason F.; Bryson, Stephen T.; Quinn, Samuel N.; Marcy, Geoffrey W.; Isaacson, Howard; Ciardi, David R.; Metcalfe, Travis S.; Monteiro, Mario J. P. F. G.; Appourchaux, Thierry; Basu, Sarbani; Creevey, Orlagh L.; Gilliland, Ronald L.; Quirion, Pierre-Olivier; Stello, Denis; Kjeldsen, Hans; Christensen-Dalsgaard, Joergen; Garcia, Rafael A. [Laboratoire AIM, CEA and others

    2012-02-20

    We present Kepler observations of the bright (V = 8.3), oscillating star HD 179070. The observations show transit-like events which reveal that the star is orbited every 2.8 days by a small, 1.6 R{sub Earth} object. Seismic studies of HD 179070 using short cadence Kepler observations show that HD 179070 has a frequency-power spectrum consistent with solar-like oscillations that are acoustic p-modes. Asteroseismic analysis provides robust values for the mass and radius of HD 179070, 1.34 {+-} 0.06 M{sub Sun} and 1.86 {+-} 0.04 R{sub Sun }, respectively, as well as yielding an age of 2.84 {+-} 0.34 Gyr for this F5 subgiant. Together with ground-based follow-up observations, analysis of the Kepler light curves and image data, and blend scenario models, we conservatively show at the >99.7% confidence level (3{sigma}) that the transit event is caused by a 1.64 {+-} 0.04 R{sub Earth} exoplanet in a 2.785755 {+-} 0.000032 day orbit. The exoplanet is only 0.04 AU away from the star and our spectroscopic observations provide an upper limit to its mass of {approx}10 M{sub Earth} (2{sigma}). HD 179070 is the brightest exoplanet host star yet discovered by Kepler.

  3. Conditions for HD cooling in the first galaxies revisited: interplay between far-ultraviolet and cosmic ray feedback in Population III star formation

    NASA Astrophysics Data System (ADS)

    Nakauchi, Daisuke; Inayoshi, Kohei; Omukai, Kazuyuki

    2014-08-01

    HD dominates the cooing of primordial clouds with enhanced ionization, e.g. shock-heated clouds in structure formation or supernova remnants, relic H II regions of Pop III stars and clouds with cosmic ray (CR) irradiation. There, the temperature decreases to several 10 K and the characteristic stellar mass decreases to ˜10 M⊙, in contrast with first stars formed from undisturbed pristine clouds (˜100 M⊙). However, without CR irradiation, even weak far-ultraviolet (FUV) irradiation suppresses HD formation/cooling. Here, we examine conditions for HD cooling in primordial clouds including both FUV and CR feedback. At the beginning of collapse, the shock-compressed gas cools with its density increasing, while the relic H II region gas cools at a constant density. Moreover, shocks tend to occur in denser environments than H II regions. Owing to the higher column density and the more effective shielding, the critical FUV intensity for HD cooling in a shock-compressed gas becomes ˜10 times higher than that in relic H II regions. Consequently, in the shock-compressed gas, the critical FUV intensity exceeds the background level for most of the redshift we consider (6 ≲ z ≲ 15), while in relic H II regions, HD cooling becomes effective after the CR intensity increases enough at z ≲ 10. Our result suggests that less massive (˜10 M⊙) Pop III stars may be more common than previously considered and could be the dominant population of Pop III stars.

  4. Molecular emission bands in the ultraviolet spectrum of the red rectangle star HD 44179

    NASA Technical Reports Server (NTRS)

    Sitko, M. L.

    1981-01-01

    New observations of the ultraviolet spectrum of HD 44179 are reported. Absorption due to the CO molecule is present in the spectrum with NCO approximately 10 to the 18th power per sq cm. Emission due to either CO or a molecule containing C=C, C=N, C-C, and C-H bonds (or both) is also present.

  5. B fields in OB stars (BOB): The magnetic triple stellar system HD 164492C in the Trifid nebula

    NASA Astrophysics Data System (ADS)

    González, J. F.; Hubrig, S.; Przybilla, N.; Carroll, T.; Nieva, M.-F.; Ilyin, I.; Järvinen, S.; Morel, T.; Schöller, M.; Castro, N.; Barbá, R.; de Koter, A.; Schneider, F. R. N.; Kholtygin, A.; Butler, K.; Veramendi, M. E.; Langer, N.; BOB Collaboration

    2017-01-01

    HD 164492C is a spectroscopic triple stellar system that has been recently detected to possess a strong magnetic field. We have obtained high-resolution spectroscopic and spectropolarimetric observations over a timespan of two years and derived physical, chemical, and magnetic properties for this object. The system is formed by an eccentric close spectroscopic binary (Ca1-Ca2) with a period of 12.5 days, and a massive tertiary Cb. We calculated the orbital parameters of the close pair, reconstructed the spectra of the three components, and determined atmospheric parameters and chemical abundances by spectral synthesis. From spectropolarimetric observations, multi-epoch measurements of the longitudinal magnetic fields were obtained. The magnetic field is strongly variable on timescales of a few days, with a most probable period in the range of 1.4-1.6 days. Star Cb with Teff ˜ 25 000 K is the apparently fastest rotator and the most massive star of this triple system and has anomalous chemical abundances with a marked overabundance of helium, 0.35±0.04 by number. We identified this star as being responsible for the observed magnetic field, although the presence of magnetic fields in the components of the Ca pair cannot be excluded. Star Ca1 with a temperature of about 24 000 K presents a normal chemical pattern, while the least massive star Ca2 is a mid-B type star (Teff ˜ 15 000 K) with an overabundance of silicon. The obtained stellar parameters of the system components suggest a distance of 1.5 kpc and an age of 10-15 Myr.

  6. Documentation for the machine-readable version of the University of Michigan Catalogue of two-dimensional spectral types for the HD stars. Volume 2: Declinations minus 53 deg to minus 40 deg

    NASA Technical Reports Server (NTRS)

    Warren, W. H., Jr.

    1981-01-01

    The magnetic tape version of Volume 2 of the University of Michigan systematic reclassification program for the Henry Draper Catalogue (HD) stars is described. Volume 2 contains all HD stars in the declination range -53 degrees to 40 degrees and also exists in printed form.

  7. LOOKING FOR A CONNECTION BETWEEN THE Am PHENOMENON AND HYBRID {delta} Sct -{gamma} Dor PULSATION: DETERMINATION OF THE FUNDAMENTAL PARAMETERS AND ABUNDANCES OF HD 114839 AND BD +18 4914

    SciTech Connect

    Hareter, M.; Weiss, W.; Fossati, L.; Suarez, J. C.; Rainer, M.; Poretti, E.

    2011-12-20

    {delta} Sct-{gamma} Dor hybrids pulsate simultaneously in p- and g-modes, which carry information on the structure of the envelope as well as to the core. Hence, they are key objects for investigating A and F type stars with asteroseismic techniques. An important requirement for seismic modeling is small errors in temperature, gravity, and chemical composition. Furthermore, we want to investigate the existence of an abundance indicator typical for hybrids, something that is well established for the roAp stars. Previous to the present investigation, the abundance pattern of only one hybrid and another hybrid candidate has been published. We obtained high-resolution spectra of HD 114839 and BD +18 4914 using the SOPHIE spectrograph of the Observatoire de Haute-Provence and the HARPS spectrograph at ESO La Silla. For each star we determined fundamental parameters and photospheric abundances of 16 chemical elements by comparing synthetic spectra with the observations. We compare our results to that of seven {delta} Sct and nine {gamma} Dor stars. For the evolved BD +18 4914 we found an abundance pattern typical for an Am star, but could not confirm this peculiarity for the less evolved star HD 114839, which is classified in the literature as uncertain Am star. Our result supports the concept of evolved Am stars being unstable. With our investigation we nearly doubled the number of spectroscopically analyzed {delta} Sct-{gamma} Dor hybrid stars, but did not yet succeed in identifying a spectroscopic signature for this group of pulsating stars. A statistically significant spectroscopic investigation of {delta} Sct- {gamma} Dor hybrid stars is still missing, but would be rewarding considering the asteroseismological potential of this group.

  8. The RS CVn Binary HD 155555: A Comparative Study of the Atmospheres for the Two Component Stars

    NASA Technical Reports Server (NTRS)

    Airapetian, V. S.; Dempsey, R. C.

    1997-01-01

    We present GHRS/HST observations of the RS CVn binary system HD 155555. Several key UV emission lines (Fe XXI, Si IV, O V, C IV) have been analyzed to provide information about the heating rate throughout the atmosphere from the chromosphere to the corona. We show that both the G and K components reveal features of a chromosphere, transition region and corona. The emission measure distribution as a function of temperature for both components is derived and compared with the RS Cvn system, HR 1099, and the Sun. The transition region and coronal lines of both stars show nonthermal broadenings of approx. 20-30 km/s. Possible physical implications for coronal heating mechanisms are discussed.

  9. The field horizontal-branch star HD 109995: New results with coadded ultraviolet and optical region spectra

    NASA Technical Reports Server (NTRS)

    Adelman, S. J.; Leckrone, D. S.

    1985-01-01

    A comprehensive ultraviolet and optical region abundance analysis of the field horizontal branch Population 2 A-type star HD 109995 is described. Coaddition of IUE high dispersion images and DAO 6.5 A/mm IIaO spectrograms improved the signal-to-noise ratio of the data. We have identified ultraviolet lines whose analysis will provide more complete and accurate elemental abundances than those obtained from optical region spectra alone. A preliminary elemental abundance analysis of the optical region shows that log Z/Z (solar) approx. = -2. A first attempt to synthesize two Fe 2 ultraviolet resonance lines yields an iron abundance a few tenths of a deg higher than the average obtained from optical region Fe 2 lines.

  10. 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).

  11. REVEALING THE ASYMMETRY OF THE WIND OF THE VARIABLE WOLF-RAYET STAR WR1 (HD 4004) THROUGH SPECTROPOLARIZATION

    SciTech Connect

    St-Louis, N.

    2013-11-01

    In this paper, high quality spectropolarimetric observations of the Wolf-Rayet (WR) star WR1 (HD 4004) obtained with ESPaDOnS at the Canada-France-Hawaii Telescope are presented. All major emission lines present in the spectrum show depolarization in the relative Stokes parameters Q/I and U/I. From the behavior of the amount of line depolarization as a function of line strength, the intrinsic continuum light polarization of WR1 is estimated to be P/I = 0.443% ± 0.028% with an angle of θ = –26.°2. Although such a level of polarization could in principle be caused by a wind flattened by fast rotation, the scenario in which it is a consequence of the presence of corotating interaction regions (CIRs) in the wind is preferred. This is supported by previous photometric and spectroscopic observations showing periodic variations with a period of 16.9 days. This is now the third WR star thought to exhibit CIRs in its wind that is found to have line depolarization. Previous authors have found a strong correlation between line depolarization and the presence of an ejected nebula, which they interpret as a sign that the star has relatively recently reached the WR phase since the nebula are thought to dissipate very fast. In cases where the presence of CIRs in the wind is favored to explain the depolarization across spectral lines, the above-mentioned correlation may indicate that those massive stars have only very recently transited from the previous evolutionary phase to the WR phase.

  12. Chromospherically active stars. III - HD 26337 = EI Eri: An RS CVn candidate for the Doppler-imaging technique

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Quigley, Robert; Gillies, Kim; Africano, John L.

    1987-01-01

    Spectroscopic observations of the chromospherically active G5 IV single-lined binary HD 26337 = EI Eri are presented. An orbital period of 1.94722 days is found for the star. It has moderately strong Ca II H and K emission and strong ultraviolet emission features, while H-alpha is a weak absorption feature that is variable in strength. The inclination of the system is 46 + or - 12 deg, and the unseen secondary is probably a late K or early M dwarf. The v sin i of the primary is 50 + or - 3 km/s, resulting in a minimum radius of 1.9 + or - 0.1 solar radius. The star is within the required limits for Doppler imaging. The primary is close to filling its Roche lobe, resulting in a strong constraint that the mass ratio is 2.6 or greater, with a primary mass of at least 1.4 solar mass. The distance to the system is estimated at 75 pc.

  13. NIR spectroscopy of the HAeBe star HD 100546. III. Further evidence of an orbiting companion?

    SciTech Connect

    Brittain, Sean D.; Carr, John S.; Najita, Joan R.; Quanz, Sascha P.; Meyer, Michael R.

    2014-08-20

    We report high-resolution NIR spectroscopy of CO and OH emission from the Herbig Be star HD 100546. We discuss how our results bear striking resemblance to several theoretically predicted signposts of giant planet formation. The properties of the CO and OH emission lines are consistent with our earlier interpretation that these diagnostics provide indirect evidence for a companion that orbits the star close to the disk wall (at ∼13 AU). The asymmetry of the OH spectral line profiles and their lack of time variability are consistent with emission from gas in an eccentric orbit at the disk wall that is approximately stationary in the inertial frame. The time variable spectroastrometric properties of the CO v = 1-0 emission line point to an orbiting source of CO emission with an emitting area similar to that expected for a circumplanetary disk (∼0.1 AU{sup 2}) assuming the CO emission is optically thick. We also consider a counterhypothesis to this interpretation, namely that the variable CO emission arises from a bright spot on the disk wall. We conclude with a brief suggestion of further work that can distinguish between these scenarios.

  14. Spectroscopic study of the HgMn star HD 49606: the quest for binarity, abundance stratifications and magnetic field

    NASA Astrophysics Data System (ADS)

    Catanzaro, G.; Giarrusso, M.; Leone, F.; Munari, M.; Scalia, C.; Sparacello, E.; Scuderi, S.

    2016-08-01

    In this paper, we present a multi-instrument analysis of the mercury-manganese star HD 49606. New spectroscopic observations have been obtained by us with Catania Astrophysical Observatory Spectropolarimeter (CAOS@OAC) and High Accuracy Radial Velocity Planet Searcher-North@Telescopio Nazionale Galileo (HARPS-N@TNG). Combining these observations with archive data coming from other instruments, we performed a comprehensive analysis of this star. We highlight the motion around the centre of mass of a binary system of SB1 type, and we calculate the fundamental parameters characterizing its orbit. We also speculate on the nature of the unseen component. From the fit of H β and H γ, we determined the effective temperature and gravity, while from a number of metal lines, we derive the rotational and microturbulent velocities. Regarding chemical composition, we found underabundances of helium, oxygen, magnesium, sulfur and nickel, solar composition for carbon and overabundances for all the other elements. In particular, mercury abundance is derived taking into account an isotopic mixture different from the terrestrial one. As to magnesium, silicon and phosphorus, we found a non-constant abundance with the optical depth, a result currently considered an evidence of stratification. Spectropolarimetric observations have been performed in the attempt to highlight the presence of a magnetic field, but no detection has been found.

  15. VizieR Online Data Catalog: MK Classification for HD stars for 25-30{deg} zone (Jensen 1982)

    NASA Astrophysics Data System (ADS)

    Jensen, K. S.

    1993-08-01

    The catalog contains MK spectral classifications for 1003 HD stars in the zone +25-30{deg}, briefly presented at IAU Colloq. 47, held in Vatican City in July 1978 (1979RA......9..479C). Most stars classified in this region are earlier than G2. The notation is the same as in the earlier paper (1981A&AS...45..455J), with conventions similar to the Houk and Cowley survey (Cats. III/31 and III/51); a noticeable exception is that the luminosity class the most probable stands before the slash. On the average, the classifications present in the catalogue are means of 3 classifications. The internal rms error estimated by the author on a single classification is typically: {sigma}(SpT) = 0.65 (unit 1 subtype) {sigma}(Lum) = 0.40 (unit lum. class) No dependence on spectrum quality is found; however the quality 4 spectra are seldom classified without slashes (which introduces a sort of "internal scatter" into the type) External errors were estimated by a comparison with published work: - Walborn (1971ApJS...23..257W) and Guetter (1968PASP...80..197G) concern early-B stars; - Cowley et al. (1969AJ.....74..375C) and Osawa (1959ApJ...130..159O) concern late-B and A stars; - Harlan et al. (1969AJ.....74..916H, 1970AJ.....75..165H), Hill et al. (1976MmRAS..82...69H) and Heard (1956PDDO....2..105H) concern F stars; - Fehrenbach lists concern all type stars. The comparisons give the following external errors: ----------------------------------------------------- Source N D(SpT) +/- D(Lum) +/- ----------------------------------------------------- Walborn (1971) 5 -.40 +/- .45 -.10 +/- .32 Guetter (1968) 4 -.12 +/- .25 -.12 +/- .25 Cowley et al. 17 -.52 +/- .72 -.09 +/- .53 Osawa (1959) 18 -.22 +/- .77 -.22 +/- .77 Harlan et al. 20 +.20 +/- .69 +.03 +/- .56 Hill et al. 18 -.36 +/- .78 -.19 +/- .55 Heard (1956) 46 -.24 +/- .88 +.10 +/- .47 Fehrenbach et al. 46 +.48 +/-1.39 +.34 +/-1.06 ----------------------------------------------------- These figures should be compared with e

  16. Non-LTE analysis of subluminous O-star. V - The binary system HD 128220

    NASA Astrophysics Data System (ADS)

    Gruschinske, J.; Hamann, W. R.; Kudritzki, R. P.; Simon, K. P.; Kaufmann, J. P.

    1983-05-01

    Spectra of the binary system HD 128220 were taken in the UV and in the visual. The hot component - an O subdwarf - is analysed by means of non-LTE calculations. The cool companion has an effective temperature about 5500 ± 500K (Type G). The discussion of the stellar parameters arrives at results which agree with those derived from the mass function (Wallerstein and Wolff, 1966): if both components have about the same mass, these masses lie above 3 M_sun;. An O subdwarf of such a high mass has not yet been found and may be a supernova candidate. However, within the error margin of the orbital data also a mass ratio of MO/MG = 0.5 cannot be excluded, which would lead to stellar parameters which are more common for sdO's.

  17. Gas phase abundances and conditions along the sight line to the low-halo, inner galaxy star HD 167756

    NASA Technical Reports Server (NTRS)

    Cardelli, Jason A.; Sembach, Kenneth R.; Savage, Blair D.

    1995-01-01

    We present high-resolution (3.5 km/s) Goddard High Resolution Spectrograph (GHRS) measurements of the Mg II, Si II, Cr II, Fe II, and Zn II lines toward HD 167756, a low-latitude halo star at a distance of 4 kpc in the direction l = 351.5 deg, b = -12.3 and at a Galactic altitude of z = -0.85 kpc. Supplemental Na I, Ca II, and H I data are also presented for comparison with the UV lines. Our analysis centers on converting the observed absoprtion-line data into measures of the apparent column density per unit velocity. N(sub a)(v), over the velocity range -25 less than or = v(sub lsr) less than 30 km/s for each species observed. We use these N(sub a)(v) profiles to construct logarithmic abundance ratios of Mg II, Si II, Cr II, Fe II, and Ca II relative to Zn II, normalized to solar abundances, as a function of velocity. Compared to Zn, these species show an underabundance relative to their solar values, with the largest underabundances occurring in the v(sub lsr) approximately equals 5 km/s component(s), for which we find logarithmic abundances A(sub Si/Zn) greater than -0.38, A(Mg/Zn) = -0.82, A(sub Cr/Zn) = -1.18, and A(sub Fe/Zn) greater than 1.40 dex. We show that ionization effects, abundance gradients, or intrinsic abundance variability cannot be significant sources for the underabundances observed. The most likely explanation is gas phase depletion of elements onto dust grains. Comparisons with the gas phase abundances along other diffuse, warm gas sight lines, like the halo sight line to HD 93521, support this interpretation as do the derived physical properties of the sight line.

  18. Discovery of a low-mass companion inside the debris ring surrounding the F5V star HD 206893

    NASA Astrophysics Data System (ADS)

    Milli, J.; Hibon, P.; Christiaens, V.; Choquet, É.; Bonnefoy, M.; Kennedy, G. M.; Wyatt, M. C.; Absil, O.; Gómez González, C. A.; del Burgo, C.; Matrà, L.; Augereau, J.-C.; Boccaletti, A.; Delacroix, C.; Ertel, S.; Dent, W. R. F.; Forsberg, P.; Fusco, T.; Girard, J. H.; Habraken, S.; Huby, E.; Karlsson, M.; Lagrange, A.-M.; Mawet, D.; Mouillet, D.; Perrin, M.; Pinte, C.; Pueyo, L.; Reyes, C.; Soummer, R.; Surdej, J.; Tarricq, Y.; Wahhaj, Z.

    2017-01-01

    Aims: Uncovering the ingredients and the architecture of planetary systems is a very active field of research that has fuelled many new theories on giant planet formation, migration, composition, and interaction with the circumstellar environment. We aim at discovering and studying new such systems, to further expand our knowledge of how low-mass companions form and evolve. Methods: We obtained high-contrast H-band images of the circumstellar environment of the F5V star HD 206893, known to host a debris disc never detected in scattered light. These observations are part of the SPHERE High Angular Resolution Debris Disc Survey (SHARDDS) using the InfraRed Dual-band Imager and Spectrograph (IRDIS) installed on VLT/SPHERE. Results: We report the detection of a source with a contrast of 3.6 × 10-5 in the H-band, orbiting at a projected separation of 270 milliarcsec or 10 au, corresponding to a mass in the range 24 to 73 MJup for an age of the system in the range 0.2 to 2 Gyr. The detection was confirmed ten months later with VLT/NaCo, ruling out a background object with no proper motion. A faint extended emission compatible with the disc scattered light signal is also observed. Conclusions: The detection of a low-mass companion inside a massive debris disc makes this system an analog of other young planetary systems such as β Pictoris, HR 8799 or HD 95086 and requires now further characterisation of both components to understand their interactions.

  19. HD 164492C: a rapidly rotating, Hα-bright, magnetic early B star associated with a 12.5 d spectroscopic binary

    NASA Astrophysics Data System (ADS)

    Wade, G. A.; Shultz, M.; Sikora, J.; Bernier, M.-É.; Rivinius, Th.; Alecian, E.; Petit, V.; Grunhut, J. H.; BinaMIcS Collaboration

    2017-03-01

    We employ high-resolution spectroscopy and spectropolarimetry to derive the physical properties and magnetic characteristics of the multiple system HD 164492C, located in the young open cluster M20. The spectrum reveals evidence of three components: a broad-lined early B star (HD 164492C1), a narrow-lined early B star (HD 164492C2) and a late B star (HD 164492C3). Components C2 and C3 exhibit significant (>100 km s-1) bulk radial velocity variations with a period of 12.5351(7) d that we attribute to eccentric binary motion around a common centre-of-mass. Component C1 exhibits no detectable radial velocity variations. Using constraints derived from modelling the orbit of the C2+C3 binary and from synthesis of the combined spectrum, we determine the approximate physical characteristics of the components. We conclude that a coherent evolutionary solution consistent with the published age of M20 implies a distance to M20 of 0.9 ± 0.2 kpc, corresponding to the smallest published values. We confirm the detection of a strong magnetic field in the combined spectrum. The field is clearly associated with the broad-lined C1 component of the system. Repeated measurement of the longitudinal magnetic field allows the derivation of the rotation period of the magnetic star, Prot = 1.369 86(6) d. We derive the star's magnetic geometry, finding i=63± 6°, β =33± 6° and a dipole polar strength B_d=7.9^{+1.2}_{-1.0} kG. Strong emission - varying according to the magnetic period - is detected in the Hα profile. This is consistent with the presence of a centrifugal magnetosphere surrounding the rapidly rotating magnetic C1 component.

  20. SEARCHING FOR GAS GIANT PLANETS ON SOLAR SYSTEM SCALES: VLT NACO/APP OBSERVATIONS OF THE DEBRIS DISK HOST STARS HD172555 AND HD115892

    SciTech Connect

    Quanz, Sascha P.; Meyer, Michael R.; Kenworthy, Matthew A.; Girard, Julien H. V.; Kasper, Markus

    2011-08-01

    Using the Apodizing Phase Plate (APP) coronagraph of Very Large Telescope/NACO we searched for planetary mass companions around HD115892 and HD172555 in the thermal infrared at 4 {mu}m. Both objects harbor unusually luminous debris disks for their age and it has been suggested that small dust grains were produced recently in transient events (e.g., a collision) in these systems. Such a collision of planetesimals or protoplanets could have been dynamically triggered by yet unseen companions. We did not detect any companions in our images but derived the following detection limits: for both objects we would have detected companions with apparent magnitudes between {approx}13.2 and 14.1 mag at angular separations between 0.''4 and 1.''0 at the 5{sigma} level. For HD115892 we were sensitive to companions with 12.1 mag even at 0.''3. Using theoretical models these magnitudes are converted into mass limits. For HD115892 we would have detected objects with 10-15 M{sub Jup} at angular separations between 0.''4 and 1.''0 (7-18 AU). At 0.''3 ({approx}5.5 AU) the detection limit was {approx}>25 M{sub Jup}. For HD172555 we reached detection limits between 2 and 3 M{sub Jup} at separations between 0.''5 and 1.''0 (15-29 AU). At 0.''4 ({approx}11 AU) the detection limit was {approx}>4 M{sub Jup}. Despite the non-detections, our data demonstrate the unprecedented contrast performance of NACO/APP in the thermal infrared at very small inner working angles and we show that our observations are mostly background limited at separations {approx}>0.''5.

  1. Frequency analysis of the rapidly oscillating AP star HR 1217 (HD 24712)

    NASA Astrophysics Data System (ADS)

    Kurtz, D. W.; Seeman, J.

    1983-10-01

    High speed photometric observations of HR 1217 have been obtained during 119 hr on 18 nights in 1981. On five of those nights, contemporaneous observations were obtained at the South African Astronomical Observatory and Cerro Tololo Inter-American Observatory which greatly reduce the severe daily aliasing problem in the frequency analysis of this star. A frequency analysis of three nights of data at the phase of pulsation amplitude maximum reveals six nearly uniformly spaced frequencies which are thought to be associated with six consecutive overtones of pulsation. From the frequency ratios, the overtones of the pulsations are estimated at 76 to 81. Pulsation amplitude maximum coincides with magnetic maximum again for these data which, with previous data obtained in 1980 for this star, sets an upper limit of Ck, l at less than or equal to 0.002 at the 3-sigma level of confidence.

  2. Magnetic stars with wide depressions in the continuum. 1. The Ap star with strong silicon lines HD5601

    NASA Astrophysics Data System (ADS)

    Romanyuk, I. I.; Kudryavtsev, D. O.; Semenko, E. A.; Moiseeva, A. V.

    2016-10-01

    Based on observations with the 6-m SAO RAS telescope, we have found that chemically peculiar star with a large depression of the continuum at λ5200 Å and strengthened silicon lines in the spectrum has a strong magnetic field. The longitudinal field component B e has a negative polarity and varies from -300 G to -2000 G with a period of 1.756 days. Photometric variations of brightness take place with the same period. We determined the variability of the radial velocity at times of about tens of years pointing to a possible binarity of the object. We have built a magnetic model of this star, determined the inclination angles of the rotation axis to the line of sight i = 20° and of the dipole axis to the rotation axis β = 116°, and the field strength at the pole is B p = 10 kG. We carried out a chemical composition analysis and found a lack of helium for almost an order of magnitude, some overabundance of silicon and metal elements for more than an order of magnitude, particularly, cobalt for three orders of magnitude.

  3. The origin of the excess transit absorption in the HD 189733 system: planet or star?

    NASA Astrophysics Data System (ADS)

    Barnes, J. R.; Haswell, C. A.; Staab, D.; Anglada-Escudé, G.

    2016-10-01

    We have detected excess absorption in the emission cores of Ca II H&K during transits of HD 189733b for the first time. Using observations of three transits, we investigate the origin of the absorption, which is also seen in Hα and the Na I D lines. Applying differential spectrophotometry methods to the Ca II H and Ca II K lines combined, using respective passband widths of Δλ = 0.4 and 0.6 Å yields excess absorption of td = 0.0074 ± 0.0044 (1.7σ; Transit 1) and 0.0214 ± 0.0022 (9.8σ; Transit 2). Similarly, we detect excess Hα absorption in a passband of width Δλ = 0.7 Å, with td = 0.0084 ± 0.0016 (5.2σ) and 0.0121 ± 0.0012 (9.9σ). For both lines, Transit 2 is thus significantly deeper. Combining all three transits for the Na I D lines yields excess absorption of td = 0.0041 ± 0.0006 (6.5σ). By considering the time series observations of each line, we find that the excess apparent absorption is best recovered in the stellar reference frame. These findings lead us to postulate that the main contribution to the excess transit absorption in the differential light curves arises because the normalizing continuum bands form in the photosphere, whereas the line cores contain a chromospheric component. We cannot rule out that part of the excess absorption signature arises from the planetary atmosphere, but we present evidence which casts doubt on recent claims to have detected wind motions in the planet's atmosphere in these data.

  4. Line formation in winds with enhanced equatorial mass-loss rates and its application to the Wolf-Rayet star HD 50896

    NASA Technical Reports Server (NTRS)

    Rumpl, W. M.

    1980-01-01

    A model having a spherically symmetric velocity distribution with a higher density at the equatorial region was developed to simulate the UV spectrum of the Wolf-Rayet star HD 50896. The spectrum showed P Cygni-shaped profiles whose emissions are stronger than expected in a spherically symmetric stellar wind. The model was studied varying the inclination angle of the star-wind system and the polar to equatorial density ratios; it was shown that HD 50896 could possess a nonspherically symmetric wind and that its symmetry axis is inclined between 60 and 90 deg. It is possible that the velocity distribution of the wind could include an inner constant velocity plateau beyond which the wind accelerates to its terminal velocity as indicated by infrared continuum investigations.

  5. Pulsation spectrum of δ Scuti stars: the binary HD 50870 as seen with CoRoT and HARPS

    NASA Astrophysics Data System (ADS)

    Mantegazza, L.; Poretti, E.; Michel, E.; Rainer, M.; Baudin, F.; García Hernández, A.; Semaan, T.; Alvarez, M.; Amado, P. J.; Garrido, R.; Mathias, P.; Moya, A.; Suárez, J. C.; Auvergne, M.; Baglin, A.; Catala, C.; Samadi, R.

    2012-06-01

    Aims: We present the results obtained with the CoRoT satellite for HD 50870, a δ Sct star which was observed for 114.4 d. The aim of these observations was to evaluate the results obtained for HD 50844, the first δ Sct star monitored with CoRoT, on a longer time baseline. Methods: The 307,570 CoRoT datapoints were analysed with different techniques. The photometric observations were complemented over 15 nights of high-resolution spectroscopy with HARPS on a baseline of 25 d. These spectra were analysed to study the line profile variations and to derive the stellar physical parameters. Some uvby photometric observations were also obtained to better characterize the pulsation modes. Results: HD 50870 proved to be a low-amplitude, long-period spectroscopic binary system seen almost pole-on (i ≃ 21°). The brighter component, which also has the higher rotational velocity (vsini = 37.5 km s-1), is a δ Sct-type variable with a full light amplitude variation of about 0.04 mag. There is a dominant axisymmetric mode (17.16 d-1). Moreover, there are two groups of frequencies (about 19) in the intervals 6 - 9 and 13 - 18 d-1, with amplitudes ranging from a few mmag to 0.3 mmag. After the detection of about 250 terms (corresponding to an amplitude of about 0.045 mmag) a flat plateau appears in the power spectrum in the low-frequency region up to about 35 d-1. We were able to detect this plateau only thanks to the short cadence sampling of the CoRoT measurements (32 s). The density distribution vs. frequency of the detected frequencies seems to rule out the possibility that this plateau is the result of a process with a continuum power spectrum. The spacings of the strongest modes suggest a quasi-periodic pattern. We failed to find a satisfactory seismic model that simultaneously matches the frequency range, the position in the HR diagram, and the quasi-periodic pattern interpreted as a large separation. Nineteen modes were detected spectroscopically from the line profile

  6. The multiplicity of exoplanet host stars. Spectroscopic confirmation of the companions GJ 3021 B and HD 27442 B, one new planet host triple-star system, and global statistics

    NASA Astrophysics Data System (ADS)

    Mugrauer, M.; Neuhäuser, R.; Mazeh, T.

    2007-07-01

    Aims:We present new results from our ongoing multiplicity study of exoplanet host stars and present a list of 29 confirmed planet host multiple-star systems. Furthermore, we discuss the properties of these stellar systems and compare the properties of exoplanets detected in these systems with those of planets orbiting single stars. Methods: We used direct imaging to search for wide stellar and substellar companions of exoplanet host stars. With infrared and/or optical spectroscopy, we determined the spectral properties of the newly-found co-moving companions. Results: We obtained infrared H- and K-band spectra of the co-moving companion GJ 3021 B. The infrared spectra and the apparent H-band photometry of the companion is consistent with an M3-M5 dwarf at the distance of the exoplanet host star. HD 40979 AB is a wide planet host stellar system, with a separation of ~ 6400 AU. The companion to the exoplanet host star turned out to be a close stellar pair with a projected separation of ~130 AU, hence, this system is a new member of those rare planet host triple-star systems of which only three other systems are presently known. HD 27442 AB is a wide binary system listed in the Washington Double Star Catalogue, whose common proper motion was recently confirmed. This system is composed of the subgiant HD 27442 A hosting the exoplanet, and its faint companion HD 27442 B. The visible and infrared J-, H-, and K_S-band photometry of HD 27442 B at the distance of the primary star shows that the companion is probably a white dwarf. Our multi-epochs SofI imaging observations confirm this result and even refine the suggested physical characteristics of HD 27442 B. This companion should be a relatively young, hot white dwarf with an effective temperature of ~14 400 K, and cooling age of ~220 Myr. Finally, we could unambiguously confirm the white dwarf nature of HD 27442 B with follow-up optical and infrared spectroscopy. The spectra of the companion show Hydrogen absorption

  7. X-RAY EMISSION FROM THE DOUBLE-BINARY OB-STAR SYSTEM QZ CAR (HD 93206)

    SciTech Connect

    Parkin, E. R.; Naze, Y.; Rauw, G.; Broos, P. S.; Townsley, L. K.; Pittard, J. M.; Moffat, A. F. J.; Oskinova, L. M.; Waldron, W. L.

    2011-05-01

    X-ray observations of the double-binary OB-star system QZ Car (HD 93206) obtained with the Chandra X-ray Observatory over a period of roughly 2 years are presented. The respective orbits of systems A (O9.7 I+b2 v, P{sub A} = 21 days) and B (O8 III+o9 v, P{sub B} = 6 days) are reasonably well sampled by the observations, allowing the origin of the X-ray emission to be examined in detail. The X-ray spectra can be well fitted by an attenuated three-temperature thermal plasma model, characterized by cool, moderate, and hot plasma components at kT {approx_equal} 0.2, 0.7, and 2 keV, respectively, and a circumstellar absorption of {approx_equal}0.2 x 10{sup 22} cm{sup -2}. Although the hot plasma component could be indicating the presence of wind-wind collision shocks in the system, the model fluxes calculated from spectral fits, with an average value of {approx_equal}7 x 10{sup -13} erg s{sup -1} cm{sup -2}, do not show a clear correlation with the orbits of the two constituent binaries. A semi-analytical model of QZ Car reveals that a stable momentum balance may not be established in either system A or B. Yet, despite this, system B is expected to produce an observed X-ray flux well in excess of the observations. If one considers the wind of the O8 III star to be disrupted by mass transfer, the model and observations are in far better agreement, which lends support to the previous suggestion of mass transfer in the O8 III + o9 v binary. We conclude that the X-ray emission from QZ Car can be reasonably well accounted for by a combination of contributions mainly from the single stars and the mutual wind-wind collision between systems A and B.

  8. Large-scale Periodic Variability of the Wind of the Wolf-Rayet Star WR 1 (HD 4004)

    NASA Astrophysics Data System (ADS)

    Chené, A.-N.; St-Louis, N.

    2010-06-01

    We present the results of an intensive photometric and spectroscopic monitoring campaign of the WN4 Wolf-Rayet (WR) star WR 1 = HD 4004. Our broadband V photometry covering a timespan of 91 days shows variability with a period of P = 16.9+0.6 -0.3 days. The same period is also found in our spectral data. The light curve is non-sinusoidal with hints of a gradual change in its shape as a function of time. The photometric variations nevertheless remain coherent over several cycles and we estimate that the coherence timescale of the light curve is of the order of 60 days. The spectroscopy shows large-scale line-profile variability which can be interpreted as excess emission peaks moving from one side of the profile to the other on a timescale of several days. Although we cannot unequivocally exclude the unlikely possibility that WR 1 is a binary, we propose that the nature of the variability we have found strongly suggests that it is due to the presence in the wind of the WR star of large-scale structures, most likely corotating interaction regions (CIRs), which are predicted to arise in inherently unstable radiatively driven winds when they are perturbed at their base. We also suggest that variability observed in WR 6, WR 134, and WR 137 is of the same nature. Finally, assuming that the period of CIRs is related to the rotational period, we estimate the rotation rate of the four stars for which sufficient monitoring has been carried out, i.e., v rot = 6.5, 40, 70, and 275 km s-1 for WR 1, WR 6, WR 134, and WR 137, respectively. Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council of Canada, the Institut National des Sciences de l'Univers of the Centre National de Recherche Scientifique of France, and the University of Hawaii. Also based on observations obtained at the Observatoire du Mont Mégantic with is operated by the Centre de Recherche en Astrophysique du Québec and the Observatoire de

  9. UES and IUE observations of the O9.5 V star HD 93521: Non-radial pulsations, wind, and distance

    NASA Astrophysics Data System (ADS)

    Howarth, Ian D.; Reid, Andy H. N.

    1993-11-01

    We have obtained time-series spectroscopy of the rapidly rotating O9.5 V star HD 93521 during commissioning of the Utrecht Echelle Spectrograph (UES) on the William Herschel Telescope. The He I lines show 'wiggles' at the approximately 1% level, which move systematically from blue to red across the profile; by contrast, the He II lines do not show detectable variations. We interpret these characteristics as indicative of sectorial-mode non-radial pulsations coupled with significant gravity darkening, and estimate P = 1.8 hours, l = -m approximately equal to 9, k less than 0.3. The H-alpha and He I lambda 5876 lines show emission wings, and line-profile variability which may be associated with circumstellar material. If that inference is correct, and if (as is plausible) the material corotates, then the star's rotation period may be estimated as Prot approximately equal to 35 hr. We also examine IUE observations, which show no detectable variations in the wind on pulsation timescales. We show that the data provide direct observational evidence for a strong equator-to-pole asymmetry in the outflow velocity, confirming Massa's interpretation of the wind as being rotationally distorted; the star may possess a 'wind-compressed disc'. We estimate the equatorial and polar terminal velocities; a steady-state wind model predicts the observed maximum (approximately polar) velocity well. Reviewing the spectroscopic determination of stellar distances, taking rotation fully into account, we show that previous suggestions that HD 93521 may be a Population II star are in error. We present a self-consistent, illustrative set of stellar parameters which are in complete accord with the notion that HD 93521 is a rapidly rotating, but otherwise quite normal, Population I star at approximately 2 kpc.

  10. VizieR Online Data Catalog: Solar-type stars from SDSS-III MARVELS. VI. HD 87646 (Ma+, 2016)

    NASA Astrophysics Data System (ADS)

    Ma, B.; Ge, J.; Wolszczan, A.; Muterspaugh, M. W.; Lee, B.; Henry, G. W.; Schneider, D. P.; Martin, E. L.; Niedzielski, A.; Xie, J.; Fleming, S. W.; Thomas, N.; Williamson, M.; Zhu, Z.; Agol, E.; Bizyaev, D.; da Costa, L. N.; Jiang, P.; Fiorenzano, A. F. M.; Hernandez, J. I. G.; Guo, P.; Grieves, N.; Li, R.; Liu, J.; Mahadevan, S.; Mazeh, T.; Nguyen, D. C.; Paegert, M.; Sithajan, S.; Stassun, K.; Thirupathi, S.; van Eyken, J. C.; Wan, X.; Wang, J.; Wisniewski, J. P.; Zhao, B.; Zucker, S.

    2016-11-01

    We have obtained a total of 16 observations of HD87646 using the W.M. Keck Exoplanet Tracker (KeckET) from 2006 December to 2007 June. The radial velocities obtained are listed in Table1. The KeckET instrument was constructed in 2005 August-2006 February with support from the Keck Foundation. It was coupled with a wide field Sloan Digital Sky Survey telescope (SDSS) and used for the pilot Multi-Object APO RV Exoplanet Large-Area Survey (MARVELS). This is the sixth paper in this series, examining the low-mass companions around solar-type stars from the SDSS-III MARVELS survey (Wisniewski et al. 2012, Cat. J/AJ/143/107; Fleming et al. 2012AJ....144...72F; Ma et al. 2013AJ....145...20M; Jiang et al. 2013AJ....146...65J; De Lee et al. 2013AJ....145..155D). The KeckET instrument consists of eight subsystems-a multi-object fiber feed, an iodine cell, a fixed-delay interferometer system, a slit, a collimator, a grating, a camera, and a 4k*4k CCD detector. In addition, it contains four auxiliary subsystems: the interferometer control, an instrument calibration system, a photon flux monitoring system, and a thermal probe and control system. The instrument is fed with 60 fibers with 200μm core diameters, which are coupled to 180μm core diameter short fibers from the SDSS telescope, corresponding to 3arcsec on the sky at f/5. The resolving power for the spectrograph is R=5100, and the wavelength coverage is ~900Å, centered at 5400Å. KeckET has one spectrograph and one 4k*4k CCD camera that captures one of the two interferometer outputs, and has a 5.5% detection efficiency from the telescope to the detector without the iodine cell under the typical APO seeing conditions (~1.5arcsec seeing). The CCD camera records fringing spectra from 59 objects in a single exposure. Subsequent observations were performed using the Exoplanet Tracker (ET) instrument at Kitt Peak National Observatory (KPNO). Initial follow-up was performed in 2007 November. Additional data points were

  11. Improved Ti I log(gf) Values and New Titanium Abundances in the Sun and the Metal-Poor Star HD 84937

    NASA Astrophysics Data System (ADS)

    Sneden, Christopher; Guzman, A.; Lawler, J. E.; Wood, M. P.; Cowan, J. J.

    2013-01-01

    New atomic transition probability measurements for 948 lines of Ti I are reported. Branching fractions from Fourier transform spectra and from spectra recorded using a 3 m echelle spectrometer are combined with published radiative lifetimes from laser induced fluorescence measurements to determine these transition probabilities. Generally good agreement is found in comparisons to the NIST Atomic Spectra Database. These Ti I transition probability data are applied to high-resolution visible and UV spectra of the Sun and the very metal-poor main-sequence turnoff dwarf star HD 84937 to provide new, more accurate values of their titanium abundances. For the solar photosphere we use 168 lines to derive = 4.97 (σ = 0.04), in good agreement with the Ti abundance recommended in previous solar abundance reviews. For HD 84937 we derive = 3.12 (σ = 0.05, 54 lines), or [Ti/H] -1.85. We also determine a new HD 84937 iron metallicity from over 400 Fe I lines in the NIST atomic spectra database, obtaining = 5.18 (σ = 0.08) or [Fe/H] = -2.32. Combining these two results, for HD 84937 we derive [Ti/Fe] = +0.47. This work has been supported by grants NSF AST-0908978 and AST-1211585 (CS), AST-1211055 (JEL), and AST-1004881 (REU at University of Wisconsin).

  12. Iron Abundances in Atmospheres of HD10700 & HD146233

    NASA Astrophysics Data System (ADS)

    Ivanyuk, O.; Pavlenko, Ya. V.; Jenkins, J. S.; Jones, H. R. A.; Lyubchik, Yu.; Kaminsky, B.; Kuznetsov, M.

    2010-12-01

    There are many different means to determine physical parameters of stars and their abundances by spectral analysis. In our work we draw our attention to the rotational and microturbulence velocities as well as metallicities for the stars of known effective temperature and surface gravity. We carried fits of LTE synthetic spectra to the observed spectra of HD10700 and HD146233. THese stars are knows aa solar-twins except slightly higher rotational velocities in both cases and higher magnetical activity i of HD10700. We adopted ABEL software (Pavlenko Ya.V.) to fit to HD10700, HD146233 spectra obtained on Camino Observatory, Chilie. Selected stars looks like. We compare our results with previous work of Valenti & Fischer (2005).

  13. Stars with discrepant v sin i as derived from the Ca II 3933 and Mg II 4481 Å lines. VI. HD 199892 — an SB2 spectroscopic binary

    NASA Astrophysics Data System (ADS)

    Zverko, J.; Romanyuk, I.; Iliev, I.; Kudryavtsev, D.; Stateva, I.; Semenko, E.

    2017-01-01

    We analyzed the spectra of a well known SB1 binary HD199892 for which the projected rotational velocity v sin i, introduced in the literature, significantly differs when determined from the lines of Ca II at 3933 Å and ofMg II at 4481 Å. Contrary to the former findings, we discovered the signs of spectral lines of a companion star in the profile of Hβ as well as weak metallic lines in the high resolution high S/N spectra covering the most of the visual region. We estimated the secondary star to be a main sequence A4V star with a mass of 2.2 M ⊙ and derived its radial velocity which resulted in the mass of the primary M = 4.6 M ⊙. Short sections of the spectra in the Mg II 4481 Å and Ca II 3933 Å regions are analyzed as well.

  14. The Diverse Origins of Neutron-capture Elements in the Metal-poor Star HD 94028: Possible Detection of Products of i-Process Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Roederer, Ian U.; Karakas, Amanda I.; Pignatari, Marco; Herwig, Falk

    2016-04-01

    We present a detailed analysis of the composition and nucleosynthetic origins of the heavy elements in the metal-poor ([Fe/H] = -1.62 ± 0.09) star HD 94028. Previous studies revealed that this star is mildly enhanced in elements produced by the slow neutron-capture process (s process; e.g., [Pb/Fe] = +0.79 ± 0.32) and rapid neutron-capture process (r process; e.g., [Eu/Fe] = +0.22 ± 0.12), including unusually large molybdenum ([Mo/Fe] = +0.97 ± 0.16) and ruthenium ([Ru/Fe] = +0.69 ± 0.17) enhancements. However, this star is not enhanced in carbon ([C/Fe] = -0.06 ± 0.19). We analyze an archival near-ultraviolet spectrum of HD 94028, collected using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, and other archival optical spectra collected from ground-based telescopes. We report abundances or upper limits derived from 64 species of 56 elements. We compare these observations with s-process yields from low-metallicity AGB evolution and nucleosynthesis models. No combination of s- and r-process patterns can adequately reproduce the observed abundances, including the super-solar [As/Ge] ratio (+0.99 ± 0.23) and the enhanced [Mo/Fe] and [Ru/Fe] ratios. We can fit these features when including an additional contribution from the intermediate neutron-capture process (i process), which perhaps operated through the ingestion of H in He-burning convective regions in massive stars, super-AGB stars, or low-mass AGB stars. Currently, only the i process appears capable of consistently producing the super-solar [As/Ge] ratios and ratios among neighboring heavy elements found in HD 94028. Other metal-poor stars also show enhanced [As/Ge] ratios, hinting that operation of the i process may have been common in the early Galaxy. These data are associated with Program 072.B-0585(A), PI. Silva. Some data presented in this paper were obtained from the Barbara A. Mikulski Archive for Space Telescopes (MAST). The Space Telescope Science Institute is

  15. The tip of the iceberg: the frequency content of the δ Sct star HD 50844 from CoRoT space photometry

    NASA Astrophysics Data System (ADS)

    Poretti, E.; Mantegazza, L.; Rainer, M.; Uytterhoeven, K.; Michel, E.; Baglin, A.; Auvergne, M.; Catala, C.; Samadi, R.; Rodríguez, E.; Garrido, R.; Amado, P.; Martín-Ruiz, S.; Moya, A.; Suárez, J. C.; Baudin, F.; Zima, W.; Alvarez, M.; Mathias, P.; Paparó, M.; Pápics, P.; Plachy, E.

