Sample records for absolute radial velocities

  1. Confirmation of radial velocity variability in Arcturus

    NASA Technical Reports Server (NTRS)

    Cochran, William D.

    1988-01-01

    The paper presents results of high-precision measurements of radial-velocity variations in Alpha Boo. Significant radial-velocity variability is detected well in excess of the random and systematic measurement errors. The radial velocity varies by an amount greater than 200 m/sec with a period of around 2 days.

  2. Radial velocity studies of cool stars.

    PubMed

    Jones, Hugh R A; Barnes, John; Tuomi, Mikko; Jenkins, James S; Anglada-Escude, Guillem

    2014-04-28

    Our current view of exoplanets is one derived primarily from solar-like stars with a strong focus on understanding our Solar System. Our knowledge about the properties of exoplanets around the dominant stellar population by number, the so-called low-mass stars or M dwarfs, is much more cursory. Based on radial velocity discoveries, we find that the semi-major axis distribution of M dwarf planets appears to be broadly similar to those around more massive stars and thus formation and migration processes might be similar to heavier stars. However, we find that the mass of M dwarf planets is relatively much lower than the expected mass dependency based on stellar mass and thus infer that planet formation efficiency around low-mass stars is relatively impaired. We consider techniques to overcome the practical issue of obtaining good quality radial velocity data for M dwarfs despite their faintness and sustained activity and emphasize (i) the wavelength sensitivity of radial velocity signals, (ii) the combination of radial velocity data from different experiments for robust detection of small amplitude signals, and (iii) the selection of targets and radial velocity interpretation of late-type M dwarfs should consider Hα behaviour.

  3. Long-term radial-velocity variations of the Sun as a star: The HARPS view

    NASA Astrophysics Data System (ADS)

    Lanza, A. F.; Molaro, P.; Monaco, L.; Haywood, R. D.

    2016-03-01

    Context. Stellar radial velocities play a fundamental role in the discovery of extrasolar planets and the measurement of their physical parameters as well as in the study of stellar physical properties. Aims: We investigate the impact of the solar activity on the radial velocity of the Sun using the HARPS spectrograph to obtain measurements that can be directly compared with those acquired in the extrasolar planet search programmes. Methods: We used the Moon, the Galilean satellites, and several asteroids as reflectors to measure the radial velocity of the Sun as a star and correlated this velocity with disc-integrated chromospheric and magnetic indexes of solar activity that are similar to stellar activity indexes. We discuss in detail the systematic effects that affect our measurements and the methods to account for them. Results: We find that the radial velocity of the Sun as a star is positively correlated with the level of its chromospheric activity at ~95 percent significance level. The amplitude of the long-term variation measured in the 2006-2014 period is 4.98 ± 1.44 m/s, which is in good agreement with model predictions. The standard deviation of the residuals obtained by subtracting a linear best fit is 2.82 m/s and is due to the rotation of the reflecting bodies and the intrinsic variability of the Sun on timescales shorter than the activity cycle. A correlation with a lower significance is detected between the radial velocity and the mean absolute value of the line-of-sight photospheric magnetic field flux density. Conclusions: Our results confirm similar correlations found in other late-type main-sequence stars and provide support to the predictions of radial velocity variations induced by stellar activity based on current models.

  4. Illumination Profile & Dispersion Variation Effects on Radial Velocity Measurements

    NASA Astrophysics Data System (ADS)

    Grieves, Nolan; Ge, Jian; Thomas, Neil B.; Ma, Bo; Li, Rui; SDSS-III

    2015-01-01

    The Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS) measures radial velocities using a fiber-fed dispersed fixed-delay interferometer (DFDI) with a moderate dispersion spectrograph. This setup allows a unique insight into the 2D illumination profile from the fiber on to the dispersion grating. Illumination profile investigations show large changes in the profile over time and fiber location. These profile changes are correlated with dispersion changes and long-term radial velocity offsets, a major problem within the MARVELS radial velocity data. Characterizing illumination profiles creates a method to both detect and correct radial velocity offsets, allowing for better planet detection. Here we report our early results from this study including improvement of radial velocity data points from detected giant planet candidates. We also report an illumination profile experiment conducted at the Kitt Peak National Observatory using the EXPERT instrument, which has a DFDI mode similar to MARVELS. Using profile controlling octagonal-shaped fibers, long term offsets over a 3 month time period were reduced from ~50 m/s to within the photon limit of ~4 m/s.

  5. The radial velocity search for extrasolar planets

    NASA Technical Reports Server (NTRS)

    Mcmillan, Robert S.

    1991-01-01

    Radial velocity measurements are being made to search for planets orbiting stars other than the Sun. The reflex acceleration induced on stars by planets can be sensed by measuring the small, slow changes in the line-of-site velocities of stars. To detect these planetary perturbations, the data series must be made on a uniform instrumental scale for as long as it takes a planet to orbit its star. A spectrometer of extreme stability and unprecedented sensitivity to changes in stellar radial velocities was operated.

  6. A Catalogue of Galaxies Having Radial Velocities: Volume 15: Part 7

    NASA Technical Reports Server (NTRS)

    Fredrick, L. W.; Gutsch, W. A.

    1974-01-01

    A tabulation of galaxies which have radial velocities is presented. The parameters of each galaxy are: (1) an abbreviation for the catalog designation, (2) RA(1950), (3) Dec. (1950), (4) new galactic longitude, (5) new galactic latitude, (6) morphological type, (7) magnitude, (8) observed radial velocity in kilometers per second (9) radial velocity corrected for solar motion, and (10) estimated error in radial velocity in kilometers per second.

  7. Space Motions of Low-Mass Stars. II: Radial Velocities

    NASA Astrophysics Data System (ADS)

    Upgren, A. R.; Harlow, J. J. B.

    1996-01-01

    Radial velocities are presented for 53 dwarf K and M stars, eight of which are radial velocity standards. This is the second list in a program to determine space motions for all of the stars in the McCormick lists of dwarf stars. The observations reported here differ from those of the first list in that they were made using the 1.88m David Dunlap reflector. One of the stars varies in radial velocity, consistent with a spectroscopic binary with a period of about 48 days. (SECTION: Stars)

  8. Vertical Motion Characteristics of Tropical Cyclones Determined with Airborne Doppler Radial Velocities.

    NASA Astrophysics Data System (ADS)

    Black, Micheal L.; Burpee, Robert W.; Marks, Frank D., Jr.

    1996-07-01

    Vertical motions in seven Atlantic hurricanes are determined from data recorded by Doppler radars on research aircraft. The database consists of Doppler velocities and reflectivities from vertically pointing radar rays collected along radial flight legs through the hurricane centers. The vertical motions are estimated throughout the depth of the troposphere from the Doppler velocities and bulk estimates of particle fallspeeds.Portions of the flight tracks are subjectively divided into eyewall, rainband, stratiform, and `other' regions. Characteristics of the vertical velocity and radar structure are described as a function of altitude for the entire dataset and each of the four regions. In all of the regions, more than 70% of the vertical velocities range from 2 to 2 m s1. The broadest distribution of vertical motion is in the eyewall region where 5% of the vertical motions are >5 m s1. Averaged over the entire dataset, the mean vertical velocity is upward at all altitudes. Mean downward motion occurs only in the lower troposphere of the stratiform region. Significant vertical variations in the mean profiles of vertical velocity and reflectivity are discussed and related to microphysical processes.In the lower and middle troposphere, the characteristics of the Doppler-derived vertical motions are similar to those described in an earlier study using flight-level vertical velocities, even though the horizontal resolution of the Doppler data is 750 m compared to 125 m from the in situ flight-level measurements. The Doppler data are available at higher altitudes than those reached by turboprop aircraft and provide information on vertical as well as horizontal variations. In a vertical plane along the radial flight tracks, Doppler up- and downdrafts are defined at each 300-m altitude interval as vertical velocities whose absolute values continuously exceed 1.5 m s1, with at least one speed having an absolute value greater than 3.0 m s1. The properties of the Doppler

  9. Ambient noise tomography of Ecuador: Fore- and back-arc velocity structure and radial anisotropy

    NASA Astrophysics Data System (ADS)

    Lynner, C.; Beck, S. L.; Porritt, R.; Meltzer, A.; Alvarado, A. P.; Gabriela, P.; Ruiz, M. C.; Hoskins, M.; Stachnik, J.; Rietbrock, A.; Leon-Rios, S.; Regnier, M. M.; Agurto-Detzel, H.; Font, Y.; Charvis, P.

    2017-12-01

    In northern South America, the oceanic Nazca plate subducts beneath the South American continent, giving rise to the high mountains of the northern Andes. The Ecuador subduction zone has a history of large megathrust earthquakes, most recently the Mw=7.8 April 16, 2016, Pedernales earthquake. The volcanic arc in Ecuador is broad with active volcanoes along both the western and eastern cordilleras. Many of these volcanoes surround the city of Quito putting millions of people at risk. A recent international broadband aftershock deployment was conducted for approximately one year after the Pedernales mainshock and this data combined with a sub-set of data from from the permanent IGEPN national network provide an ideal data set to use for ambient noise tomography (ANT) to constrain absolute Vsh and Vsv across Ecuador. ANT studies use noise-generated surface wave dispersion measurements to invert for 3D shear velocity in the crust. Having a precise understanding of crustal velocity structure is necessary to advance a number of projects, including better earthquake locations of the April 16, 2016 Pedernales-earthquake aftershock sequence and identifying large-scale partial melt zones associated with the active volcanic arc. The majority of ANT studies use only Rayleigh waves to constrain Vsv structure. Initial Rayleigh wave ANT results, using periods between 8 and 40 seconds, show a fast phase velocities for the forearc and much slower phase velocities for the high elevation volcanic arc. Including Love wave dispersion measurements can improve overall crustal velocity models, as well as provide constraints on radial anisotropy. Radial anisotropy can develop in a variety of ways but most typically arises from the deformation-induced alignment of anisotropic minerals. Radial anisotropy, therefore, can inform on patterns of ductile crustal flow. Strong radial anisotropy at mid-crustal depths from ANT has already been observed south of Ecuador, in the Central Andean Plateau

  10. Errors in radial velocity variance from Doppler wind lidar

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

    Wang, H.; Barthelmie, R. J.; Doubrawa, P.

    A high-fidelity lidar turbulence measurement technique relies on accurate estimates of radial velocity variance that are subject to both systematic and random errors determined by the autocorrelation function of radial velocity, the sampling rate, and the sampling duration. Our paper quantifies the effect of the volumetric averaging in lidar radial velocity measurements on the autocorrelation function and the dependence of the systematic and random errors on the sampling duration, using both statistically simulated and observed data. For current-generation scanning lidars and sampling durations of about 30 min and longer, during which the stationarity assumption is valid for atmospheric flows, themore » systematic error is negligible but the random error exceeds about 10%.« less

  11. Errors in radial velocity variance from Doppler wind lidar

    DOE PAGES

    Wang, H.; Barthelmie, R. J.; Doubrawa, P.; ...

    2016-08-29

    A high-fidelity lidar turbulence measurement technique relies on accurate estimates of radial velocity variance that are subject to both systematic and random errors determined by the autocorrelation function of radial velocity, the sampling rate, and the sampling duration. Our paper quantifies the effect of the volumetric averaging in lidar radial velocity measurements on the autocorrelation function and the dependence of the systematic and random errors on the sampling duration, using both statistically simulated and observed data. For current-generation scanning lidars and sampling durations of about 30 min and longer, during which the stationarity assumption is valid for atmospheric flows, themore » systematic error is negligible but the random error exceeds about 10%.« less

  12. GJ 3236 - radial velocity determination

    NASA Astrophysics Data System (ADS)

    Kára, J.; Wolf, M.; Zharikov, S.

    2018-04-01

    We present a new study of low-mass red-dwarf eclipsing binary GJ 3236 using spectroscopic data obtained by the 2.12-m telescope at the San Pedro Mártir Observatory. We resolved radial velocities of both components of the binary and improved determination of the physical parameters of the binary.

  13. Crust and Mantle Deformation Revealed from High-Resolution Radially Anisotropic Velocity Models

    NASA Astrophysics Data System (ADS)

    Li, A.; Dave, R.; Yao, Y.

    2017-12-01

    Love wave tomography, which can achieve a similar model resolution as Rayleigh wave, so far has limited applications to the USArray data. Recently, we have developed high-resolution Love wave phase velocity maps in the Wyoming craton and Texas using data at the Transportable Array stations. 3-D, radially anisotropic velocity models are obtained by jointly inverting Love and Rayleigh wave phase velocities. A high-velocity anomaly extending to about 200 km depth beneath central Wyoming correlates with negative radial anisotropy (Vsv>Vsh), suggesting that mantle downwelling develops under the cratonic lithosphere. Surprisingly, the significantly low velocity beneath the Yellowstone hotspot, which has been interpreted as partial melting and asthenospheric upwelling, is associated with the largest radial anisotropy (Vsh>Vsv) in the area. This observation does not support mantle upwelling. Instead, it indicates that the upper mantle beneath the hotspot has experienced strong shear deformation probably by the plate motion and large-scale mantle flow. In Texas, positive radial anisotropy in the lower crust extends from the coast to the Ouachita belt, which is characterized by high velocity and negative radial anisotropy. In the upper mantle, large variations of velocity and anisotropy exit under the coastal plain. A common feature in these anisotropic models is that high-velocity anomalies in the upper mantle often correlate with negative anisotropy (Vsv>Vsh) while low-velocity anomalies are associated with positive anisotropy (Vsh>Vsv). The manifestation of mantle downweling as negative radial anisotropy is largely due to the relatively high viscosity of the high-velocity mantle block, which is less affected by the surrounding large-scale horizontal flow. However, mantle upwelling, which is often associated with low-velocity anomalies, presumably low-viscosity mantle blocks, is invisible in radial anisotropy models. Such upwelling may happen too quickly to make last

  14. Search for companions in visual binary systems using precise radial-velocity measurements

    NASA Astrophysics Data System (ADS)

    Katoh, Noriyuki; Itoh, Yoichi; Sato, Bun'ei

    2018-05-01

    The frequency of triple and quadruple systems is considered to be high in the early phase of star formation. Some multiple systems decay in the pre-main-sequence phase. The multiplicity of main-sequence stars provides clues about the evolution of binary systems. This work searched for companions of five components of visual binary systems using precise radial-velocity measurements. Their radial velocities were monitored from 2007 to 2012 using the HIgh Dispersion Echelle Spectrograph (HIDES) installed on the Okayama Astrophysical Observatory (OAO) 1.88 m reflector. In combination with previous work, this work searched for companions with an orbital period of less than 9 yr for the five bodies. We found periodic variations in the radial velocities for ADS 6190 A and BDS 10966A. The radial velocities of ADS 7311 A, 31 Dra A, and 31 Dra B show significant trends. ADS 6190 A is an SB1 binary with an orbital period of 366.2 d. The minimum mass of the secondary star is 0.5^{+0.7}_{-0.2} M_{⊙}. The radial velocity of ADS 7311 A was monitored for an observational span of 3200 d. We rejected a planetary-mass companion as the cause of a decreasing trend in the radial velocity of ADS 7311 A. This work confirmed that the periodic variation in the radial velocity of BDS 10966 A is 771.1 d. Bisector analysis did not reveal a correlation between the asymmetry of a spectral line and the radial velocity of BDS 10966 A. We rejected nonradial oscillation of the photosphere as the source of the radial velocity variation. The variation may be caused by the rotational modulation owing to surface inhomogeneity. The orbital elements of 31 Dra A derived in this paper are consistent with those in a previous paper. 31 Dra A system is an SB1 binary with a minimum mass ratio of 0.30 ± 0.08. 31 Dra B exhibits a periodic variation in radial velocity. The orbital elements derived in this work are consistent with those reported previously by others. The variation is caused by a circumstellar

  15. A radial velocity survey of the Carina Nebula's O-type stars

    NASA Astrophysics Data System (ADS)

    Kiminki, Megan M.; Smith, Nathan

    2018-06-01

    We have obtained multi-epoch observations of 31 O-type stars in the Carina Nebula using the CHIRON spectrograph on the CTIO/SMARTS 1.5-m telescope. We measure their radial velocities to 1-2 km s-1 precision and present new or updated orbital solutions for the binary systems HD 92607, HD 93576, HDE 303312, and HDE 305536. We also compile radial velocities from the literature for 32 additional O-type and evolved massive stars in the region. The combined data set shows a mean heliocentric radial velocity of 0.6 km s-1. We calculate a velocity dispersion of ≤9.1 km s-1, consistent with an unbound, substructured OB association. The Tr 14 cluster shows a marginally significant 5 km s-1 radial velocity offset from its neighbour Tr 16, but there are otherwise no correlations between stellar position and velocity. The O-type stars in Cr 228 and the South Pillars region have a lower velocity dispersion than the region as a whole, supporting a model of distributed massive star formation rather than migration from the central clusters. We compare our stellar velocities to the Carina Nebula's molecular gas and find that Tr 14 shows a close kinematic association with the Northern Cloud. In contrast, Tr 16 has accelerated the Southern Cloud by 10-15 km s-1, possibly triggering further massive star formation. The expansion of the surrounding H II region is not symmetric about the O-type stars in radial velocity space, indicating that the ionized gas is constrained by denser material on the far side.

  16. Signals embedded in the radial velocity noise. Periodic variations in the τ Ceti velocities

    NASA Astrophysics Data System (ADS)

    Tuomi, M.; Jones, H. R. A.; Jenkins, J. S.; Tinney, C. G.; Butler, R. P.; Vogt, S. S.; Barnes, J. R.; Wittenmyer, R. A.; O'Toole, S.; Horner, J.; Bailey, J.; Carter, B. D.; Wright, D. J.; Salter, G. S.; Pinfield, D.

    2013-03-01

    Context. The abilities of radial velocity exoplanet surveys to detect the lowest-mass extra-solar planets are currently limited by a combination of instrument precision, lack of data, and "jitter". Jitter is a general term for any unknown features in the noise, and reflects a lack of detailed knowledge of stellar physics (asteroseismology, starspots, magnetic cycles, granulation, and other stellar surface phenomena), as well as the possible underestimation of instrument noise. Aims: We study an extensive set of radial velocities for the star HD 10700 (τ Ceti) to determine the properties of the jitter arising from stellar surface inhomogeneities, activity, and telescope-instrument systems, and perform a comprehensive search for planetary signals in the radial velocities. Methods: We performed Bayesian comparisons of statistical models describing the radial velocity data to quantify the number of significant signals and the magnitude and properties of the excess noise in the data. We reached our goal by adding artificial signals to the "flat" radial velocity data of HD 10700 and by seeing which one of our statistical noise models receives the greatest posterior probabilities while still being able to extract the artificial signals correctly from the data. We utilised various noise components to assess properties of the noise in the data and analyse the HARPS, AAPS, and HIRES data for HD 10700 to quantify these properties and search for previously unknown low-amplitude Keplerian signals. Results: According to our analyses, moving average components with an exponential decay with a timescale from a few hours to few days, and Gaussian white noise explains the jitter the best for all three data sets. Fitting the corresponding noise parameters results in significant improvements of the statistical models and enables the detection of very weak signals with amplitudes below 1 m s-1 level in our numerical experiments. We detect significant periodicities that have no

  17. Direct Imaging Of Long Period Radial Velocity Targets With NICI

    NASA Astrophysics Data System (ADS)

    Salter, Graeme S.; Tinney, Chris G.; Wittenmyer, Robert A.; Jenkins, James S.; Jones, Hugh R. A.; O'Toole, Simon J.

    2014-01-01

    We are finally entering an era where radial velocity and direct imaging parameter spaces are starting to overlap. Radial velocity measurements provide us with a minimum mass for an orbiting companion (the mass as a function of the inclination of the system). By following up these long period radial velocity detections with direct imaging we can determine whether a trend seen is due to an orbiting planet at low inclination or an orbiting brown dwarf at high inclination. In the event of a non-detection we are still able to put a limit on the maximum mass of the orbiting body. The Anglo-Australian Planet Search is one of the longest baseline radial velocity planet searches in existence, amongst its targets are many that show long period trends in the data. Here we present our direct imaging survey of these objects with our results to date. ADI Observations have been made using NICI (Near Infrared Coronagraphic Imager) on Gemini South and analysed using an in house, LOCI-like, post processing.

  18. Radial Velocity Survey of T Tauri Stars in Taurus-Auriga

    NASA Astrophysics Data System (ADS)

    Crockett, Christopher; Mahmud, N.; Huerta, M.; Prato, L.; Johns-Krull, C.; Hartigan, P.; Jaffe, D.

    2009-01-01

    Is the frequency of giant planet companions to young stars similar to that seen around old stars? Is the "brown dwarf desert" a product of how low-mass companion objects form, or of how they evolve? Some models indicate that both giant planets and brown dwarfs should be common at young ages within 3 AU of a primary star, but migration induced by massive disks drive brown dwarfs into the parent stars, leaving behind proportionally more giant planets. Our radial velocity survey of young stars will provide a census of the young giant planet and brown dwarf population in Taurus-Auriga. In this poster we present our progress in quantifying how spurious radial velocity signatures are caused by stellar activity and in developing models to help distinguish between companion induced and spot induced radial velocity variations. Early results stress the importance of complementary observations in both visible light and NIR. We present our technique to determine radial velocities by fitting telluric features and model stellar features to our observed spectra. Finally, we discuss ongoing observations at McDonald Observatory, KPNO, and the IRTF, and several new exoplanet host candidates.

  19. Radial Velocity Studies of Close Binary Stars. XI.

    NASA Astrophysics Data System (ADS)

    Pribulla, Theodor; Rucinski, Slavek M.; Lu, Wenxian; Mochnacki, Stefan W.; Conidis, George; Blake, R. M.; DeBond, Heide; Thomson, J. R.; Pych, Wojtek; Ogłoza, Waldemar; Siwak, Michal

    2006-08-01

    Radial-velocity measurements and sine-curve fits to orbital radial velocity variations are presented for 10 close binary systems: DU Boo, ET Boo, TX Cnc, V1073 Cyg, HL Dra, AK Her, VW LMi, V566 Oph, TV UMi, and AG Vir. With this contribution, the David Dunlap Observatory program has reached the point of 100 published radial velocity orbits. The radial velocities have been determined using an improved fitting technique that uses rotational profiles to approximate individual peaks in broadening functions. Three systems, ET Boo, VW LMi, and TV UMi, are found to be quadruple, while AG Vir appears to be a spectroscopic triple. ET Boo, a member of a close visual binary with Pvis=113 yr, was previously known to be a multiple system, but we show that the second component is actually a close, noneclipsing binary. The new observations have enabled us to determine the spectroscopic orbits of the companion, noneclipsing pairs in ET Boo and VW LMi. A particularly interesting case is VW LMi, for which the period of the mutual revolution of the two spectroscopic binaries is only 355 days. While most of the studied eclipsing pairs are contact binaries, ET Boo is composed of two double-lined detached binaries, and HL Dra is a single-lined detached or semidetached system. Five systems of this group have been observed spectroscopically before: TX Cnc, V1073 Cyg, AK Her (as a single-lined binary), V566 Oph, and AG Vir, but our new data are of much higher quality than in the previous studies. Based on data obtained at the David Dunlap Observatory, University of Toronto, Canada.

  20. MARVELS Radial Velocity Solutions to Seven Kepler Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Heslar, Michael Francis; Thomas, Neil B.; Ge, Jian; Ma, Bo; Herczeg, Alec; Reyes, Alan; SDSS-III MARVELS Team

    2016-01-01

    Eclipsing binaries serve momentous purposes to improve the basis of understanding aspects of stellar astrophysics, such as the accurate calculation of the physical parameters of stars and the enigmatic mass-radius relationship of M and K dwarfs. We report the investigation results of 7 eclipsing binary candidates, initially identified by the Kepler mission, overlapped with the radial velocity observations from the SDSS-III Multi-Object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS). The RV extractions and spectroscopic solutions of these eclipsing binaries were generated by the University of Florida's 1D data pipeline with a median RV precision of ~60-100 m/s, which was utilized for the DR12 data release. We performed the cross-reference fitting of the MARVELS RV data and the Kepler photometric fluxes obtained from the Kepler Eclipsing Binary Catalog (V2) and modelled the 7 eclipsing binaries in the BinaryMaker3 and PHOEBE programs. This analysis accurately determined the absolute physical and orbital parameters of each binary. Most of the companion stars were determined to have masses of K and M dwarf stars (0.3-0.8 M⊙), and allowed for an investigation into the mass-radius relationship of M and K dwarfs. Among the cases are KIC 9163796, a 122.2 day period "heartbeat star", a recently-discovered class of eccentric binaries known for tidal distortions and pulsations, with a high eccentricity (e~0.75) and KIC 11244501, a 0.29 day period, contact binary with a double-lined spectrum and mass ratio (q~0.45). We also report on the possible reclassification of 2 Kepler eclipsing binary candidates as background eclipsing binaries based on the analysis of the flux measurements, flux ratios of the spectroscopic and photometric solutions, the differences in the FOVs, the image processing of Kepler, and RV and spectral analysis of MARVELS.

  1. Spectrum radial velocity analyser (SERVAL). High-precision radial velocities and two alternative spectral indicators

    NASA Astrophysics Data System (ADS)

    Zechmeister, M.; Reiners, A.; Amado, P. J.; Azzaro, M.; Bauer, F. F.; Béjar, V. J. S.; Caballero, J. A.; Guenther, E. W.; Hagen, H.-J.; Jeffers, S. V.; Kaminski, A.; Kürster, M.; Launhardt, R.; Montes, D.; Morales, J. C.; Quirrenbach, A.; Reffert, S.; Ribas, I.; Seifert, W.; Tal-Or, L.; Wolthoff, V.

    2018-01-01

    Context. The CARMENES survey is a high-precision radial velocity (RV) programme that aims to detect Earth-like planets orbiting low-mass stars. Aims: We develop least-squares fitting algorithms to derive the RVs and additional spectral diagnostics implemented in the SpEctrum Radial Velocity AnaLyser (SERVAL), a publicly available python code. Methods: We measured the RVs using high signal-to-noise templates created by coadding all available spectra of each star. We define the chromatic index as the RV gradient as a function of wavelength with the RVs measured in the echelle orders. Additionally, we computed the differential line width by correlating the fit residuals with the second derivative of the template to track variations in the stellar line width. Results: Using HARPS data, our SERVAL code achieves a RV precision at the level of 1 m/s. Applying the chromatic index to CARMENES data of the active star YZ CMi, we identify apparent RV variations induced by stellar activity. The differential line width is found to be an alternative indicator to the commonly used full width half maximum. Conclusions: We find that at the red optical wavelengths (700-900 nm) obtained by the visual channel of CARMENES, the chromatic index is an excellent tool to investigate stellar active regions and to identify and perhaps even correct for activity-induced RV variations.

  2. VizieR Online Data Catalog: HD20794 HARPS radial velocities (Feng+, 2017)

    NASA Astrophysics Data System (ADS)

    Feng, F.; Tuomi, M.; Jones, H. R. A.

    2017-05-01

    HARPS radial velocities, activity indices and differential radial velocities for HD 20794. The HARPS spectra are available in the European Southern Observatory archive, and are processed using the TERRA algorithm (Anglada-Escude and Butler, 2012, Cat. J/ApJS/200/15). (1 data file).

  3. Radial Velocity Detection of Extra-Solar Planetary Systems

    NASA Technical Reports Server (NTRS)

    Cochran, William D.

    2004-01-01

    This NASA Origins Program grant supported four closely related research programs at The University of Texas at Austin: 1) The McDonald Observatory Planetary Search (MOPS) Program, using the McDonald Observatory 2.7m Harlan Smith telescope and its 2dcoude spectrometer, 2) A high-precision radial-velocity survey of Hyades dwarfs, using the Keck telescope and its HIRES spectrograph, 3) A program at McDonald Observatory to obtain spectra of the parent stars of planetary systems at R = 210,000, and 4) the start of high precision radial velocity surveys using the Hobby-Eberly Telescope. The most important results from NASA support of these research programs are described. A list of all papers published under support of this grant is included at the end.

  4. Radial and latitudinal gradients in the solar internal angular velocity

    NASA Technical Reports Server (NTRS)

    Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain G.; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

    1988-01-01

    The frequency splittings of intermediate-degree (3 to 170 deg) p-mode oscillations obtained from a 16-day subset of observations were analyzed. Results show evidence for both radial and latitudinal gradients in the solar internal angular velocity. From 0.6 to 0.95 solar radii, the solar internal angular velocity increases systematically from 440 to 463 nHz, corresponding to a positive radial gradient of 66 nHz/solar radius for that portion of the solar interior. Analysis also indicates that the latitudinal differential rotation gradient which is seen at the solar surface persists throughout the convection zone, although there are indications that the differential rotation might disappear entirely below the base of the convection zone. The analysis was extended to include comparisons with additional observational studies and between earlier results and the results of additional inversions of several of the observational datasets. All the comparisons reinforce conclusions regarding the existence of radial and latitudinal gradients in the internal angular velocity.

  5. THE BULGE RADIAL VELOCITY ASSAY (BRAVA). II. COMPLETE SAMPLE AND DATA RELEASE

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

    Kunder, Andrea; De Propris, Roberto; Stubbs, Scott A.

    2012-03-15

    We present new radial velocity measurements from the Bulge Radial Velocity Assay, a large-scale spectroscopic survey of M-type giants in the Galactic bulge/bar region. The sample of {approx}4500 new radial velocities, mostly in the region -10 Degree-Sign < l < +10 Degree-Sign and b Almost-Equal-To -6 Degree-Sign , more than doubles the existent published data set. Our new data extend our rotation curve and velocity dispersion profile to +20 Degree-Sign , which is {approx}2.8 kpc from the Galactic center. The new data confirm the cylindrical rotation observed at -6 Degree-Sign and -8 Degree-Sign and are an excellent fit to themore » Shen et al. N-body bar model. We measure the strength of the TiO{epsilon} molecular band as a first step toward a metallicity ranking of the stellar sample, from which we confirm the presence of a vertical abundance gradient. Our survey finds no strong evidence of previously unknown kinematic streams. We also publish our complete catalog of radial velocities, photometry, TiO band strengths, and spectra, which is available at the Infrared Science Archive as well as at UCLA.« less

  6. Radial Velocity Detection of Extra-Solar Planetary Systems

    NASA Technical Reports Server (NTRS)

    Cochran, William D.

    2004-01-01

    This NASA Origins Program grant supported four closely related research programs at The University of Texas at Austin: 1) The McDonald Observatory Planetary Search (MOPS) Program, using the McDonald Observatory 2.7m Harlan Smith telescope and its 2dcoud6 spectrometer, 2) A high-precision radial-velocity survey of Hyades dwarfs, using the Keck telescope and its HIRES spectrograph, 3) A program at McDonald Observatory to obtain spectra of the parent stars of planetary systems at R = 210,000, and 4) the start of high precision radial velocity surveys using the Hobby-Eberly Telescope. The most important results from NASA support of these research programs are described below. A list of all papers published under support of this grant is included at the end.

  7. Radial velocities of K-M dwarfs and local stellar kinematics

    NASA Astrophysics Data System (ADS)

    Sperauskas, J.; Bartašiūtė, S.; Boyle, R. P.; Deveikis, V.; Raudeliūnas, S.; Upgren, A. R.

    2016-12-01

    Aims: The goal of this paper is to present complete radial-velocity data for the spectroscopically selected McCormick sample of nearby K-M dwarfs and, based on these and supplementary data, to determine the space-velocity distributions of late-type stars in the solar neighborhood. Methods: We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. Combining radial-velocity data with Hipparcos/Tycho-2 astrometry we calculated the space-velocity components and parameters of the galactic orbits in a three-component model potential for the stars in the sample, that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. Results: We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability, along with the catalog of U,V,W velocities and Galactic orbital parameters for a total of 1088 K-M stars which are used in the present kinematic analysis. Of these, 146 stars were identified as possible candidate members of the known nearby kinematic groups and suspected subgroups. The distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction ( 3%) of stars with the thick disk kinematics. The kinematic structure gives evidence that the bulk of K-M type stars in the immediate solar vicinity represents a dynamically relaxed stellar population. The star MCC 869 is found to be on a retrograde Galactic orbit (V = -262 km s-1) of low inclination (4°) and can be a member of stellar stream of some dissolved structure. The Sun's velocity with respect to the Local

  8. A systematic approach to determining the properties of an iodine absorption cell for high-precision radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Perdelwitz, V.; Huke, P.

    2018-06-01

    Absorption cells filled with diatomic iodine are frequently employed as wavelength reference for high-precision stellar radial velocity determination due their long-term stability and low cost. Despite their wide-spread usage in the community, there is little documentation on how to determine the ideal operating temperature of an individual cell. We have developed a new approach to measuring the effective molecular temperature inside a gas absorption cell and searching for effects detrimental to a high precision wavelength reference, utilizing the Boltzmann distribution of relative line depths within absorption bands of single vibrational transitions. With a high resolution Fourier transform spectrometer, we took a series of 632 spectra at temperatures between 23 °C and 66 °C. These spectra provide a sufficient basis to test the algorithm and demonstrate the stability and repeatability of the temperature determination via molecular lines on a single iodine absorption cell. The achievable radial velocity precision σRV is found to be independent of the cell temperature and a detailed analysis shows a wavelength dependency, which originates in the resolving power of the spectrometer in use and the signal-to-noise ratio. Two effects were found to cause apparent absolute shifts in radial velocity, a temperature-induced shift of the order of ˜1 ms-1K-1 and a more significant effect resulting in abrupt jumps of ≥50 ms-1 is determined to be caused by the temperature crossing the dew point of the molecular iodine.

  9. EXOFIT: orbital parameters of extrasolar planets from radial velocities

    NASA Astrophysics Data System (ADS)

    Balan, Sreekumar T.; Lahav, Ofer

    2009-04-01

    Retrieval of orbital parameters of extrasolar planets poses considerable statistical challenges. Due to sparse sampling, measurement errors, parameters degeneracy and modelling limitations, there are no unique values of basic parameters, such as period and eccentricity. Here, we estimate the orbital parameters from radial velocity data in a Bayesian framework by utilizing Markov Chain Monte Carlo (MCMC) simulations with the Metropolis-Hastings algorithm. We follow a methodology recently proposed by Gregory and Ford. Our implementation of MCMC is based on the object-oriented approach outlined by Graves. We make our resulting code, EXOFIT, publicly available with this paper. It can search for either one or two planets as illustrated on mock data. As an example we re-analysed the orbital solution of companions to HD 187085 and HD 159868 from the published radial velocity data. We confirm the degeneracy reported for orbital parameters of the companion to HD 187085, and show that a low-eccentricity orbit is more probable for this planet. For HD 159868, we obtained slightly different orbital solution and a relatively high `noise' factor indicating the presence of an unaccounted signal in the radial velocity data. EXOFIT is designed in such a way that it can be extended for a variety of probability models, including different Bayesian priors.

  10. The effect of non-zero radial velocity on the impulse and circulation of starting jets

    NASA Astrophysics Data System (ADS)

    Krieg, Michael; Mohseni, Kamran

    2011-11-01

    Vortex ring formation dynamics are generally studied using two basic types of vortex generators. Piston cylinder vortex generators eject fluid through a long tube which ensures a purely axial jet; whereas, vortex ring generators which expel fluid through a flat plate with a circular orifice produce 2-D jets (non-zero radial velocity). At the nozzle exit plane of the orifice type vortex generator the radial component of velocity is linearly proportional to the radial distance from the axis of symmetry, reaching a maximum at the edge of the orifice with a magnitude around 10 % of the piston velocity (the ratio of the volume flux and the nozzle area). As the jet advances downstream the radial velocity quickly dissipates, and becomes purely axial less than a diameter away from the nozzle exit plane. The radial velocity gradient in the axial direction plays a key role in the rate at which circulation and impulse are ejected from the vortex generator. Though the radial component of velocity is small compared to the axial velocity, it has a significant effect on both the circulation and impulse of the starting jet because of this gradient. The extent of circulation and impulse enhancement is investigated through experimental DPIV data showing that the orifice device produces nearly double both circulation and energy (with identical piston velocity and stroke ratios).

  11. VizieR Online Data Catalog: Radial velocities of K-M dwarfs (Sperauskas+, 2016)

    NASA Astrophysics Data System (ADS)

    Sperauskas, J.; Bartasiute, S.; Boyle, R. P.; Deveikis, V.; Raudeliunas, S.; Upgren, A. R.

    2016-09-01

    We analyzed nearly 3300 measurements of radial velocities for 1049 K-M dwarfs, that we obtained during the past decade with a CORAVEL-type instrument, with a primary emphasis on detecting and eliminating from kinematic calculations the spectroscopic binaries and binary candidates. We present the catalog of our observations of radial velocities for 959 stars which are not suspected of velocity variability. Of these, 776 stars are from the MCC sample and 173 stars are K-M dwarfs from the CNS4. The catalog consists of two parts: Table 2 lists the mean radial velocities, and Table 2a contains individual measurements. Our radial velocities agree with the best published standard stars to within 0.7km/s in precision. Combining these and supplementary radial-velocity data with Hipparcos/Tycho-2 astrometry (Table 4 summarizes input observational data) we calculated the space velocity components and parameters of the galactic orbits in a three-component model potential by Johnston K.V. et al. (1995ApJ...451..598J) for a total of 1088 K-M dwarfs (Table 5), that we use for kinematical analysis and for the identification of possible candidate members of nearby stellar kinematic groups. We identified 146 stars as possible candidate members of the classical moving groups and known or suspected subgroups (Table 7). We show that the distributions of space-velocity components, orbital eccentricities, and maximum distances from the Galactic plane for nearby K-M dwarfs are consistent with the presence of young, intermediate-age and old populations of the thin disk and a small fraction (3%) of stars with the thick disk kinematics. (7 data files).

  12. Absolute Plate Velocities from Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Zheng, Lin; Gordon, Richard

    2015-04-01

    The orientation of seismic anisotropy inferred beneath plate interiors may provide a means to estimate the motions of the plate relative to the sub-asthenospheric mantle. Here we analyze two global sets of shear-wave splitting data, that of Kreemer [2009] and an updated and expanded data set, to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. We also explore the effect of using geologically current plate velocities (i.e., the MORVEL set of angular velocities [DeMets et al. 2010]) compared with geodetically current plate velocities (i.e., the GSRM v1.2 angular velocities [Kreemer et al. 2014]). We demonstrate that the errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. The SKS-MORVEL absolute plate angular velocities (based on the Kreemer [2009] data set) are determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11° Ma-1 (95% confidence limits) right-handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2° ) differs insignificantly from that for continental lithosphere (σ=21.6° ). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4° ) than for continental

  13. Radial-Velocity Signatures of Magnetic Features on the Sun Observed as a Star

    NASA Astrophysics Data System (ADS)

    Palumbo, M. L., III; Haywood, R. D.; Saar, S. H.; Dupree, A. K.; Milbourne, T. W.

    2017-12-01

    In recent years, the search for Earth-mass planets using radial-velocity measurements has become increasingly limited by signals arising from stellar activity. Individual magnetic features induce localized changes in intensity and velocity, which combine to change the apparent radial velocity of the star. Therefore it is critical to identify an indicator of activity-driven radial-velocity variations on the timescale of stellar rotation periods. We use 617.3 nm photospheric filtergrams, magnetograms, and dopplergrams from SDO/HMI and 170.0 nm chromospheric filtergrams from AIA to identify magnetically-driven solar features and reconstruct the integrated solar radial velocity with six samples per day over the course of 2014. Breaking the solar image up into regions of umbrae, penumbrae, quiet Sun, network, and plages, we find a distinct variation in the center-to-limb intensity-weighted velocity for each region. In agreement with past studies, we find that the suppression of convective blueshift is dominated by plages and network, rather than dark photospheric features. In the future, this work will be highly useful for identifying indicators which correlate with rotationally modulated radial-velocity variations. This will allow us to break the activity barrier that currently precludes the precise characterization of exoplanet properties at the lowest masses. This work was supported by the NSF-REU solar physics program at SAO, grant number AGS-1560313. This work was performed in part under contract with the California Institute of Technology (Caltech)/Jet Propulsion Laboratory (JPL) funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

  14. Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity

    NASA Astrophysics Data System (ADS)

    Hatzes, A. P.; Cochran, W. D.; Endl, M.; Guenther, E. W.; MacQueen, P.; Hartmann, M.; Zechmeister, M.; Han, I.; Lee, B.-C.; Walker, G. A. H.; Yang, S.; Larson, A. M.; Kim, K.-M.; Mkrtichian, , D. E.; Döllinger, M.; Simon, , A. E.; Girardi, L.

    2015-08-01

    Aims: We investigate the nature of the long-period radial velocity variations in α Tau first reported over 20 yr ago. Methods: We analyzed precise stellar radial velocity measurements for α Tau spanning over 30 yr. An examination of the Hα and Ca II λ8662 spectral lines, and Hipparcos photometry was also done to help discern the nature of the long-period radial velocity variations. Results: Our radial velocity data show that the long-period, low amplitude radial velocity variations are long-lived and coherent. Furthermore, Hα equivalent width measurements and Hipparcos photometry show no significant variations with this period. Another investigation of this star established that there was no variability in the spectral line shapes with the radial velocity period. An orbital solution results in a period of P = 628.96 ± 0.90 d, eccentricity, e = 0.10 ± 0.05, and a radial velocity amplitude, K = 142.1 ± 7.2 m s-1. Evolutionary tracks yield a stellar mass of 1.13 ± 0.11 M⊙, which corresponds to a minimum companion mass of 6.47 ± 0.53 MJup with an orbital semi-major axis of a = 1.46 ± 0.27 AU. After removing the orbital motion of the companion, an additional period of ≈520 d is found in the radial velocity data, but only in some time spans. A similar period is found in the variations in the equivalent width of Hα and Ca II. Variations at one-third of this period are also found in the spectral line bisector measurements. The ~520 d period is interpreted as the rotation modulation by stellar surface structure. Its presence, however, may not be long-lived, and it only appears in epochs of the radial velocity data separated by ~10 yr. This might be due to an activity cycle. Conclusions: The data presented here provide further evidence of a planetary companion to α Tau, as well as activity-related radial velocity variations. Based in part on observations obtained at the 2-m-Alfred Jensch Telescope at the Thüringer Landessternwarte Tautenburg and the

  15. Radial Velocity Detection of Extra-Solar Planetary Systems

    NASA Technical Reports Server (NTRS)

    Cochran, William D.

    1998-01-01

    The McDonald Observatory Planetary Search (MOPS) was designed to search for Jovian-mass planets in orbit around solar-type stars by making high-precision measurements of the Radial Velocity (RV) of a star, to attempt to detect the reflex orbital motion of the star around the star-planet barycenter. In our solar system, the velocity of the Sun around the Sun-Jupiter barycenter averages 12.3 m/ s. The MOPS survey started operation in September 1987, and searches 36 bright, nearby, solar-type dwarfs to 10 m/s precision. The survey was started using telluric O2 absorption lines as the velocity reference metric. Observations use the McDonald Observatory 2.7-m Harlan Smith Telescope coude spectrograph with the six-foot camera. This spectrograph configuration isolates a single order of the echelle grating on a Texas Instruments 800 x 800 CCD. The telluric line method gave us a routine radial velocity precision of about 15 m/s for stars down to about 5-th magnitude. However, the data obtained with this technique suffered from some source of long-term systematic errors, which was probably the intrinsic velocity variability of the terrestrial atmosphere, i.e. winds. In order to eliminate this systematic error and to improve our overall measurement precision, we installed a stabilized I2 gas absorption cell as the velocity metric for the MOPS in October 1990. In use at the telescope, the cell is placed directly in front of the spectrograph entrance slit, with starlight passing through the cell. The use of this sealed stabilized I2 cell removes potential problems with possible long-term drifts in the velocity metric. The survey now includes a sample of 36 nearby F, G, and K type stars of luminosity class V or IV-V.

  16. Stellar Radial Velocities with IGRINS at McDonald Observatory

    NASA Astrophysics Data System (ADS)

    Mace, Gregory; Jaffe, Daniel; Park, Chan; Lee, Jae-Joon

    2016-06-01

    Exoplanet searches with dedicated instrumentation have made 1 m/s radial velocity (RV) precision routine.Yet, RVs for large samples of stars generally remain at the 1km/s level.TheImmersion Grating Infrared Spectrometer (IGRINS) is a revolutionary instrument that exploits broad spectral coverage at high-resolution in the near-infrared.IGRINS on the 2.7 meter Harlan J. Smith Telescope at McDonald Observatory is nearly as sensitive as CRIRES at the 8 meter Very Large Telescope. However, IGRINS at R=45,000 has more than 30 times the spectral grasp of CRIRES.The use of a silicon immersion grating facilitates a compact cryostat while providing simultaneous wavelength coverage from 1.45 - 2.45 microns. Wehave developed a pipeline to cross-correlate the more than 20,000 resolution elements in two IGRINS exposures and provide relative RVs with uncertainties of 50m/s (<1% of a resolution element). Absolute RVs are limited by thezero point uncertainty, which is 150m/s.IGRINS RVs will be provided for thousands of objects per year as a default procedure of the data reduction pipeline, creating a legacy product for multi-epoch studies of low-mass, stellar and substellar multiplicity.

  17. Wide-field absolute transverse blood flow velocity mapping in vessel centerline

    NASA Astrophysics Data System (ADS)

    Wu, Nanshou; Wang, Lei; Zhu, Bifeng; Guan, Caizhong; Wang, Mingyi; Han, Dingan; Tan, Haishu; Zeng, Yaguang

    2018-02-01

    We propose a wide-field absolute transverse blood flow velocity measurement method in vessel centerline based on absorption intensity fluctuation modulation effect. The difference between the light absorption capacities of red blood cells and background tissue under low-coherence illumination is utilized to realize the instantaneous and average wide-field optical angiography images. The absolute fuzzy connection algorithm is used for vessel centerline extraction from the average wide-field optical angiography. The absolute transverse velocity in the vessel centerline is then measured by a cross-correlation analysis according to instantaneous modulation depth signal. The proposed method promises to contribute to the treatment of diseases, such as those related to anemia or thrombosis.

  18. The radial velocity technique and the discovery of exoplanets as seen by high school students.

    NASA Astrophysics Data System (ADS)

    Alves, Mauro; Gusev, Anatoly; Pugacheva, Galina; Martin, Inacio; Lyra, Cassia

    2012-07-01

    Presently, the existence of more than 750 exoplanets has been confirmed. The radial velocity technique has proven to be the most effective means to detect planets orbiting other stars. In this technique, which is based on the Doppler effect, the observation of the displacement of spectral lines is used to infer the presence of exoplanets orbiting distant stars. Despite the apparent complexity of this technique, high-school students not only can understand its basic principles, but also create simple programs and software to represent and simulate changes in the radial velocity of a star. Thus, as an extracurricular activity, high-school students developed a simple computer program using the C programming language to simulate the influence of a planet orbiting a star in order to obtain radial velocity curves. The radial velocity curve depends on the masses of the star and planet, and orbital parameters such as orbital period, semi-major axis, eccentricity, inclination, argument of periapsis, longitude of the ascending node and mean anomaly. The software allows the variation of these parameters so that the influence of any planet (or system of planets) in orbit of a star can be simulated and the corresponding changes in the radial velocity be observed. For comparison purposes, the radial velocity curve of the Sun under the influence of Jupiter and Saturn are compared with the radial velocity curves of other stars with known exoplanets. This activity became a multidisciplinary study of an interesting physical phenomenon. To obtain the desired results, the students had to learn new concepts and use different tools, which was very rewarding to them.

  19. Multifractal structures in radial velocity measurements for exoplanets

    NASA Astrophysics Data System (ADS)

    Del Sordo, Fabio; Sahil Agarwal, Debra A. Fischer, John S. Wettlaufer

    2015-01-01

    The radial velocity method is a powerful way to search for exoplanetary systems and it led to many discoveries of exoplanets in the last 20 years.Nevertheless, in order observe Earth-like planets, such method needs to be refined, i.e. one needs to improve the signal-to-noise ratio.On one hand this can be achieved by building spectrographs with better performances, but on the other hand it is also central to understand the noise present in the data.Radial-velocity data are time-series which contains the effect of planets as well as of stellar disturbances. Therefore, they are the result of different physical processes which operate on different time-scales, acting in a not always periodic fashionI present here a possible approach to such problem, which consists in looking for multifractal structures in the time-series coming from radial velocity measurements, identifying the underlying long-range correlations and fractal scaling properties, and connecting them to the underlying physical processes, like stellar oscillation, granulation, rotation, and magnetic activity.This method has been previously applied to satellite data related to Arctic sea albedo, relevant for identify trends and noise in the Arctic sea ice (Agarwal, Moon and Wettlaufer, Proc. R. Soc., 2012).Here we use such analysis for exoplanetary data related to possible Earth-like planets.Moreover, we apply the same procedure to synthetic data from numerical simulation of stellar dynamos, which give insight on the mechanism responsible for the noise. In such way we can therefore raise the signal-to-noise ratio in the data using the synthetic data as predicted noise to be subtracted from the observations.

  20. The Pulsational Nature of R-Coronae - Light and Radial Velocity Variations during 1990 and 1991

    NASA Astrophysics Data System (ADS)

    Fernie, J. D.; Lawson, W. A.

    1993-12-01

    We report photometry and radial velocities of the R Coronae Borealis (RCB) star R CrB, obtained during 1991. We compare these observations with published photometry obtained during 1990 and velocities obtained during 1990 and 1991, and analyse these data using Fourier techniques. In line with the conclusions of earlier analyses, the pulsational nature of R CrB is difficult to quantify, particularly on timescales of longer than a yea The 1990 data are possibly consistent with the presence of a 43-d radial pulsation mode. During 1991 there was some evidence for a periodicity near this value in the radial velocities, but not in the photometric data. Additional data are desirable to investigate the possible presence of one or more periodicities in the light and radial velocity curves.

  1. A radial velocity survey of the open cluster IC 4665

    NASA Technical Reports Server (NTRS)

    Prosser, Charles F.; Giampapa, Mark S.

    1994-01-01

    A radial velocity survey of the open cluster IC 4665 is reported for a group of candidate members previously identified on the basis of proper motion and photometry. Of those candidates observed, 20 out of 42 have radial velocities consistent with membership; these cluster members populate the F5-K0 dwarf region and represent the first relatively conclusive membership determinations for such solar-type stars in IC 4665. Three new spectroscopic binary members of the cluster have been identified. Rotational velocities have also been derived; the v sin i distribution among IC 4665 members reveals that most apparent G dwarf members of IC 4665 are seen to exhibit substantial rotation (v sin i greater than 10 km/s). When compared to evolutionary isochrones, the current list of intermediate-mass members appears to support earlier suggestions that IC 4665 has an age comparable to the Pleiades.

  2. Absolute calibration of Doppler coherence imaging velocity images

    NASA Astrophysics Data System (ADS)

    Samuell, C. M.; Allen, S. L.; Meyer, W. H.; Howard, J.

    2017-08-01

    A new technique has been developed for absolutely calibrating a Doppler Coherence Imaging Spectroscopy interferometer for measuring plasma ion and neutral velocities. An optical model of the interferometer is used to generate zero-velocity reference images for the plasma spectral line of interest from a calibration source some spectral distance away. Validation of this technique using a tunable diode laser demonstrated an accuracy better than 0.2 km/s over an extrapolation range of 3.5 nm; a two order of magnitude improvement over linear approaches. While a well-characterized and very stable interferometer is required, this technique opens up the possibility of calibrated velocity measurements in difficult viewing geometries and for complex spectral line-shapes.

  3. Binary-corrected velocity dispersions from single- and multi-epoch radial velocities: massive stars in R136 as a test case

    NASA Astrophysics Data System (ADS)

    Cottaar, M.; Hénault-Brunet, V.

    2014-02-01

    Orbital motions from binary stars can broaden the observed line-of-sight velocity distribution of a stellar system and artificially inflate the measured line-of-sight velocity dispersion, which can in turn lead to erroneous conclusions about the dynamical state of the system. Recently, a maximum-likelihood procedure was proposed to recover the intrinsic velocity dispersion of a resolved star cluster from a single epoch of radial velocity data of individual stars, which was achieved by simultaneously fitting the intrinsic velocity distribution of the single stars and the centers of mass of the binaries along with the velocity shifts caused by binary orbital motions. Assuming well-characterized binary properties, this procedure can accurately reproduce intrinsic velocity dispersions below 1 km s-1 for solar-type stars. Here we investigate the systematic offsets induced when the binary properties are uncertain and we show that two epochs of radial velocity data with an appropriate baseline can help to mitigate these systematic effects. We first test the method described above using Monte Carlo simulations, taking into account the large uncertainties in the binary properties of OB stars. We then apply it to radial velocity data in the young massive cluster R136 for which the intrinsic velocity dispersion of O-type stars is known from an intensive multi-epoch approach. For typical velocity dispersions of young massive clusters (≳4 km s-1) and with a single epoch of data, we demonstrate that the method can just about distinguish between a cluster in virial equilibrium and an unbound cluster. This is due to the higher spectroscopic binary fraction and more loosely constrained distributions of orbital parameters of OB stars compared to solar-type stars. By extending the maximum-likelihood method to multi-epoch data, we show that the accuracy on the fitted velocity dispersion can be improved by only a few percent by using only two epochs of radial velocities. This

  4. The Radial Velocity Precision of Fiber-fed Spectrographs

    NASA Astrophysics Data System (ADS)

    Walker, Gordon A. H.; Shkolnik, Evgenya; Bohlender, David A.; Yang, Stephenson

    2003-06-01

    We have measured the radial velocities of five 51 Peg-type stars and one star known to be constant in velocity. Our measurements, on 20 Å centered at 3947 Å, were conventional, using Th/Ar comparison spectra taken every 20 or 40 minutes between the stellar exposures. Existing IRAF routines were used for the reduction. We find σRV<=20 m s-1, provided that four measurements (out of 72) with residuals greater than 5 σRV are neglected. The observations were made on five nights with the CFHT Gecko spectrograph (R~110,000), fiber-fed by the CAFE system; σRV<=10 m s-1 seems possible with additional care. This study was incidental to the main observing program and is certainly not exhaustive, but the small value of σRV implies that the fiber feed/image slicer system on Gecko+CAFE essentially eliminates the long-standing problem of guiding errors in radial velocity measurements. We are not promoting this conventional approach for serious Doppler planet searches (especially with Gecko, which has such a small multiplex gain), but the precision is valuable for observations made in spectral regions remote from telluric lines or captive-gas fiducials. Instrument builders might consider the advantages of the CAFE optics, which incorporate agitation and invert the object and pupil to illuminate the slit and grating, respectively, in future spectrograph designs.

  5. Improved Radial Velocity Precision with a Tunable Laser Calibrator

    NASA Astrophysics Data System (ADS)

    Cramer, Claire; Brown, S.; Dupree, A. K.; Lykke, K. R.; Smith, A.; Szentgyorgyi, A.

    2010-01-01

    We present radial velocities obtained using a novel laser-based wavelength calibration technique. We have built a prototype laser calibrator for the Hectochelle spectrograph at the MMT 6.5 m telescope. The Hectochelle is a high-dispersion, fiber-fed, multi-object spectrograph capable of recording up to 240 spectra simultaneously with a resolving power of 40000. The standard wavelength calibration method makes use of spectra from thorium-argon hollow cathode lamps shining directly onto the fibers. The difference in light path between calibration and science light as well as the uneven distribution of spectral lines are believed to introduce errors of up to several hundred m/s in the wavelength scale. Our tunable laser wavelength calibrator solves these problems. The laser is bright enough for use with a dome screen, allowing the calibration light path to better match the science light path. Further, the laser is tuned in regular steps across a spectral order to generate a calibration spectrum, creating a comb of evenly-spaced lines on the detector. Using the solar spectrum reflected from the atmosphere to record the same spectrum in every fiber, we show that laser wavelength calibration brings radial velocity uncertainties down below 100 m/s. We present these results as well as an application of tunable laser calibration to stellar radial velocities determined with the infrared Ca triplet in globular clusters M15 and NGC 7492. We also suggest how the tunable laser could be useful for other instruments, including single-object, cross-dispersed echelle spectrographs, and adapted for infrared spectroscopy.

  6. Radial velocities of southern visual multiple stars

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

    Tokovinin, Andrei; Pribulla, Theodor; Fischer, Debra, E-mail: atokovinin@ctio.noao.edu, E-mail: pribulla@ta3.sk, E-mail: debra.fischer@gmail.com

    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 tomore » 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.« less

  7. Radial and Azimuthal Velocity Profiles in Gas-Puff Z-Pinches

    NASA Astrophysics Data System (ADS)

    Rocco, Sophia; Engelbrecht, Joseph; Banasek, Jacob; de Grouchy, Philip; Qi, Niansheng; Hammer, David

    2016-10-01

    The dynamics of neon, argon, and krypton (either singly or in combination) gas puff z-pinch plasmas are studied on Cornell's 1MA, 100-200ns rise-time COBRA pulsed power generator. The triple-nozzle gas puff valve, consisting of two annular gas puffs and a central jet, allows radial tailoring of the gas puff mass-density profile and the use of 1, 2 or 3 different gases at different pressures. Interferometry supplies information on sheath thickness and electron density, variously filtered PCDs and silicon diodes measure hard and soft x-ray production, and multi frame visible and extreme UV imaging systems allow tracking of the morphology of the plasma. A 527nm, 10J Thomson scattering diagnostic system is used to determine radial and azimuthal velocities. Implosion velocities of 170km/s (Kr) and 300km/s (Ne/Ar) are observed. We are investigating the correlations between instability growth, plasma density profile, velocity partitioning as a function of radius, and radiation production. Research supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement No. DE-NA0001836.

  8. An Ongoing Program of Radial Velocities of Nearby Stars

    NASA Astrophysics Data System (ADS)

    Sperauskas, J.; Boyle, R. P.; Harlow, J.; Jahreiss, H.; Upgren, A. R.

    2003-12-01

    The lists of stars found by Vyssotsky at the McCormick Observatory and the Fourth Edition of the Catalog of Nearby Stars (CNS4) complement each other. Each was limited in a different way, but together they can be used to evaluate sources of systematic error in either of them. The lists of Vyssotsky comprise almost 900 stars, brighter than a limiting visual magnitude of about 11.5. and thus form a magnitude-limited sample. The CNS4 includes all stars believed to be within 25 parsecs of the Sun, and thus forms a distance-limited group. Limits in magnitude are prone to the Malmquist bias by which stars of a given range in magnitude may average spuriously brighter than stars within a given distance range appropriate for the mean distance modulus. The CNS4 stars may be subject to a slight Lutz-Kelker effect. This also requires a correction that depends mainly on the ratios of the standard errors in the distances to the stars, to the distances, themselves. This is a status report on a survey seeking completeness in the six dynamical properties (positions along the three orthogonal axes, and their first time-derivatives). Parallax, proper motion and radial velocity are the stellar properties required for this information and, as is frequently the case among sets of faint stars, the radial velocities are not always available. We seek to obtain radial velocities for a full dynamical picture for more than one thousand nearby stars of which some two-thirds have been observed. It would be most desirable to follow with age-related measures for all stars

  9. Shear-velocity structure, radial anisotropy and dynamics of the Tibetan crust

    NASA Astrophysics Data System (ADS)

    Agius, Matthew R.; Lebedev, Sergei

    2014-12-01

    Geophysical and geological data suggest that Tibetan middle crust is a partially molten, mechanically weak layer, but it is debated whether this low-viscosity layer is present beneath the entire plateau, what its properties are, how it deforms, and what role it has played in the plateau's evolution. Broad-band seismic surface waves yield resolution in the entire depth range of the Tibetan crust and can be used to constrain its shear-wave velocity structure (indicative of crustal composition, temperature and partial melting) and radial anisotropy (indicative of the patterns of deformation). We measured Love- and Rayleigh-wave phase-velocity curves in broad period ranges (up to 7-200 s) for a few tens of pairs and groups of stations across Tibet, combining, in each case, hundreds of interstation measurements, made with cross-correlation and waveform-inversion methods. Shear-velocity profiles were then determined by extensive series of non-linear inversions of the data, designed to constrain the depth-dependent ranges of isotropic-average shear speeds and radial anisotropy. Shear wave speeds within the Tibetan middle crust are anomalously low and, also, show strong lateral variations across the plateau. The lowest mid-crustal shear speeds are found in the north and west of the plateau (˜3.1-3.2 km s-1), within a pronounced low-velocity zone. In southeastern Tibet, crustal shear wave speeds increase gradually towards southeast, whereas in the north, the change across the Kunlun Fault is relatively sharp. The lateral variations of shear speeds within the crust are indicative of those in temperature. A mid-crustal temperature of 800 °C, reported previously, can account for the low shear velocities across Lhasa. In the north, the temperature is higher and exceeds the solidus, resulting in partial melting that we estimate at 3-6 per cent. Strong radial anisotropy is required by the data in western-central Tibet (>5 per cent) but not in northeastern Tibet. The amplitude

  10. The search for extrasolar planets: Study of line bisectors and its relation with precise radial velocity measurements

    NASA Astrophysics Data System (ADS)

    Martinez Fiorenzano, A. F.

    2006-03-01

    (Abridged) To this purpose, in the course of the thesis work we prepared a suitable software in order to use the same spectra acquired for radial velocity determinations (i.e., with the spectrum of the Iodine cell imprinted on) to measure variations of the stellar line profiles. This is a novel approach, that can be of general utility in all high precision radial velocity surveys based on iodine cell data. This software has then been extensively used on data acquired within our survey, allowing a proper insight into a number of interesting cases, where spurious estimates of the radial velocities due to activity or contamination by light from the companions were revealed. The same technique can also be considered to correct the measured radial velocities, in order to search for planets around active stars.

  11. The radial velocity, velocity dispersion, and mass-to-light ratio of the Sculptor dwarf galaxy

    NASA Technical Reports Server (NTRS)

    Armandroff, T. E.; Da Costa, G. S.

    1986-01-01

    The radial velocity, velocity dispersion, and mass-to-light ratio for 16 K giants in the Sculptor dwarf galaxy are calculated. Spectra at the Ca II triplet are analyzed using cross-correlation techniques in order to obtain the mean velocity of + 107.4 + or - 2.0 km/s. The dimensional velocity dispersion estimated as 6.3 (+1.1, -1.3) km/s is combined with the calculated core radius and observed central surface brightness to produce a mass-to-light ratio of 6.0 in solar units. It is noted that the data indicate that the Sculptor contains a large amount of mass not found in globular clusters, and the mass is either in the form of remnant stars or low-mass dwarfs.

  12. AD Leonis: Radial Velocity Signal of Stellar Rotation or Spin–Orbit Resonance?

    NASA Astrophysics Data System (ADS)

    Tuomi, Mikko; Jones, Hugh R. A.; Barnes, John R.; Anglada-Escudé, Guillem; Butler, R. Paul; Kiraga, Marcin; Vogt, Steven S.

    2018-05-01

    AD Leonis is a nearby magnetically active M dwarf. We find Doppler variability with a period of 2.23 days, as well as photometric signals: (1) a short-period signal, which is similar to the radial velocity signal, albeit with considerable variability; and (2) a long-term activity cycle of 4070 ± 120 days. We examine the short-term photometric signal in the available All-Sky Automated Survey and Microvariability and Oscillations of STars (MOST) photometry and find that the signal is not consistently present and varies considerably as a function of time. This signal undergoes a phase change of roughly 0.8 rad when considering the first and second halves of the MOST data set, which are separated in median time by 3.38 days. In contrast, the Doppler signal is stable in the combined High-Accuracy Radial velocity Planet Searcher and High Resolution Echelle Spectrometer radial velocities for over 4700 days and does not appear to vary in time in amplitude, phase, period, or as a function of extracted wavelength. We consider a variety of starspot scenarios and find it challenging to simultaneously explain the rapidly varying photometric signal and the stable radial velocity signal as being caused by starspots corotating on the stellar surface. This suggests that the origin of the Doppler periodicity might be the gravitational tug of a planet orbiting the star in spin–orbit resonance. For such a scenario and no spin–orbit misalignment, the measured v\\sin i indicates an inclination angle of 15.°5 ± 2.°5 and a planetary companion mass of 0.237 ± 0.047 M Jup.

  13. Using direct numerical simulation to improve experimental measurements of inertial particle radial relative velocities

    NASA Astrophysics Data System (ADS)

    Ireland, Peter J.; Collins, Lance R.

    2012-11-01

    Turbulence-induced collision of inertial particles may contribute to the rapid onset of precipitation in warm cumulus clouds. The particle collision frequency is determined from two parameters: the radial distribution function g (r) and the mean inward radial relative velocity . These quantities have been measured in three dimensions computationally, using direct numerical simulation (DNS), and experimentally, using digital holographic particle image velocimetry (DHPIV). While good quantitative agreement has been attained between computational and experimental measures of g (r) (Salazar et al. 2008), measures of wr have not reached that stage (de Jong et al. 2010). We apply DNS to mimic the experimental image analysis used in the relative velocity measurement. To account for experimental errors, we add noise to the particle positions and `measure' the velocity from these positions. Our DNS shows that the experimental errors are inherent to the DHPIV setup, and so we explore an alternate approach, in which velocities are measured along thin two-dimensional planes using standard PIV. We show that this technique better recovers the correct radial relative velocity PDFs and suggest optimal parameter ranges for the experimental measurements.