    2009-09-01

    It has been suggested that the detection of a wealth of very low amplitude modes in δ Sct stars was only a matter of signal-to-noise ratio. Access to this treasure, impossible from the ground, is one of the scientific aims of the space mission CoRoT, developed and operated by CNES. This work presents the results obtained on HD 50844: the 140,016 datapoints allowed us to reach the level of 10-5 mag in the amplitude spectra. The frequency analysis of the CoRoT timeseries revealed hundreds of terms in the frequency range 0-30 d-1. The initial guess that δ Sct stars have a very rich frequency content is confirmed. The spectroscopic mode identification gives theoretical support since very high-degree modes (up to = 14) are identified. We also prove that cancellation effects are not sufficient in removing the flux variations associated to these modes at the noise level of the CoRoT measurements. The ground-based observations indicate that HD 50844 is an evolved star that is slightly underabundant in heavy elements, located on the Terminal Age Main Sequence. The predominant term (f1 = 6.92 d-1) has been identified as the fundamental radial mode combining ground-based photometric and spectroscopic data.

  16. Probing the galactic disk and halo. 2: Hot interstellar gas toward the inner galaxy star HD 156359

    NASA Technical Reports Server (NTRS)

    Sembach, Kenneth R.; Savage, Blair D.; Lu, Limin

    1995-01-01

    We present Goddard High Resolution Spectrograph intermediate-resolution measurements of the 1233-1256 A spectral region of HD 156396, a halo star at l = 328.7 deg, b = -14.5 deg in the inner Galaxy with a line-of sight distance of 11.1 kpc and a z-distance of -2.8 kpc. The data have a resolution of 18 km/s Full Width at Half Maximum (FWHM) and a signal-to-noise ratio of approximately 50:1. We detect interstellar lines of Mg II, S II, S II, Ge II, and N V and determine log N/(Mg II) = 15.78 +0.25, -0.27, log N(Si II) greater than 13.70, log N(S II) greater than 15.76, log N(Ge II) = 12.20 +0.09,-0.11, and log N(N v) = 14.06 +/- 0.02. Assuming solar reference abundances, the diffuse clouds containing Mg, S, and Ge along the sight line have average logarithmic depletions D(Mg) = -0.6 +/- 0.3 dex, D(S) greater than -0.2 dex, and D(Ge) = -0.2 +/- 0.2 dex. The Mg and Ge depletions are approximately 2 times smaller than is typical of diffuse clouds in the solar vicinity. Galactic rotational modeling of the N v profiles indicates that the highly ionized gas traced by this ion has a scale height of approximately 1 kpc if gas at large z-distances corotates with the underlying disk gas. Rotational modeling of the Si iv and C iv profiles measured by the IUE satellite yields similar scale height estimates. The scale height results contrast with previous studies of highly ionized gas in the outer Milky Way that reveal a more extended gas distribtion with h approximately equals 3-4 kpc. We detect a high-velocity feature in N v and Si II v(sub LSR) approximately equals + 125 km/s) that is probably created in an interface between warm and hot gas.

  17. The pulsations of the B5IVe star HD 181231 observed with CoRoT and ground-based spectroscopy

    NASA Astrophysics Data System (ADS)

    Neiner, C.; Gutiérrez-Soto, J.; Baudin, F.; de Batz, B.; Frémat, Y.; Huat, A. L.; Floquet, M.; Hubert, A.-M.; Leroy, B.; Diago, P. D.; Poretti, E.; Carrier, F.; Rainer, M.; Catala, C.; Thizy, O.; Buil, C.; Ribeiro, J.; Andrade, L.; Emilio, M.; Espinosa Lara, F.; Fabregat, J.; Janot-Pacheco, E.; Martayan, C.; Semaan, T.; Suso, J.; Baglin, A.; Michel, E.; Samadi, R.

    2009-10-01

    Context: HD 181231 is a B5IVe star, which has been observed with the CoRoT satellite during ~5 consecutive months and simultaneously from the ground in spectroscopy and spectropolarimetry. Aims: By analysing these data, we aim to detect and characterize as many pulsation frequencies as possible, to search for the presence of beating effects possibly at the origin of the Be phenomenon. Our results will also provide a basis for seismic modelling. Methods: The fundamental parameters of the star are determined from spectral fitting and from the study of the circumstellar emission. The CoRoT photometric data and ground-based spectroscopy are analysed using several Fourier techniques: Clean-ng, Pasper, and Tisaft, as well as a time-frequency technique. A search for a magnetic field is performed by applying the LSD technique to the spectropolarimetric data. Results: We find that HD 181231 is a B5IVe star seen with an inclination of ~45 degrees. No magnetic field is detected in its photosphere. We detect at least 10 independent significant frequencies of variations among the 54 detected frequencies, interpreted in terms of non-radial pulsation modes and rotation. Two longer-term variations are also detected: one at ~14 days resulting from a beating effect between the two main frequencies of short-term variations, the other at ~116 days due either to a beating of frequencies or to a zonal pulsation mode. Conclusions: Our analysis of the CoRoT light curve and ground-based spectroscopic data of HD 181231 has led to the determination of the fundamental and pulsational parameters of the star, including beating effects. This will allow a precise seismic modelling of this star. Based on observations obtained with the CoRoT satellite, with FEROS at the 2.2 m télescope of the La Silla Observatory under the ESO Large Programme LP178.D-0361, with Narval at the Télescope Bernard Lyot of the Pic du Midi Observatory, and collected from the BeSS database. Table 5 is only available in

  18. MagAO Imaging of Long-period Objects (MILO). I. A Benchmark M Dwarf Companion Exciting a Massive Planet around the Sun-like Star HD 7449

    NASA Astrophysics Data System (ADS)

    Rodigas, Timothy J.; Arriagada, Pamela; Faherty, Jackie; Anglada-Escudé, Guillem; Kaib, Nathan; Butler, R. Paul; Shectman, Stephen; Weinberger, Alycia; Males, Jared R.; Morzinski, Katie M.; Close, Laird M.; Hinz, Philip M.; Crane, Jeffrey D.; Thompson, Ian; Teske, Johanna; Díaz, Matías; Minniti, Dante; Lopez-Morales, Mercedes; Adams, Fred C.; Boss, Alan P.

    2016-02-01

    We present high-contrast Magellan adaptive optics images of HD 7449, a Sun-like star with one planet and a long-term radial velocity (RV) trend. We unambiguously detect the source of the long-term trend from 0.6-2.15 μm at a separation of ˜0.″54. We use the object’s colors and spectral energy distribution to show that it is most likely an M4-M5 dwarf (mass ˜0.1-0.2 {M}⊙ ) at the same distance as the primary and is therefore likely bound. We also present new RVs measured with the Magellan/MIKE and Planet Finder Spectrograph spectrometers and compile these with archival data from CORALIE and HARPS. We use a new Markov chain Monte Carlo procedure to constrain both the mass (\\gt 0.17 {M}⊙ at 99% confidence) and semimajor axis (˜18 AU) of the M dwarf companion (HD 7449B). We also refine the parameters of the known massive planet (HD 7449Ab), finding that its minimum mass is {1.09}-0.19+0.52 MJ, its semimajor axis is {2.33}-0.02+0.01 AU, and its eccentricity is {0.8}-0.06+0.08. We use N-body simulations to constrain the eccentricity of HD 7449B to ≲0.5. The M dwarf may be inducing Kozai oscillations on the planet, explaining its high eccentricity. If this is the case and its orbit was initially circular, the mass of the planet would need to be ≲1.5 MJ. This demonstrates that strong constraints on known planets can be made using direct observations of otherwise undetectable long-period companions. This paper includes data obtained at the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  19. Three-dimensional magnetic and abundance mapping of the cool Ap star HD 24712 . I. Spectropolarimetric observations in all four Stokes parameters

    NASA Astrophysics Data System (ADS)

    Rusomarov, N.; Kochukhov, O.; Piskunov, N.; Jeffers, S. V.; Johns-Krull, C. M.; Keller, C. U.; Makaganiuk, V.; Rodenhuis, M.; Snik, F.; Stempels, H. C.; Valenti, J. A.

    2013-10-01

    Context. High-resolution spectropolarimetric observations provide simultaneous information about stellar magnetic field topologies and three-dimensional distributions of chemical elements. High-quality spectra in the Stokes IQUV parameters are currently available for very few early-type magnetic chemically peculiar stars. Here we present analysis of a unique full Stokes vector spectropolarimetric data set, acquired for the cool magnetic Ap star HD 24712 with a recently commissioned spectropolarimeter. Aims: The goal of our work is to examine the circular and linear polarization signatures inside spectral lines and to study variation of the stellar spectrum and magnetic observables as a function of rotational phase. Methods: HD 24712 was observed with the HARPSpol instrument at the 3.6-m ESO telescope over a period of 2010-2011. We achieved full rotational phase coverage with 43 individual Stokes parameter observations. The resulting spectra have a signal-to-noise ratio of 300-600 and resolving power exceeding 105. The multiline technique of least-squares deconvolution (LSD) was applied to combine information from the spectral lines of Fe-peak and rare earth elements. Results: We used the HARPSPol spectra of HD 24712 to study the morphology of the Stokes profile shapes in individual spectral lines and in LSD Stokes profiles corresponding to different line masks. From the LSD Stokes V profiles we measured the longitudinal component of the magnetic field, ⟨Bz⟩, with an accuracy of 5-10 G. We also determined the net linear polarization from the LSD Stokes Q and U profiles. Combining previous ⟨Bz⟩ measurements with our data allowed us to determine an improved rotational period of the star, Prot = 12.45812 ± 0.00019 d. We also measured the longitudinal magnetic field from the cores of Hα and Hβ lines. The analysis of ⟨Bz⟩ measurements showed no evidence for a significant radial magnetic field gradient in the atmosphere of HD 24712. We used our ⟨Bz⟩ and

  20. A Search for X-Ray Evidence of a Compact Companion to the Unusual Wolf-Rayet Star HD 50896 (EZ CMa)

    NASA Technical Reports Server (NTRS)

    Skinner, Stephen L.; Itoh, Masayuki; Nagase, Fumiaki

    1998-01-01

    We analyze results of a approx.25 ksec ASCA X-ray observation of the unusual Wolf-Rayet star HD 50896 (= EZ CMa). This WN5 star shows optical and ultraviolet variability at a 3.766 day period, which has been interpreted as a possible signature of a compact companion. Our objective was to search for evidence of hard X-rays (greater than or equal to 5 keV) which could be present if the WN5 wind is accreting onto a compact object. The ASCA spectra are dominated by emission below 5 keV and show no significant emission in the harder 5-10 keV range. Weak emission lines are present, and the X-rays arise in an optically thin plasma which spans a range of temperatures from less than or equal to 0.4 keV up to at least approx. 2 keV. Excess X-ray absorption above the interstellar value is present, but the column density is no larger than N(sub H) approx. 10(exp 22)/sq cm. The absorption-corrected X-ray luminosity L(sub x)(0.5 - 10 keV) = 10(exp 32.85) erg/s gives L(sub x)/ L(sub bol) approx. 10(exp -6), a value that is typical of WN stars. No X-ray variability was detected. Our main conclusion is that the X-ray properties of HD 50896 are inconsistent with the behavior expected for wind accretion onto a neutron star or black hole companion. Alternative models based on wind shocks can explain most aspects of the X-ray behavior, and we argue that the hotter plasma near approx. 2 keV could be due to the WR wind shocking onto a normal (nondegenerate) companion.

  1. IMPROVED Co i log(gf) VALUES AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937

    SciTech Connect

    Lawler, J. E.; Sneden, C.; Cowan, J. J. E-mail: chris@verdi.as.utexas.edu

    2015-09-15

    New emission branching fraction measurements for 898 lines of the first spectrum of cobalt (Co i) are determined from hollow cathode lamp spectra recorded with the National Solar Observatory 1 m Fourier transform spectrometer on Kitt Peak, AZ and a high-resolution echelle spectrometer. Published radiative lifetimes from laser induced fluorescence measurements are combined with the branching fractions to determine accurate absolute atomic transition probabilities for the 898 lines. Hyperfine structure (hfs) constants for levels of neutral Co in the literature are surveyed and selected values are used to generate complete hfs component patterns for 195 transitions of Co i. These new laboratory data are applied to determine the Co abundance in the Sun and metal-poor star HD 84937, yielding log ϵ(Co) = 4.955 ± 0.007 (σ = 0.059) based on 82 Co i lines and log ϵ(Co) = 2.785 ± 0.008 (σ = 0.065) based on 66 Co i lines, respectively. A Saha or ionization balance test on the photosphere of HD 84937 is performed using 16 UV lines of Co ii, and good agreement is found with the Co i result in this metal-poor ([Fe i/H] = −2.32, [Fe ii/H] = −2.32) dwarf star. The resulting value of [Co/Fe] = +0.14 supports a rise of Co/Fe at low metallicity that has been suggested in other studies.

  2. Variability of Disk Emission in Pre-main Sequence and Related Stars. IV. Occultation Events from the Innermost Disk Region of the Herbig AE Star HD 163296 = MWC 275

    NASA Astrophysics Data System (ADS)

    Pikhartova, Monika; Long, Zachary; Fernandes, Rachel B.; Sitko, Michael L.; Grady, Carol A.; Rich, Evan; Wisniewski, John P.

    2017-01-01

    We studied the structure and the dynamics of the innermost region of the circumstellar disk around the star HD 163296, MWC 275. We extracted the emission line strengths of Pa beta and Br gamma and calculated the line fluxes, from which we then computed the mass accretion rates onto the star. We investigated the brightness drop at visible wavelengths in 2001 using the Monte Carlo Radiative Transfer Code, hochunk3d. Since the star has bipolar outflows, we looked at whether changes in the outflow, with dust entrained with the gas, could produce such a drop in brightness. We fitted data from 2001 and 2005 onto SED and temperature-density models of the disk and generated JHK disk images, then noted the changes in image brightness and in SED plots.

  3. Two New Spotted Variables-HD 191262 and HD 191011

    NASA Astrophysics Data System (ADS)

    Hall, Douglas S.; Henry, Gregory W.

    1992-11-01

    New 1988-1990 photometry in V and B with a 16 inch automatic telescope shows that both HD 191262, a previously known chromospherically active binary, and its comparison star HD 191011 are variable, with starspots judged to be the mechanism in both. In HD 191262 and 191011, respectively, spot rotation periods of 5d.4 < P < 5d.7 and 1 7d.4 < P < 23d.0 were found and differential rotation coefficients of k=0.054 and 0.28 were estimated. HD 191011, shown to be a KS giant about 475 parsecs away, had eight different spots present during the 2.5 years of observation.

  4. Exploring atmospheres of hot mini-Neptune and extrasolar giant planets orbiting different stars with application to HD 97658b, WASP-12b, CoRoT-2b, XO-1b, and HD 189733b

    SciTech Connect

    Miguel, Y.; Kaltenegger, L.

    2014-01-10

    We calculated an atmospheric grid for hot mini-Neptune and giant exoplanets that links astrophysical observable parameters—orbital distance and stellar type—with the chemical atmospheric species expected. The grid can be applied to current and future observations to characterize exoplanet atmospheres and serves as a reference to interpret atmospheric retrieval analysis results. To build the grid, we developed a one-dimensional code for calculating the atmospheric thermal structure and linked it to a photochemical model that includes disequilibrium chemistry (molecular diffusion, vertical mixing, and photochemistry). We compare the thermal profiles and atmospheric composition of planets at different semimajor axes (0.01 AU ≤ a ≤ 0.1 AU) orbiting F, G, K, and M stars. Temperature and UV flux affect chemical species in the atmosphere. We explore which effects are due to temperature and which are due to stellar characteristics, showing the species most affected in each case. CH{sub 4} and H{sub 2}O are the most sensitive to UV flux, H displaces H{sub 2} as the most abundant gas in the upper atmosphere for planets receiving a high UV flux. CH{sub 4} is more abundant for cooler planets. We explore vertical mixing, to inform degeneracies on our models and in the resulting spectral observables. For lower pressures, observable species like H{sub 2}O or CO{sub 2} can indicate the efficiency of vertical mixing, with larger mixing ratios for a stronger mixing. By establishing the grid, testing the sensitivity of the results, and comparing our model to published results, our paper provides a tool to estimate what observations could yield. We apply our model to WASP-12b, CoRoT-2b, XO-1b, HD189733b, and HD97658b.

  5. Variability of Disk Emission in Pre-main Sequence and Related Stars. V. Changes in the Innermost Disk Structure of the Herbig AE Star HD 31648 = MWC 480

    NASA Astrophysics Data System (ADS)

    Fernandes, Rachel; Long, Zachary; Sitko, Michael L.; Grady, C. A.; Kusakabe, Nobuhiko

    2017-01-01

    We present five epochs of near IR observations of the protoplanetary disk around HD 31648 (MWC 480). A mass accretion rate of approximately 1.1×10-7 Msun/year was derived from Brγ and Paβ lines. The spectral energy distribution (SED) reveals a variability of about 30% between 1.5 and 10 microns. We present the theoretical modeling analysis of the disk in HD 31648 using Monte-Carlo Radiation Transfer Code (MRTC). We find that varying the height of the inner rim successfully produces a shift in the NIR flux.

  6. Identification of the emission features near 3.5 microns in the pre main sequence star HD 97048

    NASA Technical Reports Server (NTRS)

    Baas, F.; Allamandola, L. J.; Geballe, T. R.; Persson, S. E.; Lacy, J. H.

    1982-01-01

    The spectrum of HD97048 was measured with a resolving power of 450 between 3.37 and 3.64 microns. The prominent feature near 3.5 microns is well resolved, with a peak at 3.53 microns and a wing extending to a shorter wavelength. The weaker feature near 3.4 microns is found to peak at 3.43 microns, in contrast to the 3.40 micron feature seen in other astronomical objects. The observed spectrum strongly resembles laboratory spectra of mixtures of monomeric and dimeric formaldehyde embedded in low temperature solids. Of various possible excitation mechanisms, ultraviolet pumped infrared fluorescence of formaldehyde in interstellar grains provides the best explanation for the observed spectrum of HD 97048.

  7. IMPROVED V I log(gf) VALUES AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937

    SciTech Connect

    Lawler, J. E.; Wood, M. P.; Den Hartog, E. A.; Feigenson, T.; Sneden, C.; Cowan, J. J. E-mail: mpwood@wisc.edu E-mail: tfeigenson@wisc.edu E-mail: cowan@nhn.ou.edu

    2015-01-01

    New emission branching fraction measurements for 836 lines of the first spectrum of vanadium (V I) are determined from hollow cathode lamp spectra recorded with the National Solar Observatory 1 m Fourier transform spectrometer (FTS) and a high-resolution echelle spectrometer. The branching fractions are combined with recently published radiative lifetimes from laser-induced fluorescence measurements to determine accurate absolute atomic transition probabilities for the 836 lines. The FTS data are also used to extract new hyperfine structure A coefficients for 26 levels of neutral vanadium. These new laboratory data are applied to determine the V abundance in the Sun and metal-poor star HD 84937, yielding log ε(V) = 3.956 ± 0.004 (σ = 0.037) based on 93 V I lines and log ε(V) = 1.89 ± 0.03 (σ = 0.07) based on nine V I lines, respectively, using the Holweger-Müller 1D model. These new V I abundance values for the Sun and HD 84937 agree well with our earlier determinations based upon V II.

  8. IMPROVED V II log(gf) VALUES, HYPERFINE STRUCTURE CONSTANTS, AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937

    SciTech Connect

    Wood, M. P.; Lawler, J. E.; Den Hartog, E. A.; Sneden, C.; Cowan, J. J. E-mail: jelawler@wisc.edu E-mail: chris@verdi.as.utexas.edu

    2014-10-01

    New experimental absolute atomic transition probabilities are reported for 203 lines of V II. Branching fractions are measured from spectra recorded using a Fourier transform spectrometer and an echelle spectrometer. The branching fractions are normalized with radiative lifetime measurements to determine the new transition probabilities. Generally good agreement is found between this work and previously reported V II transition probabilities. Two spectrometers, independent radiometric calibration methods, and independent data analysis routines enable a reduction in systematic uncertainties, in particular those due to optical depth errors. In addition, new hyperfine structure constants are measured for selected levels by least squares fitting line profiles in the FTS spectra. The new V II data are applied to high resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to determine new, more accurate V abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. Very good agreement is found between our new solar photospheric V abundance, log ε(V) = 3.95 from 15 V II lines, and the solar-system meteoritic value. In HD 84937, we derive [V/H] = –2.08 from 68 lines, leading to a value of [V/Fe] = 0.24.

  9. Light Curve Solution of HD 93205 (O3 V+O8 V) Containing the Earliest Known Star in a Well-studied Binary

    NASA Astrophysics Data System (ADS)

    Antokhina, Eleonora A.; Moffat, Anthony F. J.; Antokhin, Igor I.; Bertrand, Jean-François; Lamontagne, Robert

    2000-01-01

    We present the results of an extensive photometric study of the O3 V+O8 V binary HD 93205 (P~=6.08d, e=0.46). The primary O3 V star has by far the earliest known spectral type of a normal star in a cataloged close binary. Some 186 individual differential observations, each of precision ~0.003 mag, were obtained over a contiguous interval of ~3 months in a narrow, visual-continuum bandpass. The amplitude of photometric variability is very low, about 0.02 mag, with most of the light changes occurring near periastron passage. Analysis of the light variations with a state-of-the-art binary model in an eccentric orbit leads to the conclusion that the system does not exhibit eclipses. Rather, the light variations are due mainly to orbital revolution of tidally distorted stars. However, there is an additional very small, but real, systematic decreasing trend in the light curve of the system approximately centered on the apastron passage, i.e., between orbital phases 0.35 and 1.0, which cannot be accounted for with present models. A nonuniform brightness distribution on the surface of the star(s), whose origin remains a mystery, may be responsible for this effect. Another plausible explanation of the trend may be related to turbulent viscosity, causing tidal lag. Despite this problem, one can estimate the range of possible values for the orbital inclination angle, e.g., at the 5% significance level, 75deg>=i>=35deg, which leads to the masses MO3~=32-154 Msolar and MO8~=14-68 Msolar. The best-fit value, i=60deg, yields MO3=45 Msolar and MO8=20 Msolar. The latter value is compatible with the reliable masses of the two O8 V stars (22 Msolar) in the detached eclipsing binary system EM Car. This would imply that at least one of the earliest known main-sequence O3 stars has relatively modest mass, compared to evolutionary masses of the most massive stars, which are claimed elsewhere in the literature to reach up to at least 100 Msolar.

  10. IMPROVED Ni I log(gf) VALUES AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937

    SciTech Connect

    Wood, M. P.; Lawler, J. E.; Sneden, C.; Cowan, J. J. E-mail: jelawler@wisc.edu E-mail: cowan@nhn.ou.edu

    2014-04-01

    Atomic transition probability measurements for 371 Ni I lines in the UV through near-IR are reported. Branching fractions from data recorded using a Fourier transform spectrometer and a new echelle spectrograph are combined with published radiative lifetimes to determine these transition probabilities. Generally good agreement is found in comparisons to previously reported Ni I transition probability measurements. Use of the new echelle spectrograph, independent radiometric calibration methods, and independent data analysis routines enable a reduction of systematic errors and overall improvement in transition probability uncertainty over previous measurements. The new Ni I data are applied to high-resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to derive new, more accurate Ni abundances. Lines covering a wide range of wavelength and excitation potential are used to search for non-LTE effects.

  11. Improved Cr II log(gf) Values and Abundance Determinations in the Photospheres of the Sun and Metal-poor Star HD 84937

    NASA Astrophysics Data System (ADS)

    Lawler, J. E.; Sneden, C.; Nave, G.; Den Hartog, E. A.; Emrahoğlu, N.; Cowan, J. J.

    2017-01-01

    New emission branching fraction (BF) measurements for 183 lines of the second spectrum of chromium (Cr ii) and new radiative lifetime measurements from laser-induced fluorescence for 8 levels of Cr+ are reported. The goals of this study are to improve transition probability measurements in Cr ii and reconcile solar and stellar Cr abundance values based on Cr i and Cr ii lines. Eighteen spectra from three Fourier Transform Spectrometers supplemented with ultraviolet spectra from a high-resolution echelle spectrometer are used in the BF measurements. Radiative lifetimes from this study and earlier publications are used to convert the BFs into absolute transition probabilities. These new laboratory data are applied to determine the Cr abundance log ε in the Sun and metal-poor star HD 84937. The mean result in the Sun is < {log}\\varepsilon ({Cr} {{II}})> = 5.624 ± 0.009 compared to < {log}\\varepsilon ({Cr} {{I}})> = 5.644 ± 0.006 on a scale with the hydrogen abundance log ε(H) = 12 and with the uncertainty representing only line-to-line scatter. A Saha (ionization balance) test on the photosphere of HD 84937 is also performed, yielding < {log}\\varepsilon ({Cr} {{II}})> = 3.417 ± 0.006 and 0 eV)> = 3.374 ± 0.011 for this dwarf star. We find a correlation of Cr with the iron-peak element Ti, suggesting an associated nucleosynthetic production. Four iron-peak elements (Cr along with Ti, V, and Sc) appear to have a similar (or correlated) production history—other iron-peak elements appear not to be associated with Cr.

  12. Three-dimensional hydrodynamical CO5BOLD model atmospheres of red giant stars. V. Oxygen abundance in the metal-poor giant HD 122563 from OH UV lines

    NASA Astrophysics Data System (ADS)

    Prakapavičius, D.; Kučinskas, A.; Dobrovolskas, V.; Klevas, J.; Steffen, M.; Bonifacio, P.; Ludwig, H.-G.; Spite, M.

    2017-03-01

    Context. Although oxygen is an important tracer of the early Galactic evolution, its abundance trends with metallicity are still relatively poorly known at [Fe/H] ≲ -2.5. This is in part due to a lack of reliable oxygen abundance indicators in the metal-poor stars, and in part due to shortcomings in 1D LTE abundance analyses where different abundance indicators, such as OH lines located in the UV and IR or the forbidden [O I] line at 630 nm, frequently provide inconsistent results. Aims: In this study, we determined the oxygen abundance in the metal-poor halo giant HD 122563 using a 3D hydrodynamical CO5BOLD model atmosphere. Our main goal was to understand whether a 3D LTE analysis can help to improve the reliability of oxygen abundances that are determined from OH UV lines in comparison to those obtained using standard 1D LTE methodology. Methods: The oxygen abundance in HD 122563 was determined using 71 OH UV lines located in the wavelength range between 308-330 nm. The analysis was performed using a high-resolution VLT UVES spectrum with a 1D LTE spectral line synthesis performed using the SYNTHE package and classical ATLAS9 model atmosphere. Subsequently, a 3D hydrodynamical CO5BOLD and 1D hydrostatic LHD model atmospheres were used to compute 3D-1D abundance corrections. For this, the microturbulence velocity used with the 1D LHD model atmosphere was derived from the hydrodynamical CO5BOLD model atmosphere of HD 122563. The obtained abundance corrections were then applied to determine 3D LTE oxygen abundances from each individual OH UV line. Results: As in previous studies, we found trends in the 1D LTE oxygen abundances determined from OH UV lines with line parameters, such as the line excitation potential, χ, and the line equivalent width, W. These trends become significantly less pronounced in 3D LTE. Using OH UV lines, we determined a 3D LTE oxygen abundance in HD 122563 of A(O)3D LTE = 6.23 ± 0.13 ([O/Fe] = 0.07 ± 0.13). This is in fair agreement

  13. IMPROVED Ti II log(gf) VALUES AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937

    SciTech Connect

    Wood, M. P.; Lawler, J. E.; Sneden, C.; Cowan, J. J. E-mail: jelawler@wisc.edu E-mail: cowan@nhn.ou.edu

    2013-10-01

    Atomic transition probability measurements for 364 lines of Ti II in the UV through near-IR are reported. Branching fractions from data recorded using a Fourier transform spectrometer (FTS) and a new echelle spectrometer are combined with published radiative lifetimes to determine these transition probabilities. The new results are in generally good agreement with previously reported FTS measurements. Use of the new echelle spectrometer, independent radiometric calibration methods, and independent data analysis routines enables a reduction of systematic errors and overall improvement in transition probability accuracy over previous measurements. The new Ti II data are applied to high-resolution visible and UV spectra of the Sun and metal-poor star HD 84937 to derive new, more accurate Ti abundances. Lines covering a range of wavelength and excitation potential are used to search for non-LTE effects. The Ti abundances derived using Ti II for these two stars match those derived using Ti I and support the relative Ti/Fe abundance ratio versus metallicity seen in previous studies.

  14. NEWLY DISCOVERED PLANETS ORBITING HD 5319, HD 11506, HD 75784 AND HD 10442 FROM THE N2K CONSORTIUM

    SciTech Connect

    Giguere, Matthew J.; Fischer, Debra A.; Brewer, John M.; Payne, Matthew J.; Johnson, John Asher; Howard, Andrew W.; Isaacson, Howard T.

    2015-01-20

    Initially designed to discover short-period planets, the N2K campaign has since evolved to discover new worlds at large separations from their host stars. Detecting such worlds will help determine the giant planet occurrence at semi-major axes beyond the ice line, where gas giants are thought to mostly form. Here we report four newly discovered gas giant planets (with minimum masses ranging from 0.4 to 2.1 M {sub Jup}) orbiting stars monitored as part of the Next 2000 target stars (N2K) Doppler Survey program. Two of these planets orbit stars already known to host planets: HD 5319 and HD 11506. The remaining discoveries reside in previously unknown planetary systems: HD 10442 and HD 75784. The refined orbital period of the inner planet orbiting HD 5319 is 641 days. The newly discovered outer planet orbits in 886 days. The large masses combined with the proximity to a 4:3 mean motion resonance make this system a challenge to explain with current formation and migration theories. HD 11506 has one confirmed planet, and here we confirm a second. The outer planet has an orbital period of 1627.5 days, and the newly discovered inner planet orbits in 223.6 days. A planet has also been discovered orbiting HD 75784 with an orbital period of 341.7 days. There is evidence for a longer period signal; however, several more years of observations are needed to put tight constraints on the Keplerian parameters for the outer planet. Lastly, an additional planet has been detected orbiting HD 10442 with a period of 1043 days.

  15. An in-depth study of HD 174966 with CoRoT photometry and HARPS spectroscopy. Large separation as a new observable for δ Scuti stars

    NASA Astrophysics Data System (ADS)

    García Hernández, A.; Moya, A.; Michel, E.; Suárez, J. C.; Poretti, E.; Martín-Ruíz, S.; Amado, P. J.; Garrido, R.; Rodríguez, E.; Rainer, M.; Uytterhoeven, K.; Rodrigo, C.; Solano, E.; Rodón, J. R.; Mathias, P.; Rolland, A.; Auvergne, M.; Baglin, A.; Baudin, F.; Catala, C.; Samadi, R.

    2013-11-01

    Aims: The aim of this work was to use a multi-approach technique to derive the most accurate values possible of the physical parameters of the δ Sct star HD 174966, which was observed with the CoRoT satellite. In addition, we searched for a periodic pattern in the frequency spectra with the goal of using it to determine the mean density of the star. Methods: First, we extracted the frequency content from the CoRoT light curve. Then, we derived the physical parameters of HD 174966 and carried a mode identification out from the spectroscopic and photometric observations. We used this information to look for the models fulfilling all the conditions and discussed the inaccuracies of the method because of the rotation effects. In a final step, we searched for patterns in the frequency set using a Fourier transform, discussed its origin, and studied the possibility of using the periodicity to obtain information about the physical parameters of the star. Results: A total of 185 peaks were obtained from the Fourier analysis of the CoRoT light curve, all of which were reliable pulsating frequencies. From the spectroscopic observations, 18 oscillation modes were detected and identified, and the inclination angle (62.5°-17.5+7.5) and the rotational velocity of the star (142 km s-1) were estimated. From the multi-colour photometric observations, only three frequencies were detected that correspond to the main ones in the CoRoT light curve. We looked for periodicities within the 185 frequencies and found a quasiperiodic pattern Δν ~ 64 μHz. Using the inclination angle, the rotational velocity, and an Echelle diagram (showing a double comb outside the asymptotic regime), we concluded that the periodicity corresponds to a large separation structure. The quasiperiodic pattern allowed us to discriminate models from a grid. As a result, the value of the mean density is achieved with a 6% uncertainty. So, the Δν pattern could be used as a new observable for A-F type stars. The

  16. Evidence for the pulsational origin of the Long Secondary Periods: The red supergiant star V424 Lac (HD 216946)

    NASA Astrophysics Data System (ADS)

    Messina, Sergio

    2007-10-01

    The results of a long-term UBV photometric monitoring of the red supergiant (RSG) star V424 Lac are presented. V424 Lac shows multiperiodic brightness variations which can be attributed to pulsational oscillations. A much longer period ( P = 1601 d), that allows us to classify this star as a long secondary period variable star (LSPV) has been also detected. The B - V and U - B color variations related to the long secondary period (LSP) are similar to those related to the shorter periods, supporting the pulsational nature of LSP. The long period brightness variation of V424 Lac is accompanied by a near-UV (NUV) excess, which was spectroscopically detected in a previous study [Massey, P., Plez, B., Levesque, E.M., et al., 2005. ApJ 634, 1286] and which is now found to be variable from photometry. On the basis of the results found for V424 Lac, the NUV excess recently found in a number of RSGs may be due not solely to circumstellar dust but may also have a contribution from a still undetected LSP variability.

  17. Improved Cr II log(gf)s and Cr Abundances in the Photospheres of the Sun and Metal-Poor Star HD 84937

    NASA Astrophysics Data System (ADS)

    Lawler, James E.; Sneden, Chris; Nave, Gillian; Den Hartog, Elizabeth; Emrahoglu, Nuri; Cowan, John J.

    2017-01-01

    New laser induced fluorescence (LIF) data for eight levels of singly ionized chromium (Cr) and emission branching fraction (BF) measurements for 183 lines of the second spectrum of chromium (Cr II) are reported. A goal of this study is to reconcile Solar and stellar Cr abundance values based on Cr I and Cr II lines. Analyses of eighteen spectra from three Fourier Transform Spectrometers supplemented with ultraviolet spectra from a high resolution echelle spectrometer yield the BF measurements. Radiative lifetimes from LIF measurements are used to convert the BFs to absolute transition probabilities. These new laboratory data are applied to determine the Cr abundance log eps in the Sun and metal-poor star HD 84937. The mean result in the Sun is = 5.624 ± 0.009 compared to = 5.644 ± 0.006 on a scale with the H abundance log eps(H) = 12. Similarily the photosphere of HD 84937 is found to be in Saha balance with = 3.417 ± 0.006 and 0 eV) > = 3.374 ± 0.011 for this dwarf star. The resonance (E.P. = 0 eV) lines of Cr I reveal overionization of the ground level of neutral Cr. We find a correlation of Cr with the iron-peak element Ti, suggesting an associated or related nucleosynthetic production. Four iron-peak elements (Cr along with Ti, V and Sc) appear to have a similar (or correlated) production history - other iron-peak elements appear not to be associated with Cr.This work is supported in part by NASA grant NNX16AE96G (J.E.L.), by NSF grant AST-1516182 (J.E.L. & E.D.H.), by NASA interagency agreement NNH10AN381 (G.N.), and NSF grant AST-1211585 (C.S.). Postdoctoral research support for N. E. is from the Technological and Scientific Research Council of Turkey (TUBITAK).

  18. Rare-earth elements in the atmosphere of the magnetic chemically peculiar star HD 144897. New classification of the Nd III spectrum

    NASA Astrophysics Data System (ADS)

    Ryabchikova, T.; Ryabtsev, A.; Kochukhov, O.; Bagnulo, S.

    2006-09-01

    Context: . The chemically peculiar stars of the upper main sequence represent a natural laboratory for the study of rare-earth elements (REE). Aims: . We want to check the reliability of the energy levels and atomic line parameters for the second REE ions currently available in the literature, and obtained by means of experiments and theoretical calculations. Methods: . We have obtained a UVES spectrum of a slowly rotating strongly magnetic Ap star, HD 144897, that exhibits very large overabundances of rare-earth elements. Here we present a detailed spectral analysis of this object, taking effects of non-uniform vertical distribution (stratification) of chemical elements into account. Results: . We determined the photospheric abundances of 40 ions. For seven elements (Mg, Si, Ca, Ti, Cr, Mn, Fe), we obtained a stratification model that allows us to produce a satisfactory fit to the observed profiles of spectral lines of various strengths. All the stratified elements but Cr show a steep decrease in concentration toward the upper atmospheric layers; for Cr the transition from high to low concentration regions appears smoother than for the other elements. The REEs abundances, which have been determined for the first time from the lines of the first and second ions, have been found typically four dex higher than solar abundances. Our analysis of REE spectral lines provides strong support for the laboratory line classification and determination of the atomic parameters. The only remarkable exception is Nd iii, for which spectral synthesis was found to be inconsistent with the observations. We therefore performed a revision of the Nd iii classification. We confirmed the energies for 11 out of 24 odd energy levels that were classified previously, and derived the energies for additional 24 levels of Nd iii, thereby substantially increasing the number of classified Nd iii lines with corrected wavelengths and atomic parameters.

  19. Improved log(gf) Values for Lines of V I and V II, New Vanadium Abundances in the Sun and the Metal-Poor Star HD 84937

    NASA Astrophysics Data System (ADS)

    Lawler, James E.; Wood, Michael P.; Den Hartog, Elizabeth; Feigenson, Thomas; Sneden, Chris; Cowan, John J.

    2015-01-01

    New emission branching fraction measurements for 836 lines of the first spectrum of vanadium (V I) and 203 lines of V II are determined from hollow cathode lamp spectra recorded with the National Solar Observatory 1m Fourier transform spectrometer (FTS) and a high resolution echelle spectrometer. The branching fractions are combined with new radiative lifetimes from laser induced fluorescence measurements to determine accurate absolute atomic transition probabilities for 1039 lines of V I and V II. The FTS data are also used to extract new hyperfine structure A coefficients for both spectra. These new laboratory data are applied to determine the V abundance in the Sun and metal-poor star HD 84937, yielding log ɛ(V) = 3.96 (σ = 0.04) based on 93 V I lines and log ɛ(V) = 1.89 (σ = 0.07) based on nine V I lines respectively, and yielding log ɛ(V) = 3.95 (σ = 0.05) based on 15 V II lines and log ɛ(V) = 1.87 (σ = 0.07) based on 68 V II lines respectively1-3.1. Wood et al., ApJS 214:18 (2014), 2. Den Hartog et al. ApJS in press (2014), 3. Lawler et al. ApJS submitted (2014). This work is supported by NASA grant NNX10AN93G (JEL), NSF AST-1211055 (EDH & JEL), and NSF AST-1211585 (CS).

  20. Synthetic uvby-beta photometry of HD 12856 and HD 13890

    NASA Technical Reports Server (NTRS)

    Torres, A. V.; Garmany, C. D.

    1987-01-01

    Stromgren and H-beta colors have been measured from spectrophotometric observations of two Be stars without published photometry in Per OB1: HD 12856 (B0 pe) and HD 13890 (B1 III:pe). Stellar parameters and improved spectral types are then derived from the color indices and the calibrations of Jakobsen (1986). These are compared with the parameters of normal B stars and are used to estimate the evolutionary status of the stars.

  1. Very Low-mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. VI. A Giant Planet and a Brown Dwarf Candidate in a Close Binary System HD 87646

    NASA Astrophysics Data System (ADS)

    Ma, Bo; Ge, Jian; Wolszczan, Alex; Muterspaugh, Matthew W.; Lee, Brian; Henry, Gregory W.; Schneider, Donald P.; Martín, Eduardo L.; Niedzielski, Andrzej; Xie, Jiwei; Fleming, Scott W.; Thomas, Neil; Williamson, Michael; Zhu, Zhaohuan; Agol, Eric; Bizyaev, Dmitry; Nicolaci da Costa, Luiz; Jiang, Peng; Martinez Fiorenzano, A. F.; González Hernández, Jonay I.; Guo, Pengcheng; Grieves, Nolan; Li, Rui; Liu, Jane; Mahadevan, Suvrath; Mazeh, Tsevi; Nguyen, Duy Cuong; Paegert, Martin; Sithajan, Sirinrat; Stassun, Keivan; Thirupathi, Sivarani; van Eyken, Julian C.; Wan, Xiaoke; Wang, Ji; Wisniewski, John P.; Zhao, Bo; Zucker, Shay

    2016-11-01

    We report the detections of a giant planet (MARVELS-7b) and a brown dwarf (BD) candidate (MARVELS-7c) around the primary star in the close binary system, HD 87646. To the best of our knowledge, it is the first close binary system with more than one substellar circumprimary companion that has been discovered. The detection of this giant planet was accomplished using the first multi-object Doppler instrument (KeckET) at the Sloan Digital Sky Survey (SDSS) telescope. Subsequent radial velocity observations using the Exoplanet Tracker at the Kitt Peak National Observatory, the High Resolution Spectrograph at the Hobby Eberley telescope, the “Classic” spectrograph at the Automatic Spectroscopic Telescope at the Fairborn Observatory, and MARVELS from SDSS-III confirmed this giant planet discovery and revealed the existence of a long-period BD in this binary. HD 87646 is a close binary with a separation of ˜22 au between the two stars, estimated using the Hipparcos catalog and our newly acquired AO image from PALAO on the 200 inch Hale Telescope at Palomar. The primary star in the binary, HD 87646A, has {T}{eff} = 5770 ± 80 K, log g = 4.1 ± 0.1, and [Fe/H] = -0.17 ± 0.08. The derived minimum masses of the two substellar companions of HD 87646A are 12.4 ± 0.7 {M}{Jup} and 57.0 ± 3.7 {M}{Jup}. The periods are 13.481 ± 0.001 days and 674 ± 4 days and the measured eccentricities are 0.05 ± 0.02 and 0.50 ± 0.02 respectively. Our dynamical simulations show that the system is stable if the binary orbit has a large semimajor axis and a low eccentricity, which can be verified with future astrometry observations.

  2. Radial Pulsation and the Rotation Period of the Rapidly Oscillating Ap-Star Alpha-Circini HR:5463 HD128898

    NASA Astrophysics Data System (ADS)

    Kurtz, D. W.; Martinez, P.; Ashley, R. P.

    1993-10-01

    A frequency analysis of 211 h of high-speed photometric observations obtained in 1981, 1983 and 1992 shows that α Cir pulsates in two modes with frequencies ν1 =2442.023±0.016 μHz and ν2 =2439.427±0.016 μHz, separated by ν1-ν2 = 2.60±0.02 μHz. This separation suggests that ν1 is a mode of overtone n ≍ =35-40 and degree l=0, while ν2 has overtone and degree of n-1 and l=2. The principal frequency, ν1, however, is phase-modulated. The modulation period may be 524.2 d, in which case α Cir is a binary star with a reasonable probability that the secondary is of substellar mass. The modulation period may be 0.995 350 d, which is then the rotation period, in which case it can be shown that the principal frequency cannot be represented purely by a radial spherical harmonic pulsation mode. A decomposition of a derived frequency triplet indicates that, for most values of the rotational inclination i and the magnetic obliquity β, the mode is mostly a radial mode with a smaller dipole distortion. We suggest that the rotational inclination i ≤ 12° and the magnetic obliquity is large, which means that the magnetic field is seen always from an unfavourable aspect. The suggested rotation period, Prot=0.995350±0.000005 d, is so close to one sidereal day that it must be confirmed with multisite observations. If it is not confirmed, then the binary model becomes more attractive.

  3. LOCATING PLANETESIMAL BELTS IN THE MULTIPLE-PLANET SYSTEMS HD 128311, HD 202206, HD 82943, AND HR 8799

    SciTech Connect

    Moro-Martin, Amaya; Malhotra, Renu; Bryden, Geoffrey; Rieke, George H.; Su, Kate Y. L.; Beichman, Charles A.; Lawler, Samantha M.

    2010-07-10

    In addition to the Sun, six other stars are known to harbor multiple planets and debris disks: HD 69830, HD 38529, HD 128311, HD 202206, HD 82943, and HR 8799. In this paper, we set constraints on the location of the dust-producing planetesimals around the latter four systems. We use a radiative transfer model to analyze the spectral energy distributions of the dust disks (including two new Spitzer IRS spectra presented in this paper), and a dynamical model to assess the long-term stability of the planetesimals' orbits. As members of a small group of stars that show evidence of harboring a multiple planets and planetesimals, their study can help us learn about the diversity of planetary systems.

  4. Spectroscopic studies of four southern-hemisphere G-K supergiants: HD 192876 (α1 Cap), HD 194215 (HR 7801), HD 206834 (c Cap), and HD 222574 (104 Aqr)

    NASA Astrophysics Data System (ADS)

    Usenko, I. A.; Kniazev, A. Yu.; Berdnikov, L. N.; Kravtsov, V. V.

    2015-11-01

    We have studied the high-resolution spectra taken with the 1.9-m telescope of the South African Astronomical Observatory for four supergiants that are deemed to be nonvariable and to lie beyond the red edge of the Cepheid instability strip (CIS): HD 192876, HD 194215, HD 206834, and HD 222574. The atmospheric parameters, reddenings, luminosities, distances, radii, and chemical composition have been determined for these stars. Based on these results, we have ascertained thatHD194215 is not a mainsequence star but an ordinary supergiant. All objects exhibit a nearly solar metallicity. The abundances of carbon and oxygen in HD 194215 and HD 206834 are nearly solar, while they are underabundant in HD 192876 and HD 222574. The abundances of sodium, magnesium, and aluminum are different for all objects, while those of the remaining elements are nearly solar. For HD 206834, the measured radial velocity exceeds its previously known values by a factor of 3, while the asymmetric knifelike profiles of the Ha and Hß absorption lines suggest the existence of an extended envelope around the star. Similar profiles of hydrogen absorption lines and strong lines of some metals with low lower-level excitation potentials have also been revealed in the spectrum of HD 222574. The positions of the supergiants on the effective temperature-luminosity diagram in comparison with the evolutionary tracks of the stars have shown their masses to lie within the range 3.4-4.3 M ⊙. HD 194215 and HD 206834 have crossed the CIS for the first time, with the latter object being near the stage of transformation into a red supergiant. HD 192876 and HD 222574 have already passed the first dredge-up and probably move from right to left, crossing the CIS for the second time. The position of HD 222574 near the red CIS edge is probably attributable to its Cepheid-like brightness and radial velocity variations.

  5. Improved Log(gf) Values for Lines of Ti I and Abundance Determinations in the Photospheres of the Sun and Metal-Poor Star HD 84937 (Accurate Transition Probabilities for Ti I)

    NASA Astrophysics Data System (ADS)

    Lawler, J. E.; Guzman, A.; Wood, M. P.; Sneden, C.; Cowan, J. J.

    2013-04-01

    New atomic transition probability measurements for 948 lines of Ti I are reported. Branching fractions from Fourier transform spectra and from spectra recorded using a 3 m echelle spectrometer are combined with published radiative lifetimes from laser-induced fluorescence measurements to determine these transition probabilities. Generally good agreement is found in comparisons to the NIST Atomic Spectra Database. The new Ti I data are applied to re-determine the Ti abundance in the photospheres of the Sun and metal-poor star HD 84937 using many lines covering a range of wavelength and excitation potential to explore possible non-local thermal equilibrium effects. The variation of relative Ti/Fe abundance with metallicity in metal-poor stars observed in earlier studies is supported in this study.

  6. IMPROVED log(gf) VALUES FOR LINES OF Ti I AND ABUNDANCE DETERMINATIONS IN THE PHOTOSPHERES OF THE SUN AND METAL-POOR STAR HD 84937 (ACCURATE TRANSITION PROBABILITIES FOR Ti I)

    SciTech Connect

    Lawler, J. E.; Guzman, A.; Wood, M. P.; Sneden, C.; Cowan, J. J. E-mail: adrianaguzman2014@u.northwestern.edu E-mail: chris@verdi.as.utexas.edu

    2013-04-01

    New atomic transition probability measurements for 948 lines of Ti I are reported. Branching fractions from Fourier transform spectra and from spectra recorded using a 3 m echelle spectrometer are combined with published radiative lifetimes from laser-induced fluorescence measurements to determine these transition probabilities. Generally good agreement is found in comparisons to the NIST Atomic Spectra Database. The new Ti I data are applied to re-determine the Ti abundance in the photospheres of the Sun and metal-poor star HD 84937 using many lines covering a range of wavelength and excitation potential to explore possible non-local thermal equilibrium effects. The variation of relative Ti/Fe abundance with metallicity in metal-poor stars observed in earlier studies is supported in this study.

  7. 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

  8. Observations of FK Comae stars

    NASA Technical Reports Server (NTRS)

    Bopp, B. W.

    1981-01-01

    Observations on the FK Comae stars are described. FK Com, UZ Lib and HD 199178 are compared and related as a group of stars. The crucial observational tests of the proposed evolutionary status of these stars are noted.

  9. The Pan-Pacific Planet Search. VI. Giant Planets Orbiting HD 86950 and HD 222076

    NASA Astrophysics Data System (ADS)

    Wittenmyer, Robert A.; Jones, M. I.; Zhao, Jinglin; Marshall, J. P.; Butler, R. P.; Tinney, C. G.; Wang, Liang; Johnson, John Asher

    2017-02-01

    We report the detection of two new planets orbiting the K giants HD 86950 and HD 222076, based on precise radial velocities obtained with three instruments: AAT/UCLES, FEROS, and CHIRON. HD 86950b has a period of 1270 ± 57 days at a=2.72+/- 0.08 au, and m sin i=3.6+/- 0.7 {M}{Jup}. HD 222076b has P=871+/- 19 days at a=1.83+/- 0.03 au, and m sin i=1.56+/- 0.11 {M}{Jup}. These two giant planets are typical of the population of planets known to orbit evolved stars. In addition, we find a high-amplitude periodic velocity signal (K∼ 50 m s‑1) in HD 29399 and show that it is due to stellar variability rather than Keplerian reflex motion. We also investigate the relation between planet occurrence and host-star metallicity for the 164-star Pan-Pacific Planet Search (PPPS) sample of evolved stars. In spite of the small sample of PPPS detections, we confirm the trend of increasing planet occurrence as a function of metallicity found by other studies of planets orbiting evolved stars.

  10. Hubble Space Telescope Observations of the HD 202628 Debris Disk

    NASA Technical Reports Server (NTRS)

    Krist, John E.; Stapelfeldt, Karl R.; Bryden, Geoffrey; Plavchan, Peter

    2012-01-01

    A ring-shaped debris disk around the G2V star HD 202628 (d = 24.4 pc) was imaged in scattered light at visible wavelengths using the coronagraphic mode of the Space Telescope Imaging Spectrograph on the Hubble Space Telescope. The ring is inclined by approx.64deg from face-on, based on the apparent major/minor axis ratio, with the major axis aligned along PA = 130deg. It has inner and outer radii (> 50% maximum surface brightness) of 139 AU and 193 AU in the northwest ansae and 161 AU and 223 AU in the southeast ((Delta)r/r approx. = 0.4). The maximum visible radial extent is approx. 254 AU. With a mean surface brightnesses of V approx. = 24 mag arcsec.(sup -2), this is the faintest debris disk observed to date in reflected light. The center of the ring appears offset from the star by approx.28 AU (deprojected). An ellipse fit to the inner edge has an eccentricity of 0.18 and a = 158 AU. This offset, along with the relatively sharp inner edge of the ring, suggests the influence of a planetary-mass companion. There is a strong similarity with the debris ring around Fomalhaut, though HD 202628 is a more mature star with an estimated age of about 2 Gyr. We also provide surface brightness limits for nine other stars in our study with strong Spitzer excesses around which no debris disks were detected in scattered light (HD 377, HD 7590, HD 38858, HD 45184, HD 73350, HD 135599, HD 145229, HD 187897, and HD 201219).

  11. A gas density drop in the inner 6 AU of the transition disk around the Herbig Ae star HD 139614 . Further evidence for a giant planet inside the disk?

    NASA Astrophysics Data System (ADS)

    Carmona, A.; Thi, W. F.; Kamp, I.; Baruteau, C.; Matter, A.; van den Ancker, M.; Pinte, C.; Kóspál, A.; Audard, M.; Liebhart, A.; Sicilia-Aguilar, A.; Pinilla, P.; Regály, Zs.; Güdel, M.; Henning, Th.; Cieza, L. A.; Baldovin-Saavedra, C.; Meeus, G.; Eiroa, C.

    2017-02-01

    Context. Quantifying the gas surface density inside the dust cavities and gaps of transition disks is important to establish their origin. Aims: We seek to constrain the surface density of warm gas in the inner disk of HD 139614, an accreting 9 Myr Herbig Ae star with a (pre-)transition disk exhibiting a dust gap from 2.3 ± 0.1 to 5.3 ± 0.3 AU. Methods: We observed HD 139614 with ESO/VLT CRIRES and obtained high-resolution (R 90 000) spectra of CO ro-vibrational emission at 4.7 μm. We derived constraints on the disk's structure by modeling the CO isotopolog line-profiles, the spectroastrometric signal, and the rotational diagrams using grids of flat Keplerian disk models. Results: We detected υ = 1 → 0 12CO, 2→1 12CO, 1→0 13CO, 1→0 C18O, and 1→0 C17O ro-vibrational lines. Lines are consistent with disk emission and thermal excitation. 12CO υ = 1 → 0 lines have an average width of 14 km s-1, Tgas of 450 K and an emitting region from 1 to 15 AU. 13CO and C18O lines are on average 70 and 100 K colder, 1 and 4 km s-1 narrower than 12CO υ = 1 → 0, and are dominated by emission at R ≥ 6 AU. The 12CO υ = 1 → 0 composite line-profile indicates that if there is a gap devoid of gas it must have a width narrower than 2 AU. We find that a drop in the gas surface density (δgas) at R < 5-6 AU is required to be able to simultaneously reproduce the line-profiles and rotational diagrams of the three CO isotopologs. Models without a gas density drop generate 13CO and C18O emission lines that are too broad and warm. The value of δgas can range from 10-2 to 10-4 depending on the gas-to-dust ratio of the outer disk. We find that the gas surface density profile at 1 < R < 6 AU is flat or increases with radius. We derive a gas column density at 1 < R < 6 AU of NH = 3 × 1019-1021 cm-2 (7 × 10-5-2.4 × 10-3 g cm-2) assuming NCO = 10-4NH. We find a 5σ upper limit on the CO column density NCO at R ≤ 1 AU of 5 × 1015 cm-2 (NH ≤ 5 × 1019 cm-2). Conclusions

  12. THE DIVERSE ORIGINS OF NEUTRON-CAPTURE ELEMENTS IN THE METAL-POOR STAR HD 94028: POSSIBLE DETECTION OF PRODUCTS OF i-PROCESS NUCLEOSYNTHESIS

    SciTech Connect

    Roederer, Ian U.; Karakas, Amanda I.; Pignatari, Marco; Herwig, Falk E-mail: amanda.karakas@monash.edu E-mail: fherwig@uvic.ca

    2016-04-10

    We present a detailed analysis of the composition and nucleosynthetic origins of the heavy elements in the metal-poor ([Fe/H] = −1.62 ± 0.09) star HD 94028. Previous studies revealed that this star is mildly enhanced in elements produced by the slow neutron-capture process (s process; e.g., [Pb/Fe] = +0.79 ± 0.32) and rapid neutron-capture process (r process; e.g., [Eu/Fe] = +0.22 ± 0.12), including unusually large molybdenum ([Mo/Fe] = +0.97 ± 0.16) and ruthenium ([Ru/Fe] = +0.69 ± 0.17) enhancements. However, this star is not enhanced in carbon ([C/Fe] = −0.06 ± 0.19). We analyze an archival near-ultraviolet spectrum of HD 94028, collected using the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope, and other archival optical spectra collected from ground-based telescopes. We report abundances or upper limits derived from 64 species of 56 elements. We compare these observations with s-process yields from low-metallicity AGB evolution and nucleosynthesis models. No combination of s- and r-process patterns can adequately reproduce the observed abundances, including the super-solar [As/Ge] ratio (+0.99 ± 0.23) and the enhanced [Mo/Fe] and [Ru/Fe] ratios. We can fit these features when including an additional contribution from the intermediate neutron-capture process (i process), which perhaps operated through the ingestion of H in He-burning convective regions in massive stars, super-AGB stars, or low-mass AGB stars. Currently, only the i process appears capable of consistently producing the super-solar [As/Ge] ratios and ratios among neighboring heavy elements found in HD 94028. Other metal-poor stars also show enhanced [As/Ge] ratios, hinting that operation of the i process may have been common in the early Galaxy.

  13. X-Raying the Coronae of HD 155555

    NASA Technical Reports Server (NTRS)

    Lalitha, S.; Singh, K.P.; Drake, S. A.; Kashyap, V.

    2015-01-01

    We present an analysis of the high-resolution Chandra observation of the multiple system, HD 155555 (an RS CVn type binary system, HD 155555 AB, and its spatially resolved low-mass companion HD 155555 C). This is an intriguing system which shows properties of both an active pre-main sequence star and a synchronised (main sequence) binary. We obtain the emission measure distribution, temperature structures, plasma densities, and abundances of this system and compare them with the coronal properties of other young/active stars. HD 155555 AB and HD 155555 C produce copious X-ray emission with log L(sub x) of 30.54 and 29.30, respectively, in the 0.3-6.0 kiloelectronvolt energy band. The light curves of individual stars show variability on timescales of few minutes to hours. We analyse the dispersed spectra and reconstruct the emission measure distribution using spectral line analysis. The resulting elemental abundances exhibit inverse first ionisation potential effect in both cases. An analysis of He-like triplets yields a range of coronal electron densities 1010 - 1013 per cubic centimeter. Since HD 155555 AB is classified both as an RS CVn and a PMS star, we compare our results with those of other slightly older active main-sequence stars and T Tauri stars, which indicates that the coronal properties of HD 155555 AB closely resemble that of an older RS CVn binary rather than a younger PMS star. Our results also suggests that the properties of HD 155555 C is very similar to those of other active M dwarfs.

  14. Sub-Saturn Planetary Candidates of HD 16141 and HD 46375.

    PubMed

    Marcy; Butler; Vogt

    2000-06-10

    Precision Doppler measurements from the Keck High-Resolution Echelle Spectrograph reveal periodic Keplerian velocity variations in the stars HD 16141 and HD 46375. HD 16141 (G5 IV) has a period of 75.8 days and a velocity amplitude of 11 m s-1, yielding a companion having Msini=0.22 M(JUP) and a semimajor axis of a=0.35 AU. HD 46375 (K1 IV-V) has a period of 3.024 days and a velocity amplitude of 35 m s-1, yielding a companion with Msini=0.25 M(JUP), a semimajor axis of a=0.041 AU, and an eccentricity of 0.04 (consistent with zero). These companions contribute to the rising planet mass function toward lower masses.

  15. Six Planets Orbiting HD 219134

    NASA Astrophysics Data System (ADS)

    Vogt, Steven S.; Burt, Jennifer; Meschiari, Stefano; Butler, R. Paul; Henry, Gregory W.; Wang, Songhu; Holden, Brad; Gapp, Cyril; Hanson, Russell; Arriagada, Pamela; Keiser, Sandy; Teske, Johanna; Laughlin, Gregory

    2015-11-01

    We present new, high-precision Doppler radial velocity (RV) data sets for the nearby K3V star HD 219134. The data include 175 velocities obtained with the HIRES Spectrograph at the Keck I Telescope and 101 velocities obtained with the Levy Spectrograph at the Automated Planet Finder Telescope at Lick Observatory. Our observations reveal six new planetary candidates, with orbital periods of P = 3.1, 6.8, 22.8, 46.7, 94.2, and 2247 days, spanning masses of {M}{sin}i=3.8, 3.5, 8.9, 21.3, 10.8, and 108 {{M}}\\oplus , respectively. Our analysis indicates that the outermost signal is unlikely to be an artifact induced by stellar activity. In addition, several years of precision photometry with the T10 0.8 m automatic photometric telescope at Fairborn Observatory demonstrated a lack of brightness variability to a limit of ∼0.0002 mag, providing strong support for planetary-reflex motion as the source of the RV variations. The HD 219134 system with its bright (V = 5.6) primary provides an excellent opportunity to obtain detailed orbital characterization (and potentially follow-up observations) of a planetary system that resembles many of the multiple-planet systems detected by Kepler, which are expected to be detected by NASA’s forthcoming TESS Mission and by ESA’s forthcoming PLATO Mission.

  16. Physical characters of HD 93044

    NASA Astrophysics Data System (ADS)

    Li, Zhiping

    1993-12-01

    The measurements of uvby H beta of HD 93044 were obtained in April 1991, and the observational results that the star locates nearly in the middle of delta Scuti instability strip with somewhat deviation to red edge. According to Crawford (1979) and Philip's (1979) calibrations, the effective temperature, absolute visual magnitude and surface gravity are obtained to be Teff = 7300 +/- 200 K, Mv = 1.33 mag +/- 0.39 and log g = 3.7 +/- 0.15, respectively. The observational results of Delta m1 = 0.01 give an estimate of (Fe/H) = -0.003 +/- 0.18, so the opinion of metallic deficient is not supported obviously. The observations show the reddening index E(b-y) to be 0.014 which is 1.4 times as large as the standard deviation of Crawford's (1979) statistics.

  17. The Disk and Environment of HD 100546

    NASA Technical Reports Server (NTRS)

    Gull, Theodore R.; Fisher, Richard R. (Technical Monitor)

    2000-01-01

    We present coronagraphic imaging of the nearest Herbig Be star with the Space Telescope Imaging Spectrograph on board HST, K-short imaging with ADONIS from the 3.6m telescope at La Silla, and mid-IR imaging with OSCIR using the 4m telescope at Cerro Tololo Inter-American Observatory (CTIO). We confirm the disk detection reported by Pantin et al. The brightest material associated with the disk is located within 3.5 sec (365 AU) of the star, but disk material can be traced to 5 sec. (515 AU) based on the surface brightness distribution. Spiral dark lanes are seen beyond 200 AU. HD 100546 is accompanied by a diffuse envelope which is more highly flared than the disk and which extends 10 sec (1000 AU) from the star. Far from the star, a band of nebulosity running from NNW to SSE is seen, compatible with the orientation of filaments in DC 292.6-7.9. Closer to the star, the bands are bowed out to the W and WSW, in the direction of HD 100546's proper motion. The OSCIR images show that the source is slightly extended at 11.7 microns, but unresolved at 10 and 18 microns. The mid-IR color temperatures are consistent with central clearing of the disk, supporting the inference of Pantin et al. This study is based on observations made with HST, and at ESO.

  18. HOT DEBRIS DUST AROUND HD 106797

    SciTech Connect

    Fujiwara, Hideaki; Onaka, Takashi; Yamashita, Takuya; Ishihara, Daisuke; Kataza, Hirokazu; Ootsubo, Takafumi; Murakami, Hiroshi; Nakagawa, Takao; Hirao, Takanori; Enya, Keigo; Fukagawa, Misato; Marshall, Jonathan P.; White, Glenn J.

    2009-04-10

    Photometry of the A0 V main-sequence star HD 106797 with AKARI and Gemini/T-ReCS is used to detect excess emission over the expected stellar photospheric emission between 10 and 20 {mu}m, which is best attributed to hot circumstellar debris dust surrounding the star. The temperature of the debris dust is derived as T {sub d} {approx} 190 K by assuming that the excess emission is approximated by a single temperature blackbody. The derived temperature suggests that the inner radius of the debris disk is {approx}14 AU. The fractional luminosity of the debris disk is 1000 times brighter than that of our own zodiacal cloud. The existence of such a large amount of hot dust around HD 106797 cannot be accounted for by a simple model of the steady state evolution of a debris disk due to collisions, and it is likely that transient events play a significant role. Our data also show a narrow spectral feature between 11 and 12 {mu}m attributable to crystalline silicates, suggesting that dust heating has occurred during the formation and evolution of the debris disk of HD 106797.

  19. HD 129333: The Sun in its infancy

    NASA Technical Reports Server (NTRS)

    Dorren, J. David; Guinan, Edward F.

    1994-01-01

    HD 129333 is a remarkable young, nearby solar-type G star which offers a unique opportunity of studying the properties of the Sun at a time very shortly after in arrived on the main sequence. Its space motion suggest that it is a member of the Pleiades moving group, with an age of approximately 70 Myr; its lithium abundance is consistent with this. HD 129333 has the highest level of Ca II emission of any G star which is not a member of a close binary. Our observations in 1983 showed it to have low-amplitude (5%) light variations implying a rotation period of about 2.7 days, or about 10 times faster than the Sun. Modeling of the photometric variations on the assumption that they are due to starspots yields a spot temperature about 500 K cooler than the photosphere, and a coverage of about 6% of the stellar surface area. ROSAT observations in 1990 revealed the star to be an X-ray source, with an X-ray luminosity in the 0.2 to 2.4 keV range about 300 times that of the Sun. We have used International Ultraviolet Explorer (IUE) observations in conjuction with ground-based photometry to examine the magnetic activity of this star. The IUE emission-line fluxes reveal a level of chromospheric activity 3 to 20 times greater than the Sun's. The transition-region activity is 20 to 100 times that of the Sun. The activity level of HD 129333 is consistent with the Skumanich law relating activity to age, and with the rotation-activity relation, although it may be near saturation level. This star can yield valuable information about the magnetic dynamo of the young Sun, as well as about stellar dynamos in general. The 1988 IUE observations covered four phases of its rotational cycle. A phase dependence of the Mg II h and k emission flux suggests a close association of chromospheric plages with starspot regions at that time. Systematic variations in the mean brightness of HD 129333 between 1983 and 1993, and in the UV emission fluxes, indicate the presence of an activity cycle of an

  20. The AP spectroscopic binary HD 59435 revisited

    NASA Astrophysics Data System (ADS)

    Wade, G. A.; Mathys, G.; North, P.

    1999-07-01

    HD 59435 is a double-lined spectroscopic binary, one component of which is a magnetic Ap star and the other a G8 or K0 giant (Wade et al. 1996). Both components are very slowly rotating, and the Ap star exhibits spectral lines resolved into their magneti cally-split components. Herein we report additional measurements of the mean magnetic field modulus of the Ap star, measurements of the radial velocities of both components, and Geneva photometry of the system, and discuss their impact upon conclusions drawn previously. Based on observations collected at the European Southern Observatory (La Silla, Chile; ESO Programme Nos. 56.E-0688, 58.E-0159, 60.E-0565). Table 3 is available only in electronic form at the CDS via anonymous ftp 130.79.128.5

  1. ROVIBRATIONAL QUENCHING RATE COEFFICIENTS OF HD IN COLLISIONS WITH He

    SciTech Connect

    Nolte, J. L.; Stancil, P. C.; Lee, T.-G.; Balakrishnan, N.; Forrey, R. C. E-mail: stancil@physast.uga.edu E-mail: naduvala@unlv.nevada.edu

    2012-01-01

    Along with H{sub 2}, HD has been found to play an important role in the cooling of the primordial gas for the formation of the first stars and galaxies. It has also been observed in a variety of cool molecular astrophysical environments. The rate of cooling by HD molecules requires knowledge of collisional rate coefficients with the primary impactors, H, He, and H{sub 2}. To improve knowledge of the collisional properties of HD, we present rate coefficients for the He-HD collision system over a range of collision energies from 10{sup -5} to 5 Multiplication-Sign 10{sup 3} cm{sup -1}. Fully quantum mechanical scattering calculations were performed for initial HD rovibrational states of j = 0 and 1 for v = 0-17 which utilized accurate diatom rovibrational wave functions. Rate coefficients of all {Delta}v = 0, -1, and -2 transitions are reported. Significant discrepancies with previous calculations, which adopted a small basis and harmonic HD wave functions for excited vibrational levels, were found for the highest previously considered vibrational state of v = 3. Applications of the He-HD rate coefficients in various astrophysical environments are briefly discussed.

  2. The active chromosphere binary HD 17433 (VY Arietis)

    NASA Technical Reports Server (NTRS)

    Bopp, Bernard W.; Dempsey, Robert; Saar, Steven H.; Ambruster, Carol; Feldman, Paul

    1989-01-01

    The sixth-magnitude K star HD 17433 (VY Ari) is shown to be an active-chromosphere binary with an orbital period of 13.198 days. A photometric (rotational) period of 17.4 days is indicated by the existing photometry, implying that HD 17433 is not in synchronous rotation. In the optical, H-alpha is seen in emission, with variable profile and intensity; He I lambda-5876 is present in absorption. IUE observations show chromospheric and transition-region emission lines with surface fluxes up to 200 times greater than those observed in the quiet sun. The luminosity and radius are appropriate for a subgiant, and the kinematics suggest Pleiades group membership. The presence of a lithium absorption feature indicates it may either be a young object, possibly a pre-main sequence star or an evolved spotted RS CVn system. Interpretations from the optical measurement of the magnetic field strength of HD 17433 are given.

  3. HD 123335, an interesting eclipsing SB2 in Centaurus

    NASA Astrophysics Data System (ADS)

    Hensberge, H.; Nitschelm, C.; Freyhammer, L. M.; Bouzid, M. Y.; Clausen, J. V.; David, M.; Helt, B. E.; Olsen, E. H.; Papadaki, C.; Sterken, C.; Vaz, L. P. R.

    2004-12-01

    New extensive differential uvby photometry at the Danish SAT telescope, and high-resolution spectroscopy at ESO, SAAO and Mt. John Observatory reveal that HD 123335 (HR 5292) is an eclipsing SB2 consisting of two sharp-lined B-type stars in an eccentric orbit (e = 0.735, Porb = 35.44735 deg). The slowest rotating component (Prot = 61.46 deg) is a chemically peculiar (CP) star of the type He-weak SrTi.

  4. Shadows Cast On The Transition Disk Of Hd 135344B

    NASA Astrophysics Data System (ADS)

    Stolker, Tomas

    2016-07-01

    I will present new VLT/SPHERE polarimetric imaging observations of the transition disk around HD 135344B (SAO 206462) which have revealed multiple shadow features. These shadows are likely cast by a warped inner disk component and possibly an accretion funnel flow from the inner disk onto the star which might explain the variability of one shadow.

  5. The highly varying circumstellar debris disk of HD 183324

    NASA Astrophysics Data System (ADS)

    Welsh, Barry; Montgomery, Sharon Lynn

    2017-01-01

    The 140 Myr-old A0IV-type star HD 183324 possesses many of the same physical characteristics as the stars Beta Pictoris and 49 Ceti, whose circumstellar gas and dust disks are the two best-studied debris disk systems. Here, we compare spectral observations of HD 183324 collected (and archived) in 2009 and 2010 to similarly high-resolution spectral observations of HD 183324 that we collected in 2013. An inspection of these spectra (recorded at visible wavelengths) reveals a remarkably high level of variable circumstellar absorption activity around the star. Such behavior is typical of a stellar system in which gas and dust is being sporadically added to a circumstellar disk due to the evaporation of planetesimal-like objects (“exocomets”) as they fall towards the central star. We present spectral data that show levels of absorption variability of greater than 100% in both the circumstellar CaII-K (3933Å) and FeI (3860Å) line profiles as measured throughout the 5-year period of observations. Such high levels of circumstellar absorption variability may be indicative of an as-yet undetected exoplanet, whose gravitational forces are perturbing the planetesimals orbiting HD 183324.

  6. Light variations of the population II F-type supergiant HD 46703

    NASA Technical Reports Server (NTRS)

    Bond, H. E.; Carney, B. W.; Grauer, A. D.

    1984-01-01

    Photometric monitoring has revealed brightness variations of 0.1 m on a time scale of weeks for HD 46703, a metal-deficient F-type field analog of the stars lying above the horizontal branch in globular clusters. It is suggested that HD 46703 belongs to the '89 Her' class of luminous F-type variables. Since HD 46703 is unquestionably a halo object, it is almost certainly a low-mass star. It is suggested that it, and probably the other 89 Her variables, are masquerading as supergiants during their final evolution off the asymptotic giant branch.

  7. Physics of Cool Stars: Densities, Sizes, and Energetics

    NASA Technical Reports Server (NTRS)

    Dupree, Andrea K.

    2001-01-01

    The ORFEUS 1 (Orbiting and Retrievable Far and Extreme Ultraviolet Spectrometer) telescope obtained far ultraviolet spectra (lambda-lambda 912-1218) of luminous cool stars as a part of our observing program. Two classes of objects were measured: luminous single stars beta Dra (HD 159181) and two hybrid stars alpha Aqr (HD 209750) and alpha TrA (HD 150798) and two active binary systems: 44i Boo and UX Ari.

  8. Pulsations in the atmosphere of the rapidly oscillating Ap star 10Aquilae

    NASA Astrophysics Data System (ADS)

    Sachkov, M.; Kochukhov, O.; Ryabchikova, T.; Huber, D.; Leone, F.; Bagnulo, S.; Weiss, W. W.

    2008-09-01

    The rapidly oscillating Ap (roAp) star 10Aquilae (10Aql) shows one of the lowest photometric pulsation amplitudes and is characterized by an unusual spectroscopic pulsational behaviour compared to other roAp stars. In summer 2006 this star became target of an intense observing campaign, that combined ground-based spectroscopy with space photometry obtained with the MOST (Microvariability & Oscillations Stars) satellite. More than 1000 spectra were taken during seven nights over a time-span of 21d with high-resolution spectrographs at the 8-m European Southern Observatory (ESO) Very Large Telescope (VLT) and 3.6-m Telescopio Nazionale Galileo (TNG) giving access to radial velocity variations of about 150 lines from different chemical species. A comparison of pulsation signatures in lines formed at different atmospheric heights allowed us to resolve the vertical structure of individual pulsation modes in 10Aql which is the first time for a multiperiodic roAp star. Taking advantage of the clear oscillation patterns seen in a number of rare earth ions and using the contemporaneous MOST photometry to resolve aliasing in the radial velocity measurements, we improve also the determination of pulsation frequencies. The inferred propagation of pulsation waves in 10Aql is qualitatively similar to other roAp stars: pulsation amplitudes become measurable in the layers where Y and Eu are concentrated, increase in layers where the Hα core is formed, reach a maximum of 200-300ms-1 in the layers probed by Ce, Sm, Dy lines and then decrease to 20-50ms-1 in the layers where NdIII and PrIII lines are formed. A unique pulsation feature of 10Aql is a second pulsation maximum indicated by TbIII lines which form in the uppermost atmospheric layers and oscillate with amplitudes of up to 350ms-1. The dramatic decline of pulsations in the atmospheric layers probed by the strong PrIII and NdIII lines accounts for the apparent peculiarity of 10Aql when compared to other roAp stars. The phase

  9. Ultraviolet spectral synthesis of HD 72660

    NASA Astrophysics Data System (ADS)

    Golriz, S. S.; Landstreet, J. D.

    2016-03-01

    The study of chemical abundances in stellar atmosphere provides a useful tool to investigate the formation and evolution history of stars. The optical wavelength range has been used almost exclusively in the past to determine the elemental abundance in A-type stars. We use high-resolution, high signal-to-noise ultraviolet spectra obtained from the STIS/NUV-MAMA instrument on board Hubble Space Telescope. The spectra available cover the wavelength ranges 1630 Å-1901 Å and 2130 Å-2887 Å. The main challenge to carrying out abundance analysis in the ultraviolet is the extreme level of line blending. Abundance analysis using single isolated spectral lines is almost completely impossible; it is necessary to model spectral windows using spectrum synthesis with fairly complete line-lists. We have used the LTE spectrum synthesis code ZEEMAN to model the UV spectrum of HD 72660, adjusting abundances for a best match for elements with 6 ≤ Z≤ 82 for which lines are present in the Vinna Atomic Line Database line-list. Abundances or upper limits are derived for 32 elements. We find that except a few, our derived abundances are slightly higher than solar values. We estimate upper limits for abundances of eleven elements and abundance values of 12 elements which have not been detected in the optical. The high abundances that we find for some heavy elements may point to radiative levitation. The presence of lanthanides plus our results, suggest the reclassification of HD 72660 as a transition object between an HgMn star and an Am star.

  10. The Unseen Companion of HD 114762

    NASA Astrophysics Data System (ADS)

    Latham, David W.

    2014-01-01

    I have told the story of the discovery of the unseen companion of HD114762 (Latham et al. 1989, Nature, 389, 38-40) in a recent publication (Latham 2012, New Astronomy Reviews 56, 16-18). The discovery was enabled by a happy combination of some thinking outside the box by Tsevi Mazeh at Tel Aviv University and the development of new technology for measuring stellar spectra at the Harvard-Smithsonian Center for Astrophysics. Tsevi's unconventional idea was that giant exoplanets might be found much closer to their host stars than Jupiter and Saturn are to the Sun, well inside the snow line. Our instrument was a high-resolution echelle spectrograph optimized for measuring radial velocities of stars similar to the Sun. The key technological developments were an intensified Reticon photon-counting detector under computer control combined with sophisticated analysis of the digital spectra. The detector signal-processing electronics eliminated persistence, which had plagued other intensified systems. This allowed bright Th-Ar calibration exposures before and after every stellar observation, which in turn enabled careful correction for spectrograph drifts. We built three of these systems for telescopes in Massachusetts and Arizona and christened them the "CfA Digital Speedometers". The discovery of HD 114762-b was serendipitous, but not accidental.

  11. Analysis of the Chemical Composition of the Atmospheres of Stars with Debris Disks and Planetary Systems

    NASA Astrophysics Data System (ADS)

    Rojas, M.; Drake, N. A.; Chavero, C.; Pereira, C. B.; Kholtygin, A. F.; Solovyov, D. I.

    2013-12-01

    Spectroscopic studies of seven low mass stars in spectral classes F, G, and K are presented. Four of these (HD 1581, HD 10700, HD 17925, and HD 22484) have debris disks and for two of them (HD 22049 and HD 222582(A + B)) planets are observed. Neither a debris disk nor planets have been observed for one the program stars (HD 20766). High resolution spectral observations of the program stars were made at the 2.2-m telescope of the European Southern Observatory (ESO) during 2008 with the FEROS spectrograph (R = 48000, spectral range 3800-9200 Å). The fundamental parameters of the stars are determined, including effective temperature, acceleration of gravity at the stars' surface, microturbulence velocity, metallicity, and the abundances of volatile and refractory elements in their atmospheres. The positions of all these stars are indicated on a Hertzsprung-Russell diagram.

  12. Chemical abundances for A-and F-type supergiant stars

    NASA Astrophysics Data System (ADS)

    Molina, R. E.; Rivera, H.

    2016-10-01

    We present the stellar parameters and elemental abundances of a set of A-F-type supergiant stars HD 45674, HD 180028, HD 194951 and HD 224893 using high resolution (R≈ 42,000) spectra taken from ELODIE library. We present the first results of the abundance analysis for HD 45674 and HD 224893. We reaffirm the abundances for HD 180028 and HD 194951 studied previously by Luck. Alpha-elements indicate that the objects belong to the thin disc population. Their abundances and their location on the Hertzsprung-Russell diagram seem to indicate that HD 45675, HD 194951 and HD 224893 are in the post-first dredge-up (post-1DUP) phase, and that they are moving in the red-blue loop region. HD 180028, on the contary, shows typical abundances of Population I, but its evolutionary status cannot be satisfactorily defined.

  13. Period04 FCAPT uvby Photometric Studies of Eight Magnetic CP Stars

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Dukes, Robert J.

    2014-06-01

    We present Four College Automated Photometric Telescope (FCAPT) differential Stromgren uvby photometry of 8 magnetic CP (mCP) stars: HD 5797 (V551 Cas), HD 26792 (DH Cam), HD 27309 (56 Tau, V724 Tau), HD 49713 (V740 Mon), HD 74521 (49 Cnc, BI Cnc), HD 120198 (84 UMa, CR UMa), HD 171263 (QU Ser), and HD 215441 (GL Lac, Babcock's star). Our data sets are larger than those of most mCP stars in the literature. These are the first FCAPT observations of HD 5797, HD 26792, HD 49713, and HD 171263. Those for the remaining four stars substantially extend published FCAPT data. The FCAPT observed some stars for a longer time range and with greater accuracy than other optical region automated photometric telescopes.Our goals were to determine very accurate periods, the u, v, b, and y amplitudes, and if there were any long period periods. In addition we wanted to compare our results with those of magnetic field measurements to help interpret the light curves.We used the Period04 computer program to analyze the light curves. This program provides errors for the derived quantities as it fits the light curve. Our derived periods of 68.046 +/- 0.008 days for HD 5797, 3.80205 +/- 0.00006 days for HD 26792, 1.56889 +/- 0.000002 days for HD 27309, 2.13536 +/- 0.00002 days for HD 49713, 7.0505 +/- 0.0001 days for HD 74521, 1.38577 +/- 0.000004 days for HD 120198, 3.9974 +/- 0.0001days for HD 171263, and 9.487792 +/- 0.00005 days for HD 215441 are refinements of the best determinations in the literature.

  14. MULTIWAVELENGTH OBSERVATIONS OF THE RUNAWAY BINARY HD 15137

    SciTech Connect

    McSwain, M. Virginia; Aragona, Christina; Marsh, Amber N.; Roettenbacher, Rachael M.; De Becker, Michael; Roberts, Mallory S. E.; Boyajian, Tabetha S.; Gies, Douglas R.; Grundstrom, Erika D. E-mail: cha206@lehigh.edu E-mail: rmr207@lehigh.edu E-mail: malloryr@gmail.com E-mail: gies@chara.gsu.edu

    2010-03-15

    HD 15137 is an intriguing runaway O-type binary system that offers a rare opportunity to explore the mechanism by which it was ejected from the open cluster of its birth. Here, we present recent blue optical spectra of HD 15137 and derive a new orbital solution for the spectroscopic binary and physical parameters of the O star primary. We also present the first XMM-Newton observations of the system. Fits of the EPIC spectra indicate soft, thermal X-ray emission consistent with an isolated O star. Upper limits on the undetected hard X-ray emission place limits on the emission from a proposed compact companion in the system, and we rule out a quiescent neutron star (NS) in the propeller regime or a weakly accreting NS. An unevolved secondary companion is also not detected in our optical spectra of the binary, and it is difficult to conclude that a gravitational interaction could have ejected this runaway binary with a low mass optical star. HD 15137 may contain an elusive NS in the ejector regime or a quiescent black hole with conditions unfavorable for accretion at the time of our observations.

  15. HD 47147 - A small-amplitude extreme metal-poor RRab pulsating variable

    NASA Astrophysics Data System (ADS)

    Grenon, M.; Waelkens, C.

    1986-01-01

    The photometric variations and physical and kinematical properties of HD 47147, a ninth magnitude metal-deficient star, are discussed. The long period (0.79732 days), the small amplitude (0.17 mag in the visual band), and the mean effective temperature of 6160 K of this RR Lyrae pulsating variable can be understood by its location near the red edge of the instability strip. The extreme Population II characteristics of HD 47147 are confirmed by its kinematical properties. The temperature and the relatively high luminosity derived are consistent with both possibilities that HD 47147 is a red horizontal branch star or that it is a suprahorizontal branch star actually evolving redward toward the asymptotic branch. Its low amplitude suggests the possibility that the red edge of the instability strip corresponds to a smooth transition from variable to non-variable stars.

  16. The Spectroscopic Orbits of Five γ Doradus Stars

    NASA Astrophysics Data System (ADS)

    Fekel, Francis C.; Henry, Gregory W.; Pourbaix, Dimitri

    2016-02-01

    We have determined the spectroscopic orbits of five γ Dor variables, HD 776, HD 6568, HD 17310, HD 19684, and HD 62196. Their orbital periods range from 27.8 to 1163 days and their eccentricities from 0.01 to 0.65. Of the five systems, only HD 19684 shows lines of its binary companion, but those lines are always so weak and blended with the lines of the primary that we were unable to measure them satisfactorily. The velocity residuals of the orbital fits were searched for periodicities associated with pulsation. No clear, convincing case for velocity periodicities in the residuals was found in four of the five stars. However, for HD 17310 we identified a period of 2.13434 days, a value in agreement with the largest amplitude period previously found photometrically for that star. The velocity residuals of HD 62196 have a long-term trend suggesting that it is a triple system.

  17. Radio detection of the young binary HD 160934

    NASA Astrophysics Data System (ADS)

    Azulay, R.; Guirado, J. C.; Marcaide, J. M.; Martí-Vidal, I.; Arroyo-Torres, B.

    2014-01-01

    Context. Precise determination of dynamical masses of pre-main-sequence (PMS) stars is essential to calibrate stellar evolution models that are widely used to derive theoretical masses of young low-mass objects. Binary stars in young, nearby loose associations are particularly good candidates for this calibration since all members share a common age. Interestingly, some of these young binaries present a persistent and compact radio emission, which makes them excellent targets for astrometric VLBI studies. Aims: We aim to monitor the orbital motion of the binary system HD 160934, a member of the AB Doradus moving group. Methods: We observed HD 160934 with the Very Large Array and the European VLBI Network at 8.4 and 5 GHz, respectively. The orbital information derived from these observations was analyzed along with previously reported orbital measurements. Results: We show that the two components of the binary, HD 160934 A and HD 160934 c, display compact radio emission at VLBI scales, providing precise information on the relative orbit. Revised orbital elements were estimated. Conclusions: Future VLBI monitoring of this pair should determine precise model-independent mass estimates for the A and c components, which will serve as calibration tests for PMS evolutionary models.

  18. The Physical Properties of HD 3651B: An Extrasolar Nemesis?

    NASA Astrophysics Data System (ADS)

    Burgasser, Adam J.

    2007-03-01

    I present detailed analysis of the near-infrared spectrum of HD 3651B, a faint, comoving wide companion to the nearby planet-hosting star HD 3651. These data confirm the companion as a brown dwarf with spectral type T8, consistent with the analysis of Luhman et al. Application of the semi-empirical technique of Burgasser, Burrows, & Kirkpatrick indicates that HD 3651B has Teff=790+/-30 K and logg=5.0+/-0.3 for a metallicity of [M/H]=0.12+/-0.04, consistent with a mass M=0.033+/-0.013 Msolar and an age of 0.7-4.7 Gyr. The surface gravity, mass, and age estimates of this source are all highly sensitive to the assumed metallicity; however, a supersolar metallicity is deduced by direct comparison of spectral models to the observed absolute fluxes. The age of HD 3651B is somewhat better constrained than that of the primary, with estimates for the latter ranging over ~2 Gyr to >12 Gyr. As a widely orbiting massive object to a known planetary system that could potentially harbor terrestrial planets in its habitable zone, HD 3651B may play the role of Nemesis in this system.

  19. GMRT search for 150 MHz radio emission from the transiting extrasolar planets HD 189733 b and HD 209458 b

    NASA Astrophysics Data System (ADS)

    Lecavelier Des Etangs, A.; Sirothia, S. K.; Gopal-Krishna; Zarka, P.

    2011-09-01

    We report a sensitive search for meter-wavelength emission at 150 MHz from two prominent transiting extrasolar planets, HD 189733 b and HD 209458 b. To distinguish any planetary emission from possible stellar or background contributions, we monitored these systems just prior to, during, and after the planet's eclipse behind the host star. No emission was detected from HD 209458 b with a 3σ upper limit of 3.6 mJy. For HD 189733 b we obtain a 3σ upper limit of 2.1 mJy and a marginal 2.7σ detection of ~1900 ± 700 μJy from a direction just 13″ from the star's coordinates (i.e., within the beam), but its association with the planet remains unconfirmed. Thus, the present GMRT observations provide unprecedentedly tight upper limits for meter wavelength emissions from these nearest two transiting-type exoplanets. We point out possible explanations of the non-detections and briefly discuss the resulting constraints on these systems. Data for this observations can be retrieved electronically on the GMRT archive server http://ncra.tifr.res.in/~gmrtarchive and upon request to archive@gmrt.ncra.tifr.res.in.

  20. Planet host stars in open clusters

    NASA Astrophysics Data System (ADS)

    Yang, XiaoLing; Chen, YuQin; Zhao, Gang

    2015-03-01

    We have compiled a list of all planet host star candidates reported in the literature, which are likely to be cluster members, and we checked their memberships by the spatial location, radial velocity, proper motion and photometric criteria. We found that only six stars, BD-13 2130, HD 28305, Kepler-66, Kepler-67, Pr0201 and Pr0211, are planet orbiting stars in open clusters to date. Two stars, HD 70573 and HD 89744, belong to moving groups and one star, TYC 8975-2606-1, may not be a planet host star, while three stars, HD 16175, HD 46375 and HD 108874 are not members of open clusters. We note that all these six planetary systems in the stellar cluster environment are younger than ˜1 Gyr, which might indicate that the planetary system in open cluster can not survive for a long time, and we speculate that close stellar encounters between member stars in open cluster can potentially destroy, or at least strongly affect, the presence of planetary systems.

  1. B- and A-Type Stars in the Taurus-Auriga Star-Forming Region

    NASA Technical Reports Server (NTRS)

    Mooley, Kunal; Hillenbrand, Lynne; Rebull, Luisa; Padgett, Deborah; Knapp, Gillian

    2013-01-01

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud, (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey, and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), t Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.

  2. B- AND A-TYPE STARS IN THE TAURUS-AURIGA STAR-FORMING REGION

    SciTech Connect

    Mooley, Kunal; Hillenbrand, Lynne; Rebull, Luisa; Padgett, Deborah; Knapp, Gillian

    2013-07-10

    We describe the results of a search for early-type stars associated with the Taurus-Auriga molecular cloud complex, a diffuse nearby star-forming region noted as lacking young stars of intermediate and high mass. We investigate several sets of possible O, B, and early A spectral class members. The first is a group of stars for which mid-infrared images show bright nebulae, all of which can be associated with stars of spectral-type B. The second group consists of early-type stars compiled from (1) literature listings in SIMBAD, (2) B stars with infrared excesses selected from the Spitzer Space Telescope survey of the Taurus cloud, (3) magnitude- and color-selected point sources from the Two Micron All Sky Survey, and (4) spectroscopically identified early-type stars from the Sloan Digital Sky Survey coverage of the Taurus region. We evaluated stars for membership in the Taurus-Auriga star formation region based on criteria involving: spectroscopic and parallactic distances, proper motions and radial velocities, and infrared excesses or line emission indicative of stellar youth. For selected objects, we also model the scattered and emitted radiation from reflection nebulosity and compare the results with the observed spectral energy distributions to further test the plausibility of physical association of the B stars with the Taurus cloud. This investigation newly identifies as probable Taurus members three B-type stars: HR 1445 (HD 28929), {tau} Tau (HD 29763), 72 Tau (HD 28149), and two A-type stars: HD 31305 and HD 26212, thus doubling the number of stars A5 or earlier associated with the Taurus clouds. Several additional early-type sources including HD 29659 and HD 283815 meet some, but not all, of the membership criteria and therefore are plausible, though not secure, members.

  3. Highly ionized atoms toward HD 93521

    NASA Technical Reports Server (NTRS)

    Spitzer, Lyman, Jr.; Fitzpatrick, Edward L.

    1992-01-01

    Results are reported from the HST High Resolution Spectrograph observations of absorption features of C IV and Si IV in the spectrum of the high-latitude O star HD 93521 (l = 183 deg; b = 62 deg). A comparison of Si IV and C IV profiles showed that the FWHM of both features is about 50 km/sec, in contrast to the 7 km/sec found for one of the several S II features. The line centers for C IV and Si IV are at v = -67 km/sec and -60 km/sec, respectively. As the interval velocity decreases from 90 to 50 km/sec, the Si IV/C IV ratio of the column density per unit velocity interval increases from about 0.2 to 0.4. The result is qualitatively consistent with a fountain model of Shapiro and Benjamin (1991) if the slower gas has cooled and recombined more than the faster gas.

  4. Recent results on the hierarchical triple system HD 150136

    NASA Astrophysics Data System (ADS)

    Gosset, E.; Berger, J. P.; Absil, O.; Le Bouquin, J. B.; Sana, H.; Mahy, L.; De Becker, M.

    2013-06-01

    HD 150136 is a hierarchical triple system, non-thermal radio emitter, made of three O stars totalling some 130 solar masses. The 2.67-day inner orbit is rather well-known. Recent works derived a good approximation for the outer orbit with a period of 3000 days. We report here on interferometric observations that allow us to angularly resolve the outer orbit. First evidences for an astrometric displacement are given. The determination of the outer system orbit gives access to the inclinations of the systems and to the masses, including the one of the O3-O3.5 primary star.

  5. VizieR Online Data Catalog: Radial velocity data of HD 59686 A (Ortiz+, 2016)

    NASA Astrophysics Data System (ADS)

    Ortiz, M.; Reffert, S.; Trifonov, T.; Quirrenbach, A.; Mitchell, D. S.; Nowak, G.; Buenzli, E.; Zimmerman, N.; Bonnefoy, M.; Skemer, A.; Defrere, D.; Lee, M. H.; Fischer, D. A.; Hinz, P. M.

    2016-08-01

    Precise radial velocities of the giant star HD 59686 A are presented. The observations were taken with the Hamilton spectrograph at the Lick Observatory. The data were acquired and reduced using the iodine cell approach. In total, we have 88 RV measurements for HD 59686 A spanning a period of time of around 12 years. Typical exposure times were 20-min, and the signal-to-noise ratios for these observations are about 120-150. (1 data file).

  6. Chromospherically active stars. 6: Giants with compact hot companions and the barium star scenario

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Henry, Gregory W.; Busby, Michael R.; Eitter, Joseph J.

    1993-01-01

    We have determined spectroscopic orbits for three chromospherically active giants that have hot compact companions. They are HD 160538 (K0 III + wd, P = 904 days), HD 165141 (G8 III + wd, P approximately 5200 days), and HD 185510 (K0 III + sdB, P = 20.6619 days). By fitting an IUE spectrum with theoretical models, we find the white dwarf companion of HD 165141 has a temperature of about 35000 K. Spectral types and rotational velocities have been determined for the three giants and distances have been estimated. These three systems and 39 Ceti are compared with the barium star mass-transfer scenario. The long-period mild barium giant HD 165141 as well as HD 185510 and 39 Ceti, which have relatively short periods and normal abundance giants, appear to be consistent with this scenario. The last binary, HD 160538, a system with apparently near solar abundances, a white dwarf companion, and orbital characteristics similar to many barium stars, demonstrates that the existence of a white-dwarf companion is insufficient to produce a barium star. The paucity of systems with confirmed white-dwarf companions makes abundance analyses of HD 160538 and HD 165141 of great value in examining the role of metallicity in barium star formation.