  14. Radial Velocities of RR Lyrae Stars in and around NGC 6441

    NASA Astrophysics Data System (ADS)

    Kunder, Andrea; Mills, Arthur; Edgecomb, Joseph; Thomas, Mathew; Schilter, Levi; Boyle, Craig; Parker, Stephen; Bellevue, Gordon; Rich, R. Michael; Koch, Andreas; Johnson, Christian I.; Nataf, David M.

    2018-04-01

    Detailed elemental abundance patterns of metal-poor ([Fe/H] ∼ ‑1 dex) stars in the Galactic bulge indicate that a number of them are consistent with globular cluster (GC) stars and may be former members of dissolved GCs. This would indicate that a few per cent of the Galactic bulge was built up from destruction and/or evaporation of GCs. Here, an attempt is made to identify such presumptive stripped stars originating from the massive, inner Galaxy GC NGC 6441 using its rich RR Lyrae variable star (RRL) population. We present radial velocities of 40 RRLs centered on the GC NGC 6441. All 13 of the RRLs observed within the cluster tidal radius have velocities consistent with cluster membership, with an average radial velocity of 24 ± 5 km s‑1 and a star-to-star scatter of 11 km s‑1. This includes two new RRLs that were previously not associated with the cluster. Eight RRLs with radial velocities consistent with cluster membership but up to three time the distance from the tidal radius are also reported. These potential extra-tidal RRLs also have exceptionally long periods, which is a curious characteristic of the NGC 6441 RRL population that hosts RRLs with periods longer than seen anywhere else in the Milky Way. As expected of stripped cluster stars, most are inline with the cluster’s orbit. Therefore, either the tidal radius of NGC 6441 is underestimated and/or we are seeing dissolving cluster stars stemming from NGC 6441 that are building up the old spheroidal bulge.

  15. VizieR Online Data Catalog: l Car radial velocity curves (Anderson, 2016)

    NASA Astrophysics Data System (ADS)

    Anderson, R. I.

    2018-02-01

    Line-of-sight (radial) velocities of the long-period classical Cepheid l Carinae were measured from 925 high-quality optical spectra recorded using the fiber-fed high-resolution (R~60,000) Coralie spectrograph located at the Euler telescope at La Silla Observatory, Chile. The data were taken between 2014 and 2016. This is the full version of Tab. 2 presented partially in the paper. Line shape parameters (depth, width, asymmetry) are listed for the computed cross-correlation profiles (CCFs). Radial velocities were determined using different techniques (Gaussian, bi-Gaussian) and measured on CCFs computed using three different numerical masks (G2, weak lines, strong lines). (1 data file).

  16. VizieR Online Data Catalog: Cepheid radial velocity amplitude modulations (Anderson, 2014)

    NASA Astrophysics Data System (ADS)

    Anderson, R. I.

    2014-06-01

    A total of 983 radial velocity measurements of the four Cepheids QZ Nor (125), V335 Pup (95), l Car (324), and RS Pup (439) are provided. The measurements are based on observations carried out between April 2011 and February 2014 that were obtained using the Coralie spectrograph, mounted to the Swiss 1.2m Euler telescope located at La Silla Observatory, Chile. For each Cepheid, a table with the barycentric Julian date of observation, radial velocity, and the measurement uncertainty are provided. In addition, a table containing the identifiers, coordinates, and pulsation periods used to phase-fold the data (see the figures in the article) is provided. (5 data files).

  17. A high-precision radial-velocity survey for other planetary systems

    NASA Technical Reports Server (NTRS)

    Cochran, William D.; Hatzes, Artie P.

    1994-01-01

    The precise measurement of variations in stellar radial velocities provides one of several promising methods of surveying a large sample of nearby solar type stars to detect planetary systems in orbit around them. The McDonald Observatory Planetary Search (MOPS) was started in 1987 September with the goal of detecting other nearby planetary systems. A stabilized I2 gas absorption cell placed in front of the entrance slit to the McDonald Observatory 2.7 m telescope coude spectrograph serves as the velocity metric. With this I2 cell we can achieve radial velocity measurement precision better than 10 m/s in an individual measurement. At this level we can detect a Jupiter-like planet around a solar-type star, and have some hope of detecting Saturn-like planets in a long-term survey. The detectability of planets is ultimately limited by stellar pulsation modes and photospheric motions. Monthly MOPS observing runs allow us to obtain at least 5 independent observations per year of the 33 solar-type (F5-K7) stars on our observing list. We present representative results from the first five years of the survey.

  18. Removing Activity-Related Radial Velocity Noise to Improve Extrasolar Planet Searches

    NASA Technical Reports Server (NTRS)

    Saar, Steven; Lindstrom, David M. (Technical Monitor)

    2004-01-01

    We have made significant progress towards the proposal goals of understanding the causes and effects of magnetic activity-induced radial velocity (v_r) jitter and developing methods for correcting it. In the process, we have also made some significant discoveries in the fields of planet-induced stellar activity, planet detection methods, M dwarf convection, starspot properties, and magnetic dynamo cycles. We have obtained super high resolution (R approximately 200,000), high S / N (greater than 300) echelle study of joint line bisector and radial velocity variations using the McDonald 2-D coude. A long observing run in October 2002 in particular was quite successful (8 clear nights). We now have close to three years of data, which begins to sample a good fraction of the magnetic cycle timescales for some of our targets (e.g., kappa Ceti; P_cyc = 5.6 yrs). This will be very helpful in unraveling the complex relationships between plage and radial velocity (v-r) changes which we have uncovered. Preliminary analysis (Saar et al. 2003) of the data in hand, reveals correlations between median line bisector displacement and v_r. The correlation appears to be specific the the particular star being considered, probably since it is a function of both spectral type and rotation rate. Further analysis and interpretation will be in the context of evolving plage models and is in progress.

  19. [The radial velocity measurement accuracy of different spectral type low resolution stellar spectra at different signal-to-noise ratio].

    PubMed

    Wang, Feng-Fei; Luo, A-Li; Zhao, Yong-Heng

    2014-02-01

    The radial velocity of the star is very important for the study of the dynamics structure and chemistry evolution of the Milky Way, is also an useful tool for looking for variable or special objects. In the present work, we focus on calculating the radial velocity of different spectral types of low-resolution stellar spectra by adopting a template matching method, so as to provide effective and reliable reference to the different aspects of scientific research We choose high signal-to-noise ratio (SNR) spectra of different spectral type stellar from the Sloan Digital Sky Survey (SDSS), and add different noise to simulate the stellar spectra with different SNR. Then we obtain theradial velocity measurement accuracy of different spectral type stellar spectra at different SNR by employing a template matching method. Meanwhile, the radial velocity measurement accuracy of white dwarf stars is analyzed as well. We concluded that the accuracy of radial velocity measurements of early-type stars is much higher than late-type ones. For example, the 1-sigma standard error of radial velocity measurements of A-type stars is 5-8 times as large as K-type and M-type stars. We discuss the reason and suggest that the very narrow lines of late-type stars ensure the accuracy of measurement of radial velocities, while the early-type stars with very wide Balmer lines, such as A-type stars, become sensitive to noise and obtain low accuracy of radial velocities. For the spectra of white dwarfs stars, the standard error of radial velocity measurement could be over 50 km x s(-1) because of their extremely wide Balmer lines. The above conclusion will provide a good reference for stellar scientific study.

  20. Two dwarf galaxies in Orion with low radial velocities.

    NASA Astrophysics Data System (ADS)

    Karachentsev, I.; Musella, I.

    1996-11-01

    Two relatively faint (B=15.7 and B=18.4mag, respectively), low velocity (+276 and +322km/s) galaxies were imaged with a CCD in the B, V, I bands. By means of the brightest stars we estimated their distances to be 6.4 and 5.5(+/-2)Mpc, assuming a galactic extinction of 2.7 and 2.9mag, respectively. We note that these isolated irregular dwarfs are located to a high Supergalactic latitude, -63deg, and their low radial velocities may be the result of a retarded expansion along the polar axis of the Local cloud of galaxies.

  1. RadVel: General toolkit for modeling Radial Velocities

    NASA Astrophysics Data System (ADS)

    Fulton, Benjamin J.; Petigura, Erik A.; Blunt, Sarah; Sinukoff, Evan

    2018-01-01

    RadVel models Keplerian orbits in radial velocity (RV) time series. The code is written in Python with a fast Kepler's equation solver written in C. It provides a framework for fitting RVs using maximum a posteriori optimization and computing robust confidence intervals by sampling the posterior probability density via Markov Chain Monte Carlo (MCMC). RadVel can perform Bayesian model comparison and produces publication quality plots and LaTeX tables.

  2. VizieR Online Data Catalog: K2-141 b radial velocity and light curve (Barragan+, 2018)

    NASA Astrophysics Data System (ADS)

    Barragan, O.; Gandolfi, D.; Dai, F.; Livingston, J.; Persson, C. M.; Hirano, T.; Narita, N.; Csizmadia, Sz.; Winn, J. N.; Nespral, D.; Prieto-Arranz, J.; Smith, A. M. S.; Nowak, G.; Albrecht, S.; Antoniciello, G.; Bo Justesen, A.; Cabrera, J.; Cochran, W. D.; Deeg, H..; Eigmuller, P.; Endl, M.; Erikson, A.; Fridlund, M.; Fukui, A.; Grziwa, S.; Guenther, E.; Hatzes, A. P.; Hidalgo, D.; Johnson, M. C.; Korth, J.; Palle, E.; Patzold, M.; Rauer, H.; Tanaka, Y.; van Eylen, V.

    2018-01-01

    Light curve and radial velocities for K2-141 (EPIC 246393474). Light curve comes from campaing 12 of the extended Kepler mission, K2. Radial velocity data was obtained with HARPS at th3 3.6m telescope, ESO. FIES data comes from observations at the Nordic Optical Telescope (NOT). (3 data files).

  3. Volumetric vessel reconstruction method for absolute blood flow velocity measurement in Doppler OCT images

    NASA Astrophysics Data System (ADS)

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

    2017-02-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it not only relates to the properties of the laser and the scattering particles, but also relates to the geometry of both directions of the laser beam and the flow. In this paper, focusing on the analysis of cerebral hemodynamics, we presents a method to quantify the total absolute blood flow velocity in middle cerebral artery (MCA) based on volumetric vessel reconstruction from pure DOCT images. A modified region growing segmentation method is first used to localize the MCA on successive DOCT B-scan images. Vessel skeletonization, followed by an averaging gradient angle calculation method, is then carried out to obtain Doppler angles along the entire MCA. Once the Doppler angles are determined, the absolute blood flow velocity of each position on the MCA is easily found. Given a seed point position on the MCA, our approach could achieve automatic quantification of the fully distributed absolute BFV. Based on experiments conducted using a swept-source optical coherence tomography system, our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches in the rodent brain.

  4. Accelerated radial Fourier-velocity encoding using compressed sensing.

    PubMed

    Hilbert, Fabian; Wech, Tobias; Hahn, Dietbert; Köstler, Herbert

    2014-09-01

    Phase Contrast Magnetic Resonance Imaging (MRI) is a tool for non-invasive determination of flow velocities inside blood vessels. Because Phase Contrast MRI only measures a single mean velocity per voxel, it is only applicable to vessels significantly larger than the voxel size. In contrast, Fourier Velocity Encoding measures the entire velocity distribution inside a voxel, but requires a much longer acquisition time. For accurate diagnosis of stenosis in vessels on the scale of spatial resolution, it is important to know the velocity distribution of a voxel. Our aim was to determine velocity distributions with accelerated Fourier Velocity Encoding in an acquisition time required for a conventional Phase Contrast image. We imaged the femoral artery of healthy volunteers with ECG-triggered, radial CINE acquisition. Data acquisition was accelerated by undersampling, while missing data were reconstructed by Compressed Sensing. Velocity spectra of the vessel were evaluated by high resolution Phase Contrast images and compared to spectra from fully sampled and undersampled Fourier Velocity Encoding. By means of undersampling, it was possible to reduce the scan time for Fourier Velocity Encoding to the duration required for a conventional Phase Contrast image. Acquisition time for a fully sampled data set with 12 different Velocity Encodings was 40 min. By applying a 12.6-fold retrospective undersampling, a data set was generated equal to 3:10 min acquisition time, which is similar to a conventional Phase Contrast measurement. Velocity spectra from fully sampled and undersampled Fourier Velocity Encoded images are in good agreement and show the same maximum velocities as compared to velocity maps from Phase Contrast measurements. Compressed Sensing proved to reliably reconstruct Fourier Velocity Encoded data. Our results indicate that Fourier Velocity Encoding allows an accurate determination of the velocity distribution in vessels in the order of the voxel size. Thus

  5. The Galactic Bulge Radial Velocity/Abundance Assay

    NASA Astrophysics Data System (ADS)

    Rich, R. M.

    2012-08-01

    The Bulge Radial Velocity Assay (BRAVA) measured radial velocities for ˜ 9500 late-type giants in the Galactic bulge, predominantly from -10° < l < +10° and -2° < b < -10°. The project has discovered that the bulge exhibits cylindrical rotation characteristic of bars, and two studies of dynamics (Shen et al. 2010; Wang et al. 2012 MNRAS sub.) find that bar models- either N-body formed from an instability in a preexisting disk, or a self-consistent model- can account for the observed kinematics. Studies of the Plaut field at (l,b) = 0°, -8° show that alpha enhancement is found in bulge giants even 1 kpc from the nucleus. New infrared studies extending to within 0.25° = 35 pc of the Galactic Center find no iron or alpha gradient from Baade's Window (l,b) = 0.9°, -3.9° to our innermost field, in contrast to the marked gradient observed in the outer bulge. We consider the case of the remarkable globular cluster Terzan 5, which has a strongly bimodal iron and rm [α/Fe] within its members, and we consider evidence pro and con that the bulge was assembled from dissolved clusters. The Subaru telescope has the potential to contribute to study of the Galactic bulge, especially using the Hyper Superime-Cam and planned spectroscopic modes, as well as the high resolution spectrograph. The planned Jasmine satellite series may deliver a comprehensive survey of distances and proper motions of bulge stars, and insight into the origin and importance of the X-shaped bulge.

  6. Measurement of the Radial Velocity of Vega and SAO 104807 by high resolution spectrometry

    NASA Astrophysics Data System (ADS)

    Rosas, F.; Ordoñez, J.; Suarez, W.; Quijano, A.

    2017-07-01

    The radial velocity is the component of the velocity with which a celestial object approaches (blueshift) or go away (redshift) of the observer. The precise measurement of the redshift allowed to Humason and Hubble discover the expansion of the Universe. In 1998 two research teams simultaneously discovered that this expansion is accelerated, for that reason the hypothesis of the dark energy has been raised to explain the existing repulsion. The present work shows the measurement of the radial velocity of Vega and SAO104807 by high resolution spectrometry. Using the instruments of the Astronomical Observatory of the University of Nariño, located in the south of Colombia, was measured the displacement that the spectral lines of both celestial objects suffer due to the Doppler effect. The results obtained were quite close to those recorded in databases such as SIMBAD, according to the used equipment. The instruments used were: Celestron CGE Pro 1400 Telescope, Shelyak LHIRES III High Resolution Spectrometer and SBIG ST-8300 CCD Camera. The characteristics of the spectrometer are: Diffraction grating: 2400 lines/mm, Spectral dispersion (H alpha): 0:012 nm/pixel, Radial velocity resolution: 5 km/s.

  7. Stellar Parameters and Radial Velocities of Hot Stars in the Carina Nebula

    NASA Astrophysics Data System (ADS)

    Hanes, Richard J.; McSwain, M. Virginia; Povich, Matthew S.

    2018-05-01

    The Carina Nebula is an active star-forming region in the southern sky that is of particular interest due to the presence of a large number of massive stars in a wide array of evolutionary stages. Here, we present the results of the spectroscopic analysis of 82 B-type stars and 33 O-type stars that were observed in 2013 and 2014. For 82 B-type stars without line blending, we fit model spectra from the Tlusty BSTAR2006 grid to the observed profiles of Hγ and He λλ4026, 4388, and 4471 to measure the effective temperatures, surface gravities, and projected rotational velocities. We also measure the masses, ages, radii, bolometric luminosities, and distances of these stars. From the radial velocities measured in our sample, we find 31 single lined spectroscopic binary candidates. We find a high dispersion of radial velocities among our sample stars, and we argue that the Carina Nebula stellar population has not yet relaxed and become virialized.

  8. Theoretical and Experimental Study of Radial Velocity Generation for Extending Bandwidth of Magnetohydrodynamic Angular Rate Sensor at Low Frequency.

    PubMed

    Ji, Yue; Li, Xingfei; Wu, Tengfei; Chen, Cheng

    2015-12-15

    The magnetohydrodynamics angular rate sensor (MHD ARS) has received much attention for its ultra-low noise in ultra-broad bandwidth and its impact resistance in harsh environments; however, its poor performance at low frequency hinders its work in long time duration. The paper presents a modified MHD ARS combining Coriolis with MHD effect to extend the measurement scope throughout the whole bandwidth, in which an appropriate radial flow velocity should be provided to satisfy simplified model of the modified MHD ARS. A method that can generate radial velocity by an MHD pump in MHD ARS is proposed. A device is designed to study the radial flow velocity generated by the MHD pump. The influence of structure and physical parameters are studied by numerical simulation and experiment of the device. The analytic expression of the velocity generated by the energized current drawn from simulation and experiment are consistent, which demonstrates the effectiveness of the method generating radial velocity. The study can be applied to generate and control radial velocity in modified MHD ARS, which is essential for the two effects combination throughout the whole bandwidth.

  9. Theoretical and Experimental Study of Radial Velocity Generation for Extending Bandwidth of Magnetohydrodynamic Angular Rate Sensor at Low Frequency

    PubMed Central

    Ji, Yue; Li, Xingfei; Wu, Tengfei; Chen, Cheng

    2015-01-01

    The magnetohydrodynamics angular rate sensor (MHD ARS) has received much attention for its ultra-low noise in ultra-broad bandwidth and its impact resistance in harsh environments; however, its poor performance at low frequency hinders its work in long time duration. The paper presents a modified MHD ARS combining Coriolis with MHD effect to extend the measurement scope throughout the whole bandwidth, in which an appropriate radial flow velocity should be provided to satisfy simplified model of the modified MHD ARS. A method that can generate radial velocity by an MHD pump in MHD ARS is proposed. A device is designed to study the radial flow velocity generated by the MHD pump. The influence of structure and physical parameters are studied by numerical simulation and experiment of the device. The analytic expression of the velocity generated by the energized current drawn from simulation and experiment are consistent, which demonstrates the effectiveness of the method generating radial velocity. The study can be applied to generate and control radial velocity in modified MHD ARS, which is essential for the two effects combination throughout the whole bandwidth. PMID:26694393

  10. A catalog of rotational and radial velocities for evolved stars. V. Southern stars

    NASA Astrophysics Data System (ADS)

    De Medeiros, J. R.; Alves, S.; Udry, S.; Andersen, J.; Nordström, B.; Mayor, M.

    2014-01-01

    Rotational and radial velocities have been measured for 1589 evolved stars of spectral types F, G, and K and luminosity classes IV, III, II, and Ib, based on observations carried out with the CORAVEL spectrometers. The precision in radial velocity is better than 0.30 km s-1 per observation, whereas rotational velocity uncertainties are typically 1.0 km s-1 for subgiants and giants and 2.0 km s-1 for class II giants and Ib supergiants. Based on observations collected at the Haute-Provence Observatory, Saint-Michel, France, and at the European Southern Observatory, La Silla, Chile.Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/561/A126

  11. A new method of measuring centre-of-mass velocities of radially pulsating stars from high-resolution spectroscopy

    NASA Astrophysics Data System (ADS)

    Britavskiy, N.; Pancino, E.; Tsymbal, V.; Romano, D.; Fossati, L.

    2018-03-01

    We present a radial velocity analysis of 20 solar neighbourhood RR Lyrae and three Population II Cepheid variables. We obtained high-resolution, moderate-to-high signal-to-noise ratio spectra for most stars; these spectra covered different pulsation phases for each star. To estimate the gamma (centre-of-mass) velocities of the programme stars, we use two independent methods. The first, `classic' method is based on RR Lyrae radial velocity curve templates. The second method is based on the analysis of absorption-line profile asymmetry to determine both pulsational and gamma velocities. This second method is based on the least-squares deconvolution (LSD) technique applied to analyse the line asymmetry that occurs in the spectra. We obtain measurements of the pulsation component of the radial velocity with an accuracy of ±3.5 km s-1. The gamma velocity was determined with an accuracy of ±10 km s-1, even for those stars having a small number of spectra. The main advantage of this method is the possibility of obtaining an estimation of gamma velocity even from one spectroscopic observation with uncertain pulsation phase. A detailed investigation of LSD profile asymmetry shows that the projection factor p varies as a function of the pulsation phase - this is a key parameter, which converts observed spectral line radial velocity variations into photospheric pulsation velocities. As a by-product of our study, we present 41 densely spaced synthetic grids of LSD profile bisectors based on atmospheric models of RR Lyr covering all pulsation phases.

  12. Disentangling Time-series Spectra with Gaussian Processes: Applications to Radial Velocity Analysis

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

    Czekala, Ian; Mandel, Kaisey S.; Andrews, Sean M.

    Measurements of radial velocity variations from the spectroscopic monitoring of stars and their companions are essential for a broad swath of astrophysics; these measurements provide access to the fundamental physical properties that dictate all phases of stellar evolution and facilitate the quantitative study of planetary systems. The conversion of those measurements into both constraints on the orbital architecture and individual component spectra can be a serious challenge, however, especially for extreme flux ratio systems and observations with relatively low sensitivity. Gaussian processes define sampling distributions of flexible, continuous functions that are well-motivated for modeling stellar spectra, enabling proficient searches formore » companion lines in time-series spectra. We introduce a new technique for spectral disentangling, where the posterior distributions of the orbital parameters and intrinsic, rest-frame stellar spectra are explored simultaneously without needing to invoke cross-correlation templates. To demonstrate its potential, this technique is deployed on red-optical time-series spectra of the mid-M-dwarf binary LP661-13. We report orbital parameters with improved precision compared to traditional radial velocity analysis and successfully reconstruct the primary and secondary spectra. We discuss potential applications for other stellar and exoplanet radial velocity techniques and extensions to time-variable spectra. The code used in this analysis is freely available as an open-source Python package.« less

  13. On the Voyager 1 Zero Radial Velocity Measurements in the Inner Heliosheath

    NASA Astrophysics Data System (ADS)

    Pogorelov, N. V.; Borovikov, S. N.; Kryukov, I.; Zank, G. P.

    2011-12-01

    Theoretical analysis of the Voyager 1 data revealed a very small, or even negative, value of the solar wind (SW) radial velocity component. This should not be surprising if we take into account time-dependent processes that take place in the inner heliosheath (IHS). We analyze solar cycle modeling of the SW interaction with the local interstellar medium (LISM) and demonstrate the existence of small and negative values of the SW radial velocity. It shown that, in reality, a similar picture can be observed in the outer heliosheath (OHS), where on the contrary, extended regions of the positive radial velocity are observed. Another scenario discussed in this talk is related to effects of transients, such as global merged interaction regions and corotating interacting regions. Numerical results are obtained with the SW-LISM interaction model developed in the UAHuntsville and implemented in the Multi-Scale Fluid-Kinetic Simulation Suite. This model treats ions magnetohydrodynamically while the transport of neutral atoms is performed kinetically by solving the Boltzmann equation with a Monte Carlo approach or using a multi-fluid approach developed in mid-90's by G. P. Zank. Pickup ions (PUIs) can be treated as a separate fluid. The evolution of the PUI-generated turbulence is addressed on the differential level by adding three additional equations, which are solved self-consistently with the MHD-kinetic system of equations.

  14. Disentangling Time-series Spectra with Gaussian Processes: Applications to Radial Velocity Analysis

    NASA Astrophysics Data System (ADS)

    Czekala, Ian; Mandel, Kaisey S.; Andrews, Sean M.; Dittmann, Jason A.; Ghosh, Sujit K.; Montet, Benjamin T.; Newton, Elisabeth R.

    2017-05-01

    Measurements of radial velocity variations from the spectroscopic monitoring of stars and their companions are essential for a broad swath of astrophysics; these measurements provide access to the fundamental physical properties that dictate all phases of stellar evolution and facilitate the quantitative study of planetary systems. The conversion of those measurements into both constraints on the orbital architecture and individual component spectra can be a serious challenge, however, especially for extreme flux ratio systems and observations with relatively low sensitivity. Gaussian processes define sampling distributions of flexible, continuous functions that are well-motivated for modeling stellar spectra, enabling proficient searches for companion lines in time-series spectra. We introduce a new technique for spectral disentangling, where the posterior distributions of the orbital parameters and intrinsic, rest-frame stellar spectra are explored simultaneously without needing to invoke cross-correlation templates. To demonstrate its potential, this technique is deployed on red-optical time-series spectra of the mid-M-dwarf binary LP661-13. We report orbital parameters with improved precision compared to traditional radial velocity analysis and successfully reconstruct the primary and secondary spectra. We discuss potential applications for other stellar and exoplanet radial velocity techniques and extensions to time-variable spectra. The code used in this analysis is freely available as an open-source Python package.

  15. Absolute measurement of the Hugoniot and sound velocity of liquid copper at multimegabar pressures

    DOE PAGES

    McCoy, Chad August; Knudson, Marcus David; Root, Seth

    2017-11-13

    Measurement of the Hugoniot and sound velocity provides information on the bulk modulus and Grüneisen parameter of a material at extreme conditions. The capability to launch multilayered (copper/aluminum) flyer plates at velocities in excess of 20 km/s with the Sandia Z accelerator has enabled high-precision sound-velocity measurements at previously inaccessible pressures. For these experiments, the sound velocity of the copper flyer must be accurately known in the multi-Mbar regime. Here we describe the development of copper as an absolutely calibrated sound-velocity standard for high-precision measurements at pressures in excess of 400 GPa. Using multilayered flyer plates, we performed absolute measurementsmore » of the Hugoniot and sound velocity of copper for pressures from 500 to 1200 GPa. These measurements enabled the determination of the Grüneisen parameter for dense liquid copper, clearly showing a density dependence above the melt transition. As a result, combined with earlier data at lower pressures, these results constrain the sound velocity as a function of pressure, enabling the use of copper as a Hugoniot and sound-velocity standard for pressures up to 1200 GPa.« less

  16. Absolute measurement of the Hugoniot and sound velocity of liquid copper at multimegabar pressures

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

    McCoy, Chad August; Knudson, Marcus David; Root, Seth

    Measurement of the Hugoniot and sound velocity provides information on the bulk modulus and Grüneisen parameter of a material at extreme conditions. The capability to launch multilayered (copper/aluminum) flyer plates at velocities in excess of 20 km/s with the Sandia Z accelerator has enabled high-precision sound-velocity measurements at previously inaccessible pressures. For these experiments, the sound velocity of the copper flyer must be accurately known in the multi-Mbar regime. Here we describe the development of copper as an absolutely calibrated sound-velocity standard for high-precision measurements at pressures in excess of 400 GPa. Using multilayered flyer plates, we performed absolute measurementsmore » of the Hugoniot and sound velocity of copper for pressures from 500 to 1200 GPa. These measurements enabled the determination of the Grüneisen parameter for dense liquid copper, clearly showing a density dependence above the melt transition. As a result, combined with earlier data at lower pressures, these results constrain the sound velocity as a function of pressure, enabling the use of copper as a Hugoniot and sound-velocity standard for pressures up to 1200 GPa.« less

  17. Celestial-mechanical interpretation of the two-way radio measurements of radial velocity of spacecraft for scientific applications

    NASA Astrophysics Data System (ADS)

    Komovkin, S. V.; Lavrenov, S. M.; Tuchin, A. G.; Tuchin, D. A.; Yaroshevsky, V. S.

    2016-12-01

    The article describes a model of the two-way measurements of radial velocity based on the Doppler effect. The relations are presented for the instantaneous value of the increment range at the time of measurement and the radial velocity of the mid-dimensional interval. The compensation of methodological errors of interpretation of the two-way Doppler measurements is considered.

  18. Estimating vertical velocity and radial flow from Doppler radar observations of tropical cyclones

    NASA Astrophysics Data System (ADS)

    Lee, J. L.; Lee, W. C.; MacDonald, A. E.

    2006-01-01

    The mesoscale vorticity method (MVM) is used in conjunction with the ground-based velocity track display (GBVTD) to derive the inner-core vertical velocity from Doppler radar observations of tropical cyclone (TC) Danny (1997). MVM derives the vertical velocity from vorticity variations in space and in time based on the mesoscale vorticity equation. The use of MVM and GBVTD allows us to derive good correlations among the eye-wall maximum wind, bow-shaped updraught and echo east of the eye-wall in Danny. Furthermore, we demonstrate the dynamically consistent radial flow can be derived from the vertical velocity obtained from MVM using the wind decomposition technique that solves the Poisson equations over a limited-area domain. With the wind decomposition, we combine the rotational wind which is obtained from Doppler radar wind observations and the divergent wind which is inferred dynamically from the rotational wind to form the balanced horizontal wind in TC inner cores, where rotational wind dominates the divergent wind. In this study, we show a realistic horizontal and vertical structure of the vertical velocity and the induced radial flow in Danny's inner core. In the horizontal, the main eye-wall updraught draws in significant surrounding air, converging at the strongest echo where the maximum updraught is located. In the vertical, the main updraught tilts vertically outwards, corresponding very well with the outward-tilting eye-wall. The maximum updraught is located at the inner edge of the eye-wall clouds, while downward motions are found at the outer edge. This study demonstrates that the mesoscale vorticity method can use high-temporal-resolution data observed by Doppler radars to derive realistic vertical velocity and the radial flow of TCs. The vorticity temporal variations crucial to the accuracy of the vorticity method have to be derived from a high-temporal-frequency observing system such as state-of-the-art Doppler radars.

  19. Radial velocities of very low mass stars and candidate brown dwarf members of the Hyades and Pleiades

    NASA Technical Reports Server (NTRS)

    Stauffer, John R.; Liebert, James; Giampapa, Mark; Macintosh, Bruce; Reid, Neill; Hamilton, Donald

    1994-01-01

    We have determined H alpha equivalent widths and radial velocities with 1 sigma accuracies of approximately 5 km s(exp -1) for approximately 20 candidate very low mass members of the Hyades and Pleiades clusters. The radial velocities for the Hyades sample suggest that nearly all of these stars are indeed highly probable members of the Hyades. The faintest stars in the Hyades sample have masses of order 0.1 solar mass. We also obtained radial velocities for four candidate very low mass members of the Pleiades and two objects that are candidate BD Pleiads. All of these stars have apparent V magnitudes fainter than the Hyades stars we observed, and the resultant radial velocity accuracy is worse. We believe that the three brighter stars are indeed likely very low mass stellar members of the Pleiades, whereas the status of the two brown dwarf candidates is uncertain. The Hyades stars we have observed and the three Pleiades very low mass stars are the lowest mass members of any open cluster whose membership has been confirmed by radial velocities and whose chromospheric activity has been measured. We see no change in chromospheric activity at the boundary where stars are expected to become fully convective (M approximately equals 0.3 solar mass) in either cluster. In the Pleiades, however, there may be a decrease in chromospheric activity for stars with (V-I)(sub K) greater than 3.5 (M less than or equal to 0.1 solar mass).

  20. VizieR Online Data Catalog: Radial velocities in M3, M13, and M92 (Kamann+, 2014)

    NASA Astrophysics Data System (ADS)

    Kamann, S.; Wisotzki, L.; Roth, M. M.; Gerssen, J.; Husser, T.-O.; Sandin, C.; Weilbacher, P.

    2014-04-01

    Radial velocity data are presented for three Galactic globular clusters, M3, M13, and M92. The provided catalogues include several hundreds of stars in each cluster that cover a wide range of distances to the cluster centres. Besides the measured radial velocities, the catalogues contain measurement uncertainties, identifiers, world coordinates and variability information for each star. The velocities for stars near the centres of the clusters were obtained using PMAS integral field spectroscopy (IFS). Note that in order to facilitate future variability studies, for each star the individual velocity measurements are provided instead of a single combined velocity. The PMAS data are complemented with velocities reported in various literature studies for stars at larger distances to the centres. (6 data files).

  1. Binaries at Birth: Stellar multiplicity in embedded clusters from radial velocity variations in the IN-SYNC survey

    NASA Astrophysics Data System (ADS)

    Oskar Jaehnig, Karl; Stassun, Keivan; Tan, Jonathan C.; Covey, Kevin R.; Da Rio, Nicola

    2016-01-01

    We study the nature of stellar multiplicity in young stellar systems using the INfrared Spectroscopy of Young Nebulous Clusters (IN-SYNC) survey, carried out in SDSS III with the APOGEE spectrograph. Multi-epoch observations of thousands of low-mass stars in Orion A, NGC2264, NGC1333 and IC348 have been carried out, yielding H-band spectra with R=22,500 for sources with H<12 mag. Radial velocity sensitivities ~0.3 km/s can be achieved, depending on the spectral type of the star. We search the IN-SYNC radial velocity catalog to identify sources with radial velocity variations indicative of spectroscopically undetected companions, analyze their spectral properties and discuss the implications for the overall multiplicity of stellar populations in young, embedded star clusters.

  2. VizieR Online Data Catalog: Radial velocities of 1 Gem (Lane+, 2014)

    NASA Astrophysics Data System (ADS)

    Lane, B. F.; Muterspaugh, M. W.; Griffin, R. F.; Scarfe, C. D.; Fekel, F. C.; Williamson, M. H.; Eaton, J. A.; Shao, M.; Colavita, M. M.; Konacki, M.

    2016-05-01

    Extensive radial-velocity measurements of the 1 Gem system have been obtained in four separate campaigns spanning 40yr, including data from eight different instruments. Between 1969 and 2009 R.F.G. acquired a total of 128 observations of 1 Gem using the original radial-velocity spectrometer at Cambridge; a second-generation, computerized instrument at Palomar; the CORAVEL spectrometer at Haute Provence Observatory (OHP), and most recently, the Cambridge CORAVEL. The "Cambridge CORAVEL" operates at the Coude focus of the 36inch reflector on the home site of the Cambridge Observatories, Madingley Road, Cambridge, England. The Cambridge and Palomar data are referred to as data set A, while the OHP data are labeled set B. The data for components A and Ba are provided in Table1. A series of observations of 1 Gem has been obtained by C.D.S. with the Dominion Astrophysical Observatory (DAO) radial-velocity spectrometer. Observations were begun early in 1980 and continued until the end of 2003. The DAO velocities of components A and Ba are listed in Table2. The total number of acceptable velocities from DAO radial-velocity scanner observations is 123 of the primary star and 107 of the brighter component of the close pair. The third component was not detectable in the DAO traces. We identify the DAO observations as data set C. >From 1983 through 2009 F.C.F. obtained observations at the Kitt Peak National Observatory (KPNO) with the 0.9m coude feed telescope, coude spectrograph, and several different CCD detectors. All of the spectrograms were acquired with a Texas Instruments (TI) CCD except for five that were obtained in 1983 with an RCA CCD and a single observation in 2008 September with a Tektronix CCD. All those observations were centered near 6430Å and had typical signal-to-noise ratios of about 250. The numerous TI CCD spectra have a wavelength range of just 84Å and a resolution of 0.21Å. The 86 velocities of component A and 80 of component Ba are listed in Table3

  3. Astrometry, radial velocity, and photometry: the HD 128311 system remixed with data from HST, HET, and APT

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

    McArthur, Barbara E.; Benedict, G. Fritz.; Cochran, William D.

    We have used high-cadence radial velocity measurements from the Hobby-Eberly Telescope with published velocities from the Lick 3 m Shane Telescope, combined with astrometric data from the Hubble Space Telescope (HST) Fine Guidance Sensors to refine the orbital parameters of the HD 128311 system, and determine an inclination of 55.°95 ± 14.°55 and true mass of 3.789 {sub −0.432}{sup +0.924} M {sub JUP} for HD 128311 c. The combined radial velocity data also reveal a short period signal which could indicate a third planet in the system with an Msin i of 0.133 ± 0.005 M {sub JUP} or stellarmore » phenomena. Photometry from the T12 0.8 m automatic photometric telescope at the Fairborn Observatory and HST are used to determine a photometric period close to, but not within the errors of the radial velocity signal. We performed a cross-correlation bisector analysis of the radial velocity data to look for correlations with the photometric period and found none. Dynamical integrations of the proposed system show long-term stability with the new orbital parameters of over 10 million years. Our new orbital elements do not support the claims of HD 128311 b and c being in mean motion resonance.« less

  4. A radial velocity study of CTCV J1300-3052

    NASA Astrophysics Data System (ADS)

    Savoury, C. D. J.; Littlefair, S. P.; Marsh, T. R.; Dhillon, V. S.; Parsons, S. G.; Copperwheat, C. M.; Steeghs, D.

    2012-05-01

    We present time-resolved spectroscopy of the eclipsing, short-period cataclysmic variable CTCV J1300-3052. Using absorption features from the secondary star, we determine the radial velocity semi-amplitude of the secondary star to be K2= 378 ± 6 km s-1, and its projected rotational velocity to be v sin i= 125 ± 7 km s-1. Using these parameters and Monte Carlo techniques, we obtain masses of M1= 0.79 ± 0.05 M⊙ for the white dwarf primary and M2= 0.198 ± 0.029 M⊙ for the M-type secondary star. These parameters are found to be in good agreement with previous mass determinations found via photometric fitting techniques, supporting the accuracy and validity of photometric mass determinations in short-period CVs.

  5. Near-infrared metallicities, radial velocities, and spectral types for 447 nearby M dwarfs

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

    Newton, Elisabeth R.; Charbonneau, David; Irwin, Jonathan

    We present metallicities, radial velocities, and near-infrared (NIR) spectral types for 447 M dwarfs determined from moderate resolution (R ≈ 2000) NIR spectra obtained with the NASA Infrared Telescope Facility (IRTF)/SpeX. These M dwarfs are primarily targets of the MEarth Survey, a transiting planet survey searching for super Earths around mid-to-late M dwarfs within 33 pc. We present NIR spectral types for each star and new spectral templates for the IRTF in the Y, J, H, and K-bands, created using M dwarfs with near-solar metallicities. We developed two spectroscopic distance calibrations that use NIR spectral type or an index basedmore » on the curvature of the K-band continuum. Our distance calibration has a scatter of 14%. We searched 27 NIR spectral lines and 10 spectral indices for metallicity sensitive features, taking into account correlated noise in our estimates of the errors on these parameters. We calibrated our relation using 36 M dwarfs in common proper pairs with an F-, G-, or K-type star of known metallicity. We validated the physical association of these pairs using proper motions, radial velocities, and spectroscopic distance estimates. Our resulting metallicity calibration uses the sodium doublet at 2.2 μm as the sole indicator for metallicity. It has an accuracy of 0.12 dex inferred from the scatter between the metallicities of the primaries and the estimated metallicities of the secondaries. Our relation is valid for NIR spectral types from M1V to M5V and for –1.0 dex < [Fe/H] < +0.35 dex. We present a new color-color metallicity relation using J – H and J – K colors that directly relates two observables: the distance from the M dwarf main sequence and equivalent width of the sodium line at 2.2 μm. We used radial velocities of M dwarf binaries, observations at different epochs, and comparison between our measurements and precisely measured radial velocities to demonstrate a 4 km s{sup –1} accuracy.« less

  6. Twenty Years of Precise Radial Velocities at Keck and Lick Observatories

    NASA Astrophysics Data System (ADS)

    Wright, J. T.

    2015-10-01

    The precise radial velocity survey at Keck Observatory began over 20 years ago. Its survey of thousands of stars now has the time baseline to be sensitive to planets with decade-long orbits, including Jupiter analogs. I present several newly-finished orbital solutions for long-period giant planets. Although hot Jupiters are generally ``lonely'' (i.e. they are not part of multiplanet systems), those that are not appear to often have giant companions at 5 AU or beyond. I present two of the highest period-ratios among planets in a two-planet system, and some of the longest orbital periods ever measured for exoplanets. In many cases, combining Keck radial velocities from those from other long-term surveys at Lick Observatory, McDonald Observatory, HARPS, and, of course, OHP spectrographs, produces superior orbital fits, constraining both period and eccentricity better than could be possible with any single set alone. Stellar magnetic activity cycles can masquerade as long-period planets. In most cases this effect is very small, but a loud minority of stars, including, apparently, HD 154345, show very strong RV-activity correlations.

  7. DESIGN ANALYSIS OF RADIAL INFLOW TURBINES

    NASA Technical Reports Server (NTRS)

    Glassman, A. J.

    1994-01-01

    This program performs a velocity-diagram analysis required for determining geometry and estimating performance for radial-inflow turbines. Input design requirements are power, mass flow rate, inlet temperature and pressure, and rotative rate. The design variables include stator-exit angle, rotor-exit-tip to rotor-inlet radius ratio, rotor-exit-hub to tip radius ratio, and the magnitude and radial distribution of rotor-exit tangential velocity. The program output includes diameters, total and static efficiences, all absolute and relative temperatures, pressures, and velocities, and flow angles at stator inlet, stator exit, rotor inlet, and rotor exit. Losses accounted for in this program by the internal loss model are three-dimensional (profile plus end wall) viscous losses in the stator and the rotor, the disk-friction loss on the back side of the rotor, the loss due to the clearance between the rotor tip and the outer casing, and the exit velocity loss. The flow analysis is one-dimensional at the stator inlet, stator exit, and rotor inlet, each of these calculation stations being at a constant radius. At the rotor exit where there is a variation in flow-field radius, an axisymmetric two-dimensional analysis is made using constant height sectors. Simple radial equilibrium is used to establish the static pressure gradient at the rotor exit. This program is written in FORTRAN V and has been implemented on a UNIVAC 1100 series computer with a memory requirement of approximately 22K of 36 bit words.

  8. VizieR Online Data Catalog: Radial velocity curves of LMC ellipsoidal variables (Nie+, 2014)

    NASA Astrophysics Data System (ADS)

    Nie, J. D.; Wood, P. R.

    2014-11-01

    We initially selected 86 sequence E candidates from those given in Soszynski et al. 2004 (cat. J/AcA/54/347). The radial velocity observations were taken using the Wide Field Spectrograph (WiFeS) mounted on the Australian National University 2.3m telescope at Siding Spring Observatory. WiFes has six gratings. For our observations, the gratings B7000 (wavelength coverage of 4184-5580Å) and I7000 (wavelength coverage of 6832-9120Å) were chosen for the blue and red CCD, respectively. These two gratings give a two-pixel resolution R=7000. We carried out 18 weeks of radial velocity monitoring, from 2010 September to 2012 March. (2 data files).

  9. New measurements of radial velocities in clusters of galaxies. II

    NASA Astrophysics Data System (ADS)

    Proust, D.; Mazure, A.; Sodre, L.; Capelato, H.; Lund, G.

    1988-03-01

    Heliocentric radial velocities are determined for 100 galaxies in five clusters, on the basis of 380-518-nm observations obtained using a CCD detector coupled by optical fibers to the OCTOPUS multiobject spectrograph at the Cassegrain focus of the 3.6-m telescope at ESO La Silla. The data-reduction procedures and error estimates are discussed, and the results are presented in tables and graphs and briefly characterized.

  10. VizieR Online Data Catalog: IN-SYNC. III. Radial velocities of IC348 stars (Cottaar+, 2015)

    NASA Astrophysics Data System (ADS)

    Cottaar, M.; Covey, K. R.; Foster, J. B.; Meyer, M. R.; Tan, J. C.; Nidever, D. L.; Drew Chojnowski, S.; da Rio, N.; Flaherty, K. M.; Frinchaboy, P. M.; Majewski, S.; Skrutskie, M. F.; Wilson, J. C.; Zasowski, G.

    2015-11-01

    Cottaar et al. (Paper I, 2014, J/ApJ/794/125) describes the analysis of the high-resolution near-infrared spectra obtained by the APOGEE multi-object spectrograph from stars in IC 348, NGC 1333, NGC 2264, and Orion A as part of the INfrared Spectroscopy of Young Nebulous Clusters (IN-SYNC) ancillary program. Using radial velocities determined from APOGEE spectra of 380 likely cluster members, we have measured the radial velocity distribution of the young (2-6Myr) cluster IC 348. (2 data files).

  11. VizieR Online Data Catalog: Radial velocities of 7 cataclysmic binaries (Halpern+, 2015)

    NASA Astrophysics Data System (ADS)

    Halpern, J. P.; Thorstensen, J. R.

    2016-04-01

    Our instrumentation, and reduction and analysis procedures are essentially identical to those described in Paper I (Thorstensen et al. 2013, cat. J/AJ/146/107). All of our optical data are from the MDM Observatory (http://mdm.kpno.noao.edu/index/Instrumentation.html), which comprises the 1.3m McGraw-Hill telescope and the 2.4m Hiltner telescope, both on the southwest ridge of Kitt Peak, Arizona. With a single exception, the radial velocity studies to search for the orbital periods were done on the 2.4m, while high-cadence photometry sensitive to spin periods was carried out on the 1.3m. All of our radial velocity studies used the modular spectrograph, as described in Paper I (Thorstensen et al. 2013, cat. J/AJ/146/107). Most of our velocities are from the the 2.4m telescope. Some spectra of Swift J2124.6+0500, and all the data we used for Swift J0939.7-3224, are from the McGraw-Hill 1.3m telescope, again with the modular spectrograph. For four newly identified objects we have only single spectra that were obtained on two observing runs on the 2.4m. These used the Boller and Chivens CCD spectrograph (CCDS) and the Ohio State Multi-Object Spectrograph (OSMOS). Descriptions of these instruments can be found on the MDM Observatory web page (http://mdm.kpno.noao.edu/index/Instrumentation.html). The objects observed are listed in Table1. Table2 lists the radial velocity data, and Table3 gives parameters of the best-fit sinusoids. (3 data files).

  12. The SLUGGS Survey: A Catalog of Over 4000 Globular Cluster Radial Velocities in 27 Nearby Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Forbes, Duncan A.; Alabi, Adebusola; Brodie, Jean P.; Romanowsky, Aaron J.; Strader, Jay; Foster, Caroline; Usher, Christopher; Spitler, Lee; Bellstedt, Sabine; Pastorello, Nicola; Villaume, Alexa; Wasserman, Asher; Pota, Vincenzo

    2017-03-01

    Here, we present positions and radial velocities for over 4000 globular clusters (GCs) in 27 nearby early-type galaxies from the SLUGGS survey. The SLUGGS survey is designed to be representative of elliptical and lenticular galaxies in the stellar mass range 10 < log {M}* /M ⊙ < 11.7. The data have been obtained over many years, mostly using the very stable multi-object spectrograph DEIMOS on the Keck II 10 m telescope. Radial velocities are measured using the calcium triplet lines, with a velocity accuracy of ±10-15 km s-1. We use phase space diagrams (I.e., velocity-position diagrams) to identify contaminants such as foreground stars and background galaxies, and to show that the contribution of GCs from neighboring galaxies is generally insignificant. Likely ultra-compact dwarfs are tabulated separately. We find that the mean velocity of the GC system is close to that of the host galaxy systemic velocity, indicating that the GC system is in overall dynamical equilibrium within the galaxy potential. We also find that the GC system velocity dispersion scales with host galaxy stellar mass, in a similar manner to the Faber-Jackson relation for the stellar velocity dispersion. Publication of these GC radial velocity catalogs should enable further studies in many areas, such as GC system substructure, kinematics, and host galaxy mass measurements.

  13. VizieR Online Data Catalog: Radial velocities of δ Sagittae (Pugh+, 2015)

    NASA Astrophysics Data System (ADS)

    Pugh, T.; Gray, D. F.; Griffin, R. F.

    2018-01-01

    28 spectra were obtained by Gray and Pugh between 2008 July and 2010 October (MJD 2454674-2455479) with the high-resolution (R~100000) coude spectrograph of the Elginfield Observatory of Western University (Gray 2009ApJ...697.1032G). The signal-to-noise ratios in the continuum, estimated from the photon counts, ranged from 152 to 314 with a mean of 220. The spectrograph has a dispersion of ~0.013 Å/mm and can reach a radial-velocity precision of 25 m/s by reference to water vapour lines inside the spectrograph (Gray & Brown 2006PASP..118.1112G). In the current case our measurement errors (based on exposures taken within a few nights of one another) range from 27 to 160 m/s, with a mean value of 90 m/s. The radial velocities were determined by measuring the positions of the spectral lines at 85 per cent of the line depth for 15 neutral metal lines in the λ6250-Å region. (1 data file).

  14. Radial variation in sap velocity as a function of stem diameter and sapwood thickness in yellow-poplar trees.

    PubMed

    Wullschleger, Stan D.; King, Anthony W.

    2000-04-01

    Canopy transpiration and forest water use are frequently estimated as the product of sap velocity and cross-sectional sapwood area. Few studies, however, have considered whether radial variation in sap velocity and the proportion of sapwood active in water transport are significant sources of uncertainty in the extrapolation process. Therefore, radial profiles of sap velocity were examined as a function of stem diameter and sapwood thickness for yellow-poplar (Liriodendron tulipifera L.) trees growing on two adjacent watersheds in eastern Tennessee. The compensation heat pulse velocity technique was used to quantify sap velocity at four equal-area depths in 20 trees that ranged in stem diameter from 15 to 69 cm, and in sapwood thickness from 2.1 to 14.8 cm. Sap velocity was highly dependent on the depth of probe insertion into the sapwood. Rates of sap velocity were greatest for probes located in the two outer sapwood annuli (P1 and P2) and lowest for probes in closest proximity to the heartwood (P3 and P4). Relative sap velocities averaged 0.98 at P1, 0.66 at P2, 0.41 at P3 and 0.35 at P4. Tree-specific sap velocities measured at each of the four probe positions, divided by the maximum sap velocity measured (usually at P1 or P2), indicated that the fraction of sapwood functional in water transport (f(S)) varied between 0.49 and 0.96. There was no relationship between f(S) and sapwood thickness, or between f(S) and stem diameter. The fraction of functional sapwood averaged 0.66 +/- 0.13 for trees on which radial profiles were determined. No significant depth-related differences were observed for sapwood density, which averaged 469 kg m(-3) across all four probe positions. There was, however, a significant decline in sapwood water content between the two outer probe positions (1.04 versus 0.89 kg kg(-1)). This difference was not sufficient to account for the observed radial variation in sap velocity. A Monte-Carlo analysis indicated that the standard error in

  15. WIYN open cluster study. LIX. Radial velocity membership of the evolved population of the old open cluster NGC 6791

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

    Tofflemire, Benjamin M.; Gosnell, Natalie M.; Mathieu, Robert D.

    2014-10-01

    The open cluster NGC 6791 has been the focus of much recent study due to its intriguing combination of old age and high metallicity (∼8 Gyr, [Fe/H] = +0.30), as well as its location within the Kepler field. As part of the WIYN Open Cluster Study, we present precise (σ = 0.38 km s{sup –1}) radial velocities for proper motion candidate members of NGC 6791 from Platais et al. Our survey, extending down to g' ∼ 16.8, is comprised of the evolved cluster population, including blue stragglers, giants, and horizontal branch stars. Of the 280 proper-motion-selected stars above our magnitudemore » limit, 93% have at least one radial velocity measurement and 79% have three measurements over the course of at least 200 days, sufficient for secure radial-velocity-determined membership of non-velocity-variable stars. The Platais et al. proper motion catalog includes 12 anomalous horizontal branch candidates blueward of the red clump, of which we find only 4 to be cluster members. Three fall slightly blueward of the red clump and the fourth is consistent with being a blue straggler. The cleaned color-magnitude diagram shows a richly populated red giant branch and a blue straggler population. Half of the blue stragglers are in binaries. From our radial velocity measurement distribution, we find the cluster's radial velocity dispersion to be σ {sub c} = 0.62 ± 0.10 km s{sup –1}. This corresponds to a dynamical mass of ∼4600 M {sub ☉}.« less

  16. Miniature Exoplanet Radial Velocity Array (MINERVA) I. Design, Commissioning, and First Science Results

    NASA Astrophysics Data System (ADS)

    Swift, Jonathan J.; Bottom, Michael; Johnson, John A.; Wright, Jason T.; McCrady, Nate; Wittenmyer, Robert A.; Plavchan, Peter; Riddle, Reed; Muirhead, Philip S.; Herzig, Erich; Myles, Justin; Blake, Cullen H.; Eastman, Jason; Beatty, Thomas G.; Barnes, Stuart I.; Gibson, Steven R.; Lin, Brian; Zhao, Ming; Gardner, Paul; Falco, Emilio; Criswell, Stephen; Nava, Chantanelle; Robinson, Connor; Sliski, David H.; Hedrick, Richard; Ivarsen, Kevin; Hjelstrom, Annie; de Vera, Jon; Szentgyorgyi, Andrew

    2015-04-01

    The Miniature Exoplanet Radial Velocity Array (MINERVA) is a U.S.-based observational facility dedicated to the discovery and characterization of exoplanets around a nearby sample of bright stars. MINERVA employs a robotic array of four 0.7-m telescopes outfitted for both high-resolution spectroscopy and photometry, and is designed for completely autonomous operation. The primary science program is a dedicated radial velocity survey and the secondary science objective is to obtain high-precision transit light curves. The modular design of the facility and the flexibility of our hardware allows for both science programs to be pursued simultaneously, while the robotic control software provides a robust and efficient means to carry out nightly observations. We describe the design of MINERVA, including major hardware components, software, and science goals. The telescopes and photometry cameras are characterized at our test facility on the Caltech campus in Pasadena, California, and their on-sky performance is validated. The design and simulated performance of the spectrograph is briefly discussed as we await its completion. New observations from our test facility demonstrate sub-mmag photometric precision of one of our radial velocity survey targets, and we present new transit observations and fits of WASP-52b-a known hot-Jupiter with an inflated radius and misaligned orbit. The process of relocating the MINERVA hardware to its final destination at the Fred Lawrence Whipple Observatory in southern Arizona has begun, and science operations are expected to commence in 2015.

  17. The LCES HIRES/Keck Precision Radial Velocity Exoplanet Survey

    NASA Astrophysics Data System (ADS)

    Butler, R. Paul; Vogt, Steven S.; Laughlin, Gregory; Burt, Jennifer A.; Rivera, Eugenio J.; Tuomi, Mikko; Teske, Johanna; Arriagada, Pamela; Diaz, Matias; Holden, Brad; Keiser, Sandy

    2017-05-01

    We describe a 20 year survey carried out by the Lick-Carnegie Exoplanet Survey Team (LCES), using precision radial velocities from HIRES on the Keck I telescope to find and characterize extrasolar planetary systems orbiting nearby F, G, K, and M dwarf stars. We provide here 60,949 precision radial velocities for 1624 stars contained in that survey. We tabulate a list of 357 significant periodic signals that are of constant period and phase, and not coincident in period and/or phase with stellar activity indices. These signals are thus strongly suggestive of barycentric reflex motion of the star induced by one or more candidate exoplanets in Keplerian motion about the host star. Of these signals, 225 have already been published as planet claims, 60 are classified as significant unpublished planet candidates that await photometric follow-up to rule out activity-related causes, and 54 are also unpublished, but are classified as “significant” signals that require confirmation by additional data before rising to classification as planet candidates. Of particular interest is our detection of a candidate planet with M\\sin (I)=3.8 {M}\\oplus , and P = 9.9 days orbiting Lalande 21185, the fourth-closest main-sequence star to the Sun. For each of our exoplanetary candidate signals, we provide the period and semi-amplitude of the Keplerian orbital fit, and a likelihood ratio estimate of its statistical significance. We also tabulate 18 Keplerian-like signals that we classify as likely arising from stellar activity.

  18. Shear-Velocity Structure and Azimuthal and Radial Anisotropy Beneath the Kaapvaal Craton From Bayesian Inversion of Surface-Wave Data: Inferences for the Architecture and Early Evolution of Cratons

    NASA Astrophysics Data System (ADS)

    Lebedev, S.; Ravenna, M.; Adam, J.

    2017-12-01

    Seismic anisotropy provides essential information on the deformation of the lithosphere. Knowledge of anisotropy also allows us to isolate the isotropic-average seismic velocities, relatable to the lithospheric temperature and composition. We use Rayleigh and Love-wave phase velocities and their azimuthal anisotropy measured in broad period ranges across the footprint of the Southern Africa Seismic Experiment (SASE), from the Kaapvaal Craton to the Limpopo Belt. We invert the data using our recently developed, fully non-linear Markov Chain Monte Carlo method and determine, for the first time, both the isotropic-average S velocity and its radial and azimuthal anisotropy as a function of depth from the upper crust down to the asthenosphere. The probabilistic inversion provides a way to quantify non-uniqueness, using direct parameter-space sampling, and assess model uncertainties. The high-velocity anomaly indicative of the cold cratonic lithosphere bottoms at 200-250 km beneath the central and western Kaapvaal Craton, underlain by a low-velocity zone. Beneath northern Kaapvaal and Limpopo, by contrast, high velocities extend down to 300-350 km. Although this does not require a lithosphere that has maintained this thickness over a geologically long time, the data does require the mantle to be anomalously cold down to 300-350 km. Interestingly, topography correlates with the thickness of this high-velocity layer, with lower elevations where the lid is thicker. Radial shear-wave anisotropy is in the 2-5 percent range (Vsh > Vsv) from the lower crust down to 200 km, below which depth it decreases gradually. Radial variations in the amplitude of radial anisotropy show no clear relationship with those in the amplitude of azimuthal anisotropy or isotropic-average Vs anomalies. Azimuthal anisotropy changes the fast-propagation direction near the base of the lithosphere (200-300 km depth), from the laterally varying fast azimuths in the lower lithosphere to a spatially

  19. RadVel: The Radial Velocity Modeling Toolkit

    NASA Astrophysics Data System (ADS)

    Fulton, Benjamin J.; Petigura, Erik A.; Blunt, Sarah; Sinukoff, Evan

    2018-04-01

    RadVel is an open-source Python package for modeling Keplerian orbits in radial velocity (RV) timeseries. RadVel provides a convenient framework to fit RVs using maximum a posteriori optimization and to compute robust confidence intervals by sampling the posterior probability density via Markov Chain Monte Carlo (MCMC). RadVel allows users to float or fix parameters, impose priors, and perform Bayesian model comparison. We have implemented real-time MCMC convergence tests to ensure adequate sampling of the posterior. RadVel can output a number of publication-quality plots and tables. Users may interface with RadVel through a convenient command-line interface or directly from Python. The code is object-oriented and thus naturally extensible. We encourage contributions from the community. Documentation is available at http://radvel.readthedocs.io.

  20. Eclipsing binaries and fast rotators in the Kepler sample. Characterization via radial velocity analysis from Calar Alto

    NASA Astrophysics Data System (ADS)

    Lillo-Box, J.; Barrado, D.; Mancini, L.; Henning, Th.; Figueira, P.; Ciceri, S.; Santos, N.

    2015-04-01

    Context. The Kepler mission has searched for planetary transits in more than two hundred thousand stars by obtaining very accurate photometric data over a long period of time. Among the thousands of detected candidates, the planetary nature of around 15% has been established or validated by different techniques. But additional data are needed to characterize the rest of the candidates and reject other possible configurations. Aims: We started a follow-up program to validate, confirm, and characterize some of the planet candidates. In this paper we present the radial velocity analysis of those that present large variations, which are compatible with being eclipsing binaries. We also study those showing high rotational velocities, which prevents us from reaching the necessary precision to detect planetary-like objects. Methods: We present new radial velocity results for 13 Kepler objects of interest (KOIs) obtained with the CAFE spectrograph at the Calar Alto Observatory and analyze their high-spatial resolution (lucky) images obtained with AstraLux and the Kepler light curves of some interesting cases. Results: We have found five spectroscopic and eclipsing binaries (group A). Among them, the case of KOI-3853 is of particular interest. This system is a new example of the so-called heartbeat stars, showing dynamic tidal distortions in the Kepler light curve. We have also detected duration and depth variations of the eclipse. We suggest possible scenarios to explain such an effect, including the presence of a third substellar body possibly detected in our radial velocity analysis. We also provide upper mass limits to the transiting companions of six other KOIs with high rotational velocities (group B). This property prevents the radial velocity method from achieving the necessary precision to detect planetary-like masses. Finally, we analyze the large radial velocity variations of two other KOIs, which are incompatible with the presence of planetary-mass objects

  1. Study on a multi-delay spectral interferometry for stellar radial velocity measurement

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Jiang, Haijiao; Tang, Jin; Ji, Hangxin; Zhu, Yongtian; Wang, Liang

    2014-08-01

    High accuracy radial velocity measurement isn't only one of the most important methods for detecting earth-like Exoplanets, but also one of the main developing fields of astronomical observation technologies in future. Externally dispersed interferometry (EDI) generates a kind of particular interference spectrum through combining a fixed-delay interferometer with a medium-resolution spectrograph. It effectively enhances radial velocity measuring accuracy by several times. Another further study on multi-delay interferometry was gradually developed after observation success with only a fixed-delay, and its relative instrumentation makes more impressive performance in near Infrared band. Multi-delay is capable of giving wider coverage from low to high frequency in Fourier field so that gives a higher accuracy in radial velocity measurement. To study on this new technology and verify its feasibility at Guo Shoujing telescope (LAMOST), an experimental instrumentation with single fixed-delay named MESSI has been built and tested at our lab. Another experimental study on multi-delay spectral interferometry given here is being done as well. Basically, this multi-delay experimental system is designed in according to the similar instrument named TEDI at Palomar observatory and the preliminary test result of MESSI. Due to existence of LAMOST spectrograph at lab, a multi-delay interferometer design actually dominates our work. It's generally composed of three parts, respectively science optics, phase-stabilizing optics and delay-calibrating optics. To switch different fixed delays smoothly during observation, the delay-calibrating optics is possibly useful to get high repeatability during switching motion through polychromatic interferometry. Although this metrology is based on white light interferometry in theory, it's different that integrates all of interference signals independently obtained by different monochromatic light in order to avoid dispersion error caused by

  2. Fully distributed absolute blood flow velocity measurement for middle cerebral arteries using Doppler optical coherence tomography

    PubMed Central

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M.; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D.; Chen, Zhongping

    2016-01-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence tomography showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement. PMID:26977365

  3. Fully distributed absolute blood flow velocity measurement for middle cerebral arteries using Doppler optical coherence tomography.

    PubMed

    Qi, Li; Zhu, Jiang; Hancock, Aneeka M; Dai, Cuixia; Zhang, Xuping; Frostig, Ron D; Chen, Zhongping

    2016-02-01

    Doppler optical coherence tomography (DOCT) is considered one of the most promising functional imaging modalities for neuro biology research and has demonstrated the ability to quantify cerebral blood flow velocity at a high accuracy. However, the measurement of total absolute blood flow velocity (BFV) of major cerebral arteries is still a difficult problem since it is related to vessel geometry. In this paper, we present a volumetric vessel reconstruction approach that is capable of measuring the absolute BFV distributed along the entire middle cerebral artery (MCA) within a large field-of-view. The Doppler angle at each point of the MCA, representing the vessel geometry, is derived analytically by localizing the artery from pure DOCT images through vessel segmentation and skeletonization. Our approach could achieve automatic quantification of the fully distributed absolute BFV across different vessel branches. Experiments on rodents using swept-source optical coherence tomography showed that our approach was able to reveal the consequences of permanent MCA occlusion with absolute BFV measurement.

  4. Absolute and geometric parameters of contact binary BO Arietis

    NASA Astrophysics Data System (ADS)

    Gürol, B.; Gürsoytrak, S. H.; Bradstreet, D. H.

    2015-08-01

    We present the results of our investigation on the geometrical and physical parameters of the W UMa type binary system BO Ari from analyzed CCD (BVRI) light curves and radial velocity data. The photometric data were obtained in 2009 and 2010 at Ankara University Observatory (AUO) and the spectroscopic observations were made in 2007 and 2010 at TUBITAK National Observatory (TUG). These light and radial velocity observations were analyzed simultaneously by using the Wilson-Devinney (2013 revision) code to obtain absolute and geometrical parameters. The system was determined to be an A-type W UMa system. Combining our photometric solution with the spectroscopic data we derived masses and radii of the eclipsing system to be M1 = 0.995M⊙,M2 = 0.189M⊙,R1 = 1.090R⊙ and R2 = 0.515R⊙ . Finally, we discuss the evolutionary status of the system.

  5. WIYN Open Cluster Study. XXXII. Stellar Radial Velocities in the Old Open Cluster NGC 188

    NASA Astrophysics Data System (ADS)

    Geller, Aaron M.; Mathieu, Robert D.; Harris, Hugh C.; McClure, Robert D.

    2008-06-01

    We present the results of our ongoing radial-velocity (RV) survey of the old (7 Gyr) open cluster NGC 188. Our WIYN 3.5 m data set spans a time baseline of 11 years, a magnitude range of 12 <= V <= 16.5 (1.18-0.94 M sun), and a 1° diameter region on the sky. With the addition of a Domain Astrophysical Observatory data set we extend our bright limit to V = 10.8 and, for some stars, extend our time baseline to 35 years. Our magnitude limits include solar-mass main-sequence stars, subgiants, giants, and blue stragglers (BSs), and our spatial coverage extends radially to 17 pc (~13 core radii). For the WIYN data we present a detailed description of our data reduction process and a thorough analysis of our measurement precision of 0.4 km s-1 for narrow-lined stars. We have measured radial velocities for 1046 stars in the direction of NGC 188, and have calculated RV membership probabilities for stars with >=3 measurements, finding 473 to be likely cluster members. We detect 124 velocity-variable cluster members, all of which are likely to be dynamically hard-binary stars. Using our single member stars, we find an average cluster radial velocity of -42.36 ± 0.04 km s-1. We use our precise RV and proper-motion membership data to greatly reduce field-star contamination in our cleaned color-magnitude diagram, from which we identify six stars of note that lie far from a standard single-star isochrone. We present a detailed study of the spatial distribution of cluster-member populations, and find the binaries to be centrally concentrated, providing evidence for the presence of mass segregation in NGC 188. We observe the BSs to populate a bimodal spatial distribution that is not centrally concentrated, suggesting that we may be observing two populations of BSs in NGC 188, including a centrally concentrated distribution as well as a halo population. Finally, we find NGC 188 to have a global RV dispersion of 0.64 ± 0.04 km s-1, which may be inflated by up to 0.23 km s-1 from

  6. K-KIDS: K Dwarfs and Their Companions. First Results from Radial Velocity Survey with CHIRON Spectrograph

    NASA Astrophysics Data System (ADS)

    Paredes, Leonardo; Henry, Todd; Nusdeo, Daniel; Winters, J.; Dincer, Tolga

    2018-01-01

    We present the K-KIDS project, an effort to survey a large sample of K dwarfs and their companions, the KIDS. We are observing a carefully vetted equatorial sample (DEC = -30 to +30) of more than 1000 K dwarfs within 50 pc to make a comprehensive assessment of stellar, substellar and planetary companions with separations of 0.1 to 10,000 AU.The initial sample of 1048 stars has been compiled using astrometric data from Hipparcos and photometric data from Tycho-2 and 2MASS. Four different imaging and spectroscopic surveys are underway. Here we present the strategy and initial results for our high-precision radial velocity survey for the closest companions using the CHIRON spectrograph on the CTIO/SMARTS 1.5m telescope. Individual measurements with CHIRON at R = 80,000 using ThAr wavelength calibration, indicate that for K dwarf radial velocity standards with V = 5.8, 7.0 and 8.0 yield precisions over 6 weeks of observing of 7.4 m/s, 9.8 m/s and 5.7 m/s. In the first two months, a core sample of 42 K dwarfs, including carefully selected calibration systems as well as previously unobserved stars, was observed every few nights to detect the radial velocity signals of close companions. In our calibration stellar systems, we have confirmed the suitability of CHIRON for our studies, by having found periodic radial velocity perturbations consistent with hot Jupiter and stellar companions previously detected. This set forms the foundation of our one-year survey of 100 K dwarfs with magnitudes as faint as V = 11.5, for which we should detect companions with masses as low as Jupiter.In light of the promising performance and efficiency of the CHIRON spectrograph for a long-term radial velocity survey, we have expanded our initial sample using Gaia Data Release 1 to 1824 K dwarfs within 50 pc. Ultimately, the combination of all four surveys will provide an unprecedented portrait of K dwarfs and their kids.This effort has been supported by the NSF through grant AST-1517413, and

  7. IN-SYNC VI. Identification and Radial Velocity Extraction for 100+ Double-Lined Spectroscopic Binaries in the APOGEE/IN-SYNC Fields

    NASA Astrophysics Data System (ADS)

    Fernandez, M. A.; Covey, Kevin R.; De Lee, Nathan; Chojnowski, S. Drew; Nidever, David; Ballantyne, Richard; Cottaar, Michiel; Da Rio, Nicola; Foster, Jonathan B.; Majewski, Steven R.; Meyer, Michael R.; Reyna, A. M.; Roberts, G. W.; Skinner, Jacob; Stassun, Keivan; Tan, Jonathan C.; Troup, Nicholas; Zasowski, Gail

    2017-08-01

    We present radial velocity measurements for 70 high confidence, and 34 potential binary systems in fields containing the Perseus Molecular Cloud, Pleiades, NGC 2264, and the Orion A star-forming region. Eighteen of these systems have been previously identified as binaries in the literature. Candidate double-lined spectroscopic binaries (SB2s) are identified by analyzing the cross-correlation functions (CCFs) computed during the reduction of each APOGEE spectrum. We identify sources whose CCFs are well fit as the sum of two Lorentzians as likely binaries, and provide an initial characterization of the system based on the radial velocities indicated by that dual fit. For systems observed over several epochs, we present mass ratios and systemic velocities; for two systems with observations on eight or more epochs, and which meet our criteria for robust orbital coverage, we derive initial orbital parameters. The distribution of mass ratios for multi-epoch sources in our sample peaks at q = 1, but with a significant tail toward lower q values. Tables reporting radial velocities, systemic velocities, and mass ratios are provided online. We discuss future improvements to the radial velocity extraction method we employ, as well as limitations imposed by the number of epochs currently available in the APOGEE database. The Appendix contains brief notes from the literature on each system in the sample, and more extensive notes for select sources of interest.

  8. Frequentist and Bayesian Orbital Parameter Estimaton from Radial Velocity Data Using RVLIN, BOOTTRAN, and RUN DMC

    NASA Astrophysics Data System (ADS)

    Nelson, Benjamin Earl; Wright, Jason Thomas; Wang, Sharon

    2015-08-01

    For this hack session, we will present three tools used in analyses of radial velocity exoplanet systems. RVLIN is a set of IDL routines used to quickly fit an arbitrary number of Keplerian curves to radial velocity data to find adequate parameter point estimates. BOOTTRAN is an IDL-based extension of RVLIN to provide orbital parameter uncertainties using bootstrap based on a Keplerian model. RUN DMC is a highly parallelized Markov chain Monte Carlo algorithm that employs an n-body model, primarily used for dynamically complex or poorly constrained exoplanet systems. We will compare the performance of these tools and their applications to various exoplanet systems.

  9. Radial velocities of stars in the globular cluster M4 and the cluster distance

    NASA Technical Reports Server (NTRS)

    Peterson, R. C.; Rees, Richard F.; Cudworth, Kyle M.

    1995-01-01

    The internal stellar velocity distribution of the globular cluster M4 is evaluated from nearly 200 new radial velocity measurements good to 1 km/s and a rederivation of existing proper motions. The mean radial velocity of the cluster is 70.9 +/- 0.6 km/s. The velocity dispersion is 3.5 +/- 0.3 km/s at the core, dropping marginally towards the outskirts. Such a low internal dispersion is somewhat at odds with the cluster's orbit, for which the perigalacticon is sufficiently close to the galactic center that the probability of cluster disruption is high; a tidal radius two-thirds the currently accepted value would eliminate the discrepancy. The cluster mass-to-light ratio is also small, M/L(sub V) = 1.0 +/- 0.4 in solar units. M4 thus joins M22 as a cluster of moderate and concentration with a mass-to-light ratio among the lowest known. The astrometric distance to the cluster is also smaller than expected, 1.72 +/- 0.14 kpc. This is only consistent with conventional estimates of the luminosity of horizontal branch stars provided an extinction law R = A(sub V)/E(B-V) approximately 4 is adopted, as has been suggested recently by several authors.

  10. The Joker: A custom Monte Carlo sampler for binary-star and exoplanet radial velocity data

    NASA Astrophysics Data System (ADS)

    Price-Whelan, Adrian M.; Hogg, David W.; Foreman-Mackey, Daniel; Rix, Hans-Walter

    2017-01-01

    Given sparse or low-quality radial-velocity measurements of a star, there are often many qualitatively different stellar or exoplanet companion orbit models that are consistent with the data. The consequent multimodality of the likelihood function leads to extremely challenging search, optimization, and MCMC posterior sampling over the orbital parameters. The Joker is a custom-built Monte Carlo sampler that can produce a posterior sampling for orbital parameters given sparse or noisy radial-velocity measurements, even when the likelihood function is poorly behaved. The method produces correct samplings in orbital parameters for data that include as few as three epochs. The Joker can therefore be used to produce proper samplings of multimodal pdfs, which are still highly informative and can be used in hierarchical (population) modeling.

  11. VizieR Online Data Catalog: Radial velocities measurements (Duflot+ 1997)

    NASA Astrophysics Data System (ADS)

    Fehrenbach, C.; Duflot, M.; Mannone, C.; Burnage, R.; Genty, V.

    1996-11-01

    We publish 1879 radial velocities of stars distributed in 105 fields of 4x4degres. We continue the PPO series (Fehrenbach et al. 1987A&AS...71..263F, 1987A&AS...71..275F, 1990A&AS...83...91F and 1992A&AS...95..541F; Duflot et al. 1990A&AS...83..251D, 1992A&AS...94..479D, 1992A&AS...95..541F and 1995A&AS..110..177D), using the Fehrenbach objective prism method. (2 data files).

  12. Magnetic field and radial velocities of the star β CrB

    NASA Astrophysics Data System (ADS)

    Han, Inwoo; Valyavin, G.; Galazutdinov, G.; Plachinda, S.; Butkovskaya, V.; Lee, B. C.; Kim, Kang-Min; Jeong, Gwanghui; Romanyuk, I.; Burlakova, T.

    2018-06-01

    We present the results of long term high-resolution spectral and spectro-polarimetric observations of the classic spectroscopic binary star β Coronae Borealis, which is also well known for its chemical peculiarity and strong magnetic field. One of the main objectives of these observations was to check some suggestions of the presence of a third low-mass component in the system. Analysing our own radial velocity measurements of β Coronae Borealis obtained between 2004 and 2013 together with other RV and astrometric data taken from literature, we have considerably improved the orbital elements of the star. Using residual RVs obtained after subtracting the orbit from the observed RV, we detected a significant periodic signal consistent with the well known 18.4868 day rotation/magnetic period of the star. The shape of the residual RVs folded with the rotation period exhibits a bimodal structure. In order to clarify the origin of the residual RV variation, we model the RV variation due to rotational modulation Zeeman patterns in the spectral lines of β Coronae Borealis spectra. The results of this analysis and the investigation of chemical inhomogeneities in the spectra of β Coronae Borealis convincingly support the "magnetic" nature of the observed radial velocity variations.

  13. Astrometry, Radial Velocity, and Photometry: The HD 128311 System Remixed with Data from HST, HET, and APT

    NASA Astrophysics Data System (ADS)

    McArthur, Barbara. E.; Benedict, G. Fritz; Henry, Gregory W.; Hatzes, Artie; Cochran, William D.; Harrison, Tom E.; Johns-Krull, Chris; Nelan, Ed

    2014-11-01

    We have used high-cadence radial velocity measurements from the Hobby-Eberly Telescope with published velocities from the Lick 3 m Shane Telescope, combined with astrometric data from the Hubble Space Telescope (HST) Fine Guidance Sensors to refine the orbital parameters of the HD 128311 system, and determine an inclination of 55.°95 ± 14.°55 and true mass of 3.789 +0.924 -0.432 M JUP for HD 128311 c. The combined radial velocity data also reveal a short period signal which could indicate a third planet in the system with an Msin i of 0.133 ± 0.005 M JUP or stellar phenomena. Photometry from the T12 0.8 m automatic photometric telescope at the Fairborn Observatory and HST are used to determine a photometric period close to, but not within the errors of the radial velocity signal. We performed a cross-correlation bisector analysis of the radial velocity data to look for correlations with the photometric period and found none. Dynamical integrations of the proposed system show long-term stability with the new orbital parameters of over 10 million years. Our new orbital elements do not support the claims of HD 128311 b and c being in mean motion resonance. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen, and observations with T12 0.8 m automatic photoelectric telescope (APT) at Fairborn Observatory.

  14. Bayesian planet searches in radial velocity data

    NASA Astrophysics Data System (ADS)

    Gregory, Phil

    2015-08-01

    Intrinsic stellar variability caused by magnetic activity and convection has become the main limiting factor for planet searches in both transit and radial velocity (RV) data. New spectrographs are under development like ESPRESSO and EXPRES that aim to improve RV precision by a factor of approximately 100 over the current best spectrographs, HARPS and HARPS-N. This will greatly exacerbate the challenge of distinguishing planetary signals from stellar activity induced RV signals. At the same time good progress has been made in simulating stellar activity signals. At the Porto 2014 meeting, “Towards Other Earths II,” Xavier Dumusque challenged the community to a large scale blind test using the simulated RV data to understand the limitations of present solutions to deal with stellar signals and to select the best approach. My talk will focus on some of the statistical lesson learned from this challenge with an emphasis on Bayesian methodology.

  15. Absolute and geometric parameters of contact binary V1918 Cyg

    NASA Astrophysics Data System (ADS)

    Gürol, B.

    2016-08-01

    We present the results of our investigation on the geometrical and physical parameters of the W UMa type binary system V1918 Cyg from analyzed CCD (BVR) light curves and radial velocity data. We used the photometric data published by Yang et al. (2013) and spectroscopic data obtained in 2012 at TUBITAK National Observatory (TUG). The light and radial velocity observations were analyzed simultaneously by using the Wilson-Devinney (2015 revision) code to obtain absolute and geometrical parameters of the system. It is confirmed that the system is an A-type W UMa as indicated by Yang et al. (2013). Combining our spectroscopic data with the photometric solution we derived masses and radii of the eclipsing system as M1 = 1.302M⊙ , M2 = 0.362M⊙ , R1 = 1.362R⊙ and R2 = 0.762R⊙ . Finally, we discuss the evolutionary status of the system.

  16. Precision stellar radial velocity measurements with FIDEOS at the ESO 1-m telescope of La Silla

    NASA Astrophysics Data System (ADS)

    Vanzi, L.; Zapata, A.; Flores, M.; Brahm, R.; Tala Pinto, M.; Rukdee, S.; Jones, M.; Ropert, S.; Shen, T.; Ramirez, S.; Suc, V.; Jordán, A.; Espinoza, N.

    2018-07-01

    We present results from the commissioning and early science programs of FIbre Dual Echelle Optical Spectrograph (FIDEOS), the new high-resolution echelle spectrograph developed at the Centre of Astro Engineering of Pontificia Universidad Catolica de Chile, and recently installed at the ESO 1-m telescope of La Silla. The instrument provides spectral resolution R ˜ 43 000 in the visible spectral range 420-800 nm, reaching a limiting magnitude of 11 in V band. Precision in the measurement of radial velocity is guaranteed by light feeding with an octagonal optical fibre, suitable mechanical isolation, thermal stabilization, and simultaneous wavelength calibration. Currently the instrument reaches radial velocity stability of ˜8 m s-1 over several consecutive nights of observation.

  17. VizieR Online Data Catalog: Radial velocity curve of 51 Peg (Birkby+, 2017)

    NASA Astrophysics Data System (ADS)

    Birkby, J. L.; de Kok, R. J.; Brogi, M.; Schwarz, H.; Snellen, I. A. G.

    2017-07-01

    We observed the bright star 51 Peg (G2.5V, V=5.46mag, K=3.91mag) for 3.7hr during the night beginning 2010 October 21, using the CRyogenic InfraRed Echelle Spectrograph (CRIRES) mounted at Nasmyth A at the VLT (8.2 m UT1/Antu), Cerro Paranal, Chile. The observations were collected as part of the ESO large program 186.C-0289. The instrument setup consisted of a 0.2 arcsec slit centred on 3236nm (order 17), in combination with the Multi-Application Curvature Adaptive Optic system (MACAO). The CRIRES infrared detector is comprised of four Aladdin III InSb-arrays, each with 1024*512 pixels, and separated by a gap of 280 pixels. The resulting wavelength coverage of the observations was 3.1806<λ(μm)<3.2659 with a resolution of R{approx}100000 per resolution element. We observed 51 Peg continuously while its hot Jupiter companion passed through orbital phases 0.55<~{Phi}<~0.58, corresponding to an expected change in the planet's radial velocity of ΔRVP=-23km/s (15 pixels on the CRIRES detectors). In total, we obtained 42 spectra, with the first 20 spectra each consisting of two sets of 5*20s exposures, and the remainder each consisting of two sets of 5*30s exposures. The increase in the exposure time was aimed at maintaining a constant signal-to-noise ratio (S/N) in the continuum of the observed stellar spectra after a sudden and significant deterioration of the seeing (increasing from 0.75 to 1.4 arcsec between one set of frames, see Section 2.3). To enable accurate sky-background subtraction, the telescope was nodded along the slit by 10 arcsec between each set of exposures in a classic ABBA sequence, with each of the final 42 extracted spectra consisting of an AB or BA pair. A standard set of CRIRES calibration frames was taken the following morning. To ensure we had its most up-to-date orbital solution, we compiled an extensive repository of literature and archival radial velocity measurements of the star 51 Peg from multiple observatories. These data are given in

  18. Radial Velocities of 41 Kepler Eclipsing Binaries

    NASA Astrophysics Data System (ADS)

    Matson, Rachel A.; Gies, Douglas R.; Guo, Zhao; Williams, Stephen J.

    2017-12-01

    Eclipsing binaries are vital for directly determining stellar parameters without reliance on models or scaling relations. Spectroscopically derived parameters of detached and semi-detached binaries allow us to determine component masses that can inform theories of stellar and binary evolution. Here we present moderate resolution ground-based spectra of stars in close binary systems with and without (detected) tertiary companions observed by NASA’s Kepler mission and analyzed for eclipse timing variations. We obtain radial velocities and spectroscopic orbits for five single-lined and 35 double-lined systems, and confirm one false positive eclipsing binary. For the double-lined spectroscopic binaries, we also determine individual component masses and examine the mass ratio {M}2/{M}1 distribution, which is dominated by binaries with like-mass pairs and semi-detached classical Algol systems that have undergone mass transfer. Finally, we constrain the mass of the tertiary component for five double-lined binaries with previously detected companions.

  19. Noise Sources in Photometry and Radial Velocities

    NASA Astrophysics Data System (ADS)

    Oshagh, Mahmoudreza

    The quest for Earth-like, extrasolar planets (exoplanets), especially those located inside the habitable zone of their host stars, requires techniques sensitive enough to detect the faint signals produced by those planets. The radial velocity (RV) and photometric transit methods are the most widely used and also the most efficient methods for detecting and characterizing exoplanets. However, presence of astrophysical "noise" makes it difficult to detect and accurately characterize exoplanets. It is important to note that the amplitude of such astrophysical noise is larger than both the signal of Earth-like exoplanets and state-of-the-art instrumentation limit precision, making this a pressing topic that needs to be addressed. In this chapter, I present a general review of the main sources of noise in photometric and RV observations, namely, stellar oscillations, granulation, and magnetic activity. Moreover, for each noise source I discuss the techniques and observational strategies which allow us to mitigate their impact.

  20. Comparison of CME radial velocities from a flux rope model and an ice cream cone model

    NASA Astrophysics Data System (ADS)

    Kim, T.; Moon, Y.; Na, H.

    2011-12-01

    Coronal Mass Ejections (CMEs) on the Sun are the largest energy release process in the solar system and act as the primary driver of geomagnetic storms and other space weather phenomena on the Earth. So it is very important to infer their directions, velocities and three-dimensional structures. In this study, we choose two different models to infer radial velocities of halo CMEs since 2008 : (1) an ice cream cone model by Xue et al (2005) using SOHO/LASCO data, (2) a flux rope model by Thernisien et al. (2009) using the STEREO/SECCHI data. In addition, we use another flux rope model in which the separation angle of flux rope is zero, which is morphologically similar to the ice cream cone model. The comparison shows that the CME radial velocities from among each model have very good correlations (R>0.9). We will extending this comparison to other partial CMEs observed by STEREO and SOHO.

  1. VizieR Online Data Catalog: Radial velocity monitoring of 5 FGK stars (Endl+, 2016)

    NASA Astrophysics Data System (ADS)

    Endl, M.; Brugamyer, E. J.; Cochran, W. D.; MacQueen, P. J.; Robertson, P.; Meschiari, S.; Ramirez, I.; Shetrone, M.; Gullikson, K.; Johnson, M. C.; Wittenmyer, R.; Horner, J.; Ciardi, D. R.; Horch, E.; Simon, A. E.; Howell, S. B.; Everett, M.; Caldwell, C.; Castanheira, B. G.

    2016-04-01

    Our radial velocity (RV) measurements were obtained using the 2.7m Harlan J. Smith Telescope (HJST; R=60000, 3750-10200Å). For HD 95872, we also obtained 10 precise RV measurements using the 10m Keck I and its HIRES spectrograph (R=50000). (6 data files).

  2. VizieR Online Data Catalog: Radial velocities of TYC 4110-01037-1 (Wisniewski+, 2012)

    NASA Astrophysics Data System (ADS)

    Wisniewski, J. P.; Ge, J.; Crepp, J. R.; de, Lee N.; Eastman, J.; Esposito, M.; Fleming, S. W.; Gaudi, B. S.; Ghezzi, L.; Gonzalez Hernandez, J. I.; Lee, B. L.; Stassun, K. G.; Agol, E.; Prieto, C. A.; Barnes, R.; Bizyaev, D.; Cargile, P.; Chang, L.; da Costa, L. N.; Porto de Mello, G. F.; Femenia, B.; Ferreira, L. D.; Gary, B.; Hebb, L.; Holtzman, J.; Liu, J.; Ma, B.; Mack, C. E.; Mahadevan, S.; Maia, M. A. G.; Nguyen, D. C.; Ogando, R. L. C.; Oravetz, D. J.; Paegert, M.; Pan, K.; Pepper, J.; Rebolo, R.; Santiago, B.; Schneider, D. P.; Shelden, A. C.; Simmons, A.; Tofflemire, B. M.; Wan, X.; Wang, J.; Zhao, B.

    2013-06-01

    The Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS), one of the three surveys being executed during the Sloan Digital Sky Survey (SDSS) III (Eisenstein et al., 2011AJ....142...72E), is a four-year program which is monitoring the radial velocities of ~3300 V=7.6-12 FGK-type dwarfs and subgiants. Our primary RV observations of TYC 4110-01037-1 were obtained during the first two years of the SDSS-III MARVELS survey, which uses a dispersed fixed-delay interferometer on the SDSS 2.5m telescope. A total of 32 observations were obtained over the course of ~2 years. Each 50minute observation yielded two fringing spectra from the interferometer spanning the wavelength regime ~500-570nm with R~12000. Supporting RV observations were obtained with the 3.6m Telescopio Nazionale Galileo (TNG) using its SARG spectrograph. The 0.8"*5.3" slit provided R~57000 spectroscopy between 462-792nm. (1 data file).

  3. A large systematic search for close supermassive binary and rapidly recoiling black holes - III. Radial velocity variations

    NASA Astrophysics Data System (ADS)

    Runnoe, Jessie C.; Eracleous, Michael; Pennell, Alison; Mathes, Gavin; Boroson, Todd; Sigurðsson, Steinn; Bogdanović, Tamara; Halpern, Jules P.; Liu, Jia; Brown, Stephanie

    2017-06-01

    We have been spectroscopically monitoring 88 quasars selected to have broad Hβ emission lines offset from their systemic redshift by thousands of km s-1. By analogy with single-lined spectroscopic binary stars, we consider these quasars to be candidates for hosting supermassive black hole binaries (SBHBs). In this work, we present new radial velocity measurements, typically three to four per object over a time period of up to 12 yr in the observer's frame. In 29/88 of the SBHB candidates, no variability of the shape of the broad Hβ profile is observed, which allows us to make reliable measurements of radial velocity changes. Among these, we identify three objects that have displayed systematic and monotonic velocity changes by several hundred km s-1 and are prime targets for further monitoring. Because the periods of the hypothetical binaries are expected to be long, we cannot hope to observe many orbital cycles during our lifetimes. Instead, we seek to evaluate the credentials of the SBHB candidates by attempting to rule out the SBHB hypothesis. In this spirit, we present a method for placing a lower limit on the period, and thus the mass, of the SBHBs under the assumption that the velocity changes we observe are due to orbital motion. Given the duration of our monitoring campaign and the uncertainties in the radial velocities, we were able to place a lower limit on the total mass in the range 4.7 × 104-3.8 × 108 M⊙, which does not yet allow us to rule out the SBHB hypothesis for any candidates.

  4. A velocity-dependent anomalous radial transport model for (2-D, 2-V) kinetic transport codes

    NASA Astrophysics Data System (ADS)

    Bodi, Kowsik; Krasheninnikov, Sergei; Cohen, Ron; Rognlien, Tom

    2008-11-01

    Plasma turbulence constitutes a significant part of radial plasma transport in magnetically confined plasmas. This turbulent transport is modeled in the form of anomalous convection and diffusion coefficients in fluid transport codes. There is a need to model the same in continuum kinetic edge codes [such as the (2-D, 2-V) transport version of TEMPEST, NEO, and the code being developed by the Edge Simulation Laboratory] with non-Maxwellian distributions. We present an anomalous transport model with velocity-dependent convection and diffusion coefficients leading to a diagonal transport matrix similar to that used in contemporary fluid transport models (e.g., UEDGE). Also presented are results of simulations corresponding to radial transport due to long-wavelength ExB turbulence using a velocity-independent diffusion coefficient. A BGK collision model is used to enable comparison with fluid transport codes.

  5. Absolute Geostrophic Velocity Inverted from World Ocean Atlas 2013 (WOAV13) with the P-Vector Method

    DTIC Science & Technology

    2015-11-01

    The WOAV13 dataset comprises 3D global gridded climatological fields of absolute geostrophic velocity inverted...from World Ocean Atlas-2013 (WOA13) temperature and salinity fields using the P-vector method. It provides a climatological velocity field that is... climatology Dataset Identifier: gov.noaa.nodc:0121576 Creator: NOAP Lab, Department of Oceanography, Naval Postgraduate School, Monterey, CA Title

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    Context. Gaia is a space mission that is currently measuring the five astrometric parameters, as well as spectrophotometry of at least 1 billion stars to G = 20.7 mag with unprecedented precision. The sixth parameter in phase space (I.e., radial velocity) is also measured thanks to medium-resolution spectroscopy that is being obtained for the 150 million brightest stars. During the commissioning phase, two fields, one around each ecliptic pole, have been repeatedly observed to assess and to improve the overall satellite performances, as well as the associated reduction and analysis software. A ground-based photometric and spectroscopic survey was therefore initiated in 2007, and is still running to gather as much information as possible about the stars in these fields. This work is of particular interest to the validation of the radial velocity spectrometer outputs. Aims: The paper presents the radial velocity measurements performed for the Southern targets in the 12-17 R magnitude range on high- to mid-resolution spectra obtained with the GIRAFFE and UVES spectrographs. Methods: Comparison of the South Ecliptic Pole (SEP) GIRAFFE data to spectroscopic templates observed with the HERMES (Mercator in La Palma, Spain) spectrograph enabled a first coarse characterisation of the 747 SEP targets. Radial velocities were then obtained by comparing the results of three different methods. Results: In this paper, we present an initial overview of the targets to be found in the 1 sq. deg SEP region that was observed repeatedly by Gaia ever since its commissioning. In our representative sample, we identified one galaxy, six LMC S-stars, nine candidate chromospherically active stars, and confirmed the status of 18 LMC Carbon stars. A careful study of the 3471 epoch radial velocity measurements led us to identify 145 RV constant stars with radial velocities varying by less than 1 km s-1. Seventy-eight stars show significant RV scatter, while nine stars show a composite spectrum

  7. Absolute wind velocities in the lower thermosphere of Venus using infrared heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Goldstein, Jeffrey J.; Mumma, Michael J.; Kostiuk, Theodor; Deming, Drake; Espenak, Fred; Zipoy, David

    1991-01-01

    NASA's IR Telescope Facility and the McMath Solar Telescope have yielded absolute wind velocities in the Venus thermosphere for December 1985 to March 1987 with sufficient spatial resolution for circulation model discrimination. A qualitative analysis of beam-integrated winds indicates subsolar-to-antisolar circulation in the lower thermosphere; horizontal wind velocity was derived from a two-parameter model wind field of subsolar-antisolar and zonal components. A unique model fit common to all observing periods possessed 120 m/sec subsolar-antisolar and 25 m/sec zonal retrograde components, consistent with the Bougher et al. (1986, 1988) hydrodynamical models for 110 km.

  8. The symbiosis of photometry and radial-velocity measurements

    NASA Technical Reports Server (NTRS)

    Cochran, William D.

    1994-01-01

    The FRESIP mission is optimized to detect the inner planets of a planetary system. According to the current paradigm of planet formation, these planets will probably be small Earth-sized objects. Ground-based radial-velocity programs now have the sensitivity to detect Jovian-mass planets in orbit around bright solar-type stars. We expect the more massive planets to form in the outer regions of a proto-stellar nebula. These two types of measurements will very nicely complement each other, as they have highest detection probability for very different types of planets. The combination of FRESIP photometry and ground-based spectra will provide independent confirmation of the existence of planetary systems in orbit around other stars. Such detection of both terrestrial and Jovian planets in orbit around the same star is essential to test our understanding of planet formation.

  9. Radial-velocity measures and the existence of astrophysical binaries in late-type dwarf stars

    NASA Technical Reports Server (NTRS)

    Bopp, B. W.; Meredith, R.

    1986-01-01

    Radial velocities with errors of 1-2 km/s are presented based on CCD scans obtained with the Kitt Peak National Observatory coude feed telescope between 1982 and 1985 of 48 dK-M stars that lack Balmer emission. Comparison with Gliese's (1969) values shows only two stars to be spectroscopic binary candidates with small velocity amplitudes. No evidence for any short period (less than 10 days) binaries is found, supporting the conclusions of Young et al. (1986) that there are no astrophysical binaries among these chromosherically inactive dM stars.

  10. Requirements for Radial Migration: How does the migrating fraction depend on stellar velocity dispersion?

    NASA Astrophysics Data System (ADS)

    Tolfree, Kathryne; Wyse, R. F.

    2014-01-01

    Radial migration is a way to rearrange the orbital angular momentum of stars in an spiral disk without inducing kinematic heating. When radial migration is very efficient, a large fraction of disk stars experience significant changes in their orbital angular momenta in a short period of time. Such scenarios have strong implications for the chemical and kinematic evolution of disk galaxies. We have undertaken an investigation of the physical dependencies of the efficiency of radial migration on stellar kinematics and spiral structure by deriving the fraction of stars that can migrate radially given certain conditions. In order for a star in a spiral disk to migrate radially, it must first be “captured" in a family of resonant orbits near the radius of corotation with a spiral pattern. Thus far, the only analytic criterion for capture has been for stars in circular orbits. We present the capture criterion for stars on non-circular orbits in a disk galaxy. We then use our analytically derived capture criteria to model the radial distribution of the captured fraction in an exponential disk with a flat rotation curve as well as the dependence of the total captured fraction in the disk on the radial component of the stellar velocity dispersion (σR) and the amplitude of the spiral perturbation to the underlying potential at corotation (|Φs|CR). We find that the captured fraction goes as Exp[-σR2/|Φs|CR].

  11. Requirements for Radial Migration: How Does the Migrating Fraction Depend on Stellar Velocity Dispersion?

    NASA Astrophysics Data System (ADS)

    Tolfree, K. J. D.; Wyse, R. F. G.

    2014-03-01

    Radial migration is a mechanism that can rearrange the orbital angular momentum of stars in a spiral disk without inducing kinematic heating. When radial migration is very efficient, a large fraction of disk stars experience significant changes in their orbital angular momenta over a short period of time. Such scenarios have strong implications for the chemical and kinematic evolution of disk galaxies. We have undertaken an investigation of the physical dependencies of the efficiency of radial migration on stellar kinematics and spiral structure by deriving the fraction of stars that can migrate radially. In order for a star in a spiral disk to migrate radially, it must first be “captured” in a family of resonant orbits near the radius of corotation with a transient spiral pattern. To date, the only analytic criterion for capture has been for stars in circular orbits. We present the capture criterion for disk stars on non-circular orbits. We then use our analytically derived capture criterion to model the radial distribution of the captured fraction in an exponential disk with a flat rotation curve. Further, we derive the dependence of the total captured fraction in the disk on the radial component of the stellar velocity dispersion (σR) and the amplitude of the spiral perturbation to the underlying potential evaluated at corotation (|Φs|CR). We find that within an annulus centered around corotation where σR is constant, the captured fraction goes as e-σR2/|Φs|CR.

  12. KECK NIRSPEC RADIAL VELOCITY OBSERVATIONS OF LATE-M DWARFS

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

    Tanner, Angelle; White, Russel; Bailey, John

    2012-11-15

    We present the results of an infrared spectroscopic survey of 23 late-M dwarfs with the NIRSPEC echelle spectrometer on the Keck II telescope. Using telluric lines for wavelength calibration, we are able to achieve measurement precisions of down to 45 m s{sup -1} for our late-M dwarfs over a one- to four-year long baseline. Our sample contains two stars with radial velocity (RV) variations of >1000 m s{sup -1}. While we require more measurements to determine whether these RV variations are due to unseen planetary or stellar companions or are the result of starspots known to plague the surface ofmore » M dwarfs, we can place upper limits of <40 M{sub J} sin i on the masses of any companions around those two M dwarfs with RV variations of <160 m s{sup -1} at orbital periods of 10-100 days. We have also measured the rotational velocities for all the stars in our late-M dwarf sample and offer our multi-order, high-resolution spectra over 2.0-2.4 {mu}m to the atmospheric modeling community to better understand the atmospheres of late-M dwarfs.« less

  13. New scramblers for precision radial velocity: square and octagonal fibers

    NASA Astrophysics Data System (ADS)

    Chazelas, Bruno; Pepe, Francesco; Wildi, François; Bouchy, Francois; Perruchot, Sandrine; Avila, Gerardo

    2010-07-01

    One of the remaining limitation of the precise radial velocity instruments is the imperfect scrambling produced by the circular fibers. We present here experimental studies on new optical fibers aiming at an improvement of the scrambling they provide. New fibers shapes were tested: square and octagonal. Measurements have been performed of the scrambling performances of these fibers in the near field as well FRD measurements. These fibers show extremely promising performances in the near field scrambling: an improvement of a factor 5 to 10 compared to the circular fiber. They however show some strange behavior in the far field that need to be understood.

  14. VizieR Online Data Catalog: WOCS. LXVI. Radial velocity survey in M35 (Leiner+, 2015)

    NASA Astrophysics Data System (ADS)

    Leiner, E. M.; Mathieu, R. D.; Gosnell, N. M.; Geller, A. M.

    2015-09-01

    In this second paper (see also Geller et al. 2010, cat. J/AJ/139/1383) in a series studying the dynamical state of the young (150Myr) open cluster M35 we present an updated version of our complete radial velocity database for the cluster. Our sample is selected to cover the range of the M35 main sequence from 0.8 to 1.6Mȯ out to 30' from cluster center. In the 17 years that we have observed M35, we have gathered ~8000 moderate-precision (σi=0.5km/s) spectra of ~1300 stars. We find 418 of these to be confirmed radial velocity cluster members or likely members. Within our sample of 418 cluster members or likely members, we detect 64 velocity-variable stars. We present orbital solutions for 52 (see Tables 5 and 7) of these 64 systems, in addition to 28 (see Tables 6 and 8) completed orbital solutions for non-member binaries in our field of view. The binaries are drawn from a sample initially derived from the photometry of T. von Hippel taken at KPNO on the Burrell Schmidt telescope. Observations were taken on 1993 November 18-19, and include B and V photometry down to a magnitude of V=17 lying within a 70'*70' field of view. Subsequently, we updated this photometry for 74% of our sources with more precise BV photometry from C. P. Deliyannis (2006, private communication; Sarrazine et al., 2000AAS...197.4107S). This new photometry was taken on the WIYN 0.9m telescope with the S2KB imager and covers a 40'*40' field of view. See Geller et al. 2010 (cat. J/AJ/139/1383) for more information on these two sets of photometry. Beginning in 1997 September, we have obtained spectra for the stars in our sample at the WIYN 3.5m telescope at KPNO using the Hydra Multi-Object Spectrograph (MOS). For a detailed description of our observing and data reduction procedure see Geller et al. 2008 (cat. J/AJ/135/2264). In short, we typically use Hydra's blue sensitive fibers and an echelle grating providing a resolution of R~20000. These spectra are centered on 512.5nm, and span a ~25nm

  15. Lyman-Alpha Observations of High Radial Velocity Stars

    NASA Astrophysics Data System (ADS)

    Bookbinder, Jay

    1990-12-01

    H I LYMAN -ALPHA (LY-A) IS ONE OF THE MOST IMPORTANT LINES EMITTED BY PLASMA IN THE TEMPERATURE RANGE OF 7000 TO 10 TO THE FIFTH POWER K IN LATE-TYPE STARS. IT IS A MAJOR COMPONENT OF THE TOTAL RADIATIVE LOSS RATE, AND IT PLAYS A CRUCIAL ROLE IN DETERMINING THE ATMOSPHERIC STRUCTURE AND IN FLUORESCING OTHER UV LINES. YET IT IS ALSO THE LEAST STUDIED MAJOR LINE IN THE FAR UV, BECAUSE MOST OF THE LINE FLUX IS ABSORBED BY THE ISM ALONG THE LINE OF SIGHT AND BECAUSE IT IS STRONGLY COMTAMINATED BY THE GEOCORONAL BACKGROUND. A KNOWLEDGE OF THE Ly-A PROFILE IS ALSO IMPORTANT FOR STUDIES OF DEUTERIUM IN THE INTERSTELLAR MEDIUM. BY OBSERVING HIGH RADIAL VELOCITY STARS WE WILL OBTAIN FOR THE FIRST TIME HIGH RESOLUTION SPECTRA OF THE CORE OF A STELLAR H I LYMAN-A EMISSION LINE PROFILE.

  16. Origins of Solar Systems: Removing Activity-Related Radial Velocity Noise to Improve Extrasolar Planet Searches

    NASA Technical Reports Server (NTRS)

    Saar, Steven; Lindstrom, David (Technical Monitor)

    2003-01-01

    We have continued the super high resolution (R is approximately 200,000), high S/N (> 300) echelle study of joint line bisector and radial velocity variations using the McDonald 2-D coude. A long observing run in October 2002 was quite successful (8 clear nights). We now have close to three years of data, which begins to sample a good fraction of the magnetic cycle timescales for some of our targets (e.g., K Ceti; P(sub cyc)=5.6 yrs). This will be very helpful in unraveling the complex relationships between plage and v(sub r), changes which we have uncovered. A preliminary analysis of the limited data in hand, and find some tantalizing evidence for correlations between median line bisector displacement and radial velocity v(sub r). The correlation appears to be specific to the particular star being considered, probably since it is a function of both spectral type and rotation rate. Additional information regarding progress on the grant is included.

  17. Radial Velocities and Space Motions for nearby Stars

    NASA Astrophysics Data System (ADS)

    Upgren, A. R.; Sperauskas, J.

    2005-10-01

    The McCormick lists of stars and the Fourth Edition of the Catalog of Nearby Stars (CNS4) complement each other. Together they can be used to evaluate sources of systematic error in either of them. In addition to the 900 McCormick dwarf K-M stars brighter than about 11.5, the CNS4 includes all similar dwarfs believed to be within 25 parsecs of the Sun that appear to be missed in the former source. All of the stars from both sources are known to have precise trigonometric parallaxes, proper motions and, of course, positions. At the Moletai Observatory and elsewhere, radial velocities mostly to± 1 km/sec are almost complete for these dwarf stars. The goal is to have a sample of some 1200 dwarf stars with spatial coordinates and their first time derivatives for which the Lutz-Kelker and Malmquist corrections can be evaluated. Hopefully, age-related stellar measures will also be provided in a later phase of the program.

  18. First Absolutely Calibrated Localized Measurements of Ion Velocity in the MST in Locked and Rotating Plasmas

    NASA Astrophysics Data System (ADS)

    Baltzer, M.; Craig, D.; den Hartog, D. J.; Nornberg, M. D.; Munaretto, S.

    2015-11-01

    An Ion Doppler Spectrometer (IDS) is used on MST for high time-resolution passive and active measurements of impurity ion emission. Absolutely calibrated measurements of flow are difficult because the spectrometer records data within 0.3 nm of the C+5 line of interest, and commercial calibration lamps do not produce lines in this narrow range . A novel optical system was designed to absolutely calibrate the IDS. The device uses an UV LED to produce a broad emission curve in the desired region. A Fabry-Perot etalon filters this light, cutting transmittance peaks into the pattern of the LED emission. An optical train of fused silica lenses focuses the light into the IDS with f/4. A holographic diffuser blurs the light cone to increase homogeneity. Using this light source, the absolute Doppler shift of ion emissions can be measured in MST plasmas. In combination with charge exchange recombination spectroscopy, localized ion velocities can now be measured. Previously, a time-averaged measurement along the chord bisecting the poloidal plane was used to calibrate the IDS; the quality of these central chord calibrations can be characterized with our absolute calibration. Calibration errors may also be quantified and minimized by optimizing the curve-fitting process. Preliminary measurements of toroidal velocity in locked and rotating plasmas will be shown. This work has been supported by the US DOE.

  19. Shear wave velocity and radial anisotropy beneath the Wyoming craton: craton destruction and lithospheric layering

    NASA Astrophysics Data System (ADS)

    Dave, R.; Li, A.

    2016-12-01

    The Wyoming craton has evolved under an intriguing geological history with suture zones, accreted margins, flat-slab subduction, orogeny and an encroaching hotspot. Whether and how the cratonic root has been widely destroyed by the series of tectonic events remain controversial. Aiming to address these questions using a craton-wide model, we have analyzed Rayleigh and Love wave data from 75 earthquakes recorded by 103 USArray TA stations in the Wyoming craton. 2-D phase velocity maps are constructed for 18 periods from 20 s to 166 s using the two-plane-wave tomography. The Yellowstone hotspot and the Cheyenne belt are characterized by low velocity anomalies at all periods in both Rayleigh and Love wave models. The northern craton in Montana is broadly fast at periods < 70 s and is relatively slow at longer periods, suggesting a shallower lithosphere. The fast anomaly in Wyoming has a NE-SW trend and extends to more than 200 km in the VSV model. However, such a fast anomaly is largely absent in the Love wave images at long periods. The association of VSV>VSH with this deep fast anomaly indicates mantle downwelling beneath south-central Wyoming. Mantle upwelling likely happens in slow regions at the hotspot, the Cheyenne belt, and the northeastern craton. The overall pattern of velocity anomaly and radial anisotropy suggests that small-scale mantle convection is vigorously acting beneath the Wyoming craton and continuously destructing the cratonic lithosphere. In addition, the average VSV and VSH models show a strong positive radial anisotropy of 5% (VSH>VSV) above 100 km and a weak negative anisotropy (VSV>VSH) below 120 km. Such a significant change in radial anisotropy could contribute to the observed mid-lithosphere discontinuity (MLD) from receiver functions. Both VSV and VSH reveal a fast lid above 100 km and a large velocity reduction at the depths of 115-190 km, corresponding with a lithosphere-asthenosphere boundary (LAB) at 150 km. These observations

  20. Current Global Absolute Plate Velocities Inferred from the Trends of Hotspot Tracks: Implications for Motion between Groups of Hotspots and Comparison and Combination with Absolute Velocities Inferred from the Orientation of Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Wang, C.; Gordon, R. G.; Zheng, L.

    2016-12-01

    Hotspot tracks are widely used to estimate the absolute velocities of plates, i.e., relative to the lower mantle. Knowledge of current motion between hotspots is important for both plate kinematics and mantle dynamics and informs the discussion on the origin of the Hawaiian-Emperor Bend. Following Morgan & Morgan (2007), we focus only on the trends of young hotspot tracks and omit volcanic propagation rates. The dispersion of the trends can be partitioned into between-plate and within-plate dispersion. Applying the method of Gripp & Gordon (2002) to the hotspot trend data set of Morgan & Morgan (2007) constrained to the MORVEL relative plate angular velocities (DeMets et al., 2010) results in a standard deviation of the 56 hotspot trends of 22°. The largest angular misfits tend to occur on the slowest moving plates. Alternatively, estimation of best-fitting poles to hotspot tracks on the nine individual plates, results in a standard deviation of trends of only 13°, a statistically significant reduction from the introduction of 15 additional adjustable parameters. If all of the between-plate misfit is due to motion of groups of hotspots (beneath different plates), nominal velocities relative to the mean hotspot reference frame range from 1 to 4 mm/yr with the lower bounds ranging from 1 to 3 mm/yr and the greatest upper bound being 8 mm/yr. These are consistent with bounds on motion between Pacific and Indo-Atlantic hotspots over the past ≈50 Ma, which range from zero (lower bound) to 8 to 13 mm/yr (upper bounds) (Koivisto et al., 2014). We also determine HS4-MORVEL, a new global set of plate angular velocities relative to the hotspots constrained to consistency with the MORVEL relative plate angular velocities, using a two-tier analysis similar to that used by Zheng et al. (2014) to estimate the SKS-MORVEL global set of absolute plate velocities fit to the orientation of seismic anisotropy. We find that the 95% confidence limits of HS4-MORVEL and SKS

  1. A California statewide three-dimensional seismic velocity model from both absolute and differential times

    USGS Publications Warehouse

    Lin, G.; Thurber, C.H.; Zhang, H.; Hauksson, E.; Shearer, P.M.; Waldhauser, F.; Brocher, T.M.; Hardebeck, J.

    2010-01-01

    We obtain a seismic velocity model of the California crust and uppermost mantle using a regional-scale double-difference tomography algorithm. We begin by using absolute arrival-time picks to solve for a coarse three-dimensional (3D) P velocity (VP) model with a uniform 30 km horizontal node spacing, which we then use as the starting model for a finer-scale inversion using double-difference tomography applied to absolute and differential pick times. For computational reasons, we split the state into 5 subregions with a grid spacing of 10 to 20 km and assemble our final statewide VP model by stitching together these local models. We also solve for a statewide S-wave model using S picks from both the Southern California Seismic Network and USArray, assuming a starting model based on the VP results and a VP=VS ratio of 1.732. Our new model has improved areal coverage compared with previous models, extending 570 km in the SW-NE directionand 1320 km in the NW-SE direction. It also extends to greater depth due to the inclusion of substantial data at large epicentral distances. Our VP model generally agrees with previous separate regional models for northern and southern California, but we also observe some new features, such as high-velocity anomalies at shallow depths in the Klamath Mountains and Mount Shasta area, somewhat slow velocities in the northern Coast Ranges, and slow anomalies beneath the Sierra Nevada at midcrustal and greater depths. This model can be applied to a variety of regional-scale studies in California, such as developing a unified statewide earthquake location catalog and performing regional waveform modeling.

  2. High precision radial velocities with GIANO spectra

    NASA Astrophysics Data System (ADS)

    Carleo, I.; Sanna, N.; Gratton, R.; Benatti, S.; Bonavita, M.; Oliva, E.; Origlia, L.; Desidera, S.; Claudi, R.; Sissa, E.

    2016-06-01

    Radial velocities (RV) measured from near-infrared (NIR) spectra are a potentially excellent tool to search for extrasolar planets around cool or active stars. High resolution infrared (IR) spectrographs now available are reaching the high precision of visible instruments, with a constant improvement over time. GIANO is an infrared echelle spectrograph at the Telescopio Nazionale Galileo (TNG) and it is a powerful tool to provide high resolution spectra for accurate RV measurements of exoplanets and for chemical and dynamical studies of stellar or extragalactic objects. No other high spectral resolution IR instrument has GIANO's capability to cover the entire NIR wavelength range (0.95-2.45 μm) in a single exposure. In this paper we describe the ensemble of procedures that we have developed to measure high precision RVs on GIANO spectra acquired during the Science Verification (SV) run, using the telluric lines as wavelength reference. We used the Cross Correlation Function (CCF) method to determine the velocity for both the star and the telluric lines. For this purpose, we constructed two suitable digital masks that include about 2000 stellar lines, and a similar number of telluric lines. The method is applied to various targets with different spectral type, from K2V to M8 stars. We reached different precisions mainly depending on the H-magnitudes: for H ˜ 5 we obtain an rms scatter of ˜ 10 m s-1, while for H ˜ 9 the standard deviation increases to ˜ 50 ÷ 80 m s-1. The corresponding theoretical error expectations are ˜ 4 m s-1 and 30 m s-1, respectively. Finally we provide the RVs measured with our procedure for the targets observed during GIANO Science Verification.

  3. A Low-cost Environmental Control System for Precise Radial Velocity Spectrometers

    NASA Astrophysics Data System (ADS)

    Sliski, David H.; Blake, Cullen H.; Halverson, Samuel

    2017-12-01

    We present an environmental control system (ECS) designed to achieve milliKelvin (mK) level temperature stability for small-scale astronomical instruments. This ECS is inexpensive and is primarily built from commercially available components. The primary application for our ECS is the high-precision Doppler spectrometer MINERVA-Red, where the thermal variations of the optical components within the instrument represent a major source of systematic error. We demonstrate ±2 mK temperature stability within a 0.5 m3 thermal enclosure using resistive heaters in conjunction with a commercially available PID controller and off-the-shelf thermal sensors. The enclosure is maintained above ambient temperature, enabling rapid cooling through heat dissipation into the surrounding environment. We demonstrate peak-to-valley (PV) temperature stability of better than 5 mK within the MINERVA-Red vacuum chamber, which is located inside the thermal enclosure, despite large temperature swings in the ambient laboratory environment. During periods of stable laboratory conditions, the PV variations within the vacuum chamber are less than 3 mK. This temperature stability is comparable to the best stability demonstrated for Doppler spectrometers currently achieving m s-1 radial velocity precision. We discuss the challenges of using commercially available thermoelectrically cooled CCD cameras in a temperature-stabilized environment, and demonstrate that the effects of variable heat output from the CCD camera body can be mitigated using PID-controlled chilled water systems. The ECS presented here could potentially provide the stable operating environment required for future compact “astrophotonic” precise radial velocity (PRV) spectrometers to achieve high Doppler measurement precision with a modest budget.

  4. The Joker: A Custom Monte Carlo Sampler for Binary-star and Exoplanet Radial Velocity Data

    NASA Astrophysics Data System (ADS)

    Price-Whelan, Adrian M.; Hogg, David W.; Foreman-Mackey, Daniel; Rix, Hans-Walter

    2017-03-01

    Given sparse or low-quality radial velocity measurements of a star, there are often many qualitatively different stellar or exoplanet companion orbit models that are consistent with the data. The consequent multimodality of the likelihood function leads to extremely challenging search, optimization, and Markov chain Monte Carlo (MCMC) posterior sampling over the orbital parameters. Here we create a custom Monte Carlo sampler for sparse or noisy radial velocity measurements of two-body systems that can produce posterior samples for orbital parameters even when the likelihood function is poorly behaved. The six standard orbital parameters for a binary system can be split into four nonlinear parameters (period, eccentricity, argument of pericenter, phase) and two linear parameters (velocity amplitude, barycenter velocity). We capitalize on this by building a sampling method in which we densely sample the prior probability density function (pdf) in the nonlinear parameters and perform rejection sampling using a likelihood function marginalized over the linear parameters. With sparse or uninformative data, the sampling obtained by this rejection sampling is generally multimodal and dense. With informative data, the sampling becomes effectively unimodal but too sparse: in these cases we follow the rejection sampling with standard MCMC. The method produces correct samplings in orbital parameters for data that include as few as three epochs. The Joker can therefore be used to produce proper samplings of multimodal pdfs, which are still informative and can be used in hierarchical (population) modeling. We give some examples that show how the posterior pdf depends sensitively on the number and time coverage of the observations and their uncertainties.

  5. VizieR Online Data Catalog: Radial velocities in M67. I. 1278 candidate members (Geller+, 2015)

    NASA Astrophysics Data System (ADS)

    Geller, A. M.; Latham, D. W.; Mathieu, R. D.

    2015-10-01

    This is the first in a series of papers studying the dynamical state of the old open cluster M67 through precise radial velocities. This is also the paper LXVII of the WIYN Open Cluster Study. Our radial velocity survey of M67 began as part of the dissertation work of Mathieu (1983PhDT.........8M), taking advantage of the CfA Digital Speedometers (DS). Three nearly identical instruments were used, initially on the MMT (from HJD2445337 to HJD2450830) and 1.5m Tillinghast Reflector (from HJD2444184 to HJD2454958) at the Fred Lawrence Whipple Observatory on Mount Hopins, Arizona, and then later on the 1.5m Wyeth Reflector (from HJD2445722 to HJD2453433) at the Oak Ridge Observatory in the Town of Harvard, Massachusetts. Subsequently the M67 target samples were expanded several times. Radial velocities measurements from other programs were integrated into the database, and our observational facilities were extended to include Hydra Multi-Object Spectrograph (MOS) at the WIYN Observatory (from HJD2453386 to HJD2456709) and the new Tillinghast Reflector Echelle Spectrograph (TRES) on the Tillinghast Reflector (from HJD2455143 to HJD2456801). Details about the telescopes, observing procedures, and data reductions of spectra obtained with the CfA DS can be found in Latham (1985srv..conf...21L, 1992ASPC...32..110L). The corresponding information for spectra obtained with Hydra at the WIYN Observatory can be found in Geller et al. 2008 (cat. J/AJ/135/2264), Geller et al. 2010 (cat. J/AJ/139/1383) and Hole et al. (2009). TRES is a stabilized fiber-fed echelle spectrograph with a CCD detector and resolution of 44000. The initial CfA sample was defined in 1982. The last surviving CfA Digital Speedometer, on the 1.5m Tillinghast Reflector, was retired in the summer of 2009. Over the following five observing seasons, TRES was used to continue the radial velocity observations of targets (mostly binaries) from both the CfA and the WIYN samples. Importantly, Roger Griffin and James

  6. Absolute Properties of the Eclipsing Binary Star BF Draconis

    NASA Astrophysics Data System (ADS)

    Lacy, Claud H. Sandberg; Torres, Guillermo; Fekel, Francis C.; Sabby, Jeffrey A.; Claret, Antonio

    2012-06-01

    BF Dra is now known to be an eccentric double-lined F6+F6 binary star with relatively deep (0.7 mag) partial eclipses. Previous studies of the system are improved with 7494 differential photometric observations from the URSA WebScope and 9700 from the NFO WebScope, 106 high-resolution spectroscopic observations from the Tennessee State University 2 m automatic spectroscopic telescope and the 1 m coudé-feed spectrometer at Kitt Peak National Observatory, and 31 accurate radial velocities from the CfA. Very accurate (better than 0.6%) masses and radii are determined from analysis of the two new light curves and four radial velocity curves. Theoretical models match the absolute properties of the stars at an age of about 2.72 Gyr and [Fe/H] = -0.17, and tidal theory correctly confirms that the orbit should still be eccentric. Our observations of BF Dra constrain the convective core overshooting parameter to be larger than about 0.13 Hp . We find, however, that standard tidal theory is unable to match the observed slow rotation rates of the components' surface layers.

  7. A Refined Radial Velocity Curve for the L Dwarf Donor of WZ Sagittae

    NASA Astrophysics Data System (ADS)

    Harrison, Thomas E.

    2017-12-01

    We have obtained a radial velocity curve for the L dwarf donor in WZ Sagittae using phase-resolved J-band spectra obtained with GNIRS on Gemini-north. We find a radial velocity semi-amplitude of {K}2=525+/- 11 {km} {{{s}}}-1. This result reduces the error bar by a factor of three over previous attempts. A relatively strong, unidentified emission line centered near 1.177 μm, corrupts the blue K i doublet in these data. While an H i emission feature near 1.2527 μm distorts the depth of the red K i doublet. In addition, a weak H i emission line at 1.1969 μm falls in the middle of the strongest FeH feature in these spectra. The combination of these contaminants prevents us from precisely constraining the spectral type of the donor. The strength of the absorption features remains consistent with an early L spectral type. Based on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), and Ministério da Ciência, Tecnologia e Inovação (Brazil).

  8. METALLICITY DISTRIBUTION FUNCTIONS, RADIAL VELOCITIES, AND ALPHA ELEMENT ABUNDANCES IN THREE OFF-AXIS BULGE FIELDS

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

    Johnson, Christian I.; Rich, R. Michael; Kobayashi, Chiaki

    2013-03-10

    We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe], [Si/Fe], and [Ca/Fe] for 264 red giant branch stars in three Galactic bulge off-axis fields located near (l, b) = (-5.5, -7), (-4, -9), and (+8.5, +9). The results are based on equivalent width and spectrum synthesis analyses of moderate resolution (R Almost-Equal-To 18,000), high signal-to-noise ratio (S/N {approx} 75-300 pixel{sup -1}) spectra obtained with the Hydra spectrographs on the Blanco 4 m and WIYN 3.5 m telescopes. The targets were selected from the blue side of the giant branch to avoid cool stars that would be strongly affectedmore » by CN and TiO; however, a comparison of the color-metallicity distribution in literature samples suggests that our selection of bluer targets should not present a significant bias against metal-rich stars. We find a full range in metallicity that spans [Fe/H] Almost-Equal-To -1.5 to +0.5, and that, in accordance with the previously observed minor-axis vertical metallicity gradient, the median [Fe/H] also declines with increasing Galactic latitude in off-axis fields. The off-axis vertical [Fe/H] gradient in the southern bulge is estimated to be {approx}0.4 dex kpc{sup -1}; however, comparison with the minor-axis data suggests that a strong radial gradient does not exist. The (+8.5, +9) field exhibits a higher than expected metallicity, with a median [Fe/H] = -0.23, that might be related to a stronger presence of the X-shaped bulge structure along that line-of-sight. This could also be the cause of an anomalous increase in the median radial velocity for intermediate metallicity stars in the (+8.5, +9) field. However, the overall radial velocity and dispersion for each field are in good agreement with recent surveys and bulge models. All fields exhibit an identical, strong decrease in velocity dispersion with increasing metallicity that is consistent with observations in similar minor-axis outer bulge fields. Additionally, the [O/Fe], [Si

  9. Searching for Radial Velocity Variations in eta Carinae

    NASA Technical Reports Server (NTRS)

    Iping, R. C.; Sonneborn, G.; Gull, T. R.; Ivarsson, S.; Nielsen, K.

    2006-01-01

    A hot companion of eta Carinae has been detected using high resolution spectra (905 - 1180 A) obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite (see poster by Sonneborn et al.). Analysis of the far-UV spectrum shows that eta Car B is a luminous hot star. The N II 1084-86 emission feature indicates that the star may be nitrogen rich. The FUV continuum and the S IV 1073 P-Cygni wind line suggest that the effective temperature of eta Car B is at least 25,000 K. FUV spectra of eta Carinae were obtained with the FUSE satellite at 9 epochs between 2000 February and 2005 July. The data consists of 12 observations taken with the LWRS aperture (30x30 arcsec), three with the HIRS aperture (1.25x20 arcsec), and one MRDS aperture (4x20 arcsec). In this paper we discuss the analysis of these spectra to search for radial velocity variations associated with the 5.54-year binary orbit of Eta Car AB.

  10. Magnetic field and radial velocities of the star Chi Draconis A

    NASA Astrophysics Data System (ADS)

    Lee, Byeong-Cheol; Gadelshin, D.; Han, Inwoo; Kang, Dong-Il; Kim, Kang-Min; Valyavin, G.; Galazutdinov, G.; Jeong, Gwanghui; Beskrovnaya, N.; Burlakova, T.; Grauzhanina, A.; Ikhsanov, N. R.; Kholtygin, A. F.; Valeev, A.; Bychkov, V.; Park, Myeong-Gu

    2018-01-01

    We present high-resolution spectropolarimetric observations of the spectroscopic binary χ Dra. Spectral lines in the spectrum of the main component χ Dra A show variable Zeeman displacement, which confirms earlier suggestions about the presence of a weak magnetic field on the surface of this star. Within about 2 yr of time base of our observations, the longitudinal component BL of the magnetic field exhibits variation from -11.5 ± 2.5 to +11.1 ± 2.1 G with a period of about 23 d. Considering the rotational velocity of χ Dra A in the literature and that newly measured in this work, this variability may be explained by the stellar rotation under the assumption that the magnetic field is globally stable. Our new measurements of the radial velocities (RV) in high-resolution I-spectra of χ Dra A refined the orbital parameters and reveal persistent deviations of RVs from the orbital curve. We suspect that these deviations may be due to the influence of local magnetically generated spots, pulsations, or a Jupiter-size planet orbiting the system.

  11. SOAP. A tool for the fast computation of photometry and radial velocity induced by stellar spots

    NASA Astrophysics Data System (ADS)

    Boisse, I.; Bonfils, X.; Santos, N. C.

    2012-09-01

    We define and put at the disposal of the community SOAP, Spot Oscillation And Planet, a software tool that simulates the effect of stellar spots and plages on radial velocimetry and photometry. This paper describes the tool release and provides instructions for its use. We present detailed tests with previous computations and real data to assess the code's performance and to validate its suitability. We characterize the variations of the radial velocity, line bisector, and photometric amplitude as a function of the main variables: projected stellar rotational velocity, filling factor of the spot, resolution of the spectrograph, linear limb-darkening coefficient, latitude of the spot, and inclination of the star. Finally, we model the spot distributions on the active stars HD 166435, TW Hya and HD 189733, which reproduce the observations. We show that the software is remarkably fast, allowing several evolutions in its capabilities that could be performed to study the next challenges in the exoplanetary field connected with the stellar variability. The tool is available at http://www.astro.up.pt/soap

  12. The catalogue of radial velocity variable hot subluminous stars from the MUCHFUSS project

    NASA Astrophysics Data System (ADS)

    Geier, S.; Kupfer, T.; Heber, U.; Schaffenroth, V.; Barlow, B. N.; Østensen, R. H.; O'Toole, S. J.; Ziegerer, E.; Heuser, C.; Maxted, P. F. L.; Gänsicke, B. T.; Marsh, T. R.; Napiwotzki, R.; Brünner, P.; Schindewolf, M.; Niederhofer, F.

    2015-05-01

    The project Massive Unseen Companions to Hot Faint Underluminous Stars from SDSS (MUCHFUSS) aims to find sdBs with compact companions such as massive white dwarfs, neutron stars, or black holes. Here we provide classifications, atmospheric parameters, and a complete radial velocity (RV) catalogue containing 1914 single measurements for a sample of 177 hot subluminous stars discovered based on SDSS DR7; 110 stars show significant RV variability, while 67 qualify as candidates. We constrain the fraction of close massive compact companions of hydrogen-rich hot subdwarfs in our sample to be smaller than ~1.3%, which is already close to the theoretical predictions. However, the sample might still contain such binaries with longer periods exceeding ~8 d. We detect a mismatch between the ΔRVmax-distribution of the sdB and the more evolved sdOB and sdO stars, which challenges our understanding of their evolutionary connection. Furthermore, irregular RV variations of unknown origin with amplitudes of up to ~180 km s-1 on timescales of years, days, and even hours have been detected in some He-sdO stars. They might be connected to irregular photometric variations in some cases. The radial velocity table is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/577/A26

  13. No Evidence for Activity Correlations in the Radial Velocities of Kapteyn’s Star

    NASA Astrophysics Data System (ADS)

    Anglada-Escudé, G.; Tuomi, M.; Arriagada, P.; Zechmeister, M.; Jenkins, J. S.; Ofir, A.; Dreizler, S.; Gerlach, E.; Marvin, C. J.; Reiners, A.; Jeffers, S. V.; Butler, R. Paul; Vogt, S. S.; Amado, P. J.; Rodríguez-López, C.; Berdiñas, Z. M.; Morin, J.; Crane, J. D.; Shectman, S. A.; Díaz, M. R.; Sarmiento, L. F.; Jones, H. R. A.

    2016-10-01

    Stellar activity may induce Doppler variability at the level of a few m s-1 which can then be confused by the Doppler signal of an exoplanet orbiting the star. To first order, linear correlations between radial velocity measurements and activity indices have been proposed to account for any such correlation. The likely presence of two super-Earths orbiting Kapteyn’s star was reported in Anglada-Escudé et al., but this claim was recently challenged by Robertson et al., who argued for evidence of a rotation period (143 days) at three times the orbital period of one of the proposed planets (Kapteyn’s b, P = 48.6 days) and the existence of strong linear correlations between its Doppler signal and activity data. By re-analyzing the data using global statistics and model comparison, we show that such a claim is incorrect given that (1) the choice of a rotation period at 143 days is unjustified, and (2) the presence of linear correlations is not supported by the data. We conclude that the radial velocity signals of Kapteyn’s star remain more simply explained by the presence of two super-Earth candidates orbiting it. We note that analysis of time series of activity indices must be executed with the same care as Doppler time series. We also advocate for the use of global optimization procedures and objective arguments, instead of claims based on residual analyses which are prone to biases and incorrect interpretations.

  14. Time Variations of the Radial Velocity of H2O Masers in the Semi-Regular Variable R Crt

    NASA Astrophysics Data System (ADS)

    Sudou, Hiroshi; Shiga, Motoki; Omodaka, Toshihiro; Nakai, Chihiro; Ueda, Kazuki; Takaba, Hiroshi

    2017-12-01

    H2O maser emission {at 22 GHz} in the circumstellar envelope is one of the good tracers of detailed physics and inematics in the mass loss process of asymptotic giant branch stars. Long-term monitoring of an H2O maser spectrum with high time resolution enables us to clarify acceleration processes of the expanding shell in the stellar atmosphere. We monitored the H2O maser emission of the semi-regular variable R Crt with the Kagoshima 6-m telescope, and obtained a large data set of over 180 maser spectra over a period of 1.3 years with an observational span of a few days. Using an automatic peak detection method based on least-squares fitting, we exhaustively detected peaks as significant velocity components with the radial velocity on a 0.1 km s^{-1} scale. This analysis result shows that the radial velocity of red-shifted and blue-shifted components exhibits a change between acceleration and deceleration on the time scale of a few hundred days. These velocity variations are likely to correlate with intensity variations, in particular during flaring state of H2O masers. It seems reasonable to consider that the velocity variation of the maser source is caused by shock propagation in the envelope due to stellar pulsation.However, it is difficult to explain the relationship between the velocity variation and the intensity variation only from shock propagation effects. We found that a time delay of the integrated maser intensity with respect to the optical light curve is about 150 days.