  7. Chromospherically active stars. 11: Giant with compact hot companions and the barium star scenario

    NASA Technical Reports Server (NTRS)

    Fekel, Francis C.; Henry, Gregory W.; Busby, Michael R.; Eitter, Joseph J.

    1993-01-01

    We have determined spectroscopic orbits for three chromsopherically active giants that have hot compact companions. They are HD 160538 (KO III + wd, P = 904 days), HD 165141 (G8 III + wd, P approximately 5200 days), and HD 185510 (KO III + sdB, P = 20.6619 days). By fitting an IUE spectrum with theoretical models, we find the white dwarf companion of HD 165141 has a temperature of about 35,000 K. Spectral types and rotational velocities have been determined for the three giants and distances have been estimated. These three systems and 39 Ceti are compared with the barium star mass-transfer scenario. The long-period mild barium giant HD 165141 as well as HD 185510 and 39 Ceti, which have relatively short periods and normal abundance giants, appear to be consistent with this scenario. The last binary, HD 160538, a system with apparently near solar abundances, a white dwarf companion, and orbital characteristics similar to many barium stars, demonstrates that the existence of a white dwarf companion is insufficient to produce a barium star. The paucity of systems with confirmed white dwarf companions makes abundance analyses of HD 160538 and HD 165141 of great value in examining the role of metallicity in barium star formation.

  8. A NEW INVESTIGATION OF THE BINARY HD 48099

    SciTech Connect

    Mahy, L.; Rauw, G.; Naze, Y.; Gosset, E.; De Becker, M.; Martins, F.; Sana, H.; Eenens, P.

    2010-01-10

    With an orbital period of about 3.078 days, the double-lined spectroscopic binary HD 48099 is, until now, the only short-period O+O system known in the Mon OB2 association. Even though an orbital solution has already been derived for this system, few information are available about the individual stars. We present, in this paper, the results of a long-term spectroscopic campaign. We derive a new orbital solution and apply a disentangling method to recover the mean spectrum of each star. To improve our knowledge concerning both components, we determine their spectral classifications and their projected rotational velocities. We also constrain the main stellar parameters of both stars by using the CMFGEN atmosphere code and provide the wind properties for the primary star through the study of International Ultraviolet Explorer spectra. This investigation reveals that HD 48099 is an O5.5 V ((f)) + O9 V binary with M{sub 1}sin{sup 3} i = 0.70 M{sub sun} and M{sub 2}sin{sup 3} i = 0.39 M{sub sun}, implying a rather low orbital inclination. This result, combined with both a large effective temperature and log g, suggests that the primary star (vsin i approx = 91 km s{sup -1}) is actually a fast rotator with a strongly clumped wind and a nitrogen abundance of about 8 times the solar value.

  9. The HARPS search for Earth-like planets in the habitable zone. I. Very low-mass planets around HD 20794, HD 85512, and HD 192310

    NASA Astrophysics Data System (ADS)

    Pepe, F.; Lovis, C.; Ségransan, D.; Benz, W.; Bouchy, F.; Dumusque, X.; Mayor, M.; Queloz, D.; Santos, N. C.; Udry, S.

    2011-10-01

    Context. In 2009 we started an intense radial-velocity monitoring of a few nearby, slowly-rotating and quiet solar-type stars within the dedicated HARPS-Upgrade GTO program. Aims: The goal of this campaign is to gather very-precise radial-velocity data with high cadence and continuity to detect tiny signatures of very-low-mass stars that are potentially present in the habitable zone of their parent stars. Methods: Ten stars were selected among the most stable stars of the original HARPS high-precision program that are uniformly spread in hour angle, such that three to four of them are observable at any time of the year. For each star we recorded 50 data points spread over the observing season. The data points consist of three nightly observations with a total integration time of 10 min each and are separated by two hours. This is an observational strategy adopted to minimize stellar pulsation and granulation noise. Results: We present the first results of this ambitious program. The radial-velocity data and the orbital parameters of five new and one confirmed low-mass planets around the stars HD 20794, HD 85512, and HD 192310 are reported and discussed, among which is a system of three super-Earths and one that harbors a 3.6 M⊕-planet at the inner edge of the habitable zone. Conclusions: This result already confirms previous indications that low-mass planets seem to be very frequent around solar-type stars and that this may occur with a frequency higher than 30%. Based on observations made with the HARPS instrument on ESO's 3.6 m telescope at the La Silla Observatory in the frame of the HARPS-Upgrade GTO program ID 086.C-0230.Tables 7-9 (RV data) 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/534/A58

  10. SUBSTELLAR-MASS COMPANIONS TO THE K-GIANTS HD 240237, BD +48 738, AND HD 96127

    SciTech Connect

    Gettel, S.; Wolszczan, A.; Niedzielski, A.; Nowak, G.; Adamow, M.; Zielinski, P.; Maciejewski, G. E-mail: alex@astro.psu.edu

    2012-01-20

    We present the discovery of substellar-mass companions to three giant stars by the ongoing Penn State-Torun Planet Search conducted with the 9.2 m Hobby-Eberly Telescope. The most massive of the three stars, K2-giant HD 240237, has a 5.3 M{sub J} minimum mass companion orbiting the star at a 746 day period. The K0-giant BD +48 738 is orbited by a {>=}0.91 M{sub J} planet which has a period of 393 days and shows a nonlinear, long-term radial velocity (RV) trend that indicates a presence of another, more distant companion, which may have a substellar mass or be a low-mass star. The K2-giant HD 96127 has a {>=}4.0 M{sub J} mass companion in a 647 day orbit around the star. The two K2-giants exhibit a significant RV noise that complicates the detection of low-amplitude, periodic variations in the data. If the noise component of the observed RV variations is due to solar-type oscillations, we show, using all the published data for the substellar companions to giants, that its amplitude is anti-correlated with stellar metallicity.

  11. REPRODUCING THE OBSERVED ABUNDANCES IN RCB AND HdC STARS WITH POST-DOUBLE-DEGENERATE MERGER MODELS-CONSTRAINTS ON MERGER AND POST-MERGER SIMULATIONS AND PHYSICS PROCESSES

    SciTech Connect

    Menon, Athira; Herwig, Falk; Denissenkov, Pavel A.; Clayton, Geoffrey C.; Staff, Jan; Pignatari, Marco; Paxton, Bill

    2013-07-20

    The R Coronae Borealis (RCB) stars are hydrogen-deficient, variable stars that are most likely the result of He-CO WD mergers. They display extremely low oxygen isotopic ratios, {sup 16}O/{sup 18}O {approx_equal} 1-10, {sup 12}C/{sup 13}C {>=} 100, and enhancements up to 2.6 dex in F and in s-process elements from Zn to La, compared to solar. These abundances provide stringent constraints on the physical processes during and after the double-degenerate merger. As shown previously, O-isotopic ratios observed in RCB stars cannot result from the dynamic double-degenerate merger phase, and we now investigate the role of the long-term one-dimensional spherical post-merger evolution and nucleosynthesis based on realistic hydrodynamic merger progenitor models. We adopt a model for extra envelope mixing to represent processes driven by rotation originating in the dynamical merger. Comprehensive nucleosynthesis post-processing simulations for these stellar evolution models reproduce, for the first time, the full range of the observed abundances for almost all the elements measured in RCB stars: {sup 16}O/{sup 18}O ratios between 9 and 15, C-isotopic ratios above 100, and {approx}1.4-2.35 dex F enhancements, along with enrichments in s-process elements. The nucleosynthesis processes in our models constrain the length and temperature in the dynamic merger shell-of-fire feature as well as the envelope mixing in the post-merger phase. s-process elements originate either in the shell-of-fire merger feature or during the post-merger evolution, but the contribution from the asymptotic giant branch progenitors is negligible. The post-merger envelope mixing must eventually cease {approx}10{sup 6} yr after the dynamic merger phase before the star enters the RCB phase.

  12. STUDIES OF THE DIFFUSE INTERSTELLAR BANDS. III. HD 183143

    SciTech Connect

    Hobbs, L. M.; Thorburn, J. A.; York, D. G.; Bishof, M.; Oka, T.; Snow, T. P.; Friedman, S. D.; McCall, B. J.; Rachford, B.; Sonnentrucker, P.; Welty, D. E.

    2009-11-01

    Echelle spectra of HD 183143 [B7Iae, E(B - V) = 1.27] were obtained on three nights, at a resolving power R = 38,000 and with a signal-to-noise ratio approx 1000 at 6400 A in the final, combined spectrum. A catalog is presented of 414 diffuse interstellar bands (DIBs) measured between 3900 and 8100 A in this spectrum. The central wavelengths, the widths (FWHM), and the equivalent widths of nearly all of the bands are tabulated, along with the minimum uncertainties in the latter. Among the 414 bands, 135 (or 33%) were not reported in four previous, modern surveys of the DIBs in the spectra of various stars, including HD 183143. The principal result of this study is that the great majority of the bands in the catalog are very weak and fairly narrow. Typical equivalent widths amount to a few mA, and the bandwidths (FWHM) are most often near 0.7 A. No preferred wavenumber spacings among the 414 bands are identified which could provide clues to the identities of the large molecules thought to cause the DIBs. At generally comparable detection limits in both spectra, the population of DIBs observed toward HD 183143 is systematically redder, broader, and stronger than that seen toward HD 204827 (Paper II). In addition, interstellar lines of C{sub 2} molecules have not been detected toward HD 183143, while a very high value of N(C{sub 2})/E(B - V) is observed toward HD 204827. Therefore, either the abundances of the large molecules presumed to give rise to the DIBs, or the physical conditions in the absorbing clouds, or both, must differ significantly between the two cases.

  13. Stars of type MS with evidence of white dwarf companions. [IUE, Main Sequence (MS)

    NASA Technical Reports Server (NTRS)

    Peery, Benjamin F., Jr.

    1986-01-01

    A search for white dwarf companions of MS-type stars was conducted, using IUE. The overendowments of these stars in typical S-process nuclides suggest that they, like the Ba II stars, may owe their peculiar compositions to earlier mass transfer. Short-wavelength IUE spectra show striking emission line variability in HD35155, HD61913, and 4 Ori; HD35155 and 4 Ori show evidence of white dwarf companions.

  14. A Semi-automated Abundance Survey of Ap Stars

    NASA Astrophysics Data System (ADS)

    Hall, Martin P.; Kurtz, Don; Elkin, Vladimir; Bruntt, Hans

    2015-08-01

    We have carried out an abundance analysis on the high-resolution spectra of approximately 350 Ap stars collected between 2007 and 2010 on the FEROS Echelle (Fibre-led, Extended Range, Echelle ) spectrograph housed at the 2.2-m telescope at European Southern Observatory at La Silla, Chile. We employed the VWA package (vsin I, wavelength shift, abundance analysis) for preliminary selection of spectral lines, and a semi-automated set of routines which we developed in the programming language IDL, to calculate the equivalent widths and abundances of ions of Iron and the rare earth elements Neodymium and Praseodymium using the WIDTH program and NEMO model atmospheres. Initial results are presented, which reinforce the correlation between iron abundance and effective temperature, from an over-abundance in the late Bp stars, to under-abundant in the early F stars. Results also suggest that the disequilibrium in abundances of the first and second ionisation stages of these ions in the rapidly oscillating Ap (roAp) stars may a consequence of the relatively cool temperatures of those stars, rather than a signature of pulsation.

  15. HST AND SPITZER OBSERVATIONS OF THE HD 207129 DEBRIS RING

    SciTech Connect

    Krist, John E.; Stapelfeldt, Karl R.; Bryden, Geoffrey; Rieke, George H.; Su, K. Y. L.; Gaspar, Andras; Chen, Christine C.; Beichman, Charles A.; Hines, Dean C.; Rebull, Luisa M.; Tanner, Angelle; Trilling, David E.; Clampin, Mark

    2010-10-15

    A debris ring around the star HD 207129 (G0V; d = 16.0 pc) has been imaged in scattered visible light with the ACS coronagraph on the Hubble Space Telescope (HST) and in thermal emission using MIPS on the Spitzer Space Telescope at {lambda} = 70 {mu}m (resolved) and 160 {mu}m (unresolved). Spitzer IRS ({lambda} = 7-35 {mu}m) and MIPS ({lambda} = 55-90 {mu}m) spectrographs measured disk emission at {lambda}> 28 {mu}m. In the HST image the disk appears as a {approx}30 AU wide ring with a mean radius of {approx}163 AU and is inclined by 60{sup 0} from pole-on. At 70 {mu}m, it appears partially resolved and is elongated in the same direction and with nearly the same size as seen with HST in scattered light. At 0.6 {mu}m, the ring shows no significant brightness asymmetry, implying little or no forward scattering by its constituent dust. With a mean surface brightness of V = 23.7 mag arcsec{sup -2}, it is the faintest disk imaged to date in scattered light. We model the ring's infrared spectral energy distribution (SED) using a dust population fixed at the location where HST detects the scattered light. The observed SED is well fit by this model, with no requirement for additional unseen debris zones. The firm constraint on the dust radial distance breaks the usual grain size-distance degeneracy that exists in modeling of spatially unresolved disks, and allows us to infer a minimum grain size of {approx}2.8 {mu}m and a dust size distribution power-law spectral index of -3.9. An albedo of {approx}5% is inferred from the integrated brightness of the ring in scattered light. The low-albedo and isotropic scattering properties are inconsistent with Mie theory for astronomical silicates with the inferred grain size and show the need for further modeling using more complex grain shapes or compositions. Brightness limits are also presented for six other main-sequence stars with strong Spitzer excess around which HST detects no circumstellar nebulosity (HD 10472, HD 21997, HD

  16. The abundance of boron in three halo stars

    NASA Technical Reports Server (NTRS)

    Duncan, Douglas K.; Lambert, David L.; Lemke, Michael

    1992-01-01

    B abundances for three halo stars: HD 140283, HD 19445, and HD 201891 are presented. Using recent determinations of the Be abundance in HD 140283, B/Be of 10 +5/-4 is found for this star, and similar ratios are inferred for HD 19445 and HD 201891. This ratio is equal to the minimum value of 10 expected from a synthesis of B and Be by high-energy cosmic-ray spallation reactions in the interstellar medium. It is shown that the accompanying synthesis of Li by alpha on alpha fusion reactions is probably a minor contributor to the observed 'primordial' Li of halo stars. The observed constant ratios of B/O and Be/O are expected if the principal channel of synthesis involves cosmic-ray CNO nuclei from the supernovae colliding with interstellar protons.

  17. The hot subdwarf in the eclipsing binary HD 185510

    NASA Technical Reports Server (NTRS)

    Jeffery, C. S.; Simon, Theodore; Evans, T. L.

    1992-01-01

    High-resolution spectroscopic measurements of radial velocity are employed to characterize the eclipsing binary HD 185510 in terms of masses and evolutionary status. The IUE is used to obtain the radial velocities which indicate a large mass ratio Mp/Ms of 7.45 +/- 0.15, and Teff is given at 25,000 +/- 1000 K based on Ly alpha and UV spectrophotometry. Photometric observations are used to give an orbital inclination of between 90 and 70 deg inclusive, leading to masses of 0.31-0.37 and 2.3-2.8 solar mass for the hot star and the K star, respectively. The surface gravity of HD 185510B is shown to be higher than those values for sdB stars suggesting that the object is a low-mass white dwarf that has not reached its fully degenerate configuration. The object is theorized to be a low-mass helium main-sequence star or a nascent helium degenerate in a post-Algol system.

  18. The Transiting Exocomets in the HD 172555 System

    NASA Technical Reports Server (NTRS)

    Grady, C. A.; Brown, A.; Kamp, I.; Roberge, A.; Riviere-Marichalar, P.; Welsh, B.

    2017-01-01

    The Earth is thought to have formed dry, in a part of the Solar Nebula deficient in organic material, and to have acquired its organics and water through bombardment by minor bodies. Observations of this process in well-dated systems can provide insight into the probable origin and composition of the bombarding parent bodies. Transiting cometary activity has previously been reported in Ca II for the late-A member of the 241 Myr old Pictoris Moving Group member, HD 172555(Kiefer et al. 2014). We present HST STIS and COS spectra of HD 172555 demonstrating that the star has chromospheric emission and variable in falling gas features in transitions of silicon and carbon ions at times when no Fe II absorption is seen in the UV data, and no Ca II absorption is seen in contemporary optical spectra. The lack of CO absorption and stable gas absorption at the system velocity is consistent with the absence of a cold Kuiper belt analog (Riviere-Marichalar et al. 2012) in this system. The presence of infall in some species at one epoch and others at different epochs suggests that, like Pictoris, there may be more than one family of exocomets. If perturbed into star-grazing orbits by the same mechanism as for Pic, these data suggest that the wide planet frequency among A-early F stars in the PMG is at least 37.5, well above the frequency estimated for young moving groups independent of host star spectral type.

  19. THE DISCOVERY OF HD 37605c AND A DISPOSITIVE NULL DETECTION OF TRANSITS OF HD 37605b

    SciTech Connect

    Wang, Sharon Xuesong; Wright, Jason T.; Mahadevan, Suvrath; Cochran, William; Endl, Michael; MacQueen, Phillip J.; Kane, Stephen R.; Von Braun, Kaspar; Henry, Gregory W.; Payne, Matthew J.; Ford, Eric B.; Valenti, Jeff A.; Antoci, Victoria; Dragomir, Diana; Matthews, Jaymie M.; Howard, Andrew W.; Marcy, Geoffrey W.; Isaacson, Howard E-mail: jtwright@astro.psu.edu

    2012-12-10

    We report the radial velocity discovery of a second planetary mass companion to the K0 V star HD 37605, which was already known to host an eccentric, P {approx} 55 days Jovian planet, HD 37605b. This second planet, HD 37605c, has a period of {approx}7.5 years with a low eccentricity and an Msin i of {approx}3.4 M{sub Jup}. Our discovery was made with the nearly 8 years of radial velocity follow-up at the Hobby-Eberly Telescope and Keck Observatory, including observations made as part of the Transit Ephemeris Refinement and Monitoring Survey effort to provide precise ephemerides to long-period planets for transit follow-up. With a total of 137 radial velocity observations covering almost 8 years, we provide a good orbital solution of the HD 37605 system, and a precise transit ephemeris for HD 37605b. Our dynamic analysis reveals very minimal planet-planet interaction and an insignificant transit time variation. Using the predicted ephemeris, we performed a transit search for HD 37605b with the photometric data taken by the T12 0.8 m Automatic Photoelectric Telescope (APT) and the MOST satellite. Though the APT photometry did not capture the transit window, it characterized the stellar activity of HD 37605, which is consistent of it being an old, inactive star, with a tentative rotation period of 57.67 days. The MOST photometry enabled us to report a dispositive null detection of a non-grazing transit for this planet. Within the predicted transit window, we exclude an edge-on predicted depth of 1.9% at the >>10{sigma} level, and exclude any transit with an impact parameter b > 0.951 at greater than 5{sigma}. We present the BOOTTRAN package for calculating Keplerian orbital parameter uncertainties via bootstrapping. We made a comparison and found consistency between our orbital fit parameters calculated by the RVLIN package and error bars by BOOTTRAN with those produced by a Bayesian analysis using MCMC.

  20. The structure and kinematics of the ISM around HD 192281

    NASA Astrophysics Data System (ADS)

    Arnal, E. M.; Cichowolski, S.; Pineault, S.; Testori, J. C.; Cappa, C. E.

    2011-08-01

    Aims: This work aims at investigating the interaction of HD 192281 (O5 Vn((f))p) with its local ISM. The purpose is to analyse the effects that a massive star has on the structure and kinematics of its surrounding gas. Methods: To carry out this study, we used high-resolution radio continuum and 21-cm H i line data from the Canadian Galactic Plane Survey (CGPS). This data base was complemented with radio continuum, infrared, and molecular data retrieved from available surveys. Given that HD 192281 is very likely a runaway star, we attempt to establish whether the observed H i distribution can be interpreted in terms of a simple bow shock model. Results: Analysis of the H i data shows the presence of an H i feature likely to be associated with HD 192281. This feature remains detectable from ~5 to -10 km s-1. At the most negative radial velocities, the shape of the H i feature is highly reminiscent of a bow shock structure seen projected onto the plane of the sky. This feature has counterparts at radio-continuum, infrared, and CO emissions. The analysis of the radio continuum data suggests a thermal spectrum for the gas related to this structure.

  1. Dynamical Study of the Exoplanet Host Binary System HD 106515

    NASA Astrophysics Data System (ADS)

    Rica, F. M.; Barrena, R.; Henríquez, J. A.; Pérez, F. M.; Vargas, P.

    2017-01-01

    HD 106515 AB (STF1619 AB) is a high common proper motion and common radial velocity binary star system composed of two G-type bright stars located at 35 pc and separated by about 7 arcsec. This system was observed by the Hipparcos satellite with a precision in distance and proper motion of 3 and 2%, respectively. The system includes a circumprimary planet of nearly 10 Jupiter masses and a semimajor axis of 4.59 AU, discovered using the radial velocity method. The observational arc of 21° shows a small curvature that evidences HD 106515 AB is a gravitationally bound system. This work determines the dynamical parameters for this system which reinforce the bound status of both stellar components. We determine orbital solutions from instantaneous position and velocity vectors. In addition, we provide a very preliminary orbital solution and a distribution of the orbital parameters, obtained from the line of sight (z). Our results show that HD 106515 AB presents an orbital period of about 4 800 years, a semimajor axis of 345 AU and an eccentricity of about 0.42. Finally, we use an N-body numerical code to perform simulations and reproduce the longer term octupole perturbations on the inner orbit.

  2. Chemical analysis of 24 dusty (pre-)main-sequence stars

    NASA Astrophysics Data System (ADS)

    Acke, B.; Waelkens, C.

    2004-12-01

    We have analysed the chemical photospheric composition of 24 Herbig Ae/Be and Vega-type stars in search for the λ Bootis phenomenon. We present the results of the elemental abundances of the sample stars. Some of the stars were never before studied spectroscopically at optical wavelengths. We have determined the projected rotational velocities of our sample stars. Furthermore, we discuss stars that depict a (selective) depletion pattern in detail. HD 4881 and HD 139614 seem to display an overall deficiency. AB Aur and possibly HD 126367 have subsolar values for the iron abundance, but are almost solar in silicon. HD 100546 is the only clear λ Bootis star in our sample. Appendix is only available in electronic form at http://www.edpsciences.org

  3. A SEARCH FOR THE TRANSIT OF HD 168443b: IMPROVED ORBITAL PARAMETERS AND PHOTOMETRY

    SciTech Connect

    Pilyavsky, Genady; Mahadevan, Suvrath; Wright, Jason T.; Wang, Xuesong X.; Kane, Stephen R.; Ciardi, David R.; Dragomir, Diana; Von Braun, Kaspar; Howard, Andrew W.; De Pree, Chris; Marlowe, Hannah; Fischer, Debra; Henry, Gregory W.; Jensen, Eric L. N.; Laughlin, Gregory

    2011-12-20

    The discovery of transiting planets around bright stars holds the potential to greatly enhance our understanding of planetary atmospheres. In this work we present the search for transits of HD 168443b, a massive planet orbiting the bright star HD 168443 (V = 6.92) with a period of 58.11 days. The high eccentricity of the planetary orbit (e = 0.53) significantly enhances the a priori transit probability beyond that expected for a circular orbit, making HD 168443 a candidate for our ongoing Transit Ephemeris Refinement and Monitoring Survey. Using additional radial velocities from Keck High Resolution Echelle Spectrometer, we refined the orbital parameters of this multi-planet system and derived a new transit ephemeris for HD 168443b. The reduced uncertainties in the transit window make a photometric transit search practicable. Photometric observations acquired during predicted transit windows were obtained on three nights. Cerro Tololo Inter-American Observatory 1.0 m photometry acquired on 2010 September 7 had the required precision to detect a transit but fell just outside of our final transit window. Nightly photometry from the T8 0.8 m automated photometric telescope at Fairborn Observatory, acquired over a span of 109 nights, demonstrates that HD 168443 is constant on a timescale of weeks. Higher-cadence photometry on 2011 April 28 and June 25 shows no evidence of a transit. We are able to rule out a non-grazing transit of HD 168443b.

  4. Direct Imaging of an Asymmetric Debris Disk in the HD 106906 Planetary System

    NASA Astrophysics Data System (ADS)

    Kalas, Paul G.; Rajan, Abhijith; Wang, Jason J.; Millar-Blanchaer, Maxwell A.; Duchene, Gaspard; Chen, Christine; Fitzgerald, Michael P.; Dong, Ruobing; Graham, James R.; Patience, Jennifer; Macintosh, Bruce; Murray-Clay, Ruth; Matthews, Brenda; Rameau, Julien; Marois, Christian; Chilcote, Jeffrey; De Rosa, Robert J.; Doyon, René; Draper, Zachary H.; Lawler, Samantha; Ammons, S. Mark; Arriaga, Pauline; Bulger, Joanna; Cotten, Tara; Follette, Katherine B.; Goodsell, Stephen; Greenbaum, Alexandra; Hibon, Pascale; Hinkley, Sasha; Hung, Li-Wei; Ingraham, Patrick; Konapacky, Quinn; Lafreniere, David; Larkin, James E.; Long, Douglas; Maire, Jérôme; Marchis, Franck; Metchev, Stan; Morzinski, Katie M.; Nielsen, Eric L.; Oppenheimer, Rebecca; Perrin, Marshall D.; Pueyo, Laurent; Rantakyrö, Fredrik T.; Ruffio, Jean-Baptiste; Saddlemyer, Leslie; Savransky, Dmitry; Schneider, Adam C.; Sivaramakrishnan, Anand; Soummer, Rémi; Song, Inseok; Thomas, Sandrine; Vasisht, Gautam; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.; Wolff, Schuyler G.

    2015-11-01

    We present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco-Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ˜50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the “needle” morphology seen for the HD 15115 debris disk. The planet candidate is oriented ˜21° away from the position angle of the primary’s debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary’s disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. We show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.

  5. Direct imaging of an asymmetric debris disk in the HD 106906 planetary system

    SciTech Connect

    Kalas, Paul G.; Rajan, Abhijith; Wang, Jason J.; Millar-Blanchaer, Maxwell A.; Duchene, Gaspard; Chen, Christine; Fitzgerald, Michael P.; Dong, Ruobing; Graham, James R.; Patience, Jennifer; Macintosh, Bruce; Murray-Clay, Ruth; Matthews, Brenda; Rameau, Julien; Marois, Christian; Chilcote, Jeffrey; De Rosa, Robert J.; Doyon, René; Draper, Zachary H.; Lawler, Samantha; Ammons, S. Mark; Arriaga, Pauline; Bulger, Joanna; Cotten, Tara; Follette, Katherine B.; Goodsell, Stephen; Greenbaum, Alexandra; Hibon, Pascale; Hinkley, Sasha; Hung, Li -Wei; Ingraham, Patrick; Lafreniere, David; Larkin, James E.; Long, Douglas; Maire, Jérôme; Marchis, Franck; Metchev, Stan; Morzinski, Katie M.; Nielsen, Eric L.; Oppenheimer, Rebecca; Perrin, Marshall D.; Pueyo, Laurent; Rantakyrö, Fredrik T.; Ruffio, Jean -Baptiste; Saddlemyer, Leslie; Savransky, Dmitry; Schneider, Adam C.; Sivaramakrishnan, Anand; Soummer, Rémi; Song, Inseok; Thomas, Sandrine; Ward-Duong, Kimberly; Wiktorowicz, Sloane J.; Wolff, Schuyler G.

    2015-11-13

    Here, we present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco–Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ~50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the "needle" morphology seen for the HD 15115 debris disk. The planet candidate is oriented ~21° away from the position angle of the primary's debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary's disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. In conclusion, we show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.

  6. Direct imaging of an asymmetric debris disk in the HD 106906 planetary system

    DOE PAGES

    Kalas, Paul G.; Rajan, Abhijith; Wang, Jason J.; ...

    2015-11-13

    Here, we present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco–Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ~50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the "needle" morphologymore » seen for the HD 15115 debris disk. The planet candidate is oriented ~21° away from the position angle of the primary's debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary's disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. In conclusion, we show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.« less

  7. DIRECT IMAGING OF AN ASYMMETRIC DEBRIS DISK IN THE HD 106906 PLANETARY SYSTEM

    SciTech Connect

    Kalas, Paul G.; Wang, Jason J.; Duchene, Gaspard; Dong, Ruobing; Graham, James R.; Rosa, Robert J. De; Rajan, Abhijith; Patience, Jennifer; Millar-Blanchaer, Maxwell A.; Chilcote, Jeffrey; Chen, Christine; Fitzgerald, Michael P.; Macintosh, Bruce; Murray-Clay, Ruth; Matthews, Brenda; Marois, Christian; Draper, Zachary H.; Lawler, Samantha; Rameau, Julien; Doyon, René; and others

    2015-11-20

    We present the first scattered light detections of the HD 106906 debris disk using the Gemini/Gemini Planet Imager in the infrared and Hubble Space Telescope (HST)/Advanced Camera for Surveys in the optical. HD 106906 is a 13 Myr old F5V star in the Sco–Cen association, with a previously detected planet-mass candidate HD 106906b projected 650 AU from the host star. Our observations reveal a near edge-on debris disk that has a central cleared region with radius ∼50 AU, and an outer extent >500 AU. The HST data show that the outer regions are highly asymmetric, resembling the “needle” morphology seen for the HD 15115 debris disk. The planet candidate is oriented ∼21° away from the position angle of the primary’s debris disk, strongly suggesting non-coplanarity with the system. We hypothesize that HD 106906b could be dynamically involved in the perturbation of the primary’s disk, and investigate whether or not there is evidence for a circumplanetary dust disk or cloud that is either primordial or captured from the primary. We show that both the existing optical properties and near-infrared colors of HD 106906b are weakly consistent with this possibility, motivating future work to test for the observational signatures of dust surrounding the planet.

  8. OBSERVATIONS OF ENHANCED RADIATIVE GRAIN ALIGNMENT NEAR HD 97300

    SciTech Connect

    Andersson, B-G; Potter, S. B. E-mail: sbp@saao.ac.z

    2010-09-10

    We have obtained optical multi-band polarimetry toward sightlines through the Chamaeleon I cloud, particularly in the vicinity of the young B9/A0 star HD 97300. We show, in agreement with earlier studies, that the radiation field impinging on the cloud in the projected vicinity of the star is dominated by the flux from the star, as evidenced by a local enhancement in the grain heating. By comparing the differential grain heating with the differential change in the location of the peak of the polarization curve, we show that the grain alignment is enhanced by the increase in the radiation field. We also find a weak, but measurable, variation in the grain alignment with the relative angle between the radiation field anisotropy and the magnetic field direction. Such an anisotropy in the grain alignment is consistent with a unique prediction of modern radiative alignment torque theory and provides direct support for radiatively driven grain alignment.

  9. SILICA-RICH BRIGHT DEBRIS DISK AROUND HD 15407A

    SciTech Connect

    Fujiwara, Hideaki; Onaka, Takashi; Yamashita, Takuya; Takeda, Yoichi; Ishihara, Daisuke; Kataza, Hirokazu; Murakami, Hiroshi; Fukagawa, Misato

    2012-04-20

    We report an intriguing debris disk toward the F3V star HD 15407A in which an extremely large amount of warm fine dust ({approx}10{sup -7} M{sub Circled-Plus }) is detected. The dust temperature is derived as {approx}500-600 K and the location of the debris dust is estimated as 0.6-1.0 AU from the central star, a terrestrial planet region. The fractional luminosity of the debris disk is {approx}0.005, which is much larger than those predicted by steady-state models of the debris disk produced by planetesimal collisions. The mid-infrared spectrum obtained by Spitzer indicates the presence of abundant {mu}m-sized silica dust, suggesting that the dust comes from the surface layer of differentiated large rocky bodies and might be trapped around the star.

  10. Resolving Close Encounters: Stability in the HD 5319 and HD 7924 Planetary Systems

    NASA Astrophysics Data System (ADS)

    Kane, Stephen R.

    2016-10-01

    Radial velocity searches for exoplanets have detected many multi-planet systems around nearby bright stars. An advantage of this technique is that it generally samples the orbit outside of the inferior/superior conjunction, potentially allowing the Keplerian elements of eccentricity and argument of periastron to be well characterized. The orbital architectures for some of these systems show signs of close planetary encounters that may render the systems unstable as described. We provide an in-depth analysis of two such systems: HD 5319 and HD 7924, for which the scenario of coplanar orbits results in their rapid destabilization. The poorly constrained periastron arguments of the outer planets in these systems further emphasizes the need for detailed investigations. An exhaustive scan of parameter space via dynamical simulations reveals specific mutual inclinations between the two outer planets in each system that allow for stable configurations over long timescales. We compare these configurations with those presented by mean-motion resonance as possible stability sources. Finally, we discuss the relevance to interpretation of multi-planet Keplerian orbits and suggest additional observations that will help to resolve the system stabilities.

  11. Three-dimensional orbit and physical parameters of HD 6840

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Li; Ren, Shu-Lin; Fu, Yan-Ning

    2016-02-01

    HD 6840 is a double-lined visual binary with an orbital period of ˜7.5 years. By fitting the speckle interferometric measurements made by the 6 m BTA telescope and 3.5 m WIYN telescope, Balega et al. gave a preliminary astrometric orbital solution of the system in 2006. Recently, Griffin derived a precise spectroscopic orbital solution from radial velocities observed with OPH and Cambridge Coravel. However, due to the low precision of the determined orbital inclination, the derived component masses are not satisfying. By adding the newly collected astrometric data in the Fourth Catalog of Interferometric Measurements of Binary Stars, we give a three-dimensional orbit solution with high precision and derive the preliminary physical parameters of HD 6840 via a simultaneous fit including both astrometric and radial velocity measurements.

  12. The Nature of the Flaring EUVE Companion to HD 43162

    NASA Technical Reports Server (NTRS)

    Kulkarni, Shrinivas R.

    2005-01-01

    The purpose of our program was to observe and characterize the companion to HD 43162, EUVE J0614-2354, which (serendipitously) experienced an enormous flare event during our EUVE observation of HD 43162, one of the nearby solar analogs that we observed during our survey of this population. Our observation was carried out and the data have been received and reduced. We are able to identify EUVE J0614-2354 in both the X-ray (EPIC MOS + PN) and the UV (OM) data, which provides a sub-arcsecond position for this source. Our findings are consistent with the analysis of Christian et al. (2003a,b), who identify EUVE J0614-2354 with a coronally-active M-dwarf star at distance d = 15 plus or minus 5pc. The X-ray spectrum from the EPIC data are also consistent with this identification.

  13. Abundance Analyses of 12 Parent Stars of Extrasolar Planets Observed with the SUBARU/HDS

    NASA Astrophysics Data System (ADS)

    Sadakane, Kozo; Ohkubo, Michiko; Takeda, Yoichi; Sato, Bun'ei; Kambe, Eiji; Aoki, Wako

    2002-12-01

    High S/N ratio (350-600) and high resolution (R ˜ 90000) spectral data covering the wavelength region between 4200-8800Å were obtained for 12 planet-harboring stars with the SUBARU/HDS. Detailed abundance analyses were carried out for these stars using the solar spectrum as a reference. Atmospheric parameters (Teff, logg, microturbulent velocity ξt, and [Fe/H]) were determined spectroscopically using selected Fe I and Fe II lines. The abundances of 25 other elements have been determined relative to the Sun in a strictly differential manner. Three out of 12 stars (HD82943, HD92788, and HD134987) are definitely metal rich, and two stars (HD114762 and HD190228) are metal deficient. The abundances in the remaining seven stars (HD106252, HD130322, HD141937, HD168746, HD187123, HD192263, HD209458) coincide with the Sun. We find that the abundances of both volatile and refractory e lements behave similarly in these stars, and do not confirm any significant dependence on the condensation temperature, Tc. Comparisons of the [X/Fe] vs [Fe/H] relations for 19 elements between planet-harboring stars and nearby field stars reveal no distinct anomaly, except for possible enhancements of V and Co in the former group. These results suggest that the observed over-abundances of metallic elements in planet-harboring stars relative to normal disk stars in the solar neighborhood are primordial, and can be interpreted as being a consequence of the galactic chemical evolution.

  14. Know the Star, Know the Planet. III. Discovery of the Late-Type Companions to Two Exoplanet Host Stars

    DTIC Science & Technology

    2015-03-04

    separations to compute orbital periods of the new stellar companions, HD 2638 has a period of 130 yr and 30 Ari B has a period of 80 yr. Previous...be roughly 0.5 solar mass stars. Key words: binaries: visual – instrumentation: adaptive optics – stars: individual (HD 2638, 30 Ari B) – stars: solar ... array of architectures. With this variety has come an increasing number of models and theories to explain these systems. It has also been realized that

  15. Toward the Infrared Spectrum of the Extrasolar Planet HD209458b

    NASA Astrophysics Data System (ADS)

    Deming, D.; Richardson, L. J.; Goukenleuque, C.; Harrington, J.; Wiedemann, G.

    2002-12-01

    We have conducted ground-based infrared spectroscopic observations during two secondary eclipses of the only known transiting extrasolar planet, HD209458b. We are using the technique of "occultation spectroscopy" (Richardson et al. 2003, Ap.J., in press) to separate the 2 to 4 micron spectrum of the planet from the combined light of the system. Frequent observations of a close comparison star (HD210483) allow us to remove the effects of the terrestrial atmosphere and minimize other errors in excess of the photon noise. Due to excellent observing conditions, we were able to acquire approximately 2500 spectra, equally divided between HD209458 and HD210483, using the SpeX spectrometer at the NASA IRTF on Mauna Kea in September 2001. We exploit the secondary eclipse - when the planet passes behind the star - to isolate the spectrum of the planet. Models of the exoplanet spectrum predict a maximum planet-to-star contrast in the L band near 3.9 microns, with peak contrast values in the approximate range from 3000 to 800 parts-per-million (ppm). Our 1-sigma error level is currently about 500 ppm - already sufficient to rule out the most optimistic contrast values. We are working to decorrelate the remaining noise sources from our data, and refine our analysis toward a measurement of the infrared spectrum of HD209458b.

  16. The peculiar behaviour of the 5780 and 5797 DIBs in HD25137

    NASA Technical Reports Server (NTRS)

    Porceddu, Ignazio; Benvenuti, P.

    1994-01-01

    The interstellar environment close to the high latitude molecular cloud Lynds 1569 (L1569, Lynds 1962), also known as MBM 18 (Magnani, Blitz and Mundy, 1985), has been analyzed by Penrase et al. (1990) and Penrase (1993). Their observations of the CH, CH(sup+), and CN molecular features, are consistent with a region having a high molecular and reduced dust content. They also observed the background star HD 24263- located 8 degrees far from the center of L1569 - reporting a CH rich line of sight and the presence of two intervening clouds from a sodium lines spectra. The infrared excess which has been revealed by the IRAS survey at 12 microns might suggest the presence of PAH's molecules, the well know candidate for the Unidentified Infrared Bands and Diffuse Interstellar Bands. This interesting scenario led to the investigation of the behavior of the diffuse interstellar bands toward HD 25137, which is supposed to be a background object for L1569 (Penrase et al., 1990); as well as the field star HD 24263. As part of a wider observational program devoted to study the HLC's special environments, the observations of the diffuse interstellar bands (DIB's) at 5780 and 5797 lambda lambda in the direction of the two above mentioned stars, HD 24263 and HD 25137 are presented here.

  17. Revising the Evolutionary Stage of HD 163899: The Effects of Convective Overshooting and Rotation

    NASA Astrophysics Data System (ADS)

    Ostrowski, Jakub; Daszyńska-Daszkiewicz, Jadwiga; Cugier, Henryk

    2017-02-01

    We revise the evolutionary status of the B-type supergiant HD 163899 based on the new determinations of the mass–luminosity ratio, effective temperature, and rotational velocity, as well as on the interpretation of the oscillation spectrum of the star. The observed value of the nitrogen-to-carbon abundance fixes the value of the rotation rate of the star. Now, more massive models are strongly preferred than those previously considered, and it is very likely that the star is still in the main-sequence stage. The rotationally induced mixing manifests as the nitrogen overabundance in the atmosphere, which agrees with our analysis of the HARPS spectra. Thus, HD 163899 probably belongs to a group of evolved nitrogen-rich main-sequence stars.

  18. HD-SAO-DM cross index

    NASA Technical Reports Server (NTRS)

    Nagy, T. A.; Mead, J.

    1978-01-01

    A table of correspondence SAO-HD-DM-GC was prepared by Morin (1973). The machine-readable version of this cross identification was obtained from the Centre de Donnees Stellaires (Strasbourg, France). The table was sorted at the Goddard Space Flight Center by HD number and all blank HD number records were removed to produce the HD-SAO-DM table presented. There were 258997 entries in the original table; there are 180411 entries after removing the blank HD records. The Boss General Catalogue (GC) numbers were retained on the machine-readable version after the sort.

  19. STIS coronographic imaging of old PMS stars

    NASA Astrophysics Data System (ADS)

    Lagrange, Anne-Marie

    2000-07-01

    In the past decade, circumstellar {CS} disks of short-lived dust and gas have been evidenced around Main Sequence {MS} stars {e.g. beta Pictoris}. The dust and gas are probably due to planetesimal collisions and/or comet evaporation. These so called ``second generation disks'' are then believed to trace the history of planetary systems formation, in a stage where planetesimals are numerous and planets may be already formed, i.e. an evolved stage compared to the disks around young stars such as Classical T Tauri stars, but yet prior to mostly dust-free planetary systems such as those revealed by radial velocity searches. We recently began to investigate the missing link between MS and young stars CS environments by searching for second generation disks of dust or gas around the few known old PMS stars and by modeling their CS environments. Our HST/NICMOS images revealed a disk around HD141569 {10 Myrs}, and possibly also {but still to be confirmed} around HD100546 and HD135344. We propose here to use the unprecedent detection capabilities of STIS/CORON to get high signal-to-noise {SN} images of HD141569 and HD135344. This will allow to study in much more detail the HD141569 disk, to confirm or infirm the other disk, and to perform fine modeling of the CS dust. This is a key step in the study of the complete evolution of {proto}planetary systems, from the PMS to the MS stages.

  20. Spectral energy distributions of hot stars with circumstellar dust

    NASA Technical Reports Server (NTRS)

    Sitko, M. L.

    1981-01-01

    Combined spectral energy distribution curves of six Ae/Be stars (BD+61 deg 154, AB Aur, V380 Ori, HD 259431, ZCMa, and BD+40 deg 4124), five peculiar shell stars (HD 31648, HD 45677, HD 50138, HD 163296, and HD 190073), and the peculiar central object in the Red Rectangle nebula (HD 44179), obtained with the IUE and a variety of ground-based optical and infrared telescope systems, are presented, covering the wavelength range of approximately 1300 A to 12.5 microns. The observations are reviewed, and include ultraviolet observations, low-resolution absolute visual spectrophotometry, moderate-resolution relative visual spectrophotometry, and infrared photometry. For most of the objects the ratio of the flux deficiency for lambda equals less than 1 micron to the flux excess for lambda equals greater than 1 micron is approximately unity. Only two of the objects (AB Aur and HD 163296) possess a strong emission feature at 9.7 microns, while one other (HD 31648) may have a weak 9.7 micron emission feature. Most of the objects have a broad, smooth, infrared emission curve resembling those seen in some WC stars. It is concluded that the dust surrounding these stars may be different from that seen in the diffuse interstellar medium.

  1. Analysis of the Hipparcos Measurements of HD 10697: A Mass Determination of a Brown Dwarf Secondary.

    PubMed

    Zucker; Mazeh

    2000-03-01

    HD 10697 is a nearby main-sequence star around which a planet candidate has recently been discovered by means of radial velocity measurements (Vogt et al.). The stellar orbit has a period of about 3 yr, the secondary minimum mass is 6.35 Jupiter masses (MJ), and the minimum semimajor axis is 0.36 mas. Using the Hipparcos data of HD 10697 together with the spectroscopic elements of Vogt et al., we found a semimajor axis of 2.1+/-0.7 mas, implying a mass of 38+/-13 MJ for the unseen companion. We therefore suggest that the secondary of HD 10697 is probably a brown dwarf, orbiting around its parent star at a distance of 2 AU.

  2. Long baseline interferometric observations of HD 195019: no K dwarf companion detected

    NASA Technical Reports Server (NTRS)

    Koresko, C.; Memmesson, B.; Boden, A. F.; Akeson, R. L.; Fisher, D. A.; Butter, R. P.; Marcy, G. W.; Vogt, S. S.

    2003-01-01

    Radial velocity measurements of the G3V/IV star HD 195019 revealed the presence of an orbiting companion with m sin(i) = 3.5 Jupiter masses and a period of 18 days. Here we present new visability measurements obtained at the Palomar Testbed Interferometer which rule out any companion in an orbit consistent with the spectroscopic data and having more than 1% of the flux of the primary star in the near-infrared K band.

  3. Fine detrending of raw Kepler and MOST photometric data of KIC 6950556 and HD 37633

    NASA Astrophysics Data System (ADS)

    Mikulášek, Zdeněk; Paunzen, Ernst; Zejda, Miloslav; Semenko, Evgenij; Bernhard, Klaus; Hümmerich, Stefan; Zhang, Jia; Hubrig, Swetlana; Kuschnig, Rainer; Janík, Jan; Jagelka, Miroslav

    2016-07-01

    We present a simple phenomenological method for detrending of raw Kepler and MOST photometry, which is illustrated by means of photometric data processing of two periodically variable chemically peculiar stars, KIC 6950556 and HD 37633. In principle, this method may be applied to any type of periodically variable objects and satellite or ground based photometries. As a by product, we have identified KIC 6950556 as a magnetic chemically peculiar star with an ACV type variability.

  4. Apsidal motion in the massive binary HD 152218

    NASA Astrophysics Data System (ADS)

    Rauw, G.; Rosu, S.; Noels, A.; Mahy, L.; Schmitt, J. H. M. M.; Godart, M.; Dupret, M.-A.; Gosset, E.

    2016-10-01

    Massive binary systems are important laboratories in which to probe the properties of massive stars and stellar physics in general. In this context, we analysed optical spectroscopy and photometry of the eccentric short-period early-type binary HD 152218 in the young open cluster NGC 6231. We reconstructed the spectra of the individual stars using a disentangling code. The individual spectra were then compared with synthetic spectra obtained with the CMFGEN model atmosphere code. We furthermore analysed the light curve of the binary and used it to constrain the orbital inclination and to derive absolute masses of (19.8 ± 1.5) and (15.0 ± 1.1) M⊙. Combining radial velocity measurements from over 60 yr, we show that the system displays apsidal motion at a rate of (2.04+ .23-.24)° yr-1. Solving the Clairaut-Radau equation, we used stellar evolution models, obtained with the CLES code, to compute the internal structure constants and to evaluate the theoretically predicted rate of apsidal motion as a function of stellar age and primary mass. In this way, we determine an age of 5.8 ± 0.6 Myr for HD 152218, which is towards the higher end of, but compatible with, the range of ages of the massive star population of NGC 6231 as determined from isochrone fitting.