  15. The white dwarf binary pathways survey - II. Radial velocities of 1453 FGK stars with white dwarf companions from LAMOST DR 4

    NASA Astrophysics Data System (ADS)

    Rebassa-Mansergas, A.; Ren, J. J.; Irawati, P.; García-Berro, E.; Parsons, S. G.; Schreiber, M. R.; Gänsicke, B. T.; Rodríguez-Gil, P.; Liu, X.; Manser, C.; Nevado, S. P.; Jiménez-Ibarra, F.; Costero, R.; Echevarría, J.; Michel, R.; Zorotovic, M.; Hollands, M.; Han, Z.; Luo, A.; Villaver, E.; Kong, X.

    2017-12-01

    We present the second paper of a series of publications aiming at obtaining a better understanding regarding the nature of type Ia supernovae (SN Ia) progenitors by studying a large sample of detached F, G and K main-sequence stars in close orbits with white dwarf companions (i.e. WD+FGK binaries). We employ the Large Sky Area Multi-Object Fibre Spectroscopic Telescope (LAMOST) data release 4 spectroscopic data base together with Galaxy Evolution Explorer (GALEX) ultraviolet fluxes to identify 1549 WD+FGK binary candidates (1057 of which are new), thus doubling the number of known sources. We measure the radial velocities of 1453 of these binaries from the available LAMOST spectra and/or from spectra obtained by us at a wide variety of different telescopes around the globe. The analysis of the radial velocity data allows us to identify 24 systems displaying more than 3σ radial velocity variation that we classify as close binaries. We also discuss the fraction of close binaries among WD+FGK systems, which we find to be ∼10 per cent, and demonstrate that high-resolution spectroscopy is required to efficiently identify double-degenerate SN Ia progenitor candidates.

  16. The New Absolute Parameters of OU Gem - The Star of BY Dra Type

    NASA Astrophysics Data System (ADS)

    Mishenina, T. V.; Glazunova, L. V.; Soubiran, C.; Kovtyukh, V. V.

    2010-12-01

    The spectra of OU Gem were obtained with the fiber-fed echelle spectrograph SOPHIE at the 1.93-m telescope of the Observatoire de Haute- Provence (France). The temperatures of components of the system were defined and are equal to 5013 ± 15 K and 4486±50 K for primary (A) and secondary (B) components, accordingly. The rotation velocity of components are measured: for primary component it is equal to 5.1±1 km/s and 6.2 ± km/s for the secondary one. The definition of radial velocities of components by LSD profile method and redetermination of spectral orbital elements were carried out. New absolute parameters of components were obtained too.

  17. Globular Clusters: Absolute Proper Motions and Galactic Orbits

    NASA Astrophysics Data System (ADS)

    Chemel, A. A.; Glushkova, E. V.; Dambis, A. K.; Rastorguev, A. S.; Yalyalieva, L. N.; Klinichev, A. D.

    2018-04-01

    We cross-match objects from several different astronomical catalogs to determine the absolute proper motions of stars within the 30-arcmin radius fields of 115 Milky-Way globular clusters with the accuracy of 1-2 mas yr-1. The proper motions are based on positional data recovered from the USNO-B1, 2MASS, URAT1, ALLWISE, UCAC5, and Gaia DR1 surveys with up to ten positions spanning an epoch difference of up to about 65 years, and reduced to Gaia DR1 TGAS frame using UCAC5 as the reference catalog. Cluster members are photometrically identified by selecting horizontal- and red-giant branch stars on color-magnitude diagrams, and the mean absolute proper motions of the clusters with a typical formal error of about 0.4 mas yr-1 are computed by averaging the proper motions of selected members. The inferred absolute proper motions of clusters are combined with available radial-velocity data and heliocentric distance estimates to compute the cluster orbits in terms of the Galactic potential models based on Miyamoto and Nagai disk, Hernquist spheroid, and modified isothermal dark-matter halo (axisymmetric model without a bar) and the same model + rotating Ferre's bar (non-axisymmetric). Five distant clusters have higher-than-escape velocities, most likely due to large errors of computed transversal velocities, whereas the computed orbits of all other clusters remain bound to the Galaxy. Unlike previously published results, we find the bar to affect substantially the orbits of most of the clusters, even those at large Galactocentric distances, bringing appreciable chaotization, especially in the portions of the orbits close to the Galactic center, and stretching out the orbits of some of the thick-disk clusters.

  18. Orbital Solutions and Absolute Elements of the Eclipsing Binary YY Ceti

    NASA Astrophysics Data System (ADS)

    Williamon, Richard M.; Sowell, James R.

    2012-05-01

    YY Cet is a 10.5 mag semidetached variable with a 19 hr orbital period. The Wilson-Devinney program is used to simultaneously solve two new sets of UBV light curves together with preexisting photometry and single-line radial velocity measurements . The system has the lower-mass component completely filling its Roche lobe. The resulting masses are M1 = 1.78 ± 0.19 M⊙ and M2 = 0.92 ± 0.10 M⊙, and the radii are R1 = 2.08 ± 0.08 R⊙ and R2 = 1.62 ± 0.06 R⊙. Its computed distance is 534 ± 28 pc. Light- and velocity-curve parameters, orbital elements, and absolute dimensions are presented. A study of published TOM observations indicates that the period changed around 1999.

  19. Photometric study and absolute parameters of the short-period eclipsing binary HH Bootis

    NASA Astrophysics Data System (ADS)

    Gürol, B.; Bradstreet, D. H.; Demircan, Y.; Gürsoytrak, S. H.

    2015-11-01

    We present the results of our investigation on the geometrical and physical parameters of the W UMa type binary system HH Bootis from new CCD (BVRI) light curves and published radial velocity data. The photometric data were obtained in 2011 and 2012 at Ankara University Observatory (AUO). Light and radial velocity observations were analyzed simultaneously using the Wilson-Devinney (2013 revision) code to obtain absolute and geometrical parameters. The system was determined to be a W-type W UMa system of a type different from that suggested by Dal and Sipahi (2013). An interesting cyclic period variation in the time intervals between primary and secondary eclipses ("half-period variation") was discovered and analyzed and its possible cause is discussed. Combining our photometric solution with the spectroscopic data we derived masses and radii of the eclipsing system to be M1 = 0.627M⊙ , M2 = 1.068M⊙ , R1 = 0.782R⊙ and R2 = 0.997R⊙ . New light elements were derived and finally the evolutionary status of the system is discussed.

  20. TRUE MASSES OF RADIAL-VELOCITY EXOPLANETS

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

    Brown, Robert A., E-mail: rbrown@stsci.edu

    We study the task of estimating the true masses of known radial-velocity (RV) exoplanets by means of direct astrometry on coronagraphic images to measure the apparent separation between exoplanet and host star. Initially, we assume perfect knowledge of the RV orbital parameters and that all errors are due to photon statistics. We construct design reference missions for four missions currently under study at NASA: EXO-S and WFIRST-S, with external star shades for starlight suppression, EXO-C and WFIRST-C, with internal coronagraphs. These DRMs reveal extreme scheduling constraints due to the combination of solar and anti-solar pointing restrictions, photometric and obscurational completeness,more » image blurring due to orbital motion, and the “nodal effect,” which is the independence of apparent separation and inclination when the planet crosses the plane of the sky through the host star. Next, we address the issue of nonzero uncertainties in RV orbital parameters by investigating their impact on the observations of 21 single-planet systems. Except for two—GJ 676 A b and 16 Cyg B b, which are observable only by the star-shade missions—we find that current uncertainties in orbital parameters generally prevent accurate, unbiased estimation of true planetary mass. For the coronagraphs, WFIRST-C and EXO-C, the most likely number of good estimators of true mass is currently zero. For the star shades, EXO-S and WFIRST-S, the most likely numbers of good estimators are three and four, respectively, including GJ 676 A b and 16 Cyg B b. We expect that uncertain orbital elements currently undermine all potential programs of direct imaging and spectroscopy of RV exoplanets.« less

  1. Effects of rotation and tidal distortions on the shapes of radial velocity curves of polytropic models of pulsating variable stars

    NASA Astrophysics Data System (ADS)

    Kumar, Tarun; Lal, Arvind Kumar; Pathania, Ankush

    2018-06-01

    Anharmonic oscillations of rotating stars have been studied by various authors in literature to explain the observed features of certain variable stars. However, there is no study available in literature that has discussed the combined effect of rotation and tidal distortions on the anharmonic oscillations of stars. In this paper, we have created a model to determine the effect of rotation and tidal distortions on the anharmonic radial oscillations associated with various polytropic models of pulsating variable stars. For this study we have used the theory of Rosseland to obtain the anharmonic pulsation equation for rotationally and tidally distorted polytropicmodels of pulsating variable stars. The main objective of this study is to investigate the effect of rotation and tidal distortions on the shapes of the radial velocity curves for rotationally and tidally distorted polytropic models of pulsating variable stars. The results of the present study show that the rotational effects cause more deviations in the shapes of radial velocity curves of pulsating variable stars as compared to tidal effects.

  2. VizieR Online Data Catalog: Radial velocities of HD 133131A and HD 133131B (Teske+, 2016)

    NASA Astrophysics Data System (ADS)

    Teske, J. K.; Shectman, S. A.; Vogt, S. S.; Diaz, M.; Butler, R. P.; Crane, J. D.; Thompson, I. B.; Arriagada, P.

    2017-05-01

    The radial velocity observations of HD133131A and B are part of the large Magellan Planet Search Program, which began in 2002 and is surveying a sample of ~500 of the nearest stars (<100pc). The survey was started with observations from the Magellan Inamori Kyocera Echelle (MIKE) echelle spectrograph, mounted for a limited time on the Magellan I (Baade), but mostly on Magellan II (Clay), 6.5m telescopes at Las Campanas Observatory. In 2010, the survey switched to using the Carnegie Planet Finder Spectrograph (PFS), a temperature-controlled high-resolution echelle spectrograph built for precision radial velocity observations, on Magellan II. Only HD133131A observations from MIKE are included here. Using a 0.35*5'' slit, MIKE provides spectra with R~70000 in the blue and ~50000 in the red and covers 3900-6200Å. Only the red MIKE orders are used for radial velocity determination, while the blue orders provide coverage of the CaIIH and K lines for monitoring stellar activity. The MIKE observations of HD133131A span 2003 June to 2009 July, with total exposure times ranging from 150 to 600s, depending on observing conditions. Both HD133131A and B were observed with PFS, the former observations ranging from 2010 February to 2015 September, and the latter from 2010 August to 2015 September. PFS has a more limited wavelength range than MIKE (3880-6680Å), but still covers the entire iodine wavelength region, CaIIH and K, and Hα. We use a 0.5*2.5'' slit for target observations, providing R~80000 in the iodine region. The total exposure times for the A component range from 285 to 720s, and for the B component range from 282 to 800s. (6 data files).

  3. Low-Resolution Radial-Velocity Monitoring of Pulsating sdBs in the Kepler Field

    NASA Astrophysics Data System (ADS)

    Telting, J.; Östensen, R.; Reed, M.; Kiæerad, F.; Farris, L.; Baran, A.; Oreiro, R.; O'Toole, S.

    2014-04-01

    We present preliminary results from an ongoing spectroscopic campaign to uncover the binary status of the 18 known pulsating subdwarf B stars and the one pulsating BHB star observed with the Kepler spacecraft. During the 2010-2012 observing seasons, we have used the KP4m Mayall, NOT, and WHT telescopes to obtain low-resolution (R˜2000-2500) Balmer-line spectroscopy of our sample stars. We applied a standard cross-correlation technique to derive radial velocities, and find clear evidence for binarity in several of the pulsators, some of which were not previously known to be binaries.

  4. VizieR Online Data Catalog: Radial velocities of 51 Peg (Martins+, 2015)

    NASA Astrophysics Data System (ADS)

    Martins, J. H. C.; Santos, N. C.; Figueira, P.; Faria, J. P.; Montalto, M.; Boisse, I.; Ehrenreich, D.; Lovis, C.; Mayor, M.; Melo, C.; Pepe, F.; Sousa, S.; Udry, S.; Cunha, D.

    2015-04-01

    The table contains the radial velocity data for HARPS observations of 51 Peg. This data was collected with the HARPS spectrograph at ESO's 3.6-m Telescope at La Silla-Paranal Observatory, as part of ESO programme 091.C-0271. It consists of 91 spectra observed in seven different nights (2013-06-08, 2013-06-25, 2013-08-02, 2013-08-04, 2013-09-05, 2013-09-09 and 2013-09-30) totalling around 12.5h of observing time. The obtained spectra have a S/N on the 50th order (~5560Å) that varies between 122 and 388. The spectra cover the wavelengths range from roughly 3781Å to 6910Å. (1 data file).

  5. Kinematic Clues to OB Field Star Origins: Radial Velocities, Runaways, and Binaries

    NASA Astrophysics Data System (ADS)

    Januszewski, Helen; Castro, Norberto; Oey, Sally; Becker, Juliette; Kratter, Kaitlin M.; Mateo, Mario; Simón-Díaz, Sergio; Bjorkman, Jon E.; Bjorkman, Karen; Sigut, Aaron; Smullen, Rachel; M2FS Team

    2018-01-01

    Field OB stars are a crucial probe of star formation in extreme conditions. Properties of massive stars formed in relative isolation can distinguish between competing star formation theories, while the statistics of runaway stars allow an indirect test of the densest conditions in clusters. To address these questions, we have obtained multi-epoch, spectroscopic observations for a spatially complete sample of 48 OB field stars in the SMC Wing with the IMACS and M2FS multi-object spectrographs at the Magellan Telescopes. The observations span 3-6 epochs per star, with sampling frequency ranging from one day to about one year. From these spectra, we have calculated the radial velocities (RVs) and, in particular, the systemic velocities for binaries. Thus, we present the intrinsic RV distribution largely uncontaminated by binary motions. We estimate the runaway frequency, corresponding to the high velocity stars in our sample, and we also constrain the binary frequency. The binary frequency and fitted orbital parameters also place important constraints on star formation theories, as these properties drive the process of runaway ejection in clusters, and we discuss these properties as derived from our sample. This unique kinematic analysis of a high mass field star population thus provides a new look at the processes governing formation and interaction of stars in environments at extreme densities, from isolation to dense clusters.

  6. RADIAL VELOCITY VARIABILITY OF FIELD BROWN DWARFS

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

    Prato, L.; Mace, G. N.; Rice, E. L.

    2015-07-20

    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R ∼ 20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity (RV) precision of ∼2 km s{sup −1}, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties,more » and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1σ upper limit for very low mass binary frequency is 18%. Our targets included seven known, wide brown dwarf binary systems. No significant RV variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant fraction of the orbital period. Specialized techniques are required to reach the high precisions sensitive to motion in orbits of very low-mass systems. For eight objects, including six T dwarfs, we present the first published high-resolution spectra, many with high signal to noise, that will provide valuable comparison data for models of brown dwarf atmospheres.« less

  7. VizieR Online Data Catalog: LCES HIRES/Keck radial velocity Exoplanet Survey (Butler+, 2017)

    NASA Astrophysics Data System (ADS)

    Butler, R. P.; Vogt, S. S.; Laughlin, G.; Burt, J. A.; Rivera, E. J.; Tuomi, M.; Teske, J.; Arriagada, P.; Diaz, M.; Holden, B.; Keiser, S.

    2017-08-01

    We present 60949 precision radial velocities of 1624 stars obtained over the past 20 years from the Lick-Carnegie Exoplanet Survey Team (LCES) survey with the HIgh-Resolution Echelle Spectrometer (HIRES) spectrometer on the Keck I telescope. We tabulate a list of 357 significant periodic signals that are of constant period and phase, and not coincident in period and/or phase with stellar activity indices. For this survey, the HIRES spectrometer was configured to operate at a nominal spectral resolving power of R~60000 and wavelength range of 3700-8000Å. (4 data files).

  8. McDonald Observatory Planetary Search - A high precision stellar radial velocity survey for other planetary systems

    NASA Technical Reports Server (NTRS)

    Cochran, William D.; Hatzes, Artie P.

    1993-01-01

    The McDonald Observatory Planetary Search program surveyed a sample of 33 nearby F, G, and K stars since September 1987 to search for substellar companion objects. Measurements of stellar radial velocity variations to a precision of better than 10 m/s were performed as routine observations to detect Jovian planets in orbit around solar type stars. Results confirm the detection of a companion object to HD114762.

  9. Chromospherically Active Stars in the RAdial Velocity Experiment (RAVE) Survey. I. The Catalog

    NASA Astrophysics Data System (ADS)

    Žerjal, M.; Zwitter, T.; Matijevič, G.; Strassmeier, K. G.; Bienaymé, O.; Bland-Hawthorn, J.; Boeche, C.; Freeman, K. C.; Grebel, E. K.; Kordopatis, G.; Munari, U.; Navarro, J. F.; Parker, Q. A.; Reid, W.; Seabroke, G.; Siviero, A.; Steinmetz, M.; Wyse, R. F. G.

    2013-10-01

    RAVE, the unbiased magnitude limited survey of southern sky stars, contained 456,676 medium-resolution spectra at the time of our analysis. Spectra cover the Ca II infrared triplet (IRT) range, which is a known indicator of chromospheric activity. Our previous work classified all spectra using locally linear embedding. It identified 53,347 cases with a suggested emission component in calcium lines. Here, we use a spectral subtraction technique to measure the properties of this emission. Synthetic templates are replaced by the observed spectra of non-active stars to bypass the difficult computations of non-local thermal equilibrium profiles of the line cores and stellar parameter dependence. We derive both the equivalent width of the excess emission for each calcium line on a 5 Å wide interval and their sum EWIRT for ~44,000 candidate active dwarf stars with signal-to-noise ratio >20, with no cuts on the basis of the source of their emission flux. From these, ~14,000 show a detectable chromospheric flux with at least a 2σ confidence level. Our set of active stars vastly enlarges previously known samples. Atmospheric parameters and, in some cases, radial velocities of active stars derived from automatic pipelines suffer from systematic shifts due to their shallower calcium lines. We re-estimate the effective temperature, metallicity, and radial velocities for candidate active stars. The overall distribution of activity levels shows a bimodal shape, with the first peak coinciding with non-active stars and the second with the pre-main-sequence cases. The catalog will be made publicly available with the next RAVE public data releases.

  10. Data reduction, radial velocities and stellar parameters from spectra in the very low signal-to-noise domain

    NASA Astrophysics Data System (ADS)

    Malavolta, Luca

    2013-10-01

    Large astronomical facilities usually provide data reduction pipeline designed to deliver ready-to-use scientific data, and too often as- tronomers are relying on this to avoid the most difficult part of an astronomer job Standard data reduction pipelines however are usu- ally designed and tested to have good performance on data with av- erage Signal to Noise Ratio (SNR) data, and the issues that are related with the reduction of data in the very low SNR domain are not taken int account properly. As a result, informations in data with low SNR are not optimally exploited. During the last decade our group has collected thousands of spec- tra using the GIRAFFE spectrograph at Very Large Telescope (Chile) of the European Southern Observatory (ESO) to determine the ge- ometrical distance and dynamical state of several Galactic Globular Clusters but ultimately the analysis has been hampered by system- atics in data reduction, calibration and radial velocity measurements. Moreover these data has never been exploited to get other informa- tions like temperature and metallicity of stars, because considered too noisy for these kind of analyses. In this thesis we focus our attention on data reduction and analysis of spectra with very low SNR. The dataset we analyze in this thesis comprises 7250 spectra for 2771 stars of the Globular Cluster M 4 (NGC 6121) in the wavelength region 5145-5360Å obtained with GIRAFFE. Stars from the upper Red Giant Branch down to the Main Sequence have been observed in very different conditions, including nights close to full moon, and reaching SNR - 10 for many spectra in the dataset. We will first review the basic steps of data reduction and spec- tral extraction, adapting techniques well tested in other field (like photometry) but still under-developed in spectroscopy. We improve the wavelength dispersion solution and the correction of radial veloc- ity shift between day-time calibrations and science observations by following a completely

  11. Inversion of Surface Wave Phase Velocities for Radial Anisotropy to an Depth of 1200 km

    NASA Astrophysics Data System (ADS)

    Xing, Z.; Beghein, C.; Yuan, K.

    2012-12-01

    This study aims to evaluate three dimensional radial anisotropy to an depth of 1200 km. Radial anisotropy describes the difference in velocity between horizontally polarized Rayleigh waves and vertically polarized Love waves. Its presence in the uppermost 200 km mantle has well been documented by different groups, and has been regarded as an indicator of mantle convection which aligns the intrinsically anisotropic minerals, largely olivine, to form large scale anisotropy. However, there is no global agreement on whether anisotropy exists in the region below 200 km. Recent models also associate a fast vertically polarized shear wave with vertical upwelling mantle flow. The data used in this study is the globally isotropic phase velocity models of fundamental and higher mode Love and Rayleigh waves (Visser, 2008). The inclusion of higher mode surface wave phase velocity provides sensitivities to structure at depth that extends to below the transition zone. While the data is the same as used by Visser (2008), a quite different parameterization is applied. All the six parameters - five elastic parameters A, C, F, L, N and density - are now regarded as independent, which rules out possible biased conclusions induced by scaling relation method used in several previous studies to reduce the number of parameters partly due to limited computing resources. The data need to be modified by crustal corrections (Crust2.0) as we want to look at the mantle structure only. We do this by eliminating the perturbation in surface wave phase velocity caused by the difference in crustal structure with respect to the referent model PREM. Sambridge's Neighborhood Algorithm is used to search the parameter space. The introduction of such a direct search technique pales the traditional inversion method, which requires regularization or some unnecessary priori restriction on the model space. On the contrary, the new method will search the full model space, providing probability density

  12. Three-dimensional inviscid analysis of radial-turbine flow and a limited comparison with experimental data

    NASA Technical Reports Server (NTRS)

    Choo, Y. K.; Civinskas, K. C.

    1985-01-01

    The three-dimensional inviscid DENTON code is used to analyze flow through a radial-inflow turbine rotor. Experimental data from the rotor are compared with analytical results obtained by using the code. The experimental data available for comparison are the radial distributions of circumferentially averaged values of absolute flow angle and total pressure downstream of the rotor exit. The computed rotor-exit flow angles are generally underturned relative to the experimental values, which reflect the boundary-layer separation at the trailing edge and the development of wakes downstream of the rotor. The experimental rotor is designed for a higher-than-optimum work factor of 1.126 resulting in a nonoptimum positive incidence and causing a region of rapid flow adjustment and large velocity gradients. For this experimental rotor, the computed radial distribution of rotor-exit to turbine-inlet total pressure ratios are underpredicted due to the errors in the finite-difference approximations in the regions of rapid flow adjustment, and due to using the relatively coarser grids in the middle of the blade region where the flow passage is highly three-dimensional. Additional results obtained from the three-dimensional inviscid computation are also presented, but without comparison due to the lack of experimental data. These include quasi-secondary velocity vectors on cross-channel surfaces, velocity components on the meridional and blade-to-blade surfaces, and blade surface loading diagrams. Computed results show the evolution of a passage vortex and large streamline deviations from the computational streamwise grid lines. Experience gained from applying the code to a radial turbine geometry is also discussed.

  13. Three-dimensional inviscid analysis of radial turbine flow and a limited comparison with experimental data

    NASA Technical Reports Server (NTRS)

    Choo, Y. K.; Civinskas, K. C.

    1985-01-01

    The three-dimensional inviscid DENTON code is used to analyze flow through a radial-inflow turbine rotor. Experimental data from the rotor are compared with analytical results obtained by using the code. The experimental data available for comparison are the radial distributions of circumferentially averaged values of absolute flow angle and total pressure downstream of the rotor exit. The computed rotor-exit flow angles are generally underturned relative to the experimental values, which reflect the boundary-layer separation at the trailing edge and the development of wakes downstream of the rotor. The experimental rotor is designed for a higher-than-optimum work factor of 1.126 resulting in a nonoptimum positive incidence and causing a region of rapid flow adjustment and large velocity gradients. For this experimental rotor, the computed radial distribution of rotor-exit to turbine-inlet total pressure ratios are underpredicted due to the errors in the finite-difference approximations in the regions of rapid flow adjustment, and due to using the relatively coarser grids in the middle of the blade region where the flow passage is highly three-dimensional. Additional results obtained from the three-dimensional inviscid computation are also presented, but without comparison due to the lack of experimental data. These include quasi-secondary velocity vectors on cross-channel surfaces, velocity components on the meridional and blade-to-blade surfaces, and blade surface loading diagrams. Computed results show the evolution of a passage vortex and large streamline deviations from the computational streamwise grid lines. Experience gained from applying the code to a radial turbine geometry is also discussed.

  14. SKARPS: The Search for Kuiper Belts around Radial-Velocity Planet Stars

    NASA Technical Reports Server (NTRS)

    Bryden, Geoffrey; Marshall, Jonathan; Stapelfeldt, Karl; Su, Kate; Wyatt, Mark

    2011-01-01

    The Search for Kuiper belts Around Radial-velocity Planet Stars - SKARPS -is a Herschel survey of solar-type stars known to have orbiting planets. When complete, the 100-star SKARPS sample will be large enough for a meaningful statistical comparison against stars not known to have planets. (This control sample has already been observed by Herschel's DUst around NEarby Stars - DUNES - key program). Initial results include previously known disks that are resolved for the first time and newly discovered disks that are fainter and colder than those typically detected by Spitzer. So far, with only half of the sample in hand, there is no measured correlation between inner RV planets and cold outer debris. While this is consistent with the results from Spitzer, it is in contrast with the relationship suggested by the prominent debris disks in imaged-planet systems.

  15. Rubidium-traced white-light etalon calibrator for radial velocity measurements at the cm s-1 level

    NASA Astrophysics Data System (ADS)

    Stürmer, Julian; Seifahrt, Andreas; Schwab, Christian; Bean, Jacob L.

    2017-04-01

    We report on the construction and testing of a vacuum-gap Fabry-Pérot etalon calibrator for high precision radial velocity spectrographs. Our etalon is traced against a rubidium frequency standard to provide a cost effective, yet ultra precise wavelength reference. We describe here a turn-key system working at 500 to 900 nm, ready to be installed at any current and next-generation radial velocity spectrograph that requires calibration over a wide spectral bandpass. Where appropriate, we have used off-the-shelf, commercial components with demonstrated long-term performance to accelerate the development timescale of this instrument. Our system combines for the first time the advantages of passively stabilized etalons for optical and near-infrared wavelengths with the laser-locking technique demonstrated for single-mode fiber etalons. We realize uncertainties in the position of one etalon line at the 10 cm s-1 level in individual measurements taken at 4 Hz. When binning the data over 10 s, we are able to trace the etalon line with a precision of better than 3 cm s-1. We present data obtained during a week of continuous operation where we detect (and correct for) the predicted, but previously unobserved shrinking of the etalon Zerodur spacer corresponding to a shift of 13 cm s-1 per day.

  16. The Mass of the Candidate Exoplanet Companion to HD 33636 from Hubble Space Telescope Astrometry and High-Precision Radial Velocities

    NASA Astrophysics Data System (ADS)

    Bean, Jacob L.; McArthur, Barbara E.; Benedict, G. Fritz; Harrison, Thomas E.; Bizyaev, Dmitry; Nelan, Edmund; Smith, Verne V.

    2007-08-01

    We have determined a dynamical mass for the companion to HD 33636 that indicates it is a low-mass star instead of an exoplanet. Our result is based on an analysis of Hubble Space Telescope (HST) astrometry and ground-based radial velocity data. We have obtained high-cadence radial velocity measurements spanning 1.3 yr of HD 33636 with the Hobby-Eberly Telescope at McDonald Observatory. We combined these data with previously published velocities to create a data set that spans 9 yr. We used this data set to search for, and place mass limits on, the existence of additional companions in the HD 33636 system. Our high-precision astrometric observations of the system with the HST Fine Guidance Sensor 1r span 1.2 yr. We simultaneously modeled the radial velocity and astrometry data to determine the parallax, proper motion, and perturbation orbit parameters of HD 33636. Our derived parallax, πabs=35.6+/-0.2 mas, agrees within the uncertainties with the Hipparcos value. We find a perturbation period P=2117.3+/-0.8 days, semimajor axis aA=14.2+/-0.2 mas, and system inclination i=4.1deg+/-0.1deg. Assuming the mass of the primary star to be MA=1.02+/-0.03 Msolar, we obtain a companion mass MB=142+/-11 MJup=0.14+/-0.01 Msolar. The much larger true mass of the companion relative to its minimum mass estimated from the spectroscopic orbit parameters (Msini=9.3 MJup) is due to the nearly face-on orbit orientation. This result demonstrates the value of follow-up astrometric observations to determine the true masses of exoplanet candidates detected with the radial velocity method. Based on data obtained with the NASA/ESA Hubble Space Telescope (HST) and the Hobby-Eberly Telescope (HET). The HST observations were obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. The HET is a joint project of the University of Texas at Austin, Pennsylvania State University, Stanford

  17. The TROY project: Searching for co-orbital bodies to known planets. I. Project goals and first results from archival radial velocity

    NASA Astrophysics Data System (ADS)

    Lillo-Box, J.; Barrado, D.; Figueira, P.; Leleu, A.; Santos, N. C.; Correia, A. C. M.; Robutel, P.; Faria, J. P.

    2018-01-01

    Context. The detection of Earth-like planets, exocomets or Kuiper belts show that the different components found in the solar system should also be present in other planetary systems. Trojans are one of these components and can be considered fossils of the first stages in the life of planetary systems. Their detection in extrasolar systems would open a new scientific window to investigate formation and migration processes. Aims: In this context, the main goal of the TROY project is to detect exotrojans for the first time and to measure their occurrence rate (η-Trojan). In this first paper, we describe the goals and methodology of the project. Additionally, we used archival radial velocity data of 46 planetary systems to place upper limits on the mass of possible trojans and investigate the presence of co-orbital planets down to several tens of Earth masses. Methods: We used archival radial velocity data of 46 close-in (P < 5 days) transiting planets (without detected companions) with information from high-precision radial velocity instruments. We took advantage of the time of mid-transit and secondary eclipses (when available) to constrain the possible presence of additional objects co-orbiting the star along with the planet. This, together with a good phase coverage, breaks the degeneracy between a trojan planet signature and signals coming from additional planets or underestimated eccentricity. Results: We identify nine systems for which the archival data provide >1σ evidence for a mass imbalance between L4 and L5. Two of these systems provide >2σ detection, but no significant detection is found among our sample. We also report upper limits to the masses at L4/L5 in all studied systems and discuss the results in the context of previous findings. Radial velocity 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/609/A96

  18. Digital Doppler Radial Velocity Data Compared Objectively with Digital Reflectivity Radar Data.

    DTIC Science & Technology

    1980-05-01

    AD-A092 318 AIR FORCE INST OF TECH WRIGHT-PATTERSON AFS OH F/6 17/9 DI6ITAL DOPPLER RADIAL VELOCITY DATA COMPARED OBJECTIVELY WITH --ETC(UMAY G0 T F...Technology (ATCQ D.:rp’: ofWbi fcr. rlght-Paterson AfS OH _45433.- . 19. KEY WORDS (Continue on reverse side it necessary anld Identify by block number) 8...14I 4J ZUi 0 0’ ~0 MWiLi )0( InO 011C4-. ɜ l- W OW o. .4 w U CZt ( - 3 a p-N a M 0 .LtW a X 0N- W U W XOL :) DWuUvN CY Z- O It 0% toI a C-~z 10- 2: J 3

  19. Stationary Plasma Thruster Ion Velocity Distribution

    NASA Technical Reports Server (NTRS)

    Manzella, David H.

    1994-01-01

    A nonintrusive velocity diagnostic based on laser induced fluorescence of the 5d4F(5/2)-6p4D(5/2) singly ionized xenon transition was used to interrogate the exhaust of a 1.5 kW Stationary Plasma Thruster (SPT). A detailed map of plume velocity vectors was obtained using a simplified, cost-effective, nonintrusive, semiconductor laser based scheme. Circumferential velocities on the order of 250 m/s were measured which implied induced momentum torques of approximately 5 x 10(exp -2) N-cm. Axial and radial velocities were evaluated one mm downstream of the cathode at several locations across the width of the annular acceleration channel. Radial velocities varied linearly with radial distance. A maximum radial velocity of 7500 m/s was measured 8 mm from the center of the channel. Axial velocities as large as 16,500 m/s were measured.

  20. ORBITAL SOLUTIONS AND ABSOLUTE ELEMENTS OF THE ECLIPSING BINARY EE AQUARII

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

    Wronka, Marissa Diehl; Gold, Caitlin; Sowell, James R.

    2010-04-15

    EE Aqr is a 7.9 mag Algol variable with a 12 hr orbital period. The Wilson-Devinney program is used to simultaneously solve 11 previously published light curves together with two existing radial velocity curves. The resulting masses are M {sub 1} = 2.24 {+-} 0.13 M {sub sun} and M {sub 2} = 0.72 {+-} 0.04 M {sub sun}, and the radii are R {sub 1} = 1.76 {+-} 0.03 R {sub sun} and R {sub 2} = 1.10 {+-} 0.02 R {sub sun}. The system has the lower-mass component completely filling its Roche lobe. Its distance from Hipparcos observationsmore » is 112 {+-} 10 pc. An improved ephemeris is derived, and no deviations in the period over time were seen. Light and velocity curve parameters, orbital elements, and absolute dimensions are presented, plus a comparison is made with previous solutions.« less

  1. VizieR Online Data Catalog: WASP-103b radial velocities and light curves (Gillon+, 2014)

    NASA Astrophysics Data System (ADS)

    Gillon, M.; Anderson, D. R.; Collier-Cameron, A.; Delrez, L.; Hellier, C.; Jehin, E.; Lendl, M.; Maxted, P. F. L.; Pepe, F.; Pollacco, D.; Queloz, D.; Segransan, D.; Smith, A. M. S.; Smalley, B.; Southworth, J.; Triaud, A. H. M. J.; Udry, S.; Van Grootel, V.; West, R. G.

    2014-01-01

    The host star WASP-103 (1SWASPJ163715.59+071100.0 = 2MASS16371556+0711000; V=12.1, K=10.8) was observed by the southern station of the WASP survey during the 2010, 2011, and 2012 observing seasons, covering the intervals 2010 May 15 to Aug. 16, 2011 Mar. 26 to Aug. 20, and 2012 Mar. 25 to Jun. 28. Files wasp.dat, trappist.dat, euler.dat contain the photometric time-series presented in the paper. File rv.dat contains the radial velocity time-series presented in the paper. (4 data files).

  2. A Preliminary Analysis on Empirical Attenuation of Absolute Velocity Response Spectra (1 to 10s) in Japan

    NASA Astrophysics Data System (ADS)

    Dhakal, Y. P.; Kunugi, T.; Suzuki, W.; Aoi, S.

    2013-12-01

    The Mw 9.1 Tohoku-oki earthquake caused strong shakings of super high rise and high rise buildings constructed on deep sedimentary basins in Japan. Many people felt difficulty in moving inside the high rise buildings even on the Osaka basin located at distances as far as 800 km from the epicentral area. Several empirical equations are proposed to estimate the peak ground motions and absolute acceleration response spectra applicable mainly within 300 to 500km from the source area. On the other hand, Japan Meteorological Agency has recently proposed four classes of absolute velocity response spectra as suitable indices to qualitatively describe the intensity of long-period ground motions based on the observed earthquake records, human experiences, and actual damages that occurred in the high rise and super high rise buildings. The empirical prediction equations have been used in disaster mitigation planning as well as earthquake early warning. In this study, we discuss the results of our preliminary analysis on attenuation relation of absolute velocity response spectra calculated from the observed strong motion records including those from the Mw 9.1 Tohoku-oki earthquake using simple regression models with various model parameters. We used earthquakes, having Mw 6.5 or greater, and focal depths shallower than 50km, which occurred in and around Japanese archipelago. We selected those earthquakes for which the good quality records are available over 50 observation sites combined from K-NET and KiK-net. After a visual inspection on approximately 21,000 three component records from 36 earthquakes, we used about 15,000 good quality records in the period range of 1 to 10s within the hypocentral distance (R) of 800km. We performed regression analyses assuming the following five regression models. (1) log10Y (T) = c+ aMw - log10R - bR (2) log10Y (T) = c+ aMw - log10R - bR +gS (3) log10Y (T) = c+ aMw - log10R - bR + hD (4) log10Y (T) = c+ aMw - log10R - bR +gS +hD (5) log10Y

  3. RADIAL VELOCITY MONITORING OF KEPLER HEARTBEAT STARS

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

    Shporer, Avi; Fuller, Jim; Isaacson, Howard

    2016-09-20

    Heartbeat stars (HB stars) are a class of eccentric binary stars with close periastron passages. The characteristic photometric HB signal evident in their light curves is produced by a combination of tidal distortion, heating, and Doppler boosting near orbital periastron. Many HB stars continue to oscillate after periastron and along the entire orbit, indicative of the tidal excitation of oscillation modes within one or both stars. These systems are among the most eccentric binaries known, and they constitute astrophysical laboratories for the study of tidal effects. We have undertaken a radial velocity (RV) monitoring campaign of Kepler HB stars inmore » order to measure their orbits. We present our first results here, including a sample of 22 Kepler HB systems, where for 19 of them we obtained the Keplerian orbit and for 3 other systems we did not detect a statistically significant RV variability. Results presented here are based on 218 spectra obtained with the Keck/HIRES spectrograph during the 2015 Kepler observing season, and they have allowed us to obtain the largest sample of HB stars with orbits measured using a single instrument, which roughly doubles the number of HB stars with an RV measured orbit. The 19 systems measured here have orbital periods from 7 to 90 days and eccentricities from 0.2 to 0.9. We show that HB stars draw the upper envelope of the eccentricity–period distribution. Therefore, HB stars likely represent a population of stars currently undergoing high eccentricity migration via tidal orbital circularization, and they will allow for new tests of high eccentricity migration theories.« less

  4. Correlated Radial Velocity and X-Ray Variations in HD 154791/4U 1700+24

    NASA Astrophysics Data System (ADS)

    Galloway, Duncan K.; Sokoloski, J. L.; Kenyon, Scott J.

    2002-12-01

    We present evidence for approximately 400 day variations in the radial velocity of HD 154791 (V934 Her), the suggested optical counterpart of 4U 1700+24. The variations are correlated with the previously reported ~400 day variations in the X-ray flux of 4U 1700+24, which supports the association of these two objects, as well as the identification of this system as the second known X-ray binary in which a neutron star accretes from the wind of a red giant. The HD 154791 radial velocity variations can be fitted with an eccentric orbit with period 404+/-3 days, amplitude K=0.75+/-0.12kms-1, and eccentricity e=0.26+/-0.15. There are also indications of variations on longer timescales >~2000 days. We have reexamined all available All-Sky Monitor (ASM) data following an unusually large X-ray outburst in 1997-1998 and confirm that the 1 day averaged 2-10 keV X-ray flux from 4U 1700+24 is modulated with a period of 400+/-20 days. The mean profile of the persistent X-ray variations was approximately sinusoidal, with an amplitude of 0.108+/-0.012 ASM counts s-1 (corresponding to 31% rms). The epoch of X-ray maximum was approximately 40 days after the time of periastron, according to the eccentric orbital fit. If the 400 day oscillations from HD 154791/4U 1700+24 are due to orbital motion, then the system parameters are probably close to those of the only other neutron star symbiotic-like binary, GX 1+4. We discuss the similarities and differences between these two systems.

  5. Dynamically consistent hydrography and absolute velocity in the eastern North Atlantic Ocean

    NASA Technical Reports Server (NTRS)

    Wunsch, Carl

    1994-01-01

    The problem of mapping a dynamically consistent hydrographic field and associated absolute geostrophic flow in the eastern North Atlantic between 24 deg and 36 deg N is related directly to the solution of the so-called thermocline equations. A nonlinear optimization problem involving Needler's P equation is solved to find the hydrography and resulting flow that minimizes the vertical mixing above about 1500 m in the ocean and is simultaneously consistent with the observations. A sharp minimum (at least in some dimensions) is found, apparently corresponding to a solution nearly conserving potential vorticity and with vertical eddy coefficient less than about 10(exp -5) sq m/s. Estimates of `residual' quantities such as eddy coefficients are extremely sensitive to slight modifications to the observed fields. Boundary conditions, vertical velocities, etc., are a product of the optimization and produce estimates differing quantitatively from prior ones relying directly upon observed hydrography. The results are generally insensitive to particular elements of the solution methodology, but many questions remain concerning the extent to which different synoptic sections can be asserted to represent the same ocean. The method can be regarded as a practical generalization of the beta spiral and geostrophic balance inverses for the estimate of absolute geostrophic flows. Numerous improvements to the methodology used in this preliminary attempt are possible.

  6. Towards accurate radial velocities from early type spectra in the framework of an ESO key programme

    NASA Astrophysics Data System (ADS)

    Verschueren, Werner; David, M.; Hensberge, Herman

    In order to elucidate the internal kinematics in very young stellar groups, a dedicated machinery was set up, which made it possible to proceed from actual observations to reductions and correlation analysis to the ultimate derivation of early-type stellar radial velocities (RVs) with the requisite precision. The following ingredients are found to be essential to obtain RVs of early-type stars at the 1-km/s level of precision: high-resolution, high-S/N spectra covering a large wavelength range; maximal reduction of observational errors and the use of optimal reduction procedures; the intelligent use of a versatile cross-correlation package; and comparison of velocities derived from different regions of the spectrum in order to detect systematic mismatches between object and template spectrum in some of the lines.

  7. Development of a large blazed transmission grating by effective binary index modulation for the GAIA radial velocity spectrometer

    NASA Astrophysics Data System (ADS)

    Erdmann, M.; Kley, E.-B.; Zeitner, U.

    2017-11-01

    Gaia is an ambitious ESA mission to chart a three-dimensional map of our Galaxy, the Milky Way, in the process revealing the composition, formation and evolution of the Galaxy. Gaia will provide unprecedented positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and cinematic census of about one billion stars in our Galaxy. The payload consists of 2 Three Mirror Anastigmat (TMA) telescopes (aperture size 1.5 m x 0.5 m), 3 instruments (astrometer, photometer and spectrometer) and 106 butted CCDs assembled to a 0.9 Giga-Pixel focal plane. The Radial Velocity Spectrometer (RVS) of Gaia measures the red shift of the stars in the spectral band between 847 nm and 874 nm. The spectrometer is a fully refractive optics consisting of 2 Fery prisms, 2 prisms, a pass band filter and a blazed transmission grating (instrument mass about 30 kg). It is located in the vicinity of the focal plane and illuminates 12 of the 106 Charge Coupled Devices (CCDs). Gaia is in the implementation phase, the launch of the 2120 kg mass satellite is planned in Dec. 2012.

  8. Absolute instability of the Gaussian wake profile

    NASA Technical Reports Server (NTRS)

    Hultgren, Lennart S.; Aggarwal, Arun K.

    1987-01-01

    Linear parallel-flow stability theory has been used to investigate the effect of viscosity on the local absolute instability of a family of wake profiles with a Gaussian velocity distribution. The type of local instability, i.e., convective or absolute, is determined by the location of a branch-point singularity with zero group velocity of the complex dispersion relation for the instability waves. The effects of viscosity were found to be weak for values of the wake Reynolds number, based on the center-line velocity defect and the wake half-width, larger than about 400. Absolute instability occurs only for sufficiently large values of the center-line wake defect. The critical value of this parameter increases with decreasing wake Reynolds number, thereby indicating a shrinking region of absolute instability with decreasing wake Reynolds number. If backflow is not allowed, absolute instability does not occur for wake Reynolds numbers smaller than about 38.

  9. Predictors of degenerative medial meniscus extrusion: radial component and knee osteoarthritis.

    PubMed

    Lee, Dae-Hee; Lee, Bum-Sik; Kim, Jong-Min; Yang, Kyung-Sook; Cha, Eun-Jong; Park, Ji-Hun; Bin, Seong-Il

    2011-02-01

    the purpose of this study was to determine the effect of a radial tear on degenerative medial meniscus posterior horn tear extrusion and to identify predictors of medial meniscus extrusion. we reviewed the records of 102 knees with medial meniscus posterior horn tears and degeneration that underwent a partial meniscectomy. Tears were classified as root (n = 17) and non-root (n = 85) tears, or as radial (n = 46) and non-radial (n = 56) tears. Groups were compared in terms of absolute and relative meniscal extrusion, and the proportion of knees with major (> 3 mm) extrusion. Multiple regression analysis was used to identify predictors of extrusion. the radial group had greater mean absolute (4 ± 1 vs. 3 ± 1 mm, P = 0.001) and relative (31 ± 11 vs. 23 ± 12%, P = 0.031) extrusion than the non-radial group. The radial group also had a greater proportion of major extrusions than the non-radial group (74% vs. 26%; P = 0.016). In contrast, the root tear and non-root tear groups were similar in terms of mean absolute (3 ± 1 vs. 3 ± 1 mm, P = n.s.) and relative (30 ± 7 vs. 26 ± 13%; P = n.s.) extrusion and in terms of proportion with major extrusions (59 vs. 55%; P = n.s.). Extrusion was found to be associated with a similar strength with both the presence of a radial component and the preoperative Kellgren-Lawrence grade. meniscal extrusion was greater and more severe in knees with a radial tear component than in knees without a radial component. The incidence and degree of major extrusion was similar in knees with root tears and non-root tears. A radial component and knee osteoarthritis severity were similarly predictive of absolute and relative extrusion. Meniscal extrusion in osteoarthritic knees was associated not only with degenerative meniscal tear but also with osteoarthritis severity. Therefore, arthroscopic meniscal procedures, especially meniscal repair, should be cautiously considered in patients with meniscal extrusion.

  10. Searching for co-orbital planets by combining transit and radial-velocity measurements

    NASA Astrophysics Data System (ADS)

    Robutel, p.; Leleu, A.; Correia, A.; Lillo-Box, J.

    2017-09-01

    Co-orbital planetary systems consist of two planets orbiting with the same period a central star. If co-orbital bodies are common in the solar system and are also a natural output of planetary formation models, so far none have been found in extrasolar systems. This lack may be due to observational biases, since the main detection methods are unable to spot co-orbital companions when they are small or near the Lagrangian equilibrium points. We propose a simple method, based on an idea from Ford & Gaudi (2006), that allows the detection of co-orbital companions, and relies on a single parameter proportional to the mass ratio of the two planets. This method is applied to archival radial velocity data of 46 close-in transiting planets among which a few are strong candidates to harbor a co-orbital companion.

  11. Crustal shear wave velocity and radial anisotropy beneath the Rio Grande rift from ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Fu, Yuanyuan V.; Li, Aibing

    2015-02-01

    Shear wave velocity and radial anisotropy beneath New Mexico are obtained from ambient seismic noise tomography using data from the Transportable Array. Besides the distinct seismic structure imaged across the Rio Grande rift from the Colorado Plateau to the Great Plains, both velocity and anisotropy models also reveal significant variations along the rift. The rift at Albuquerque is characterized by remarkably low velocity in the shallow crust, high velocity and strong positive anisotropy in the middle and lower crust, and low velocity in the upper mantle. These observations can be interpreted as magma accumulation in the shallow crust and significant mafic underplating in the lower crust with abundant melt supply from the hot mantle. We propose that the Albuquerque region has recently been experiencing the most vigorous extensional deformation in the rift. Positive anisotropy with Vsh > Vsv appears in the central and southern rifts with a stronger anisotropy beneath younger volcanoes, reflecting layering of magma intrusion due to past and recent rifting activities. The low velocities in the uppermost mantle are observed under high-elevation places, the Jemez Lineament, northern rift, and east rift boundary, implying that the buoyancy of hot mantle largely compensates the local high topography. Low mantle velocities appear at the boundary of the southern rift, corresponding to the large lithosphere thickness change, instead of the rift center, consistent with the prediction from the small-scale, edge-driven mantle convection model. We conclude that the edge-driven upper mantle convection is probably the dominant mechanism for the recent and current rifting and uplift in the Rio Grande rift.

  12. Velocity diagrams

    NASA Technical Reports Server (NTRS)

    Whitney, W. J.; Stewart, W. L.

    1972-01-01

    The selection and design of velocity diagrams for axial flow turbines are considered. Application is treated in two parts which includes: (1) mean-section diagrams, and (2) radial variation of diagrams. In the first part, the velocity diagrams occurring at the mean section are assumed to represent the average conditions encountered by the turbine. The different types of diagrams, their relation to stage efficiency, and their selection when staging is required are discussed. In the second part, it is shown that in certain cases the mean-section diagrams may or may not represent the average flow conditions for the entire blade span. In the case of relatively low hub- to tip-radius ratios, substantial variations in the velocity diagrams are encountered. The radial variations in flow conditions and their effect on the velocity diagrams are considered.

  13. Absolute Wavelength Calibration of the IDSII Spectrometer for Impurity Ion Velocity Measurements in the MST

    NASA Astrophysics Data System (ADS)

    Baltzer, M.; Craig, D.; den Hartog, D. J.; Nornberg, M. D.; MST Team

    2014-10-01

    The MST operates two Ion Doppler Spectrometers (IDS) for high time-resolution passive and active measurements of impurity ion emission. Absolutely calibrated measurements of flow are difficult because the spectrometers record data within 0.3 nm of the line of interest, and commercial calibration lamps do not produce lines in this narrow range . Four calibration methods were investigated. First, emission along the chord bisecting the poloidal plane was measured as it should have no time-averaged Doppler shift. Second, a calibrated CCD spectrometer and the IDSII were used to observe the same plasma from opposing sides so as to measure opposite Doppler shifts. The unshifted line is located halfway between the two opposing measurements. Third, the two fibers of the IDSI were positioned to take absolute flow measurements using opposing views. Substituting the IDSII for one of the IDSI fibers, absolute measurements of flow from the IDSI were used to calibrate the IDSII. Finally, an optical system was designed to filter an ultraviolet LED, providing a known wavelength source within the spectral range covered by the IDSII. The optical train is composed of an air-gapped etalon and fused silica lenses. The quality of calibration for each of these methods is analyzed and their results compared. Preliminary impurity ion velocity measurements are shown. This work has been supported by the US DOE and the NSF.

  14. Dynamically balanced absolute sea level of the global ocean derived from near-surface velocity observations

    NASA Astrophysics Data System (ADS)

    Niiler, Pearn P.; Maximenko, Nikolai A.; McWilliams, James C.

    2003-11-01

    The 1992-2002 time-mean absolute sea level distribution of the global ocean is computed for the first time from observations of near-surface velocity. For this computation, we use the near-surface horizontal momentum balance. The velocity observed by drifters is used to compute the Coriolis force and the force due to acceleration of water parcels. The anomaly of horizontal pressure gradient is derived from satellite altimetry and corrects the temporal bias in drifter data distribution. NCEP reanalysis winds are used to compute the force due to Ekman currents. The mean sea level gradient force, which closes the momentum balance, is integrated for mean sea level. We find that our computation agrees, within uncertainties, with the sea level computed from the geostrophic, hydrostatic momentum balance using historical mean density, except in the Antarctic Circumpolar Current. A consistent horizontally and vertically dynamically balanced, near-surface, global pressure field has now been derived from observations.

  15. Absolute and convective instabilities of a film flow down a vertical fiber subjected to a radial electric field

    NASA Astrophysics Data System (ADS)

    Liu, Rong; Chen, Xue; Ding, Zijing

    2018-01-01

    We consider the motion of a gravity-driven flow down a vertical fiber subjected to a radial electric field. This flow exhibits rich dynamics including the formation of droplets, or beads, driven by a Rayleigh-Plateau mechanism modified by the presence of gravity as well as the Maxwell stress at the interface. A spatiotemporal stability analysis is performed to investigate the effect of electric field on the absolute-convective instability (AI-CI) characteristics. We performed a numerical simulation on the nonlinear evolution of the film to examine the transition from CI to AI regime. The numerical results are in excellent agreement with the spatiotemporal stability analysis. The blowup behavior of nonlinear simulation predicts the formation of touchdown singularity of the interface due to the effect of electric field. We try to connect the blowup behavior with the AI-CI characteristics. It is found that the singularities mainly occur in the AI regime. The results indicate that the film may have a tendency to form very sharp tips due to the enhancement of the absolute instability induced by the electric field. We perform a theoretical analysis to study the behaviors of the singularities. The results show that there exists a self-similarity between the temporal and spatial distances from the singularities.

  16. Eigenmodes of Ducted Flows With Radially-Dependent Axial and Swirl Velocity Components

    NASA Technical Reports Server (NTRS)

    Kousen, Kenneth A.

    1999-01-01

    This report characterizes the sets of small disturbances possible in cylindrical and annular ducts with mean flow whose axial and tangential components vary arbitrarily with radius. The linearized equations of motion are presented and discussed, and then exponential forms for the axial, circumferential, and time dependencies of any unsteady disturbances are assumed. The resultant equations form a generalized eigenvalue problem, the solution of which yields the axial wavenumbers and radial mode shapes of the unsteady disturbances. Two numerical discretizations are applied to the system of equations: (1) a spectral collocation technique based on Chebyshev polynomial expansions on the Gauss-Lobatto points, and (2) second and fourth order finite differences on uniform grids. The discretized equations are solved using a standard eigensystem package employing the QR algorithm. The eigenvalues fall into two primary categories: a discrete set (analogous to the acoustic modes found in uniform mean flows) and a continuous band (analogous to convected disturbances in uniform mean flows) where the phase velocities of the disturbances correspond to the local mean flow velocities. Sample mode shapes and eigensystem distributions are presented for both sheared axial and swirling flows. The physics of swirling flows is examined with reference to hydrodynamic stability and completeness of the eigensystem expansions. The effect of assuming exponential dependence in the axial direction is discussed.

  17. Where are the Binaries? Results of a Long-term Search for Radial Velocity Binaries in Proto-planetary Nebulae

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

    Hrivnak, Bruce J.; Lu, Wenxian; Steene, Griet Van de

    We present the results of an expanded, long-term radial velocity search (25 years) for evidence of binarity in a sample of seven bright proto-planetary nebulae (PPNe). The goal is to investigate the widely held view that the bipolar or point-symmetric shapes of planetary nebulae (PNe) and PPNe are due to binary interactions. Observations from three observatories were combined from 2007 to 2015 to search for variations on the order of a few years and then combined with earlier observations from 1991 to 1995 to search for variations on the order of decades. All seven show velocity variations due to periodicmore » pulsation in the range of 35–135 days. However, in only one PPN, IRAS 22272+5435, did we find even marginal evidence for multi-year variations that might be due to a binary companion. This object shows marginally significant evidence of a two-year period of low semi-amplitude, which could be due to a low-mass companion, and it also displays some evidence of a much longer period of >30 years. The absence of evidence in the other six objects for long-period radial velocity variations due to a binary companion sets significant constraints on the properties of any undetected binary companions: they must be of low mass, ≤0.2 M {sub ⊙}, or long period, >30 years. Thus the present observations do not provide direct support for the binary hypothesis to explain the shapes of PNe and PPNe and severely constrains the properties of any such undetected companions.« less

  18. Three-dimensional imaging of absolute blood flow velocity and blood vessel position under low blood flow velocity based on Doppler signal information included in scattered light from red blood cells

    NASA Astrophysics Data System (ADS)

    Kyoden, Tomoaki; Akiguchi, Shunsuke; Tajiri, Tomoki; Andoh, Tsugunobu; Hachiga, Tadashi

    2017-11-01

    The development of a system for in vivo visualization of occluded distal blood vessels for diabetic patients is the main target of our research. We herein describe two-beam multipoint laser Doppler velocimetry (MLDV), which measures the instantaneous multipoint flow velocity and can be used to observe the blood flow velocity in peripheral blood vessels. By including a motorized stage to shift the measurement points horizontally and in the depth direction while measuring the velocity, the path of the blood vessel in the skin could be observed using blood flow velocity in three-dimensional space. The relationship of the signal power density between the blood vessel and the surrounding tissues was shown and helped us identify the position of the blood vessel. Two-beam MLDV can be used to simultaneously determine the absolute blood flow velocity distribution and identify the blood vessel position in skin.

  19. Multicore fibre photonic lanterns for precision radial velocity Science

    NASA Astrophysics Data System (ADS)

    Gris-Sánchez, Itandehui; Haynes, Dionne M.; Ehrlich, Katjana; Haynes, Roger; Birks, Tim A.

    2018-04-01

    Incomplete fibre scrambling and fibre modal noise can degrade high-precision spectroscopic applications (typically high spectral resolution and high signal to noise). For example, it can be the dominating error source for exoplanet finding spectrographs, limiting the maximum measurement precision possible with such facilities. This limitation is exacerbated in the next generation of infra-red based systems, as the number of modes supported by the fibre scales inversely with the wavelength squared and more modes typically equates to better scrambling. Substantial effort has been made by major research groups in this area to improve the fibre link performance by employing non-circular fibres, double scramblers, fibre shakers, and fibre stretchers. We present an original design of a multicore fibre (MCF) terminated with multimode photonic lantern ports. It is designed to act as a relay fibre with the coupling efficiency of a multimode fibre (MMF), modal stability similar to a single-mode fibre and low loss in a wide range of wavelengths (380 nm to 860 nm). It provides phase and amplitude scrambling to achieve a stable near field and far-field output illumination pattern despite input coupling variations, and low modal noise for increased stability for high signal-to-noise applications such as precision radial velocity (PRV) science. Preliminary results are presented for a 511-core MCF and compared with current state of the art octagonal fibre.

  20. RADIAL VELOCITY PLANETS DE-ALIASED: A NEW, SHORT PERIOD FOR SUPER-EARTH 55 Cnc e

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

    Dawson, Rebekah I.; Fabrycky, Daniel C., E-mail: rdawson@cfa.harvard.ed, E-mail: daniel.fabrycky@gmail.co

    2010-10-10

    Radial velocity measurements of stellar reflex motion have revealed many extrasolar planets, but gaps in the observations produce aliases, spurious frequencies that are frequently confused with the planets' orbital frequencies. In the case of Gl 581 d, the distinction between an alias and the true frequency was the distinction between a frozen, dead planet and a planet possibly hospitable to life. To improve the characterization of planetary systems, we describe how aliases originate and present a new approach for distinguishing between orbital frequencies and their aliases. Our approach harnesses features in the spectral window function to compare the amplitude andmore » phase of predicted aliases with peaks present in the data. We apply it to confirm prior alias distinctions for the planets GJ 876 d and HD 75898 b. We find that the true periods of Gl 581 d and HD 73526 b/c remain ambiguous. We revise the periods of HD 156668 b and 55 Cnc e, which were afflicted by daily aliases. For HD 156668 b, the correct period is 1.2699 days and the minimum mass is (3.1 {+-} 0.4) M{sub +}. For 55 Cnc e, the correct period is 0.7365 days-the shortest of any known planet-and the minimum mass is (8.3 {+-} 0.3) M{sub +}. This revision produces a significantly improved five-planet Keplerian fit for 55 Cnc, and a self-consistent dynamical fit describes the data just as well. As radial velocity techniques push to ever-smaller planets, often found in systems of multiple planets, distinguishing true periods from aliases will become increasingly important.« less

  1. Precise Near IR Radial Velocity First Light Observations With iSHELL

    NASA Astrophysics Data System (ADS)

    Cale, Bryson L.; Plavchan, Peter; Gagné, Jonathan; Gao, Peter; Nishimoto, America; Tanner, Angelle; Walp, Bernie; Brinkworth, Carolyn; Johnson, John Asher; Vasisht, Gautam

    2018-01-01

    We present our current progress on obtaining precise radial velocities with the new iSHELL spectrograph at NASA's Infrared Telescope Facility. To obtain precise RV's, we use a methane isotopologue absorption gas cell in the calibration unit. Over the past year, we've collected 3-12 epochs of 17 bright G, K, and M dwarfs at a high SNR. By focusing on late type type stars, we obtain relatively higher SNR in the near infrared. We've successfully updated both our spectral and RV extraction pipelines, with a few exceptions. Inherent to the iSHELL data is a wavelength dependent fringing component, which must be incorporated into our model to obtain adequate RV precision. With iSHELL's predecessor, CSHELL, we obtained a precision of 3 m/s on the bright M giant SV Peg. With further progress on our fringing and telluric models, we hope to obtain a precision of <3 m/s with iSHELL, sufficient to detect terrestrial planets in the habitable zone of nearby M dwarfs.

  2. The Gaia-ESO Survey: Empirical determination of the precision of stellar radial velocities and projected rotation velocities

    NASA Astrophysics Data System (ADS)

    Jackson, R. J.; Jeffries, R. D.; Lewis, J.; Koposov, S. E.; Sacco, G. G.; Randich, S.; Gilmore, G.; Asplund, M.; Binney, J.; Bonifacio, P.; Drew, J. E.; Feltzing, S.; Ferguson, A. M. N.; Micela, G.; Neguerela, I.; Prusti, T.; Rix, H.-W.; Vallenari, A.; Alfaro, E. J.; Allende Prieto, C.; Babusiaux, C.; Bensby, T.; Blomme, R.; Bragaglia, A.; Flaccomio, E.; Francois, P.; Hambly, N.; Irwin, M.; Korn, A. J.; Lanzafame, A. C.; Pancino, E.; Recio-Blanco, A.; Smiljanic, R.; Van Eck, S.; Walton, N.; Bayo, A.; Bergemann, M.; Carraro, G.; Costado, M. T.; Damiani, F.; Edvardsson, B.; Franciosini, E.; Frasca, A.; Heiter, U.; Hill, V.; Hourihane, A.; Jofré, P.; Lardo, C.; de Laverny, P.; Lind, K.; Magrini, L.; Marconi, G.; Martayan, C.; Masseron, T.; Monaco, L.; Morbidelli, L.; Prisinzano, L.; Sbordone, L.; Sousa, S. G.; Worley, C. C.; Zaggia, S.

    2015-08-01

    Context. The Gaia-ESO Survey (GES) is a large public spectroscopic survey at the European Southern Observatory Very Large Telescope. Aims: A key aim is to provide precise radial velocities (RVs) and projected equatorial velocities (vsini) for representative samples of Galactic stars, which will complement information obtained by the Gaia astrometry satellite. Methods: We present an analysis to empirically quantify the size and distribution of uncertainties in RV and vsini using spectra from repeated exposures of the same stars. Results: We show that the uncertainties vary as simple scaling functions of signal-to-noise ratio (S/N) and vsini, that the uncertainties become larger with increasing photospheric temperature, but that the dependence on stellar gravity, metallicity and age is weak. The underlying uncertainty distributions have extended tails that are better represented by Student's t-distributions than by normal distributions. Conclusions: Parametrised results are provided, which enable estimates of the RV precision for almost all GES measurements, and estimates of the vsini precision for stars in young clusters, as a function of S/N, vsini and stellar temperature. The precision of individual high S/N GES RV measurements is 0.22-0.26 km s-1, dependent on instrumental configuration. Based on observations collected with the FLAMES spectrograph at VLT/UT2 telescope (Paranal Observatory, ESO, Chile), for the Gaia- ESO Large Public Survey (188.B-3002).Full Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/580/A75

  3. Short-period terrestrial planets and radial velocity stellar jitter.

    NASA Astrophysics Data System (ADS)

    Dumusque, Xavier

    2015-01-01

    Stellar jitter is the main limitation to ultra-precise radial velocity (RV) measurements. It currently precludes our ability to detect a planet like the Earth. Short-period terrestrial planets present first the advantage of inducing a stronger RV signal. In addition, the signal produced by these planets have a period completely different than stellar activity. This allows us, when the observational strategy is adequate, to decorrelate the planetary signal from the jitter induced by the star using filtering techniques. I will show the examples of Kepler-78b and Corot-7b, where the amplitude of the planetary signal can be detected, despite the stellar activity jitter that is 5 and 3 times larger, respectively. The cases of Alpha Cen Bb will also be reviewed, with a new reduction of the published data that increases the significance of the planetary signal.This project is funded by ETAEARTH, a transnational collaboration between European countries and the US (the Swiss Space Office, the Harvard Origin of Life Initiative, the Scottish Universities Physics Alliance, the University of Geneva, the Smithsonian Astrophysical Observatory, the Italian National Astrophysical Institute, the University of St. Andrews, Queens University Belfast, and the University of Edinburgh) setup to optimize the synergy between space-and ground-based data whose scientific potential for the characterization of extrasolar planets can only be fully exploited when analyzed together.

  4. Stellar Angular Momentum Distributions and Preferential Radial Migration

    NASA Astrophysics Data System (ADS)

    Wyse, Rosemary; Daniel, Kathryne J.

    2018-04-01

    I will present some results from our recent investigations into the efficiency of radial migration in stellar disks of differing angular momentum distributions, within a given adopted 2D spiral disk potential. We apply to our models an analytic criterion that determines whether or not individual stars are in orbits that could lead to radial migration around the corotation resonance. We couch our results in terms of the local stellar velocity dispersion and find that the fraction of stars that could migrate radially decreases as the velocity dispersion increases. I will discuss implications and comparisons with the results of other approaches.

  5. Unbiased Inference of the Masses of Transiting Planets from Radial Velocity Follow-up

    NASA Astrophysics Data System (ADS)

    Montet, Benjamin T.