  5. ENSTATITE-RICH WARM DEBRIS DUST AROUND HD165014

    SciTech Connect

    Fujiwara, Hideaki; Onaka, Takashi; Ishihara, Daisuke; Yamashita, Takuya; Fukagawa, Misato; Nakagawa, Takao; Kataza, Hirokazu; Murakami, Hiroshi; Ootsubo, Takafumi

    2010-05-01

    We present the Spitzer/Infrared Spectrograph spectrum of the main-sequence star HD165014, which is a warm ({approx_gt}200 K) debris disk candidate discovered by the AKARI All-Sky Survey. The star possesses extremely large excess emission at wavelengths longer than 5 {mu}m. The detected flux densities at 10 and 20 {mu}m are {approx}10 and {approx}30 times larger than the predicted photospheric emission, respectively. The excess emission is attributable to the presence of circumstellar warm dust. The dust temperature is estimated as 300-750 K, corresponding to the distance of 0.7-4.4 AU from the central star. Significant fine-structured features are seen in the spectrum and the peak positions are in good agreement with those of crystalline enstatite. Features of crystalline forsterite are not significantly seen. HD165014 is the first debris disk sample that has enstatite as a dominant form of crystalline silicate rather than forsterite. Possible formation of enstatite dust from differentiated parent bodies is suggested according to the solar system analog. The detection of an enstatite-rich debris disk in the current study suggests the presence of large bodies and a variety of silicate dust processing in warm debris disks.

  6. Observations of Water Ice Distribution in the HD169142 Disk

    NASA Astrophysics Data System (ADS)

    Honda, Mitsuhiko

    2013-01-01

    Icy grains play an important role on planetesimal/planet formation and related matters. Therefore, to reveal ice dust distribution within a protoplanetary disk is an important work for understanding planet formation. However, observations of icy grain IN THE DISK are scarce due to various observational limitations. Here we propose observations to trace the icy grains by making K, H_2O ice, and L' imaging photometric observations of disk scattered light to derive H_2O ice dust distribution in a disk surface via 3.1 mu m absorption. For the moment, only Gemini/NICI is capable of such observations. We have already demonstrated the effectiveness of such observing method toward Herbig Fe star HD142527. Since some theoretical studies suggest that there are no ice grains at the surface of the disk around A/B stars due to intense UV irradiation, we propose to observe disks around Herbig Ae star HD169142. When we fail to detect the ice feature, it supports the theoretical prediction that photodesorption is important. While the ice feature is detected, it requires reconsideration of the theories and provides an important constraint for the disk chemistry.

  7. The polarization of HD 189733

    NASA Astrophysics Data System (ADS)

    Bott, Kimberly; Bailey, Jeremy; Kedziora-Chudczer, Lucyna; Cotton, Daniel V.; Lucas, P. W.; Marshall, Jonathan P.; Hough, J. H.

    2016-06-01

    We present linear polarization observations of the exoplanet system HD 189733 made with the HIgh Precision Polarimetric Instrument (HIPPI) on the Anglo-Australian Telescope (AAT). The observations have higher precision than any previously reported for this object. They do not show the large amplitude polarization variations reported by Berdyugina et al. Our results are consistent with polarization data presented by Wiktorowicz et al. A formal least squares fit of a Rayleigh-Lambert model yields a polarization amplitude of 29.4 ± 15.6 parts per million. We observe a background constant level of polarization of ˜55-70 ppm, which is a little higher than expected for interstellar polarization at the distance of HD 189733.

  8. VizieR Online Data Catalog: Velocity curves of HD 40307 (Mayor+, 2009)

    NASA Astrophysics Data System (ADS)

    Mayor, M.; Udry, S.; Lovis, C.; Pepe, F.; Queloz, D.; Benz, W.; Bertaux, J.-L.; Bouchy, F.; Mordasini, C.; Segransan, D.

    2009-04-01

    HARPS high-precision radial velocities of the star HD 40307. The table contains 3 columns: barycentric Julian date , barycentric radial velocity (km/s) and uncertainty on radial velocity (km/s). The table gives the 129 measurements from which the final orbital parameters are obtained in the paper. (1 data file).

  9. A HIGH-ECCENTRICITY COMPONENT IN THE DOUBLE-PLANET SYSTEM AROUND HD 163607 AND A PLANET AROUND HD 164509

    SciTech Connect

    Giguere, Matthew J.; Fischer, Debra A.; Spronck, Julien; Howard, Andrew W.; Marcy, Geoffrey W.; Isaacson, Howard T.; Johnson, John A.; Henry, Gregory W.; Wright, Jason T.; Hou Fengji

    2012-01-01

    We report the detection of three new exoplanets from Keck Observatory. HD 163607 is a metal-rich G5IV star with two planets. The inner planet has an observed orbital period of 75.29 {+-} 0.02 days, a semi-amplitude of 51.1 {+-} 1.4 m s{sup -1}, an eccentricity of 0.73 {+-} 0.02, and a derived minimum mass of M{sub P} sin i = 0.77 {+-} 0.02 M{sub Jup}. This is the largest eccentricity of any known planet in a multi-planet system. The argument of periastron passage is 78.7 {+-} 2.{sup 0}0; consequently, the planet's closest approach to its parent star is very near the line of sight, leading to a relatively high transit probability of 8%. The outer planet has an orbital period of 3.60 {+-} 0.02 years, an orbital eccentricity of 0.12 {+-} 0.06, and a semi-amplitude of 40.4 {+-} 1.3 m s{sup -1}. The minimum mass is M{sub P} sin i = 2.29 {+-} 0.16 M{sub Jup}. HD 164509 is a metal-rich G5V star with a planet in an orbital period of 282.4 {+-} 3.8 days and an eccentricity of 0.26 {+-} 0.14. The semi-amplitude of 14.2 {+-} 2.7 m s{sup -1} implies a minimum mass of 0.48 {+-} 0.09 M{sub Jup}. The radial velocities (RVs) of HD 164509 also exhibit a residual linear trend of -5.1 {+-} 0.7 m s{sup -1} year{sup -1}, indicating the presence of an additional longer period companion in the system. Photometric observations demonstrate that HD 163607 and HD 164509 are constant in brightness to submillimagnitude levels on their RV periods. This provides strong support for planetary reflex motion as the cause of the RV variations.

  10. The MiMeS survey of Magnetism in Massive Stars: magnetic analysis of the O-type stars

    NASA Astrophysics Data System (ADS)

    Grunhut, J. H.; Wade, G. A.; Neiner, C.; Oksala, M. E.; Petit, V.; Alecian, E.; Bohlender, D. A.; Bouret, J.-C.; Henrichs, H. F.; Hussain, G. A. J.; Kochukhov, O.; MiMeS Collaboration

    2017-02-01

    We present the analysis performed on spectropolarimetric data of 97 O-type targets included in the framework of the Magnetism in Massive Stars (MiMeS) Survey. Mean least-squares deconvolved Stokes I and V line profiles were extracted for each observation, from which we measured the radial velocity, rotational and non-rotational broadening velocities, and longitudinal magnetic field Bℓ. The investigation of the Stokes I profiles led to the discovery of two new multiline spectroscopic systems (HD 46106, HD 204827) and confirmed the presence of a suspected companion in HD 37041. We present a modified strategy of the least-squares deconvolution technique aimed at optimizing the detection of magnetic signatures while minimizing the detection of spurious signatures in Stokes V. Using this analysis, we confirm the detection of a magnetic field in six targets previously reported as magnetic by the MiMeS collaboration (HD 108, HD 47129A2, HD 57682, HD 148937, CPD-28 2561, and NGC 1624-2), as well as report the presence of signal in Stokes V in three new magnetic candidates (HD 36486, HD 162978, and HD 199579). Overall, we find a magnetic incidence rate of 7 ± 3 per cent, for 108 individual O stars (including all O-type components part of multiline systems), with a median uncertainty of the Bℓ measurements of about 50 G. An inspection of the data reveals no obvious biases affecting the incidence rate or the preference for detecting magnetic signatures in the magnetic stars. Similar to A- and B-type stars, we find no link between the stars' physical properties (e.g. Teff, mass, and age) and the presence of a magnetic field. However, the Of?p stars represent a distinct class of magnetic O-type stars.

  11. The chemically peculiar double-lined spectroscopic binary HD 90264

    NASA Astrophysics Data System (ADS)

    Quiroga, C.; Torres, A. F.; Cidale, L. S.

    2010-10-01

    Context. HD 90264 is a chemically peculiar (CP) double-lined spectroscopic binary system of the type He-weak. Double-lined binaries are unique sources of data for stellar masses, physical properties, and evolutionary aspects of stars. Therefore, the determination of orbital elements is of great importance to study how the physical characteristics of CP stars are affected by a companion. Aims: We carried out a detailed spectral and polarimetric study of the spectroscopic binary system HD 90264 to characterize its orbit, determine the stellar masses, and investigate the spectral variability and possible polarization of the binary components. Methods: We employed medium-resolution échelle spectra and polarimetric data obtained at the 2.15-m telescope at CASLEO Observatory, Argentina. We measured radial velocities and line equivalent widths with IRAF packages. The radial velocity curves of both binary components were obtained combining radial velocity data derived from the single line of Hg II λ3984 Åand the double lines of Mg II λ4481 Å. Polarimetric data were studied by means of the statistical method of Clarke & Stewart and the Welch test. Results: We found that both components of the binary system are chemically peculiar stars, deficient in helium, where the primary is a He variable and the secondary is a Hg-Mn star. We derived for the first time the orbital parameters of the binary system. We found that the system has a quasi-circular orbit (e ~ 0.04) with an orbital period of 15.727 days. Taking into account the circular orbit solution, we derived a mass ratio of q = MHe-w/MHg-Mn = 1.22. We also found a rotational period of around 15-16 days, suggesting a spin-orbit synchronization. Possible signs of intrinsic polarization have also been detected. Conclusions: HD 90264 is the first known binary system comprised of a He variable star as the primary component and a Hg-Mn star as the secondary one. Based on observations taken at Complejo Astronómico El

  12. Four-colour photometry of hydrogen-deficient stars and related objects

    NASA Astrophysics Data System (ADS)

    Walker, H. J.; Kilkenny, D.

    1980-01-01

    Stromgren uvby photometry of hydrogen deficient and helium-weak stars suggests that the 'extreme helium' (= 'hydrogen deficient') stars which have been well observed are all variable, probably in a complex way. Previously observed short-term variability of HD 160641 and long-term variability of HD 168476 are confirmed. There is no evidence for variability in the intermediate helium stars or the helium-weak stars.

  13. Two Substellar Companions Orbiting HD 168443

    NASA Astrophysics Data System (ADS)

    Marcy, Geoffrey W.; Butler, R. Paul; Vogt, Steven S.; Liu, Michael C.; Laughlin, Gregory; Apps, Kevin; Graham, J. R.; Lloyd, J.; Luhman, Kevin L.; Jayawardhana, Ray

    2001-07-01

    Precise Doppler measurements during 4.4 yr from the Keck/HIRES spectrometer reveal two superimposed Keplerian velocity variations for HD 168443 (G6 IV). A simultaneous orbital fit to both companions yields companion masses of Msini=7.7 and 17.2 MJUP, orbital periods of P=58 days and 4.8 yr, semimajor axes of a=0.29 and 2.9 AU, and eccentricities of e=0.53 and 0.20. An upper limit to the mass of the outer companion of 42 MJUP is derived from the lack of astrometric wobble. The outer companion was not detected with Keck adaptive optics in the near-IR. Dynamical simulations show that the system is remarkably stable for all possible masses of both companions. The two orbiting companions have masses that are probably near and slightly above the upper end of the observed mass distribution of ``planets'' at 10 MJUP. Formation in a protoplanetary disk seems plausible. But these objects present a puzzle about their formation and dynamical history, as well as about their possible kinship with planetary systems and triple-star systems. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology.

  14. Infrared Transit Spectroscopy of HD 209458b

    NASA Astrophysics Data System (ADS)

    Harrington, J.; Deming, D.; Goukenleuque, C.; Matthews, K.; Richardson, L. J.; Steyert, D.; Wiedemann, G.; Zeehandelaar, D.

    We measure spectra during transits of planet HD 209458b in front of its star to determine its composition and temperature. Transits should modulate the stellar spectrum because tangent rays of different wavelengths become extinct at different levels in the extrasolar planet atmosphere, changing the occulting area. S/N calculations show that ground-based spectroscopy can measure or place useful limits on the atmospheric abundances of water, methane, and carbon monoxide. Carbon forms predominantly methane below 1400 K and carbon monoxide if hotter. Since the equilibrium temperature is about 1400 K, detecting methane and/or carbon monoxide would constrain atmospheric temperatures. We have observed on 12 transit and 4 non-transit nights from Palomar, Keck, VLT, and IRTF. The expected modulation of the stellar spectrum is model-dependent. Since the effect is subtle compared to the noise in the data, we correlate model vs. observed spectra and average the correlations to test whether the data support a given model. We are developing a tangent-geometry radiative-transfer model to predict the spectrum of a given planetary model, and we are measuring water, methane, and carbon monoxide in the laboratory at 1300 K, with pressure-broadening by molecular hydrogen, to make our model spectra realistic at these elevated temperatures. We solicit participation by those who wish to test their planetary models.

  15. The shell spectrum of HD 94509

    NASA Astrophysics Data System (ADS)

    Cowley, Charles R.; Przybilla, Norbert; Hubrig, Swetlana

    2015-01-01

    HD 94509 is a 9th magnitude Be star with an unusually rich metallic-lined shell. The absorption spectrum is rich, comparable to that of an A or F supergiant, but Mg II (4481A), and the Si II (4128 and 4130A), are weak, indicating a dilute radiation field, as described by Otto Struve. The H-alpha emission is double with components of equal intensity and an absorption core that dips well below the stellar continuum. H-beta is weaker, but with a similar structure. H-gamma through H-epsilon have virtually black cores, indicating that the shell covers the stellar disk. The stronger metallic absorption lines are wide near the continuum, but taper to very narrow cores. This line shape is unexplained. However, the total absorption can be modeled to reveal an overall particle densities of 10^{10}-10^{12} cm^{-3}. An electron density log(n_e) = 11.2 is obtained from the Paschen-line convergence and the Inglis-Tellar relation. Column densities are obtained with the help of curves of growth by assuming uniform conditions in the cloud. These indicate a nearly solar composition. The CLOUDY code (Ferland, et al. Rev. Mex. Astron. Astroph. 49, 137, 213) is used to produce a model that predicts matching column densities of the dominant ions, the n = 3 level of hydrogen, the H-alpha strength, and the electron density (± 0.5 dex).

  16. Radio emission from rapidly-rotating cool giant stars

    NASA Technical Reports Server (NTRS)

    Drake, Stephen A.; Walter, Frederick M.; Florkowski, David R.

    1990-01-01

    The results of a VLA program are reported to examine the radio continuum emission from 11 rapidly-rotating cool giant stars, all of which were originally believed to be single stars. Six of the 11 stars were detected as radio sources, including FK Com and HR 9024, for which there exist multifrequency observations. HD 199178, UZ Lib (now known to be a binary system), and HD 82558, for which there is only 6-cm data. The radio properties of these stars are compared with those of the active, rapidly rotating evolved stars found in the RS CVn binary systems.

  17. VizieR Online Data Catalog: Chemical abundances of 8 metal-poor stars (Ishigaki+, 2014)

    NASA Astrophysics Data System (ADS)

    Ishigaki, M. N.; Aoki, W.; Arimoto, N.; Okamoto, S.

    2014-01-01

    Equivalent widths and chemical abundances of the six giant stars in Bootes I dwarf spheroidal galaxy (Boo-009, Boo-094, Boo-117, Boo-121, Boo-127, Boo-911) and the two Milky Way halo stars (HD216143, HD85773) are presented. For each spectral line, excitation potential, loggf values, measured equivalent widths and abundances are given. (2 data files).

  18. An investigation of four chemically peculiar stars with photometric periods below 12 h

    NASA Astrophysics Data System (ADS)

    Hümmerich, Stefan; Bernhard, Klaus; Paunzen, Ernst; Hambsch, Franz-Josef; Bohlsen, Terry; Powles, Jonathan

    2017-04-01

    We present an investigation of three chemically peculiar (CP) stars and one CP star candidate that exhibit photometric periods below 12 h. New spectroscopic observations have been acquired that confirm the peculiar nature of all objects. HD 77013 and HD 81076 are classical CP1 (Am) stars, HD 67983 is a marginal CP1 (Am:) star and HD 98000 is a CP2 (Ap) star. We have procured observations from the ASAS-3 and SuperWASP archives and obtained additional photometry in order to verify the results from the sky survey data. We have derived astrophysical parameters and investigated the positions of our target stars in the MBol versus log Teff diagram, from which information on evolutionary status has been derived. We present period analyses and discuss each object in detail. From the available data, we propose pulsational variability as the underlying mechanism for the variability in HD 67983, HD 77013 and HD 81076, which offer the opportunity to study the interaction of atomic diffusion and pulsation. HD 67983 and HD 77013 exhibit multiperiodic variability in the γ Doradus frequency realm; HD 81076 is a δ Scuti star. The CP2 star HD 98000 exhibits monoperiodic variability with a frequency of f ≈ 2.148 cycles d-1 (P ≈ 0.466 d), which we interpret as the rotational period. If this assumption is correct, HD 98000 is the α2 Canum Venaticorum variable with the shortest period hitherto observed and thus a very interesting object that might help to investigate the influence of rotational mixing on chemical peculiarities.

  19. Star Formation Regions in LDN 1667

    NASA Astrophysics Data System (ADS)

    Gyulbudaghian, A. L.

    2015-09-01

    A group of three star formation regions in the dark cloud LDN 1667 is examined. All three of these regions contain Trapezium type systems. 12C(1-0) observations are made of the part of the molecular cloud LDN 1667 associated with one of the star formation regions. Three molecular clouds were detected, one of which (the main cloud) has a red and a blue outflow. Three stars from the star formation regions are found to have annular nebulae and one star has a conical nebula. The dark cloud LDN 1667 is associated with a radial system of dark globules which is formed by the star HD 57061.

  20. Refined Parameters of the Planet Orbiting HD 189733

    NASA Astrophysics Data System (ADS)

    Bakos, G. Á.; Knutson, H.; Pont, F.; Moutou, C.; Charbonneau, D.; Shporer, A.; Bouchy, F.; Everett, M.; Hergenrother, C.; Latham, D. W.; Mayor, M.; Mazeh, T.; Noyes, R. W.; Queloz, D.; Pál, A.; Udry, S.

    2006-10-01

    We report on the BVRI multiband follow-up photometry of the transiting extrasolar planet HD 189733b. We revise the transit parameters and find a planetary radius of RP=1.154+/-0.033RJ and an inclination of iP=85.79d+/-0.24d. The new density (~1 g cm-3) is significantly higher than the former estimate (~0.75 g cm-3) this shows that from the current sample of nine transiting planets, only HD 209458 (and possibly OGLE-10b) have anomalously large radii and low densities. We note that due to the proximity of its parent star, HD 189733b currently has one of the most precise radius determinations among extrasolar planets. We calculate new ephemerides, P=2.218573+/-0.000020 days and T0=2453629.39420+/-0.00024 (HJD), and estimate the timing offsets of the 11 distinct transits with respect to the predictions of a constant orbital period, which can be used to reveal the presence of additional planets in the system.

  1. Exploring the origin of magnetic fields in massive stars. II. New magnetic field measurements in cluster and field stars

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; Schöller, M.; Ilyin, I.; Kharchenko, N. V.; Oskinova, L. M.; Langer, N.; González, J. F.; Kholtygin, A. F.; Briquet, M.; Magori Collaboration

    2013-03-01

    Context. Theories on the origin of magnetic fields in massive stars remain poorly developed, because the properties of their magnetic field as function of stellar parameters could not yet be investigated. Additional observations are of utmost importance to constrain the conditions that are conducive to magnetic fields and to determine first trends about their occurrence rate and field strength distribution. Aims: To investigate whether magnetic fields in massive stars are ubiquitous or appear only in stars with a specific spectral classification, certain ages, or in a special environment, we acquired 67 new spectropolarimetric observations for 30 massive stars. Among the observed sample, roughly one third of the stars are probable members of clusters at different ages, whereas the remaining stars are field stars not known to belong to any cluster or association. Methods: Spectropolarimetric observations were obtained during four different nights using the low-resolution spectropolarimetric mode of FOcal Reducer low dispersion Spectrograph (FORS 2) mounted on the 8-m Antu telescope of the VLT. Furthermore, we present a number of follow-up observations carried out with the high-resolution spectropolarimeters SOFIN mounted at the Nordic Optical Telescope (NOT) and HARPS mounted at the ESO 3.6 m between 2008 and 2011. To assess the membership in open clusters and associations, we used astrometric catalogues with the highest quality kinematic and photometric data currently available. Results: The presence of a magnetic field is confirmed in nine stars previously observed with FORS 1/2: HD 36879, HD 47839, CPD-28 2561, CPD-47 2963, HD 93843, HD 148937, HD 149757, HD 328856, and HD 164794. New magnetic field detections at a significance level of at least 3σ were achieved in five stars: HD 92206c, HD 93521, HD 93632, CPD-46 8221, and HD 157857. Among the stars with a detected magnetic field, five stars belong to open clusters with high membership probability. According to

  2. The signature of hot hydrogen in the atmosphere of the extrasolar planet HD 209458b

    NASA Astrophysics Data System (ADS)

    Ballester, Gilda E.; Sing, David K.; Herbert, Floyd

    2007-02-01

    About ten per cent of the known extrasolar planets are gas giants that orbit very close to their parent stars. The atmospheres of these `hot Jupiters' are heated by the immense stellar irradiation. In the case of the planet HD 209458b, this energy deposition results in a hydrodynamic state in the upper atmosphere, allowing for sizeable expansion and escape of neutral hydrogen gas. HD 209458b was the first extrasolar planet discovered that transits in front of its parent star. The size of the planet can be measured using the total optical obscuration of the stellar disk during an observed transit, and the structure and composition of the planetary atmosphere can be studied using additional planetary absorption signatures in the stellar spectrum. Here we report the detection of absorption by hot hydrogen in the atmosphere of HD 209458b. Previously, the lower atmosphere and the full extended upper atmosphere of HD 209458b have been observed, whereas here we probe a layer where the escaping gas forms in the upper atmosphere of HD 209458b.

  3. BD+15 2940 AND HD 233604: TWO GIANTS WITH PLANETS CLOSE TO THE ENGULFMENT ZONE

    SciTech Connect

    Nowak, G.; Niedzielski, A.; Adamow, M.; Maciejewski, G.; Wolszczan, A. E-mail: andrzej.niedzielski@astri.umk.pl E-mail: gracjan.maciejewski@astri.umk.pl

    2013-06-10

    We report the discovery of planetary-mass companions to two red giants by the ongoing Penn State-Torun Planet Search (PTPS) conducted with the 9.2 m Hobby-Eberly Telescope. The 1.1 M{sub Sun} K0-giant, BD+15 2940, has a 1.1 M{sub J} minimum mass companion orbiting the star at a 137.5 day period in a 0.54 AU orbit what makes it the closest-in planet around a giant and possible subject of engulfment as the consequence of stellar evolution. HD 233604, a 1.5 M{sub Sun} K5-giant, is orbited by a 6.6 M{sub J} minimum mass planet which has a period of 192 days and a semi-major axis of only 0.75 AU making it one of the least distant planets to a giant star. The chemical composition analysis of HD 233604 reveals a relatively high {sup 7}Li abundance which may be a sign of its early evolutionary stage or recent engulfment of another planet in the system. We also present independent detections of planetary-mass companions to HD 209458 and HD 88133, and stellar activity-induced radial velocity variations in HD 166435, as part of the discussion of the observing and data analysis methods used in the PTPS project.

  4. The signature of hot hydrogen in the atmosphere of the extrasolar planet HD 209458b.

    PubMed

    Ballester, Gilda E; Sing, David K; Herbert, Floyd

    2007-02-01

    About ten per cent of the known extrasolar planets are gas giants that orbit very close to their parent stars. The atmospheres of these 'hot Jupiters' are heated by the immense stellar irradiation. In the case of the planet HD 209458b, this energy deposition results in a hydrodynamic state in the upper atmosphere, allowing for sizeable expansion and escape of neutral hydrogen gas. HD 209458b was the first extrasolar planet discovered that transits in front of its parent star. The size of the planet can be measured using the total optical obscuration of the stellar disk during an observed transit, and the structure and composition of the planetary atmosphere can be studied using additional planetary absorption signatures in the stellar spectrum. Here we report the detection of absorption by hot hydrogen in the atmosphere of HD 209458b. Previously, the lower atmosphere and the full extended upper atmosphere of HD 209458b have been observed, whereas here we probe a layer where the escaping gas forms in the upper atmosphere of HD 209458b.

  5. Photometry of ET Andromedae and pulsation of HD 219891

    NASA Astrophysics Data System (ADS)

    Weiss, W. W.; Kuschnig, R.; Mkrtichian, D. E.; Kusakin, A. V.; Kreidl, T. J.; Bus, S. J.; Osip, D. J.; Guo, Z.; Hao, J.; Huang, L.; Sareyan, J.-P.; Alvarez, M.; Bedolla, S. G.; Zverko, J.; Ziznovsky, J. \\V.; Mittermayer, P.; Zwintz, K.; Polosukhina, N.; Mironov, A. V.; Dorokhov, N. I.; Goranskij, V. P.; Dorokhova, T. N.; Schneider, H.; Hiesberger, F.

    1998-10-01

    ET And is a binary system with a B9p(Si) star as the main component. We report on the photometric observing campaigns in 1988, 1989 and 1994 which confirmed the rotation period of 1.618875 deg for ET And while refuting other published values. Furthermore, the controversial issue of pulsational stability of ET And is resolved since we have discovered pulsation for HD 219891, which was the main comparison star and sometimes exclusively used. The frequency of 10.0816 d(-1) , a semi-amplitude of 2.5 mmag, T_eff\\ and M_v suggest this comparison star to be a delta Scuti variable close to the blue border of the instability strip. The pulsational stability of ET And could be clearly established and hence no need exists to derive new driving mechanisms for stars between the classical instability strip and the region of slowly pulsating B-type (SPB) stars. Based on observations obtained at the Bulgarian National Observatory, Crimean Astrophysical Observatory (Ukraine), Lowell Observatory (USA), Mauna Kea (USA), Mt. Dushak-Erekdak (Turkmenistan), San Pedro (Mexico), Skalnate Pleso (Slovakia), Tien Shan (Kazakhstan) and Wise Observatory (Israel)

  6. Transfer Function Calibration Using AN a2 Star

    NASA Astrophysics Data System (ADS)

    Lupie, Olivia

    1996-07-01

    This proposal acquires FGS TRANS mode scans on asingle star (HD89309) for use in the reference star transfer scanlibrary. These reference scans are crucial calibrations used in theanalysis of the transfer scans of multiple systems.The binary has been studied by Otto Franz and is a puresingle star. This star has been selected to replace areference star which has subsequently shown indications ofduplicity.

  7. Interstellar H2 toward HD 147888

    NASA Astrophysics Data System (ADS)

    Gnaciński, P.

    2013-01-01

    The ultraviolet and far-ultraviolet spectra of HD 147888 allows the H2 vibrational level ν = 0 to be accessed along with higher vibrational levels of the ground H2 electronic level. The large number of H2 absorption lines in the HST spectra allows column densities to be determined even from a noisy spectra. We have determined column densities of the H2 molecule on vibrational levels ν = 0-5 and rotational levels J = 0-6 using the profile fitting method. No variations in the column densities of H2 on vibrationally excited levels were observed from 2000 through 2009. The ortho to para H2 ratio (O/P)* for the excited vibrational states ν = 1-4 equals to 1.13. For the lowest vibrational state ν = 0 and rotational level J = 1 the ortho to para H2 ratio is only 0.15. The temperature of ortho-para thermodynamical equilibrium is TOP = 42 ± 3 K. The measurements of H2 column densities on excited vibrational levels (from the HST spectra) leads to constraints on the radiation field in photon-dominated region (PDR) models of the interstellar cloud towards HD 147888. The Meudon PDR model locates the cloud 0.62 pc from the star. The modeled hydrogen cloud density (89-336 cm-3) agrees with independent density estimations based on the C2 molecule and the chemical model. The observed (O/P)J = 1 and (O/P)* H2 ratios cannot be explained by a simple model. Based on observations made with the NASA/ESA Hubble Space Telescope and with NASA/Johns Hopkins University Far Ultraviolet Spectroscopic Explorer, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555. Support for FUSE data is provided by the NASA Office of Space Science via grant NAG5-7584 and by other grants and contracts.

  8. The Transiting Exocomets in the HD 172555 System

    NASA Astrophysics Data System (ADS)

    Grady, C. A.; Brown, Alexander; Kamp, Inga; Roberge, Aki; Riviere-Marichalar, Pablo; Welsh, Barry

    2017-01-01

    The Earth is thought to have formed dry, in a part of the Solar Nebula deficient in organic material, and to have acquired its water and organics through bombardment by minor bodies. Observations of this process in well-dated systems can provide insight into the probable origin and composition of the bombarding parent bodies. Transiting cometary activity has previously been reported in Ca II for the late-A member of the ~23 Myr old Beta Pictoris Moving Group member, HD 172555. We present HST STIS and COS spectra of HD 172555 which demonstrate that the star has chromospheric emission and variable infalling gas features in transitions of silicon and carbon ions at times when no Fe II absorption is seen in the UV data, and no Ca II absorption is seen in contemporary optical spectra. We discuss apparent optical depths for the infall features. The lack of CO absorption and stable gas absorption at the system velocity is consistent with the absence of a cold Kuiper belt analog in this system. The presence of infall in some species at one epoch and others at different epochs suggests that, like beta Pictoris, there may be more than one family of exocomets. If perturbed into star-grazing orbits by the same mechanism as for beta Pic, these data suggest that the wide planet frequency among A-early F stars in the BPMG is at least 37.5%, well above the frequency estimated for young moving groups independent of host star spectral type.Support for this work was provided by NASA through grant Number HST-GO-13798 from the Space Telescope Science Institute, which is operated by AURA, Inc., under NASA contract NAS5-26555.

  9. A spectrophotometric analysis of the hot helium-rich white dwarf HD 149499 B

    NASA Technical Reports Server (NTRS)

    Sion, E. M.; Guinan, E. F.; Wesemael, F.

    1982-01-01

    A comprehensive analysis of the hot helium-rich white dwarf HD 149499 B is presented based on International Ultraviolet Explorer ultraviolet spectra along with available optical spectra and photometry. Line strengths, line profiles, and continuum fluxes are analyzed in terms of a new grid of hot, high-gravity stellar atmospheres of mixed composition. The line strengths furnish the strongest temperature and gravity diagnostics because they are not affected by the contamination of the white dwarf optical spectrum and photometric properties by the K0 V companion, 2.35 arcsec away. Wegner's (1978) classification of HD 149499 B as a DO star is confirmed.

  10. VizieR Online Data Catalog: WDS-DM-HD-ADS Cross Index (Roman 1987)

    NASA Astrophysics Data System (ADS)

    Roman, N. G.

    1996-11-01

    A machine-readable version of the Washington Catalog of Visual Double Stars (WDS) was prepared in 1984 (Worley 1984) on the basis of a data file that has been collected and maintained for more than a century by a succession of double-star observers. Although this catalog is now being continually updated, a new copy for distribution is not expected to be available for a few years. The WDS contains DM numbers (Argelander 1859-1862, Gill and Kapteyn 1895-1900, Thome 1892-1932), but many of these are listed only in the notes, which makes it difficult to search for double-star information, except by position. Hence, a cross index that provides complete DM identifications is desirable, and it appears useful to add HD numbers (Cannon and Pickering 1918-1924, Cannon 1925- 1936) for systems in that catalog. Aitken Double Star (ADS) numbers (Aitken 1932) have been retained from the WDS, but no attempt has been made to correct these except for obvious errors. A major effort in the preparation of this cross index has been devoted to improving the DM designations. A subset of the information in the WDS has been prepared that lists the 1900 position, the double-star observer and number, the component designation, the DM number, and the ADS number. All DM numbers given only in the notes have been entered by duplicating the entry and changing the component designation appropriately. The standard rule for multiple systems in the catalog is that the DM number refers to the first component. This rule is frequently violated, however, so that it often appears that a single component has two different DM numbers. All such cases have been checked and the component designations have been corrected appropriately. It should be noted that the introduction to the 1984 machine-readable version of the WDS is in error: unless modified by the notes, DM numbers for the -52d zone refer to the CPD. In multiple systems with more than one discoverer name, numbers are sometimes given for components

  11. HD 65949: Rosetta stone or red herring

    NASA Astrophysics Data System (ADS)

    Cowley, C. R.; Hubrig, S.; Palmeri, P.; Quinet, P.; Biémont, É.; Wahlgren, G. M.; Schütz, O.; González, J. F.

    2010-06-01

    HD 65949 is a late B star with exceptionally strong HgII λ3984, but it is not a typical HgMn star. The ReII spectrum is of extraordinary strength. Abundances or upper limits are derived here for 58 elements based on a model with Teff = 13100K and log (g) = 4.0. Even-Z elements through nickel show minor deviations from solar abundances. Anomalies among the odd-Z elements through copper are mostly small. Beyond the iron peak, a huge scatter is found. Enormous enhancements are found for the elements rhenium through mercury (Z = 75-80). We note the presence of ThIII in the spectrum. The abundance pattern of the heaviest elements resembles the N = 126 r-process peak of solar material, though not in detail. An odd-Z anomaly appears at the triplet (Zr Nb Mo), and there is a large abundance jump between Xe (Z = 54) and Ba (Z = 56). These are signatures of chemical fractionation. We find a significant correlation of the abundance excesses with second ionization potentials for elements with Z > 30. If this is not a red herring (false lead), it indicates the relevance of photospheric or near-photospheric processes. Large excesses (4-6 dex) require diffusion from deeper layers with the elements passing through a number of ionization stages. That would make the correlation with second ionization potential puzzling. We explore a model with mass accretion of exotic material followed by the more commonly accepted differentiation by diffusion. That model leads to a number of predictions which challenge future work. New observations confirm the orbital elements of Gieseking and Karimie, apart from the systemic velocity, which has increased. Likely primary and secondary masses are near 3.3 and 1.6 Msolar, with a separation of ca. 0.25 au. New atomic structure calculations are presented in two appendices. These include partition functions for the first through third spectra of Ru, Re and Os, as well as oscillator strengths in the ReII spectrum. Based on observations obtained at the

  12. Spectroscopy of γ Doradus stars

    NASA Astrophysics Data System (ADS)

    Brunsden, E.; Pollard, K. R.; Cottrell, P. L.; Wright, D. J.; De Cat, P.; Kilmartin, P. M.

    2014-02-01

    The musician programme at the University of Canterbury has been successfully identifying pulsation modes in many γ Doradus stars using hundreds of ground-based spectroscopic observations. This paper describes some of the successful mode identifications and emerging patterns of the programme. The hybrid γ Doradus/δ Scuti star HD 49434 remains an enigma, despite the analysis of more than 1700 multi-site high-resolution spectra. A new result for this star is apparently distinct line-profile variations for the γ Doradus and δ Scuti frequencies.

  13. XMM-NEWTON OBSERVATIONS OF HD 189733 DURING PLANETARY TRANSITS

    SciTech Connect

    Pillitteri, I.; Wolk, S. J.; Cohen, O.; Kashyap, V.; Knutson, H.; Lisse, C. M.; Henry, G. W.

    2010-10-20

    We report on two XMM-Newton observations of the planetary host star HD 189733. The system has a close in planet and it can potentially affect the coronal structure via interactions with the magnetosphere. We have obtained X-ray spectra and light curves from EPIC and the Reflection Grating Spectrometer on board XMM-Newton which we have analyzed and interpreted. We reduced X-ray data from the primary transit and secondary eclipse that occurred on 2007 April 17 and 2009 May 18, respectively. In the 2007 April observation, only variability due to weak flares is recognized. In 2009 HD 189733 exhibited an X-ray flux that was always larger than in the 2007 observation. The average flux in 2009 was higher than in the 2007 observation by a factor of 45%. During the 2009 secondary eclipse we observed a significant softening of the X-ray spectrum at a level of {approx}3{sigma}. Furthermore, we observed the most intense flare recorded at either epoch. This flare occurred 3 ks after the end of the eclipse. The flare decay shows several minor ignitions perhaps linked to the main event and hinting at secondary loops that are triggered by the main loop. Magnetohydrodynamic (MHD) simulations show that the magnetic interaction between planet and star enhances the density and the magnetic field in a region between the planet and the star because of their relative orbital/rotation motion. X-ray observations and model predictions are globally found in agreement, despite the quite simple MHD model and the lack of precise estimate of parameters including the alignment and the intensity of stellar and planetary magnetic fields. Future observations should confirm or disprove this hypothesis, by determining whether flares are systematically recurring in the light curve at the same planetary phase.

  14. PLANETS AROUND THE K-GIANTS BD+20 274 AND HD 219415

    SciTech Connect

    Gettel, S.; Wolszczan, A.; Niedzielski, A.; Nowak, G.; Adamow, M.; Zielinski, P.; Maciejewski, G. E-mail: alex@astro.psu.edu

    2012-09-01

    We present the discovery of planet-mass companions to two giant stars by the ongoing Penn State-Torun Planet Search conducted with the 9.2 m Hobby-Eberly Telescope. The less massive of these stars, K5-giant BD+20 274, has a 4.2 M{sub J} minimum mass planet orbiting the star at a 578 day period and a more distant, likely stellar-mass companion. The best currently available model of the planet orbiting the K0-giant HD 219415 points to a {approx}> Jupiter-mass companion in a 5.7 year, eccentric orbit around the star, making it the longest period planet yet detected by our survey. This planet has an amplitude of {approx}18 m s{sup -1}, comparable to the median radial velocity 'jitter', typical of giant stars.

  15. HD 172555: Detection of 63 micrometers [OI] Emission in a Debris Disc

    NASA Technical Reports Server (NTRS)

    Riviere-Marichalar, P.; Barrado, D.; Augereau, J. -C.; Thi, W. F.; Roberge, A.; Eiroa, C.; Montesinos, B.; Meeus, G.; Howard, C.; Sandell, G.; Duchene, G.; Dent, W. R. F.; Lebreton, J.; Mendigutia, I.; Huelamo, N.; Menard, F.; Pinte, C.

    2012-01-01

    Context. HD 172555 is a young A7 star belonging to the Beta Pictoris Moving Group that harbours a debris disc. The Spitzer IRS spectrum of the source showed mid-IR features such as silicates and glassy silica species, indicating the presence of a warm dust component with small grains, which places HD 172555 among the small group of debris discs with such properties. The IRS spectrum also shows a possible emission of SiO gas. Aims. We aim to study the dust distribution in the circumstellar disc of HD 172555 and to asses the presence of gas in the debris disc. Methods. As part of the GASPS Open Time Key Programme, we obtained Herschel-PACS photometric and spectroscopic observations of the source. We analysed PACS observations of HD 172555 and modelled the Spectral Energy Distribution (SED) with a modified blackbody and the gas emission with a two-level population model with no collisional de-excitation. Results. We report for the first time the detection of [OI] atomic gas emission at 63.18 micrometers in the HD 172555 circumstellar disc.We detect excesses due to circumstellar dust toward HD 172555 in the three photometric bands of PACS (70, 100, and 160 m). We derive a large dust particle mass of (4.8 plus-minus 0.6)x10(exp -4) Mass compared to Earth and an atomic oxygen mass of 2.5x10(exp -2)R(exp 2) Mass compared to Earth, where R in AU is the separation between the star and the inner disc. Thus, most of the detected mass of the disc is in the gaseous phase.

  16. Evidence for the Direct Detection of the Thermal Spectrum of the Non-Transiting Hot Gas Giant HD 88133 b

    NASA Astrophysics Data System (ADS)

    Piskorz, Danielle; Crockett, Nathan R.; Lockwood, Alexandra; Benneke, Björn; Blake, Geoffrey A.; Barman, Travis S.; Bender, Chad F.; Bryan, Marta; Carr, John S.; Fischer, Debra; Howard, Andrew; Isaacson, Howard T.; Johnson, John A.

    2016-10-01

    We target the thermal emission spectrum of the non-transiting gas giant HD 88133 b with high-resolution near-infrared spectroscopy, by treating the planet and its host star as a spectroscopic binary. For sufficiently deep summed flux observations of the star and planet across multiple epochs, it is possible to resolve the signal of the hot gas giant's atmosphere compared to the brighter stellar spectrum, at a level consistent with the aggregate shot noise of the full data set. To do this, we first perform a principal component analysis to remove the contribution of the Earth's atmosphere to the observed spectra. Then, we use a cross-correlation analysis to tease out the spectra of the host star and HD 88133 b to determine its orbit and identify key sources of atmospheric opacity. In total, six epochs of Keck NIRSPEC L band observations and three epochs of Keck NIRSPEC K band observations of the HD 88133 system were obtained. Based on an analysis of the maximum likelihood curves calculated from the multi-epoch cross correlation of the full data set with two atmospheric models, we report the direct detection of the emission spectrum of the non-transiting exoplanet HD 88133 b and measure a radial projection of its Keplerian orbital velocity, its true mass, its orbital inclination, and dominant atmospheric species. This, combined with eleven years of radial velocity measurements of the system, provides the most up-to-date ephemeris for HD 88133.

  17. Synthetic filter photometry and evolutionary status of two Be stars in the association Per OB1

    NASA Technical Reports Server (NTRS)

    Torres, Ana V.

    1987-01-01

    Stromgren and H-beta colors have been determined from spectrophotometric observations for two Be stars without published photometry in the association Per OB1: HD 12856 (B0 pe) and HD 13890 (B1 III:pe). Stellar parameters and improved spectral types are then derived from the color indices using the calibrations of Jakobsen (1986), and independently from the BCD classification method. The intrinsic properties of HD 12856 and HD 13890 are compared with those of normal B stars and are used to estimate their evolutionary status.

  18. MODELING THE HD 32297 DEBRIS DISK WITH FAR-INFRARED HERSCHEL DATA

    SciTech Connect

    Donaldson, J. K.; Lebreton, J.; Augereau, J.-C.; Krivov, A. V.

    2013-07-20

    HD 32297 is a young A-star ({approx}30 Myr) 112 pc away with a bright edge-on debris disk that has been resolved in scattered light. We observed the HD 32297 debris disk in the far-infrared and sub-millimeter with the Herschel Space Observatory PACS and SPIRE instruments, populating the spectral energy distribution (SED) from 63 to 500 {mu}m. We aimed to determine the composition of dust grains in the HD 32297 disk through SED modeling, using geometrical constraints from the resolved imaging to break the degeneracies inherent in SED modeling. We found the best fitting SED model has two components: an outer ring centered around 110 AU, seen in the scattered light images, and an inner disk near the habitable zone of the star. The outer disk appears to be composed of grains >2 {mu}m consisting of silicates, carbonaceous material, and water ice with an abundance ratio of 1:2:3 respectively and 90% porosity. These grains appear consistent with cometary grains, implying the underlying planetesimal population is dominated by comet-like bodies. We also discuss the 3.7{sigma} detection of [C II] emission at 158 {mu}m with the Herschel PACS instrument, making HD 32297 one of only a handful of debris disks with circumstellar gas detected.

  19. Modeling the HD 32297 Debris Disk With Far-Infrared Herschel Data

    NASA Technical Reports Server (NTRS)

    Donaldson, J.K.; Lebreton, J.; Roberge, A.; Augereau, J.-C.; Krivov, A. V.

    2013-01-01

    HD 32297 is a young A-star (approx. 30 Myr) 112 pc away with a bright edge-on debris disk that has been resolved in scattered light. We observed the HD 32297 debris disk in the far-infrared and sub-millimeter with the Herschel Space Observatory PACS and SPIRE instruments, populating the spectral energy distribution (SED) from 63 to 500 micron..We aimed to determine the composition of dust grains in the HD 32297 disk through SED modeling, using geometrical constraints from the resolved imaging to break the degeneracies inherent in SED modeling. We found the best fitting SED model has two components: an outer ring centered around 110 AU, seen in the scattered light images, and an inner disk near the habitable zone of the star. The outer disk appears to be composed of grains>2 micron consisting of silicates, carbonaceous material, and water ice with an abundance ratio of 1:2:3 respectively and 90% porosity. These grains appear consistent with cometary grains, implying the underlying planetesimal population is dominated by comet-like bodies. We also discuss the 3.7 sigma detection of [C ii] emission at 158 micron with the Herschel PACS instrument, making HD 32297 one of only a handful of debris disks with circumstellar gas detected

  20. The SOPHIE search for northern extrasolar planets. II. A multiple planet system around HD 9446

    NASA Astrophysics Data System (ADS)

    Hébrard, G.; Bonfils, X.; Ségransan, D.; Moutou, C.; Delfosse, X.; Bouchy, F.; Boisse, I.; Arnold, L.; Desort, M.; Díaz, R. F.; Eggenberger, A.; Ehrenreich, D.; Forveille, T.; Lagrange, A.-M.; Lovis, C.; Pepe, F.; Perrier, C.; Pont, F.; Queloz, D.; Santos, N. C.; Udry, S.; Vidal-Madjar, A.

    2010-04-01

    We report the discovery of a planetary system around HD 9446, performed from radial velocity measurements secured with the spectrograph SOPHIE at the 193-cm telescope of the Haute-Provence Observatory for more than two years. At least two planets orbit this G5V, active star: HD 9446b has a minimum mass of 0.7 MJup and a slightly eccentric orbit with a period of 30 days, whereas HD 9446c has a minimum mass of 1.8 MJup and a circular orbit with a period of 193 days. As for most of the known multiple planet systems, the HD 9446-system presents a hierarchical disposition with a massive outer planet and a lighter inner planet. Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium (program 07A.PNP.CONS). The full version of Table 1 (SOPHIE measurements of HD 9446) is 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/513/A69

  1. THE NON-THERMAL RADIO EMITTER HD 93250 RESOLVED BY LONG BASELINE INTERFEROMETRY

    SciTech Connect

    Sana, H.; De Koter, A.; Le Bouquin, J.-B.; Berger, J.-P.; Merand, A.

    2011-10-20

    As the brightest O-type X-ray source in the Carina nebula, HD 93250 (O4 III(fc)) is X-ray overluminous for its spectral type and has an unusually hard X-ray spectrum. Two different scenarios have been invoked to explain its X-ray properties: wind-wind interaction and magnetic wind confinement. Yet, HD 93250 shows absolutely constant radial velocities over timescales of years suggesting either a single star, a binary system seen pole-on view or a very long period, and/or highly eccentric system. Using the ESO Very Large Telescope Interferometer, we resolved HD 93250 as a close pair with similar components. We measured a near-infrared flux ratio of 0.8 {+-} 0.1 and a separation of (1.5 {+-} 0.2) x 10{sup -3} arcsec. At the distance of Carina, this corresponds to a projected physical distance of 3.5 AU. While a quantitative investigation would require a full characterization of the orbit, the binary nature of HD 93250 allows us to qualitatively explain both its X-ray flux and hardness and its non-thermal radio emission in the framework of a colliding wind scenario. We also discuss various observational biases. We show that, due to line blending of two similar spectral components, HD 93250 could have a period as short as 1 to several years despite the lack of measurable radial velocity variations.

  2. Discovery of Molecular Gas around HD 131835 in an APEX Molecular Line Survey of Bright Debris Disks

    NASA Astrophysics Data System (ADS)

    Moór, A.; Henning, Th.; Juhász, A.; Ábrahám, P.; Balog, Z.; Kóspál, Á.; Pascucci, I.; Szabó, Gy. M.; Vavrek, R.; Curé, M.; Csengeri, T.; Grady, C.; Güsten, R.; Kiss, Cs.

    2015-11-01

    Debris disks are considered to be gas-poor, but recent observations revealed molecular or atomic gas in several 10-40 Myr old systems. We used the APEX and IRAM 30 m radio telescopes to search for CO gas in 20 bright debris disks. In one case, around the 16 Myr old A-type star HD 131835, we discovered a new gas-bearing debris disk, where the CO 3-2 transition was successfully detected. No other individual system exhibited a measurable CO signal. Our Herschel Space Observatory far-infrared images of HD 131835 marginally resolved the disk at both 70 and 100 μm, with a characteristic radius of ˜170 AU. While in stellar properties HD 131835 resembles β Pic, its dust disk properties are similar to those of the most massive young debris disks. With the detection of gas in HD 131835 the number of known debris disks with CO content has increased to four, all of them encircling young (≤40 Myr) A-type stars. Based on statistics within 125 pc, we suggest that the presence of a detectable amount of gas in the most massive debris disks around young A-type stars is a common phenomenon. Our current data cannot conclude on the origin of gas in HD 131835. If the gas is secondary, arising from the disruption of planetesimals, then HD 131835 is a comparably young, and in terms of its disk, more massive analog of the β Pic system. However, it is also possible that this system, similar to HD 21997, possesses a hybrid disk, where the gas material is predominantly primordial, while the dust grains are mostly derived from planetesimals.

  3. DISCOVERY OF MOLECULAR GAS AROUND HD 131835 IN AN APEX MOLECULAR LINE SURVEY OF BRIGHT DEBRIS DISKS

    SciTech Connect

    Moór, A.; Ábrahám, P.; Kóspál, Á.; Szabó, Gy. M.; Kiss, Cs.; Henning, Th.; Balog, Z.; Juhász, A.; Pascucci, I.; Vavrek, R.; Csengeri, T.; Güsten, R.; Grady, C.

    2015-11-20

    Debris disks are considered to be gas-poor, but recent observations revealed molecular or atomic gas in several 10–40 Myr old systems. We used the APEX and IRAM 30 m radio telescopes to search for CO gas in 20 bright debris disks. In one case, around the 16 Myr old A-type star HD 131835, we discovered a new gas-bearing debris disk, where the CO 3–2 transition was successfully detected. No other individual system exhibited a measurable CO signal. Our Herschel Space Observatory far-infrared images of HD 131835 marginally resolved the disk at both 70 and 100 μm, with a characteristic radius of ∼170 AU. While in stellar properties HD 131835 resembles β Pic, its dust disk properties are similar to those of the most massive young debris disks. With the detection of gas in HD 131835 the number of known debris disks with CO content has increased to four, all of them encircling young (≤40 Myr) A-type stars. Based on statistics within 125 pc, we suggest that the presence of a detectable amount of gas in the most massive debris disks around young A-type stars is a common phenomenon. Our current data cannot conclude on the origin of gas in HD 131835. If the gas is secondary, arising from the disruption of planetesimals, then HD 131835 is a comparably young, and in terms of its disk, more massive analog of the β Pic system. However, it is also possible that this system, similar to HD 21997, possesses a hybrid disk, where the gas material is predominantly primordial, while the dust grains are mostly derived from planetesimals.

  4. Direct detection of the tertiary component in the massive multiple HD 150136 with VLTI

    NASA Astrophysics Data System (ADS)

    Sanchez-Bermudez, J.; Schödel, R.; Alberdi, A.; Barbá, R. H.; Hummel, C. A.; Maíz Apellániz, J.; Pott, J.-U.

    2013-06-01

    Context. Massive stars are of fundamental importance for almost all aspects of astrophysics, but there still exist large gaps in our understanding of their properties and formation because they are rare and therefore distant. It has been found that most O-stars are multiples. It may well be that almost all massive stars are born as triples or higher multiples, but their large distances require milliarcsecond angular resolution for a direct detection of the companions. Aims: HD 150136 is the nearest system to Earth with >100 M⊙ and provides a unique opportunity to study an extremely massive system. Recently, evidence for the existence of a third component in HD 150136, in addition to the tight spectroscopic binary that forms the main component, was found in spectroscopic observations. Our aim was to image and obtain astrometric and photometric measurements of this component using long-baseline optical interferometry to further constrain the nature of this component. Methods: We observed HD 150136 with the near-infrared instrument AMBER attached to the ESO VLT Interferometer, which provides an angular resolution of 2 mas. The recovered closure phases are robust to systematic errors and provide unique information on the source asymmetry. Therefore, they are of crucial relevance for both image reconstruction and model fitting of the source structure. Results: The third component in HD 150136 is clearly detected in the high-quality data from AMBER. It is located at a projected angular distance of 7.3 mas, or about 13 AU at the line-of-sight distance of HD 150136, at a position angle of 209 degrees east of north, and has a flux ratio of 0.25 with respect to the inner binary. Our findings agree with previous results and have permitted us to improve the orbital solutions of the tertiary around the inner system. Conclusions: We resolved the third component of HD 150136 in J, H and K filters. The luminosity and color of the tertiary agrees with the predictions and shows

  5. Interrogation of duplicitous stars with an APT

    NASA Technical Reports Server (NTRS)

    Bopp, Bernard W.

    1992-01-01

    Preliminary results from intensive spectroscopic and APT monitoring of two interacting binary systems are presented. Both V644 Mon (Be + K:) and HD 37453 (F5 II + B) show complex, composite, and variable spectral. APT observations extending over three years show both stars to vary by 0.1-0.2 mag in V. The photometric variability of V644 Mon appears to be irregular, though there is some evidence for periodic behavior in the 50-60 day range. HD 37453 has an orbital period of 66.75 days; the best-fit photometric period is not quite half this value, indicating the star is an ellipsoidal variable.

  6. The Nainital-Cape Survey. IV. A search for pulsational variability in 108 chemically peculiar stars

    NASA Astrophysics Data System (ADS)

    Joshi, S.; Martinez, P.; Chowdhury, S.; Chakradhari, N. K.; Joshi, Y. C.; van Heerden, P.; Medupe, T.; Kumar, Y. B.; Kuhn, R. B.

    2016-05-01

    Context. The Nainital-Cape Survey is a dedicated ongoing survey program to search for and study pulsational variability in chemically peculiar (CP) stars to understand their internal structure and evolution. Aims: The main aims of this survey are to find new pulsating Ap and Am stars in the northern and southern hemisphere and to perform asteroseismic studies of these new pulsators. Methods: The survey is conducted using high-speed photometry. The candidate stars were selected on the basis of having Strömgren photometric indices similar to those of known pulsating CP stars. Results: Over the last decade a total of 337 candidate pulsating CP stars were observed for the Nainital-Cape Survey, making it one of the longest ground-based surveys for pulsation in CP stars in terms of time span and sample size. The previous papers of this series presented seven new pulsating variables and 229 null results. In this paper we present the light curves, frequency spectra and various astrophysical parameters of the 108 additional CP stars observed since the last reported results. We also tabulated the basic physical parameters of the known roAp stars. As a part of establishing the detection limits in the Nainital-Cape Survey, we investigated the scintillation noise level at the two observing sites used in this survey, Sutherland and Nainital, by comparing the combined frequency spectra stars observed from each location. Our analysis shows that both the sites permit the detection of variations of the order of 0.6 milli-magnitude (mmag) in the frequency range 1-4 mHz, Sutherland is on average marginally better. The dataset 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/590/A116

  7. NON-DETECTION OF PREVIOUSLY REPORTED TRANSITS OF HD 97658b WITH MOST PHOTOMETRY

    SciTech Connect

    Dragomir, Diana; Matthews, Jaymie M.; Antoci, Victoria; Howard, Andrew W.; Marcy, Geoffrey W.; Henry, Gregory W.; Guenther, David B.; Johnson, John A.; Kuschnig, Rainer; Weiss, Werner W.; Moffat, Anthony F. J.; Rowe, Jason F.; Rucinski, Slavek M.; Sasselov, Dimitar

    2012-11-10

    The radial velocity-discovered exoplanet HD 97658b was recently announced to transit, with a derived planetary radius of 2.93 {+-} 0.28 R{sub Circled-Plus }. As a transiting super-Earth orbiting a bright star, this planet would make an attractive candidate for additional observations, including studies of its atmospheric properties. We present and analyze follow-up photometric observations of the HD 97658 system acquired with the Microvariability and Oscillations of STars space telescope. Our results show no transit with the depth and ephemeris reported in the announcement paper. For the same ephemeris, we rule out transits for a planet with radius larger than 2.09 R{sub Circled-Plus }, corresponding to the reported 3{sigma} lower limit. We also report new radial velocity measurements which continue to support the existence of an exoplanet with a period of 9.5 days, and obtain improved orbital parameters.

  8. Spectroscopic study of the strontium AM binaries HD 434 and 41 Sex A

    NASA Astrophysics Data System (ADS)

    Sreedhar Rao, S.; Abhyankar, K. D.

    1992-10-01

    Improved spectroscopic orbital elements of the single-line Am binary HD 434 are presented, and cover large gaps in the radial velocity curve obtained earlier by Hube and Gulliver (1985). The MK morphology of the spectrum of HD 434 is examined, and the classification of its metallic line types in the violet and blue regions, along with its revised K- and H-line spectral types, are given for the first time. The strontium anomaly in its spectrum is discussed. 41 Sex A is found to be a prototype of an Am star exhibiting transitional characteristics, forming an evolutionary link between Ap and Am groups of CP stars. Its spectroscopic orbital elements are confirmed using our own velocities. The MK morphology of its spectrum and its spectral line behavior, especially that of the Sr II 4077 line, are briefly discussed.

  9. VizieR Online Data Catalog: HD 18078 uvby light curves (Mathys+, 2016)

    NASA Astrophysics Data System (ADS)

    Mathys, G.; Romanyuk, I. I.; Kudryavtsev, D. O.; Landstreet, J. D.; Pyper, D. M.; Adelman, S. J.

    2015-11-01

    This table contains the good observations of HD 18078 obtained with the Four College Automated Photoelectric Telescope, Washington Camp, Arizona, United States of America. The data were obtained in the Stromgren uvby system. It measures the dark count and then, in each filter, sky-ch-c-v-c-v-c-v-c-ch-sky for each group of variable (v), check (ch), and comparison (c) stars where sky is a reading of the sky. (1 data file).

  10. HARPS spectropolarimetry of Herbig Ae/Be stars

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; Ilyin, I.; Schöller, M.; Lo Curto, G.

    2013-12-01

    Our knowledge of the presence and the strength of magnetic fields in intermediate-mass pre-main-sequence stars remains very poor. We present new magnetic field measurements in six Herbig Ae/Be stars observed with HARPS in spectropolarimetric mode. We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for six Herbig Ae/Be stars. Wavelength shifts between right- and left-hand side circularly polarised spectra were interpreted in terms of a longitudinal magnetic field , using the moment technique introduced by Mathys. The application of the moment technique to the HARPS spectra allowed us in addition to study the presence of the crossover effect and quadratic magnetic fields. Our search for longitudinal magnetic fields resulted in first detections of weak magnetic fields in the Herbig Ae/Be stars HD 58647 and HD 98922. Further, we confirm the previous tentative detection of a weak magnetic field in HD 104237 by Donati et al. and confirm the previous detection of a magnetic field in the Herbig Ae star HD 190073. Surprisingly, the measured longitudinal magnetic field of HD 190073, < Bz >=91±18 G at a significance level of 5σ is not in agreement with the measurement results of Alecian et al. (2013), < Bz >=-10±20 G, who applied the LSD method to exactly the same data. No crossover effect was detected for any star in the sample. Only for HD 98922 the crossover effect was found to be close to 3σ with a measured value of -4228±1443 km s-1 G. A quadratic magnetic field of the order of 10 kG was detected in HD 98922, and of ˜3.5 kG in HD 104237. Based on data obtained from the ESO Science Archive Facility under requests MSCHOELLER 51301, 51324, 36608-36611.

  11. Line profile variability in the massive binary HD 152219

    NASA Astrophysics Data System (ADS)

    Sana, H.; Gosset, E.

    2009-07-01

    HD 152219 is a massive binary system with O9.5 III and B1-2 III/V components and a short orbital period of 4.2 d. In a previous work, we showed that the primary star (M_{prim}˜21 M_⊙) was presenting clear line profile variabilities (LPVs) that might be caused by nonradial pulsations (NRPs). In the present work, we report on an intensive spectroscopic monitoring, that aimed at unveiling the nature of the detected LPVs. Based on this new data set, we discard the NRPs and point out the Rossiter-McLaughlin effect as % being the cause of the observed LPVs. The upper limit derived on the amplitude of undetected NRPs, if any, is set at a couple of part per thousands of the continuum level.

  12. The Very Low Albedo of an Extrasolar Planet: MOST Space-based Photometry of HD 209458

    NASA Astrophysics Data System (ADS)

    Rowe, Jason F.; Matthews, Jaymie M.; Seager, Sara; Miller-Ricci, Eliza; Sasselov, Dimitar; Kuschnig, Rainer; Guenther, David B.; Moffat, Anthony F. J.; Rucinski, Slavek M.; Walker, Gordon A. H.; Weiss, Werner W.

    2008-12-01

    Measuring the albedo of an extrasolar planet provides insight into its atmospheric composition and its global thermal properties, including heat dissipation and weather patterns. Such a measurement requires very precise photometry of a transiting system, fully sampling many phases of the secondary eclipse. Space-based optical photometry of the transiting system HD 209458 from the MOST (Microvariablity and Oscillations of Stars) satellite, spanning 14 and 44 days in 2004 and 2005, respectively, allows us to set a sensitive limit on the optical eclipse of the hot exosolar giant planet in this system. Our best fit to the observations yields a flux ratio of the planet and star of 7 +/- 9 ppm (parts per million), which corresponds to a geometric albedo through the MOST bandpass (400-700 nm) of Ag = 0.038 +/- 0.045. This gives a 1 σ upper limit of 0.08 for the geometric albedo and a 3 σ upper limit of 0.17. HD 209458b is significantly less reflective than Jupiter (for which Ag would be about 0.5). This low geometric albedo rules out the presence of bright reflective clouds in this exoplanet's atmosphere. We determine refined parameters for the star and exoplanet in the HD 209458 system based on a model fit to the MOST light curve. MOST is a Canadian Space Agency mission, operated jointly by Dynacon, Inc., and the Universities of Toronto and British Columbia, with assistance from the University of Vienna.

  13. Radial velocities of southern visual multiple stars

    SciTech Connect

    Tokovinin, Andrei; Pribulla, Theodor; Fischer, Debra E-mail: pribulla@ta3.sk

    2015-01-01

    High-resolution spectra of visual multiple stars were taken in 2008–2009 to detect or confirm spectroscopic subsystems and to determine their orbits. Radial velocities of 93 late-type stars belonging to visual multiple systems were measured by numerical cross-correlation. We provide the individual velocities, the width, and the amplitude of the Gaussians that approximate the correlations. The new information on the multiple systems resulting from these data is discussed. We discovered double-lined binaries in HD 41742B, HD 56593C, and HD 122613AB, confirmed several other known subsystems, and constrained the existence of subsystems in some visual binaries where both components turned out to have similar velocities. The orbits of double-lined subsystems with periods of 148 and 13 days are computed for HD 104471 Aa,Ab and HD 210349 Aa,Ab, respectively. We estimate individual magnitudes and masses of the components in these triple systems and update the outer orbit of HD 104471 AB.

  14. Constraints on the structure of the core of subgiants via mixed modes: the case of HD 49385

    NASA Astrophysics Data System (ADS)

    Deheuvels, S.; Michel, E.

    2011-11-01

    Context. The solar-like pulsator HD 49385 was observed with the CoRoT satellite over a period of 137 days. The analysis of its oscillation spectrum yielded precise estimates of the mode frequencies over nine radial orders and distinguished some unusual characteristics, such as some modes outside the identified ridges in the échelle diagram and that the curvature of the ℓ = 1 ridge differs significantly from that of the ℓ = 0 ridge. Aims: We search for stellar models that can reproduce the peculiar features of the oscillation spectrum of HD 49385. After showing that they can be accounted for only by a low-frequency ℓ = 1 avoided crossing, we investigate the information provided by the mixed modes about the structure of the core of HD 49385. Methods: We propose a toy-model to study the case of avoided crossings with a strong coupling between the p-mode and g-mode cavities in order to establish the presence of mixed modes in the spectrum of HD 49385. We then show that traditional optimization techniques are ill-suited to stars with mixed modes in avoided crossing. We propose a new approach to the computation of grids of models that we apply to HD 49385. Results: The detection of mixed modes leads us to establish the post-main-sequence status of HD 49385. The mixed mode frequencies suggest that there is a strong coupling between the p-mode and g-mode cavities. As a result, we show that the amount of core overshooting in HD 49385 is either very small (0 < αov < 0.05) or moderate (0.18 < αov < 0.20). The mixing length parameter is found to be significantly lower than the solar one (αCGM = 0.55 ± 0.04 compared to the solar value α⊙ = 0.64). Finally, we show that the revised solar abundances of Asplund ensure closer agreement with the observations than the classical ones of Grevesse & Noels. At each step, we investigate the origin and meaning of these seismic diagnostics in terms of the physical structure of the star. Conclusions: The subgiant HD 49385 is the

  15. The N2K Consortium. I. A Hot Saturn Planet Orbiting HD 88133

    NASA Astrophysics Data System (ADS)

    Fischer, Debra A.; Laughlin, Greg; Butler, Paul; Marcy, Geoff; Johnson, John; Henry, Greg; Valenti, Jeff; Vogt, Steve; Ammons, Mark; Robinson, Sarah; Spear, Greg; Strader, Jay; Driscoll, Peter; Fuller, Abby; Johnson, Teresa; Manrao, Elizabeth; McCarthy, Chris; Muñoz, Melesio; Tah, K. L.; Wright, Jason; Ida, Shigeru; Sato, Bun'ei; Toyota, Eri; Minniti, Dante

    2005-02-01

    The N2K (``next 2000'') consortium is carrying out a distributed observing campaign with the Keck, Magellan, and Subaru telescopes, as well as the automatic photometric telescopes of Fairborn Observatory, in order to search for short-period gas giant planets around metal-rich stars. We have established a reservoir of more than 14,000 main-sequence and subgiant stars closer than 110 pc, brighter than V=10.5, and with 0.4stars with planets is a sensitive function of stellar metallicity, a broadband photometric calibration has been developed to identify a subset of 2000 stars with [Fe/H]>0.1 dex for this survey. We outline the strategy and report the detection of a planet orbiting the metal-rich G5 IV star HD 88133 with a period of 3.41 days, semivelocity amplitude K=35.7 m s-1, and Msini=0.29MJ. Photometric observations reveal that HD 88133 is constant on the 3.415 day radial velocity period to a limit of 0.0005 mag. Despite a transit probability of 19.5%, our photometry rules out the shallow transits predicted by the large stellar radius. Based on observations obtained at the W. M. Keck Observatory, which is operated by the University of California and the California Institute of Technology. Keck time has been granted by NOAO and NASA.

  16. Evolutionary status of isolated B[e] stars

    NASA Astrophysics Data System (ADS)

    Lee, Chien-De; Chen, Wen-Ping; Liu, Sheng-Yuan

    2016-08-01

    Aims: We study a sample of eight B[e] stars with uncertain evolutionary status to shed light on the origin of their circumstellar dust. Methods: We performed a diagnostic analysis on the spectral energy distribution beyond infrared wavelengths, and conducted a census of neighboring region of each target to ascertain its evolutionary status. Results: In comparison to pre-main sequence Herbig stars, these B[e] stars show equally substantial excess emission in the near-infrared, indicative of existence of warm dust, but much reduced excess at longer wavelengths, so the dusty envelopes should be compact in size. Isolation from star-forming regions excludes the possibility of their pre-main sequence status. Six of our targets, including HD 50138, HD 45677, CD-24 5721, CD-49 3441, MWC 623, and HD 85567, have been previously considered as FS CMa stars, whereas HD 181615/6 and HD 98922 are added to the sample by this work. We argue that the circumstellar grains of these isolated B[e] stars, already evolved beyond the pre-main sequence phase, should be formed in situ. This is in contrast to Herbig stars, which inherit large grains from parental molecular clouds. It has been thought that HD 98922, in particular, is a Herbig star because of its large infrared excess, but we propose it being in a more evolved stage. Because dust condenses out of stellar mass loss in an inside-out manner, the dusty envelope is spatially confined, and anisotropic mass flows, or anomalous optical properties of tiny grains, lead to the generally low line-of-sight extinction toward these stars.

  17. IUE observations of new A star candidate proto-planetary systems

    NASA Technical Reports Server (NTRS)

    Grady, Carol A.

    1994-01-01

    As a result of the detection of accreting gas in the A5e PMS Herbig Ae star, HR 5999, most of the observations for this IUE program were devoted to Herbig Ae stars rather than to main sequence A stars. Mid-UV emission at optical minimum light was detected for UX Ori (A1e), BF Ori (A5e), and CQ Tau (F2e). The presence of accreting gas in HD 45677 and HD 50138 prompted reclassification of these stars as Herbig Be stars rather than as protoplanetary nebulae. Detailed results are discussed.

  18. HD209458b Transit Spectroscopy

    NASA Astrophysics Data System (ADS)

    Harrington, J.; Deming, L. D.; Matthews, K.; Richardson, L. J.; Rojo, P.; Steyert, D.; Wiedemann, G.; Zeehandelaar, D.

    2002-09-01

    We search for the spectral signature of H2O, CH4, and CO on the extrasolar planet HD 209458b using transit spectroscopy. The planet will modulate the stellar spectrum during transit. The extinction altitude of tangent rays of a given wavelength depends on the abundance and distribution of molecular species that absorb at that wavelength. The depth of the occultation at a given wavelength depends on the cross-sectional area of the planet, which is determined by the extinction altitude. For deep lines of H2O, CH4, and CO, the effect is about 0.07%, due to the ~750 km scale height. Our S/N calculations show that well-calibrated, ground-based spectra, integrated over time and wavelength, can measure or place useful limits on the atmospheric abundances of H2O, CH4, and CO. Carbon forms predominantly CH4 below 1400 K and CO if hotter. Since the effective temperature is around 1400 K, detecting CH4 and/or CO would provide a tight constraint on atmospheric temperatures. Observations began in August 2001 at Palomar and we have 12 additional nights granted in 2002 at Keck, VLT, and IRTF. The expected modulation of the stellar spectrum is model-dependent: high-altitude hazes, photochemical effects, and different thermal profiles would substantially modify the effect for the same planetary elemental abundances. Since the effect is subtle compared to the noise in the data, we correlate model spectra against thousands of observed spectra and average the correlations to test whether the data support a given model. We are developing a radiative-transfer model to predict the spectrum of a given planetary model, and we are measuring H2O, CH4, and CO in the laboratory at 1300 K, with pressure-broadening by H2, to make our model spectra realistic at these elevated temperatures (crucial for detecting H2O). Analysis of the 2001 data and acquisition of 2002 data are in progress. We solicit participation by those who wish to test their planetary models.

  19. HD 100453: A Link Between Gas-Rich Protoplanetary Disks and Gas-Poor Debris Disks

    NASA Astrophysics Data System (ADS)

    Collins, K. A.; Grady, C. A.; Hamaguchi, K.; Wisniewski, J. P.; Brittain, S.; Sitko, M.; Carpenter, W. J.; Williams, J. P.; Mathews, G. S.; Williger, G. M.; van Boekel, R.; Carmona, A.; Henning, Th.; van den Ancker, M. E.; Meeus, G.; Chen, X. P.; Petre, R.; Woodgate, B. E.

    2009-05-01

    HD 100453 has an IR spectral energy distribution (SED) which can be fit with a power law plus a blackbody. Previous analysis of the SED suggests that the system is a young Herbig Ae star with a gas-rich, flared disk. We reexamine the evolutionary state of the HD 100453 system by refining its age (based on a candidate low-mass companion) and by examining limits on the disk extent, mass accretion rate, and gas content of the disk environment. We confirm that HD 100453B is a common proper motion companion to HD 100453A, with a spectral type of M4.0V-M4.5V, and derive an age of 10 ± 2 Myr. We find no evidence of mass accretion onto the star. Chandra ACIS-S imagery shows that the Herbig Ae star has L x/L bol and an X-ray spectrum similar to nonaccreting β Pic Moving Group early F stars. Moreover, the disk lacks the conspicuous Fe II emission and excess FUV continuum seen in spectra of actively accreting Herbig Ae stars, and from the FUV continuum, we find the accretion rate is < 1.4 × 10-9 M sun yr-1. A sensitive upper limit to the CO J = 3-2 intensity indicates that the gas in the outer disk is likely optically thin. Assuming a [CO]/[H2] abundance of 1 × 10-4 and a depletion factor of 103, we find that the mass of cold molecular gas is less than ~0.33 M J and that the gas-to-dust ratio is no more than ~4:1 in the outer disk. The combination of a high fractional IR excess luminosity, a relatively old age, an absence of accretion signatures, and an absence of detectable circumstellar molecular gas suggests that the HD 100453 system is in an unusual state of evolution between a gas-rich protoplanetary disk and a gas-poor debris disk.

  20. HD 240121 - An ACV variable showing anti-phase variations of the B and V light curves

    NASA Astrophysics Data System (ADS)

    Gröbel, Rainer; Hümmerich, Stefan; Paunzen, Ernst; Bernhard, Klaus

    2017-01-01

    The variability of HD 240121 = BD+59 2602 was first suspected by Särg and Wramdemark (1970) and later confirmed by Gröbel R. (1992a,b). Because of the observed anti-phase variations of the B and V light curves, the latter author tentatively suggested an ACV type. Apart from its inclusion in the catalog of New Suspected Variables (NSV 25977), no further investigations of the star have been published. HD 240121 was included into our target list of ACV candidates and investigated in order to determine the reason for the observed brightness variations. All available information on HD 240121 were collected via an exhaustive data mining procedure. Data from Gröbel (1992a,b) were re-analysed and photometric observations from the NSVS and Hipparcos archives were procured and investigated. Line-of-sight reddening and stellar parameters were calculated from archival photometric data. HD 240121 is a young, late B-type CP2 star of the silicon subgroup. The observed period, amplitude of light variations and variability pattern (anti-phase variations) are typical of ACV variables. The occurrence of anti-phase variations of the B and V light curves is rarely observed and points to the existence of a null wavelength in the visual spectrum. We therefore strongly encourage further multi-colour photometric observations of this star.

  1. Subaru Near-Infrared Imaging of Herbig Ae Stars

    NASA Astrophysics Data System (ADS)

    Fukagawa, Misato; Tamura, Motohide; Itoh, Yoichi; Oasa, Yumiko; Kudo, Tomoyuki; Hayashi, Saeko S.; Kato, Eri; Ootsubo, Takafumi; Itoh, Yusuke; Shibai, Hiroshi; Hayashi, Masahiko

    2010-04-01

    We report results of H-band (λ = 1.65μm) imaging observations of young intermediate-mass stars using the Subaru 8.2-m Telescope with the adaptive optics AO36 and the infrared coronagraph CIAO. The targets consist of 16 Herbig Ae/Be stars (15 Herbig Ae stars and one Herbig Be star) and four additional main-sequence stars with infrared excesses. Five protoplanetary disks have been spatially resolved around the Herbig Ae stars with ages of 2-8 Myr. The resolved disks have outer radii of several 100 AU, and their surface brightnesses range from 10 mag arcsec-2 to 18 mag arcsec-2. The images reveal various morphologies in optically thick disks: spiral arms around AB Aur, a banana-split structure with an outer arm for HD 142527, a compact circumprimary disk of HD 150193, a faint discontinuous ring around HD 163296, and an unstructured face-on disk of HD 169142. The detection of an optically thick disk in scattered light implies that it is vertically flared, and intercepts stellar light at least in the outer region where those images were obtained. However, the surface brightness distribution, the resolved structure, and other observational characteristics suggest that the disks are unlikely to be continuously flared young disks with small grains well mixed with gas. The detection rate and the disk brightness do not correlate with the stellar age and the disk mass, but there is a tendency that the brightest disks are still surrounded by long-lived envelopes (AB Aur, HD 100546, HD 142527). The significant diversity of the disk structure can be attributed to the multiplicity and the initial condition of the local star-forming environments. The detections of companion candidates around our targeted stars are also reported.

  2. HD Therapeutics - CHDI Fifth Annual Conference.

    PubMed

    Gagnon, Keith T

    2010-04-01

    The CHDI Fifth Annual HD Therapeutics Conference, held in Palm Springs, CA, included topics covering new therapeutic developments in the field of Huntington's disease (HD). This conference report highlights presentations on biomarkers in HD; emerging topics in drug targeting, such as the lysosomal degradation pathway and target prediction by network-based modeling; understanding phenotype and neuronal circuit dysfunction in animal models; regulation of huntingtin protein expression and function; RNAi and antisense technology to deplete the mutant huntingtin protein; and small-molecule drugs that are progressing quickly through the clinic. Investigational drugs discussed include ALN-HTT (Alnylam Pharmaceuticals Inc/Medtronic Inc), EPI-743 (Edison Pharmaceuticals Inc), LNK-754 (Link Medicine Corp) and pridopidine (NeuroSearch A/S).

  3. The Mass of HD 38529c from Hubble Space Telescope Astrometry and High-precision Radial Velocities

    NASA Astrophysics Data System (ADS)

    Benedict, G. Fritz; McArthur, Barbara E.; Bean, Jacob L.; Barnes, Rory; Harrison, Thomas E.; Hatzes, Artie; Martioli, Eder; Nelan, Edmund P.

    2010-05-01

    Hubble Space Telescope Fine Guidance Sensor astrometric observations of the G4 IV star HD 38529 are combined with the results of the analysis of extensive ground-based radial velocity (RV) data to determine the mass of the outermost of two previously known companions. Our new RVs obtained with the Hobby-Eberly Telescope and velocities from the Carnegie-California group now span over 11 yr. With these data we obtain improved RV orbital elements for both the inner companion, HD 38529b, and the outer companion, HD 38529c. We identify a rotational period of HD 38529 (P rot = 31.65 ± 0fd17) with Fine Guidance Sensor photometry. The inferred star spot fraction is consistent with the remaining scatter in velocities being caused by spot-related stellar activity. We then model the combined astrometric and RV measurements to obtain the parallax, proper motion, perturbation period, perturbation inclination, and perturbation size due to HD 38529c. For HD 38529c we find P = 2136.1 ± 0.3 d, perturbation semimajor axis α = 1.05 ± 0.06 mas, and inclination i = 48fdg3 ± 3fdg7. Assuming a primary mass M * = 1.48 M sun, we obtain a companion mass Mc = 17.6+1.5 -1.2 M Jup, 3σ above a 13 M Jup deuterium burning, brown dwarf lower limit. Dynamical simulations incorporating this accurate mass for HD 38529c indicate that a near-Saturn mass planet could exist between the two known companions. We find weak evidence of an additional low amplitude signal that can be modeled as a planetary-mass (~0.17 M Jup) companion at P ~194 days. Including this component in our modeling lowers the error of the mass determined for HD 38529c. Additional observations (RVs and/or Gaia astrometry) are required to validate an interpretation of HD 38529d as a planetary-mass companion. If confirmed, the resulting HD 38529 planetary system may be an example of a "Packed Planetary System." Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute

  4. No hydrogen exosphere detected around the super-Earth HD 97658 b

    NASA Astrophysics Data System (ADS)

    Bourrier, V.; Ehrenreich, D.; King, G.; Lecavelier des Etangs, A.; Wheatley, P. J.; Vidal-Madjar, A.; Pepe, F.; Udry, S.

    2017-01-01

    The exoplanet HD 97658 b provides a rare opportunity to probe the atmospheric composition and evolution of moderately irradiated super-Earths. It transits a bright K star at a moderate orbital distance of 0.08 au. Its low density is compatible with a massive steam envelope that could photodissociate at high altitudes and become observable as escaping neutral hydrogen. Our analysis of three transits with HST/STIS at Lyman-α reveals no such signature, suggesting that the thermosphere of HD 97658 b is not hydrodynamically expanding and is subjected to a low escape of neutral hydrogen (<108 g s-1 at 3σ). Using HST/STIS Lyman-α observations and Chandra/ACIS-S and XMM-Newton/EPIC X-ray observations at different epochs, we find that HD 97658 is in fact a weak and soft X-ray source with signs of chromospheric variability in the Lyman-α line core. We determine an average reference for the intrinsic Lyman-α line and X-EUV (XUV) spectrum of the star, and show that HD 97658 b is in mild conditions of irradiation compared to other known evaporating exoplanets with an XUV irradiation about three times lower than the evaporating warm Neptune GJ436 b. This could be the reason why the thermosphere of HD 97658 b is not expanding: the low XUV irradiation prevents an efficient photodissociation of any putative steam envelope. Alternatively, it could be linked to a low hydrogen content or inefficient conversion of the stellar energy input. The HD 97658 system provides clues for understanding the stability of low-mass planet atmospheres in terms of composition, planetary density, and irradiation. Our study of HD 97658 b can be seen as a control experiment of our methodology, confirming that it does not bias detections of atmospheric escape and underlining its strength and reliability. Our results show that stellar activity can be efficiently discriminated from absorption signatures by a transiting exospheric cloud. They also highlight the potential of observing the upper atmosphere

  5. A Gemini Planet Imager investigation of the atmosphere of the HD 95086b planet

    NASA Astrophysics Data System (ADS)

    De Rosa, Robert J.; Pueyo, Laurent; Patience, Jenny; Graham, James R.; Gemini Planet Imager Team

    2015-01-01

    We present Gemini Planet Imager (GPI) near-infrared observations of the ~5 Mjup companion to the young, dusty A-type star HD 95086, observed during the course of the verification and commissioning of the instrument. By combining binned low-resolution H and K-band IFS spectra from GPI, with literature near and mid-IR photometry, we have undertaken the most comprehensive analysis of the spectral energy distribution of HD 95086 b to-date. Comparing these observational results with atmospheric models, we constrain key parameters such as the effective temperature and surface gravity, and place the results in the context of analyses of other directly imaged planetary-mass companions (e.g. HR 8799 bcde, β Pic b), and other substellar companions at a similar age (e.g. HD 106906 b, GQ Lup b). We also comment on the sensitivity of companions interior and exterior to HD 95086 b. Lastly, we present the color-corrections derived during the course of this study that are required to transform photometry obtained with GPI in the K1 and K2 filters into both the MKO and 2MASS photometric systems, essential for the propoer interpretation of K-band photometry measurements obtained with GPI.

  6. An M Dwarf Companion and Its Induced Spiral Arms in the HD 100453 Protoplanetary Disk

    NASA Astrophysics Data System (ADS)

    Dong, Ruobing; Zhu, Zhaohuan; Fung, Jeffrey; Rafikov, Roman; Chiang, Eugene; Wagner, Kevin

    2016-01-01

    Recent VLT/SPHERE near-infrared imaging observations revealed two spiral arms with a near m = 2 rotational symmetry in the protoplanetary disk around the ˜1.7 M⊙ Herbig star HD 100453. A ˜0.3 M⊙ M dwarf companion, HD 100453 B, was also identified at a projected separation of 120 AU from the primary. In this Letter, we carry out hydrodynamic and radiative transfer simulations to examine the scattered light morphology of the HD 100453 disk as perturbed by the companion on a circular and coplanar orbit. We find that the companion truncates the disk at ˜45 AU in scattered light images, and excites two spiral arms in the remaining (circumprimary) disk with a near m = 2 rotational symmetry. Both the truncated disk size and the morphology of the spirals are in excellent agreement with the SPHERE observations at Y, J, H, and K1-bands, suggesting that the M dwarf companion is indeed responsible for the observed double-spiral-arm pattern. Our model suggests that the disk is close to face on (inclination angle ˜5°), and that the entire disk-companion system rotates counterclockwise on the sky. The HD 100453 observations, along with our modeling work, demonstrate that double spiral arm patterns in near-infrared scattered light images can be generically produced by companions, and support future observations to identify the companions responsible for the arms observed in the MWC 758 and SAO 206462 systems.

  7. The peculiar object HD 44179 /'The red rectangle'/

    NASA Technical Reports Server (NTRS)

    Cohen, M.; Fawley, W. M.; Anderson, C. M.; Cowley, A.; Coyne, G. V.; Gull, T. R.; Harlan, E. A.; Herbig, G. H.; Holden, F.; Hudson, H. S.

    1975-01-01

    A strong infrared source detected in the AFCRL sky survey is confirmed, and is identified with the binary star HD 44179, embedded in a peculiar nebula. UBVRI and broad-band photometry between 2.2 and 27 microns are combined with blue, red, and near-infrared spectra, polarimetry and spectrophotometry of the star, and a range of direct and image-tube photographs of the nebula, to suggest a composite model of the system. In this model, the infrared radiation derives from thermal emission by dust grains contained in a disklike geometry about the central object, which appears to be of spectral type B9-A0 III and which may be in pre-main-sequence evolution. Two infrared emission features are found, peaking at 8.7 and 11.3 microns, the latter corresponding to the feature seen in the spectrum of the planetary nebula NGC 7027. The complex nebular structure is discussed on the basis of photographs through narrow-band continuum and emission-line filters. The polarization data support the suggestion of a disk containing some large particles. No radio continuum emission is detected.

  8. IMPROVED ORBITAL PARAMETERS AND TRANSIT MONITORING FOR HD 156846b

    SciTech Connect

    Kane, Stephen R.; Von Braun, Kaspar; Ciardi, David R.; Dragomir, Diana; Ramirez, Solange V.; Howard, Andrew W.; Pilyavsky, Genady; Mahadevan, Suvrath; Wright, Jason T.; Henry, Gregory W.; Fischer, Debra A.; Jensen, Eric; Laughlin, Gregory

    2011-05-20

    HD 156846b is a Jovian planet in a highly eccentric orbit (e = 0.85) with a period of 359.55 days. The pericenter passage at a distance of 0.16 AU is nearly aligned to our line of sight, offering an enhanced transit probability of 5.4% and a potentially rich probe of the dynamics of a cool planetary atmosphere impulsively heated during close approach to a bright star (V = 6.5). We present new radial velocity (RV) and photometric measurements of this star as part of the Transit Ephemeris Refinement and Monitoring Survey. The RV measurements from the Keck-High Resolution Echelle Spectrometer reduce the predicted transit time uncertainty to 20 minutes, an order of magnitude improvement over the ephemeris from the discovery paper. We photometrically monitored a predicted transit window under relatively poor photometric conditions, from which our non-detection does not rule out a transiting geometry. We also present photometry that demonstrates stability at the millimagnitude level over its rotational timescale.

  9. Detection of Arsenic in the Atmospheres of Dying Stars

    NASA Astrophysics Data System (ADS)

    Chayer, Pierre; Dupuis, Jean; Kruk, Jeffrey W.

    2015-06-01

    We report the detection of As V resonance lines observed in the Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of three hot DA white dwarfs: G191-B2B, WD 0621-376, and WD 2211-495. The stars have effective temperatures ranging from 60,000 K to 64,000 K and are among the most metal-rich white dwarfs known. We measured the arsenic abundances not only in these stars, but also in three DO stars in which As has been detected before: HD 149499 B, HZ 21, and RE 0503-289. The arsenic abundances observed in the DA stars are very similar. This suggests that radiative levitation may be the mechanism that supports arsenic. The arsenic abundance in HZ 21 is significantly lower than that observed in HD 149499 B, even though the stars have similar atmospheric parameters. An additional mechanism may be at play in the atmospheres of these two DO stars.

  10. High-resolution abundance analysis of HD 140283

    NASA Astrophysics Data System (ADS)

    Siqueira-Mello, C.; Andrievsky, S. M.; Barbuy, B.; Spite, M.; Spite, F.; Korotin, S. A.

    2015-12-01

    Context. HD 140283 is a reference subgiant that is metal poor and confirmed to be a very old star. The element abundances of this type of old star can constrain the nature and nucleosynthesis processes that occurred in its (even older) progenitors. The present study may shed light on nucleosynthesis processes yielding heavy elements early in the Galaxy. Aims: A detailed analysis of a high-quality spectrum is carried out, with the intent of providing a reference on stellar lines and abundances of a very old, metal-poor subgiant. We aim to derive abundances from most available and measurable spectral lines. Methods: The analysis is carried out using high-resolution (R = 81 000) and high signal-to-noise ratio (800 Stars (ESPaDOnS) at the Canada-France-Hawaii Telescope (CFHT). The calculations in local thermodynamic equilibrium (LTE) were performed with a OSMARCS 1D atmospheric model and the spectrum synthesis code Turbospectrum, while the analysis in non-LTE (NLTE) is based on the MULTI code. We present LTE abundances for 26 elements, and NLTE calculations for the species C i, O i, Na i, Mg i, Al i, K i, Ca i, Sr ii, and Ba ii lines. Results: The abundance analysis provided an extensive line list suitable for metal-poor subgiant stars. The results for Li, CNO, α-, and iron peak elements are in good agreement with literature. The newly NLTE Ba abundance, along with a NLTE Eu correction and a 3D Ba correction from literature, leads to [Eu/Ba] = + 0.59 ± 0.18. This result confirms a dominant r-process contribution, possibly together with a very small contribution from the main s-process, to the neutron-capture elements in HD 140283. Overabundances of the lighter heavy elements and the high abundances derived for Ba, La, and Ce favour the operation of the weak r-process in HD 140283

  11. B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid nebula, one of the youngest star forming regions

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; Fossati, L.; Carroll, T. A.; Castro, N.; González, J. F.; Ilyin, I.; Przybilla, N.; Schöller, M.; Oskinova, L. M.; Morel, T.; Langer, N.; Scholz, R. D.; Kharchenko, N. V.; Nieva, M.-F.

    2014-04-01

    Aims: Recent magnetic field surveys in O- and B-type stars revealed that about 10% of the core-hydrogen-burning massive stars host large-scale magnetic fields. The physical origin of these fields is highly debated. To identify and model the physical processes responsible for the generation of magnetic fields in massive stars, it is important to establish whether magnetic massive stars are found in very young star-forming regions or whether they are formed in close interacting binary systems. Methods: In the framework of our ESO Large Program, we carried out low-resolution spectropolarimetric observations with FORS 2 in 2013 April of the three most massive central stars in the Trifid nebula, HD 164492A, HD 164492C, and HD 164492D. These observations indicated a strong longitudinal magnetic field of about 500-600 G in the poorly studied component HD 164492C. To confirm this detection, we used HARPS in spectropolarimetric mode on two consecutive nights in 2013 June. Results: Our HARPS observations confirmed the longitudinal magnetic field in HD 164492C. Furthermore, the HARPS observations revealed that HD 164492C cannot be considered as a single star as it possesses one or two companions. The spectral appearance indicates that the primary is most likely of spectral type B1-B1.5 V. Since in both observing nights most spectral lines appear blended, it is currently unclear which components are magnetic. Long-term monitoring using high-resolution spectropolarimetry is necessary to separate the contribution of each component to the magnetic signal. Given the location of the system HD 164492C in one of the youngest star formation regions, this system can be considered as a Rosetta Stone for our understanding of the origin of magnetic fields in massive stars. Based on observations obtained in the framework of the ESO Prg. 191.D-0255(A,B).

  12. THE ANGLO-AUSTRALIAN PLANET SEARCH. XX. A SOLITARY ICE-GIANT PLANET ORBITING HD 102365

    SciTech Connect

    Tinney, C. G.; Wittenmyer, Robert A.; Bailey, Jeremy; Butler, R. Paul; Jones, Hugh R. A.; O'Toole, Simon; Carter, Brad D.

    2011-02-01

    We present 12 years of precision Doppler data for the very nearby G3 star HD 102365, which reveals the presence of a Neptune-like planet with a 16.0 M{sub Earth} minimum mass in a 122.1 day orbit. Very few 'Super Earth' planets have been discovered to date in orbits this large and those that have been found reside in multiple systems of between three and six planets. HD 102365 b, in contrast, appears to orbit its star in splendid isolation. Analysis of the residuals to our Keplerian fit for HD 102365 b indicates that there are no other planets with minimum mass above 0.3 M{sub Jup} orbiting within 5 AU and no other 'Super Earths' more massive than 10 M{sub Earth} orbiting at periods shorter than 50 days. At periods of less than 20 days these limits drop to as low as 6 M{sub Earth}. There are now 32 exoplanets known with minimum mass below 20 M{sub Earth}, and interestingly the period distributions of these low-mass planets seem to be similar whether they orbit M-, K-, or G-type dwarfs.

  13. The Anglo-Australian Planet Search. XXV. A Candidate Massive Saturn Analog Orbiting HD 30177

    NASA Astrophysics Data System (ADS)

    Wittenmyer, Robert A.; Horner, Jonathan; Mengel, M. W.; Butler, R. P.; Wright, D. J.; Tinney, C. G.; Carter, B. D.; Jones, H. R. A.; Anglada-Escudé, G.; Bailey, J.; O’Toole, Simon J.

    2017-04-01

    We report the discovery of a second long-period giant planet orbiting HD 30177, a star previously known to host a massive Jupiter analog (HD 30177b: a = 3.8 ± 0.1 au, m sin i = 9.7 ± 0.5 M Jup). HD 30177c can be regarded as a massive Saturn analog in this system, with a = 9.9 ± 1.0 au and m sin i = 7.6 ± 3.1 M Jup. The formal best-fit solution slightly favors a closer-in planet at a ∼ 7 au, but detailed n-body dynamical simulations show that configuration to be unstable. A shallow local minimum of longer period, lower eccentricity solutions was found to be dynamically stable, and hence we adopt the longer period in this work. The proposed ∼32 year orbit remains incomplete; further monitoring of this and other stars is necessary to reveal the population of distant gas giant planets with orbital separations a ∼ 10 au, analogous to that of Saturn.

  14. Subaru/HDS study of CH stars: elemental abundances for stellar neutron-capture process studies

    NASA Astrophysics Data System (ADS)

    Goswami, Aruna; Aoki, Wako; Karinkuzhi, Drisya

    2016-01-01

    A comprehensive abundance analysis providing rare insight into the chemical history of lead stars is still lacking. We present results from high-resolution (R ˜ 50 000) spectral analyses of three CH stars, HD 26, HD 198269 and HD 224959, and, a carbon star with a dusty envelope, HD 100764. Previous studies on these objects are limited by both resolution and wavelength regions and the results differ significantly from each other. We have undertaken to reanalyse the chemical composition of these objects based on high-resolution Subaru spectra covering the wavelength regions 4020-6775 Å. Considering local thermodynamic equilibrium and using model atmospheres, we have derived the stellar parameters, the effective temperatures Teff, surface gravities log g, and metallicities [Fe/H] for these objects. The derived parameters for HD 26, HD 100764, HD 198269 and HD 224959 are (5000, 1.6, -1.13), (4750, 2.0 -0.86), (4500, 1.5, -2.06) and (5050, 2.1, -2.44), respectively. The stars are found to exhibit large enhancements of heavy elements relative to iron in conformity to previous studies. Large enhancement of Pb with respect to iron is also confirmed. Updates on the elemental abundances for several s-process elements (Y, Zr, La, Ce, Nd, Sm and Pb) along with the first-time estimates of abundances for a number of other heavy elements (Sr, Ba, Pr, Eu, Er and W) are reported. Our analysis suggests that neutron-capture elements in HD 26 primarily originate in the s-process while the major contributions to the abundances of neutron-capture elements in the more metal-poor objects HD 224959 and HD 198269 are from the r-process, possibly from materials that are pre-enriched with products of the r-process.