    2018-05-01

    Data from the TESS mission will be used to discover hundreds of small planets amenable to radial velocity (RV) followup. Often, RV observations are obtained until a particular fractional precision on the inferred mass is achieved. I show that when the decision to stop collecting RV observations depends on the mass inferred from already-collected data, this will bias mass measurements upward, particularly when the fixed length of RV observing campaigns is considered. I suggest that observing teams should determine their observing strategy for each star before any data are collected, and all stopping criteria should not directly depend on the inferred mass. Observing teams should explicitly publish both their criteria for observing targets and deciding to end their observations, as well as their mass non-detections to avoid introducing biases into the masses---and thus inferences on the densities, compositions, and atmospheres---of transiting planets.

  6. VizieR Online Data Catalog: HIRES radial velocity measurements (Knutson+, 2014)

    NASA Astrophysics Data System (ADS)

    Knutson, H. A.; Fulton, B. J.; Montet, B. T.; Kao, M.; Ngo, H.; Howard, A. W.; Crepp, J. R.; Hinkley, S.; Bakos, G. A.; Batygin, K.; Johnson, J. A.; Morton, T. D.; Muirhead, P. S.

    2017-06-01

    We observed our target stars using the High Resolution Echelle Spectrometer (HIRES) (Vogt et al. 1994SPIE.2198..362V) on the 10 m Keck I telescope over a period of two years beginning in 2011; many of our targets also had existing HIRES observations taken prior to 2011 by other programs. We used the standard HIRES setup and reduction pipeline employed by the California Planet Search (CPS) consortium (Wright et al. 2004, J/ApJS/152/261; Howard et al. 2009ApJ...696...75H; Johnson et al. 2010PASP..122..149J). Observations were typically obtained with a slit width of 0.86" with integration times optimized to obtain typical signal to noise ratios of 70 per pixel. An iodine cell mounted in front of the spectrometer entrance slit provided a wavelength scale and instrumental profile for the observations (Marcy & Butler, 1992PASP..104..270M; Valenti et al. 1995PASP..107..966V). We obtained a total of approximately 270 new radial velocity measurements for our target sample, with a minimum of four observations per target separated by at least six months. (3 data files).

  7. A Comprehensive Radial Velocity Error Budget for Next Generation Doppler Spectrometers

    NASA Technical Reports Server (NTRS)

    Halverson, Samuel; Ryan, Terrien; Mahadevan, Suvrath; Roy, Arpita; Bender, Chad; Stefansson, Guomundur Kari; Monson, Andrew; Levi, Eric; Hearty, Fred; Blake, Cullen; hide

    2016-01-01

    We describe a detailed radial velocity error budget for the NASA-NSF Extreme Precision Doppler Spectrometer instrument concept NEID (NN-explore Exoplanet Investigations with Doppler spectroscopy). Such an instrument performance budget is a necessity for both identifying the variety of noise sources currently limiting Doppler measurements, and estimating the achievable performance of next generation exoplanet hunting Doppler spectrometers. For these instruments, no single source of instrumental error is expected to set the overall measurement floor. Rather, the overall instrumental measurement precision is set by the contribution of many individual error sources. We use a combination of numerical simulations, educated estimates based on published materials, extrapolations of physical models, results from laboratory measurements of spectroscopic subsystems, and informed upper limits for a variety of error sources to identify likely sources of systematic error and construct our global instrument performance error budget. While natively focused on the performance of the NEID instrument, this modular performance budget is immediately adaptable to a number of current and future instruments. Such an approach is an important step in charting a path towards improving Doppler measurement precisions to the levels necessary for discovering Earth-like planets.

  8. A new infrared Fabry-Pérot-based radial-velocity-reference module for the SPIRou radial-velocity spectrograph

    NASA Astrophysics Data System (ADS)

    Cersullo, Federica; Wildi, François; Chazelas, Bruno; Pepe, Francesco

    2017-05-01

    Context. The field of exoplanet research is moving towards the detection and characterization of habitable planets. These exo-Earths can be easily found around low-mass stars by using either photometric transit or radial-velocity (RV) techniques. In the latter case the gain is twofold because the signal induced by the planet of a given mass is higher due to the more favourable planet-star mass ratio and because the habitable zone lies closer to the star. However, late-type stars emit mainly in the infrared (IR) wavelength range, which calls for IR instruments. Aims: SPIRou is a stable RV IR spectrograph addressing these ambitious scientific objectives. As with any other spectrograph, calibration and drift monitoring is fundamental to achieve high precision. However, the IR domain suffers from a lack of suitable reference spectral sources. Our goal was to build, test and finally operate a Fabry-Pérot-based RV-reference module able to provide the needed spectral information over the full wavelength range of SPIRou. Methods: We adapted the existing HARPS Fabry-Pérot calibrator for operation in the IR domain. After manufacturing and assembly, we characterized the FP RV-module in the laboratory before delivering it to the SPIRou integration site. In particular, we measured finesse, transmittance, and spectral flux of the system. Results: The measured finesse value of F = 12.8 corresponds perfectly to the theoretical value. The total transmittance at peak is of the order of 0.5%, mainly limited by fibre-connectors and interfaces. Nevertheless, the provided flux is in line with the the requirements set by the SPIRou instrument. Although we could test the stability of the system, we estimated it by comparing the SPIRou Fabry-Pérot with the already operating HARPS system and demonstrated a stability of better than 1 m s-1 during a night. Conclusions: Once installed on SPIRou, we will test the full spectral characteristics and stability of the RV-reference module. The

  9. Advanced structural design for precision radial velocity instruments

    NASA Astrophysics Data System (ADS)

    Baldwin, Dan; Szentgyorgyi, Andrew; Barnes, Stuart; Bean, Jacob; Ben-Ami, Sagi; Brennan, Patricia; Budynkiewicz, Jamie; Chun, Moo-Young; Conroy, Charlie; Crane, Jeffrey D.; Epps, Harland; Evans, Ian; Evans, Janet; Foster, Jeff; Frebel, Anna; Gauron, Thomas; Guzman, Dani; Hare, Tyson; Jang, Bi-Ho; Jang, Jeong-Gyun; Jordan, Andres; Kim, Jihun; Kim, Kang-Min; Mendes de Oliveira, Claudia; Lopez-Morales, Mercedes; McCracken, Kenneth; McMuldroch, Stuart; Miller, Joseph; Mueller, Mark; Oh, Jae Sok; Ordway, Mark; Park, Byeong-Gon; Park, Chan; Park, Sung-Joon; Paxson, Charles; Phillips, David; Plummer, David; Podgorski, William; Seifahrt, Andreas; Stark, Daniel; Steiner, Joao; Uomoto, Alan; Walsworth, Ronald; Yu, Young-Sam

    2016-07-01

    The GMT-Consortium Large Earth Finder (G-CLEF) is an echelle spectrograph with precision radial velocity (PRV) capability that will be a first light instrument for the Giant Magellan Telescope (GMT). G-CLEF has a PRV precision goal of 40 cm/sec (10 cm/s for multiple measurements) to enable detection of Earth-like exoplanets in the habitable zones of sun-like stars1. This precision is a primary driver of G-CLEF's structural design. Extreme stability is necessary to minimize image motions at the CCD detectors. Minute changes in temperature, pressure, and acceleration environments cause structural deformations, inducing image motions which degrade PRV precision. The instrument's structural design will ensure that the PRV goal is achieved under the environments G-CLEF will be subjected to as installed on the GMT azimuth platform, including: Millikelvin (0.001 °K) thermal soaks and gradients 10 millibar changes in ambient pressure Changes in acceleration due to instrument tip/tilt and telescope slewing Carbon fiber/cyanate composite was selected for the optical bench structure in order to meet performance goals. Low coefficient of thermal expansion (CTE) and high stiffness-to-weight are key features of the composite optical bench design. Manufacturability and serviceability of the instrument are also drivers of the design. In this paper, we discuss analyses leading to technical choices made to minimize G-CLEF's sensitivity to changing environments. Finite element analysis (FEA) and image motion sensitivity studies were conducted to determine PRV performance under operational environments. We discuss the design of the optical bench structure to optimize stiffness-to-weight and minimize deformations due to inertial and pressure effects. We also discuss quasi-kinematic mounting of optical elements and assemblies, and optimization of these to ensure minimal image motion under thermal, pressure, and inertial loads expected during PRV observations.

  10. EnKF OSSE Experiments Assessing the Impact of HIRAD Wind Speed and HIWRAP Radial Velocity Data on Analysis of Hurricane Karl (2010)

    NASA Technical Reports Server (NTRS)

    Albers, Cerese; Sippel, Jason A.; Braun, Scott A.; Miller, Timothy

    2012-01-01

    Previous studies (e.g., Zhang et al. 2009, Weng et al. 2011) have shown that radial velocity data from airborne and ground-based radars can be assimilated into ensemble Kalman filter (EnKF) systems to produce accurate analyses of tropical cyclone vortices, which can reduce forecast intensity error. Recently, wind speed data from SFMR technology has also been assimilated into the same types of systems and has been shown to improve the forecast intensity of mature tropical cyclones. Two instruments that measure these properties were present during the NASA Genesis and Rapid Intensification Processes (GRIP) field experiment in 2010 which sampled Hurricane Karl, and will next be co-located on the same aircraft for the subsequent NASA HS3 experiment. The High Altitude Wind and Rain Profiling Radar (HIWRAP) is a conically scanning Doppler radar mounted upon NASAs Global Hawk unmanned aerial vehicle, and the usefulness of its radial velocity data for assimilation has not been previously examined. Since the radar scans from above with a fairly large fixed elevation angle, it observes a large component of the vertical wind, which could degrade EnKF analyses compared to analyses with data taken from lesser elevation angles. The NASA Hurricane Imaging Radiometer (HIRAD) is a passive microwave radiometer similar to SFMR, and measures emissivity and retrieves hurricane surface wind speeds and rain rates over a much wider swath. Thus, this study examines the impact of assimilating simulated HIWRAP radial velocity data into an EnKF system, simulated HIRAD wind speed, and HIWRAP+HIRAD with the Weather Research and Forecasting (WRF) model and compares the results to no data assimilation and also to the Truth from which the data was simulated for both instruments.

  11. The Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT): An Open-source Tool for Efficient Fitting of Astrometric and Radial Velocity Data

    NASA Astrophysics Data System (ADS)

    Mede, Kyle; Brandt, Timothy D.

    2017-03-01

    We present the Exoplanet Simple Orbit Fitting Toolbox (ExoSOFT), a new, open-source suite to fit the orbital elements of planetary or stellar-mass companions to any combination of radial velocity and astrometric data. To explore the parameter space of Keplerian models, ExoSOFT may be operated with its own multistage sampling approach or interfaced with third-party tools such as emcee. In addition, ExoSOFT is packaged with a collection of post-processing tools to analyze and summarize the results. Although only a few systems have been observed with both radial velocity and direct imaging techniques, this number will increase, thanks to upcoming spacecraft and ground-based surveys. Providing both forms of data enables simultaneous fitting that can help break degeneracies in the orbital elements that arise when only one data type is available. The dynamical mass estimates this approach can produce are important when investigating the formation mechanisms and subsequent evolution of substellar companions. ExoSOFT was verified through fitting to artificial data and was implemented using the Python and Cython programming languages; it is available for public download at https://github.com/kylemede/ExoSOFT under GNU General Public License v3.

  12. Radial Distribution of Stellar Motions in Gaia DR2

    NASA Astrophysics Data System (ADS)

    Kawata, Daisuke; Baba, Junichi; Ciucǎ, Ioana; Cropper, Mark; Grand, Robert J. J.; Hunt, Jason A. S.; Seabroke, George

    2018-06-01

    By taking advantage of the superb measurements of position and velocity for an unprecedented large number of stars provided in Gaia DR2, we have generated the first maps of the rotation velocity, Vrot, and vertical velocity, Vz, distributions as a function of the Galactocentric radius, Rgal, across a radial range of 5 < Rgal < 12 kpc. In the R - Vrot map, we have identified many diagonal ridge features, which are compared with the location of the spiral arms and the expected outer Lindblad resonance of the Galactic bar. We have detected also radial wave-like oscillations of the peak of the vertical velocity distribution.

  13. Is the four-day rotation of Venus illusory?. [includes systematic error in radial velocities of solar lines reflected from Venus

    NASA Technical Reports Server (NTRS)

    Young, A. T.

    1974-01-01

    An overlooked systematic error exists in the apparent radial velocities of solar lines reflected from regions of Venus near the terminator, owing to a combination of the finite angular size of the Sun and its large (2 km/sec) equatorial velocity of rotation. This error produces an apparent, but fictitious, retrograde component of planetary rotation, typically on the order of 40 meters/sec. Spectroscopic, photometric, and radiometric evidence against a 4-day atmospheric rotation is also reviewed. The bulk of the somewhat contradictory evidence seems to favor slow motions, on the order of 5 m/sec, in the atmosphere of Venus; the 4-day rotation may be due to a traveling wave-like disturbance, not bulk motions, driven by the UV albedo differences.

  14. The three-dimensional steady radial expansion of a viscous gas from a sonic source into a vacuum.

    NASA Technical Reports Server (NTRS)

    Bush, W. B.; Rosen, R.

    1971-01-01

    The three-dimensional steady radial expansion of a viscous, heat-conducting, compressible fluid from a spherical sonic source into a vacuum is analyzed using the Navier-Stokes equations as a basis. It is assumed that the model fluid is a perfect gas having constant specific heats, a constant Prandtl number of order unity, and viscosity coefficients varying as a power of the absolute temperature. Limiting forms for the flow variable solutions are studied for the Reynolds number based on the sonic source conditions, going to infinity and the Newtonian parameter both fixed and going to zero. For the case of the viscosity-temperature exponent between .5 and 1, it is shown that the velocity as well as the pressure approach zero as the radial distance goes to infinity. The formulations of the distinct regions that span the domain extending from the sonic source to the vacuum are presented.

  15. BANYAN. III. Radial velocity, rotation, and X-ray emission of low-mass star candidates in nearby young kinematic groups

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

    Malo, Lison; Artigau, Étienne; Doyon, René

    2014-06-10

    Based on high-resolution spectra obtained with PHOENIX at Gemini-South, CRIRES at VLT-UT1, and ESPaDOnS at the Canada-France-Hawaii Telescope, we present new measurements of the radial and projected rotational velocities of 219 low-mass stars. The target likely membership was initially established using the Bayesian analysis tool recently presented in Malo et al., taking into account only the position, proper motion, and photometry of the stars to assess their membership probability. In the present study, we include radial velocity as an additional input to our analysis, and in doing so we confirm the high membership probability for 130 candidates: 27 in βmore » Pictoris, 22 in Tucana-Horologium, 25 in Columba, 7 in Carina, 18 in Argus and 18 in AB Doradus, and 13 with an ambiguous membership. Our analysis also confirms the membership of 57 stars proposed in the literature. A subsample of 16 candidates was observed at 3 or more epochs, allowing us to discover 6 new spectroscopic binaries. The fraction of binaries in our sample is 25%, consistent with values in the literature. Of the stars in our sample, 20% show projected rotational velocities (vsin i) higher than 30 km s{sup –1} and therefore are considered as fast rotators. A parallax and other youth indicators are still needed to fully confirm the 130 highly probable candidates identified here as new bona fide members. Finally, based on the X-ray emission of bona fide and highly probable group members, we show that for low-mass stars in the 12-120 Myr age range, the X-ray luminosity is an excellent indicator of youth and better than the more traditionally used R {sub X} parameter, the ratio of X-ray to bolometric luminosity.« less

  16. Potential Habitable Zone Exomoon Candidates and Radial Velocity Estimates for Giant Kepler HZ Candidates.

    NASA Astrophysics Data System (ADS)

    Hill, M.; Kane, S.; Kopparapu, R.; Seperuelo Duarte, E.; Gelino, D.; Whittenmyer, R.

    2017-12-01

    The NASA Kepler mission has discovered thousands of new planetary candidates, many of which have been confirmed through follow-up observations. A primary goal of the mission is to determine the occurrence rate of terrestrial-size planets within the Habitable Zone (HZ) of their host stars. A major product of the Habitable Zone Working Group (HZWG) is a list of HZ exoplanet candidates from the Kepler Data Release 24 Q1- Q17 data vetting process [1]. We used a variety of criteria regarding HZ boundaries and planetary sizes to produce complete lists of HZ candidates, including a catalog of 104 candidates within the optimistic HZ. We cross-matched our HZ candidates with the Data Release 25 stellar properties and confirmed planet properties to provide robust stellar parameters and candidate dispositions. We also performed dynamical analysis simulations for multi-planet systems that contain candidates with radii less than two Earth radii as a step toward validation of those systems. From this list we found 39 planet candidates greater than 3 earth radii residing in the Optimistic Habitable Zone of their host star. While giant planets are not favored in the search for eta Earth, they do indicate a potential for large, potentially rocky moons residing in the habitable zone. These giant planets can also provide a potential for a wider range of "habitable" incident flux due to additional energy sources from tidal energy, etc. Thus we analyzed each giant planet, estimating their mass and then calculating the estimated Radial Velocity Semi Amplitudes of each planet for use in follow up observations. We then calculated the planets Hill radius and determined the maximum angular separation of potential moons. This presentation will describe the highlights of the HZ catalog giant planets and the plans for further validation of HZ candidates and follow-up studies. Fig. 1 - Plots both the unconfirmed and confirmed Giant (>3⊕R) Kepler candidates expected Radial Velocity signatures

  17. VizieR Online Data Catalog: Radial velocities of the Be star HR 2142 (Peters+, 2016)

    NASA Astrophysics Data System (ADS)

    Peters, G. J.; Wang, L.; Gies, D. R.; Grundstrom, E. D.

    2016-11-01

    Radial velocity measurements were made using the set of spectra summarized in Table 1. The main focus of this work is a set of 88 high resolution, SWP HIRES FUV spectra acquired over the lifetime of the International Ultraviolet Explorer (IUE) observatory. These were downloaded from MAST and resampled. We also collected a set of 49 LWR and LWP near-UV spectra that were used to inspect the orbital variations in the MgII2796,2803 feature. The UV spectra were supplemented with a large collection of Hα spectra that we secured with the KPNO Coude Feed telescope and that were obtained by amateur astronomers participating in the Be Star Spectra database project (Pollmann 2007IBVS.5778....1P; Neiner et al. 2011AJ....142..149N). (2 data files).

  18. Radial distribution of the flow velocity, efficiency and concentration in a wide HPLC column

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

    Farkas, T.; Sepaniak, M.J.; Guiochon, G.

    1997-08-01

    The use of optical fibers in a fluorescence-detection scheme permits the accurate determination of the radial distribution of the transit time, the column efficiency, and the analyte concentration at the exit of a chromatographic axial-compression column (50 mmID). The results obtained demonstrate that the column is not homogeneous, but suggest a nearly cylindrical distribution of the packing density. The average velocity close to the column wall is 7% lower than along its axis and the HETP 25% higher. The lack of homogeneity of the column packing is another source of band broadening not taken into account in chromatography so far.more » It causes the apparent HETP derived from the conventional elution chromatogram recorded on the bulk eluent to be larger than the local HETP and the band profile to be unsymmetrical with a slight tail reminiscent of kinetic tailing.« less

  19. 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.

  20. “MODAL NOISE” IN SINGLE-MODE FIBERS: A CAUTIONARY NOTE FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS

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

    Halverson, Samuel; Roy, Arpita; Mahadevan, Suvrath

    2015-12-01

    Exploring the use of single-mode fibers (SMFs) in high precision Doppler spectrometers has become increasingly attractive since the advent of diffraction-limited adaptive optics systems on large-aperture telescopes. Spectrometers fed with these fibers can be made significantly smaller than typical “seeing-limited” instruments, greatly reducing cost and overall complexity. Importantly, classical mode interference and speckle issues associated with multi-mode fibers, also known as “modal noise,” are mitigated when using SMFs, which also provide perfect radial and azimuthal image scrambling. However, SMFs do support multiple polarization modes, an issue that is generally ignored for larger-core fibers given the large number of propagation modes.more » Since diffraction gratings used in most high resolution astronomical instruments have dispersive properties that are sensitive to incident polarization changes, any birefringence variations in the fiber can cause variations in the efficiency profile, degrading illumination stability. Here we present a cautionary note outlining how the polarization properties of SMFs can affect the radial velocity (RV) measurement precision of high resolution spectrographs. This work is immediately relevant to the rapidly expanding field of diffraction-limited, extreme precision RV spectrographs that are currently being designed and built by a number of groups.« less

  1. THE RADIAL VELOCITY TATOOINE SEARCH FOR CIRCUMBINARY PLANETS: PLANET DETECTION LIMITS FOR A SAMPLE OF DOUBLE-LINED BINARY STARS-INITIAL RESULTS FROM KECK I/HIRES, SHANE/CAT/HAMSPEC, AND TNG/SARG OBSERVATIONS

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

    Konacki, Maciej; Helminiak, Krzysztof G.; Muterspaugh, Matthew W.

    2009-10-10

    We present preliminary results of the first and on-going radial velocity survey for circumbinary planets. With a novel radial velocity technique employing an iodine absorption cell, we achieve an unprecedented radial velocity (RV) precision of up to 2 m s{sup -1} for double-lined binary stars. The high-resolution spectra collected with the Keck I/Hires, TNG/Sarg, and Shane/CAT/Hamspec telescopes/spectrographs over the years 2003-2008 allow us to derive RVs and compute planet detection limits for 10 double-lined binary stars. For this initial sample of targets, we can rule out planets on dynamically stable orbits with masses as small as approx0.3 to 3 Mmore » {sub Jup} for the orbital periods of up to approx5.3 years. Even though the presented sample of stars is too small to make any strong conclusions, it is clear that the search for circumbinary planets is now technique-wise possible and eventually will provide new constraints for the planet formation theories.« less

  2. Radial Velocities of Subgiant Stars and New Astrophysical Insights into RV Jitter

    NASA Astrophysics Data System (ADS)

    Luhn, Jacob; Bastien, Fabienne; Wright, Jason T.

    2018-01-01

    For nearly 20 years, the California Planet Search (CPS) has simultaneously monitored precise radial velocities and chromospheric activity levels of stars from Keck observatory to search for exoplanets. This sample provides a useful set of stars to better determine the dependence of RV jitter on flicker (which traces surface gravity) first shown in Bastien et al. (2014). We expand upon this initial work by examining a much larger sample of stars covering a much wider range of stellar parameters (effective temperature, surface gravity, and activity, among others). For more than 600 stars, there are enough RV measurements to distinguish this astrophysical jitter from accelerations due to orbital companions. To properly isolate RV jitter from these effects, we must first remove the RV signal due to these companions, including several previously unannounced giant planets around subgiant stars. We highlight some new results from our analysis of the CPS data. A more thorough understanding of the various sources of RV jitter and the underlying stellar phenomena that drive these intrinsic RV variations will enable more precise jitter estimates for RV follow-up targets such as those from K2 or the upcoming TESS mission.

  3. Tangential velocity measurement using interferometric MTI radar

    DOEpatents

    Doerry, Armin W.; Mileshosky, Brian P.; Bickel, Douglas L.

    2006-01-03

    Radar systems use time delay measurements between a transmitted signal and its echo to calculate range to a target. Ranges that change with time cause a Doppler offset in phase and frequency of the echo. Consequently, the closing velocity between target and radar can be measured by measuring the Doppler offset of the echo. The closing velocity is also known as radial velocity, or line-of-sight velocity. Doppler frequency is measured in a pulse-Doppler radar as a linear phase shift over a set of radar pulses during some Coherent Processing Interval (CPI). An Interferometric Moving Target Indicator (MTI) radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity of a target.

  4. Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter

    NASA Astrophysics Data System (ADS)

    Martínez-Arnáiz, R.; Maldonado, J.; Montes, D.; Eiroa, C.; Montesinos, B.

    2010-09-01

    Context. Chromospheric activity produces both photometric and spectroscopic variations that can be mistaken as planets. Large spots crossing the stellar disc can produce planet-like periodic variations in the light curve of a star. These spots clearly affect the spectral line profiles, and their perturbations alter the line centroids creating a radial velocity jitter that might “contaminate” the variations induced by a planet. Precise chromospheric activity measurements are needed to estimate the activity-induced noise that should be expected for a given star. Aims: We obtain precise chromospheric activity measurements and projected rotational velocities for nearby (d ≤ 25 pc) cool (spectral types F to K) stars, to estimate their expected activity-related jitter. As a complementary objective, we attempt to obtain relationships between fluxes in different activity indicator lines, that permit a transformation of traditional activity indicators, i.e., Ca ii H & K lines, to others that hold noteworthy advantages. Methods: We used high resolution (~50 000) echelle optical spectra. Standard data reduction was performed using the IRAF echelle package. To determine the chromospheric emission of the stars in the sample, we used the spectral subtraction technique. We measured the equivalent widths of the chromospheric emission lines in the subtracted spectrum and transformed them into fluxes by applying empirical equivalent width and flux relationships. Rotational velocities were determined using the cross-correlation technique. To infer activity-related radial velocity (RV) jitter, we used empirical relationships between this jitter and the R'_HK index. Results: We measured chromospheric activity, as given by different indicators throughout the optical spectra, and projected rotational velocities for 371 nearby cool stars. We have built empirical relationships among the most important chromospheric emission lines. Finally, we used the measured chromospheric activity

  5. Forecasting the detectability of known radial velocity planets with the upcoming CHEOPS mission

    NASA Astrophysics Data System (ADS)

    Yi, Joo Sung; Chen, Jingjing; Kipping, David

    2018-04-01

    The CHaracterizing ExOPlanets Satellite (CHEOPS) mission is planned for launch next year with a major objective being to search for transits of known radial velocity (RV) planets, particularly those orbiting bright stars. Since the RV method is only sensitive to planetary mass, the radii, transit depths and transit signal-to-noise values of each RV planet are, a priori, unknown. Using an empirically calibrated probabilistic mass-radius relation, forecaster, we address this by predicting a catalogue of homogeneous credible intervals for these three keys terms for 468 planets discovered via RVs. Of these, we find that the vast majority should be detectable with CHEOPS, including terrestrial bodies, if they have the correct geometric alignment. In particular, we predict that 22 mini-Neptunes and 82 Neptune-sized planets would be suitable for detection and that more than 80 per cent of these will have apparent magnitude of V < 10, making them highly suitable for follow-up characterization work. Our work aims to assist the CHEOPS team in scheduling efforts and highlights the great value of quantifiable, statistically robust estimates for upcoming exoplanetary missions.

  6. Blood flow velocity measurement by endovascular Doppler optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Sun, Cuiru; Nolte, Felix; Vuong, Barry; Cheng, Kyle H. Y.; Lee, Kenneth K. C.; Standish, Beau A.; Courtney, Brian; Marotta, Tom R.; Yang, Victor X. D.

    2013-03-01

    Blood flow velocity and volumetric flow measurements are important parameters for assessment of the severity of stenosis and the outcome of interventional therapy. However, feasibility of intravascular flow measurement using a rotational catheter based phase resolved Doppler optical coherence tomography (DOCT) is difficult. Motion artefacts induced by the rotating optical imaging catheter, and the radially dependent noise background of measured Doppler signals are the main challenges encountered. In this study, a custom-made data acquisition system and developed algorithms to remove non-uniform rotational distortion (NURD) induced phase shift artefact by tracking the phase shift observed on catheter sheath. The flow velocity is calculated from Doppler shift obtained by Kasai autocorrelation after motion artefact removal. Blood flow velocity profiles in porcine carotid arteries in vivo were obtained at 100 frames/s with 500 A-lines/frame and DOCT images were taken at 20 frames/s with 2500 A-lines/frame. Time-varying velocity profiles were obtained at an artery branch. Furthermore, the identification of a vein adjacent to the catheterized vessel based on the color Doppler signal was also observed. The absolute measurement of intravascular flow using a rotating fiber catheter can provide insights to different stages of interventional treatment of stenosis in carotid artery.

  7. In vivo visualization method by absolute blood flow velocity based on speckle and fringe pattern using two-beam multipoint laser Doppler velocimetry

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

    Kyoden, Tomoaki, E-mail: kyouden@nc-toyama.ac.jp; Naruki, Shoji; Akiguchi, Shunsuke

    Two-beam multipoint laser Doppler velocimetry (two-beam MLDV) is a non-invasive imaging technique able to provide an image of two-dimensional blood flow and has potential for observing cancer as previously demonstrated in a mouse model. In two-beam MLDV, the blood flow velocity can be estimated from red blood cells passing through a fringe pattern generated in the skin. The fringe pattern is created at the intersection of two beams in conventional LDV and two-beam MLDV. Being able to choose the depth position is an advantage of two-beam MLDV, and the position of a blood vessel can be identified in a three-dimensionalmore » space using this technique. Initially, we observed the fringe pattern in the skin, and the undeveloped or developed speckle pattern generated in a deeper position of the skin. The validity of the absolute velocity value detected by two-beam MLDV was verified while changing the number of layers of skin around a transparent flow channel. The absolute velocity value independent of direction was detected using the developed speckle pattern, which is created by the skin construct and two beams in the flow channel. Finally, we showed the relationship between the signal intensity and the fringe pattern, undeveloped speckle, or developed speckle pattern based on the skin depth. The Doppler signals were not detected at deeper positions in the skin, which qualitatively indicates the depth limit for two-beam MLDV.« less

  8. Absolute dimensions and masses of eclipsing binaries. V. IQ Persei

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

    Lacy, C.H.; Frueh, M.L.

    1985-08-01

    New photometric and spectroscopic observations of the 1.7 day eclipsing binary IQ Persei (B8 + A6) have been analyzed to yield very accurate fundamental properties of the system. Reticon spectroscopic observations obtained at McDonald Observatory were used to determine accurate radial velocities of both stars in this slightly eccentric large light-ratio binary. A new set of VR light curves obtained at McDonald Observatory were analyzed by synthesis techniques, and previously published UBV light curves were reanalyzed to yield accurate photometric orbits. Orbital parameters derived from both sets of photometric observations are in excellent agreement. The absolute dimensions, masses, luminosities, andmore » apsidal motion period (140 yr) derived from these observations agree well with the predictions of theoretical stellar evolution models. The A6 secondary is still very close to the zero-age main sequence. The B8 primary is about one-third of the way through its main-sequence evolution. 27 references.« less

  9. Absolute proper motions to B approximately 22.5: Evidence for kimematical substructure in halo field stars

    NASA Technical Reports Server (NTRS)

    Majewski, Steven R.; Munn, Jeffrey A.; Hawley, Suzanne L.

    1994-01-01

    Radial velocities have been obtained for six of nine stars identified on the basis of similar distances and common, extreme transverse velocities in the proper motion survey of Majewski (1992) as a candidate halo moving group at the north Galactic pole. These radial velocities correspond to velocities perpendicular to the Galactic plane which span the range -48 +/- 21 to -128 +/- 9 km/sec (but a smaller range, -48 +/- 21 to -86 +/- 19 km/sec, when only our own measurements are considered), significantly different than the expected distribution, with mean 0 km/sec, for a random sample of either halo or thick disk stars. The probability of picking such a set of radial velocities at random is less than 1%. Thus the radial velocity data support the hypothesis that these stars constitute part of a halo moving group or star stream at a distance of approximately 4-5 kpc above the Galactic plane. If real, this moving group is evidence for halo phase space substructure which may be the fossil remains of a destroyed globular cluster, Galactic satellite, or Searle & Zinn (1978) 'fragment.'

  10. MULTI-COMPONENT ANALYSIS OF POSITION-VELOCITY CUBES OF THE HH 34 JET

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

    Rodriguez-Gonzalez, A.; Esquivel, A.; Raga, A. C.

    We present an analysis of H{alpha} spectra of the HH 34 jet with two-dimensional spectral resolution. We carry out multi-Gaussian fits to the spatially resolved line profiles and derive maps of the intensity, radial velocity, and velocity width of each of the components. We find that close to the outflow source we have three components: a high (negative) radial velocity component with a well-collimated, jet-like morphology; an intermediate velocity component with a broader morphology; and a positive radial velocity component with a non-collimated morphology and large linewidth. We suggest that this positive velocity component is associated with jet emission scatteredmore » in stationary dust present in the circumstellar environment. Farther away from the outflow source, we find only two components (a high, negative radial velocity component, which has a narrower spatial distribution than an intermediate velocity component). The fitting procedure was carried out with the new AGA-V1 code, which is available online and is described in detail in this paper.« less

  11. The VMC survey - XXIII. Model fitting of light and radial velocity curves of Small Magellanic Cloud classical Cepheids

    NASA Astrophysics Data System (ADS)

    Marconi, M.; Molinaro, R.; Ripepi, V.; Cioni, M.-R. L.; Clementini, G.; Moretti, M. I.; Ragosta, F.; de Grijs, R.; Groenewegen, M. A. T.; Ivanov, V. D.

    2017-04-01

    We present the results of the χ2 minimization model fitting technique applied to optical and near-infrared photometric and radial velocity data for a sample of nine fundamental and three first overtone classical Cepheids in the Small Magellanic Cloud (SMC). The near-infrared photometry (JK filters) was obtained by the European Southern Observatory (ESO) public survey 'VISTA near-infrared Y, J, Ks survey of the Magellanic Clouds system' (VMC). For each pulsator, isoperiodic model sequences have been computed by adopting a non-linear convective hydrodynamical code in order to reproduce the multifilter light and (when available) radial velocity curve amplitudes and morphological details. The inferred individual distances provide an intrinsic mean value for the SMC distance modulus of 19.01 mag and a standard deviation of 0.08 mag, in agreement with the literature. Moreover, the intrinsic masses and luminosities of the best-fitting model show that all these pulsators are brighter than the canonical evolutionary mass-luminosity relation (MLR), suggesting a significant efficiency of core overshooting and/or mass-loss. Assuming that the inferred deviation from the canonical MLR is only due to mass-loss, we derive the expected distribution of percentage mass-loss as a function of both the pulsation period and the canonical stellar mass. Finally, a good agreement is found between the predicted mean radii and current period-radius (PR) relations in the SMC available in the literature. The results of this investigation support the predictive capabilities of the adopted theoretical scenario and pave the way for the application to other extensive data bases at various chemical compositions, including the VMC Large Magellanic Cloud pulsators and Galactic Cepheids with Gaia parallaxes.

  12. Box Tomography: first application to the imaging of upper-mantle shear velocity and radial anisotropy structure beneath the North American continent

    NASA Astrophysics Data System (ADS)

    Clouzet, P.; Masson, Y.; Romanowicz, B.

    2018-06-01

    The EarthScope Transpotable Array (TA) deployment provides dense array coverage throughout the continental United States and with it, the opportunity for high-resolution 3-D seismic velocity imaging of the stable part of the North American (NA) upper mantle. Building upon our previous long-period waveform tomographic modeling, we present a higher resolution 3-D isotropic and radially anisotropic shear wave velocity model of the NA lithosphere and asthenosphere. The model is constructed using a combination of teleseismic and regional waveforms down to 40 s period and wavefield computations are performed using the spectral element method both for regional and teleseismic data. Our study is the first tomographic application of `Box Tomography', which allows us to include teleseismic events in our inversion, while computing the teleseismic wavefield only once, thus significantly reducing the numerical computational cost of several iterations of the regional inversion. We confirm the presence of high-velocity roots beneath the Archean part of the continent, reaching 200-250 km in some areas, however the thickness of these roots is not everywhere correlated to the crustal age of the corresponding cratonic province. In particular, the lithosphere is thick (˜250 km) in the western part of the Superior craton, while it is much thinner (˜150 km) in its eastern part. This may be related to a thermomechanical erosion of the cratonic root due to the passage of the NA plate over the Great Meteor hotspot during the opening of the Atlantic ocean 200-110 Ma. Below the lithosphere, an upper-mantle low-velocity zone (LVZ) is present everywhere under the NA continent, even under the thickest parts of the craton, although it is less developed there. The depth of the minimum in shear velocity has strong lateral variations, whereas the bottom of the LVZ is everywhere relatively flat around 270-300 km depth, with minor undulations of maximum 30 km that show upwarping under the thickest

  13. The warm and cold neutral phase in the local interstellar medium at absolute value of B greater than or equal to 10 deg

    NASA Astrophysics Data System (ADS)

    Poppel, W. G. L.; Marronetti, P.; Benaglia, P.

    1994-07-01

    We made a systematic separation of both the neutral phases using the atlases of 21-cm profiles of Heiles & Habing (1974) and Colomb et al. (1980), complemented with other data. First, we fitted the emission of the warm neutral medium (WNM) by means of a broad Gaussian curve (velocity dispersion sigma approximately 10-14 km/s). We derived maps of the column densities NWH and the radial velocities VW of the WNM. Its overall distribution appears to be very inhomogeneous with a large hole in the range b greater than or equal to +50 deg. However, if the hole is excluded, the mean latitude-profiles admit a rough cosec absolute value of b-fit common to both hemispheres. A kinematical analysis of VW for the range 10 deg less than or equal to absolute value of b less than or equal to 40 deg indicates a mean differential rotation with a small nodal deviation. At absolute value of b greater than 50 deg VW is negative, with larger values and discontinuities in the north. On the mean, sigma increases for absolute value of b decreasing, as is expected from differential rotation. From a statistical study of the peaks of the residual profiles we derived some characteristics of the cold neutral medium (CNM). The latter is generally characterized by a single component of sigma approximately 2-6 km/s. Additionally we derived the sky-distribution of the column densities NCH and the radial velocities VC of the CNM within bins of 1.2 deg sec b x 1 deg in l, b. Furthermore, we focused on the characteristics of Linblad's feature A of cool gas by considering the narrow ridge of local H I, which appears in the b-V contour maps at fixed l (e.g. Schoeber 1976). The ridge appears to be the main component of the CNM. We suggest a scenario for the formulation and evolution of the Gould belt system of stars and gas on the basis of an explosive event within a shingle of cold dense gas tilted to the galactic plane. The scenario appears to be consistent with the results found for both the neutral

  14. Radial k-t SPIRiT: autocalibrated parallel imaging for generalized phase-contrast MRI.

    PubMed

    Santelli, Claudio; Schaeffter, Tobias; Kozerke, Sebastian

    2014-11-01

    To extend SPIRiT to additionally exploit temporal correlations for highly accelerated generalized phase-contrast MRI and to compare the performance of the proposed radial k-t SPIRiT method relative to frame-by-frame SPIRiT and radial k-t GRAPPA reconstruction for velocity and turbulence mapping in the aortic arch. Free-breathing navigator-gated two-dimensional radial cine imaging with three-directional multi-point velocity encoding was implemented and fully sampled data were obtained in the aortic arch of healthy volunteers. Velocities were encoded with three different first gradient moments per axis to permit quantification of mean velocity and turbulent kinetic energy. Velocity and turbulent kinetic energy maps from up to 14-fold undersampled data were compared for k-t SPIRiT, frame-by-frame SPIRiT, and k-t GRAPPA relative to the fully sampled reference. Using k-t SPIRiT, improvements in magnitude and velocity reconstruction accuracy were found. Temporally resolved magnitude profiles revealed a reduction in spatial blurring with k-t SPIRiT compared with frame-by-frame SPIRiT and k-t GRAPPA for all velocity encodings, leading to improved estimates of turbulent kinetic energy. k-t SPIRiT offers improved reconstruction accuracy at high radial undersampling factors and hence facilitates the use of generalized phase-contrast MRI for routine use. Copyright © 2013 Wiley Periodicals, Inc.

  15. The SDSS-III DR12 MARVELS radial velocity data release: the first data release from the multiple object Doppler exoplanet survey

    NASA Astrophysics Data System (ADS)

    Ge, Jian; Thomas, Neil B.; Li, Rui; Senan Seieroe Grieves, Nolan; Ma, Bo; de Lee, Nathan M.; Lee, Brian C.; Liu, Jian; Bolton, Adam S.; Thakar, Aniruddha R.; Weaver, Benjamin; SDSS-Iii Marvels Team

    2015-01-01

    We present the first data release from the SDSS-III Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS) through the SDSS-III DR12. The data include 181,198 radial velocity (RV) measurements for a total of 5520 different FGK stars with V~7.6-12, of which more than 80% are dwarfs and subdwarfs while remainders are GK giants, among a total of 92 fields nearly randomly spread out over the entire northern sky taken with a 60-object MARVELS dispersed fixed-delay interferometer instrument over four years (2008-2012). There were 55 fields with a total of 3300 FGK stars which had 14 or more observations over about 2-year survey window. The median number of observations for these plates is 27 RV measurements. This represents the largest homogeneous sample of precision RV measurements of relatively bright stars. In this first released data, a total of 18 giant planet candidates, 16 brown dwarfs, and over 500 binaries with additional 96 targets having RV variability indicative of a giant planet companion are reported. The released data were produced by the MARVELS finalized 1D pipeline. We will also report preliminary statistical results from the MARVELS 2D data pipeline which has produced a median RV precision of ~30 m/s for stable stars.

  16. Radial Velocity and Metallicity Determinations for Remote Globular Clusters in M31 and M33

    NASA Astrophysics Data System (ADS)

    Ferguson, Annette; Barmby, Pauline; Cote, Pat; Harris, Bill; Huxor, Avon; Mackey, Dougal; Puzia, Thomas

    2009-08-01

    We propose to determine radial velocities and metallicities for a sample of ~ 20 remote globular clusters (GCs) which we have discovered in the outer halos of the Local Group galaxies M31 and M33. Most of these objects have been uncovered in the course of the PAndAs survey, an international collaboration which is using CFHT/MegaPrime to map more than 300 square degrees in the g and i bands around M31 and M33. The target clusters, all of which have been identified from high- quality imaging (typically ≲ 0.8'' seeing), lie at projected radii of up to 130 kpc from M31 and 30 kpc from M33 and thus lie significantly beyond all previously-known GCs in these systems. Rather intriguingly, many of the new discoveries exhibit either possible associations with halo tidal streams, or show unusual spatial anisotropies with respect to their host galaxy. Velocity and metallicity data for these objects will provide a detailed characterization of the ensemble properties of the outer halo GC populations, and, through the search for kinematic and metallicity correlations within groups of GCs, help determine what fraction of these objects can be attributed to either late or ongoing accretion events. Ultimately, these data will also provide a basis for improved dynamical mass estimates of both galaxies.

  17. On the Feasibility of Intense Radial Velocity Surveys for Earth-twin Discoveries

    NASA Astrophysics Data System (ADS)

    Hall, Richard D.; Thompson, Samantha J.; Handley, Will; Queloz, Didier

    2018-06-01

    This work assesses the potential capability of the next generation of high-precision Radial Velocity (RV) instruments for Earth-twin exoplanet detection. From the perspective of the importance of data sampling, the Terra Hunting Experiment aims to do this through an intense series of nightly RV observations over a long baseline on a carefully selected target list, via the brand-new instrument HARPS3. This paper describes an end-to-end simulation of generating and processing such data to help us better understand the impact of uncharacterised stellar noise in the recovery of Earth-mass planets with orbital periods of the order of many months. We consider full Keplerian systems, realistic simulated stellar noise, instrument white noise, and location-specific weather patterns for our observation schedules. We use Bayesian statistics to assess various planetary models fitted to the synthetic data, and compare the successful planet recovery of the Terra Hunting Experiment schedule with a typical reference survey. We find that the Terra Hunting Experiment can detect Earth-twins in the habitable zones of solar-type stars, in single and multi-planet systems, and in the presence of stellar signals. Also that it out-performs a typical reference survey on accuracy of recovered parameters, and that it performs comparably to an uninterrupted space-based schedule.

  18. Quantification of absolute blood velocity using LDA

    NASA Astrophysics Data System (ADS)

    Borozdova, M. A.; Fedosov, I. V.; Tuchin, V. V.

    2018-04-01

    We developed novel schematics of a Laser Doppler anemometer where measuring volume is comparable with the red blood cell (RBC) size and a small period of interference fringes improves device resolution. The technique was used to estimate Doppler frequency shift at flow velocity measurements. It has been shown that technique is applicable for measurements in whole blood.

  19. High-Contrast Imaging of Intermediate-Mass Giants with Long-Term Radial Velocity Trends

    NASA Technical Reports Server (NTRS)

    Ryu, Tsuguru; Sato, Bun'ei; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; hide

    2016-01-01

    A radial velocity (RV) survey for intermediate-mass giants has been operated for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to gamma Hya B (0.61+0.12 -0.14 Stellar Mass), HD 5608 B (0.10 +/- 0.01 Stellar Mass), and HD 109272 B (0.28 +/- 0.06 Stellar Mass). For the remaining targets( Dra, 18 Del, and HD 14067) we exclude companions more massive than 30-60 M(sub Jup) at projected separations of 1''-7''. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets Dra b, HD 5608 b, and HD 14067 b.

  20. High-contrast Imaging of Intermediate-mass Giants with Long-term Radial Velocity Trends

    NASA Astrophysics Data System (ADS)

    Ryu, Tsuguru; Sato, Bun'ei; Kuzuhara, Masayuki; Narita, Norio; Takahashi, Yasuhiro H.; Uyama, Taichi; Kudo, Tomoyuki; Kusakabe, Nobuhiko; Hashimoto, Jun; Omiya, Masashi; Harakawa, Hiroki; Abe, Lyu; Ando, Hiroyasu; Brandner, Wolfgang; Brandt, Timothy D.; Carson, Joseph C.; Currie, Thayne; Egner, Sebastian; Feldt, Markus; Goto, Miwa; Grady, Carol A.; Guyon, Olivier; Hayano, Yutaka; Hayashi, Masahiko; Hayashi, Saeko S.; Hełminiak, Krzysztof G.; Henning, Thomas; Hodapp, Klaus W.; Ida, Shigeru; Ishii, Miki; Itoh, Yoichi; Iye, Masanori; Izumiura, Hideyuki; Janson, Markus; Kambe, Eiji; Kandori, Ryo; Knapp, Gillian R.; Kokubo, Eiichiro; Kwon, Jungmi; Matsuo, Taro; Mayama, Satoshi; McElwain, Michael W.; Mede, Kyle; Miyama, Shoken; Morino, Jun-Ichi; Moro-Martin, Amaya; Nishimura, Tetsuo; Pyo, Tae-Soo; Serabyn, Eugene; Suenaga, Takuya; Suto, Hiroshi; Suzuki, Ryuji; Takami, Michihiro; Takato, Naruhisa; Takeda, Yoichi; Terada, Hiroshi; Thalmann, Christian; Turner, Edwin L.; Watanabe, Makoto; Wisniewski, John; Yamada, Toru; Yoshida, Michitoshi; Takami, Hideki; Usuda, Tomonori; Tamura, Motohide

    2016-07-01

    A radial velocity (RV) survey for intermediate-mass giants has been in operation for over a decade at Okayama Astrophysical Observatory (OAO). The OAO survey has revealed that some giants show long-term linear RV accelerations (RV trends), indicating the presence of outer companions. Direct-imaging observations can help clarify what objects generate these RV trends. We present the results of high-contrast imaging observations of six intermediate-mass giants with long-term RV trends using the Subaru Telescope and HiCIAO camera. We detected co-moving companions to γ Hya B ({0.61}-0.14+0.12{M}⊙ ), HD 5608 B (0.10+/- 0.01{M}⊙ ), and HD 109272 B (0.28+/- 0.06{M}⊙ ). For the remaining targets (ι Dra, 18 Del, and HD 14067), we exclude companions more massive than 30-60 M Jup at projected separations of 1″-7″. We examine whether these directly imaged companions or unidentified long-period companions can account for the RV trends observed around the six giants. We find that the Kozai mechanism can explain the high eccentricity of the inner planets ι Dra b, HD 5608 b, and HD 14067 b.

  1. Shallow crustal radial anisotropy beneath the Tehran basin of Iran from seismic ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Shirzad, Taghi; Shomali, Z. Hossein

    2014-06-01

    We studied the shear wave velocity structure and radial anisotropy beneath the Tehran basin by analyzing the Rayleigh wave and Love wave empirical Green's functions obtained from cross-correlation of seismic ambient noise. Approximately 199 inter-station Rayleigh and Love wave empirical Green's functions with sufficient signal-to-noise ratios extracted from 30 stations with various sensor types were used for phase velocity dispersion analysis of periods ranging from 1 to 7 s using an image transformation analysis technique. Dispersion curves extracted from the phase velocity maps were inverted based on non-linear damped least squares inversion method to obtain a quasi-3D model of crustal shear wave velocities. The data used in this study provide an unprecedented opportunity to resolve the spatial distribution of radial anisotropy within the uppermost crust beneath the Tehran basin. The quasi-3D shear wave velocity model obtained in this analysis delineates several distinct low- and high-velocity zones that are generally separated by geological boundaries. High-shear-velocity zones are located primarily around the mountain ranges and extend to depths of 2.0 km, while the low-shear-velocity zone is located near regions with sedimentary layers. In the shallow subsurface, our results indicate strong radial anisotropy with negative magnitude (VSV > VSH) primarily associated with thick sedimentary deposits, reflecting vertical alignment of cracks. With increasing depth, the magnitude of the radial anisotropy shifts from predominantly negative (less than -10%) to predominantly positive (greater than 5%). Our results show a distinct change in radial anisotropy between the uppermost sedimentary layer and the bedrock.

  2. V1327 Aquilae: A New RR Lyrae variable with an extremely high radial velocity

    NASA Astrophysics Data System (ADS)

    Galeev, A. I.; Bikmaev, I. F.; Borisov, N. V.; Zhuchkov, R. Ya.; Shimanskii, V. V.; Khabibullina, M. L.; Sakhibullin, N. A.

    2008-07-01

    We have carried out photometry and spectroscopy of the star V1327 Aql ( R = 16 m ) as part of our program of observations of poorly studied cataclysmic variables using the 1.5-m optical Russian—Turkish telescope (RTT-150, Turkey) and the 6-m telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. After analyzing our photometry, we have re-classified the variable as an RR Lyrae star. Our BV R photometry during 10 nights reveals brightness variations with the period 12h49m, with the B, V, and R amplitudes being 1.36 m , 1.13 m , and 1.11 m , respectively. We derived the first estimates of the star’s atmospheric parameters from our moderate-resolution spectra: T eff = 6280 K, log g = 3.3, [M/H] = -1.05. The extremely high radial velocity of the star’s motion ( V R = -470 km/s) and the star’s large distances to the Galactic center (13.1 kpc) and disk (4.2 kpc) testify to a probable extragalactic origin of this object.

  3. H0, q0 and the local velocity field. [Hubble and deceleration constants in Big Bang expansion

    NASA Technical Reports Server (NTRS)

    Sandage, A.; Tammann, G. A.

    1982-01-01

    An attempt is made to find a systematic deviation from linearity for distances that are under the control of the Virgo cluster, and to determine the value of the mean random motion about the systematic flow, in order to improve the measurement of the Hubble and the deceleration constants. The velocity-distance relation for large and intermediate distances is studied, and type I supernovae are calibrated relatively as distance indicators and absolutely to obtain a new value for the Hubble constant. Methods of determining the deceleration constant are assessed, including determination from direct measurement, mean luminosity density, virgocentric motion, and the time scale test. The very local velocity field is investigated, and a solution is preferred with a random peculiar radial velocity of very nearby field galaxies of 90-100 km/s, and a Virgocentric motion of the local group of 220 km/s, leading to an underlying expansion rate of 55, in satisfactory agreement with the global value.

  4. Suppression of fiber modal noise induced radial velocity errors for bright emission-line calibration sources

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

    Mahadevan, Suvrath; Halverson, Samuel; Ramsey, Lawrence

    2014-05-01

    Modal noise in optical fibers imposes limits on the signal-to-noise ratio (S/N) and velocity precision achievable with the next generation of astronomical spectrographs. This is an increasingly pressing problem for precision radial velocity spectrographs in the near-infrared (NIR) and optical that require both high stability of the observed line profiles and high S/N. Many of these spectrographs plan to use highly coherent emission-line calibration sources like laser frequency combs and Fabry-Perot etalons to achieve precision sufficient to detect terrestrial-mass planets. These high-precision calibration sources often use single-mode fibers or highly coherent sources. Coupling light from single-mode fibers to multi-mode fibersmore » leads to only a very low number of modes being excited, thereby exacerbating the modal noise measured by the spectrograph. We present a commercial off-the-shelf solution that significantly mitigates modal noise at all optical and NIR wavelengths, and which can be applied to spectrograph calibration systems. Our solution uses an integrating sphere in conjunction with a diffuser that is moved rapidly using electrostrictive polymers, and is generally superior to most tested forms of mechanical fiber agitation. We demonstrate a high level of modal noise reduction with a narrow bandwidth 1550 nm laser. Our relatively inexpensive solution immediately enables spectrographs to take advantage of the innate precision of bright state-of-the art calibration sources by removing a major source of systematic noise.« less

  5. The SDSS-III Multi-object Apo Radial-velocity Exoplanet Large-area Survey

    NASA Astrophysics Data System (ADS)

    Ge, Jian; Mahadevan, S.; Lee, B.; Wan, X.; Zhao, B.; van Eyken, J.; Kane, S.; Guo, P.; Ford, E. B.; Agol, E.; Gaudi, S.; Fleming, S.; Crepp, J.; Cohen, R.; Groot, J.; Galvez, M.; Liu, J.; Ford, H.; Schneider, D.; Seager, S.; Hawley, S. L.; Weinberg, D.; Eisenstein, D.

    2007-12-01

    As part of SDSS-III survey in 2008-2014, the Multi-object APO Radial-Velocity Exoplanet Large-area Survey (MARVELS) will conduct the largest ground-based Doppler planet survey to date using the SDSS telescope and new generation multi-object Doppler instruments with 120 object capability and 10-20 m/s Doppler precision. The baseline survey plan is to monitor a total of 11,000 V=8-12 stars ( 10,000 main sequence stars and 1000 giant stars) over 800 square degrees over the 6 years. The primary goal is to produce a large, statistically well defined sample of giant planets ( 200) with a wide range of masses ( 0.2-10 Jupiter masses) and orbits (1 day-2 years) drawn from a large of host stars with a diverse set of masses, compositions, and ages for studying the diversity of extrasolar planets and constraining planet formation, migration & dynamical evolution of planetary systems. The survey data will also be used for providing a statistical sample for theoretical comparison and discovering rare systems and identifying signposts for lower-mass or more distant planets. Early science results from the pilot program will be reported. We would like to thank the SDSS MC for allocation of the telescope time and the W.M. Keck Foundation, NSF, NASA and UF for support.

  6. A technique for generating shear waves in cylindrical shells under radial impact

    NASA Technical Reports Server (NTRS)

    Blum, A.; Mortimer, R. W.; Rose, J. L.

    1974-01-01

    Experimental techniques are developed to study and measure the shear-wave velocity in an aluminum cylindrical shell subjected to a radial impact. The radial impact is obtained by exploding an electrical detonator inserted in plastic plugs mounted on the end of the shell. Strain gages, mounted on the outside surface of the shell at various axial locations, are used to obtain oscilloscope traces from which the shear-wave velocity can be calculated.

  7. The absolute dynamic ocean topography (ADOT)

    NASA Astrophysics Data System (ADS)

    Bosch, Wolfgang; Savcenko, Roman

    The sea surface slopes relative to the geoid (an equipotential surface) basically carry the in-formation on the absolute velocity field of the surface circulation. Pure oceanographic models may remain unspecific with respect to the absolute level of the ocean topography. In contrast, the geodetic approach to estimate the ocean topography as difference between sea level and the geoid gives by definition an absolute dynamic ocean topography (ADOT). This approach requires, however, a consistent treatment of geoid and sea surface heights, the first being usually derived from a band limited spherical harmonic series of the Earth gravity field and the second observed with much higher spectral resolution by satellite altimetry. The present contribution shows a procedure for estimating the ADOT along the altimeter profiles, preserving as much sea surface height details as the consistency w.r.t. the geoid heights will allow. The consistent treatment at data gaps and the coast is particular demanding and solved by a filter correction. The ADOT profiles are inspected for their innocent properties towards the coast and compared to external estimates of the ocean topography or the velocity field of the surface circulation as derived, for example, by ARGO floats.

  8. THE BROWN DWARF KINEMATICS PROJECT (BDKP). IV. RADIAL VELOCITIES OF 85 LATE-M AND L DWARFS WITH MagE

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

    Burgasser, Adam J.; Logsdon, Sarah E.; Gagné, Jonathan

    2015-09-15

    Radial velocity measurements are presented for 85 late M- and L-type very low-mass stars and brown dwarfs obtained with the Magellan Echellette spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2–3 km s{sup −1}, and combined these with astrometric and spectrophotometric data to calculate UVW velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2 ± 0.2 Gyr for sources within 20 pc. We find signficantly different kinematic ages between late-M dwarfsmore » (4.0 ± 0.2 Gyr) and L dwarfs (6.5 ± 0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric U velocity distribution with a net inward flow, similar to gradients recently detected in local stellar samples. Simulations incorporating brown dwarf evolution and Galactic orbital dynamics are unable to reproduce the velocity asymmetry, suggesting non-axisymmetric perturbations or two distinct L dwarf populations. We also find the L dwarfs to have a kinematic age-activity correlation similar to more massive stars. We identify several sources with low surface gravities, and two new substellar candidate members of nearby young moving groups: the astrometric binary DENIS J08230313–4912012AB, a low-probability member of the β Pictoris Moving Group; and 2MASS J15104786–2818174, a moderate-probability member of the 30–50 Myr Argus Association.« less

  9. Production, Outflow Velocity, and Radial Distribution of H2O and OH in the Coma of Comet C/1995 O1 [Hale-Bopp] from Wide Field Imaging of OH

    NASA Technical Reports Server (NTRS)

    Harris, Walter M.; Scherb, Frank; Mierkiewicz, Edwin; Oliversen, Ronald; Morgenthaler, Jeffrey

    2001-01-01

    Observations of OH are a useful proxy of the water production rate (Q(sub H2O)) and outflow velocity (V(sub out)) in comets. We use wide field images taken on 03/28/1997 and 04/08/1997 that capture the entire scale length of the OH coma of comet C/1995O1 (Hale-Bopp) to obtain Q(sub H2O) from the model-independent method of aperture summation. We also extract the radial brightness profile of OH 3080 angstroms out to cometocentric distances of up to 10(exp 6) km using an adaptive ring summation algorithm. Radial profiles are obtained as azimuthal averages and in quadrants covering different position angles relative to the comet-Sun line. These profiles are fit using both fixed and variable velocity two-component spherical expansion models to determine VOH with increasing distance from the nucleus. The OH coma of Hale-Bopp was more spatially extended than in previous comets, and this extension is best matched by a variable acceleration of H2O and OH that acted across the entire coma, but was strongest within 1-2 x 10(exp 4) km from the nucleus. This acceleration led to VOH at 10(exp 6) km that was 2-3 times greater than that obtained from a 1P/Halleytype comet at 1 AU, a result that is consistent with gas-kinetic models, extrapolation from previous observations of OH in comets with Q(sub H2O) > 10(exp 29)/s, and radio measurements of the outer coma Hale-Bopp OH velocity profile. When the coma is broken down by quadrant, we find an azimuthal asymmetry in the radial distribution that is characterized by an increase in the spatial extent of OH in the region between the orbit-trailing and anti-sunward directions. Model fits to this area and comparison with radio OH measurements suggest greater acceleration in this region, with VOH UP to 1.5 times greater at 10(exp 6) km radial distance than elsewhere in the coma.

  10. Predicted space motions for hypervelocity and runaway stars: proper motions and radial velocities for the Gaia Era

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

    Kenyon, Scott J.; Brown, Warren R.; Geller, Margaret J.

    We predict the distinctive three-dimensional space motions of hypervelocity stars (HVSs) and runaway stars moving in a realistic Galactic potential. For nearby stars with distances less than 10 kpc, unbound stars are rare; proper motions alone rarely isolate bound HVSs and runaways from indigenous halo stars. At large distances of 20-100 kpc, unbound HVSs are much more common than runaways; radial velocities easily distinguish both from indigenous halo stars. Comparisons of the predictions with existing observations are encouraging. Although the models fail to match observations of solar-type HVS candidates from SEGUE, they agree well with data for B-type HVS andmore » runaways from other surveys. Complete samples of g ≲ 20 stars with Gaia should provide clear tests of formation models for HVSs and runaways and will enable accurate probes of the shape of the Galactic potential.« less

  11. A search for solar wind velocity changes between 0.7 and 1 AU

    NASA Technical Reports Server (NTRS)

    Intriligator, D. S.; Neugebauer, M.

    1975-01-01

    Observations are presented concerning the radial variations of the solar wind velocity between 0.7 and 1 AU in late 1968 and early 1969. The observations were made with instruments carried by Pioneer 9 and the earth-orbiting satellite OGO 5. The Pioneer and OGO velocity measurements are compared. It is found that the same basic solar wind velocity structure was seen at both spacecraft. No statistically significant dependence of average velocity on the radial distance from the sun could be observed.

  12. GIARPS: the unique VIS-NIR high precision radial velocity facility in this world

    NASA Astrophysics Data System (ADS)

    Claudi, R.; Benatti, S.; Carleo, I.; Ghedina, A.; Molinari, E.; Oliva, E.; Tozzi, A.; Baruffolo, A.; Cecconi, M.; Cosentino, R.; Fantinel, D.; Fini, L.; Ghinassi, F.; Gonzalez, M.; Gratton, R.; Guerra, J.; Harutyunyan, A.; Hernandez, N.; Iuzzolino, M.; Lodi, M.; Malavolta, L.; Maldonado, J.; Micela, G.; Sanna, N.; Sanjuan, J.; Scuderi, S.; Sozzetti, A.; Pérez Ventura, H.; Diaz Marcos, H.; Galli, A.; Gonzalez, C.; Riverol, L.; Riverol, C.

    2016-08-01

    GIARPS (GIAno and haRPS) is a project devoted to have on the same focal station of the Telescopio Nazionale Galileo (TNG) both the high resolution spectrographs HARPS-N (VIS) and GIANO (NIR) working simultaneously. This could be considered the first and unique worldwide instrument providing cross-dispersed echelle spectroscopy at a high resolution (R=115,000 in the visual and R=50,000 in the IR) and over in a wide spectral range (0.383 - 2.45 μm) in a single exposure. The science case is very broad, given the versatility of such an instrument and the large wavelength range. A number of outstanding science cases encompassing mainly extra-solar planet science starting from rocky planet search and hot Jupiters, atmosphere characterization can be considered. Furthermore both instrument can measure high precision radial velocity by means the simultaneous thorium technique (HARPS - N) and absorbing cell technique (GIANO) in a single exposure. Other science cases are also possible. Young stars and proto- planetary disks, cool stars and stellar populations, moving minor bodies in the solar system, bursting young stellar objects, cataclysmic variables and X-ray binary transients in our Galaxy, supernovae up to gamma-ray bursts in the very distant and young Universe, can take advantage of the unicity of this facility both in terms of contemporaneous wide wavelength range and high resolution spectroscopy.

  13. Revised FORTRAN program for calculating velocities and streamlines on the hub-shroud midchannel stream surface of an axial-, radial-, or mixed-flow turbomachine or annular duct. 2: Programmer's manual

    NASA Technical Reports Server (NTRS)

    Katsanis, T.; Mcnally, W. D.

    1977-01-01

    A FORTRAN IV computer program has been developed that obtains a detailed subsonic or shock free transonic flow solution on the hub-shroud midchannel stream surface of a turbomachine. The blade row may be fixed or rotating, and the blades may be twisted and leaned. Flow may be axial, mixed, or radial. Upstream and downstream flow variables may vary from hub to shroud, and provisions are made to correct for loss of stagnation pressure. The results include velocities, streamlines, and flow angles on the stream surface and approximate blade surface velocities.

  14. Latitude dependence of solar wind velocity observed at not less than 1 AU

    NASA Technical Reports Server (NTRS)

    Mitchell, D. G.; Roelof, E. C.; Wolfe, J. H.

    1981-01-01

    The large-scale solar wind velocity structure in the outer heliosphere has been systematically analyzed for Carrington rotations 1587-1541 (March 1972 to April 1976). Spacecraft data were taken from Imp 7/8 at earth, Pioneer 6, 8, and 9 near 1 AU, and Pioneer 10 and 11 between 1.6 and 5 AU. Using the constant radial velocity solar wind approximation to map all of the velocity data to its high coronal emission heliolongitude, the velocity structure observed at different spacecraft was examined for latitudinal dependence and compared with coronal structure in soft X-rays and H-alpha absorption features. The constant radial velocity approximation usually remains self-consistent in decreasing or constant velocity solar wind out to 5 AU, enabling us to separate radial from latitudinal propagation effects. Several examples of sharp nonmeridional stream boundaries in interplanetary space (about 5 deg latitude in width), often directly associated with features in coronal X-rays and H-alpha were found.