  15. Toward Understanding The B[e] Phenomenon. VI. Nature and Spectral Variations of HD 85567.

    NASA Astrophysics Data System (ADS)

    Khokhlov, S. A.; Miroshnichenko, A. S.; Mennickent, R.; Cabezas, M.; Zhanabaev, Z. Zh.; Reichart, D. E.; Ivarsen, K. M.; Haislip, J. B.; Nysewander, M. C.; LaCluyze, A. P.

    2017-01-01

    We report the results of high-resolution (R ∼ 80,000) spectroscopic observations of the emission-line object HD 85567, which has been classified as an FS CMa type object or a pre-main-sequence star. The main goal is to put more constraints on the object’s fundamental parameters, as well as on its nature and evolutionary state. Absorption lines in the spectrum of HD 85567 were found to be similar to those of mid-B-type dwarfs and correspond to the following fundamental parameters: Teff = 15,000 ± 500 K, v\\sin i=31+/- 3 km s‑1, and {log} g∼ 4.0. The interstellar extinction, AV = 0.50 ± 0.02 mag, was measured using the strengths of some diffuse interstellar bands. We also obtained UBV(RI)c images of a 10‧ × 10‧ region around the object. Photometry of projectionally close stars was used to derive an interstellar extinction law in this direction and resulted in a distance of 1300 ± 100 pc to the object and a luminosity of log L/L⊙ = 3.3 ± 0.2. We found no significant radial velocity variations of the absorption lines in the spectra of HD 85567 obtained during two-month-long periods of time in 2012 and 2015. Our analysis of the spectroscopic and photometric data available for the star led us to a conclusion that it cannot be a pre-main-sequence Herbig Ae/Be star. We argue that the circumstellar gas and dust were produced during the object’s evolution as most likely a binary system, which contains an undetected secondary component and is unlikely to be a merger product. This paper is partly based on observations obtained at the 1.5 m telescope of the Cerro Tololo Interamerican Observatory under CNTAC proposal 2012A–016.

  16. Quantum defect analysis of HD photoionization

    SciTech Connect

    Du, N.Y.; Greene, C.H.

    1986-11-15

    A multichannel quantum defect calculation is shown to reproduce most observed features in several portions of the HD photoabsorption spectrum. The rovibrational frame transformation theory of Atabek, Dill, and Jungen is reformulated in terms of a quantum defect matrix. The calculation accounts for spectral regions far from dissociation thresholds despite its neglect of g--u mixing.

  17. Documentation for the machine-readable version of the general catalogue of 33342 stars for the epoch 1950 (Boss 1937)

    NASA Technical Reports Server (NTRS)

    Roman, N. G.; Warren, W. H., Jr.

    1983-01-01

    A revised and corrected version of the machine-readable catalog has been prepared. Cross identifications of the GC stars to the HD and DM catalogs have been replaced by data from the new SAO-HD-GC-DM Cross Index (Roman, Warren and Schofield 1983), including component identifications for multiple SAO entries having identical DM numbers in the SAO Catalog, supplemental Bonner Durchmusterung stars (lower case letter designations) and codes for multiple HD stars. Additional individual corrections have been incorporated based upon errors found during analyses of other catalogs.

  18. Gas Modelling in the Disc of HD 163296

    NASA Technical Reports Server (NTRS)

    Tilling, I.; Woitke, P.; Meeus, G.; Mora, A.; Montesinos, B.; Riviere-Marichalar, P.; Eiroa, C.; Thi, W. -F.; Isella, A.; Roberge, A.; Martin-Zaidi, C.; Kamp, I.; Pinte, C.; Sandell, G.; Vacca, W. D.; Menard, F.; Mendigutia, I.; Duchene, G.; Dent, W. R. F.; Aresu, G.; Meijerink, R.; Spaans, M.

    2011-01-01

    We present detailed model fits to observations of the disc around the Herbig Ae star HD 163296. This well-studied object has an age of approx. 4Myr, with evidence of a circumstellar disc extending out to approx. 540AU. We use the radiation thermo-chemical disc code ProDiMo to model the gas and dust in the circumstellar disc of HD 163296, and attempt to determine the disc properties by fitting to observational line and continuum data. These include new Herschel/PACS observations obtained as part of the open-time key program GASPS (Gas in Protoplanetary Systems), consisting of a detection of the [Oi] 63 m line and upper limits for several other far infrared lines. We complement this with continuum data and ground-based observations of the CO-12 3-2, 2-1 and CO-13 J=1-0 line transitions, as well as the H2 S(1) transition. We explore the effects of stellar ultraviolet variability and dust settling on the line emission, and on the derived disc properties. Our fitting efforts lead to derived gas/dust ratios in the range 9-100, depending on the assumptions made. We note that the line fluxes are sensitive in general to the degree of dust settling in the disc, with an increase in line flux for settled models. This is most pronounced in lines which are formed in the warm gas in the inner disc, but the low excitation molecular lines are also affected. This has serious implications for attempts to derive the disc gas mass from line observations. We derive fractional PAH abundances between 0.007 and 0.04 relative to ISM levels. Using a stellar and UV excess input spectrum based on a detailed analysis of observations, we find that the all observations are consistent with the previously assumed disc geometry

  19. Optical studies of X-ray peculiar chromosphereically active stars

    NASA Astrophysics Data System (ADS)

    Pandey, J. C.

    2006-02-01

    A multiwavelength study of the late-type active stars, selected on the basis of their X-ray and radio luminosities is presented in this thesis. For FR Cnc, a photometric period 0.8267 +/- 0.0004 d has been established. The strong variation in the phase and amplitude of the FR Cnc light curves when folded on this period implies the presence of evolving and migrating spots or spot groups on its surface. A photometric period of 18.802 +/- 0.074 has been discovered in the star HD 81032. The shape and amplitude of the photometric light curves of FR Cnc, HD 81032, HD 95559 and LO Peg are observed to be changing from one epoch to another. The change in the amplitude is mainly due to a change in the minimum of the light curve, and this May be due to a change in the spot coverage. This indicates that photometric variability is due to the presence of dark spots on the surface of active star. Two groups of spots are identified for FR Cnc and LO Peg. The spots are found to migrate, and migration periods of 0.97 year and 0.93 year are determined from the 4 years of data. A migration period of 1.12 years for one group of spots in LO Peg is also determined. Formation of a new group of spots in the star HD 95559 was also seen during our observations. A single large group of spots is found to migrate, and a migration period of 7.32 +/- 0.04 years is determined for HD 81032. The stars FR Cnc, HD 81032, HD 160934 and LO Peg are seen to be redder at the light minimum and we interpret this is due to the relatively cooler temperature of the darker regions present in the visible hemisphere. We find the lack of color-brightness correlation in the star HD 95559 and this May be due to the presence of bright faculae and plages like regions accompanied by dark spots in any one component of the this binary system. The optical spectroscopy of FR Cnc and HD 81032 carried out during 2002-2003, reveals the presence of strong and variable Ca II H and K, Halpha and Hbeta emission features indicative

  20. The mineral clouds on HD 209458b and HD 189733b

    NASA Astrophysics Data System (ADS)

    Helling, Ch.; Lee, G.; Dobbs-Dixon, I.; Mayne, N.; Amundsen, D. S.; Khaimova, J.; Unger, A. A.; Manners, J.; Acreman, D.; Smith, C.

    2016-07-01

    3D atmosphere model results are used to comparatively study the kinetic, non-equilibrium cloud formation in the atmospheres of two example planets guided by the giant gas planets HD 209458b and HD 189733b. Rather independently of hydrodynamic model differences, our cloud modelling suggest that both planets are covered in mineral clouds throughout the entire modelling domain. Both planets harbour chemically complex clouds that are made of mineral particles that have a height-dependent material composition and size. The remaining gas-phase element abundances strongly affect the molecular abundances of the atmosphere in the cloud-forming regions. Hydrocarbon and cyanopolyyne molecules can be rather abundant in the inner, dense part of the atmospheres of HD 189733b and HD 209458b. No one value for metallicity and the C/O ratio can be used to describe an extrasolar planet. Our results concerning the presence and location of water in relation to the clouds explain some of the observed difference between the two planets. In HD 189733b, strong water features have been reported while such features appear less strong for HD 209458b. By considering the location of the clouds in the two atmospheres, we see that obscuring clouds exist high in the atmosphere of HD 209458b, but much deeper in HD 189733b. We further conclude that the (self-imposed) degeneracy of cloud parameters in retrieval methods can only be lifted if the cloud formation processes are accurately modelled in contrast to prescribing them by independent parameters.

  1. Stellar Activity and Exclusion of the Outer Planet in the HD 99492 System

    NASA Astrophysics Data System (ADS)

    Kane, Stephen R.; Thirumalachari, Badrinath; Henry, Gregory W.; Hinkel, Natalie R.; Jensen, Eric L. N.; Boyajian, Tabetha S.; Fischer, Debra A.; Howard, Andrew W.; Isaacson, Howard T.; Wright, Jason T.

    2016-03-01

    A historical problem for indirect exoplanet detection has been contending with the intrinsic variability of the host star. If the variability is periodic, it can easily mimic various exoplanet signatures, such as radial velocity (RV) variations that originate with the stellar surface rather than the presence of a planet. Here we present an update for the HD 99492 planetary system, using new RV and photometric measurements from the Transit Ephemeris Refinement and Monitoring Survey. Our extended time series and subsequent analyses of the Ca ii H&K emission lines show that the host star has an activity cycle of ∼13 years. The activity cycle correlates with the purported orbital period of the outer planet, the signature of which is thus likely due to the host star activity. We further include a revised Keplerian orbital solution for the remaining planet, along with a new transit ephemeris. Our transit-search observations were inconclusive.

  2. X-RAY ACTIVITY PHASED WITH PLANET MOTION IN HD 189733?

    SciTech Connect

    Pillitteri, I.; Guenther, H. M.; Wolk, S. J.; Kashyap, V. L.; Cohen, O.

    2011-11-01

    We report on the follow-up XMM-Newton observation of the planet-hosting star HD 189733 we obtained in 2011 April. We observe a flare just after the secondary transit of the hot Jupiter. This event shares the same phase and many of the characteristics of the flare we observed in 2009. We suggest that a systematic interaction between planet and stellar magnetic fields when the planet passes close to active regions on the star can lead to periodic variability phased with planetary motion. By means of high-resolution X-ray spectroscopy with the Reflection Grating Spectrometer on board XMM-Newton, we determine that the corona of this star is unusually dense.

  3. HD139614: the Interferometric Case for a Group-Ib Pre-Transitional Young Disk

    NASA Technical Reports Server (NTRS)

    Labadie, Lucas; Matter, Alexis; Kreplin, Alexander; Lopez, Bruno; Wolf, Sebastian; Weigelt, Gerd; Ertel, Steve; Berger, Jean-Philippe; Pott, Jorg-Uwe; Danchi, William C.

    2014-01-01

    The Herbig Ae star HD139614 is a group-Ib object, which featureless SED indicates disk flaring and a possible pre-transitional evolutionary stage. We present mid- and near-IR interferometric results collected with MIDI, AMBER and PIONIER with the aim of constraining the spatial structure of the 0.1-10 AU disk region and assess its possible multi-component structure. A two-component disk model composed of an optically thin 2-AU wide inner disk and an outer temperature-gradient disk starting at 5.6 AU reproduces well the observations. This is an additional argument to the idea that group-I HAeBe inner disks could be already in the disk-clearing transient stage. HD139614 will become a prime target for mid-IR interferometric imaging with the second-generation instrument MATISSE of the VLTI.

  4. HD 139614: the interferometric case for a group-Ib pre-transitional young disk

    NASA Astrophysics Data System (ADS)

    Labadie, Lucas; Matter, Alexis; Kreplin, Alexander; Lopez, Bruno; Wolf, Sebastian; Weigelt, Gerd; Ertel, Steve; Berger, Jean-Philippe; Pott, Jorg-Uwe; Danchi, William C.

    2014-07-01

    The Herbig Ae star HD 139614 is a group-Ib object, which featureless SED indicates disk flaring and a possible pre-transitional evolutionary stage. We present mid- and near-IR interferometric results collected with MIDI, AMBER and PIONIER with the aim of constraining the spatial structure of the 0.1-10 AU disk region and assess its possible multi-component structure. A two-component disk model composed of an optically thin 2-AU wide inner disk and an outer temperature-gradient disk starting at 5.6 AU reproduces well the observations. This is an additional argument to the idea that group-I HAeBe inner disks could be already in the disk-clearing transient stage. HD 139614 will become a prime target for mid-IR interferometric imaging with the second-generation instrument MATISSE of the VLTI.

  5. HD 181068: a red giant in a triply eclipsing compact hierarchical triple system.

    PubMed

    Derekas, A; Kiss, L L; Borkovits, T; Huber, D; Lehmann, H; Southworth, J; Bedding, T R; Balam, D; Hartmann, M; Hrudkova, M; Ireland, M J; Kovács, J; Mezo, Gy; Moór, A; Niemczura, E; Sarty, G E; Szabó, Gy M; Szabó, R; Telting, J H; Tkachenko, A; Uytterhoeven, K; Benko, J M; Bryson, S T; Maestro, V; Simon, A E; Stello, D; Schaefer, G; Aerts, C; ten Brummelaar, T A; De Cat, P; McAlister, H A; Maceroni, C; Mérand, A; Still, M; Sturmann, J; Sturmann, L; Turner, N; Tuthill, P G; Christensen-Dalsgaard, J; Gilliland, R L; Kjeldsen, H; Quintana, E V; Tenenbaum, P; Twicken, J D

    2011-04-08

    Hierarchical triple systems comprise a close binary and a more distant component. They are important for testing theories of star formation and of stellar evolution in the presence of nearby companions. We obtained 218 days of Kepler photometry of HD 181068 (magnitude of 7.1), supplemented by ground-based spectroscopy and interferometry, which show it to be a hierarchical triple with two types of mutual eclipses. The primary is a red giant that is in a 45-day orbit with a pair of red dwarfs in a close 0.9-day orbit. The red giant shows evidence for tidally induced oscillations that are driven by the orbital motion of the close pair. HD 181068 is an ideal target for studies of dynamical evolution and testing tidal friction theories in hierarchical triple systems.

  6. On the orbital structure of the HD 82943 multi-planet system

    NASA Astrophysics Data System (ADS)

    Baluev, Roman V.; Beaugé, Cristian

    2014-07-01

    HD 82943 hosts a mysterious multi-planet system in the 2:1 mean-motion resonance that puzzles astronomers for more than a decade. We describe our new analysis of all radial velocity data currently available for this star, including both the most recent Keck data and the older but more numerous CORALIE measurements. Here we pay a major attention to the task of optimal scheduling of the future observation of this system. Applying several optimality criteria, we demonstrate that in the forthcoming observational season of HD 82943 (the winter 2014/2015) rather promising time ranges can be found. Observations of the near future may give rather remarkable improvement of the orbital fit, but only if we choose their time carefully.

  7. On the stability of the detected planet in the triple system HD 131399

    NASA Astrophysics Data System (ADS)

    Funk, B.; Pilat-Lohinger, E.; Bazsó, Á.; Bancelin, D.

    2017-03-01

    Wagner et al. (2016) reported the discovery of a Jovian planet within a triple-star system by using direct imaging. In their paper they suspect the planet might be on an unstable orbit. Due to the discovery by direct imaging the orbital parameters of the system (distances and eccentricities) possess large uncertainties. Therefore in our work we tested different dynamical configurations to determine the stable regions in the system HD 131399 by varying the distances and the eccentricities of the stellar and the planetary components. Using different numerical methods we could show that stable regions remain for almost all possible orbital parameters. Additionally we also investigated the possible habitability of the system HD 131399.

  8. Energy Distributions and spectra of Orion B stars

    NASA Technical Reports Server (NTRS)

    Schild, R. E.; Chaffee, F.

    1972-01-01

    New MK spectral types and energy distributions are presented for B stars in Orion for which far ultraviolet flux excesses have recently been discovered. Significant differences between HD spectral energy distributions show the Orion late B stars to have smaller Balmer discontinuities than do field stars of the same spectral types. For the late B stars, these effects cause the 1500 A fluxes to be under-estimated by approximately 0.5 mag. No comparable systematic effects were found for the early B stars.

  9. ON THE VOLATILE ENRICHMENTS AND HEAVY ELEMENT CONTENT IN HD189733b

    SciTech Connect

    Mousis, O.; Petit, J.-M.; Picaud, S.; Lunine, J. I.; Zahnle, K.; Marley, M. S.; Biennier, L.; Mitchell, J. B. A.; Cordier, D.; Georges, R.; Johnson, T. V.; Boudon, V.; Devel, M.; Griffith, C.; Iro, N.

    2011-02-01

    Favored theories of giant planet formation center around two main paradigms, namely the core accretion model and the gravitational instability model. These two formation scenarios support the hypothesis that the giant planet metallicities should be higher or equal to that of the parent star. Meanwhile, spectra of the transiting hot Jupiter HD189733b suggest that carbon and oxygen abundances range from depleted to enriched with respect to the star. Here, using a model describing the formation sequence and composition of planetesimals in the protoplanetary disk, we determine the range of volatile abundances in the envelope of HD189733b that is consistent with the 20-80 M{sub +} of heavy elements estimated to be present in the planet's envelope. We then compare the inferred carbon and oxygen abundances to those retrieved from spectroscopy, and we find a range of supersolar values that directly fit both spectra and internal structure models. In some cases, we find that the apparent contradiction between the subsolar elemental abundances and the mass of heavy elements predicted in HD189733b by internal structure models can be explained by the presence of large amounts of carbon molecules in the form of polycyclic aromatic hydrocarbons and soots in the upper layers of the envelope, as suggested by recent photochemical models. A diagnostic test that would confirm the presence of these compounds in the envelope is the detection of acetylene. Several alternative hypotheses that could also explain the subsolar metallicity of HD189733b are formulated: the possibility of differential settling in its envelope, the presence of a larger core that did not erode with time, a mass of heavy elements lower than the one predicted by interior models, a heavy element budget resulting from the accretion of volatile-poor planetesimals in specific circumstances, or the combination of all these mechanisms.

  10. The Non-thermal Radio Emitter HD 93250 Resolved by Long Baseline Interferometry

    NASA Astrophysics Data System (ADS)

    Sana, H.; Le Bouquin, J.-B.; De Becker, M.; Berger, J.-P.; de Koter, A.; Mérand, A.

    2011-10-01

    As the brightest O-type X-ray source in the Carina nebula, HD 93250 (O4 III(fc)) is X-ray overluminous for its spectral type and has an unusually hard X-ray spectrum. Two different scenarios have been invoked to explain its X-ray properties: wind-wind interaction and magnetic wind confinement. Yet, HD 93250 shows absolutely constant radial velocities over timescales of years suggesting either a single star, a binary system seen pole-on view or a very long period, and/or highly eccentric system. Using the ESO Very Large Telescope Interferometer, we resolved HD 93250 as a close pair with similar components. We measured a near-infrared flux ratio of 0.8 ± 0.1 and a separation of (1.5 ± 0.2) × 10-3 arcsec. At the distance of Carina, this corresponds to a projected physical distance of 3.5 AU. While a quantitative investigation would require a full characterization of the orbit, the binary nature of HD 93250 allows us to qualitatively explain both its X-ray flux and hardness and its non-thermal radio emission in the framework of a colliding wind scenario. We also discuss various observational biases. We show that, due to line blending of two similar spectral components, HD 93250 could have a period as short as 1 to several years despite the lack of measurable radial velocity variations. Based on observations collected under program IDs 086.D-0586 and 386.D-0198 at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile.

  11. SURVEY OF NEARBY FGK STARS AT 160 mum WITH SPITZER

    SciTech Connect

    Tanner, Angelle; Beichman, Charles; Bryden, Geoff; Lisse, Carey

    2009-10-10

    The Spitzer Space Telescope has advanced debris disk science tremendously with a wealth of information on debris disks around nearby A, F, G, K, and M stars at 24 and 70 mum with the MIPS photometer and at 8-34 mum with IRS. Here we present 160 mum observations of a small subset of these stars. At this wavelength, the stellar photospheric emission is negligible and any detected emission corresponds to cold dust in extended Kuiper Belt analogs. However, the Spitzer 160 mum observations are limited in sensitivity by the large beam size which results in significant 'noise' due to cirrus and extragalactic confusion. In addition, the 160 mum measurements suffer from the added complication of a light leak next to the star's position whose flux is proportional to the near-infrared flux of the star. We are able to remove the contamination from the leak and report 160 mum measurements or upper limits for 24 stars. Three stars (HD 10647, HD 207129, and HD 115617) have excesses at 160 mum that we use to constrain the properties of the debris disks around them. A more detailed model of the spectral energy distribution of HD 10647 reveals that the 70 and 160 mum emission could be due to small water ice particles at a distance of 100 AU, consistent with Hubble Space Telescope optical imaging of circumstellar material in the system.

  12. An Upper Limit on the Albedo of HD 209458b: Direct Imaging Photometry with the MOST Satellite

    NASA Astrophysics Data System (ADS)

    Rowe, Jason F.; Matthews, Jaymie M.; Seager, Sara; Kuschnig, Rainer; Guenther, David B.; Moffat, Anthony F. J.; Rucinski, Slavek M.; Sasselov, Dimitar; Walker, Gordon A. H.; Weiss, Werner W.

    2006-08-01

    We present space-based photometry of the transiting exoplanetary system HD 209458 obtained with the Microvariablity and Oscillations of Stars (MOST) satellite, spanning 14 days and covering 4 transits and 4 secondary eclipses. The HD 209458 photometry was obtained in MOST's lower precision direct imaging mode, which is used for targets in the brightness range 6.5>=V>=13. We describe the photometric reduction techniques for this mode of observing, in particular the corrections for stray earthshine. We do not detect the secondary eclipse in the MOST data, to a limit in depth of 0.053 mmag (1 σ). We set a 1 σ upper limit on the planet-star flux ratio of 4.88×10-5 corresponding to a geometric albedo upper limit in the MOST bandpass (400-700 nm) of 0.25. The corresponding numbers at the 3 σ level are 1.34×10-4 and 0.68, respectively. HD 209458b is half as bright as Jupiter in the MOST bandpass. This low geometric albedo value is an important constraint for theoretical models of the HD 209458b atmosphere, in particular ruling out the presence of reflective clouds. A second MOST campaign on HD 209458 is expected to be sensitive to an exoplanet albedo as low as 0.13 (1 σ), if the star does not become more intrinsically variable in the meantime. MOST is a Canadian Space Agency mission, operated jointly by Dynacon, Inc., and the Universities of Toronto and British Columbia, with assistance from the University of Vienna.

  13. Evidence for the Direct Detection of the Thermal Spectrum of the Non-Transiting Hot Gas Giant HD 88133 b

    NASA Astrophysics Data System (ADS)

    Piskorz, Danielle; Benneke, Björn; Crockett, Nathan R.; Lockwood, Alexandra C.; Blake, Geoffrey A.; Barman, Travis S.; Bender, Chad F.; Bryan, Marta L.; Carr, John S.; Fischer, Debra A.; Howard, Andrew W.; Isaacson, Howard; Johnson, John A.

    2016-12-01

    We target the thermal emission spectrum of the non-transiting gas giant HD 88133 b with high-resolution near-infrared spectroscopy, by treating the planet and its host star as a spectroscopic binary. For sufficiently deep summed flux observations of the star and planet across multiple epochs, it is possible to resolve the signal of the hot gas giant’s atmosphere compared to the brighter stellar spectrum, at a level consistent with the aggregate shot noise of the full data set. To do this, we first perform a principal component analysis to remove the contribution of the Earth’s atmosphere to the observed spectra. Then, we use a cross-correlation analysis to tease out the spectra of the host star and HD 88133 b to determine its orbit and identify key sources of atmospheric opacity. In total, six epochs of Keck NIRSPEC L-band observations and three epochs of Keck NIRSPEC K-band observations of the HD 88133 system were obtained. Based on an analysis of the maximum likelihood curves calculated from the multi-epoch cross-correlation of the full data set with two atmospheric models, we report the direct detection of the emission spectrum of the non-transiting exoplanet HD 88133 b and measure a radial projection of the Keplerian orbital velocity of 40 ± 15 km s-1, a true mass of {1.02}-0.28+0.61{M}{{J}}, a nearly face-on orbital inclination of {15}-5+6^\\circ , and an atmosphere opacity structure at high dispersion dominated by water vapor. This, combined with 11 years of radial velocity measurements of the system, provides the most up-to-date ephemeris for HD 88133.

  14. A JVLA survey of the high-frequency radio emission of the massive magnetic B- and O-type stars

    NASA Astrophysics Data System (ADS)

    Kurapati, Sushma; Chandra, Poonam; Wade, Gregg; Cohen, David H.; David-Uraz, Alexandre; Gagne, Marc; Grunhut, Jason; Oksala, Mary E.; Petit, Veronique; Shultz, Matt; Sundqvist, Jon; Townsend, Richard H. D.; ud-Doula, Asif

    2017-02-01

    We conducted a survey of seven magnetic O-type stars and eleven B-type stars with masses above 8 M⊙ using the Very Large Array in the 1, 3 and 13 cm bands. The survey resulted in a detection of two O- and two B-type stars. While the detected O-type stars - HD 37742 and HD 47129 - are in binary systems, the detected B-type stars, HD 156424 and ALS 9522, are not known to be in binaries. All four stars were detected at 3 cm, whereas three were detected at 1 cm and only one star was detected at 13 cm. The detected B-type stars are significantly more radio luminous than the non-detected ones, which is not the case for O-type stars. The non-detections at 13 cm are interpreted as due to thermal free-free absorption. Mass-loss rates were estimated using 3 cm flux densities and were compared with theoretical mass-loss rates, which assume free-free emission. For HD 37742, the two values of the mass-loss rates were in good agreement, possibly suggesting that the radio emission for this star is mainly thermal. For the other three stars, the estimated mass-loss rates from radio observations were much higher than those expected from theory, suggesting either a possible contribution from non-thermal emission from the magnetic star or thermal or non-thermal emission due to interacting winds of the binary system, especially for HD 47129. All the detected stars are predicted to host centrifugal magnetospheres except HD 37742, which is likely to host a dynamical magnetosphere. This suggests that non-thermal radio emission is favoured in stars with centrifugal magnetospheres.

  15. FURTHER EVIDENCE OF THE PLANETARY NATURE OF HD 95086 b FROM GEMINI/NICI H-BAND DATA

    SciTech Connect

    Meshkat, T.; Kenworthy, M.; Bailey, V.; Su, K. Y. L.; Rameau, J.; Chauvin, G.; Lagrange, A.-M.; Boccaletti, A.; Mamajek, E. E.; Currie, T.

    2013-10-01

    We present our analysis of the Gemini/NICI H-band data of HD 95086, following the discovery of the planet HD 95086 b in L'. The H-band data reach a contrast of 12.7 mag relative to the host star at 5σ levels in the location of HD 95086 b, and no point source is found. Our non-detection and H – L' color limit rules out the possibility that the object is a foreground L/T dwarf and that, if it is bound to HD 95086, it is a genuine planetary mass object. We estimate a new pre-main-sequence isochronal age for HD 95086 of 17 ± 4 Myr, which is commensurate with previous mean age estimates for the Lower Cen-Crux subgroup. Adopting an age of 17 Myr, the color limit is inconsistent with the COND model, marginally consistent with the BT-SETTL model, and consistent with the DUSTY model.

  16. Spectroscopic Orbits for 15 Late-type Stars

    NASA Astrophysics Data System (ADS)

    Willmarth, Daryl W.; Fekel, Francis C.; Abt, Helmut A.; Pourbaix, Dimitri

    2016-08-01

    Spectroscopic orbital elements are determined for 15 stars with periods from 8 to 6528 days with six orbits computed for the first time. Improved astrometric orbits are computed for two stars and one new orbit is derived. Visual orbits were previously determined for four stars, four stars are members of multiple systems, and five stars have Hipparcos “G” designations or have been resolved by speckle interferometry. For the nine binaries with previous spectroscopic orbits, we determine improved or comparable elements. For HD 28271 and HD 200790, our spectroscopic results support the conclusions of previous authors that the large values of their mass functions and lack of detectable secondary spectrum argue for the secondary in each case being a pair of low-mass dwarfs. The orbits given here may be useful in combination with future interferometric and Gaia satellite observations.

  17. The corona of HD 189733 and its X-ray activity

    SciTech Connect

    Pillitteri, I.; Wolk, S. J.; Günther, H. M.; Cohen, O.; Kashyap, V.; Drake, J. J.; Lopez-Santiago, J.; Sciortino, S.

    2014-04-20

    Testing whether close-in massive exoplanets (hot Jupiters) can enhance the stellar activity in their host primary is crucial for the models of stellar and planetary evolution. Among systems with hot Jupiters, HD 189733 is one of the best studied because of its proximity, strong activity, and the presence of a transiting planet, which allows transmission spectroscopy and a measure of the planetary radius and its density. Here we report on the X-ray activity of the primary star, HD 189733 A, using a new XMM-Newton observation and a comparison with the previous X-ray observations. The spectrum in the quiescent intervals is described by two temperatures at 0.2 keV and 0.7 keV, while during the flares a third component at 0.9 keV is detected. With the analysis of the summed Reflection Grating Spectrometer spectra, we obtain estimates of the electron density in the range n{sub e} = (1.6-13) × 10{sup 10} cm{sup –3}, and thus the corona of HD 189733 A appears denser than the solar one. For the third time, we observe a large flare that occurred just after the eclipse of the planet. Together with the flares observed in 2009 and 2011, the events are restricted to a small planetary phase range of φ = 0.55-0.65. Although we do not find conclusive evidence of a significant excess of flares after the secondary transits, we suggest that the planet might trigger such flares when it passes close to the locally high magnetic field of the underlying star at particular combinations of stellar rotational phases and orbital planetary phases. For the most recent flares, a wavelet analysis of the light curve suggests a loop of length of four stellar radii at the location of the bright flare, and a local magnetic field of the order of 40-100 G, in agreement with the global field measured in other studies. The loop size suggests an interaction of magnetic nature between planet and star, separated by only ∼8R {sub *}. The X-ray variability of HD 189733 A is larger than the variability

  18. The SOPHIE search for northern extrasolar planets. VII. A warm Neptune orbiting HD 164595

    NASA Astrophysics Data System (ADS)

    Courcol, B.; Bouchy, F.; Pepe, F.; Santerne, A.; Delfosse, X.; Arnold, L.; Astudillo-Defru, N.; Boisse, I.; Bonfils, X.; Borgniet, S.; Bourrier, V.; Cabrera, N.; Deleuil, M.; Demangeon, O.; Díaz, R. F.; Ehrenreich, D.; Forveille, T.; Hébrard, G.; Lagrange, A. M.; Montagnier, G.; Moutou, C.; Rey, J.; Santos, N. C.; Ségransan, D.; Udry, S.; Wilson, P. A.

    2015-09-01

    High-precision radial velocity surveys explore the population of low-mass exoplanets orbiting bright stars. This allows accurately deriving their orbital parameters such as their occurrence rate and the statistical distribution of their properties. Based on this, models of planetary formation and evolution can be constrained. The SOPHIE spectrograph has been continuously improved in past years, and thanks to an appropriate correction of systematic instrumental drift, it is now reaching 2 m s-1precision in radial velocity measurements on all timescales. As part of a dedicated radial velocity survey devoted to search for low-mass planets around a sample of 190 bright solar-type stars in the northern hemisphere, we report the detection of a warm Neptune with a minimum mass of 16.1 ± 2.7M⊕ orbiting the solar analog HD 164595 in 40 ± 0.24 days. We also revised the parameters of the multiplanetary system around HD 190360. We discuss this new detection in the context of the upcoming space mission CHEOPS, which is devoted to a transit search of bright stars harboring known exoplanets. Based on observations made with SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS/OSU Pythéas), France (program 07A.PNP.CONS).Appendix A is available in electronic form at http://www.aanda.org

  19. VizieR Online Data Catalog: HD 163151: a new W UMa type system (Rodriguez+ 1998)

    NASA Astrophysics Data System (ADS)

    Rodríguez, E.; Claret, A.; García, J. M.; Zerbi, F. M.; Garrido, R.; Martín, S.; Akan, C.; Luedeke, K.; Keskin, V.; Ibanoglu, C.; Evren, S.; Tunca, Z.; Pekunlu, R.; Paparo, M.; Nuspl, J.; Krisciunas, K.; Jiang, S. Y.

    1998-06-01

    Table 2 contains 408 simultaneous measurements collected in each of the four uvby colours of the Stromgren photometric system for the W UMa system HD 163151. The data are magnitude differences (Du, Dv, Db, Dy, D(b-y), Dm1, Dc1) of the variable star minus comparison star in the standard system versus Heliocentric Julian Day. Tables 3, 4 and 5 are the same, but for Hβ (65 points), Johnson B data (212 points) and Johnson V data (355 points). The comparison star is HD 166095. The origin in time is the Julian Day 2449858. The observations were carried out (by E. Rodriguez, A. Claret, J.M. Garcia, F.M. Zerbi, R. Garrido, S. Martin, C. Akan, K. Luedeke, V. Keskin, C. Ibanoglu, S. Evren, Z. Tunca, R. Pekunlu, M. Paparo, J. Nuspl, K. Krisciunas and S.Y. Jiang) in 1995 during the course of a multisite campaign. The following telescopes were used: 90cm telescope of the Sierra Nevada Observatory, Spain (uvby-Hβ photometry); 50cm telescope at the Ege University Observatory, Turkey (BV-uvby); 50cm telescope at Piszkesteto mountain station, Konkoly Observatory, Hungary (BV); 50cm telescope at the Merate Observatory, Italy (V); 30cm telescope at Albuquerque, New Mexico, USA (V) and 15cm telescope at Mauna Kea, Hawaii, USA (V). (4 data files).

  20. Study of variable extinction of hot stars with circumstellar dust shells

    NASA Technical Reports Server (NTRS)

    1984-01-01

    Various projects on the topic of hot stars with circumstellar dust are reported. The surface temperature, wind speed, and interstellar reddening were determined for the variable WC7 star HD 193793. Circumstellar carbon monoxide molecules were detected around a hot star. The dust envelope of the star W90 in the young cluster NGC2264 is discussed, and the spectra of low-redshift and X-ray emitting quasars are mentioned.

  1. The Translucent Clouds toward HD 204827

    NASA Astrophysics Data System (ADS)

    Snow, Theodore P.; Blake, Geoffrey A.; Clayton, Geoffrey C.; Gordon, Karl D.; Jensen, Adam G.; McCall, Benjamin J.; Misselt, Karl A.; Rachford, Brian L.; Salama, Farid; Smith, Erin C.; Welty, Daniel K.

    2015-01-01

    Translucent clouds represent a middle ground between the diffuse and dense interstellar medium. In these clouds the total dust extinction lies in the range of AV = 1.5 to 10 magnitudes, hydrogen is predominantly in molecular form, and carbon becomes neutral and then molecular (in the form of CO). Our goal is to characterize such clouds toward HD 204827, which has spectral type O9 V, V = 7.94, E(B-V) = 1.11, a total extinction AV ~ 3.5, and very steep far-UV extinction. HD 204827 is also a spectroscopic binary -- enabling a clear distinction between stellar and interstellar absorption lines. Diffuse interstellar bands (DIBs) have been cataloged; this sight line is the exemplar for the so-called C2 DIBs. The observed molecular abundances (e.g., for CN, C2, C3, CO) are higher than those found for diffuse clouds, also suggesting the presence of translucent material.We will discuss our multi-wavelength observations of HD 204827 -- including mm-wave spectra, IR spectra and photometry, optical spectra, and UV (HST) spectra, along with laboratory data on interstellar analogs -- which enable a uniquely comprehensive study of the abundances, depletions, chemistry, and physical conditions characterizing the translucent material in this sight line.

  2. Characterization of depression in prodromal Huntington disease in the neurobiological predictors of HD (PREDICT-HD) study.

    PubMed

    Epping, Eric A; Mills, James A; Beglinger, Leigh J; Fiedorowicz, Jess G; Craufurd, David; Smith, Megan M; Groves, Mark; Bijanki, Kelly R; Downing, Nancy; Williams, Janet K; Long, Jeffrey D; Paulsen, Jane S

    2013-10-01

    Depression causes significant morbidity and mortality, and this also occurs in Huntington Disease (HD), an inherited neurodegenerative illness with motor, cognitive, and psychiatric symptoms. The presentation of depression in this population remains poorly understood, particularly in the prodromal period before development of significant motor symptoms. In this study, we assessed depressive symptoms in a sample of 803 individuals with the HD mutation in the prodromal stage and 223 mutation-negative participants at the time of entry in the Neurobiological Predictors of HD (PREDICT-HD) study. Clinical and biological HD variables potentially related to severity of depression were analyzed. A factor analysis was conducted to characterize the symptom domains of depression in a subset (n=168) with clinically significant depressive symptoms. Depressive symptoms were found to be more prevalent in HD mutation carriers but did not increase with proximity to HD diagnosis and were not associated with length of the HD mutation. Increased depressive symptoms were significantly associated with female gender, self-report of past history of depression, and a slight decrease in functioning, but not with time since genetic testing. The factor analysis identified symptom domains similar to prior studies in other populations. These results show that individuals with the HD mutation are at increased risk to develop depressive symptoms at any time during the HD prodrome. The clinical presentation appears to be similar to other populations. Severity and progression are not related to the HD mutation.

  3. Detailed abundance analysis of five field blue horizontal-branch stars

    NASA Astrophysics Data System (ADS)

    Kafando, I.; LeBlanc, F.; Robert, C.

    2016-06-01

    Previous studies have shown that hot blue horizontal-branch (BHB) stars in globular clusters present abundance anomalies of certain chemical elements in their atmosphere; some metals are overabundant while helium is underabundant. Vertical stratification of chemical species, including iron, is also found in the atmosphere of a number of these objects. The aim of our work is to do a detailed abundance analysis of BHB stars found in the field. We studied the stars HD 128801, HD 143459, HD 213781, and HZ 27, using our high-resolution spectra in the visible region obtained with ESPaDOnS at the Canada-France-Hawaii Telescope, and also Feige 86, using existing Ultraviolet and Visual Echelle Spectrograph visible spectra from the ESO archives. We searched for vertical stratification of the elements identified in our five stars, with the ZEEMAN2 code and stellar model atmospheres of PHOENIX. We confirm here the star rotational and radial velocities previously found, along with their average abundances. For the three cooler stars in our sample (HD 128801, HD 143459, and HZ 27), most elements detected are underabundant. For the two hotter stars (Feige 86 and HD 213781), the abundances of most elements are near or above their solar value. Of all the elements studied, only phosphorus is clearly found to be vertically stratified in the atmosphere of HD 213781. Marginal indications of vertical stratification of iron is observed for Feige 86. The chemical properties of the five field BHB stars are consistent with those of their globular-cluster counterparts.

  4. Detecting and Characterizing Exoplanets: The GJ 436 and HD 149026 Systems

    NASA Astrophysics Data System (ADS)

    Stevenson, Kevin B.; Harrington, J.; Madhusudhan, N.; Seager, S.; Deming, D.; Rauscher, E.; Fortney, J. J.; Loredo, T. J.; Lewis, N.; Moses, J. I.; Visscher, C. W.; UCF Exoplanets Group

    2013-01-01

    This research utilized the Spitzer Space Telescope to make secondary eclipse measurements, when the exoplanet passes behind its parent star, to provide direct measurements of emitted planetary flux. Multiple observations at different wavelengths help to constrain a planet's thermal profile and atmospheric composition. We will present dayside atmospheric constraints of two known extrasolar planets, GJ 436b and HD 149026b, and discuss the serendipitous discovery of UCF-1.01 and UCF-1.02, two sub-Earth-sized exoplanet candidates. The Neptune-sized exoplanet GJ 436b transits a relatively cool M-dwarf star in a 2.64-day orbit. With an equilibrium temperature of only 714 K, the dominant carbon-bearing species in GJ 436b's atmosphere is expected to be methane, not carbon monoxide. However, Spitzer observations of the system during secondary eclipse indicate a possible methane deficiency by a factor of ~7000. We will present additional atmospheric constraints and discuss several disequilibrium processes as possible explanations. The Saturn-sized exoplanet HD 149026b transits a large, relatively hot parent star at a distance of only 0.042 AU. The planet's high average density suggests that most of HD 149026b's mass must be in its large, icy/rocky core. Previous work reported contradicting eclipse depths at 8.0 microns. We reanalyzed these data and combined the results with nine new secondary-eclipse observations at five infrared wavelengths to present constraints on the thermal profile and atmospheric composition of HD 149026b. UCF-1.01 and UCF-1.02 are extrasolar planet candidates only two-thirds the size of the Earth. These objects transit the nearby M-dwarf star GJ 436 (located only 33 ly away). We will describe two new techniques that played a critical role in their detection, present details on eliminating false positives, and hypothesize possible atmospheric end states. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a

  5. Composition of interstellar clouds in the disk and halo. I - HD 93521

    NASA Technical Reports Server (NTRS)

    Spitzer, Lyman, Jr.; Fitzpatrick, Edward L.

    1993-01-01

    Interstellar column densities of Fe, S, Si, Mn, and Mg in their dominant ionization state, as well as of C(+) and S(2+), are presently derived from analyses of HST UV observations of the Galactic halo star HD 93521. Ratios of column densities for the dominant species yield approximations of the logarithmic depletion D(X) in the warm, primarily neutral H gas which produces each of the resolved components. Variations of D between components are highly correlated between elements; about two Fe atoms leave the grains for every Si atom, as if these atoms were primarily bound in the Fe2SiO4 molecules within the grain cores.

  6. Discovery of an activity cycle in the solar analog HD 45184. Exploring Balmer and metallic lines as activity proxy candidates

    NASA Astrophysics Data System (ADS)

    Flores, M.; González, J. F.; Jaque Arancibia, M.; Buccino, A.; Saffe, C.

    2016-05-01

    Context. Most stellar activity cycles similar to that found in the Sun have been detected by using the chromospheric Ca ii H&K lines as stellar activity proxies. However, it is unclear whether such activity cycles can be identified using other optical lines. Aims: We aim to detect activity cycles in solar-analog stars and determine whether they can be identified through other optical lines, such as Fe II and Balmer lines. We study the solar-analog star HD 45184 using HARPS spectra. The temporal coverage and high quality of the spectra allow us to detect both long- and short-term activity variations. Methods: We analysed the activity signatures of HD 45184 by using 291 HARPS spectra obtained between 2003 and 2014. To search for line-core flux variations, we focused on Ca ii H&K and Balmer Hα and Hβ lines, which are typically used as optical chromospheric activity indicators. We calculated the HARPS-S index from Ca ii H&K lines and converted it into the Mount Wilson scale. In addition, we also considered the equivalent widths of Balmer lines as activity indicators. Moreover, we analysed the possible variability of Fe ii and other metallic lines in the optical spectra. The spectral variations were analysed for periodicity using the Lomb-Scargle periodogram. Results: We report for the first time a long-term 5.14-yr activity cycle in the solar-analog star HD 45184 derived from Mount Wilson S index. This makes HD 45184 one of most similar stars to the Sun with a known activity cycle. The variation is also evident in the first lines of the Balmer series, which do not always show a correlation with activity in solar-type stars. Notably, unlike the solar case, we also found that the equivalent widths of the high photospheric Fe ii lines (4924 Å, 5018 Å and 5169 Å) are modulated (±2 mÅ) by the chromospheric cycle of the star. These metallic lines show variations above 4σ in the rms spectrum, while some Ba ii and Ti ii lines present variations at 3σ level, which

  7. Exocometary gas in the HD 181327 debris ring

    NASA Astrophysics Data System (ADS)

    Marino, S.; Matrà, L.; Stark, C.; Wyatt, M. C.; Casassus, S.; Kennedy, G.; Rodriguez, D.; Zuckerman, B.; Perez, S.; Dent, W. R. F.; Kuchner, M.; Hughes, A. M.; Schneider, G.; Steele, A.; Roberge, A.; Donaldson, J.; Nesvold, E.

    2016-08-01

    An increasing number of observations have shown that gaseous debris discs are not an exception. However, until now, we only knew of cases around A stars. Here we present the first detection of 12CO (2-1) disc emission around an F star, HD 181327, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) observations at 1.3 mm. The continuum and CO emission are resolved into an axisymmetric disc with ring-like morphology. Using a Markov chain Monte Carlo method coupled with radiative transfer calculations, we study the dust and CO mass distribution. We find the dust is distributed in a ring with a radius of 86.0 ± 0.4 au and a radial width of 23.2 ± 1.0 au. At this frequency, the ring radius is smaller than in the optical, revealing grain size segregation expected due to radiation pressure. We also report on the detection of low-level continuum emission beyond the main ring out to ˜200 au. We model the CO emission in the non-local thermodynamic equilibrium regime and we find that the CO is co-located with the dust, with a total CO gas mass ranging between 1.2 × 10-6 M⊕ and 2.9 × 10-6 M⊕, depending on the gas kinetic temperature and collisional partners densities. The CO densities and location suggest a secondary origin, i.e. released from icy planetesimals in the ring. We derive a CO+CO2 cometary composition that is consistent with Solar system comets. Due to the low gas densities, it is unlikely that the gas is shaping the dust distribution.

  8. FUSE Observations of K--M Stars

    NASA Astrophysics Data System (ADS)

    Ake, T. B.; Dupree, A. K.; Linsky, J. L.; Harper, G. M.; Young, P. R.

    2000-12-01

    As part of the FUSE PI program, a representative sample of cool stars is being surveyed in the LWRS (30 x 30 arcsec) aperture. We report on recent observations of three late-type stars, AU Mic (HD 197481, M0 Ve), β Gem (HD 62509, K0 IIIb), and α Ori (HD 39801, M1-2 Ia--Iab). AU Mic and β Gem show strong emission lines of O VI 1032/1037 and C III 977/1176 and weaker lines of C II, N II, N III, S IV, Si III, Si IV, and perhaps Fe III. AU Mic has evidence of He II and S III emission, and β Gem shows S I emission. Differences are seen in line ratios and line profiles between these stars. In α Ori, these features are very weak or non-existent, and Fe II fluorescent lines in the 1100-1150 Å region, pumped by H I Lyman α , are present. Several emission lines are still unidentified in all spectra. Prospects for future cool star observations will be discussed. This work is based on data obtained for the Guaranteed Time Team by the NASA-CNES-CSA FUSE mission operated by the Johns Hopkins University. Financial support to U. S. participants has been provided by NASA contract NAS5-32985.

  9. Tracing back the evolution of the candidate LBV HD 168625

    NASA Astrophysics Data System (ADS)

    Mahy, L.; Hutsemékers, D.; Royer, P.; Waelkens, C.