  15. Velocity space resolved absolute measurement of fast ion losses induced by a tearing mode in the ASDEX Upgrade tokamak

    NASA Astrophysics Data System (ADS)

    Galdon-Quiroga, J.; Garcia-Munoz, M.; Sanchis-Sanchez, L.; Mantsinen, M.; Fietz, S.; Igochine, V.; Maraschek, M.; Rodriguez-Ramos, M.; Sieglin, B.; Snicker, A.; Tardini, G.; Vezinet, D.; Weiland, M.; Eriksson, L. G.; The ASDEX Upgrade Team; The EUROfusion MST1 Team

    2018-03-01

    Absolute flux of fast ion losses induced by tearing modes have been measured by means of fast ion loss detectors (FILD) for the first time in RF heated plasmas in the ASDEX Upgrade tokamak. Up to 30 MW m-2 of fast ion losses are measured by FILD at 5 cm from the separatrix, consistent with infra-red camera measurements, with energies in the range of 250-500 keV and pitch angles corresponding to large trapped orbits. A resonant interaction between the fast ions in the high energy tail of the ICRF distribution and a m/n  =  5/4 tearing mode leads to enhanced fast ion losses. Around 9.3 +/- 0.7 % of the fast ion losses are found to be coherent with the mode and scale linearly with its amplitude, indicating the convective nature of the transport mechanism. Simulations have been carried out to estimate the contribution of the prompt losses. A good agreement is found between the simulated and the measured velocity space of the losses. The velocity space resonances that may be responsible for the enhanced fast ion losses are identified.

  16. Absolute plate velocities from seismic anisotropy: Importance of correlated errors

    NASA Astrophysics Data System (ADS)

    Zheng, Lin; Gordon, Richard G.; Kreemer, Corné

    2014-09-01

    The errors in plate motion azimuths inferred from shear wave splitting beneath any one tectonic plate are shown to be correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. Our preferred set of angular velocities, SKS-MORVEL, is determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25 ± 0.11° Ma-1 (95% confidence limits) right handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ = 19.2°) differs insignificantly from that for continental lithosphere (σ = 21.6°). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ = 7.4°) than for continental lithosphere (σ = 14.7°). Two of the slowest-moving plates, Antarctica (vRMS = 4 mm a-1, σ = 29°) and Eurasia (vRMS = 3 mm a-1, σ = 33°), have two of the largest within-plate dispersions, which may indicate that a plate must move faster than ≈ 5 mm a-1 to result in seismic anisotropy useful for estimating plate motion. The tendency of observed azimuths on the Arabia plate to be counterclockwise of plate motion may provide information about the direction and amplitude of superposed asthenospheric flow or about anisotropy in the lithospheric mantle.

  17. METAL-POOR LITHIUM-RICH GIANTS IN THE RADIAL VELOCITY EXPERIMENT SURVEY

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

    Ruchti, Gregory R.; Fulbright, Jon P.; Wyse, Rosemary F. G.

    We report the discovery of eight lithium-rich field giants found in a high-resolution spectroscopic sample of over 700 metal-poor stars ([Fe/H] < -0.5) selected from the Radial Velocity Experiment survey. The majority of the Li-rich giants in our sample are very metal-poor ([Fe/H] {approx}< -1.9), and have a Li abundance (in the form of {sup 7}Li), A(Li) = log (n(Li)/n(H)) + 12, between 2.30 and 3.63, well above the typical upper red giant branch (RGB) limit, A(Li) < 0.5, while two stars, with A(Li) {approx} 1.7-1.8, show similar lithium abundances to normal giants at the same gravity. We further includedmore » two metal-poor, Li-rich globular cluster giants in our sample, namely the previously discovered M3-IV101 and newly discovered (in this work) M68-A96. This comprises the largest sample of metal-poor Li-rich giants to date. We performed a detailed abundance analysis of all stars, finding that the majority of our sample stars have elemental abundances similar to that of Li-normal halo giants. Although the evolutionary phase of each Li-rich giant cannot be definitively determined, the Li-rich phase is likely connected to extra mixing at the RGB bump or early asymptotic giant branch that triggers cool bottom processing in which the bottom of the outer convective envelope is connected to the H-burning shell in the star. The surface of a star becomes Li-enhanced as {sup 7}Be (which burns to {sup 7}Li) is transported to the stellar surface via the Cameron-Fowler mechanism. We discuss and discriminate among several models for the extra mixing that can cause Li production, given the detailed abundances of the Li-rich giants in our sample.« less

  18. A Spitzer search for transits of radial velocity detected super-Earths

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

    Kammer, J. A.; Knutson, H. A.; Desert, J.-M.

    2014-02-01

    Unlike hot Jupiters or other gas giants, super-Earths are expected to have a wide variety of compositions, ranging from terrestrial bodies like our own to more gaseous planets like Neptune. Observations of transiting systems, which allow us to directly measure planet masses and radii and constrain atmospheric properties, are key to understanding the compositional diversity of the planets in this mass range. Although Kepler has discovered hundreds of transiting super-Earth candidates over the past 4 yr, the majority of these planets orbit stars that are too far away and too faint to allow for detailed atmospheric characterization and reliable massmore » estimates. Ground-based transit surveys focus on much brighter stars, but most lack the sensitivity to detect planets in this size range. One way to get around the difficulty of finding these smaller planets in transit is to start by choosing targets that are already known to host super-Earth sized bodies detected using the radial velocity (RV) technique. Here we present results from a Spitzer program to observe six of the most favorable RV-detected super-Earth systems, including HD 1461, HD 7924, HD 156668, HIP 57274, and GJ 876. We find no evidence for transits in any of their 4.5 μm flux light curves, and place limits on the allowed transit depths and corresponding planet radii that rule out even the most dense and iron-rich compositions for these objects. We also observed HD 97658, but the observation window was based on a possible ground-based transit detection that was later ruled out; thus the window did not include the predicted time for the transit detection recently made by the Microvariability and Oscillations of Stars space telescope.« less

  19. VizieR Online Data Catalog: HARPS-N radial velocities of KOI-70 (Buchhave+, 2016)

    NASA Astrophysics Data System (ADS)

    Buchhave, L. A.; Dressing, C. D.; Dumusque, X.; Rice, K.; Vanderburg, A.; Mortier, A.; Lopez-Morales, M.; Lopez, E.; Lundkvist, M. S.; Kjeldsen, H.; Affer, L.; Bonomo, A. S.; Charbonneau, D.; Collier, Cameron A.; Cosentino, R.; Figueira, P.; Fiorenzano, A. F. M.; Harutyunyan, A.; Haywood, R. D.; Johnson, J. A.; Latham, D. W.; Lovis, C.; Malavolta, L.; Mayor, M.; Micela, G.; Molinari, E.; Motalebi, F.; Nascimbeni, V.; Pepe, F.; Phillips, D. F.; Piotto, G.; Pollacco, D.; Queloz, D.; Sasselov, D.; Segransan, D.; Sozzetti, A.; Udry, S.; Watson, C.

    2017-01-01

    We obtained 125 observations of Kepler-20 (KOI-70, KIC 6850504, 2MASS J19104752+4220194) with the HARPS-N spectrograph on the 3.58m Telescopio Nazionale Galileo (TNG) located at Roque de Los Muchachos Observatory, La Palma, Spain. HARPS-N is an updated version of the original HARPS spectrograph on the 3.6m telescope at the European Southern Observatory on La Silla, Chile. HARPS-N is an ultra-stable fiber-fed high-resolution (R=115000) spectrograph with an optical wavelength coverage from 383 to 693nm. We obtained 61 and 64 observations of Kepler-20 in the 2014 and 2015 observing seasons, respectively (125 observations in total). We rejected 21 observations obtained under poor observing conditions where the internal error estimate exceeded 5m/s leaving a total of 104 observations. Kepler-20 has a mV=12.5 and required 30 minute exposure times to build up an adequate signal-to-noise ratio (S/N). The average S/N per pixel of the observations at 550nm is 30, yielding an average internal uncertainty estimate of 3.66m/s. The radial velocities and their 1σ errors are shows in Table1. (1 data file).

  20. High coronal structure of high velocity solar wind stream sources

    NASA Technical Reports Server (NTRS)

    Nolte, J. T.; Krieger, A. S.; Roelof, E. C.; Gold, R. E.

    1977-01-01

    It is shown analytically that the transition from a high-speed stream source to the ambient coronal conditions is quite rapid in longitude in the high corona. This sharp eastern coronal boundary for the solar wind stream sources is strongly suggested by the solar wind 'dwells' which appear in plots of solar wind velocity against constant-radial-velocity-approximation source longitudes. The possibility of a systematic velocity-dependent effect in the constant-radial-velocity approximation, which would cause this boundary to appear sharper than it is, is investigated. A velocity-dependent interplanetary propagation effect or a velocity-dependent 'source altitude' are two possible sources of such a systematic effect. It is shown that, for at least some dwells, significant interplanetary effects are not likely. The variation of the Alfvenic critical radius in solar wind dwells is calculated, showing that the high-velocity stream originates from a significantly lower altitude than the ambient solar wind.

  1. Radial velocity variability and stellar properties of FGK stars in the cores of NGC 2516 and NGC 2422

    NASA Astrophysics Data System (ADS)

    Bailey, John I.; Mateo, Mario; White, Russel J.; Shectman, Stephen A.; Crane, Jeffrey D.

    2018-04-01

    We present multi-epoch high-dispersion optical spectra obtained with the Michigan/Magellan Fibre System of 126 and 125 Sun-like stars in the young clusters NGC 2516 (141 Myr) and NGC 2422 (73 Myr). We determine stellar properties including radial velocity (RV), Teff, [Fe/H], [α/Fe] and the line-of-sight rotation rate, vrsin (i), from these spectra. Our median RV precision of 80 m s-1 on individual epochs that span a temporal baseline of 1.1 yr enables us to investigate membership and stellar binarity, and to search for sub-stellar companions. We determine membership probabilities and RV variability probabilities for our sample along with candidate companion orbital periods for a select subset of stars. In NGC 2516, we identified 81 RV members, 27 spectroscopic binaries (17 previously identified as photometric binaries) and 16 other stars that show significant RV variability after accounting for average stellar jitter at the 74 m s-1 level. In NGC 2422, we identify 57 members, 11 spectroscopic binaries and three other stars that show significant RV variability after accounting for an average jitter of 138 m s-1. We use Monte Carlo simulations to verify our stellar jitter measurements, determine the proportion of exoplanets and stellar companions to which we are sensitive, and estimate companion-mass limits for our targets. We also report mean cluster metallicity, velocity and velocity dispersion based on our member targets. We identify 58 non-member stars as RV variables, 24 of which have RV amplitudes that imply stellar or brown-dwarf mass companions. Finally, we note the discovery of a separate RV clustering of stars in our NGC 2422 sample.

  2. Radial velocity confirmation of Kepler-91 b. Additional evidence of its planetary nature using the Calar Alto/CAFE instrument

    NASA Astrophysics Data System (ADS)

    Lillo-Box, J.; Barrado, D.; Henning, Th.; Mancini, L.; Ciceri, S.; Figueira, P.; Santos, N. C.; Aceituno, J.; Sánchez, S. F.

    2014-08-01

    The object transiting the star Kepler-91 was recently assessed as being of planetary nature. The confirmation was achieved by analysing the light-curve modulations observed in the Kepler data. However, quasi-simultaneous studies claimed a self-luminous nature for this object, thus rejecting it as a planet. In this work, we apply anindependent approach to confirm the planetary mass of Kepler-91b by using multi-epoch high-resolution spectroscopy obtained with the Calar Alto Fiber-fed Echelle spectrograph (CAFE). We obtain the physical and orbital parameters with the radial velocity technique. In particular, we derive a value of 1.09 ± 0.20 MJup for the mass of Kepler-91b, in excellent agreement with our previous estimate that was based on the orbital brightness modulation.

  3. Absolute Plate Velocities from Seismic Anisotropy: Importance of Correlated Errors

    NASA Astrophysics Data System (ADS)

    Gordon, R. G.; Zheng, L.; Kreemer, C.

    2014-12-01

    The orientation of seismic anisotropy inferred beneath the interiors of plates may provide a means to estimate the motions of the plate relative to the deeper mantle. Here we analyze a global set of shear-wave splitting data to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. The errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are shown to be correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. Our preferred set of angular velocities, SKS-MORVEL, is determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11º Ma-1 (95% confidence limits) right-handed about 57.1ºS, 68.6ºE. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2°) differs insignificantly from that for continental lithosphere (σ=21.6°). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4°) than for continental lithosphere (σ=14.7°). Two of the slowest-moving plates, Antarctica (vRMS=4 mm a-1, σ=29°) and Eurasia (vRMS=3 mm a-1, σ=33°), have two of the largest within-plate dispersions, which may indicate that a plate must move faster than ≈5 mm a-1 to result in seismic anisotropy useful for estimating plate motion.

  4. Radial electric field in JET advanced tokamak scenarios with toroidal field ripple

    NASA Astrophysics Data System (ADS)

    Crombé, K; Andrew, Y; Biewer, T M; Blanco, E; de Vries, P C; Giroud, C; Hawkes, N C; Meigs, A; Tala, T; von Hellermann, M; Zastrow, K-D; JET EFDA Contributors

    2009-05-01

    A dedicated campaign has been run on JET to study the effect of toroidal field (TF) ripple on plasma performance. Radial electric field measurements from experiments on a series of plasmas with internal transport barriers (ITBs) and different levels of ripple amplitude are presented. They have been calculated from charge exchange measurements of impurity ion temperature, density and rotation velocity profiles, using the force balance equation. The ion temperature and the toroidal and poloidal rotation velocities are compared in plasmas with both reversed and optimized magnetic shear profiles. Poloidal rotation velocity (vθ) in the ITB region is measured to be of the order of a few tens of km s-1, significantly larger than the neoclassical predictions. Increasing levels of the TF ripple are found to decrease the ion temperature gradient in the ITB region, a measure for the quality of the ITB, and the maximum value of vθ is reduced. The poloidal rotation term dominates in the calculations of the total radial electric field (Er), with the largest gradient in Er measured in the radial region coinciding with the ITB.

  5. Rotational and radial velocities of 1.3-2.2 M {sub ☉} red giants in open clusters

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

    Carlberg, Joleen K., E-mail: jcarlberg@dtm.ciw.edu

    2014-06-01

    This study presents the rotational distribution of red giant (RG) stars in 11 old to intermediate age open clusters. The masses of these stars are all above the Kraft break, so they lose negligible amounts of their birth angular momentum (AM) during the main-sequence (MS) evolution. However, they do span a mass range with quite different AM distributions imparted during formation, with the stars less massive than ∼1.6M {sub ☉} arriving on the MS with lower rotation rates than the more massive stars. The majority of RGs in this study are slow rotators across the entire red giant branch regardlessmore » of mass, supporting the picture that intermediate-mass stars rapidly spin down when they evolve off the MS and develop convection zones capable of driving a magnetic dynamo. Nevertheless, a small fraction of RGs in open clusters show some level of enhanced rotation, and faster rotators are as common in these clusters as in the field RG population. Most of these enhanced rotators appear to be red clump stars, which is also true of the underlying stellar sample, while others are clearly RGs that are above or below the clump. In addition to rotational velocities, the radial velocities (RVs) and membership probabilities of individual stars are also presented. Cluster heliocentric RVs for NGC 6005 and Pismis 18 are reported for the first time.« less

  6. Continuum limit of electrostatic gyrokinetic absolute equilibrium

    NASA Astrophysics Data System (ADS)

    Zhu, Jian-Zhou

    2012-06-01

    Electrostatic gyrokinetic absolute equilibria with continuum velocity field are obtained through the partition function and through the Green function of the functional integral. The new results justify and explain the prescription for quantization/discretization or taking the continuum limit of velocity. The mistakes in the Appendix D of our earlier work [J.-Z. Zhu and G. W. Hammett, Phys. Plasmas 17, 122307 (2010)] are explained and corrected. If the lattice spacing for discretizing velocity is big enough, all the invariants could concentrate at the lowest Fourier modes in a negative-temperature state, which might indicate a possible variation of the dual cascade picture in 2D plasma turbulence.

  7. The MASSIVE survey - VIII. Stellar velocity dispersion profiles and environmental dependence of early-type galaxies

    NASA Astrophysics Data System (ADS)

    Veale, Melanie; Ma, Chung-Pei; Greene, Jenny E.; Thomas, Jens; Blakeslee, John P.; Walsh, Jonelle L.; Ito, Jennifer

    2018-02-01

    We measure the radial profiles of the stellar velocity dispersions, σ(R), for 90 early-type galaxies (ETGs) in the MASSIVE survey, a volume-limited integral-field spectroscopic (IFS) galaxy survey targeting all northern-sky ETGs with absolute K-band magnitude MK < -25.3 mag, or stellar mass M* ≳ 4 × 1011M⊙, within 108 Mpc. Our wide-field 107 arcsec × 107 arcsec IFS data cover radii as large as 40 kpc, for which we quantify separately the inner (2 kpc) and outer (20 kpc) logarithmic slopes γinner and γouter of σ(R). While γinner is mostly negative, of the 56 galaxies with sufficient radial coverage to determine γouter we find 36 per cent to have rising outer dispersion profiles, 30 per cent to be flat within the uncertainties and 34 per cent to be falling. The fraction of galaxies with rising outer profiles increases with M* and in denser galaxy environment, with 10 of the 11 most massive galaxies in our sample having flat or rising dispersion profiles. The strongest environmental correlations are with local density and halo mass, but a weaker correlation with large-scale density also exists. The average γouter is similar for brightest group galaxies, satellites and isolated galaxies in our sample. We find a clear positive correlation between the gradients of the outer dispersion profile and the gradients of the velocity kurtosis h4. Altogether, our kinematic results suggest that the increasing fraction of rising dispersion profiles in the most massive ETGs are caused (at least in part) by variations in the total mass profiles rather than in the velocity anisotropy alone.

  8. VizieR Online Data Catalog: Velocities of RGB stars in the Leo II dwarf galaxy (Spencer+, 2017)

    NASA Astrophysics Data System (ADS)

    Spencer, M. E.; Mateo, M.; Walker, M. G.; Olszewski, E. W.; McConnachie, A. W.; Kirby, E. N.; Koch, A.

    2018-05-01

    We use radial velocity data from four studies. The first set comprises 31 red giant branch (RGB) stars with a median radial velocity error of 3 km/s (Vogt et al. 1995AJ....109..151V). It contains the first spectroscopic observations of RGB stars in Leo II, and remained the only kinematic data set for over a decade. The second study, by Koch et al. (2007, J/AJ/134/566, hereafter KK07), consists of radial velocities for 171 member stars. KK07 published average velocities taken during three epochs between 2003 and 2004. The third data set comes from Kirby et al. (2010, J/ApJS/191/352). They used Keck/DEIMOS to obtain medium resolution spectroscopy for the purpose of chemical abundance measurements, but also extracted radial velocities to help identify member stars. The fourth and final data set is published in Spencer et al. (2017, J/ApJ/836/202), which contains radial velocities for 175 member stars. Fifty of these have two or more observations, which were taken over the course of eight years with Hectochelle (Szentgyorgyi et al. 1998SPIE.3355..242S) on the Multiple Mirror Telescope. This data set contains five epochs between the years 2006 and 2013. (1 data file).

  9. Ion velocity analysis of rotating structures in a magnetic linear plasma device

    NASA Astrophysics Data System (ADS)

    Claire, N.; Escarguel, A.; Rebont, C.; Doveil, F.

    2018-06-01

    The MISTRAL device is designed to produce a linear magnetized plasma column. It has been used a few years ago to study a nonlinear low frequency instability exhibiting an azimuthal number m = 2. By changing the experimental configuration of MISTRAL, this work shows experimental results on an m = 1 rotating instability with strongly different behavior. The spatio-temporal evolution of the ion velocity distribution function given by a laser-induced fluorescence diagnostic is measured to infer the radial and azimuthal velocities, ion fluxes, and electric fields. The naive image of a plasma exhibiting a global rotation is again invalidated in this m = 1 mode but in a different way. Contrary to the m = 2 mode, the rotation frequency of the instability is lower than the ion cyclotron frequency and ions exhibit a complex behavior with a radial outward flux inside the unstable arm and azimuthal ion fluxes always directed toward the unstable arm. The azimuthal ion velocity is close to zero inside the ionization region, whereas the radial ion velocity grows linearly with radius. The radial electric field is oriented inward inside the unstable arm and outward outside. An axial velocity perturbation is also present, indicating that contrary to the m = 2 mode, the m = 1 mode is not a flute mode. These results cannot be easily interpreted with existing theories.

  10. The radial-azimuthal stability of accretion disks - Gas pressure contributions

    NASA Technical Reports Server (NTRS)

    Mckee, M. R.

    1991-01-01

    A radial-azimuthal stability analysis of a thin, alpha disk accretion flow is presented. The proportion of radiation pressure, Pr, of the unperturbed flow is allowed to vary according to the parameter beta = Pr/P, where P is the total pressure. As is the case for a purely radial analysis, the disk is stable for beta equal to or less than 0.6. However, the coupling of radial and azimuthal perturbations eliminates the viscous instability for such nonradial modes for all values of beta. The group velocity of the retrograde thermal mode is calculated as a function of beta.

  11. Absolute earthquake locations using 3-D versus 1-D velocity models below a local seismic network: example from the Pyrenees

    NASA Astrophysics Data System (ADS)

    Theunissen, T.; Chevrot, S.; Sylvander, M.; Monteiller, V.; Calvet, M.; Villaseñor, A.; Benahmed, S.; Pauchet, H.; Grimaud, F.

    2018-03-01

    Local seismic networks are usually designed so that earthquakes are located inside them (primary azimuthal gap <<180°) and close to the seismic stations (0-100 km). With these local or near-regional networks (0°-5°), many seismological observatories still routinely locate earthquakes using 1-D velocity models. Moving towards 3-D location algorithms requires robust 3-D velocity models. This work takes advantage of seismic monitoring spanning more than 30 yr in the Pyrenean region. We investigate the influence of a well-designed 3-D model with station corrections including basins structure and the geometry of the Mohorovicic discontinuity on earthquake locations. In the most favourable cases (GAP < 180° and distance to the first station lower than 15 km), results using 1-D velocity models are very similar to 3-D results. The horizontal accuracy in the 1-D case can be higher than in the 3-D case if lateral variations in the structure are not properly resolved. Depth is systematically better resolved in the 3-D model even on the boundaries of the seismic network (GAP > 180° and distance to the first station higher than 15 km). Errors on velocity models and accuracy of absolute earthquake locations are assessed based on a reference data set made of active seismic, quarry blasts and passive temporary experiments. Solutions and uncertainties are estimated using the probabilistic approach of the NonLinLoc (NLLoc) software based on Equal Differential Time. Some updates have been added to NLLoc to better focus on the final solution (outlier exclusion, multiscale grid search, S-phases weighting). Errors in the probabilistic approach are defined to take into account errors on velocity models and on arrival times. The seismicity in the final 3-D catalogue is located with a horizontal uncertainty of about 2.0 ± 1.9 km and a vertical uncertainty of about 3.0 ± 2.0 km.

  12. Radial electric field in JET advanced tokamak scenarios with toroidal field ripple

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

    Crombe, K.; Andrew, Y.; Biewer, Theodore M

    A dedicated campaign has been run on JET to study the effect of toroidal field (TF) ripple on plasma performance. Radial electric field measurements from experiments on a series of plasmas with internal transport barriers (ITBs) and different levels of ripple amplitude are presented. They have been calculated from charge exchange measurements of impurity ion temperature, density and rotation velocity profiles, using the force balance equation. The ion temperature and the toroidal and poloidal rotation velocities are compared in plasmas with both reversed and optimized magnetic shear profiles. Poloidal rotation velocity (v ) in the ITB region is measured tomore » be of the order of a few tens of km s 1, significantly larger than the neoclassical predictions. Increasing levels of the TF ripple are found to decrease the ion temperature gradient in the ITB region, a measure for the quality of the ITB, and the maximum value of v is reduced. The poloidal rotation term dominates in the calculations of the total radial electric field (Er), with the largest gradient in Er measured in the radial region coinciding with the ITB.« less

  13. Hide and Seek: Radial-velocity searches for planets around active stars

    NASA Astrophysics Data System (ADS)

    Haywood, Raphaelle

    2017-01-01

    The ultimate obstacle to determining the masses of small, rocky exoplanets through radial-velocity (RV) monitoring is the intrinsic variability of the host stars themselves. For my PhD, I developed an intuitive and robust data analysis framework in which the activity-induced variations are modelled with a Gaussian process that has the frequency structure of the stellar magnetic activity. This allowed me to determine precise and accurate masses of the planets in the CoRoT-7, Kepler-78 and Kepler-10 systems. In parallel, I explored the physical origin of activity-induced RV variations of our best-known star: the Sun. I conducted the first systematic RV campaign of the Sun seen as an exoplanet host star using the 3.6m/HARPS spectrograph, by observing sunlight reflected off the bright asteroid 4/Vesta. I used images from the Solar Dynamics Observatory to reconstruct the RV signals incurred by individual surface features such as sunspots, faculae and granulation. I found that the activity-induced RV variations are driven by the suppression of convective blueshift arising dominantly from the presence of faculae. I also identified the full-disc magnetic flux as an excellent proxy for activity-induced RV variations.I am now pursuing my solar investigations using Sun-as-a-star RV observations acquired with the new solar telescope feed at HARPS-N. In particular, I am investigating the impact of magnetic surface features on the shapes of the spectral line profiles, rather than on the RVs themselves (which are a single moment of these lines). This work is key to developing physically-driven, better-tailored models for activity-induced RV variations, in preparation for the potentially habitable, Earth-like planets to be discovered and characterised in the coming years with TESS and GMT/G-CLEF.This work was funded by the Science and Technology Facilities Council in the United Kingdom and the John Templeton Foundation.

  14. VizieR Online Data Catalog: HARPS and HARPS-N 55 Cnc radial velocities (Lopez-Morales+, 2014)

    NASA Astrophysics Data System (ADS)

    Lopez-Morales, M.; Triaud, A. H. M. J.; Rodler, F.; Dumusque, X.; Buchhave, L. A.; Harutyunyan, A.; Hoyer, S.; Alonso, R.; Gillon, M.; Kaib, N. A.; Latham, D. W.; Lovis, C.; Pepe, F.; Queloz, D.; Raymond, S. N.; Segransan, D.; Waldmann, I. P.; Udry, S.

    2017-04-01

    Shortly after the detection of 55 Cnc e's transit was announced, we requested four spectroscopic time series on HARPS (Prog. ID 288.C-5010; PI: Triaud) as Director Discretionary Time. HARPS is installed on the 3.6 m telescope at the European Southern Observatory on La Silla, Chile (Mayor et al. 2003Msngr.114...20M). The position of 55 Cnc in the sky-RA(J2000)=08:52:35.81, DE(J2000)=+28:10:50.95-is low as seen from La Silla. The target remains at a zenith distance of z<2 for only ~2.5 hr per night, with a transit duration of about 1.5 hr having to fit within this tight window. This constraint on the airmass, essential to obtain precise radial velocities (RVs), is set by the instrumental atmospheric dispersion corrector. We used the ephemeris by Gillon et al. (2012, J/A+A/539/A28), then at an advanced stage of preparation, to schedule our observations. In total, we gathered 179 spectra on the nights starting on 2012 January 27, 2012 February 13, 2012 February 27, and 2012 March 15 UT. (1 data file).

  15. SOAP: A Tool for the Fast Computation of Photometry and Radial Velocity Induced by Stellar Spots

    NASA Astrophysics Data System (ADS)

    Boisse, I.; Bonfils, X.; Santos, N. C.; Figueira, P.

    2013-04-01

    Dark spots and bright plages are present on the surface of dwarf stars from spectral types F to M, even in their low-active phase (like the Sun). Their appearance and disappearance on the stellar photosphere, combined with the stellar rotation, may lead to errors and uncertainties in the characterization of planets both in radial velocity (RV) and photometry. Spot Oscillation and Planet (SOAP) is a tool offered to the community that enables to simulate spots and plages on rotating stars and computes their impact on RV and photometric measurements. This tool will help to understand the challenges related to the knowledge of stellar activity for the next decade: detect telluric planets in the habitable zone of their stars (from G to M dwarfs), understand the activity in the low-mass end of M dwarf (on which future projects, like SPIRou or CARMENES, will focus), limitation to the characterization of the exoplanetary atmosphere (from the ground or with Spitzer, JWST), search for planets around young stars. These can be simulated with SOAP in order to search for indices and corrections to the effect of activity.

  16. A laser frequency comb that enables radial velocity measurements with a precision of 1 cm s(-1).

    PubMed

    Li, Chih-Hao; Benedick, Andrew J; Fendel, Peter; Glenday, Alexander G; Kärtner, Franz X; Phillips, David F; Sasselov, Dimitar; Szentgyorgyi, Andrew; Walsworth, Ronald L

    2008-04-03

    Searches for extrasolar planets using the periodic Doppler shift of stellar spectral lines have recently achieved a precision of 60 cm s(-1) (ref. 1), which is sufficient to find a 5-Earth-mass planet in a Mercury-like orbit around a Sun-like star. To find a 1-Earth-mass planet in an Earth-like orbit, a precision of approximately 5 cm s(-1) is necessary. The combination of a laser frequency comb with a Fabry-Pérot filtering cavity has been suggested as a promising approach to achieve such Doppler shift resolution via improved spectrograph wavelength calibration, with recent encouraging results. Here we report the fabrication of such a filtered laser comb with up to 40-GHz (approximately 1-A) line spacing, generated from a 1-GHz repetition-rate source, without compromising long-term stability, reproducibility or spectral resolution. This wide-line-spacing comb, or 'astro-comb', is well matched to the resolving power of high-resolution astrophysical spectrographs. The astro-comb should allow a precision as high as 1 cm s(-1) in astronomical radial velocity measurements.

  17. The Kepler-19 System: A Thick-envelope Super-Earth with Two Neptune-mass Companions Characterized Using Radial Velocities and Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Malavolta, Luca; Borsato, Luca; Granata, Valentina; Piotto, Giampaolo; Lopez, Eric; Vanderburg, Andrew; Figueira, Pedro; Mortier, Annelies; Nascimbeni, Valerio; Affer, Laura; Bonomo, Aldo S.; Bouchy, Francois; Buchhave, Lars A.; Charbonneau, David; Collier Cameron, Andrew; Cosentino, Rosario; Dressing, Courtney D.; Dumusque, Xavier; Fiorenzano, Aldo F. M.; Harutyunyan, Avet; Haywood, Raphaëlle D.; Johnson, John Asher; Latham, David W.; Lopez-Morales, Mercedes; Lovis, Christophe; Mayor, Michel; Micela, Giusi; Molinari, Emilio; Motalebi, Fatemeh; Pepe, Francesco; Phillips, David F.; Pollacco, Don; Queloz, Didier; Rice, Ken; Sasselov, Dimitar; Ségransan, Damien; Sozzetti, Alessandro; Udry, Stéphane; Watson, Chris

    2017-05-01

    We report a detailed characterization of the Kepler-19 system. This star was previously known to host a transiting planet with a period of 9.29 days, a radius of 2.2 R ⊕, and an upper limit on the mass of 20 M ⊕. The presence of a second, non-transiting planet was inferred from the transit time variations (TTVs) of Kepler-19b over eight quarters of Kepler photometry, although neither the mass nor period could be determined. By combining new TTVs measurements from all the Kepler quarters and 91 high-precision radial velocities obtained with the HARPS-N spectrograph, using dynamical simulations we obtained a mass of 8.4 ± 1.6 M ⊕ for Kepler-19b. From the same data, assuming system coplanarity, we determined an orbital period of 28.7 days and a mass of 13.1 ± 2.7 M ⊕ for Kepler-19c and discovered a Neptune-like planet with a mass of 20.3 ± 3.4 M ⊕ on a 63-day orbit. By comparing dynamical simulations with non-interacting Keplerian orbits, we concluded that neglecting interactions between planets may lead to systematic errors that can hamper the precision in the orbital parameters when the data set spans several years. With a density of 4.32 ± 0.87 g cm-3 (0.78 ± 0.16 ρ ⊕) Kepler-19b belongs to the group of planets with a rocky core and a significant fraction of volatiles, in opposition to low-density planets characterized only by transit time variations and an increasing number of rocky planets with Earth-like density. Kepler-19 joins the small number of systems that reconcile transit timing variation and radial velocity measurements.

  18. Radial-radial single rotor turbine

    DOEpatents

    Platts, David A [Los Alamos, NM

    2006-05-16

    A rotor for use in turbine applications has a radial compressor/pump having radially disposed spaced apart fins forming passages and a radial turbine having hollow turbine blades interleaved with the fins and through which fluid from the radial compressor/pump flows. The rotor can, in some applications, be used to produce electrical power.

  19. Performance of an asymmetric short annular diffuser with a nondiverging inner wall using suction. [control of radial profiles of diffuser exit velocity

    NASA Technical Reports Server (NTRS)

    Juhasz, A.

    1974-01-01

    The performance of a short highly asymmetric annular diffuser equipped with wall bleed (suction) capability was evaluated at nominal inlet Mach numbers of 0.188, 0.264, and 0.324 with the inlet pressure and temperature at near ambient values. The diffuser had an area ratio of 2.75 and a length- to inlet-height ratio of 1.6. Results show that the radial profiles of diffuser exit velocity could be controlled from a severely hub peaked to a slightly tip biased form by selective use of bleed. At the same time, other performance parameters were also improved. These results indicate the possible application of the diffuser bleed technique to control flow profiles to gas turbine combustors.

  20. Measurement of poloidal velocity on the National Spherical Torus Experiment (invited).

    PubMed

    Bell, Ronald E; Feder, Russell

    2010-10-01

    A diagnostic suite has been developed to measure the impurity poloidal flow using charge exchange recombination spectroscopy on the National Spherical Torus Experiment. Toroidal and poloidal viewing systems measure all the quantities required to determine the radial electric field. Two sets of up/down symmetric poloidal views are used to measure both the active emission in the plane of the neutral heating beams and the background emission in a radial plane away from the neutral beams. Differential velocity measurements isolate the line-integrated poloidal velocity from apparent flows due to the energy-dependent charge exchange cross section. Six f/1.8 spectrometers measure 276 spectra to obtain 75 active and 63 background channels every 10 ms. The local measurements from a similar midplane toroidal viewing system are mapped into two dimensions to allow the inversion of poloidal line-integrated measurements to obtain local poloidal velocity profiles. The radial resolution after inversion is 0.6-1.8 cm from the plasma edge to the center.

  1. Evaluation of the friction coefficient, the radial stress, and the damage work during needle insertions into agarose gels.

    PubMed

    Urrea, Fabián A; Casanova, Fernando; Orozco, Gustavo A; García, José J

    2016-03-01

    Agarose hydrogels have been extensively used as a phantom material to mimic the mechanical behavior of soft biological tissues, e.g. in studies aimed to analyze needle insertions into the organs producing tissue damage. To better predict the radial stress and damage during needle insertions, this study was aimed to determine the friction coefficient between the material of commercial catheters and hydrogels. The friction coefficient, the tissue damage and the radial stress were evaluated at 0.2, 1.8, and 10mm/s velocities for 28, 30, and 32 gauge needles of outer diameters equal to 0.36, 0.31, and 0.23mm, respectively. Force measurements during needle insertions and retractions on agarose gel samples were used to analyze damage and radial stress. The static friction coefficient (0.295±0.056) was significantly higher than the dynamic (0.255±0.086). The static and dynamic friction coefficients were significantly smaller for the 0.2mm/s velocity compared to those for the other two velocities, and there was no significant difference between the friction coefficients for 1.8 and 10mm/s. Radial stress averages were 131.2±54.1, 248.3±64.2, and 804.9±164.3Pa for the insertion velocity of 0.2, 1.8, and 10mm/s, respectively. The radial stress presented a tendency to increase at higher insertion velocities and needle size, which is consistent with other studies. However, the damage work did not show to be a good predictor of tissue damage, which appears to be due to simplifications in the analytical model. Differently to other approaches, the method proposed here based on radial stress may be extended in future studies to quantity tissue damage in vivo along the entire needle track. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. A study of the compact group of galaxies Shahbazian 4

    NASA Technical Reports Server (NTRS)

    Lynds, C. R.; Khachikian, E. YE.; Amirkhanian, A. S.

    1990-01-01

    The radial velocities of members of Shakhbazian 4 are determined. It is found that the dispersion of the radial velocities is 440 km/s. The apparent and absolute magnitudes of galaxies in V color are obtained. It is found that the M/L ratio of the group is about 220 solar mass/solar luminosity. The crossing time for the Shakhbazian 4 group is equal to 47 Myr.

  3. AN EFFICIENT, COMPACT, AND VERSATILE FIBER DOUBLE SCRAMBLER FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS

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

    Halverson, Samuel; Roy, Arpita; Mahadevan, Suvrath

    2015-06-10

    We present the design and test results of a compact optical fiber double-scrambler for high-resolution Doppler radial velocity instruments. This device consists of a single optic: a high-index n ∼ 2 ball lens that exchanges the near and far fields between two fibers. When used in conjunction with octagonal fibers, this device yields very high scrambling gains (SGs) and greatly desensitizes the fiber output from any input illumination variations, thereby stabilizing the instrument profile of the spectrograph and improving the Doppler measurement precision. The system is also highly insensitive to input pupil variations, isolating the spectrograph from telescope illumination variationsmore » and seeing changes. By selecting the appropriate glass and lens diameter the highest efficiency is achieved when the fibers are practically in contact with the lens surface, greatly simplifying the alignment process when compared to classical double-scrambler systems. This prototype double-scrambler has demonstrated significant performance gains over previous systems, achieving SGs in excess of 10,000 with a throughput of ∼87% using uncoated Polymicro octagonal fibers. Adding a circular fiber to the fiber train further increases the SG to >20,000, limited by laboratory measurement error. While this fiber system is designed for the Habitable-zone Planet Finder spectrograph, it is more generally applicable to other instruments in the visible and near-infrared. Given the simplicity and low cost, this fiber scrambler could also easily be multiplexed for large multi-object instruments.« less

  4. Design and experimental evaluation of compact radial-inflow turbines

    NASA Technical Reports Server (NTRS)

    Fredmonski, A. J.; Huber, F. W.; Roelke, R. J.; Simonyi, S.

    1991-01-01

    The application of a multistage 3D Euler solver to the aerodynamic design of two compact radial-inflow turbines is presented, along with experimental results evaluating and validating the designs. The objectives of the program were to design, fabricate, and rig test compact radial-inflow turbines with equal or better efficiency relative to conventional designs, while having 40 percent less rotor length than current traditionally-sized radial turbines. The approach to achieving these objectives was to apply a calibrated 3D multistage Euler code to accurately predict and control the high rotor flow passage velocities and high aerodynamic loadings resulting from the reduction in rotor length. A comparison of the advanced compact designs to current state-of-the-art configurations is presented.

  5. Three-dimensional flow field measurements in a radial inflow turbine scroll using LDV

    NASA Technical Reports Server (NTRS)

    Malak, M. F.; Hamed, A.; Tabakoff, W.

    1986-01-01

    The results of an experimental study of the three-dimensional flow field in a radial inflow turbine scroll are presented. A two-color LDV system was used in the measurement of three orthogonal velocity components at 758 points located throughout the scroll and the unvaned portion of the nozzle. The cold flow experimental results are presented for through-flow velocity contours and the cross velocity vectors.

  6. Solar updraft power generator with radial and curved vanes

    NASA Astrophysics Data System (ADS)

    Hafizh, Hadyan; Hamsan, Raziff; Zamri, Aidil Azlan Ahmad; Keprawi, Mohamad Fairuz Mohamad; Shirato, Hiromichi

    2018-02-01

    Solar radiation is the largest source of energy available on earth and the solar updraft power generator (SUPG) is a renewable energy facility capable of harnessing its abundant power. Unlike the conventional wind turbines that harness natural wind in the atmosphere and often encounter with the intermittent issue or even complete cut-off from airflow, the SUPG creates artificial wind as a result of solar-induced convective flows. However, the SUPG has an inherent low total efficiency due to the conversion of thermal energy into pressure energy. Acknowledging the low efficiency and considering its potential as a renewable energy facility, the current work aims to increase the total efficiency by installing a series of guide walls inside the collector. Two types of guide walls were used i.e. radial and curved vanes. The result with curved vanes showed that the updraft velocity is higher compare to those without vanes. About 18% and 64% improvement of updraft velocity and mechanical power were attained respectively. Furthermore, it was observed that the role of radial vanes configuration was more to produce a smooth updraft velocity profile rather than increasing the total efficiency.

  7. Seismic Linear Noise Attenuation with Use of Radial Transform

    NASA Astrophysics Data System (ADS)

    Szymańska-Małysa, Żaneta

    2018-03-01

    One of the goals of seismic data processing is to attenuate the recorded noise in order to enable correct interpretation of the image. Radial transform has been used as a very effective tool in the attenuation of various types of linear noise, both numerical and real (such as ground roll, direct waves, head waves, guided waves etc). The result of transformation from offset - time (X - T) domain into apparent velocity - time (R - T) domain is frequency separation between reflections and linear events. In this article synthetic and real seismic shot gathers were examined. One example was targeted at far offset area of dataset where reflections and noise had similar apparent velocities and frequency bands. Another example was a result of elastic modelling where linear artefacts were produced. Bandpass filtering and scaling operation executed in radial domain attenuated all discussed types of linear noise very effectively. After noise reduction all further processing steps reveal better results, especially velocity analysis, migration and stacking. In all presented cases signal-to-noise ratio was significantly increased and reflections covered previously by noise were revealed. Power spectra of filtered seismic records preserved real dynamics of reflections.

  8. Radial transfer effects for poloidal rotation

    NASA Astrophysics Data System (ADS)

    Hallatschek, Klaus

    2010-11-01

    Radial transfer of energy or momentum is the principal agent responsible for radial structures of Geodesic Acoustic Modes (GAMs) or stationary Zonal Flows (ZF) generated by the turbulence. For the GAM, following a physical approach, it is possible to find useful expressions for the individual components of the Poynting flux or radial group velocity allowing predictions where a mathematical full analysis is unfeasible. Striking differences between up-down symmetric flux surfaces and asymmetric ones have been found. For divertor geometries, e.g., the direction of the propagation depends on the sign of the ion grad-B drift with respect to the X-point, reminiscent of a sensitive determinant of the H-mode threshold. In nonlocal turbulence computations it becomes obvious that the linear energy transfer terms can be completely overwhelmed by the action of the turbulence. In contrast, stationary ZFs are governed by the turbulent radial transfer of momentum. For sufficiently large systems, the Reynolds stress becomes a deterministic functional of the flows, which can be empirically determined from the stress response in computational turbulence studies. The functional allows predictions even on flow/turbulence states not readily obtainable from small amplitude noise, such as certain transport bifurcations or meta-stable states.

  9. Absolute plate motions relative to deep mantle plumes

    NASA Astrophysics Data System (ADS)

    Wang, Shimin; Yu, Hongzheng; Zhang, Qiong; Zhao, Yonghong

    2018-05-01

    Advances in whole waveform seismic tomography have revealed the presence of broad mantle plumes rooted at the base of the Earth's mantle beneath major hotspots. Hotspot tracks associated with these deep mantle plumes provide ideal constraints for inverting absolute plate motions as well as testing the fixed hotspot hypothesis. In this paper, 27 observed hotspot trends associated with 24 deep mantle plumes are used together with the MORVEL model for relative plate motions to determine an absolute plate motion model, in terms of a maximum likelihood optimization for angular data fitting, combined with an outlier data detection procedure based on statistical tests. The obtained T25M model fits 25 observed trends of globally distributed hotspot tracks to the statistically required level, while the other two hotspot trend data (Comores on Somalia and Iceland on Eurasia) are identified as outliers, which are significantly incompatible with other data. For most hotspots with rate data available, T25M predicts plate velocities significantly lower than the observed rates of hotspot volcanic migration, which cannot be fully explained by biased errors in observed rate data. Instead, the apparent hotspot motions derived by subtracting the observed hotspot migration velocities from the T25M plate velocities exhibit a combined pattern of being opposite to plate velocities and moving towards mid-ocean ridges. The newly estimated net rotation of the lithosphere is statistically compatible with three recent estimates, but differs significantly from 30 of 33 prior estimates.

  10. Stellar Velocity Dispersion and Anisotropy of the Milky Way Inner Halo

    NASA Astrophysics Data System (ADS)

    King, Charles, III; Brown, Warren R.; Geller, Margaret J.; Kenyon, Scott J.

    2015-11-01

    We measure the three components of velocity dispersion, σR, σθ, σϕ, for stars within 6 < R < 30 kpc of the Milky Way using a new radial velocity sample from the MMT telescope. We combine our measurements with previously published data so that we can more finely sample the stellar halo. We use a maximum likelihood statistical method for estimating mean velocities, dispersions, and covariances assuming only that velocities are normally distributed. The alignment of the velocity ellipsoid is consistent with a spherically symmetric gravitational potential. From the spherical Jeans equation, the mass of the Milky Way is M≤ft(R≤slant 12 {kpc}\\right)=1.3× {10}11 {M}⊙ with an uncertainty of 40%. We also find a region of discontinuity, 15 ≲ R ≲ 25 kpc, where the estimated velocity dispersions and anisotropies diverge from their anticipated values, confirming the break observed by others. We argue that this break in anisotropy is physically explained by coherent stellar velocity structure in the halo, such as the Sgr stream. To significantly improve our understanding of halo kinematics will require combining radial velocities with future Gaia proper motions.

  11. A HIGH-VELOCITY BULGE RR LYRAE VARIABLE ON A HALO-LIKE ORBIT

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

    Kunder, Andrea; Storm, J.; Rich, R. M.

    2015-07-20

    We report on the RR Lyrae variable star, MACHO 176.18833.411, located toward the Galactic bulge and observed within the data from the ongoing Bulge RR Lyrae Radial Velocity Assay, which has the unusual radial velocity of −372 ± 8 km s{sup −1} and true space velocity of −482 ± 22 km s{sup −1} relative to the Galactic rest frame. Located less than 1 kpc from the Galactic center and toward a field at (l, b) = (3, −2.5), this pulsating star has properties suggesting it belongs to the bulge RR Lyrae star population, yet a velocity indicating it is abnormal,more » at least with respect to bulge giants and red clump stars. We show that this star is most likely a halo interloper and therefore suggest that halo contamination is not insignificant when studying metal-poor stars found within the bulge area, even for stars within 1 kpc of the Galactic center. We discuss the possibility that MACHO 176.18833.411 is on the extreme edge of the bulge RR Lyrae radial velocity distribution, and also consider a more exotic scenario in which it is a runaway star moving through the Galaxy.« less

  12. Radial and poloidal correlation reflectometry on Experimental Advanced Superconducting Tokamak

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

    Qu, Hao; Zhang, Tao; Han, Xiang

    2015-08-15

    An X-mode polarized V band (50 GHz–75 GHz) radial and poloidal correlation reflectometry is designed and installed on Experimental Advanced Superconducting Tokamak (EAST). Two frequency synthesizers (12 GHz–19 GHz) are used as sources. Signals from the sources are up-converted to V band using active quadruplers and then coupled together for launching through one single pyramidal antenna. Two poloidally separated antennae are installed to receive the reflected waves from plasma. This reflectometry system can be used for radial and poloidal correlation measurement of the electron density fluctuation. In ohmically heated plasma, the radial correlation length is about 1.5 cm measured bymore » the system. The poloidal correlation analysis provides a means to estimate the fluctuation velocity perpendicular to the main magnetic field. In the present paper, the distance between two poloidal probing points is calculated with ray-tracing code and the propagation time is deduced from cross-phase spectrum. Fluctuation velocity perpendicular to the main magnetic field in the core of ohmically heated plasma is about from −1 km/s to −3 km/s.« less

  13. Endoscopic versus open radial artery harvest and mammario-radial versus aorto-radial grafting in patients undergoing coronary artery bypass surgery: protocol for the 2 × 2 factorial designed randomised NEO trial

    PubMed Central

    2014-01-01

    Background Coronary artery bypass grafting using the radial artery has, since the 1990s, gone through a revival. Observational studies have indicated better long-term patency when using radial arteries. Therefore, radial artery might be preferred especially in younger patients where long time patency is important. During the last 10 years different endoscopic techniques to harvest the radial artery have evolved. Endoscopic radial artery harvest only requires a small incision near the wrist in contrast to open harvest, which requires an incision from the elbow to the wrist. However, it is unknown whether the endoscopic technique results in fewer complications or a graft patency comparable to open harvest. When the radial artery has been harvested, there are two ways to use the radial artery as a graft. One way is sewing it onto the aorta and another is sewing it onto the mammary artery. It is unknown which technique is the superior revascularisation technique. Methods/Design The NEO Trial is a randomised clinical trial with a 2 × 2 factorial design. We plan to randomise 300 participants into four intervention groups: (1) mammario-radial endoscopic group; (2) aorto-radial endoscopic group; (3) mammario-radial open surgery group; and (4) aorto-radial open surgery group. The hand function will be assessed by a questionnaire, a clinical examination, the change in cutaneous sensibility, and the measurement of both sensory and motor nerve conduction velocity at 3 months postoperatively. All the postoperative complications will be registered, and we will evaluate muscular function, scar appearance, vascular supply to the hand, and the graft patency including the patency of the central radial artery anastomosis. A patency evaluation by multi-slice computer tomography will be done at one year postoperatively. We expect the nerve conduction studies and the standardised neurological examinations to be able to discriminate differences in hand function comparing

  14. A SITELLE view of M31's central region - I. Calibrations and radial velocity catalogue of nearly 800 emission-line point-like sources

    NASA Astrophysics Data System (ADS)

    Martin, Thomas B.; Drissen, Laurent; Melchior, Anne-Laure

    2018-01-01

    We present a detailed description of the wavelength, astrometric and photometric calibration plan for SITELLE, the imaging Fourier transform spectrometer attached to the Canada-France-Hawaii telescope, based on observations of a red (647-685 nm) data cube of the central region (11 arcmin × 11 arcmin) of M 31. The first application, presented in this paper is a radial-velocity catalogue (with uncertainties of ∼2-6 km s-1) of nearly 800 emission-line point-like sources, including ∼450 new discoveries. Most of the sources are likely planetary nebulae, although we also detect five novae (having erupted in the first eight months of 2016) and one new supernova remnant candidate.

  15. Newton's absolute time and space in general relativity

    NASA Astrophysics Data System (ADS)

    Gautreau, Ronald

    2000-04-01

    I describe a reference system in a spherically symmetric gravitational field that is built around times recorded by radially moving geodesic clocks. The geodesic time coordinate t and the curvature spatial radial coordinate R result in spacetime descriptions of the motion of the geodesic clocks that are exactly identical with equations following from Newton's absolute time and space used with his inverse square law. I show how to use the resulting Newtonian/general-relativistic equations for geodesic clocks to generate exact relativistic metric forms in terms of the coordinates (R,t). Newtonian theory does not describe light. However, the motion of light can be determined from the (R,t) general-relativistic metric forms obtained from Newtonian theory by setting ds2(R,t)=0. In this sense, a theory of light can be related to absolute time and space of Newtonian gravitational theory. I illustrate the (R,t) methodology by first solving the equations that result from a Newtonian picture and then examining the exact metric forms for the general-relativistic problems of the Schwarzschild field, gravitational collapse and expansion of a zero-pressure perfect fluid, and zero-pressure big-bang cosmology. I also briefly describe other applications of the Newtonian/general-relativistic formulation to: embedding a Schwarzschild mass into cosmology; continuously following an expanding universe from radiation to matter domination; Dirac's Large Numbers hypothesis; the incompleteness of Kruskal-Szekeres spacetime; double valuedness in cosmology; and the de Sitter universe.

  16. Experimental research on time-resolved evolution of cathode plasma expansion velocity in a long pulsed magnetically insulated coaxial diode

    NASA Astrophysics Data System (ADS)

    Zhu, Danni; Zhang, Jun; Zhong, Huihuang; Ge, Xingjun; Gao, Jingming

    2018-02-01

    Unlike planar diodes, separate research of the axial and radial plasma expansion velocities is difficult for magnetically insulated coaxial diodes. Time-resolved electrical diagnostic which is based on the voltage-ampere characteristics has been employed to study the temporal evolution of the axial and radial cathode plasma expansion velocities in a long pulsed magnetically insulated coaxial diode. Different from a planar diode with a "U" shaped profile of temporal velocity evolution, the temporal evolution trend of the axial expansion velocity is proved to be a "V" shaped profile. Apart from the suppression on the radial expansion velocity, the strong magnetic field is also conducive to slowing down the axial expansion velocity. Compared with the ordinary graphite cathode, the carbon velvet and graphite composite cathode showed superior characteristics as judged by the low plasma expansion velocity and long-term electrical stability as a promising result for applications where long-pulsed and reliable operation at high power is required.

  17. A RADIAL VELOCITY TEST FOR SUPERMASSIVE BLACK HOLE BINARIES AS AN EXPLANATION FOR BROAD, DOUBLE-PEAKED EMISSION LINES IN ACTIVE GALACTIC NUCLEI

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

    Liu, Jia; Halpern, Jules P.; Eracleous, Michael

    2016-01-20

    One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked Hα emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. and we use much longer time series for the three objects studied in that paper. Although systematic changes in radial velocitymore » can be traced in many of their lines, they are demonstrably not like those of a spectroscopic binary in a circular orbit. Any spectroscopic binary period must therefore be much longer than the span of the monitoring (assuming a circular orbit), which in turn would require black hole masses that exceed by 1–2 orders of magnitude the values obtained for these objects using techniques such as reverberation mapping and stellar velocity dispersion. Moreover, the response of the double-peaked Balmer line profiles to fluctuations of the ionizing continuum and the shape of the Lyα profiles are incompatible with an SMBH binary. The binary broad-line region hypothesis is therefore disfavored. Other processes evidently shape these line profiles and cause the long-term velocity variations of the double peaks.« less

  18. SEVEN NEW BINARIES DISCOVERED IN THE KEPLER LIGHT CURVES THROUGH THE BEER METHOD CONFIRMED BY RADIAL-VELOCITY OBSERVATIONS

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

    Faigler, S.; Mazeh, T.; Tal-Or, L.

    We present seven newly discovered non-eclipsing short-period binary systems with low-mass companions, identified by the recently introduced BEER algorithm, applied to the publicly available 138-day photometric light curves obtained by the Kepler mission. The detection is based on the beaming effect (sometimes called Doppler boosting), which increases (decreases) the brightness of any light source approaching (receding from) the observer, enabling a prediction of the stellar Doppler radial-velocity (RV) modulation from its precise photometry. The BEER algorithm identifies the BEaming periodic modulation, with a combination of the well-known Ellipsoidal and Reflection/heating periodic effects, induced by short-period companions. The seven detections weremore » confirmed by spectroscopic RV follow-up observations, indicating minimum secondary masses in the range 0.07-0.4 M{sub Sun }. The binaries discovered establish for the first time the feasibility of the BEER algorithm as a new detection method for short-period non-eclipsing binaries, with the potential to detect in the near future non-transiting brown-dwarf secondaries, or even massive planets.« less

  19. Onset of radial flow in p + p collisions

    DOE PAGES

    Jiang, Kun; Zhu, Yinying; Liu, Weitao; ...

    2015-02-23

    It has been debated for decades whether hadrons emerging from p+p collisions exhibit collective expansion. The signal of the collective motion in p+p collisions is not as clear as in heavy-ion collisions because of the low multiplicity and large fluctuation in p+p collisions. Tsallis Blast-Wave (TBW) model is a thermodynamic approach, introduced to handle the overwhelming correlation and fluctuation in the hadronic processes. We have systematically studied the identified particle spectra in p+p collisions from RHIC to LHC using TBW and found no appreciable radial flow in p+p collisions below √s = 900 GeV. At LHC higher energy of 7more » TeV in p+p collisions, the radial flow velocity achieves an average of (β) = 0.320 ± 0.005. This flow velocity is comparable to that in peripheral (40-60%) Au+Au collisions at RHIC. In addition, breaking of the identified particle spectra m T scaling was also observed at LHC from a model independent test.« less

  20. Three-dimensional flow measurements in a vaneless radial turbine scroll

    NASA Technical Reports Server (NTRS)

    Tabakoff, W.; Wood, B.; Vittal, B. V. R.

    1982-01-01

    The flow behavior in a vaneless radial turbine scroll was examined experimentally. The data was obtained using the slant sensor technique of hot film anemometry. This method used the unsymmetric heat transfer characteristics of a constant temperature hot film sensor to detect the flow direction and magnitude. This was achieved by obtaining a velocity vector measurement at three sensor positions with respect to the flow. The true magnitude and direction of the velocity vector was then found using these values and a Newton-Raphson numerical technique. The through flow and secondary flow velocity components are measured at various points in three scroll sections.

  1. Debris perturbed by radiation pressure: relative velocities across circular orbits

    NASA Astrophysics Data System (ADS)

    Celestino, C.; Winter, O.; Prado, A.

    It is widely know that there is a large amount of space debris and meteoroid particles around the Earth. The objects larger than 10 cm can be tracked by radar and others means allowing the satellites/ships to be maneuvered to avoid collisions. However, the detection and the attendance of the orbital dynamics of objects smaller than 10 cm (particles) is very difficult. These particles can be generated by explosions of larger objects, collisions between large objects, or simply for the reaction of the oxygen in the wall of an object could generate the escape of paint pieces. The importance of studying the dynamics of these particles is that they can have relative high speeds and their effects in a collision could cause damages and even compromise the space missions. In this present work we considered a dynamical system of mm size particles around the Earth subject to the effects of radiation pressure. Our main goal is to study the evolution of its relative velocity to the circular orbits that it crosses.Firstly, it is considered that the particle is initially in circular orbit. The effect of the radiation pressure produces variations in its eccentricity, resulting in a change in its orbital velocity. The results show that the variation of the radial distance and the relative velocity can be divided in three parts: secular, long period and short period. For the radial distance the secular variation is constant, because the semi-axis is constant. The long period variation presents a configuration that repeats with period inferior to the orbital period of the Earth. And, finally, the short period variation presents points of local maxima and minima for the variation of the width of the radial distance. When considering the variation of the relative velocity we have that the secular behavior and of long period are similar to those obtained for the variation of the radial distance. However, for the short period variation, we have a larger number of local maxima and minima

  2. A radially resolved kinetic model for nonlocal electron ripple diffusion losses in tokamaks

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

    Robertson, Scott

    A relatively simple radially resolved kinetic model is applied to the ripple diffusion problem for electrons in tokamaks. The distribution function f(r,v) is defined on a two-dimensional grid, where r is the radial coordinate and v is the velocity coordinate. Particle transport in the radial direction is from ripple and banana diffusion and transport in the velocity direction is described by the Fokker-Planck equation. Particles and energy are replaced by source functions that are adjusted to maintain a constant central density and temperature. The relaxed profiles of f(r,v) show that the electron distribution function at the wall contains suprathermal electronsmore » that have diffused from the interior that enhance ripple transport. The transport at the periphery is therefore nonlocal. The energy replacement times from the computational model are near to the experimental replacement times for tokamak discharges in the compilation by Pfeiffer and Waltz [Nucl. Fusion 19, 51 (1979)].« less

  3. Radial gas motions in The H I Nearby Galaxy Survey (THINGS)

    NASA Astrophysics Data System (ADS)

    Schmidt, Tobias M.; Bigiel, Frank; Klessen, Ralf S.; de Blok, W. J. G.

    2016-04-01

    The study of 21 cm line observations of atomic hydrogen allows detailed insight into the kinematics of spiral galaxies. We use sensitive high-resolution Very Large Array data from The H I Nearby Galaxy Survey (THINGS) to search for radial gas flows primarily in the outer parts (up to 3 × r25) of 10 nearby spiral galaxies. Inflows are expected to replenish the gas reservoir and fuel star formation under the assumption that galaxies evolve approximately in steady state. We carry out a detailed investigation of existing tilted ring fitting schemes and discover systematics that can hamper their ability to detect signatures of radial flows. We develop a new Fourier decomposition scheme that fits for rotational and radial velocities and simultaneously determines position angle and inclination as a function of radius. Using synthetic velocity fields we show that our novel fitting scheme is less prone to such systematic errors and that it is well suited to detect radial inflows in discs. We apply our fitting scheme to 10 THINGS galaxies and find clear indications of, at least partly previously unidentified, radial gas flows, in particular for NGC 2403 and NGC 3198 and to a lesser degree for NGC 7331, NGC 2903 and NGC 6946. The mass flow rates are of the same order but usually larger than the star formation rates. At least for these galaxies a scenario in which continuous mass accretion feeds star formation seems plausible. The other galaxies show a more complicated picture with either no clear inflow, outward motions or complex kinematic signatures.

  4. Entanglement-enhanced lidars for simultaneous range and velocity measurements

    NASA Astrophysics Data System (ADS)

    Zhuang, Quntao; Zhang, Zheshen; Shapiro, Jeffrey H.

    2017-10-01

    Lidar is a well-known optical technology for measuring a target's range and radial velocity. We describe two lidar systems that use entanglement between transmitted signals and retained idlers to obtain significant quantum enhancements in simultaneous measurements of these parameters. The first entanglement-enhanced lidar circumvents the Arthurs-Kelly uncertainty relation for simultaneous measurements of range and radial velocity from the detection of a single photon returned from the target. This performance presumes there is no extraneous (background) light, but is robust to the round-trip loss incurred by the signal photons. The second entanglement-enhanced lidar—which requires a lossless, noiseless environment—realizes Heisenberg-limited accuracies for both its range and radial-velocity measurements, i.e., their root-mean-square estimation errors are both proportional to 1 /M when M signal photons are transmitted. These two lidars derive their entanglement-based enhancements from the use of a unitary transformation that takes a signal-idler photon pair with frequencies ωS and ωI and converts it to a signal-idler photon pair whose frequencies are (ωS+ωI)/2 and (ωS-ωI)/2 . Insight into how this transformation provides its benefits is provided through an analogy to continuous-variable superdense coding.

  5. Recent radial turbine research at the NASA Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Rohlik, H. E.; Kofskey, M. G.

    1971-01-01

    The high efficiencies of small radial turbines led to their application in space power systems and numerous APU and shaft power engines. Experimental and analytical work associated with these systems included examination of blade-shroud clearance, blade loading, and exit diffuser design. Results indicate high efficiency over a wide range of specific speed and also insensitivity to clearance and blade loading in the radial part of the rotor. The exit diffuser investigation indicated that a conventional conical outer wall may not provide the velocity variation consistent with minimum overall diffuser loss.

  6. Recent radial turbine research at the NASA Lewis Research Center.

    NASA Technical Reports Server (NTRS)

    Rohlik, H. E.; Kofskey, M. G.

    1972-01-01

    The major results obtained in several recent experimental programs on small radial inflow turbines for space applications are presented and discussed. Specifically, experimental and analytical work associated with these systems that has included examination of blade-shroud clearance, blade loading, and exit diffuser design, is considered. Results indicate high efficiency over a wide range of specific speed, and also insensitivity to clearance and blade loading in the radial part of the rotor. The exit diffuser investigation indicated that a conventional conical outer wall may not provide the velocity variation consistent with minimum overall diffuser loss.

  7. Velocities of gas in star-forming regions

    NASA Astrophysics Data System (ADS)

    Nissen, H. D.; Gustafsson, M.; Field, D.; Lemaire, J. L.; Clénet, Y.; Rouan, D.

    2007-12-01

    We present high spatial (0.18") and velocity (<2 km/s) resolution observations of the central 1'x1' of OMC1. We identify a large number of shock features and determine radial velocity, position angle and emission brightness for each of these features. Using this dataset we analyze the kinematic properties of the inner square arcminute of OMC1, identifying among other things the IR signature of a massive outflow originating from source I.

  8. Radial stiffness characteristics of the overlap regions of sarcomeres in isolated skeletal myofibrils in pre-force generating state.

    PubMed

    Miyashiro, Daisuke; Ohtsuki, Misato; Shimamoto, Yuta; Wakayama, Jun'ichi; Kunioka, Yuki; Kobayashi, Takakazu; Ishiwata, Shin'ichi; Yamada, Takenori

    2017-01-01

    We have studied the stiffness of myofilament lattice in sarcomeres in the pre-force generating state, which was realized by a relaxing reagent, BDM (butane dione monoxime). First, the radial stiffness for the overlap regions of sarcomeres of isolated single myofibrils was estimated from the resulting decreases in diameter by osmotic pressure applied with the addition of Dextran. Then, the radial stiffness was also estimated from force-distance curve measurements with AFM technology. The radial stiffness for the overlap regions thus obtained was composed of a soft and a rigid component. The soft component visco-elastically changed in a characteristic fashion depending on the physiological conditions of myofibrils, suggesting that it comes from cross-bridge structures. BDM treatments significantly affected the soft radial component of contracting myofibrils depending on the approach velocity of cantilever: It was nearly equal to that in the contracting state at high approach velocity, whereas as low as that in the relaxing state at low approach velocity. However, comparable BDM treatments greatly suppressed the force production and the axial stiffness in contracting glycerinated muscle fibers and also the sliding velocity of actin filaments in the in vitro motility assay. Considering that BDM shifts the cross-bridge population from force generating to pre-force generating states in contracting muscle, the obtained results strongly suggest that cross-bridges in the pre-force generating state are visco-elastically attached to the thin filaments in such a binding manner that the axial stiffness is low but the radial stiffness significantly high similar to that in force generating state.