    2016-10-01

    Context. The luminous blue variable phase is a crucial transitory phase that is not clearly understood in the massive star evolution. Aims: We have obtained far-infrared Herschel/PACS imaging and spectroscopic observations of the nebula surrounding the candidate LBV HD 168625. By combining these data with optical spectra of the central star, we want to constrain the abundances in the nebula and in the star and compare them to trace back the evolution of this object. Methods: We use the CMFGEN atmosphere code to determine the fundamental parameters and the CNO abundances of the central star whilst the abundances of the nebula are derived from the emission lines present in the Herschel/PACS spectrum. Results: The far-infrared images show a nebula composed of an elliptical ring/torus of ejecta with a ESE-WNW axis and of a second perpendicular bipolar structure composed of empty caps/rings. We detect equatorial shells composed of dust and ionized material with different sizes when observed at different wavelengths, and bipolar caps more of less separated from the central star in Hα and mid-IR images. This complex global structure seems to show two different inclinations: ~40° for the equatorial torus and ~ 60° for the bipolar ejections. From the Herschel/PACS spectrum, we determine nebular abundances of N/H = 4.1 ± 0.8 × 10-4 and , as well as a mass of ionized gas of 0.17 ± 0.04 M⊙ and a neutral hydrogen mass of about 1.0 ± 0.3 M⊙ which dominates. Analysis of the central star reveals Teff = 14 000 ± 2000 K, log g = 1.74 ± 0.05 and log (L/L⊙) = 5.58 ± 0.11. We derive stellar CNO abundances of about N/H = 5.0 ± 1.5 × 10-4, C/H = 1.4 ± 0.5 × 10-4 and O/H = 3.5 ± 1.0 × 10-4, not significantly different from nebular abundances. All these measurements taken together are compatible with the evolutionary tracks of a star with an initial mass between 28 and 33 M⊙ and with a critical rotational rate between 0.3 and 0.4 that has lost its material during or

  10. REVISED ORBIT AND TRANSIT EXCLUSION FOR HD 114762b

    SciTech Connect

    Kane, Stephen R.; Dragomir, Diana; Henry, Gregory W.; Fischer, Debra A.; Howard, Andrew W.; Wang, Xuesong; Wright, Jason T.

    2011-07-10

    Transiting planets around bright stars have allowed the detailed follow-up and characterization of exoplanets, such as the study of exoplanetary atmospheres. The Transit Ephemeris Refinement and Monitoring Survey is refining the orbits of the known exoplanets to confirm or rule out both transit signatures and the presence of additional companions. Here we present results for the companion orbiting HD 114762 in an eccentric 84 day orbit. Radial velocity analysis performed on 19 years of Lick Observatory data constrain the uncertainty in the predicted time of mid-transit to {approx}5 hr, which is less than the predicted one-half day transit duration. We find no evidence of additional companions in this system. New photometric observations with one of our Automated Photoelectric Telescopes at Fairborn Observatory taken during a revised transit time for companion b, along with 23 years of nightly automated observations, allow us to rule out on-time central transits to a limit of {approx}0.001 mag. Early or late central transits are ruled out to a limit of {approx}0.002 mag, and transits with half the duration of a central transit are ruled out to a limit of {approx}0.003 mag.

  11. A Possible Icy Kuiper Belt around HD 181327

    NASA Astrophysics Data System (ADS)

    Chen, Christine H.; Fitzgerald, Michael P.; Smith, Paul S.

    2008-12-01

    We have obtained a Gemini South T-ReCS Qa-band (18.3 μm) image and a Spitzer MIPS SED-mode observation of HD 181327, an F5/F6 V member of the ~12 Myr old β Pictoris moving group. We resolve the disk in thermal emission for the first time and find that the northern arm of the disk is 1.4 times brighter than the southern arm. In addition, we detect a broad peak in the combined Spitzer IRS and MIPS spectra at 60-75 μm that may be produced by emission from crystalline water ice. We model the IRS and MIPS data using a size distribution of amorphous olivine and water ice grains (dn/da propto a-2.25, with amin consistent with the minimum blowout size and amax = 20 μm) located at a distance of 86.3 AU from the central star, as observed in previously published scattered-light images. Since the photodesorption lifetime for the icy particles is ~1400 yr, significantly less than the estimated ~12 Myr age of the system, we hypothesize that we have detected debris that may be steadily replenished by collisions among icy Kuiper Belt object-like parent bodies in a newly forming planetary system.

  12. Physical Parameters of the Pre-WN Candidate HD326823

    NASA Astrophysics Data System (ADS)

    de Araujo, F. X.; Marcolino, W. L. F.; Borges Fernándes, M.

    2006-06-01

    HD326823 is a massive and luminous star characterized mainly by the presence of very intense HeI emission lines. From qualitative spectroscopic studies it was proposed by Lopes et al. (1992, A&A, 261, 482) and Borges Fernándes et al. (2001, ApJS, 136, 747) that this interesting object is in a pre-WN stage of evolution. In the present work we reinforce this conclusion, thanks to the estimate of its physical parameters like mass loss rate and especially chemical abundances. The data analysed by us were obtained at ESO 2.2-m telescope, with the spectrograph FEROS (R=48000) on April, 2005. The method employed to obtain the parameters is the fitting of HI, HeI and NII emission lines. In order to do this we have used the CMFGEN code, developed by J. Hilliers and colaborators (see, for instance, Hiller & Miller 1998, ApJ, 496, 407). This code is adequate for the modelling of lines produced in an expanding atmosphere and it includes important effects like line-blanketting and clumping. Preliminary results indicate a mass loss rate in the range and a clear overabundance of helium. As nitrogen abundance is concerned, it also indicates a tendency of increased abundance, but the result is not so firm in this case.

  13. Infrared Observations During the Secondary Eclipse of HD209458b

    NASA Astrophysics Data System (ADS)

    Richardson, L. J.; Deming, D.; Wiedemann, G.; Goukenleuque, C.; Esposito, L. W.; Harrington, J.

    2001-11-01

    We discuss the status of our observational program to detect infrared radiation from the "transiting planet," HD209458b. Current models suggest that the planet could be as hot as 1400K, with a significant infrared output in spectral bands having minimum water vapor opacity. Our differential spectroscopic technique is designed to detect the subtle change in the 2-4 micron spectrum as the planet is blocked by the star during secondary eclipse. We have observed the system during three secondary eclipse events: two in July 2001 using ISAAC at the VLT (3.5-3.7 microns, R=3300) and one in September 2001 using the SpeX instrument at the IRTF (1.9-4.2 microns, R=1500). Analysis of these extensive data is in progress. Although direct detection of the planet is not guaranteed, initial examination of the data lead us to be optimistic concerning the utility of our differential spectroscopic approach. This work is sponsored by NASA's Origins of Solar Systems Program and by a NASA GSRF Fellowhsip to L.J.R.

  14. Infrared observations during the secondary eclipse of HD209458b

    NASA Astrophysics Data System (ADS)

    Richardson, L. J.; Deming, D.; Wiedemann, G.; Goukenleuque, C.; Esposito, L. W.; Harrington, J.

    2001-12-01

    We discuss the status of our observational program to detect infrared radiation from the "transiting planet," HD209458b. Current models suggest that the planet could be as hot as 1400K, with a significant infrared output in spectral bands having minimum water vapor opacity. Our differential spectroscopic technique is designed to detect the subtle change in the 2-4 micron spectrum as the planet is blocked by the star during secondary eclipse. We have observed the system during four secondary eclipse events: two in July 2001 using ISAAC at the VLT (3.5-3.7 microns, R=3300) and two in September 2001 using the SpeX instrument at the IRTF (1.9-4.2 microns, R=1500). Analysis of these extensive data is in progress. Although direct detection of the planet is not guaranteed, initial examination of the data lead us to be optimistic concerning the utility of our differential spectroscopic approach. This work is sponsored by NASA's Origins of Solar Systems Program and by a NASA GSRP Fellowship to L.J.R.

  15. The stellar wind velocity field of HD 77581

    NASA Astrophysics Data System (ADS)

    Manousakis, A.; Walter, R.

    2015-12-01

    Aims: The early acceleration of stellar winds in massive stars is poorly constrained. The scattering of hard X-ray photons emitted by the pulsar in the high-mass X-ray binary Vela X-1 can be used to probe the stellar wind velocity and density profile close to the surface of its supergiant companion HD 77581. Methods: We built a high signal-to-noise and high resolution hard X-ray lightcurve of Vela X-1 measured by Swift/BAT over 300 orbital periods of the system and compared it with the predictions of a grid of hydrodynamic simulations. Results: We obtain very good agreement between observations and simulations for a narrow set of parameters, implying that the wind velocity close to the stellar surface is twice higher than usually assumed with the standard beta law. Locally a velocity gradient of β ~ 0.5 is favoured. Even if still incomplete, hydrodynamic simulations successfully reproduce several observational properties of Vela X-1.

  16. Photometric Analysis of Two Candidate Pulsating Early Stars

    NASA Astrophysics Data System (ADS)

    Sonnett, S. M.; Dukes, R. J.

    2004-12-01

    Both HD199122 and HD213617 are found to be periodic with frequencies within the characteristic range of g-mode pulsation for either the Slowly Pulsating B Stars (SPBs) or the Gamma Doradus stars. We began observing HD199122 as a SPB based on its appearance in the list of such stars found through Hipparcos data examination by Koen (MNRAS, 321, 44, 2001). However, as noted by Koen, its reported spectral type A2 is late for an SPB. Based on published photometric indices, he suggests that its spectral type is closer to B7 and thus it is likely to be a SPB. Using Stromgren uvby photometry, we have examined over 600 differential measures of this star. We find two clear frequencies of f1 = 0.80209 c/d and f2 = 0.82444 c/d, which is within the characteristic range for g-mode pulsation of hotter main sequence stars. Our data suggests the possible presence of a third frequency, but confirmation is pending more data analysis. A preliminary analysis of Hipparcos satellite data for HD 213617 proposes a frequency of 0.55672 c/d (Handler, G.MNRAS 309, L19-L23,1999). However, Castellano (private communication) has found a period closer to 0.8 c/d from his analysis of the Hipparcos data. Since this star is an early F type, confirmation of this pulsational value could classify this star as a Gamma Doradus variable. We are presently obtaining observations for both subjects and will continue analysis as data arrives. Observations of HD213617 were begun as part of a summer project as part of the NASA Academy at Ames. This work has been supported by South Carolina Space Grant and NSF grant AST-0071260 to the College of Charleston,.

  17. KNOW THE STAR, KNOW THE PLANET. I. ADAPTIVE OPTICS OF EXOPLANET HOST STARS

    SciTech Connect

    Roberts, Lewis C.; Turner, Nils H.; Ten Brummelaar, Theo A.; Mason, Brian D.; Hartkopf, William I. E-mail: nils@chara-array.org E-mail: bdm@usno.navy.mil

    2011-11-15

    The results of an adaptive optics survey of exoplanet host stars for stellar companions are presented. We used the Advanced Electro-Optical System telescope and its adaptive optics system to collect deep images of the stars in the I band. Sixty-two exoplanet host stars were observed and fifteen multiple star systems were resolved. Of these eight are known multiples, while seven are new candidate binaries. For all binaries, we measured the relative astrometry of the pair and the differential magnitude in the I band. We improved the orbits of HD 19994 and {tau} Boo. These observations will provide improved statistics on the duplicity of exoplanet host stars and provide an increased understanding of the dynamics of known binary star exoplanet hosts.

  18. Detection of a magnetic field on HD108: clues to extreme magnetic braking and the Of?p phenomenon

    NASA Astrophysics Data System (ADS)

    Martins, F.; Donati, J.-F.; Marcolino, W. L. F.; Bouret, J.-C.; Wade, G. A.; Escolano, C.; Howarth, I. D.; Mimes Collaboration

    2010-09-01

    We report the detection of a magnetic field on the Of?p star HD108. Spectropolarimetric observations conducted in 2007, 2008 and 2009, respectively, with NARVAL@Télescope Bernard Lyot (TBL) and Echelle SpectroPolarimetric Device for the Observation of Stars at Canada-France-Hawaii Telescope (ESPaDOnS@CFHT) reveal a clear Zeeman signature in the average Stokes V profile, stable on time-scales of days to months and slowly increasing in amplitude on time-scales of years. We speculate that this time-scale is the same as that on which Hα emission is varying and is equal to the rotation period of the star. The corresponding longitudinal magnetic field, measured during each of the three seasons, increases slowly from 100 to 150 G, implying that the polar strength of the putatively dipolar large-scale magnetic field of HD108 is at least 0.5 kG and most likely of the order of 1-2 kG. The stellar and wind properties are derived through a quantitative spectroscopic analysis with the code CMFGEN. The effective temperature is difficult to constrain because of the unusually strong HeI λλ4471, 5876 lines. Values in the range of 33000-37000K are preferred. A mass-loss rate of about 10-7Msolaryr-1 (with a clumping factor f = 0.01) and a wind terminal velocity of 2000 km s-1 are derived. The wind confinement parameter η* is larger than 100, implying that the wind of HD108 is magnetically confined. Stochastic short-term variability is observed in the wind-sensitive lines but not in the photospheric lines, excluding the presence of pulsations. Material infall in the confined wind is the most likely origin for lines formed in the inner wind. Wind clumping also probably causes part of the Hα variability. The projected rotational velocity of HD108 is lower than 50 km s-1, consistent with the spectroscopic and photometric variation time-scales of a few decades. Overall, HD108 is very similar to the magnetic O star HD191612 except for an even slower rotation. Based on observations

  19. Kuiper belt structure around nearby super-Earth host stars

    NASA Astrophysics Data System (ADS)

    Kennedy, Grant M.; Matrà, Luca; Marmier, Maxime; Greaves, Jane S.; Wyatt, Mark C.; Bryden, Geoffrey; Holland, Wayne; Lovis, Christophe; Matthews, Brenda C.; Pepe, Francesco; Sibthorpe, Bruce; Udry, Stéphane

    2015-05-01

    We present new observations of the Kuiper belt analogues around HD 38858 and HD 20794, hosts of super-Earth mass planets within 1 au. As two of the four nearby G-type stars (with HD 69830 and 61 Vir) that form the basis of a possible correlation between low-mass planets and debris disc brightness, these systems are of particular interest. The disc around HD 38858 is well resolved with Herschel and we constrain the disc geometry and radial structure. We also present a probable James Clerk Maxwell Telescope sub-mm continuum detection of the disc and a CO J = 2-1 upper limit. The disc around HD 20794 is much fainter and appears marginally resolved with Herschel, and is constrained to be less extended than the discs around 61 Vir and HD 38858. We also set limits on the radial location of hot dust recently detected around HD 20794 with near-IR interferometry. We present High Accuracy Radial velocity Planet Searcher upper limits on unseen planets in these four systems, ruling out additional super-Earths within a few au, and Saturn-mass planets within 10 au. We consider the disc structure in the three systems with Kuiper belt analogues (HD 69830 has only a warm dust detection), concluding that 61 Vir and HD 38858 have greater radial disc extent than HD 20794. We speculate that the greater width is related to the greater minimum planet masses (10-20 M⊕ versus 3-5 M⊕), arising from an eccentric planetesimal population analogous to the Solar system's scattered disc. We discuss alternative scenarios and possible means to distinguish among them.

  20. Know the Star, Know the Planet. 2. Speckle Interferometry of Exoplanet Host Stars

    DTIC Science & Technology

    2011-11-01

    reserved. Printed in the U.S.A. KNOW THE STAR, KNOW THE PLANET. II. SPECKLE INTERFEROMETRY OF EXOPLANET HOST STARS Brian D. Mason1,6, William I. Hartkopf1,6...October 17 ABSTRACT A study of the host stars to exoplanets is important for understanding their environment. To that end, we report new speckle...observations of a sample of exoplanet host primaries. The bright exoplanet host HD 8673 (= HIP 6702) is revealed to have a companion, although at this time we

  1. The Properties of Exomoons Around the Habitable Zone Planets, Kepler 22b and HD160691b

    NASA Astrophysics Data System (ADS)

    Bokorney, Jake; Fuse, Christopher R.

    2016-01-01

    As part of a larger study to understand the formation, evolution, and stability of exoplanet satellites, we have examined the Kepler 22 and HD160691 systems. Habitable zone planets (Kopparapu et al. 2013) are found in each system, with Kepler 22b at 0.85 AU and HD160691b at 1.5 AU. While these planets may be habitable, systems of satellites also hold the potential of supporting life. A series of N-body simulations were performed to examine the most stable configuration of moons orbiting each planet. A moonlet disk was designed to span 10 - 80% of the planet's Hill sphere (Ksting et al. 1993). The 100 bodies (mdisk/mplanet = 2 × 10-4) within the disk were randomly placed around each planet. Simulations were run for 500 kyrs, with the star, planets, and moonlets allowed to gravitationally evolve. The Kepler 22b system was able to retain three to four moons in 96% of the simulations, while the HD160691b systems had a stable pair of moons in 73% of the simulations. The remaining simulations produced systems with moons on highly eccentric orbits.

  2. ALMA CONTINUUM OBSERVATIONS OF A 30 Myr OLD GASEOUS DEBRIS DISK AROUND HD 21997

    SciTech Connect

    Moór, A.; Ábrahám, P.; Kiss, Cs.; Gabányi, K.; Juhász, A.; Schmalzl, M.; Kóspál, Á.; Apai, D.; Pascucci, I.; Csengeri, T.; Grady, C.; Henning, Th.; Hughes, A. M.

    2013-11-10

    Circumstellar disks around stars older than 10 Myr are expected to be gas-poor. There are, however, two examples of old (30-40 Myr) debris-like disks containing a detectable amount of cold CO gas. Here we present Atacama Large Millimeter/Submillimeter Array (ALMA) and Herschel Space Observatory observations of one of these disks, around HD 21997, and study the distribution and origin of the dust and its connection to the gas. Our ALMA continuum images at 886 μm clearly resolve a broad ring of emission within a diameter of ∼4.''5, adding HD 21997 to the dozen debris disks resolved at (sub)millimeter wavelengths. Modeling the morphology of the ALMA image with a radiative transfer code suggests inner and outer radii of ∼55 and ∼150 AU, and a dust mass of 0.09 M {sub ⊕}. Our data and modeling hints at an extended cold outskirt of the ring. Comparison with the morphology of the CO gas in the disk reveals an inner dust-free hole where gas nevertheless can be detected. Based on dust grain lifetimes, we propose that the dust content of this gaseous disk is of secondary origin and is produced by planetesimals. Since the gas component is probably primordial, HD 21997 is one of the first known examples of a hybrid circumstellar disk, a thus-far little studied late phase of circumstellar disk evolution.

  3. Signatures of hot hydrogen in the atmosphere of the extrasolar planet HD209458b

    NASA Astrophysics Data System (ADS)

    Sing, David; Ballester, G.

    2007-05-01

    Of the extrasolar planets detected so far, about 10% consist of giant planets which orbit very close to their parent stars. The atmospheres of these ``hot-Jupiters'' are largely heated by the immense stellar irradiation. In the case of the planet HD209458b, this energy deposition results in a hydrodynamic state in the upper atmosphere, allowing for sizable expansion and escape of neutral hydrogen gas. Here we report the first detection of absorption by hot (n=2) hydrogen in the optical and near-ultraviolet Balmer jump and continuum in any planet. The hot H I signature appears as a short-wavelength absorption 0.030+\\-0.006 below the value of 0.9855 calculated from the latest values for the radius of the planet. So far, the lower atmosphere and the full extended upper atmosphere of HD209458b have been observed. This work probes a layer where the escaping gas forms in HD209458b's upper atmosphere, providing a new way to study the atmospheric structure and complex escape processes of extrasolar hot-Jupiters.

  4. Reconstructing the high-energy irradiation of the evaporating hot Jupiter HD 209458b

    NASA Astrophysics Data System (ADS)

    Louden, Tom; Wheatley, Peter J.; Briggs, Kevin

    2017-01-01

    The atmosphere of the exoplanet HD 209458b is undergoing sustained mass loss, believed to be caused by X-ray and extreme-ultraviolet (XUV) irradiation from its star. The majority of this flux is not directly observable due to interstellar absorption, but is required in order to correctly model the photoevaporation of the planet and photoionization of the outflow. We present a recovered high-energy spectrum for HD 209458 using a differential emission measure retrieval technique. We construct a model of the stellar corona and transition region for temperatures between 104.1 and 108 K which is constrained jointly by ultraviolet line strengths, measured with the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST) and X-ray flux measurements from XMM-Newton. The total hydrogen ionizing luminosity (λ < 912 Å) is found to be 1028.26 erg s-1, which is similar to the value for the mean activity level of the Sun. This luminosity is incompatible with energy-limited mass-loss rates estimated from the same COS data set, even the lower bound requires an uncomfortably high energetic efficiency of >40 per cent. However, our luminosity is compatible with early estimates of the mass-loss rate of HD 209458b, based on results from the HST Space Telescope Imaging Spectrograph. Precisely, reconstructed XUV irradiation is a key input to determining mass-loss rates and efficiencies for exoplanet atmospheres.

  5. A YOUNG PROTOPLANET CANDIDATE EMBEDDED IN THE CIRCUMSTELLAR DISK OF HD 100546

    SciTech Connect

    Quanz, Sascha P.; Amara, Adam; Meyer, Michael R.; Kenworthy, Matthew A.; Kasper, Markus; Girard, Julien H.

    2013-03-20

    We present high-contrast observations of the circumstellar environment of the Herbig Ae/Be star HD 100546. The final 3.8 {mu}m image reveals an emission source at a projected separation of 0.''48 {+-} 0.''04 (corresponding to {approx}47 {+-} 4 AU) at a position angle of 8. Degree-Sign 9 {+-} 0. Degree-Sign 9. The emission appears slightly extended with a point source component with an apparent magnitude of 13.2 {+-} 0.4 mag. The position of the source coincides with a local deficit in polarization fraction in near-infrared polarimetric imaging data, which probes the surface of the well-studied circumstellar disk of HD 100546. This suggests a possible physical link between the emission source and the disk. Assuming a disk inclination of {approx}47 Degree-Sign , the de-projected separation of the object is {approx}68 AU. Assessing the likelihood of various scenarios, we favor an interpretation of the available high-contrast data with a planet in the process of forming. Follow-up observations in the coming years can easily distinguish between the different possible scenarios empirically. If confirmed, HD 100546 ''b'' would be a unique laboratory to study the formation process of a new planetary system, with one giant planet currently forming in the disk and a second planet possibly orbiting in the disk gap at smaller separations.

  6. THE TRENDS HIGH-CONTRAST IMAGING SURVEY. II. DIRECT DETECTION OF THE HD 8375 TERTIARY

    SciTech Connect

    Crepp, Justin R.; Johnson, John Asher; Yantek, Scott M.; Howard, Andrew W.; Marcy, Geoff W.; Isaacson, Howard; Fischer, Debra A.; Wright, Jason T.; Feng Ying

    2013-07-01

    We present the direct imaging detection of a faint tertiary companion to the single-lined spectroscopic binary HD 8375 AB. Initially noticed as an 53 m s{sup -1} yr{sup -1} Doppler acceleration by Bowler et al., we have obtained high-contrast adaptive optics observations at Keck using NIRC2 that spatially resolve HD 8375 C from its host(s). Astrometric measurements demonstrate that the companion shares a common proper-motion. We detect orbital motion in a clockwise direction. Multiband relative photometry measurements are consistent with an early M-dwarf spectral type ({approx}M1V). Our combined Doppler and imaging observations place a lower-limit of m {>=} 0.297 M{sub Sun} on its dynamical mass. We also provide a refined orbit for the inner pair using recent radial velocity measurements obtained with the High Resolution Echelle Spectrometer. HD 8375 is one of many triple-star systems that are apparently missing in the solar neighborhood.

  7. Three Temperate Neptunes Orbiting Nearby Stars

    NASA Astrophysics Data System (ADS)

    Fulton, Benjamin J.; Howard, Andrew W.; Weiss, Lauren M.; Sinukoff, Evan; Petigura, Erik A.; Isaacson, Howard; Hirsch, Lea; Marcy, Geoffrey W.; Henry, Gregory W.; Grunblatt, Samuel K.; Huber, Daniel; von Braun, Kaspar; Boyajian, Tabetha S.; Kane, Stephen R.; Wittrock, Justin; Horch, Elliott P.; Ciardi, David R.; Howell, Steve B.; Wright, Jason T.; Ford, Eric B.

    2016-10-01

    We present the discovery of three modestly irradiated, roughly Neptune-mass planets orbiting three nearby Solar-type stars. HD 42618 b has a minimum mass of 15.4 ± 2.4 {M}\\oplus , a semimajor axis of 0.55 au, an equilibrium temperature of 337 K, and is the first planet discovered to orbit the solar analogue host star, HD 42618. We also discover new planets orbiting the known exoplanet host stars HD 164922 and HD 143761 (ρ CrB). The new planet orbiting HD 164922 has a minimum mass of 12.9 ± 1.6 {M}\\oplus and orbits interior to the previously known Jovian mass planet orbiting at 2.1 au. HD 164922 c has a semimajor axis of 0.34 au and an equilibrium temperature of 418 K. HD 143761 c orbits with a semimajor axis of 0.44 au, has a minimum mass of 25 ± 2 {M}\\oplus , and is the warmest of the three new planets with an equilibrium temperature of 445 K. It orbits exterior to the previously known warm Jupiter in the system. A transit search using space-based CoRoT data and ground-based photometry from the Automated Photometric Telescopes (APTs) at Fairborn Observatory failed to detect any transits, but the precise, high-cadence APT photometry helped to disentangle planetary-reflex motion from stellar activity. These planets were discovered as part of an ongoing radial velocity survey of bright, nearby, chromospherically inactive stars using the Automated Planet Finder (APF) telescope at Lick Observatory. The high-cadence APF data combined with nearly two decades of radial velocity data from Keck Observatory and gives unprecedented sensitivity to both short-period low-mass, and long-period intermediate-mass planets. Based on observations obtained at the W. M. Keck Observatory, which is operated jointly by the University of California and the California Institute of Technology. Keck time was granted for this project by the University of Hawai‘i, the University of California, and NASA.

  8. Exoplanet Atmospheres in High Definition: 3D Eclipse Mapping of HD 209458b and HD 189733b

    NASA Astrophysics Data System (ADS)

    Lewis, Nikole; Cowan, Nicolas; Knutson, Heather; de Wit, Julien; Seager, Sara; Demory, Brice-Olivier; Fortney, Jonathan; Showman, Adam

    2013-10-01

    Eclipse mapping is a newly developed technique in the arsenal of observational methods aimed at the characterization of exoplanet atmospheres. This technique was first applied to HD189733b using multiple 8 micron secondary eclipse observations to create a high-resolution snapshot of the dayside of the planet. The eclipse map of HD189733b at 8 microns was able to resolve the dayside brightness distribution of the planet both in latitude and longitude giving key insights into the atmospheric circulation of HD189733b. Here we propose to use this eclipse mapping technique to produce dayside brightness maps of the benchmark exoplanets HD189733b and HD209458b at both 3.6 and 4.5 microns. By combining brightness maps at multiple wavelengths, we will create the first three-dimensional maps of an exoplanet atmosphere (latitude, longitude, and pressure). HD209458 and HD189733 are among the brightest (Ks~6) planet harboring system and represent our best opportunity to achieve a high signal-to-noise eclipse maps. Comparisons between the brightness maps of these two planets will highlight key differences in the atmospheric circulation patterns of planets with (HD209458b) and without (HD189733b) thermal inversions in their dayside atmospheres. The atmospheres of HD189733b and HD209458b have been previously probed at wavelengths from the infrared to the ultraviolet through transit, eclipse, and phase-curve observations. With the addition of the three-dimensional eclipse maps proposed here, we will answer many of the outstanding questions about the basic radiative, chemical, and advective processes at work in these key planetary atmospheres. The observations proposed here will allow us to make the first direct comparisons of the observed thermal structure of an exoplanet with the plethora of three-dimensional atmospheric circulation models developed specifically for HD189733b and HD209458b, thus both informing the models and gaining new insights into the complex circulation

  9. The discovery of nonthermal radio emission from magnetic Bp-Ap stars

    NASA Technical Reports Server (NTRS)

    Drake, Stephen A.; Abbott, David C.; Bastian, T. S.; Bieging, J. H.; Churchwell, E.

    1987-01-01

    In a VLA survey of chemically peculiar B- and A-type stars with strong magnetic fields, five of the 34 stars observed have been identified as 6 cm continuum sources. Three of the detections are helium-strong early Bp stars (Sigma Ori E, HR 1890, and Delta Ori C), and two are helium weak, silicon-strong stars with spectral types near A0p (IQ Aur = HD 34452, Babcock's star = HD 215441). The 6 cm luminosities L6 (ergs/s Hz) range from log L6 = 16.2 to 17.9, somewhat less than the OB supergiants and W-R stars. Three-frequency observations indicate that the helium-strong Bp stars are variable nonthermal sources.

  10. Heavy Metal Stars

    NASA Astrophysics Data System (ADS)

    2001-08-01

    La Silla Telescope Detects Lots of Lead in Three Distant Binaries Summary Very high abundances of the heavy element Lead have been discovered in three distant stars in the Milky Way Galaxy . This finding strongly supports the long-held view that roughly half of the stable elements heavier than Iron are produced in common stars during a phase towards the end of their life when they burn their Helium - the other half results from supernova explosions. All the Lead contained in each of the three stars weighs about as much as our Moon. The observations show that these "Lead stars" - all members of binary stellar systems - have been more enriched with Lead than with any other chemical element heavier than Iron. This new result is in excellent agreement with predictions by current stellar models about the build-up of heavy elements in stellar interiors. The new observations are reported by a team of Belgian and French astronomers [1] who used the Coude Echelle Spectrometer on the ESO 3.6-m telescope at the La Silla Observatory (Chile). PR Photo 26a/01 : A photo of HD 196944 , one of the "Lead stars". PR Photo 26b/01 : A CES spectrum of HD 196944 . The build-up of heavy elements Astronomers and physicists denote the build-up of heavier elements from lighter ones as " nucleosynthesis ". Only the very lightest elements (Hydrogen, Helium and Lithium [2]) were created at the time of the Big Bang and therefore present in the early universe. All the other heavier elements we now see around us were produced at a later time by nucleosynthesis inside stars. In those "element factories", nuclei of the lighter elements are smashed together whereby they become the nuclei of heavier ones - this process is known as nuclear fusion . In our Sun and similar stars, Hydrogen is being fused into Helium. At some stage, Helium is fused into Carbon, then Oxygen, etc. The fusion process requires positively charged nuclei to move very close to each other before they can unite. But with increasing

  11. The McDonald Observatory Planet Search: New Long-period Giant Planets and Two Interacting Jupiters in the HD 155358 System

    NASA Astrophysics Data System (ADS)

    Robertson, Paul; Endl, Michael; Cochran, William D.; MacQueen, Phillip J.; Wittenmyer, Robert A.; Horner, J.; Brugamyer, Erik J.; Simon, Attila E.; Barnes, Stuart I.; Caldwell, Caroline

    2012-04-01

    We present high-precision radial velocity (RV) observations of four solar-type (F7-G5) stars—HD 79498, HD 155358, HD 197037, and HD 220773—taken as part of the McDonald Observatory Planet Search Program. For each of these stars, we see evidence of Keplerian motion caused by the presence of one or more gas giant planets in long-period orbits. We derive orbital parameters for each system and note the properties (composition, activity, etc.) of the host stars. While we have previously announced the two-gas-giant HD 155358 system, we now report a shorter period for planet c. This new period is consistent with the planets being trapped in mutual 2:1 mean-motion resonance. We therefore perform an in-depth stability analysis, placing additional constraints on the orbital parameters of the planets. These results demonstrate the excellent long-term RV stability of the spectrometers on both the Harlan J. Smith 2.7 m telescope and the Hobby-Eberly telescope.

  12. The 4.5 μm full-orbit phase curve of the hot Jupiter HD 209458b

    SciTech Connect

    Zellem, Robert T.; Griffith, Caitlin A.; Showman, Adam P.; Lewis, Nikole K.; Knutson, Heather A.; Fortney, Jonathan J.; Laughlin, Gregory; Cowan, Nicolas B.; Agol, Eric; Burrows, Adam; Charbonneau, David; Deming, Drake; Langton, Jonathan

    2014-07-20

    The hot Jupiter HD 209458b is particularly amenable to detailed study as it is among the brightest transiting exoplanet systems currently known (V-mag = 7.65; K-mag = 6.308) and has a large planet-to-star contrast ratio. HD 209458b is predicted to be in synchronous rotation about its host star with a hot spot that is shifted eastward of the substellar point by superrotating equatorial winds. Here we present the first full-orbit observations of HD 209458b, in which its 4.5 μm emission was recorded with Spitzer/IRAC. Our study revises the previous 4.5 μm measurement of HD 209458b's secondary eclipse emission downward by ∼35% to 0.1391%{sub −0.0069%}{sup +0.0072%}, changing our interpretation of the properties of its dayside atmosphere. We find that the hot spot on the planet's dayside is shifted eastward of the substellar point by 40.°9 ± 6.°0, in agreement with circulation models predicting equatorial superrotation. HD 209458b's dayside (T{sub bright} = 1499 ± 15 K) and nightside (T{sub bright} = 972 ± 44 K) emission indicate a day-to-night brightness temperature contrast smaller than that observed for more highly irradiated exoplanets, suggesting that the day-to-night temperature contrast may be partially a function of the incident stellar radiation. The observed phase curve shape deviates modestly from global circulation model predictions potentially due to disequilibrium chemistry or deficiencies in the current hot CH{sub 4} line lists used in these models. Observations of the phase curve at additional wavelengths are needed in order to determine the possible presence and spatial extent of a dayside temperature inversion, as well as to improve our overall understanding of this planet's atmospheric circulation.

  13. The orbital motion, absolute mass and high-altitude winds of exoplanet HD 209458b.

    PubMed

    Snellen, Ignas A G; de Kok, Remco J; de Mooij, Ernst J W; Albrecht, Simon

    2010-06-24

    For extrasolar planets discovered using the radial velocity method, the spectral characterization of the host star leads to a mass estimate of the star and subsequently of the orbiting planet. If the orbital velocity of the planet could be determined, the masses of both star and planet could be calculated using Newton's law of gravity, just as in the case of stellar double-line eclipsing binaries. Here we report high-dispersion ground-based spectroscopy of a transit of the extrasolar planet HD 209458b. We see a significant wavelength shift in absorption lines from carbon monoxide in the planet's atmosphere, which we conclude arises from a change in the radial component of the planet's orbital velocity. The masses of the star and planet are 1.00 +/- 0.22M(Sun) and 0.64 +/- 0.09M(Jup) respectively. A blueshift of the carbon monoxide signal of approximately 2 km s(-1) with respect to the systemic velocity of the host star suggests the presence of a strong wind flowing from the irradiated dayside to the non-irradiated nightside of the planet within the 0.01-0.1 mbar atmospheric pressure range probed by these observations. The strength of the carbon monoxide signal suggests a carbon monoxide mixing ratio of (1-3) x 10(-3) in this planet's upper atmosphere.

  14. A Herschel resolved far-infrared dust ring around HD 207129

    NASA Astrophysics Data System (ADS)

    Marshall, J. P.; Löhne, T.; Montesinos, B.; Krivov, A. V.; Eiroa, C.; Absil, O.; Bryden, G.; Maldonado, J.; Mora, A.; Sanz-Forcada, J.; Ardila, D.; Augereau, J.-Ch.; Bayo, A.; Del Burgo, C.; Danchi, W.; Ertel, S.; Fedele, D.; Fridlund, M.; Lebreton, J.; González-García, B. M.; Liseau, R.; Meeus, G.; Müller, S.; Pilbratt, G. L.; Roberge, A.; Stapelfeldt, K.; Thébault, P.; White, G. J.; Wolf, S.

    2011-05-01

    Context. Dusty debris discs around main sequence stars are thought to be the result of continuous collisional grinding of planetesimals in the system. The majority of these systems are unresolved and analysis of the dust properties is limited by the lack of information regarding the dust location. Aims: The Herschel DUNES key program is observing 133 nearby, Sun-like stars (<20 pc, FGK spectral type) in a volume limited survey to constrain the absolute incidence of cold dust around these stars by detection of far infrared excess emission at flux levels comparable to the Edgeworth-Kuiper belt (EKB). Methods: We have observed the Sun-like star HD 207129 with Herschel PACS and SPIRE. In all three PACS bands we resolve a ring-like structure consistent with scattered light observations. Using α Boötis as a reference point spread function (PSF), we deconvolved the images, clearly resolving the inner gap in the disc at both 70 and 100 μm. Results: We have resolved the dust-producing planetesimal belt of a debris disc at 100 μm for the first time. We measure the radial profile and fractional luminosity of the disc, and compare the values to those of discs around stars of similar age and/or spectral type, placing this disc in context of other resolved discs observed by Herschel/DUNES. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  15. BINARIES AMONG DEBRIS DISK STARS

    SciTech Connect

    Rodriguez, David R.; Zuckerman, B.

    2012-02-01

    We have gathered a sample of 112 main-sequence stars with known debris disks. We collected published information and performed adaptive optics observations at Lick Observatory to determine if these debris disks are associated with binary or multiple stars. We discovered a previously unknown M-star companion to HD 1051 at a projected separation of 628 AU. We found that 25% {+-} 4% of our debris disk systems are binary or triple star systems, substantially less than the expected {approx}50%. The period distribution for these suggests a relative lack of systems with 1-100 AU separations. Only a few systems have blackbody disk radii comparable to the binary/triple separation. Together, these two characteristics suggest that binaries with intermediate separations of 1-100 AU readily clear out their disks. We find that the fractional disk luminosity, as a proxy for disk mass, is generally lower for multiple systems than for single stars at any given age. Hence, for a binary to possess a disk (or form planets) it must either be a very widely separated binary with disk particles orbiting a single star or it must be a small separation binary with a circumbinary disk.

  16. FUSE Observations of HD 5980: The Wind Structure of the Eruptor

    NASA Astrophysics Data System (ADS)

    Koenigsberger, Gloria; Fullerton, Alexander W.; Massa, Derck; Auer, Lawrence H.

    2006-10-01

    HD 5980 is a unique system containing one massive star (star A) that is apparently entering the luminous blue variable phase and an eclipsing companion (star B) that may have already evolved beyond this phase to become a Wolf-Rayet star. In this paper we present the results from FUSE observations obtained in 1999, 2000, and 2002, and one far-UV observation obtained by ORFEUS BEFS in 1993 shortly before the first eruption of HD 5980. The eight phase-resolved spectra obtained by FUSE in 2002 are analyzed in the context of a wind-eclipse model. This analysis shows that the wind of the eruptor obeyed a very fast velocity law in 2002, which is consistent with the line-driving mechanism. Large-amplitude line-profile variations on the orbital period are shown to be due to the eclipse of star B by the wind of star A, although the eclipse due to gas flowing in the direction of star B is absent. This can only be explained if the wind of star A is not spherically symmetric or if the eclipsed line radiation is ``filled in'' by emission originating from somewhere else in the system, e.g., in the wind-wind collision region. Except for a slightly lower wind speed, the ORFEUS BEFS spectrum is very similar to the spectrum obtained by FUSE at the same orbital phase; there is no indication of the impending eruption. However, the trend for decreasing wind velocity suggests the occurrence of the ``bistability'' mechanism, which in turn implies that the restructuring of the circumbinary environment caused by the transition from fast, rarefied wind to slow, dense wind was observed as the eruptive event. The underlying mechanism responsible for the long-term decrease in wind velocity that precipitated this change remains an open issue. Based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by The Johns Hopkins University under NASA contract NAS5-32985.

  17. HD 35502: a hierarchical triple system with a magnetic B5IVpe primary

    NASA Astrophysics Data System (ADS)

    Sikora, J.; Wade, G. A.; Bohlender, D. A.; Shultz, M.; Adelman, S. J.; Alecian, E.; Hanes, D.; Monin, D.; Neiner, C.; MiMeS Collaboration; BinaMIcS Collaboration

    2016-08-01

    We present our analysis of HD 35502 based on high- and medium-resolution spectropolarimetric observations. Our results indicate that the magnetic B5IVsnp star is the primary component of a spectroscopic triple system and that it has an effective temperature of 18.4 ± 0.6 kK, a mass of 5.7 ± 0.6 M⊙, and a polar radius of 3.0^{+1.1}_{-0.5} R_{odot }. The two secondary components are found to be essentially identical A-type stars for which we derive effective temperatures (8.9 ± 0.3 kK), masses (2.1 ± 0.2 M⊙), and radii (2.1 ± 0.4 R⊙). We infer a hierarchical orbital configuration for the system in which the secondary components form a tight binary with an orbital period of 5.668 66(6) d that orbits the primary component with a period of over 40 yr. Least-Squares Deconvolution profiles reveal Zeeman signatures in Stokes V indicative of a longitudinal magnetic field produced by the B star ranging from approximately -4 to 0 kG with a median uncertainty of 0.4 kG. These measurements, along with the line variability produced by strong emission in Hα, are used to derive a rotational period of 0.853 807(3) d. We find that the measured v sin i = 75 ± 5 km s-1 of the B star then implies an inclination angle of the star's rotation axis to the line of sight of 24^{+6}_{-10}{}^circ. Assuming the Oblique Rotator Model, we derive the magnetic field strength of the B star's dipolar component (14^{+9}_{-3} kG) and its obliquity (63± 13deg). Furthermore, we demonstrate that the calculated Alfvén radius (41^{+17}_{-6}R_ast) and Kepler radius (2.1^{+0.4}_{-0.7}R_ast) place HD 35502's central B star well within the regime of centrifugal magnetosphere-hosting stars.

  18. The magnetic field of the double-lined spectroscopic binary system HD 5550

    NASA Astrophysics Data System (ADS)

    Alecian, E.; Tkachenko, A.; Neiner, C.; Folsom, C. P.; Leroy, B.

    2016-05-01

    Context. The origin of fossil fields in intermediate- and high-mass stars is poorly understood, as is the interplay between binarity and magnetism during stellar evolution. Thus we have begun a study of the magnetic properties of a sample of intermediate-mass and massive short-period binary systems as a function of binarity properties. Aims: This paper specifically aims to characterise the magnetic field of HD 5550, a double-lined spectroscopic binary system of intermediate mass. Methods: We gathered 25 high-resolution spectropolarimetric observations of HD 5550 using the instrument Narval. We first fitted the intensity spectra using Zeeman/ATLAS9 LTE synthetic spectra to estimate the effective temperatures, microturbulent velocities, and the abundances of some elements of both components, as well as the light ratio of the system. We then applied the multi-line least-square deconvolution (LSD) technique to the intensity and circularly polarised spectra, which provided us with mean LSD I and V line profiles. We fitted the Stokes I line profiles to determine the radial and projected rotational velocities of both stars. We then analysed the shape and evolution of the V profiles using the oblique rotator model to characterise the magnetic fields of both stars. Results: We confirm the Ap nature of the primary, which has previously been reported, and find that the secondary displays spectral characteristics typical of an Am star. While a magnetic field is clearly detected in the lines of the primary, no magnetic field is detected in the secondary in any of our observations. If a dipolar field were present at the surface of the Am star, its polar strength must be below 40 G. The faint variability observed in the Stokes V profiles of the Ap star allowed us to propose a rotation period of 6.84-0.39+0.61 d, which is close to the orbital period (~6.82 d), suggesting that the star is synchronised with its orbit. By fitting the variability of the V profiles, we propose that the

  19. Commissioning an Elekta Versa HD linear accelerator.

    PubMed

    Narayanasamy, Ganesh; Saenz, Daniel; Cruz, Wilbert; Ha, Chul S; Papanikolaou, Niko; Stathakis, Sotirios

    2016-01-08

    The purpose of this study is to report the dosimetric aspects of commissioning performed on an Elekta Versa HD linear accelerator (linac) with high-dose-rate flattening filter-free (FFF) photon modes and electron modes. Acceptance and commissioning was performed on the Elekta Versa HD linac with five photon energies (6 MV, 10 MV, 18 MV, 6 MV FFF, 10 MV FFF), four electron energies (6 MeV, 9MeV, 12 MeV, 15 MeV) and 160-leaf (5 mm wide) multileaf collimators (MLCs). Mechanical and dosimetric data were measured and evaluated. The measurements include percent depth doses (PDDs), in-plane and cross-plane profiles, head scatter factor (Sc), relative photon output factors (Scp), universal wedge transmission factor, MLC transmission factors, and electron cone factors. Gantry, collimator, and couch isocentricity measurements were within 1 mm, 0.7 mm, and 0.7 mm diameter, respectively. The PDDs of 6 MV FFF and 10 MV FFF beams show deeper dmax and steeper falloff with depth than the corresponding flattened beams. While flatness values of 6 MV FFF and 10 MV FFF normalized profiles were expectedly higher than the corresponding flattened beams, the symmetry values were almost identical. The cross-plane penumbra values were higher than the in-plane penumbra values for all the energies. The MLC transmission values were 0.5%, 0.6%, and 0.6% for 6 MV, 10 MV, and 18 MV photon beams, respectively. The electron PDDs, profiles, and cone factors agree well with the literature. The outcome of radiation treatment is directly related to the accuracy in the dose modeled in the treatment planning system, which is based on the commissioned data. Commissioning data provided us a valuable insight into the dosimetric characteristics of the beam. This set of commissioning data can provide comparison data to others performing Versa HD commissioning, thereby improving patient safety.

  20. The Transiting Exocomets of HD 172555

    NASA Technical Reports Server (NTRS)

    Grady, C. A.; Brown, Alex; Kamp, Inga; Riviere-Marichalar, Pablo; Roberge, Aki; Welsh, Barry

    2016-01-01

    While most attention has been garnered by searches for super-Jovian mass exo-planets the presence of minor bodies can be detected, at least through their dissociation products in suitably oriented systems. The principal detection technique is line-of-sight absorption spectroscopy of systems viewed close to edge-on. I review what we have learned about such bodies in beta Pictoris, and HD 172555, their link to more massive bodies in their systems, and what this tells us about the frequency and potential locations of Jovian-mass bodies in advance of their direct imaging detection.

  1. A new interstellar component in the spectrum of HD 72127A

    NASA Technical Reports Server (NTRS)

    Hobbs, L. M.; Wallerstein, G.; Huu, E. M.

    1982-01-01

    New high dispersion observations are reported of the very strong, broad interstellar K line of Ca II in the spectrum of HD 72127A, a star located near a filament of the Vela supernova remnant. When compared with similar observations made in 1977, the new data reveal temporal variability of the interstellar absorption, as shown both by the presence of a new, sixth line component and by a 25% increase in the total equivalent width of the K line. All five Ca II components which were seen in both years show very large column-density ratios N(Ca II) /N(Na I) at least equal to 9, probably arising from anomalously large interstellar gas-phase abundances of Ca caused by disruption of interstellar grains. Marked differences in the structure of the K line between the two early-type components of this binary star, which are separated by only 3000 AU, are confirmed.

  2. Abundance analysis of the halo giant HD 122563 with three-dimensional model stellar atmospheres

    NASA Astrophysics Data System (ADS)

    Collet, R.; Nordlund, Å.; Asplund, M.; Hayek, W.; Trampedach, R.

    We present a preliminary local thermodynamic equilibrium (LTE) abundance analysis of the template halo red giant HD122563 based on a realistic, three-dimensional (3D), time-dependent, hydrodynamical model atmosphere of the very metal-poor star. We compare the results of the 3D analysis with the abundances derived by means of a s