  9. The Kepler-19 System: A Thick-envelope Super-Earth with Two Neptune-mass Companions Characterized Using Radial Velocities and Transit Timing Variations

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

    Malavolta, Luca; Borsato, Luca; Granata, Valentina

    We report a detailed characterization of the Kepler-19 system. This star was previously known to host a transiting planet with a period of 9.29 days, a radius of 2.2 R {sub ⊕}, and an upper limit on the mass of 20 M {sub ⊕}. The presence of a second, non-transiting planet was inferred from the transit time variations (TTVs) of Kepler-19b over eight quarters of Kepler photometry, although neither the mass nor period could be determined. By combining new TTVs measurements from all the Kepler quarters and 91 high-precision radial velocities obtained with the HARPS-N spectrograph, using dynamical simulations wemore » obtained a mass of 8.4 ± 1.6 M {sub ⊕} for Kepler-19b. From the same data, assuming system coplanarity, we determined an orbital period of 28.7 days and a mass of 13.1 ± 2.7 M {sub ⊕} for Kepler-19c and discovered a Neptune-like planet with a mass of 20.3 ± 3.4 M {sub ⊕} on a 63-day orbit. By comparing dynamical simulations with non-interacting Keplerian orbits, we concluded that neglecting interactions between planets may lead to systematic errors that can hamper the precision in the orbital parameters when the data set spans several years. With a density of 4.32 ± 0.87 g cm{sup −3} (0.78 ± 0.16 ρ {sub ⊕}) Kepler-19b belongs to the group of planets with a rocky core and a significant fraction of volatiles, in opposition to low-density planets characterized only by transit time variations and an increasing number of rocky planets with Earth-like density. Kepler-19 joins the small number of systems that reconcile transit timing variation and radial velocity measurements.« less

  10. Calibrated Tully-fisher Relations For Improved Photometric Estimates Of Disk Rotation Velocities

    NASA Astrophysics Data System (ADS)

    Reyes, Reinabelle; Mandelbaum, R.; Gunn, J. E.; Pizagno, J.

    2011-01-01

    We present calibrated scaling relations (also referred to as Tully-Fisher relations or TFRs) between rotation velocity and photometric quantities-- absolute magnitude, stellar mass, and synthetic magnitude (a linear combination of absolute magnitude and color)-- of disk galaxies at z 0.1. First, we selected a parent disk sample of 170,000 galaxies from SDSS DR7, with redshifts between 0.02 and 0.10 and r band absolute magnitudes between -18.0 and -22.5. Then, we constructed a child disk sample of 189 galaxies that span the parameter space-- in absolute magnitude, color, and disk size-- covered by the parent sample, and for which we have obtained kinematic data. Long-slit spectroscopy were obtained from the Dual Imaging Spectrograph (DIS) at the Apache Point Observatory 3.5 m for 99 galaxies, and from Pizagno et al. (2007) for 95 galaxies (five have repeat observations). We find the best photometric estimator of disk rotation velocity to be a synthetic magnitude with a color correction that is consistent with the Bell et al. (2003) color-based stellar mass ratio. The improved rotation velocity estimates have a wide range of scientific applications, and in particular, in combination with weak lensing measurements, they enable us to constrain the ratio of optical-to-virial velocity in disk galaxies.

  11. Differences of the Solar Magnetic Activity Signature in Velocity and Intensity Helioseismic Observations

    NASA Astrophysics Data System (ADS)

    Salabert, D.; García, R. A.; Jiménez, A.

    2013-12-01

    The high-quality, full-disk helioseismic observations continuously collected by the spectrophotometer GOLF and the three photometers VIRGO/SPMs onboard the SoHO spacecraft for 17 years now (since April 11, 1996, apart from the SoHO “vacations”) are absolutely unique for the study of the interior of the Sun and its variability with magnetic activity. Here, we look at the differences in the low-degree oscillation p-mode frequencies between radial velocity and intensity measurements taking into account all the known features of the p-mode profiles (e.g., the opposite peak asymmetry), and of the power spectrum (e.g., the presence of the higher degrees ℓ = 4 and 5 in the signal). We show that the intensity frequencies are higher than the velocity frequencies during the solar cycle with a clear temporal dependence. The response between the individual angular degrees is also different. Time delays are observed between the temporal variations in GOLF and VIRGO frequencies. Such analysis is important in order to put new constraints and to better understand the mechanisms responsible for the temporal variations of the oscillation frequencies with the solar magnetic activity as well as their height dependences in the solar atmosphere. It is also important for the study of the stellar magnetic activity using asteroseismic data.

  12. Results from the APOGEE IN-SYNC Orion: parameters and radial velocities for thousands of young stars in the Orion Complex.

    NASA Astrophysics Data System (ADS)

    Da Rio, Nicola; SDSS Apogee IN-SYNC ancillary program Team

    2015-01-01

    I will present the results of our characterization of the dynamical status of the young stellar population in the Orion A star forming region. This is based on radial velocity measurements obtained within the SDSS-III Apogee IN-SYNC Orion Survey, which obtained high-resolution spectroscopy of ~3000 objects in the region, from the dense Orion Nebula Cluster - the prototypical nearby region of active massive star formation - to the low-density environments of the L1641 region. We find evidence for kinematic subclustering along the star forming filament, where the stellar component remains kinematically associated to the gas; in the ONC we find that the stellar population is supervirial and currently expanding. We rule out the existence of a controversial candidate foreground cluster to the south of the ONC. These results, complemented with an analysis of the spatial structure of the population, enables critical tests of theories that describe the formation and early evolution of Orion and young clusters in general.

  13. A Proper Motion Search for Stars Escaping from Globular Clusters with High Velocities

    NASA Astrophysics Data System (ADS)

    Meusinger, H.; Scholz, R.-D.; Irwin, M.

    The dynamical evolution of globular clusters, in particular during the late phases, may be strongly influenced by the energy transfer from binaries to passing stars. As a by-product of this process, stars with high velocities are expected, perhaps high enough to escape from the cluster. Accurate proper motions are the only suitable tool to identify candidates for such high-velocity cluster stars. In order to perform such a search, we use a catalogue of absolute proper motions and UBV magnitudes for about 104 stars with B < 20 in a field of 10 square degrees centered on the globular cluster M3. The data were derived from more than 80 photographic plates taken between 1965 and 1995 with the Tautenburg Schmidt telescope and measured by means of the APM facility, Cambridge. The stellar sample is complete to B = 18.5 and comprises nearly all post-main-sequence stars in the halo of M3 and its surrounding. The proper motions are of Hipparcos-like accuracy (median error 1 mas/yr) in this magnitude range. We find several dozens of candidates, distributed over the whole field, with proper motions and colours consistent with the assumption of their origin from the cluster. Further conclusions can be drawn only on the basis of radial velocity measurements for the candidates and of estimates for the field-star contamination by means of simulations of the Galactic structure and kinematics in this field.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  16. Constraints on the Efficiency of Radial Migration in Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Daniel, Kathryne J.; Wyse, Rosemary F. G.

    2015-01-01

    A transient spiral arm can permanently rearrange the orbital angular momentum of the stellar disk without inducing kinematic heating. This phenomenon is called radial migration because a star's orbital angular momentum determines its mean orbital radius. Should radial migration be an efficient process it could cause a large fraction of disk stars to experience significant changes in their individual orbital angular momenta on dynamically short timescales. Such scenarios have strong implications for the chemical, structural and kinematic evolution of disk galaxies. We have undertaken an investigation into the physical dependencies of the efficiency of radial migration on stellar kinematics and spiral structure. In order for a disk star to migrate radially, it must first be 'trapped' in a particular family of orbits, called horseshoe orbits, that occur near the radius of corotation with a spiral pattern. Thus far, the only analytic criterion for horseshoe orbits has been for stars with zero random orbital energy. We present our analytically derived 'capture criterion' for stars with some finite random orbital energy in a disk with a given rotation curve. Our capture criterion predict that trapping in a horseshoe orbit is primarily determined by whether or not the position of a star's mean orbital radius (determined by its orbital angular momentum) is within the 'capture region', the location and shape of which can be derived from the capture criterion. We visualize and confirm this prediction via numerically integrated orbits. We then apply our capture criterion to snap shot models of disk galaxies to determine (1) the radial distribution of the fraction of stars initially trapped in horseshoe orbits, and (2) the dependence of the total fraction of captured stars in the disk on the radial component of the stellar velocity dispersion (σR) and the amplitude of the spiral perturbation to the underlying potential at corotation. We here present a model of an exponential

  17. Optical and Near-infrared Radial Velocity Content of M Dwarfs: Testing Models with Barnard’s Star

    NASA Astrophysics Data System (ADS)

    Artigau, Étienne; Malo, Lison; Doyon, René; Figueira, Pedro; Delfosse, Xavier; Astudillo-Defru, Nicola

    2018-05-01

    High-precision radial velocity (RV) measurements have been central in the study of exoplanets during the last two decades, from the early discovery of hot Jupiters, to the recent mass measurements of Earth-sized planets uncovered by transit surveys. While optical RV is now a mature field, there is currently a strong effort to push the technique into the near-infrared domain (chiefly Y, J, H, and K bandpasses) to probe planetary systems around late-type stars. The combined lower mass and luminosity of M dwarfs leads to an increased reflex RV signal for planets in the habitable zone compared to Sun-like stars. The estimates on the detectability of planets rely on various instrumental characteristics but also on a prior knowledge of the stellar spectrum. While the overall properties of M dwarf spectra have been extensively tested against observations, the same is not true for their detailed line profiles, which leads to significant uncertainties when converting a given signal-to-noise ratio to a corresponding RV precision as attainable on a given spectrograph. By combining archival CRIRES and HARPS data with ESPaDOnS data of Barnard’s star, we show that state-of-the-art atmosphere models over-predict the Y- and J-band RV content by more than a factor of ∼2, while under-predicting the H- and K-band content by half.

  18. Asymmetric orbital distribution near mean motion resonance: Application to planets observed by Kepler and radial velocities

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

    Xie, Ji-Wei, E-mail: jwxie@nju.edu.cn, E-mail: jwxie@astro.utoronto.ca

    2014-05-10

    Many multiple-planet systems have been found by the Kepler transit survey and various radial velocity (RV) surveys. Kepler planets show an asymmetric feature, namely, there are small but significant deficits/excesses of planet pairs with orbital period spacing slightly narrow/wide of the exact resonance, particularly near the first order mean motion resonance (MMR), such as 2:1 and 3:2 MMR. Similarly, if not exactly the same, an asymmetric feature (pileup wide of 2:1 MMR) is also seen in RV planets, but only for massive ones. We analytically and numerically study planets' orbital evolutions near and in the MMR. We find that theirmore » orbital period ratios could be asymmetrically distributed around the MMR center regardless of dissipation. In the case of no dissipation, Kepler planets' asymmetric orbital distribution could be partly reproduced for 3:2 MMR but not for 2:1 MMR, implying that dissipation might be more important to the latter. The pileup of massive RV planets just wide of 2:1 MMR is found to be consistent with the scenario that planets formed separately then migrated toward the MMR. The location of the pileup infers a K value of 1-100 on the order of magnitude for massive planets, where K is the damping rate ratio between orbital eccentricity and semimajor axis during planet migration.« less

  19. Constraints on the anisotropic contributions to velocity discontinuities at ∼60 km depth beneath the Pacific

    PubMed Central

    Harmon, Nicholas

    2017-01-01

    Abstract Strong, sharp, negative seismic discontinuities, velocity decreases with depth, are observed beneath the Pacific seafloor at ∼60 km depth. It has been suggested that these are caused by an increase in radial anisotropy with depth, which occurs in global surface wave models. Here we test this hypothesis in two ways. We evaluate whether an increase in surface wave radial anisotropy with depth is robust with synthetic resolution tests. We do this by fitting an example surface wave data set near the East Pacific Rise. We also estimate the apparent isotropic seismic velocity discontinuities that could be caused by changes in radial anisotropy in S‐to‐P and P‐to‐S receiver functions and SS precursors using synthetic seismograms. We test one model where radial anisotropy is caused by olivine alignment and one model where it is caused by compositional layering. The result of our surface wave inversion suggests strong shallow azimuthal anisotropy beneath 0–10 Ma seafloor, which would also have a radial anisotropy signature. An increase in radial anisotropy with depth at 60 km depth is not well‐resolved in surface wave models, and could be artificially observed. Shallow isotropy underlain by strong radial anisotropy could explain moderate apparent velocity drops (<6%) in SS precursor imaging, but not receiver functions. The effect is diminished if strong anisotropy also exists at 0–60 km depth as suggested by surface waves. Overall, an increase in radial anisotropy with depth may not exist at 60 km beneath the oceans and does not explain the scattered wave observations. PMID:29097907

  20. Constraints on the anisotropic contributions to velocity discontinuities at ∼60 km depth beneath the Pacific.

    PubMed

    Rychert, Catherine A; Harmon, Nicholas

    2017-08-01

    Strong, sharp, negative seismic discontinuities, velocity decreases with depth, are observed beneath the Pacific seafloor at ∼60 km depth. It has been suggested that these are caused by an increase in radial anisotropy with depth, which occurs in global surface wave models. Here we test this hypothesis in two ways. We evaluate whether an increase in surface wave radial anisotropy with depth is robust with synthetic resolution tests. We do this by fitting an example surface wave data set near the East Pacific Rise. We also estimate the apparent isotropic seismic velocity discontinuities that could be caused by changes in radial anisotropy in S-to-P and P-to-S receiver functions and SS precursors using synthetic seismograms. We test one model where radial anisotropy is caused by olivine alignment and one model where it is caused by compositional layering. The result of our surface wave inversion suggests strong shallow azimuthal anisotropy beneath 0-10 Ma seafloor, which would also have a radial anisotropy signature. An increase in radial anisotropy with depth at 60 km depth is not well-resolved in surface wave models, and could be artificially observed. Shallow isotropy underlain by strong radial anisotropy could explain moderate apparent velocity drops (<6%) in SS precursor imaging, but not receiver functions. The effect is diminished if strong anisotropy also exists at 0-60 km depth as suggested by surface waves. Overall, an increase in radial anisotropy with depth may not exist at 60 km beneath the oceans and does not explain the scattered wave observations.

  1. Radial Velocity Fiber-Fed Spectrographs Towards the Discovery of Compact Planets and Pulsations on M Stars

    NASA Astrophysics Data System (ADS)

    Berdiñas, Zaira M.

    2016-11-01

    This thesis is developed in the framework of the paradigm that seeks for the discovery of an Earth analog. Nowadays, low mass stars, and in particular M dwarf stars, are key targets towards achieving this goal. In this thesis, I focus on the study of the short-time domain of M dwarf stars with the aim of searching for short period planets, but also for the first detection of stellar pulsations on this spectral type. Both science goals are the primary objectives of the “Cool Tiny Beats” (CTB) survey, which has produced most of the data used in this thesis. CTB data consist in high resolution and high-cadence spectroscopic Doppler measurements taken either with HARPS or HARPS-N spectrographs. First of all, a thorough understanding of the spectrographs response in the short time domain was performed to characterize the sources of noise in our range of study. Our first approach to the goals of this thesis consisted in the design of an observational experiment to delve into the HARPS-N sub-night performance. Results unveiled variability of the spectra continuum correlated with instabilities of the spectrograph illumination associated to the airmass. Such distortions, which are wavelength and time dependent, are also present in at least one of the data-products given by the HARPS-N reduction software: the width of the mean-line profiles (i.e. the so-called FWHM index), an index commonly used as a proxy of the stellar activity. As a consequence, we searched for an alternative approach to measure the width index. In particular, we calculated the mean-line profile of the spectrum with a least-squares-deconvolution technique and we obtained the profile indices as the moments of the profile distribution. As part of this study, we also corroborated that the radial velocities calculated with our template matching algorithm TERRA are not affected by the illumination stability. This work unveiled a possible failure of the HARPS-N atmospheric dispersion corrector (or ADC) and

  2. Analysis of the cross flow in a radial inflow turbine scroll

    NASA Technical Reports Server (NTRS)

    Hamed, A.; Abdallah, S.; Tabakoff, W.

    1977-01-01

    Equations of motion were derived, and a computational procedure is presented, for determining the nonviscous flow characteristics in the cross-sectional planes of a curved channel due to continuous mass discharge or mass addition. An analysis was applied to the radial inflow turbine scroll to study the effects of scroll geometry and the through flow velocity profile on the flow behavior. The computed flow velocity component in the scroll cross-sectional plane, together with the through flow velocity profile which can be determined in a separate analysis, provide a complete description of the three dimensional flow in the scroll.

  3. A Plasma Model of Missile Exhaust Plumes. (Axial and Radial Conductivity Distributions for the Redeye Missile).

    DTIC Science & Technology

    1977-04-01

    Conductivity ...... . .i 6 Relief Map of Conductivity ......... i9 7a conductivity versus Axial Position with Radial Position a a Parater...concentrations ii. pressure iii. temperature iv. velocity v. snie, number and velocity distribuions of the liquid particlas (if any are to be considered) I vi...Number = 1 vi. J• velocity = 8644 fps; Edge velocity = 10 fps vii. Jet temperature = 21160 K; Edge temperature = 278*K Also, at the exit piane, the

  4. Negative ion productions in high velocity collision between small carbon clusters and Helium atom target

    NASA Astrophysics Data System (ADS)

    M, Chabot; K, Béroff; T, Pino; G, Féraud; N, Dothi; Padellec A, Le; G, Martinet; S, Bouneau; Y, Carpentier

    2012-11-01

    We measured absolute double capture cross section of Cn+ ions (n=1,5) colliding, at 2.3 and 2.6 a.u velocities, with an Helium target atom and the branching ratios of fragmentation of the so formed electronically excited anions Cn-*. We also measured absolute cross section for the electronic attachment on neutral Cn clusters colliding at same velocities with He atom. This is to our knowledge the first measurement of neutral-neutral charge exchange in high velocity collision.

  5. Assessment of dyssynchronous wall motion during acute myocardial ischemia using velocity vector imaging.

    PubMed

    Masuda, Kasumi; Asanuma, Toshihiko; Taniguchi, Asuka; Uranishi, Ayumi; Ishikura, Fuminobu; Beppu, Shintaro

    2008-03-01

    The purpose of this study was to investigate the diagnostic value of velocity vector imaging (VVI) for detecting acute myocardial ischemia and whether VVI can accurately demonstrate the spatial extent of ischemic risk area. Using a tracking algorithm, VVI can display velocity vectors of regional wall motion overlaid onto the B-mode image and allows the quantitative assessment of myocardial mechanics. However, its efficacy for diagnosing myocardial ischemia has not been evaluated. In 18 dogs with flow-limiting stenosis and/or total occlusion of the coronary artery, peak systolic radial velocity (V(SYS)), radial velocity at mitral valve opening (V(MVO)), peak systolic radial strain, and the percent change in wall thickening (%WT) were measured in the normal and risk areas and compared to those at baseline. Sensitivity and specificity for detecting the stenosis and occlusion were analyzed in each parameter. The area of inward velocity vectors at mitral valve opening (MVO) detected by VVI was compared to the risk area derived from real-time myocardial contrast echocardiography (MCE). Twelve image clips were randomly selected from the baseline, stenosis, and occlusions to determine the intra- and inter-observer agreement for the VVI parameters. The left circumflex coronary flow was reduced by 44.3 +/- 9.0% during stenosis and completely interrupted during occlusion. During coronary artery occlusion, inward motion at MVO was observed in the risk area. Percent WT, peak systolic radial strain, V(SYS), and V(MVO) changed significantly from values at baseline. During stenosis, %WT, peak systolic radial strain, and V(SYS) did not differ from those at baseline; however, V(MVO) was significantly increased (-0.12 +/- 0.60 cm/s vs. -0.96 +/- 0.55 cm/s, p = 0.015). Sensitivity and specificity of V(MVO) for detecting ischemia were superior to those of other parameters. The spatial extent of inward velocity vectors at MVO correlated well with that of the risk area derived from MCE

  6. Radial forces in a misaligned radial face seal

    NASA Technical Reports Server (NTRS)

    Etsion, I.

    1978-01-01

    Radial forces on the primary seal ring of a flat misaligned seal are analyzed, taking into account the radial variation in seal clearance. An analytical solution for both hydrostatic and hydrodynamic effects is presented that covers the whole range from zero to full angular misalignment. The net radial force on the primary seal ring is always directed so as to produce a radial eccentricity which generates inward pumping. Although the radial force is usually very small, in some cases it may be one of the reasons for excessive leakage through both the primary and secondary seals of a radial face seal.

  7. Radial forces in a misaligned radial face seal

    NASA Technical Reports Server (NTRS)

    Etsion, I.

    1977-01-01

    Radial forces on the primary seal ring of a flat misaligned seal are analyzed, taking into account the radial variation in seal clearance. An analytical solution for both hydrostatic and hydrodynamic effects is presented that covers the whole range from zero to full angular misalignment. The net radial force on the primary seal ring is always directed so as to produce a radial eccentricity which generates inward pumping. Although the radial force is usually very small, in some cases it may be one of the reasons for excessive leakage through both the primary and secondary seals of a radial face seal.

  8. Erosion in radial inflow turbines. Volume 2: Balance of centrifugal and radial drag forces on erosive particles

    NASA Technical Reports Server (NTRS)

    Clevenger, W. B., Jr.; Tabakoff, W.

    1974-01-01

    The particle motion in two-dimensional free and forced inward flowing vortices is considered. A particle in such a flow field experiences a balance between the aerodynamic drag forces that tend to drive erosive particles toward the axis, and centrifugal forces that prevent these particles from traveling toward the axis. Results predict that certain sizes of particles will achieve a stable orbit about the turbine axis in the inward flowing free vortex. In this condition, the radial drag force is equal to the centrifugal force. The sizes of particles that will achieve a stable orbit is shown to be related to the gas flow velocity diagram at a particular radius. A second analysis yields a description of particle sizes that will experience a centrifugal force that is greater than the radial component of the aerodynamic drag force for a more general type of particle motion.

  9. Global Plate Velocities from the Global Positioning System

    NASA Technical Reports Server (NTRS)

    Larson, Kristine M.; Freymueller, Jeffrey T.; Philipsen, Steven

    1997-01-01

    We have analyzed 204 days of Global Positioning System (GPS) data from the global GPS network spanning January 1991 through March 1996. On the basis of these GPS coordinate solutions, we have estimated velocities for 38 sites, mostly located on the interiors of the Africa, Antarctica, Australia, Eurasia, Nazca, North America, Pacific, and South America plates. The uncertainties of the horizontal velocity components range from 1.2 to 5.0 mm/yr. With the exception of sites on the Pacific and Nazca plates, the GPS velocities agree with absolute plate model predictions within 95% confidence. For most of the sites in North America, Antarctica, and Eurasia, the agreement is better than 2 mm/yr. We find no persuasive evidence for significant vertical motions (less than 3 standard deviations), except at four sites. Three of these four were sites constrained to geodetic reference frame velocities. The GPS velocities were then used to estimate angular velocities for eight tectonic plates. Absolute angular velocities derived from the GPS data agree with the no net rotation (NNR) NUVEL-1A model within 95% confidence except for the Pacific plate. Our pole of rotation for the Pacific plate lies 11.5 deg west of the NNR NUVEL-1A pole, with an angular speed 10% faster. Our relative angular velocities agree with NUVEL-1A except for some involving the Pacific plate. While our Pacific-North America angular velocity differs significantly from NUVEL-1A, our model and NUVEL-1A predict very small differences in relative motion along the Pacific-North America plate boundary itself. Our Pacific-Australia and Pacific- Eurasia angular velocities are significantly faster than NUVEL-1A, predicting more rapid convergence at these two plate boundaries. Along the East Pacific Pise, our Pacific-Nazca angular velocity agrees in both rate and azimuth with NUVFL-1A.

  10. Theoretical implications of the galactic radial acceleration relation of McGaugh, Lelli, and Schombert

    NASA Astrophysics Data System (ADS)

    Nesbet, Robert K.

    2018-05-01

    Velocities in stable circular orbits about galaxies, a measure of centripetal gravitation, exceed the expected Kepler/Newton velocity as orbital radius increases. Standard Λ cold dark matter (ΛCDM) attributes this anomaly to galactic dark matter. McGaugh et al. have recently shown for 153 disc galaxies that observed radial acceleration is an apparently universal function of classical acceleration computed for observed galactic baryonic mass density. This is consistent with the empirical modified Newtonian dynamics (MOND) model, not requiring dark matter. It is shown here that suitably constrained ΛCDM and conformal gravity (CG) also produce such a universal correlation function. ΛCDM requires a very specific dark matter distribution, while the implied CG non-classical acceleration must be independent of galactic mass. All three constrained radial acceleration functions agree with the empirical baryonic v4 Tully-Fisher relation. Accurate rotation data in the nominally flat velocity range could distinguish between MOND, ΛCDM, and CG.

  11. The role of stellar radial motions in shaping galaxy surface brightness profiles

    NASA Astrophysics Data System (ADS)

    Ruiz-Lara, T.; Few, C. G.; Florido, E.; Gibson, B. K.; Pérez, I.; Sánchez-Blázquez, P.

    2017-12-01

    Aims: The physics driving features such as breaks observed in galaxy surface brightness (SB) profiles remains contentious. Here, we assess the importance of stellar radial motions in shaping their characteristics. Methods: We use the simulated Milky Way-mass cosmological discs from the Ramses Disc Environment Study (RaDES) to characterise the radial redistribution of stars in galaxies displaying type-I (pure exponentials), II (downbending), and III (upbending) SB profiles. We compare radial profiles of the mass fractions and the velocity dispersions of different sub-populations of stars according to their birth and current location. Results: Radial redistribution of stars is important in all galaxies regardless of their light profiles. Type-II breaks seem to be a consequence of the combined effects of outward-moving and accreted stars. The former produce shallower inner profiles (lack of stars in the inner disc) and accumulate material around the break radius and beyond, strengthening the break; the latter can weaken or even convert the break into a pure exponential. Further accretion from satellites can concentrate material in the outermost parts, leading to type-III breaks that can coexist with type-II breaks, but situated further out. Type-III galaxies would be the result of an important radial redistribution of material throughout the entire disc, as well as a concentration of accreted material in the outskirts. In addition, type-III galaxies display the most efficient radial redistribution and the largest number of accreted stars, followed by type-I and II systems, suggesting that type-I galaxies may be an intermediate case between types II and III. In general, the velocity dispersion profiles of all galaxies tend to flatten or even increase around the locations where the breaks are found. The age and metallicity profiles are also affected, exhibiting different inner gradients depending on their SB profile, being steeper in the case of type-II systems (as

  12. An experiment to measure the one-way velocity of propagation of electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Kolen, P.; Torr, D. G.

    1982-01-01

    An experiment involving commercially available instrumentation to measure the velocity of the earth with respect to absolute space is described. The experiment involves the measurement of the one-way propagation velocity of electromagnetic radiation down a high-quality coaxial cable. It is demonstrated that the experiment is both physically meaningful and exceedingly simple in concept and in implementation. It is shown that with currently available commercial equipment one might expect to detect a threshold value for the component of velocity of the earth's motion with respect to absolute space in the equatorial plane of approximately 10 km/s, which greatly exceeds the velocity resolution required to detect the motion of the solar system with respect to the center of the galaxy.

  13. Arthroscopic Repair of the Medial Meniscus Radial/Oblique Tear Prevents the Progression of Meniscal Extrusion in Mildly Osteoarthritic Knees.

    PubMed

    Furumatsu, Takayuki; Kodama, Yuya; Kamatsuki, Yusuke; Hino, Tomohito; Ozaki, Toshifumi

    2017-10-01

    Extrusion of the medial meniscus (MM) is associated with knee joint pain in osteoarthritic knees. The relationships among MM radial/oblique tears, MM extrusion (MME), and the effect of arthroscopic meniscal repair are not established. Here we evaluated the effects of arthroscopic all-inside MM repair on MME and the clinical outcomes in patients with radially oriented MM tears and mildly osteoarthritic knees. Twenty patients with a symptomatic radial or oblique tear of the MM posterior segment, MME ≥2.5 mm, and mildly osteoarthritic knees were treated using FasT-Fix 360 All-inside Meniscal Suture devices. We used magnetic resonance imaging (MRI) to measure the patients' MM body width (MMBW), absolute MME, and relative MME. The Japanese Knee Injury and Osteoarthritis Outcome Score, Lysholm, Tegner, IKDC Subjective Knee Evaluation, and Visual Analogue Scale scores were obtained. Arthroscopic all-inside MM repair prevented increases of absolute and relative MME. The preoperative and 3- and 12-month MRI-based MMBW values were similar. Over a 24-month follow-up after the MM repairs, the clinical scores showed significant improvements. Our results suggest that all-inside meniscal repairs would be useful in preventing the progression of MME in patients suffering from symptomatic MM radial/oblique tears associated with mildly osteoarthritic knees.

  14. A Doppler dimming determination of coronal outflow velocity

    NASA Technical Reports Server (NTRS)

    Strachan, Leonard; Kohl, John L.; Weiser, Heinz; Withbroe, George L.; Munro, Richard H.

    1993-01-01

    Outflow velocities in a polar coronal hole are derived from observations made during a 1982 sounding rocket flight. The velocity results are derived from a Doppler dimming analysis of resonantly scattered H I Ly-alpha. This analysis indicates radial outflow velocities of 217 km/s at 2 solar radii from sun-center with an uncertainty range of 153 to 251 km/s at a confidence level of 67 percent. These results are best characterized as strong evidence for supersonic outflow within 2 solar radii of sun-center in a polar coronal hole. Several means for obtaining improved accuracy in future observations are discussed.

  15. Depth-encoded dual beam phase-resolved Doppler OCT for Doppler-angle-independent flow velocity measurement

    NASA Astrophysics Data System (ADS)

    Qian, Jie; Cheng, Wei; Cao, Zhaoyuan; Chen, Xinjian; Mo, Jianhua

    2017-02-01

    Phase-resolved Doppler optical coherence tomography (PR-D-OCT) is a functional OCT imaging technique that can provide high-speed and high-resolution depth-resolved measurement on flow in biological materials. However, a common problem with conventional PR-D-OCT is that this technique often measures the flow motion projected onto the OCT beam path. In other words, it needs the projection angle to extract the absolute velocity from PR-D-OCT measurement. In this paper, we proposed a novel dual-beam PR-D-OCT method to measure absolute flow velocity without separate measurement on the projection angle. Two parallel light beams are created in sample arm and focused into the sample at two different incident angles. The images produced by these two beams are encoded to different depths in single B-scan. Then the Doppler signals picked up by the two beams together with the incident angle difference can be used to calculate the absolute velocity. We validated our approach in vitro on an artificial flow phantom with our home-built 1060 nm swept source OCT. Experimental results demonstrated that our method can provide an accurate measurement of absolute flow velocity with independency on the projection angle.

  16. VizieR Online Data Catalog: Mesure de vitesses radiales. VII. (Duflot+, 1995)

    NASA Astrophysics Data System (ADS)

    Duflot, M.; Fehrenbach, C.; Mannone, R.; Burnage, R.; Genty, V.

    1995-01-01

    We publish 734 radial velocities of stars distributed in 28 fields of 4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot et al. 1990 and 1992), using the Fehrenbach objective prism method. (2 data files).

  17. Upper- and mid-crustal radial anisotropy beneath the central Himalaya and southern Tibet from seismic ambient noise tomography

    NASA Astrophysics Data System (ADS)

    Guo, Zhi; Gao, Xing; Wang, Wei; Yao, Zhenxing

    2012-05-01

    Through analysis of the Rayleigh wave and Love wave empirical Green's functions recovered from cross-correlation of seismic ambient noise, we image the radial anisotropy and shear wave velocity structure beneath southern Tibet and the central Himalaya. Dense ray path coverage from 22 broadband seismic stations deployed by the Himalayan Nepal Tibet Seismic Experiment project provides the unprecedented opportunity to resolve the spatial distribution of the radial anisotropy within the crust of the central Himalaya and southern Tibet. In the shallow subsurface, the obtained results indicate significant radial anisotropy with negative magnitude (VSV > VSH) mainly associated with the Indus Yarlung Suture and central Himalaya, possibly related to the fossil microcracks or metamorphic foliations formed during the uplifting of the Tibetan Plateau. With increasing depth, the magnitude of radial anisotropy varies from predominantly negative to predominantly positive, and a mid-crustal layer with prominent positive radial anisotropy (VSV < VSH) has been detected. The top of the mid-crustal anisotropic layer correlates nicely with the starting depth of the mid-crustal lower velocity layers detected in our previous study. The spatial correlation of the positive radial anisotropy layers and mid-crustal lower velocity layers might suggest lateral crustal channel flow induced alignment of mineral grains, most likely micas or amphiboles, within the mid-crust of the central Himalaya and southern Tibet. This observation provides independent seismic evidence to support the thermo-mechanical model, which involves the southward extrusion of a low viscosity mid-crustal channel driven by the denudation effect focused at the southern flank of the Tibetan Plateau to explain the tectonic evolution of the Tibetan-Himalayan orogen.

  18. The influence of convective blueshift on radial velocities of F, G, and K stars

    NASA Astrophysics Data System (ADS)

    Bauer, F. F.; Reiners, A.; Beeck, B.; Jeffers, S. V.

    2018-02-01

    Context. Apparent radial velocity (RV) signals induced by stellar surface features such as spots and plages can result in a false planet detection or hide the presence of an orbiting planet. Our ability to detect rocky exoplanets is currently limited by our understanding of such stellar signals. Aims: We model RV variations caused by active regions on the stellar surface of typical exoplanet-hosting stars of spectral type F, G, and K. We aim to understand how the stellar magnetic field strength, convective blueshift, and spot temperatures can influence RV signals caused by active regions. Methods: We use magneto-hydrodynamic (MHD) simulations for stars with spectral types F3V, a G2V, and a K5V. We quantify the impact of the magnetic field strength inside active regions on the RV measurement using the magnetic and non-magnetic FeI lines at 6165 Å and 6173 Å. We also quantify the impact of spot temperature and convective blueshift on the measured RV values. Results: Increasing the magnetic field strength increases the efficiency to suppress convection in active regions which results in an asymmetry between red- and blueshifted parts of the RV curves. A stronger suppression of convection also leads to an observed increase in RV amplitude for stronger magnetic fields. The MHD simulations predict convective motions to be faster in hotter stars. The suppression of faster convection leads to a stronger RV amplitude increase in hotter stars when the magnetic field is increased. While suppression of convection increases the asymmetry in RV curves,c a decreasing spot temperature counteracts this effect. When using observed temperatures for dark spots in our simulations we find that convective blueshift effects are negligible.

  19. VizieR Online Data Catalog: Radial velocities of 35 cataclysmic variables (Thorstensen+, 2016)

    NASA Astrophysics Data System (ADS)

    Thorstensen, J. R.; Alper, E. H.; Weil, K. E.

    2017-02-01

    We present spectroscopic follow-up observations of 35 newly discovered cataclysmic variables (CVs), 32 of which were found by the Catalina Real Time Transient Surveys (CRTS; Drake et al. 2009, Cat. J/ApJ/696/870; Drake et al. 2014, Cat. J/MNRAS/441/1186; Breedt et al. 2014, Cat. J/MNRAS/443/3174), ASAS-SN (Shappee et al. 2014ApJ...788...48S), and/or MASTER (Lipunov et al. 2010AdAst2010E..30L). All our observations are from Michigan-Dartmouth-MIT (MDM) Observatory on Kitt Peak, Arizona. For nearly all the spectra, we used the "modspec" spectrograph (a description of the modspec can be found at http://mdm.kpno.noao.edu/Manuals/ModSpec/modspec_man.html) with a 600line/mm grating. We mostly used a SITe 20482 CCD detector, which yielded 2Å/pixel from 4210 to 7500Å, with declining throughput toward the ends of the spectral range. When this detector was unavailable, we used a very similar 10242 SITe detector ("Templeton"), which covered 4660 to 6730Å. The modspec was mounted mostly on the 2.4m Hiltner telescope, but for some of the brighter objects, we used the 1.3m McGraw-Hill telescope. For a few of the 1.3m spectra, we used the Mark III grism spectrograph, which covered 4580 to 6850Å at 2.3Å/pixel. On both telescopes and with both spectrographs, we used an Andor Ikon camera to view the reflective slit jaws through a microscope and guided the telescope with a separate off-axis guider. With this arrangement we could place any object that was bright enough for a usable spectrum in the slit and track it accurately even if the portion of the light spilling onto the slit jaws was invisible. Our emission-line radial velocities are almost entirely of Hα, since it almost always gives the best signal-to-noise ratio with our instrument. (3 data files).

  20. Search for Close-in Planets around Evolved Stars with Phase-curve variations and Radial Velocity Measurements

    NASA Astrophysics Data System (ADS)

    Hirano, Teruyuki; Sato, Bun'ei; Masuda, Kento; Benomar, Othman Michel; Takeda, Yoichi; Omiya, Masashi; Harakawa, Hiroki

    2016-10-01

    Tidal interactions are a key process to understand the evolution history of close-in exoplanets. But tidals still have a large uncertainty in their prediction for the damping timescales of stellar obliquity and semi-major axis. We have worked on a search for transiting giant planets around evolved stars, for which few close-in planets were discovered. It has been reported that evolved stars lack close-in planets, which is often attributed to the tidal evolution and/or engulfment of close-in planets by the hosts. Meanwhile, Kepler has detected a certain fraction of transiting planet candidates around evolved stars. Confirming the planetary nature for these candidates is especially important since the comparison between the occurrence rates of close-in planets around main sequence stars and evolved stars provides a unique opportunity to discuss the final stage of close-in planets. With the aim of confirming KOI planet candidates around evolved stars, we measured precision radial velocities (RVs) for evolved stars with transiting planet candidates using Subaru/HDS. We also developed a new code which simultaneously models and fits the observed RVs and phase-curve variations in the Kepler data (e.g., transits, stellar ellipsoidal variations, and planet emission/reflected light). As a result of applying the global fit to KOI giants/subgiants, we confirmed two giant planets around evolved stars (Kepler-91 and KOI-1894), as well as revealed that KOI-977 is more likely a false positive.

  1. Correlation between longitudinal, circumferential, and radial moduli in cortical bone: effect of mineral content.

    PubMed

    Macione, J; Depaula, C A; Guzelsu, N; Kotha, S P

    2010-07-01

    Previous studies indicate that changes in the longitudinal elastic properties of bone due to changes in mineral content are related to the longitudinal strength of bone tissue. Changes in mineral content are expected to affect bone tissue mechanical properties along all directions, albeit to different extents. However, changes in tissue mechanical properties along the different directions are expected to be correlated to one another. In this study, we investigate if radial, circumferential, and longitudinal moduli are related in bone tissue with varying mineral content. Plexiform bovine femoral bone samples were treated in fluoride ion solutions for a period of 3 and 12 days to obtain bones with 20% and 32% lower effective mineral contents. Transmission ultrasound velocities were obtained in the radial, circumferential, and longitudinal axes of bone and combined with measured densities to obtain corresponding tensorial moduli. Results indicate that moduli decreased with fluoride ion treatments and were significantly correlated to one another (r(2) radial vs. longitudinal = 0.80, r(2) circumferential vs. longitudinal = 0.90, r(2) radial vs. circumferential = 0.85). Densities calculated from using ultrasound parameters, acoustic impedance and transmission velocities, were moderately correlated to those measured by the Archimedes principle (r(2)=0.54, p<0.01). These results suggest that radial and circumferential ultrasound measurements could be used to determine the longitudinal properties of bone and that ultrasound may not be able to predict in vitro densities of bones containing unbonded mineral. Published by Elsevier Ltd.

  2. Initial drop size and velocity distributions for airblast coaxial atomizers

    NASA Technical Reports Server (NTRS)

    Eroglu, H.; Chigier, N.

    1991-01-01

    Phase Doppler measurements were used to determine initial drop size and velocity distributions after a complete disintegration of coaxial liquid jets. The Sauter mean diameter (SMD) distribution was found to be strongly affected by the structure and behavior of the preceding liquid intact jet. The axial measurement stations were determined from the photographs of the coaxial liquid jet at very short distances (1-2 mm) downstream of the observed break-up locations. Minimum droplet mean velocities were found at the center, and maximum velocities were near the spray boundary. Size-velocity correlations show that the velocity of larger drops did not change with drop size. Drop rms velocity distributions have double peaks whose radial positions coincide with the maximum mean velocity gradients.

  3. Time-and-space resolved comparison of plasma expansion velocities in high-power diodes with velvet cathodes

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

    Yang Jie; Shu Ting; Fan Yuwei

    2013-01-28

    Time-and-space resolved comparison of the expansion velocities of plasmas in the planar diode with cathodes made of carbon velvet and polymer velvet has been performed. The diode was powered by a 200 kV, 110 ns pulse, and the peak current density was nearly 477 A/cm{sup 2}. A four-channel high speed framing camera (HSFC) was used to observe the formation and subsequent movement of the cathode plasmas. More accurate and valuable information about the two-dimensional (radial and axial) velocity components of the cathode plasmas was also acquired by utilizing the digital image processing methods. Additionally, the perveance model based on themore » Child-Langmuir law was used to calculate the expansion velocities of the diode plasmas from voltage and current profiles. Results from the two diagnostics were compared. Comparing the average values of the radial and axial velocity components indicated that the former was much larger than the latter during the initial period of the current. It was also found that the radial velocity of the carbon velvet cathode (190 cm/{mu}s) was much larger than that (90 cm/{mu}s) of the polymer velvet cathode. Moreover, the average values of both the radial and axial velocity components of the carbon velvet cathode were typically in the range of 2.5 {+-} 1.5 cm/{mu}s, which were smaller than that of the polymer velvet cathode during the current flattop. These results, together with the comparison of calculated values from the perveance model, indicated that the diode with carbon velvet cathode was more robust as compared with the polymer velvet cathode for the same electron current densities.« less

  4. Radial Flow Effects On A Retreating Rotor Blade

    DTIC Science & Technology

    2014-05-01

    blades which are subject to the coupled effects of reactive centrifugal and Coriolis forces unique to the rotating environment. These forces are...coupled effects of centrifugal and Coriolis forces in the rotating environment add more complexity to the flow characteristics [96]. McCroskey’s [74...disk will definitely cause some non-linear effects on the radial velocity profile. These effects are not investigated in this study. The next of

  5. Hydrodynamic structure of the boundary layers in a rotating cylindrical cavity with radial inflow

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

    Herrmann-Priesnitz, Benjamín, E-mail: bherrman@ing.uchile.cl; Torres, Diego A.; Advanced Mining Technology Center, Universidad de Chile, Av. Tupper 2007, Santiago

    A flow model is formulated to investigate the hydrodynamic structure of the boundary layers of incompressible fluid in a rotating cylindrical cavity with steady radial inflow. The model considers mass and momentum transfer coupled between boundary layers and an inviscid core region. Dimensionless equations of motion are solved using integral methods and a space-marching technique. As the fluid moves radially inward, entraining boundary layers develop which can either meet or become non-entraining. Pressure and wall shear stress distributions, as well as velocity profiles predicted by the model, are compared to numerical simulations using the software OpenFOAM. Hydrodynamic structure of themore » boundary layers is governed by a Reynolds number, Re, a Rossby number, Ro, and the dimensionless radial velocity component at the periphery of the cavity, U{sub o}. Results show that boundary layers merge for Re < < 10 and Ro > > 0.1, and boundary layers become predominantly non-entraining for low Ro, low Re, and high U{sub o}. Results may contribute to improve the design of technology, such as heat exchange devices, and turbomachinery.« less

  6. RR Lyrae, Delta Scuti, SX Phoenicis stars and Baade-Wesselink method. I - Photometric and radial velocity measurements of four field stars - RR Cet, DX Del, BS AQR and DY Peg

    NASA Astrophysics Data System (ADS)

    Meylan, G.; Burki, G.; Rufener, F.; Mayor, M.; Burnet, M.; Ischi, E.

    1986-04-01

    Simultaneous measurements in the Geneva seven-color photometry and in radial velocities with the spectrophotometer CORAVEL for two RR Lyrae, one Delta Scuti and one SX Phoenicis field star were obtained in order to apply the Baade-Wesselink method to these kinds of variable stars. As a first step, the data regarding the RR Cet, DX Del, BS Aqr, and DY Peg are presented. The target of this study will consist in determining the physical parameters (temperature, gravity, metal content, mass, luminosity) and distances of these stars.

  7. Development of a thermal and structural analysis procedure for cooled radial turbines

    NASA Technical Reports Server (NTRS)

    Kumar, Ganesh N.; Deanna, Russell G.

    1988-01-01

    A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine is considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analyses. An inviscid, quasi three-dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous one-dimensional internal flow code for the momentum and energy equation. These boundary conditions are input to a three-dimensional heat conduction code for calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results from this case are included.

  8. Development of a thermal and structural analysis procedure for cooled radial turbines

    NASA Technical Reports Server (NTRS)

    Kumar, Ganesh N.; Deanna, Russell G.

    1988-01-01

    A procedure for computing the rotor temperature and stress distributions in a cooled radial turbine are considered. Existing codes for modeling the external mainstream flow and the internal cooling flow are used to compute boundary conditions for the heat transfer and stress analysis. The inviscid, quasi three dimensional code computes the external free stream velocity. The external velocity is then used in a boundary layer analysis to compute the external heat transfer coefficients. Coolant temperatures are computed by a viscous three dimensional internal flow cade for the momentum and energy equation. These boundary conditions are input to a three dimensional heat conduction code for the calculation of rotor temperatures. The rotor stress distribution may be determined for the given thermal, pressure and centrifugal loading. The procedure is applied to a cooled radial turbine which will be tested at the NASA Lewis Research Center. Representative results are given.

  9. A theory of self-organized zonal flow with fine radial structure in tokamak

    NASA Astrophysics Data System (ADS)

    Zhang, Y. Z.; Liu, Z. Y.; Xie, T.; Mahajan, S. M.; Liu, J.

    2017-12-01

    The (low frequency) zonal flow-ion temperature gradient (ITG) wave system, constructed on Braginskii's fluid model in tokamak, is shown to be a reaction-diffusion-advection system; it is derived by making use of a multiple spatiotemporal scale technique and two-dimensional (2D) ballooning theory. For real regular group velocities of ITG waves, two distinct temporal processes, sharing a very similar meso-scale radial structure, are identified in the nonlinear self-organized stage. The stationary and quasi-stationary structures reflect a particular feature of the poloidal group velocity. The equation set posed to be an initial value problem is numerically solved for JET low mode parameters; the results are presented in several figures and two movies that show the spatiotemporal evolutions as well as the spectrum analysis—frequency-wave number spectrum, auto power spectrum, and Lissajous diagram. This approach reveals that the zonal flow in tokamak is a local traveling wave. For the quasi-stationary process, the cycle of ITG wave energy is composed of two consecutive phases in distinct spatiotemporal structures: a pair of Cavitons growing and breathing slowly without long range propagation, followed by a sudden decay into many Instantons that carry negative wave energy rapidly into infinity. A spotlight onto the motion of Instantons for a given radial position reproduces a Blob-Hole temporal structure; the occurrence as well as the rapid decay of Caviton into Instantons is triggered by zero-crossing of radial group velocity. A sample of the radial profile of zonal flow contributed from 31 nonlinearly coupled rational surfaces near plasma edge is found to be very similar to that observed in the JET Ohmic phase [J. C. Hillesheim et al., Phys. Rev. Lett. 116, 165002 (2016)]. The theory predicts an interior asymmetric dipole structure associated with the zonal flow that is driven by the gradients of ITG turbulence intensity.

  10. Analysis of the velocity law in the wind of the Be star Lambda Pavonis

    NASA Technical Reports Server (NTRS)

    Chen, Haiqi; Ringuelet, Adela; Sahade, Jorge; Kondo, Yoji

    1989-01-01

    This paper reanalyzes the IUE spectra of Lambda Pavonis secured in 1982 (Sahade et al.). It is found that the profiles of the broad UV lines are either rotationally broadened or nonrotationally broadened and that the rotationally broadened profiles can be sorted out in two groups characterized by rotational velocity values of 170 km/s and of 210 km/s, respectively. From the analysis of the rotational and of the radial velocities it is possible to distinguish two regions in the extended atmosphere of the star, namely, a region which is rotating and a region which is expanding. In the rotating region, the radial velocities are about zero, and the rotational velocity increases from 170 km/s to 250 km/s. In the expanding region, the rotational energy dissipates, the wind is accelerated to a maximum of -155 km/s, and farther out it decelerates.

  11. Sodium Velocity Maps on Mercury

    NASA Technical Reports Server (NTRS)

    Potter, A. E.; Killen, R. M.

    2011-01-01

    The objective of the current work was to measure two-dimensional maps of sodium velocities on the Mercury surface and examine the maps for evidence of sources or sinks of sodium on the surface. The McMath-Pierce Solar Telescope and the Stellar Spectrograph were used to measure Mercury spectra that were sampled at 7 milliAngstrom intervals. Observations were made each day during the period October 5-9, 2010. The dawn terminator was in view during that time. The velocity shift of the centroid of the Mercury emission line was measured relative to the solar sodium Fraunhofer line corrected for radial velocity of the Earth. The difference between the observed and calculated velocity shift was taken to be the velocity vector of the sodium relative to Earth. For each position of the spectrograph slit, a line of velocities across the planet was measured. Then, the spectrograph slit was stepped over the surface of Mercury at 1 arc second intervals. The position of Mercury was stabilized by an adaptive optics system. The collection of lines were assembled into an images of surface reflection, sodium emission intensities, and Earthward velocities over the surface of Mercury. The velocity map shows patches of higher velocity in the southern hemisphere, suggesting the existence of sodium sources there. The peak earthward velocity occurs in the equatorial region, and extends to the terminator. Since this was a dawn terminator, this might be an indication of dawn evaporation of sodium. Leblanc et al. (2008) have published a velocity map that is similar.

  12. Seismic velocities at the core-mantle boundary inferred from P waves diffracted around the core

    NASA Astrophysics Data System (ADS)

    Sylvander, Matthieu; Ponce, Bruno; Souriau, Annie

    1997-05-01

    The very base of the mantle is investigated with core-diffracted P-wave (P diff) travel times published by the International Seismological Centre (ISC) for the period 1964-1987. Apparent slownesses are computed for two-station profiles using a difference method. As the short-period P diff mostly sample a very thin layer above the core-mantle boundary (CMB), a good approximation of the true velocity structure at the CMB can be derived from the apparent slownesses. More than 27000 profiles are built, and this provides an unprecedented P diff sampling of the CMB. The overall slowness distribution has an average value of 4.62 s/deg, which corresponds to a velocity more than 4% lower than that of most mean radial models. An analysis of the residuals of absolute ISC P and P diff travel times is independently carried out and confirms this result. It also shows that the degree of heterogeneities is significantly higher at the CMB than in the lower mantle. A search for lateral velocity variations is then undertaken; a first large-scale investigation reveals the presence of coherent slowness anomalies of very large dimensions of the order of 3000 km at the CMB. A tomographic inversion is then performed, which confirms the existence of pronounced (±8-10%) lateral velocity variations and provides a reliable map of the heterogeneities in the northern hemisphere. The influence of heterogeneity in the overlying mantle, of noise in the data and of CMB topography is evaluated; it seemingly proves minor compared with the contribution of heterogeneities at the CMB. Our results support the rising idea of a thin, low-velocity laterally varying boundary layer at the base of the D″ layer. The two principal candidate interpretations are the occurrence of partial melting, or the presence of a chemically distinct layer, featuring infiltrated core material.

  13. Gyrokinetic statistical absolute equilibrium and turbulence

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

    Zhu Jianzhou; Hammett, Gregory W.

    2010-12-15

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: a finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N+1 quantities are conserved, corresponding to an energy invariant and N entropy-related invariants), the negative temperaturemore » states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.« less

  14. A study of quantification of aortic compliance in mice using radial acquisition phase contrast MRI

    NASA Astrophysics Data System (ADS)

    Zhao, Xuandong

    Spatiotemporal changes in blood flow velocity measured using Phase contrast Magnetic Resonance Imaging (MRI) can be used to quantify Pulse Wave Velocity (PWV) and Wall Shear Stress (WSS), well known indices of vessel compliance. A study was conducted to measure the PWV in the aortic arch in young healthy children using conventional phase contrast MRI and a post processing algorithm that automatically track the peak velocity in phase contrast images. It is shown that the PWV calculated using peak velocity-time data has less variability compared to that using mean velocity and flow. Conventional MR data acquisition techniques lack both the spatial and temporal resolution needed to accurately calculate PWV and WSS in in vivo studies using transgenic animal models of arterial diseases. Radial k-space acquisition can improve both spatial and temporal resolution. A major part of this thesis was devoted to developing technology for Radial Phase Contrast Magnetic Resonance (RPCMR) cine imaging on a 7 Tesla Animal scanner. A pulse sequence with asymmetric radial k-space acquisition was designed and implemented. Software developed to reconstruct the RPCMR images include gridding, density compensation and centering of k-Space that corrects the image ghosting introduced by hardware response time. Image processing software was developed to automatically segment the vessel lumen and correct for phase offset due to eddy currents. Finally, in vivo and ex vivo aortic compliance measurements were conducted in a well-established mouse model for atherosclerosis: Apolipoprotein E-knockout (ApoE-KO). Using RPCMR technique, a significantly higher PWV value as well as a higher average WSS was detected among 9 months old ApoE-KO mice compare to in wild type mice. A follow up ex-vivo test of tissue elasticity confirmed the impaired distensibility of aortic arteries among ApoE-KO mice.

  15. Relationship between throwing velocity, muscle power, and bar velocity during bench press in elite handball players.

    PubMed

    Marques, Mario C; van den Tilaar, Roland; Vescovi, Jason D; Gonzalez-Badillo, Juan Jose

    2007-12-01

    The purpose of this study was to examine the relationship between ball-throwing velocity during a 3-step running throw and dynamic strength, power, and bar velocity during a concentric-only bench-press exercise in team-handball players. Fourteen elite senior male team-handball players volunteered to participate. Each volunteer had power and bar velocity measured during a concentric-only bench-press test with 26, 36, and 46 kg, as well as having 1-repetition-maximum (1-RMBP) strength determined. Ball-throwing velocity was evaluated with a standard 3-step running throw using a radar gun. Ball-throwing velocity was related to the absolute load lifted during the 1-RMBP (r = .637, P = .014), peak power using 36 kg (r = .586, P = .028) and 46 kg (r = .582, P = .029), and peak bar velocity using 26 kg (r = .563, P = .036) and 36 kg (r = .625, P = .017). The results indicate that throwing velocity of elite team-handball players is related to maximal dynamic strength, peak power, and peak bar velocity. Thus, a training regimen designed to improve ball-throwing velocity in elite male team-handball players should include exercises that are aimed at increasing both strength and power in the upper body.

  16. Balance Velocities of the Greenland Ice Sheet

    NASA Technical Reports Server (NTRS)

    Joughin, Ian; Fahnestock, Mark; Ekholm, Simon; Kwok, Ron

    1997-01-01

    We present a map of balance velocities for the Greenland ice sheet. The resolution of the underlying DEM, which was derived primarily from radar altimetry data, yields far greater detail than earlier balance velocity estimates for Greenland. The velocity contours reveal in striking detail the location of an ice stream in northeastern Greenland, which was only recently discovered using satellite imagery. Enhanced flow associated with all of the major outlets is clearly visible, although small errors in the source data result in less accurate estimates of the absolute flow speeds. Nevertheless, the balance map is useful for ice-sheet modelling, mass balance studies, and field planning.

  17. Simultaneous Temperature and Velocity Measurements in a Large-Scale, Supersonic, Heated Jet

    NASA Technical Reports Server (NTRS)

    Danehy, P. M.; Magnotti, G.; Bivolaru, D.; Tedder, S.; Cutler, A. D.

    2008-01-01

    Two laser-based measurement techniques have been used to characterize an axisymmetric, combustion-heated supersonic jet issuing into static room air. The dual-pump coherent anti-Stokes Raman spectroscopy (CARS) measurement technique measured temperature and concentration while the interferometric Rayleigh scattering (IRS) method simultaneously measured two components of velocity. This paper reports a preliminary analysis of CARS-IRS temperature and velocity measurements from selected measurement locations. The temperature measurements show that the temperature along the jet axis remains constant while dropping off radially. The velocity measurements show that the nozzle exit velocity fluctuations are about 3% of the maximum velocity in the flow.

  18. Detection of Intracluster Gas Bulk Velocities in the Perseus and Centaurus Clusters

    NASA Astrophysics Data System (ADS)

    Dupke, Renato A.; Bregman, Joel N.

    We report the results of spatially resolved X-ray spectroscopy of 8 different ASCApointings distributed symmetrically around the center of the Perseus cluster. The outer region of the intracluster gas is roughly isothermal, with temperature ~ 6-7 keV, and metal abundance ~ 0.3 Solar. Spectral analysis of the central pointing is consistent with the presence of a cooling flow and a central metal abundance gradient. A significant velocity gradient is found along an axis highly discrepant with the major axis of the X-ray elongation. The radial velocity difference is found to be greater than 1000 km s-1Mpc-1 at the 90% confidence level. Simultaneous fittings of GIS 2 & 3 indicate that two symmetrically opposed regions have different radial velocities at the 95% confidence level and the F-test rules out constant velocities for these regions at the 99% level. Intrinsic short and long term variations of gain are unlikely (P < 0.03) to explain the velocity discrepancies. We also report the preliminary results of a similar analysis carried out for the Centaurus cluster, where long-exposure SIS data is available. We also find a significant velocity gradient near the central regions (3'-8' of Centaurus. If attributed to bulk rotation the correspondent circular velocity is ~1500±150 km s-1 (at 90% confidence). The line of maximum velocity gradient in Centaurus is near-perpendicular to the infalling galaxy group associated with NGC 4709.

  19. PlanetPack: A radial-velocity time-series analysis tool facilitating exoplanets detection, characterization, and dynamical simulations

    NASA Astrophysics Data System (ADS)

    Baluev, Roman V.

    2013-08-01

    We present PlanetPack, a new software tool that we developed to facilitate and standardize the advanced analysis of radial velocity (RV) data for the goal of exoplanets detection, characterization, and basic dynamical N-body simulations. PlanetPack is a command-line interpreter, that can run either in an interactive mode or in a batch mode of automatic script interpretation. Its major abilities include: (i) advanced RV curve fitting with the proper maximum-likelihood treatment of unknown RV jitter; (ii) user-friendly multi-Keplerian as well as Newtonian N-body RV fits; (iii) use of more efficient maximum-likelihood periodograms that involve the full multi-planet fitting (sometimes called as “residual” or “recursive” periodograms); (iv) easily calculatable parametric 2D likelihood function level contours, reflecting the asymptotic confidence regions; (v) fitting under some useful functional constraints is user-friendly; (vi) basic tasks of short- and long-term planetary dynamical simulation using a fast Everhart-type integrator based on Gauss-Legendre spacings; (vii) fitting the data with red noise (auto-correlated errors); (viii) various analytical and numerical methods for the tasks of determining the statistical significance. It is planned that further functionality may be added to PlanetPack in the future. During the development of this software, a lot of effort was made to improve the calculational speed, especially for CPU-demanding tasks. PlanetPack was written in pure C++ (standard of 1998/2003), and is expected to be compilable and useable on a wide range of platforms.

  20. The Radial Velocity Variability of the K-giant γ Draconis: Stellar Variability Masquerading as a Planet

    NASA Astrophysics Data System (ADS)

    Hatzes, A. P.; Endl, M.; Cochran, W. D.; MacQueen, P. J.; Han, I.; Lee, B.-C.; Kim, K.-M.; Mkrtichian, D.; Döllinger, M.; Hartmann, M.; Karjalainen, M.; Dreizler, S.

    2018-03-01

    We present precise stellar radial velocity (RV) measurements of γ Dra taken from 2003 to 2017. The data from 2003 to 2011 show coherent, long-lived variations with a period of 702 days. These variations are consistent with the presence of a planetary companion having m sin i = 10.7 M Jup whose orbital properties are typical for giant planets found around evolved stars. An analysis of the Hipparcos photometry, Ca II S-index measurements, and measurements of the spectral line shapes during this time show no variations with the RV of the planet, which seems to “confirm” the presence of the planet. However, RV measurements taken from 2011–2017 seem to refute this. From 2011–2013, the RV variations virtually disappear, only to return in 2014 but with a noticeable phase shift. The total RV variations are consistent either with amplitude variations on timescales of ≈10.6 year, or the beating effect between two periods of 666 and 801 days. It seems unlikely that both these signals stem from a two-planet system. A simple dynamical analysis indicates that there is only a 1%–2% chance that the two-planet system is stable. Rather, we suggest that this multi-periodic behavior may represent a new form of stellar variability, possibly related to oscillatory convective modes. If such intrinsic stellar variability is common around K giant stars and is attributed to planetary companions, then the planet occurrence rate among these stars may be significantly lower than thought.

  1. Absolute parameters of eclipsing binaries in Southern Hemisphere sky - II: QY Tel

    NASA Astrophysics Data System (ADS)

    Erdem, A.; Sürgit, D.; Engelbrecht, C. A.; van Heerden, H. P.; Manick, R.

    2016-11-01

    This paper presents the first analysis of spectroscopic and photometric observations of the neglected southern eclipsing binary star, QY Tel. Spectroscopic observations were carried out at the South African Astronomical Observatory in 2013. New radial velocity curves from this study and V light curves from the All Sky Automated Survey were solved simultaneously using modern light and radial velocity curve synthesis methods. The final model describes QY Tel as a detached binary star where both component stars fill at least half of their Roche limiting lobes. The masses and radii were found to be 1.32 (± 0.06) M⊙, 1.74 (± 0.15) R⊙ and 1.44 (± 0.09) M⊙, 2.70 (± 0.16) R⊙ for the primary and secondary components of the system, respectively. The distance to QY Tel was calculated as 365 (± 40) pc, taking into account interstellar extinction. The evolution case of QY Tel is also examined. Both components of the system are evolved main-sequence stars with an age of approximately 3.2 Gy, when compared to Geneva theoretical evolution models.

  2. Analytical estimates of radial segregation in Bridgman growth from low-level steady and periodic accelerations

    NASA Astrophysics Data System (ADS)

    Naumann, Robert J.; Baugher, Charles

    1992-08-01

    Estimates of the convective flows driven by horizontal temperature gradients in the vertical Bridgman configuration are made for dilute systems subject to the low level accelerations typical of the residual accelerations experienced by a spacecraft in low Earth orbit. The estimates are made by solving the Navier-Stokes momentum equation in one dimension. The mass transport equation is then solved in two dimensions using a first-order perturbation method. This approach is valid provided the convective velocities are small compared to the growth velocity which generally requires a reduced gravity environment. If this condition is satisfied, there will be no circulating cells, and hence no convective transport along the vertical axis. However, the variations in the vertical velocity with radius will give rise to radial segregation. The approximate analytical model developed here can predict the degree of radial segregation for a variety of material and processing parameters to an accuracy well within a factor of two as compared against numerical computations of the full set of Navier-Stokes equations for steady accelerations. It has the advantage of providing more insight into the complex interplay of the processing parameters and how they affect the solute distribution in the grown crystal. This could be extremely valuable in the design of low-gravity experiments in which the intent is to control radial segregation. Also, the analysis can be extended to consider transient and periodic accelerations, which is difficult and costly to do numerically. Surprisingly, it was found that the relative radial segregation falls as the inverse cube of the frequency for periodic accelerations whose periods are short compared with the characteristic diffusion time.

  3. Egomotion estimation with optic flow and air velocity sensors.

    PubMed

    Rutkowski, Adam J; Miller, Mikel M; Quinn, Roger D; Willis, Mark A

    2011-06-01

    We develop a method that allows a flyer to estimate its own motion (egomotion), the wind velocity, ground slope, and flight height using only inputs from onboard optic flow and air velocity sensors. Our artificial algorithm demonstrates how it could be possible for flying insects to determine their absolute egomotion using their available sensors, namely their eyes and wind sensitive hairs and antennae. Although many behaviors can be performed by only knowing the direction of travel, behavioral experiments indicate that odor tracking insects are able to estimate the wind direction and control their absolute egomotion (i.e., groundspeed). The egomotion estimation method that we have developed, which we call the opto-aeronautic algorithm, is tested in a variety of wind and ground slope conditions using a video recorded flight of a moth tracking a pheromone plume. Over all test cases that we examined, the algorithm achieved a mean absolute error in height of 7% or less. Furthermore, our algorithm is suitable for the navigation of aerial vehicles in environments where signals from the Global Positioning System are unavailable.

  4. 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.

  5. Radial profiles of velocity and pressure for condensation-induced hurricanes

    NASA Astrophysics Data System (ADS)

    Makarieva, A. M.; Gorshkov, V. G.

    2011-02-01

    The Bernoulli integral in the form of an algebraic equation is obtained for the hurricane air flow as the sum of the kinetic energy of wind and the condensational potential energy. With an account for the eye rotation energy and the decrease of angular momentum towards the hurricane center it is shown that the theoretical profiles of pressure and velocity agree well with observations for intense hurricanes. The previous order of magnitude estimates obtained in pole approximation are confirmed.

  6. Blending of Radial HF Radar Surface Current and Model Using ETKF Scheme For The Sunda Strait

    NASA Astrophysics Data System (ADS)

    Mujiasih, Subekti; Riyadi, Mochammad; Wandono, Dr; Wayan Suardana, I.; Nyoman Gede Wiryajaya, I.; Nyoman Suarsa, I.; Hartanto, Dwi; Barth, Alexander; Beckers, Jean-Marie

    2017-04-01

    Preliminary study of data blending of surface current for Sunda Strait-Indonesia has been done using the analysis scheme of the Ensemble Transform Kalman Filter (ETKF). The method is utilized to combine radial velocity from HF Radar and u and v component of velocity from Global Copernicus - Marine environment monitoring service (CMEMS) model. The initial ensemble is based on the time variability of the CMEMS model result. Data tested are from 2 CODAR Seasonde radar sites in Sunda Strait and 2 dates such as 09 September 2013 and 08 February 2016 at 12.00 UTC. The radial HF Radar data has a hourly temporal resolution, 20-60 km of spatial range, 3 km of range resolution, 5 degree of angular resolution and spatial resolution and 11.5-14 MHz of frequency range. The u and v component of the model velocity represents a daily mean with 1/12 degree spatial resolution. The radial data from one HF radar site is analyzed and the result compared to the equivalent radial velocity from CMEMS for the second HF radar site. Error checking is calculated by root mean squared error (RMSE). Calculation of ensemble analysis and ensemble mean is using Sangoma software package. The tested R which represents observation error covariance matrix, is a diagonal matrix with diagonal elements equal 0.05, 0.5 or 1.0 m2/s2. The initial ensemble members comes from a model simulation spanning a month (September 2013 or February 2016), one year (2013) or 4 years (2013-2016). The spatial distribution of the radial current are analyzed and the RMSE values obtained from independent HF radar station are optimized. It was verified that the analysis reproduces well the structure included in the analyzed HF radar data. More importantly, the analysis was also improved relative to the second independent HF radar site. RMSE of the improved analysis is better than first HF Radar site Analysis. The best result of the blending exercise was obtained for observation error variance equal to 0.05 m2/s2. This study is

  7. IN-SYNC. III. The Dynamical State of IC 348 - A Super-virial Velocity Dispersion and a Puzzling Sign of Convergence

    NASA Astrophysics Data System (ADS)

    Cottaar, Michiel; Covey, Kevin R.; Foster, Jonathan B.; Meyer, Michael R.; Tan, Jonathan C.; Nidever, David L.; Chojnowski, S. Drew; da Rio, Nicola; Flaherty, Kevin M.; Frinchaboy, Peter M.; Majewski, Steve; Skrutskie, Michael F.; Wilson, John C.; Zasowski, Gail

    2015-07-01

    Most field stars will have encountered the highest stellar density and hence the largest number of interactions in their birth environment. Yet the stellar dynamics during this crucial phase are poorly understood. Here we analyze the radial velocities measured for 152 out of 380 observed stars in the 2-6 Myr old star cluster IC 348 as part of the SDSS-III APOGEE. The radial velocity distribution of these stars is fitted with one or two Gaussians, convolved with the measurement uncertainties including binary orbital motions. Including a second Gaussian improves the fit; the high-velocity outliers that are best fit by this second component may either (1) be contaminants from the nearby Perseus OB2 association, (2) be a halo of ejected or dispersing stars from IC 348, or (3) reflect that IC 348 has not relaxed to a Gaussian velocity distribution. We measure a velocity dispersion for IC 348 of 0.72 ± 0.07 km s-1 (or 0.64 ± 0.08 km s-1 if two Gaussians are fitted), which implies a supervirial state, unless the gas contributes more to the gravitational potential than expected. No evidence is found for a dependence of this velocity dispersion on distance from the cluster center or stellar mass. We also find that stars with lower extinction (in the front of the cloud) tend to be redshifted compared with stars with somewhat higher extinction (toward the back of the cloud). This data suggest that the stars in IC 348 are converging along the line of sight. We show that this correlation between radial velocity and extinction is unlikely to be spuriously caused by the small cluster rotation of 0.024 ± 0.013 km s-1 arcmin-1 or by correlations between the radial velocities of neighboring stars. This signature, if confirmed, will be the first detection of line of sight convergence in a star cluster. Possible scenarios for reconciling this convergence with IC 348's observed supervirial state include: (a) the cluster is fluctuating around a new virial equilibrium after a recent

  8. Computer program for design analysis of radial-inflow turbines

    NASA Technical Reports Server (NTRS)

    Glassman, A. J.

    1976-01-01

    A computer program written in FORTRAN that may be used for the design analysis of radial-inflow turbines was documented. The following information is included: loss model (estimation of losses), the analysis equations, a description of the input and output data, the FORTRAN program listing and list of variables, and sample cases. The input design requirements include the power, mass flow rate, inlet temperature and pressure, and rotational speed. The program output data includes various diameters, efficiencies, temperatures, pressures, velocities, and flow angles for the appropriate calculation stations. The design variables include the stator-exit angle, rotor radius ratios, and rotor-exit tangential velocity distribution. The losses are determined by an internal loss model.

  9. High-resolution H -band Spectroscopy of Be Stars with SDSS-III/APOGEE. II. Line Profile and Radial Velocity Variability

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

    Chojnowski, S. Drew; Holtzman, Jon A.; Wisniewski, John P.

    2017-04-01

    We report on the H -band spectral variability of classical Be stars observed over the course of the Apache Point Galactic Evolution Experiment (APOGEE), one of four subsurveys comprising SDSS-III. As described in the first paper of this series, the APOGEE B-type emission-line (ABE) star sample was culled from the large number of blue stars observed as telluric standards during APOGEE observations. In this paper, we explore the multi-epoch ABE sample, consisting of 1100 spectra for 213 stars. These “snapshots” of the circumstellar disk activity have revealed a wealth of temporal variability including, but not limited to, gradual disappearance ofmore » the line emission and vice versa over both short and long timescales. Other forms of variability include variation in emission strength, emission peak intensity ratios, and emission peak separations. We also analyze radial velocities (RVs) of the emission lines for a subsample of 162 stars with sufficiently strong features, and we discuss on a case-by-case basis whether the RV variability exhibited by some stars is caused by binary motion versus dynamical processes in the circumstellar disks. Ten systems are identified as convincing candidates for binary Be stars with as of yet undetected companions.« less

  10. External force/velocity control for an autonomous rehabilitation robot

    NASA Astrophysics Data System (ADS)

    Saekow, Peerayuth; Neranon, Paramin; Smithmaitrie, Pruittikorn

    2018-01-01

    Stroke is a primary cause of death and the leading cause of permanent disability in adults. There are many stroke survivors, who live with a variety of levels of disability and always need rehabilitation activities on daily basis. Several studies have reported that usage of rehabilitation robotic devices shows the better improvement outcomes in upper-limb stroke patients than the conventional therapy-nurses or therapists actively help patients with exercise-based rehabilitation. This research focuses on the development of an autonomous robotic trainer designed to guide a stroke patient through an upper-limb rehabilitation task. The robotic device was designed and developed to automate the reaching exercise as mentioned. The designed robotic system is made up of a four-wheel omni-directional mobile robot, an ATI Gamma multi-axis force/torque sensor used to measure contact force and a microcontroller real-time operating system. Proportional plus Integral control was adapted to control the overall performance and stability of the autonomous assistive robot. External force control was successfully implemented to establish the behavioral control strategy for the robot force and velocity control scheme. In summary, the experimental results indicated satisfactorily stable performance of the robot force and velocity control can be considered acceptable. The gain tuning for proportional integral (PI) velocity control algorithms was suitably estimated using the Ziegler-Nichols method in which the optimized proportional and integral gains are 0.45 and 0.11, respectively. Additionally, the PI external force control gains were experimentally tuned using the trial and error method based on a set of experiments which allow a human participant moves the robot along the constrained circular path whilst attempting to minimize the radial force. The performance was analyzed based on the root mean square error (E_RMS) of the radial forces, in which the lower the variation in radial

  11. Recovering the full velocity and density fields from large-scale redshift-distance samples

    NASA Technical Reports Server (NTRS)

    Bertschinger, Edmund; Dekel, Avishai

    1989-01-01

    A new method for extracting the large-scale three-dimensional velocity and mass density fields from measurements of the radial peculiar velocities is presented. Galaxies are assumed to trace the velocity field rather than the mass. The key assumption made is that the Lagrangian velocity field has negligible vorticity, as might be expected from perturbations that grew by gravitational instability. By applying the method to cosmological N-body simulations, it is demonstrated that it accurately reconstructs the velocity field. This technique promises a direct determination of the mass density field and the initial conditions for the formation of large-scale structure from galaxy peculiar velocity surveys.

  12. Size-velocity distribution of large ejecta fragments

    NASA Technical Reports Server (NTRS)

    Vickery, A. M.

    1986-01-01

    The characteristics of three primary extraterrestrial craters and the associated craters were examined to generate a size-velocity distribution for large ejecta fragments. The lunar craters Copernicus and Aristillus and the Martian crater Dv on Olympus Mons were used. Attention was focused on the radial distances between the primary and secondary crater centers and the diameters of the secondaries. The primary craters selected are all relatively young, which avoided contamination of the data from secondaries from other primaries. Attempts were made to account for the speed of the hypervelocity impacts and the elemental compositions of the impactors. An apparent velocity cutoff of about 1 km/sec was observed for the secondaries, which implies that no meteoroid impacts can accelerate ejecta to escape velocities from the moon or Mars.

  13. Gyrokinetic Statistical Absolute Equilibrium and Turbulence

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

    Jian-Zhou Zhu and Gregory W. Hammett

    2011-01-10

    A paradigm based on the absolute equilibrium of Galerkin-truncated inviscid systems to aid in understanding turbulence [T.-D. Lee, "On some statistical properties of hydrodynamical and magnetohydrodynamical fields," Q. Appl. Math. 10, 69 (1952)] is taken to study gyrokinetic plasma turbulence: A finite set of Fourier modes of the collisionless gyrokinetic equations are kept and the statistical equilibria are calculated; possible implications for plasma turbulence in various situations are discussed. For the case of two spatial and one velocity dimension, in the calculation with discretization also of velocity v with N grid points (where N + 1 quantities are conserved, correspondingmore » to an energy invariant and N entropy-related invariants), the negative temperature states, corresponding to the condensation of the generalized energy into the lowest modes, are found. This indicates a generic feature of inverse energy cascade. Comparisons are made with some classical results, such as those of Charney-Hasegawa-Mima in the cold-ion limit. There is a universal shape for statistical equilibrium of gyrokinetics in three spatial and two velocity dimensions with just one conserved quantity. Possible physical relevance to turbulence, such as ITG zonal flows, and to a critical balance hypothesis are also discussed.« less

  14. The Contradiction Between the Measurement Theory of Quantum Mechanics and the Theory that the Velocity of Any Particle Can Not be Larger than the Velocity of Light

    NASA Technical Reports Server (NTRS)

    Shen, Y.; Shen, Z. J.; Shen, G. T.; Yang, B. C.

    1996-01-01

    By the measurement theory of quantum mechanics and the method of Fourier transform,we proved that the wave function psi(x,y,z,t)= (8/((2(pi)(2L(exp (1/2)))(exp 3))(Phi(L,t,x)Phi(L,t,y)Phi(L,t,z)). According to the theory that the velocity of any particle can not be larger than the velocity of light and the Born interpretation, when absolute value of delta greater than (ct+ L),Phi(L,t,delta) = 0. But according to the calculation, we proved that for some delta, even if absolute value of delta is greater than (ct+L), Phi(L,t,delta) is not equal to 0.

  15. The evolution of rotating stars. III - Predicted surface rotation velocities for stars which conserve total angular momentum

    NASA Technical Reports Server (NTRS)

    Endal, A. S.; Sofia, S.

    1979-01-01

    Predicted surface rotation velocities for Population I stars at 10, 7, 5, 3, and 1.5 solar masses are presented. The surface velocities were computed for angular momentum with no radial redistribution, complete redistribution, and partial redistribution as predicted by consideration of circulation currents in rotating stars. Near the main sequence, rotational effects can reduce the moment of inertia of a star, so nonrotating models underestimate the expected velocities for evolving stars. On the red giant branch, angular momentum redistribution reduces the surface velocity by a factor of 2 or more, relative to the velocity expected for no radial redistribution. This removes the discrepancy between predicted and observed rotation rates for the K giants and makes it unlikely that these stars lose significant amounts of angular momentum by stellar winds. Calculations indicate that improved observations of the red giants in the Hyades cluster can be used to determine how angular momentum is redistributed by convection

  16. Electrophysiological examination and high frequency ultrasonography for diagnosis of radial nerve torsion and compression

    PubMed Central

    Shi, Miao; Qi, Hengtao; Ding, Hongyu; Chen, Feng; Xin, Zhaoqin; Zhao, Qinghua; Guan, Shibing; Shi, Hao

    2018-01-01

    Abstract This study aims to evaluate the value of electrophysiological examination and high frequency ultrasonography in the differential diagnosis of radial nerve torsion and radial nerve compression. Patients with radial nerve torsion (n = 14) and radial nerve compression (n = 14) were enrolled. The results of neurophysiological and high frequency ultrasonography were compared. Electrophysiological examination and high-frequency ultrasonography had a high diagnostic rate for both diseases with consistent results. Of the 28 patients, 23 were positive for electrophysiological examination, showing decreased amplitude and decreased conduction velocity of radial nerve; however, electrophysiological examination cannot distinguish torsion from compression. A total of 27 cases showed positive in ultrasound examinations among all 28 cases. On ultrasound images, the nerve was thinned at torsion site whereas thickened at the distal ends of torsion. The diameter and cross-sectional area of torsion or compression determined the nerve damage, and ultrasound could locate the nerve injury site and measure the length of the nerve. Electrophysiological examination and high-frequency ultrasonography can diagnose radial neuropathy, with electrophysiological examination reflecting the neurological function, and high-frequency ultrasound differentiating nerve torsion from compression. PMID:29480857

  17. A comparison of light-harvesting performance of silicon nanocones and nanowires for radial-junction solar cells.

    PubMed

    Li, Yingfeng; Li, Meicheng; Fu, Pengfei; Li, Ruike; Song, Dandan; Shen, Chao; Zhao, Yan

    2015-06-26

    Silicon nanorod based radial-junction solar cells are competitive alternatives to traditional planar silicon solar cells. In various silicon nanorods, nanocone is always considered to be better than nanowire in light-absorption. Nevertheless, we find that this notion isn't absolutely correct. Silicon nanocone is indeed significantly superior over nanowire in light-concentration due to its continuous diameters, and thus resonant wavelengths excited. However, the concentrated light can't be effectively absorbed and converted to photogenerated carriers, since its propagation path in silicon nanocone is shorter than that in nanowire. The results provide critical clues for the design of silicon nanorod based radial-junction solar cells.

  18. The Origin of Radially Aligned Magnetic Fields in Young Supernova Remnants

    NASA Astrophysics Data System (ADS)

    Inoue, Tsuyoshi; Shimoda, Jiro; Ohira, Yutaka; Yamazaki, Ryo

    2013-08-01

    It has been suggested by radio observations of polarized synchrotron emissions that downstream magnetic fields in some young supernova remnants (SNRs) are oriented radially. We study the magnetic field distribution of turbulent SNRs driven by the Richtmyer-Meshkov instability (RMI)—in other words, the effect of rippled shock—by using three-dimensional magnetohydrodynamics simulations. We find that the induced turbulence has radially biased anisotropic velocity dispersion that leads to a selective amplification of the radial component of the magnetic field. The RMI is induced by the interaction between the shock and upstream density fluctuations. Future high-resolution polarization observations can distinguish the following candidates responsible for the upstream density fluctuations: (1) inhomogeneity caused by the cascade of large-scale turbulence in the interstellar medium, the so-called big power-law in the sky; (2) structures generated by the Drury instability in the cosmic-ray modified shock; and (3) fluctuations induced by the nonlinear feedback of the cosmic-ray streaming instability.

  19. Monte-Carlo Method Application for Precising Meteor Velocity from TV Observations

    NASA Astrophysics Data System (ADS)

    Kozak, P.

    2014-12-01

    Monte-Carlo method (method of statistical trials) as an application for meteor observations processing was developed in author's Ph.D. thesis in 2005 and first used in his works in 2008. The idea of using the method consists in that if we generate random values of input data - equatorial coordinates of the meteor head in a sequence of TV frames - in accordance with their statistical distributions we get a possibility to plot the probability density distributions for all its kinematical parameters, and to obtain their mean values and dispersions. At that the theoretical possibility appears to precise the most important parameter - geocentric velocity of a meteor - which has the highest influence onto precision of meteor heliocentric orbit elements calculation. In classical approach the velocity vector was calculated in two stages: first we calculate the vector direction as a vector multiplication of vectors of poles of meteor trajectory big circles, calculated from two observational points. Then we calculated the absolute value of velocity independently from each observational point selecting any of them from some reasons as a final parameter. In the given method we propose to obtain a statistical distribution of velocity absolute value as an intersection of two distributions corresponding to velocity values obtained from different points. We suppose that such an approach has to substantially increase the precision of meteor velocity calculation and remove any subjective inaccuracies.

  20. Gas dynamics of a supersonic radial jet. Part II

    NASA Astrophysics Data System (ADS)

    Kosarev, V. F.; Klinkov, S. V.; Zaikovskii, V. N.

    2016-05-01

    The paper presents the radial distributions of the pressure measured with a Pitot tube for the case of a radial jet with/without swirling of the input flow in the pre-chamber; the length of the supersonic part of the jet, dependency of the jet thickness as a function of the distance from the nozzle outlet, and approximating analytical formula for the jet thickness that generalizes the experimental data. Experimental data demonstrated that at the deposition distances lower than 4-6 gauges from the nozzle outlet, the solid particle velocity and temperature are almost uniform over the jet cross section. This means that the target surface can be allocated here without loss in coating quality and deposition coefficient. The maximal recommended distance where the deposition is still possible is the length of l s0 ~ 16 gauges.

  1. Radial Anisotropy in the Mantle Transition Zone and Its Implications

    NASA Astrophysics Data System (ADS)

    Chang, S. J.; Ferreira, A. M.

    2016-12-01

    Seismic anisotropy is a useful tool to investigate mantle flow, mantle convection, and the presence of melts in mantle, since it provides information on the direction of mantle flow or the orientation of melts by combining it with laboratory results in mineral physics. Although the uppermost and lowermost mantle with strong anisotropy have been well studied, anisotropic properties of the mantle transition zone is still enigmatic. We use a recent global radially anisotropic model, SGLOBE-rani, to examine the patterns of radial anisotropy in the mantle transition zone. Strong faster SV velocity anomalies are found in the upper transition zone beneath subduction zones in the western Pacific, which decrease with depth, thereby nearly isotropic in the lower transition zone. This may imply that the origin for the anisotropy is the lattice-preferred orientation of wadsleyite, the dominant anisotropic mineral in the upper transition zone. The water content in the upper transition zone may be inferred from radial anisotropy because of the report that anisotropic intensity depends on the water content in wadsleyite.

  2. Observation of Magnetic Radial Vortex Nucleation in a Multilayer Stack with Tunable Anisotropy.

    PubMed

    Karakas, Vedat; Gokce, Aisha; Habiboglu, Ali Taha; Arpaci, Sevdenur; Ozbozduman, Kaan; Cinar, Ibrahim; Yanik, Cenk; Tomasello, Riccardo; Tacchi, Silvia; Siracusano, Giulio; Carpentieri, Mario; Finocchio, Giovanni; Hauet, Thomas; Ozatay, Ozhan

    2018-05-08

    Recently discovered exotic magnetic configurations, namely magnetic solitons appearing in the presence of bulk or interfacial Dzyaloshinskii-Moriya Interaction (i-DMI), have excited scientists to explore their potential applications in emerging spintronic technologies such as race-track magnetic memory, spin logic, radio frequency nano-oscillators and sensors. Such studies are motivated by their foreseeable advantages over conventional micro-magnetic structures due to their small size, topological stability and easy spin-torque driven manipulation with much lower threshold current densities giving way to improved storage capacity, and faster operation with efficient use of energy. In this work, we show that in the presence of i-DMI in Pt/CoFeB/Ti multilayers by tuning the magnetic anisotropy (both in-plane and perpendicular-to-plane) via interface engineering and postproduction treatments, we can stabilize a variety of magnetic configurations such as Néel skyrmions, horseshoes and most importantly, the recently predicted isolated radial vortices at room temperature and under zero bias field. Especially, the radial vortex state with its absolute convergence to or divergence from a single point can potentially offer exciting new applications such as particle trapping/detrapping in addition to magnetoresistive memories with efficient switching, where the radial vortex state can act as a source of spin-polarized current with radial polarization.

  3. Flow-gated radial phase-contrast imaging in the presence of weak flow.

    PubMed

    Peng, Hsu-Hsia; Huang, Teng-Yi; Wang, Fu-Nien; Chung, Hsiao-Wen

    2013-01-01

    To implement a flow-gating method to acquire phase-contrast (PC) images of carotid arteries without use of an electrocardiography (ECG) signal to synchronize the acquisition of imaging data with pulsatile arterial flow. The flow-gating method was realized through radial scanning and sophisticated post-processing methods including downsampling, complex difference, and correlation analysis to improve the evaluation of flow-gating times in radial phase-contrast scans. Quantitatively comparable results (R = 0.92-0.96, n = 9) of flow-related parameters, including mean velocity, mean flow rate, and flow volume, with conventional ECG-gated imaging demonstrated that the proposed method is highly feasible. The radial flow-gating PC imaging method is applicable in carotid arteries. The proposed flow-gating method can potentially avoid the setting up of ECG-related equipment for brain imaging. This technique has potential use in patients with arrhythmia or weak ECG signals.

  4. Z-pinch Plasma Temperature and Implosion Velocity from Laboratory Plasma Jets using Thomson Scattering

    NASA Astrophysics Data System (ADS)

    Banasek, Jacob; Byvank, Tom; Kusse, Bruce; Hammer, David

    2016-10-01

    We discuss the use of collective Thomson scattering to determine the implosion velocity and other properties of laboratory plasma jets. The plasma jet is created using a 1 MA pulsed power machine with a 15 μm Al radial foil load. The Thomson scattering laser has a maximum energy of 10 J at 526.5 nm with a pulse duration of 3 ns. Using a time gated ICCD camera and spectrometer system we are able to record the scattered spectrum from 9 or 18 regions along the laser path with sub-mm spatial resolution. Collecting scattered radiation from the same area at two different angles simultaneously enables determination of both the radial and azimuthal velocities. The scattered spectrum for non-magnetized jets indicates a radial implosion velocity of 27 km/s into the jets. A determination of ion and electron temperatures from the scattered spectrum is in progress. Comparing results using a laser energy of 10 J and 1 J shows noticeable effects on plasma jet properties when using 10 J. Therefore the lower laser energy must be used to determine the plasma properties. This research is supported by the NNSA Stewardship Sciences Academic Programs under DOE Cooperative Agreement DE-NA0001836.

  5. L.D.V. measurements of unsteady flow fields in radial turbine

    NASA Astrophysics Data System (ADS)

    Tabakoff, W.; Pasin, M.

    1992-07-01

    Detailed measurements of an unsteady flow field within the inlet guide vanes (IGV) and the rotor of a radial inflow turbine were performed using a three component Laser Doppler Velocimeter (LDV) system together with a rotary encoder. The mean velocity, the flow angle and the turbulence contours for IGV passages are presented at four blade-to-blade planes for different rotor positions to give three dimensional, unsteady behavior of the IGV flow field. These results are compared with the measurements obtained in the same passage in the absence of the rotor. The flow field of the IGV passage was found to be affected by the presence of the rotor. The ratio of the tangential normal stresses to the radial normal stresses at the exit of the IGV was found to be more than doubled when compared to the case without the rotor. The rotor flow field measurements are presented as relative mean velocity and turbulence stress contours at various cross section planes throughout the rotor. The cross flow and turbulence stress levels were found to be influenced by the incidence angle. Transportation of the high turbulence fluid by the cross flow was observed downstream in the rotor blade passages.

  6. Flow fields behind a variable-area nozzle for radial turbines

    NASA Astrophysics Data System (ADS)

    Hayami, Hiroshi; Hyun, Yong-Ik; Senoo, Yasutoshi; Yamaguchi, Michiteru

    The flow fields behind a variable-area nozzle for radial turbines were measured in detail using a three-hole cobra probe in 15 cases, which are a combination of three nozzle throat areas (0.8, 1.0, and 1.4 times the rated area) and five values of the tip-clearance to blade-height ratio (between 0.0 to 0.099). The flow fields at different tip clearances are presented in contour maps, and the pitch mean values are discussed as spanwise distributions of total pressure loss, flow angle, and radial and tangential velocity components. It is shown that the intensity of swirl behind the nozzle is decreased and the pressure loss is increased with the tip clearance, and the effect is magnified as the blade loading is higher.

  7. Quality Control of The Miniature Exoplanet Radio Velocity Array(MINERVA)

    NASA Astrophysics Data System (ADS)

    Rivera García, Kevin O.; Eastman, Jason D.

    2017-01-01

    The MINiature Exoplanet Radial Velocity Array, also known as MINERVA , is a network of four robotic 0.7 meter telescopes that is conducting a Radial Velocity survey of the nearest, brightest stars in search of small and rocky exoplanets. The robotic telescope array is located in Fred Lawrence Whipple Observatory in Arizona. MINERVA began science operations in 2015 and we are constantly improving its observing efficiency. We will describe performance statistics that we have developed in Python to proactively identify problems before they impede observations. We have written code to monitor the pointing error for each telescope to ensure it will always be able to acquire a target in the 3 arcminute field of view of its acquisition camera, but there are still some issues that need to be identified. The end goal for this research is to automatically address any common malfunction that may cause the observation to fail and ultimately improve our observing efficiency.

  8. Potential of ultrasonic pulse velocity for evaluating the dimensional stability of oak and chestnut wood

    Treesearch

    Turker Dundar; Xiping Wang; Nusret As; Erkan Avci

    2016-01-01

    The objective of this study was to examine the potential of ultrasonic velocity as a rapid and nondestructive method to predict the dimensional stability of oak (Quercus petraea (Mattuschka) Lieblein) and chestnut (Castanea sativa Mill.) that are commonly used in flooring industry. Ultrasonic velocity, specific gravity, and radial, tangential and volumetric shrinkages...

  9. The Velocity Distribution of Isolated Radio Pulsars

    NASA Technical Reports Server (NTRS)

    Arzoumanian, Z.; Chernoff, D. F.; Cordes, J. M.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We infer the velocity distribution of radio pulsars based on large-scale 0.4 GHz pulsar surveys. We do so by modelling evolution of the locations, velocities, spins, and radio luminosities of pulsars; calculating pulsed flux according to a beaming model and random orientation angles of spin and beam; applying selection effects of pulsar surveys; and comparing model distributions of measurable pulsar properties with survey data using a likelihood function. The surveys analyzed have well-defined characteristics and cover approx. 95% of the sky. We maximize the likelihood in a 6-dimensional space of observables P, dot-P, DM, absolute value of b, mu, F (period, period derivative, dispersion measure, Galactic latitude, proper motion, and flux density). The models we test are described by 12 parameters that characterize a population's birth rate, luminosity, shutoff of radio emission, birth locations, and birth velocities. We infer that the radio beam luminosity (i) is comparable to the energy flux of relativistic particles in models for spin-driven magnetospheres, signifying that radio emission losses reach nearly 100% for the oldest pulsars; and (ii) scales approximately as E(exp 1/2) which, in magnetosphere models, is proportional to the voltage drop available for acceleration of particles. We find that a two-component velocity distribution with characteristic velocities of 90 km/ s and 500 km/ s is greatly preferred to any one-component distribution; this preference is largely immune to variations in other population parameters, such as the luminosity or distance scale, or the assumed spin-down law. We explore some consequences of the preferred birth velocity distribution: (1) roughly 50% of pulsars in the solar neighborhood will escape the Galaxy, while approx. 15% have velocities greater than 1000 km/ s (2) observational bias against high velocity pulsars is relatively unimportant for surveys that reach high Galactic absolute value of z distances, but is severe for

  10. Laser induced fluorescence measurements of ion velocity and temperature of drift turbulence driven sheared plasma flow in a linear helicon plasma device

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

    Chakraborty Thakur, S.; Fedorczak, N.; Manz, P.

    2012-08-15

    Using laser induced fluorescence (LIF), radial profiles of azimuthal ion fluid velocity and ion temperature are measured in the controlled shear de-correlation experiment (CSDX) linear helicon plasma device. Ion velocities and temperatures are derived from the measured Doppler broadened velocity distribution functions of argon ions. The LIF system employs a portable, high power (>300 mW), narrowband ({approx}1 MHz) tunable diode laser-based system operating at 668.614 nm. Previous studies in CSDX have shown the existence of a radially sheared azimuthal flow as measured with time delay estimation methods and Mach probes. Here, we report the first LIF measurements of sheared plasmamore » fluid flow in CSDX. Above a critical magnetic field, the ion fluid flow profile evolves from radially uniform to peaked on axis with a distinct reversed flow region at the boundary, indicating the development of a sheared azimuthal flow. Simultaneously, the ion temperature also evolves from a radially uniform profile to a profile with a gradient. Measurements in turbulent and coherent drift wave mode dominated plasmas are compared.« less

  11. Radial Domany-Kinzel models with mutation and selection

    NASA Astrophysics Data System (ADS)

    Lavrentovich, Maxim O.; Korolev, Kirill S.; Nelson, David R.

    2013-01-01

    We study the effect of spatial structure, genetic drift, mutation, and selective pressure on the evolutionary dynamics in a simplified model of asexual organisms colonizing a new territory. Under an appropriate coarse-graining, the evolutionary dynamics is related to the directed percolation processes that arise in voter models, the Domany-Kinzel (DK) model, contact process, and so on. We explore the differences between linear (flat front) expansions and the much less familiar radial (curved front) range expansions. For the radial expansion, we develop a generalized, off-lattice DK model that minimizes otherwise persistent lattice artifacts. With both simulations and analytical techniques, we study the survival probability of advantageous mutants, the spatial correlations between domains of neutral strains, and the dynamics of populations with deleterious mutations. “Inflation” at the frontier leads to striking differences between radial and linear expansions. For a colony with initial radius R0 expanding at velocity v, significant genetic demixing, caused by local genetic drift, occurs only up to a finite time t*=R0/v, after which portions of the colony become causally disconnected due to the inflating perimeter of the expanding front. As a result, the effect of a selective advantage is amplified relative to genetic drift, increasing the survival probability of advantageous mutants. Inflation also modifies the underlying directed percolation transition, introducing novel scaling functions and modifications similar to a finite-size effect. Finally, we consider radial range expansions with deflating perimeters, as might arise from colonization initiated along the shores of an island.

  12. Radial anisotropy of Northeast Asia inferred from Bayesian inversions of ambient noise data

    NASA Astrophysics Data System (ADS)

    Lee, S. J.; Kim, S.; Rhie, J.

    2017-12-01

    The eastern margin of the Eurasia plate exhibits complex tectonic settings due to interactions with the subducting Pacific and Philippine Sea plates and the colliding India plate. Distributed extensional basins and intraplate volcanoes, and their heterogeneous features in the region are not easily explained with a simple mechanism. Observations of radial anisotropy in the entire lithosphere and the part of the asthenosphere provide the most effective evidence for the deformation of the lithosphere and the associated variation of the lithosphere-asthenosphere boundary (LAB). To infer anisotropic structures of crustal and upper-mantle in this region, radial anisotropy is measured using ambient noise data. In a continuation of previous Rayleigh wave tomography study in Northeast Asia, we conduct Love wave tomography to determine radial anisotropy using the Bayesian inversion techniques. Continuous seismic noise recordings of 237 broad-band seismic stations are used and more than 55,000 group and phase velocities of fundamental mode are measured for periods of 5-60 s. Total 8 different types of dispersion maps of Love wave from this study (period 10-60 s), Rayleigh wave from previous tomographic study (Kim et al., 2016; period 8-70 s) and longer period data (period 70-200 s) from a global model (Ekstrom, 2011) are jointly inverted using a hierarchical and transdimensional Bayesian technique. For each grid-node, boundary depths, velocities and anisotropy parameters of layers are sampled simultaneously on the assumption of the layered half-space model. The constructed 3-D radial anisotropy model provides much more details about the crust and upper mantle anisotropic structures, and about the complex undulation of the LAB.

  13. Vortex Ring Dynamics in Radially Confined Domains

    NASA Astrophysics Data System (ADS)

    Stewart, Kelley; Niebel, Casandra; Jung, Sunghwan; Vlachos, Pavlos

    2010-11-01

    Vortex ring dynamics have been studied extensively in semi-infinite quiescent volumes. However, very little is known about vortex-ring formation in wall-bounded domains where vortex wall interaction will affect both the vortex ring pinch-off and propagation velocity. This study addresses this limitation and studies vortex formation in radially confined domains to analyze the affect of vortex-ring wall interaction on the formation and propagation of the vortex ring. Vortex rings were produced using a pneumatically driven piston cylinder arrangement and were ejected into a long cylindrical tube which defined the confined downstream domain. A range of confinement domains were studied with varying confinement diameters Velocity field measurements were performed using planar Time Resolved Digital Particle Image Velocimetry (TRDPIV) and were processed using an in-house developed cross-correlation PIV algorithm. The experimental analysis was used to facilitate the development of a theoretical model to predict the variations in vortex ring circulation over time within confined domains.

  14. SOAP-T: a tool to study the light curve and radial velocity of a system with a transiting planet and a rotating spotted star

    NASA Astrophysics Data System (ADS)

    Oshagh, M.; Boisse, I.; Boué, G.; Montalto, M.; Santos, N. C.; Bonfils, X.; Haghighipour, N.

    2013-01-01

    We present an improved version of SOAP named "SOAP-T", which can generate the radial velocity variations and light curves for systems consisting of a rotating spotted star with a transiting planet. This tool can be used to study the anomalies inside transit light curves and the Rossiter-McLaughlin effect, to better constrain the orbital configuration and properties of planetary systems and the active zones of their host stars. Tests of the code are presented to illustrate its performance and to validate its capability when compared with analytical models and real data. Finally, we apply SOAP-T to the active star, HAT-P-11, observed by the NASA Kepler space telescope and use this system to discuss the capability of this tool in analyzing light curves for the cases where the transiting planet overlaps with the star's spots. The tool's public interface is available at http://www.astro.up.pt/resources/soap-t/

  15. FORTRAN program for calculating velocities in the meridional plane of a turbomachine 1: Centrifugal compressor

    NASA Technical Reports Server (NTRS)

    Vanco, M. R.

    1972-01-01

    The program will determine the velocities in the meridional plane of a backward-swept impeller, a radial impeller, and a vaned diffuser. The velocity gradient equation with the assumption of a hub-to-shroud mean stream surface is solved along arbitrary quasi-orthogonals in the meridional plane. These quasi-orthogonals are fixed straight lines.

  16. NIRPS: an adaptive-optics assisted radial velocity spectrograph to chase exoplanets around M-stars

    NASA Astrophysics Data System (ADS)

    Wildi, F.; Blind, N.; Reshetov, V.; Hernandez, O.; Genolet, L.; Conod, U.; Sordet, M.; Segovilla, A.; Rasilla, J. L.; Brousseau, D.; Thibault, S.; Delabre, B.; Bandy, T.; Sarajlic, M.; Cabral, A.; Bovay, S.; Vallée, Ph.; Bouchy, F.; Doyon, R.; Artigau, E.; Pepe, F.; Hagelberg, J.; Melo, C.; Delfosse, X.; Figueira, P.; Santos, N. C.; González Hernández, J. I.; de Medeiros, J. R.; Rebolo, R.; Broeg, Ch.; Benz, W.; Boisse, I.; Malo, L.; Käufl, U.; Saddlemyer, L.

    2017-09-01

    Since 1st light in 2002, HARPS has been setting the standard in the exo-planet detection by radial velocity (RV) measurements[1]. Based on this experience, our consortium is developing a high accuracy near-infrared RV spectrograph covering YJH bands to detect and characterize low-mass planets in the habitable zone of M dwarfs. It will allow RV measurements at the 1-m/s level and will look for habitable planets around M- type stars by following up the candidates found by the upcoming space missions TESS, CHEOPS and later PLATO. NIRPS and HARPS, working simultaneously on the ESO 3.6m are bound to become a single powerful high-resolution, high-fidelity spectrograph covering from 0.4 to 1.8 micron. NIRPS will complement HARPS in validating earth-like planets found around G and K-type stars whose signal is at the same order of magnitude than the stellar noise. Because at equal resolving power the overall dimensions of a spectrograph vary linearly with the input beam étendue, spectrograph designed for seeing-limited observations are large and expensive. NIRPS will use a high order adaptive optics system to couple the starlight into a fiber corresponding to 0.4" on the sky as efficiently or better than HARPS or ESPRESSO couple the light 0.9" fiber. This allows the spectrograph to be very compact, more thermally stable and less costly. Using a custom tan(θ)=4 dispersion grating in combination with a start-of-the-art Hawaii4RG detector makes NIRPS very efficient with complete coverage of the YJH bands at 110'000 resolution. NIRPS works in a regime that is in-between the usual multi-mode (MM) where 1000's of modes propagates in the fiber and the single mode well suited for perfect optical systems. This regime called few-modes regime is prone to modal noise- Results from a significant R and D effort made to characterize and circumvent the modal noise show that this contribution to the performance budget shall not preclude the RV performance to be achieved.

  17. Absolute wind measurements in the lower thermosphere of Venus using infrared heterodyne spectroscopy

    NASA Technical Reports Server (NTRS)

    Goldstein, Jeffrey J.

    1990-01-01

    The first absolute wind velocities above the Venusian cloud-tops were obtained using NASA/Goddard infrared heterodyne spectrometers at the NASA Infrared Telescope Facility (IRTF) and the McMath Solar Telescope. Beam-integrated Doppler displacements in the non-thermal emission core of (12)C(16)O2 10.33 micron R(8) sampled the line of sight projection of the lower thermospheric wind field (100 to 120 km). A field-usable Lamb-dip laser stabilization system, developed for spectrometer absolute frequency calibration to less than + or - 0.1 MHz, allowed S/N-limited line of sight velocity resolution at the 1 m/s level. The spectrometer's diffraction-limited beam (1.7 arc-second HPBW at McMath, 0.9 arc-second HPBW at IRTF), and 1 to 2 arc-second seeing, provided the spatial resolution necessary for circulation model discrimination. Qualitative analysis of beam-integrated winds provided definitive evidence of a dominant subsolar-antisolar circulation in the lower thermosphere. Beam-integrated winds were modelled with a 100x100 grid over the beam, incorporating beam spatial rolloff and across-the-beam gradients in non-thermal emission intensity, line of sight projection geometry, and horizontal wind velocity. Horizontal wind velocity was derived from a 2-parameter model wind field comprised of subsolar-antisolar and zonal components. Best-fit models indicated a dominant subsolar-antisolar flow with 120 m/s cross-terminator winds and a retrograde zonal component with a 25 m/s equatorial velocity. A review of all dynamical indicators above the cloud-tops allowed development of an integrated and self-consistent picture of circulation in the 70 to 200 km range.

  18. Density fluctuation correlation measurements in ASDEX Upgrade using poloidal and radial correlation reflectometry

    NASA Astrophysics Data System (ADS)

    Prisiazhniuk, D.; Conway, G. D.; Krämer-Flecken, A.; Stroth, U.; the ASDEX Upgrade Team

    2018-07-01

    The poloidal correlation reflectometry diagnostic operated in ordinary mode with additional radial correlation channel is applied in this paper to investigate the correlation of the turbulent density fluctuations. The perpendicular and radial correlation lengths, l ⊥ and l r , the perpendicular velocity v⊥ and the dissipation (mutation) time τ d are measured simultaneously from the outer core to edge in the L-mode plasmas of ASDEX Upgrade. It is shown that in the outer core region (0.6 < ρ pol < 0.9) the measured correlation lengths scale with the drift wave length, l ⊥ ≈ 5ρ s and l r ≈ 10ρ s , while the dissipation time is inversely correlated with the velocity τ d ≈ 40/v ⊥(τ d is in μs and v ⊥ in km s–1). In the pedestal region (0.925 < ρ pol < 0.98), where the E × B shear flows are present, a loss of measured correlation is observed which can be explained by a combination of small propagation velocity and an additional reduction of τ d . In the E r well region (ρ pol ≈ 0.99), the measured perpendicular correlation length increases {l}\\perp ≈ 13{ρ }s and the radial correlation length decreases l r ≈ 4ρ s compared to the outer core values. The correlation measurements are interpreted in the frame of the linear regime of reflectometry (applied only to ρ pol < 0.9). Using the Born approximation we show that the finite wavenumber sensitivity of the reflectometer increases the measured l ⊥and l r , but does not affect the measured τ d . By the including diagnostic correction the real correlation lengths l ⊥ ≈ l r ≈ 3ρ s are estimated.

  19. Investigation of the Relationship between Undercooling and Solidification Velocity

    NASA Technical Reports Server (NTRS)

    Bayuzick, Robert J.; Hofmeister, William H.

    2004-01-01

    This work was aimed at reconciling the differences between experimental measurements of the theoretical predictions of the solidification velocity as a function of undercooling. The theory proposed by Boettinger, Coriell and Trivedi (the BCT theory) has been one of the most widely used models for describing the nature of the solidification of undercooled metals and alloys. However, for undercoolings greater than about 5% of the absolute melting temperature, there is considerable discrepancy between theory and experiment. At these large undercoolings, experimental results exhibit a much lessened dependency of solidification velocity on undercooling than is predicted by theory. Furthermore, unpredicted plateaus in the solidification velocity as a function of undercooling are observed.

  20. Laser Doppler anemometer signal processing for blood flow velocity measurements

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

    Borozdova, M A; Fedosov, I V; Tuchin, V V

    A new method for analysing the signal in a laser Doppler anemometer based on the differential scheme is proposed, which provides the flow velocity measurement in strongly scattering liquids, particularly, blood. A laser Doppler anemometer intended for measuring the absolute blood flow velocity in animal and human near-surface arterioles and venules is developed. The laser Doppler anemometer signal structure is experimentally studied for measuring the flow velocity in optically inhomogeneous media, such as blood and suspensions of scattering particles. The results of measuring the whole and diluted blood flow velocity in channels with a rectangular cross section are presented. (lasermore » applications and other topics in quantum electronics)« less

  1. Accretion-driven turbulence in filaments - I. Non-gravitational accretion

    NASA Astrophysics Data System (ADS)

    Heigl, S.; Burkert, A.; Gritschneder, M.

    2018-03-01

    We study accretion-driven turbulence for different inflow velocities in star-forming filaments using the code RAMSES. Filaments are rarely isolated objects and their gravitational potential will lead to radially dominated accretion. In the non-gravitational case, accretion by itself can already provoke non-isotropic, radially dominated turbulent motions responsible for the complex structure and non-thermal line widths observed in filaments. We find that there is a direct linear relation between the absolute value of the total density-weighted velocity dispersion and the infall velocity. The turbulent velocity dispersion in the filaments is independent of sound speed or any net flow along the filament. We show that the density-weighted velocity dispersion acts as an additional pressure term, supporting the filament in hydrostatic equilibrium. Comparing to observations, we find that the projected non-thermal line width variation is generally subsonic independent of inflow velocity.

  2. Stress wave velocity patterns in the longitudinal-radial plane of trees for defect diagnosis

    Treesearch

    Guanghui Li; Xiang Weng; Xiaocheng Du; Xiping Wang; Hailin Feng

    2016-01-01

    Acoustic tomography for urban tree inspection typically uses stress wave data to reconstruct tomographic images for the trunk cross section using interpolation algorithm. This traditional technique does not take into account the stress wave velocity patterns along tree height. In this study, we proposed an analytical model for the wave velocity in the longitudinal–...

  3. Gravitational constant is likely dependent on the absolute velocity of galaxy

    NASA Astrophysics Data System (ADS)

    Chen, Shao-Guang

    ) , n = 1369, G = 6.66964*10 (-8) . G shall change follow the galaxy absolut velocity V = c / n, which shall influence Astronomy, Astrophysics and the cosmic science especially the estimation for dark matter and dark energy. The absolute velocity and G of galaxy centrality are far less than that of solar system, which is likely the origin of Galaxies’s abnormal speed-distance curve and dark matter, dark energy. But the spectrum not change with V because of the spectrum is only determined by the alphaα (1nuυ_{0} or _{0}nuυ + 9 nuυ_{0}(0) nuυ or _{0}nuυnuυ (0) ) and independent of the G ( (n) m_{0} or (n) \\underline{m }_{0}).

  4. Divertor-leg instability for finite beta and radially-tilted divertor plate

    NASA Astrophysics Data System (ADS)

    Cohen, R. H.; Ryutov, D. D.

    2004-11-01

    Plasma in the divertor leg may experience a fast instability caused by sheath boundary conditions (BC). Perturbations cannot penetrate beyond the X point because of very strong shearing in its vicinity. Accordingly, this instability could increase cross-field transport in the divertor leg, and thereby reduce the heat load on the divertor plate, without having any appreciable negative effect on core plasma confinement. A way of describing the role of shearing in terms of the surface resistivity attributed to a ``control plane'' below the X point has recently been suggested (Contr. Plasma Phys., v. 44, p. 168, 2004). We use this BC, plus sheath BC at the divertor plate. We include effects of finite beta and of the radial tilt of the divertor plate. We optimize the radial tilt in order to maximize radial transport in divertor legs. We discuss experimental signatures of the instability: i) phase velocity and wave-numbers of the most unstable modes; ii) correlations between fluctuations of various parameters; and iii) the differences between fluctuations in the common and private flux regions.

  5. Quantity Effect of Radial Cracks on the Cracking Propagation Behavior and the Crack Morphology

    PubMed Central

    Chen, Jingjing; Xu, Jun; Liu, Bohan; Yao, Xuefeng; Li, Yibing

    2014-01-01

    In this letter, the quantity effect of radial cracks on the cracking propagation behavior as well as the circular crack generation on the impacted glass plate within the sandwiched glass sheets are experimentally investigated via high-speed photography system. Results show that the radial crack velocity on the backing glass layer decreases with the crack number under the same impact conditions during large quantities of repeated experiments. Thus, the “energy conversion factor” is suggested to elucidate the physical relation between the cracking number and the crack propagation speed. Besides, the number of radial crack also takes the determinative effect in the crack morphology of the impacted glass plate. This study may shed lights on understanding the cracking and propagation mechanism in laminated glass structures and provide useful tool to explore the impact information on the cracking debris. PMID:25048684

  6. Absolute Parameters and Physical Nature of the Low-amplitude Contact Binary HI Draconis

    NASA Astrophysics Data System (ADS)

    Papageorgiou, A.; Christopoulou, P.-E.

    2015-05-01

    We present a detailed investigation of the low-amplitude contact binary HI Dra based on the new VRcIc CCD photometric light curves (LCs) combined with published radial velocity (RV) curves. Our completely covered LCs were analyzed using PHOEBE and revealed that HI Dra is an overcontact binary with low fill-out factor f = 24 ± 4(%) and temperature difference between the components of 330 K. Two spotted models are proposed to explain the LC asymmetry, between which the A subtype of W UMa type eclipsing systems, with a cool spot on the less massive and cooler component, proves to be more plausible on evolutionary grounds. The results and stability of the solutions were explored by heuristic scan and parameter perturbation to provide a consistent and reliable set of parameters and their errors. Our photometric modeling and RV curve solution give the following absolute parameters of the hot and cool components, respectively: Mh = 1.72 ± 0.08 {{M}⊙ } and Mc = 0.43 ± 0.02 {{M}⊙ }, Rh = 1.98 ± 0.03 {{R}⊙ } and Rc = 1.08 ± 0.02 {{R}⊙ }, and Lh = 9.6 ± 0.1 {{L}⊙ } and Lc = 2.4 ± 0.1 {{L}⊙ }. Based on these results the initial masses of the progenitors (1.11 ± 0.03 {{M}⊙ } and 2.25 ± 0.07 {{M}⊙ }, respectively) and a rough estimate of the age of the system of 2.4 Gyr are discussed.

  7. Non-radial instabilities and progenitor asphericities in core-collapse supernovae

    NASA Astrophysics Data System (ADS)

    Müller, B.; Janka, H.-Th.

    2015-04-01

    Since core-collapse supernova simulations still struggle to produce robust neutrino-driven explosions in 3D, it has been proposed that asphericities caused by convection in the progenitor might facilitate shock revival by boosting the activity of non-radial hydrodynamic instabilities in the post-shock region. We investigate this scenario in depth using 42 relativistic 2D simulations with multigroup neutrino transport to examine the effects of velocity and density perturbations in the progenitor for different perturbation geometries that obey fundamental physical constraints (like the anelastic condition). As a framework for analysing our results, we introduce semi-empirical scaling laws relating neutrino heating, average turbulent velocities in the gain region, and the shock deformation in the saturation limit of non-radial instabilities. The squared turbulent Mach number, , reflects the violence of aspherical motions in the gain layer, and explosive runaway occurs for ≳ 0.3, corresponding to a reduction of the critical neutrino luminosity by ˜ 25 per cent compared to 1D. In the light of this theory, progenitor asphericities aid shock revival mainly by creating anisotropic mass flux on to the shock: differential infall efficiently converts velocity perturbations in the progenitor into density perturbations δρ/ρ at the shock of the order of the initial convective Mach number Maprog. The anisotropic mass flux and ram pressure deform the shock and thereby amplify post-shock turbulence. Large-scale (ℓ = 2, ℓ = 1) modes prove most conducive to shock revival, whereas small-scale perturbations require unrealistically high convective Mach numbers. Initial density perturbations in the progenitor are only of the order of Ma_prog^2 and therefore play a subdominant role.

  8. Absolute total and partial dissociative cross sections of pyrimidine at electron and proton intermediate impact velocities

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

    Wolff, Wania, E-mail: wania@if.ufrj.br; Luna, Hugo; Sigaud, Lucas

    Absolute total non-dissociative and partial dissociative cross sections of pyrimidine were measured for electron impact energies ranging from 70 to 400 eV and for proton impact energies from 125 up to 2500 keV. MOs ionization induced by coulomb interaction were studied by measuring both ionization and partial dissociative cross sections through time of flight mass spectrometry and by obtaining the branching ratios for fragment formation via a model calculation based on the Born approximation. The partial yields and the absolute cross sections measured as a function of the energy combined with the model calculation proved to be a useful toolmore » to determine the vacancy population of the valence MOs from which several sets of fragment ions are produced. It was also a key point to distinguish the dissociation regimes induced by both particles. A comparison with previous experimental results is also presented.« less

  9. Radial velocities of very low mass stars and candidate brown dwarf members of the Hyades and Pleiades, 2

    NASA Technical Reports Server (NTRS)

    Stauffer, John R.; Liebert, James; Giampapa, Mark

    1995-01-01

    We have determined H alpha equivalent widths and radial velocities with 1 sigma accuracies of approximately 5 km/s for approximately 20 candidate very low mass members of the Pleiades cluster and for a few proposed very low mass members of the Hyades. Most of the Pleiades targets were selected from the recent Hambly, Hawkins, and Jameson proper motion survey, where they were identified as probable Pleiades brown dwarfs with an age spread from 3 to 70 Myr. Our spectroscopic data and a reinterpretation of the photometric data confirm that these objects are indeed likely Pleiades members; however, we believe that they more likely have masses slightly above the hydrogen burning mass limit and that there is no firm evidence for an age spread amongst these stars. All of the very low mass Pleiades and Hyades members show H alpha in emission. However, the ratio of H alpha flux to biometric flux in the Pleiades shows a maximum near M(sub Bol) approximately equal to 9.5 (M approximately equal to 0.3 solar mass) and a sharp decrease to lower masses. This break occurs at the approximate mass where low mass stars are expected to become fully convective, and it is tempting to assume that the decrease in H alpha flux is caused by some change in the behavior of stellar dynamos at this mass. We do not see a similar break in activity at this mass in the Hyades. We discuss possible evolutionary explanations for this difference in the H alpha activity between the two clusters.

  10. Spatially and Temporally Resolved Measurements of Velocity in a H2-air Combustion-Heated Supersonic Jet

    NASA Technical Reports Server (NTRS)

    Bivolaru, Daniel; Cutler, Andrew D.; Danehy, Paul M.; Gaffney, Richard L.; Baurle, Robert a.

    2009-01-01

    This paper presents simultaneous measurements at multiple points of two orthogonal components of flow velocity using a single-shot interferometric Rayleigh scattering (IRS) technique. The measurements are performed on a large-scale Mach 1.6 (Mach 5.5 enthalpy) H2-air combustion jet during the 2007 test campaign in the Direct Connect Supersonic Combustion Test facility at NASA Langley Research Center. The measurements are performed simultaneously with CARS (Coherent Anti-stokes Raman Spectroscopy) using a combined CARS-IRS instrument with a common path 9-nanosecond pulsed, injection-seeded, 532-nm Nd:YAG laser probe pulse. The paper summarizes the measurements of velocities along the core of the vitiated air flow as well as two radial profiles. The average velocity measurement near the centerline at the closest point from the nozzle exit compares favorably with the CFD calculations using the VULCAN code. Further downstream, the measured axial velocity shows overall higher values than predicted with a trend of convergence at further distances. Larger discrepancies are shown in the radial profiles.

  11. A Gaia study of the Hyades open cluster

    NASA Astrophysics Data System (ADS)

    Reino, Stella; de Bruijne, Jos; Zari, Eleonora; d'Antona, Francesca; Ventura, Paolo

    2018-03-01

    We present a study of the membership of the Hyades open cluster, derive kinematically-modelled parallaxes of its members, and study the colour-absolute magnitude diagram of the cluster. We use Gaia DR1 Tycho-Gaia Astrometric Solution (TGAS) data complemented by Hipparcos-2 data for bright stars not contained in TGAS. We supplement the astrometric data with radial velocities collected from a dozen literature sources. By assuming that all cluster members move with the mean cluster velocity to within the velocity dispersion, we use the observed and the expected motions of the stars to determine individual cluster membership probabilities. We subsequently derive improved parallaxes through maximum-likelihood kinematic modelling of the cluster. This method has an iterative component to deal with 'outliers', caused for instance by double stars or escaping members. Our method extends an existing method and supports the mixed presence of stars with and without radial velocities. We find 251 candidate members, 200 of which have a literature radial velocity, and 70 of which are new candidate members with TGAS astrometry. The cluster is roughly spherical in its centre but significantly flattened at larger radii. The observed colour-absolute magnitude diagram shows a clear binary sequence. The kinematically-modelled parallaxes that we derive are a factor ˜1.7 / 2.9 more precise than the TGAS / Hipparcos-2 values and allow to derive an extremely sharp main sequence. This sequence shows evidence for fine-detailed structure which is elegantly explained by the full spectrum turbulence model of convection.

  12. Absolute atomic hydrogen densities in a radio frequency discharge measured by two-photon laser induced fluorescence imaging

    NASA Astrophysics Data System (ADS)

    Chérigier, L.; Czarnetzki, U.; Luggenhölscher, D.; Schulz-von der Gathen, V.; Döbele, H. F.

    1999-01-01

    Absolute atomic hydrogen densities were measured in the gaseous electronics conference reference cell parallel plate reactor by Doppler-free two-photon absorption laser induced fluorescence spectroscopy (TALIF) at λ=205 nm. The capacitively coupled radio frequency discharge was operated at 13.56 MHz in pure hydrogen under various input power and pressure conditions. The Doppler-free excitation technique with an unfocused laser beam together with imaging the fluorescence radiation by an intensified charge coupled device camera allows instantaneous spatial resolution along the radial direction. Absolute density calibration is obtained with the aid of a flow tube reactor and titration with NO2. The influence of spatial intensity inhomogenities along the laser beam and subsequent fluorescence are corrected by TALIF in xenon. A full mapping of the absolute density distribution between the electrodes was obtained. The detection limit for atomic hydrogen amounts to about 2×1018 m-3. The dissociation degree is of the order of a few percent.

  13. Rate of radial transport of plasma in Saturn’s inner magnetosphere

    NASA Astrophysics Data System (ADS)

    Chen, Y.; Hill, T. W.

    2009-12-01

    The Cassini Plasma Spectrometer (CAPS) and the Cassini Magnetospheric Imaging Instrument (MIMI) frequently observe longitudinally localized injection and drift dispersion of hot plasma in Saturn’s magnetosphere. These signatures provide direct evidence for the major convective process in the inner magnetosphere of a rapidly rotating planet, in which the radial transport of plasma comprises hot, tenuous plasma moving inward and cooler, denser plasma moving outward. These injection events have been found to occupy only a small fraction of the total available longitudinal space, indicating that the inflow speed is probably much larger than the outflow speed. We set the local corotation speed as the upper limit of inflow velocities, and deduce the corresponding radial velocities of the outflowing flux tubes by analyzing the width of injection structures and assuming that the total potential drop around a given L-shell is zero. We then estimate an upper limit to the plasma outward mass transport rate, which turns out to be somewhat larger than previous estimates of the Enceladus source rate (e.g., Pontius and Hill, 2006). An important assumption in this study is that the plasma is largely confined to a thin equatorial sheet, and we have applied a centrifugal scale height model developed by Hill and Michel [1976].

  14. Laser measurements of unsteady flow field in a radial turbine guide vanes

    NASA Astrophysics Data System (ADS)

    Pasin, M.; Tabakoff, W.

    1992-01-01

    Detailed measurements of a unsteady flow field within the inlet guide vanes (IGV) of a radial inflow turbine were performed using a three component Laser Doppler Velocimeter (LDV) system. The mean velocity, the flow angle and the turbulence results are presented at the midspan plane for different rotor positions. These results are compared with the measurements obtained in the same passage in the absence of the rotor.

  15. The Radial Flow Speed of the Neutral Hydrogen in the Oval Distortion of NGC 4736

    NASA Astrophysics Data System (ADS)

    Speights, Jason; Benton, Allen; Reimer, Rebecca; Lemaire, Robert; Godwin, Caleb

    2017-01-01

    Radial flows are difficult to measure in the presence of elliptical flows. This is because the model describing the observed velocity field when both kinds of flows are present is degenerate in the unknown parameters. In this poster we show that the degeneracy can be overcome if the pattern speed and position angle of the elliptical flows are known. The method is demonstrated for NGC 4736 using 3.6 micrometer and neutral hydrogen data. We find a mean inward radial flow speed of 5.6 +/- 1.7 km/s in the region of the oval distortion.

  16. Radial pressure profiles in a cold‐flow gas‐solid vortex reactor

    PubMed Central

    Pantzali, Maria N.; Kovacevic, Jelena Z.; Marin, Guy B.; Shtern, Vladimir N.

    2015-01-01

    A unique normalized radial pressure profile characterizes the bed of a gas‐solid vortex reactor over a range of particle densities and sizes, solid capacities, and gas flow rates: 950–1240 kg/m3, 1–2 mm, 2 kg to maximum solids capacity, and 0.4–0.8 Nm3/s (corresponding to gas injection velocities of 55–110 m/s), respectively. The combined momentum conservation equations of both gas and solid phases predict this pressure profile when accounting for the corresponding measured particle velocities. The pressure profiles for a given type of particles and a given solids loading but for different gas injection velocities merge into a single curve when normalizing the pressures with the pressure value downstream of the bed. The normalized—with respect to the overall pressure drop—pressure profiles for different gas injection velocities in particle‐free flow merge in a unique profile. © 2015 The Authors AIChE Journal published by Wiley Periodicals, Inc. on behalf of American Institute of Chemical Engineers AIChE J, 61: 4114–4125, 2015 PMID:27667827

  17. Radial evolution of the solar wind from IMP 8 to Voyager 2

    NASA Technical Reports Server (NTRS)

    Richardson, John D.; Paularena, Karolen I.; Lazarus, Alan J.; Belcher, John W.

    1995-01-01

    Voyager 2 and Interplanetary Monitoring Platform (IMP) 8 data from 1977 through 1994 are presented and compared. Radial velocity and temperature structures remain intact over the distance from 1 to 43 AU, but density structures do not. Temperature and velocity changes are correlated and nearly in phase at 1 AU, but in the outer heliosphere temperature changes lead velocity changes by tens of days. Solar cycle variations are detected by both spacecraft, with minima in flux density and dynamic pressure near solar maxima. Differences between Voyager 2 and IMP 8 observations near the solar minimum in 1986-1987 are attributed to latitudinal gradients in solar wind properties. Solar rotation variations are often present even at 40 AU. The Voyager 2 temperature profile is best fit with a R(exp -0.49 +/- 0.01) decrease, much less steep than an adiabatic profile.

  18. Absolute and convective instabilities in combined Couette-Poiseuille flow past a neo-Hookean solid

    NASA Astrophysics Data System (ADS)

    Patne, Ramkarn; Shankar, V.

    2017-12-01

    Temporal and spatio-temporal stability analyses are carried out to characterize the occurrence of convective and absolute instabilities in combined Couette-Poiseuille flow of a Newtonian fluid past a deformable, neo-Hookean solid layer in the creeping-flow limit. Plane Couette flow of a Newtonian fluid past a neo-Hookean solid becomes temporally unstable in the inertia-less limit when the parameter Γ = V η/(GR) exceeds a critical value. Here, V is the velocity of the top plate, η is the fluid viscosity, G is the shear modulus of the solid layer, and R is the fluid layer thickness. The Kupfer-Bers method is employed to demarcate regions of absolute and convective instabilities in the Γ-H parameter space, where H is the ratio of solid to fluid thickness in the system. For certain ranges of the thickness ratio H, we find that the flow could be absolutely unstable, and the critical Γ required for absolute instability is very close to that for temporal instability, thus making the flow absolutely unstable at the onset of temporal instability. In some cases, there is a gap in the parameter Γ between the temporal and absolute instability boundaries. The present study thus shows that absolute instabilities are possible, even at very low Reynolds numbers in flow past deformable solid surfaces. The presence of absolute instabilities could potentially be exploited in the enhancement of mixing at low Reynolds numbers in flow through channels with deformable solid walls.

  19. Velocity Gradients in the Intracluster Gas of the Perseus Cluster

    NASA Astrophysics Data System (ADS)

    Dupke, Renato A.; Bregman, Joel N.

    2001-02-01

    We report the results of spatially resolved X-ray spectroscopy of eight different ASCA pointings distributed symmetrically around the center of the Perseus Cluster. The outer region of the intracluster gas is roughly isothermal, with temperature ~6-7 keV and metal abundance ~0.3 solar. Spectral analysis of the central pointing is consistent with the presence of a cooling flow and a central metal abundance gradient. A significant velocity gradient is found along an axis at a position angle of ~135°, which is ~45° discrepant with the major axis of the X-ray elongation. The radial velocity difference is found to be greater than 1000 km s-1 Mpc-1 at the 90% confidence level. Simultaneous fittings of GIS 2 and 3 indicate that the velocity gradient is significant at the 95% confidence level, and the F-test rules out constant velocities at the 99% level. Intrinsic short- and long-term variations of gain are unlikely (P<0.03) to explain the velocity discrepancies.

  20. The Sedov Blast Wave as a Radial Piston Verification Test

    DOE PAGES

    Pederson, Clark; Brown, Bart; Morgan, Nathaniel

    2016-06-22

    The Sedov blast wave is of great utility as a verification problem for hydrodynamic methods. The typical implementation uses an energized cell of finite dimensions to represent the energy point source. We avoid this approximation by directly finding the effects of the energy source as a boundary condition (BC). Furthermore, the proposed method transforms the Sedov problem into an outward moving radial piston problem with a time-varying velocity. A portion of the mesh adjacent to the origin is removed and the boundaries of this hole are forced with the velocities from the Sedov solution. This verification test is implemented onmore » two types of meshes, and convergence is shown. Our results from the typical initial condition (IC) method and the new BC method are compared.« less

  1. Modeling anomalous radial transport in kinetic transport codes

    NASA Astrophysics Data System (ADS)

    Bodi, K.; Krasheninnikov, S. I.; Cohen, R. H.; Rognlien, T. D.

    2009-11-01

    Anomalous transport is typically the dominant component of the radial transport in magnetically confined plasmas, where the physical origin of this transport is believed to be plasma turbulence. A model is presented for anomalous transport that can be used in continuum kinetic edge codes like TEMPEST, NEO and the next-generation code being developed by the Edge Simulation Laboratory. The model can also be adapted to particle-based codes. It is demonstrated that the model with a velocity-dependent diffusion and convection terms can match a diagonal gradient-driven transport matrix as found in contemporary fluid codes, but can also include off-diagonal effects. The anomalous transport model is also combined with particle drifts and a particle/energy-conserving Krook collision operator to study possible synergistic effects with neoclassical transport. For the latter study, a velocity-independent anomalous diffusion coefficient is used to mimic the effect of long-wavelength ExB turbulence.

  2. Production, Outflow Velocity, and Radial Distribution of H2O and OH in the Coma of Comet C/1995 O1 [Hale-Bopp] from Wide Field Imaging of OH

    NASA Technical Reports Server (NTRS)

    Harris, Walter M.; Scherb, Frank; Mierkiewicz, Edwin; Oliverson, Ronald; Morgenthaler, Jeffrey

    2003-01-01

    Observations of OH are a useful proxy of the water production rate (Q(sub H2O)) and outflow velocity (V(sub out)) in comets. From wide field images taken on 03/28/1997 and 04/08/1997 that capture the entire scale length of the OH coma of comet C/1995 O1 (Hale-Bopp), we obtain Q(sub H2O) from the model-independent method of aperture summation. With an adaptive ring summation algorithm, we extract the radial brightness distribution of OH 0-0 band emission out to cometocentric distances of up to 10(exp 6) km, both as azimuthal averages and in quadrants covering different position angles relative to the comet-Sun line. These profiles are fit using both fixed and variable velocity 2-component spherical expansion models to estimate V(sub OH) with increasing distance from the nucleus. The OH coma of Hale-Bopp was more spatially extended than previous comets, and this extension is best matched by a variable acceleration of H2O and OH that acted across the entire coma, but was strongest within 1-2 x 10(exp 4) km from the nucleus. Our models indicate that V(sub OH) at the edge of our detectable field of view (10(exp 6) km) was approx. 2-3 times greater in Hale-Bopp than for a 1P/Halley-class comet at 1 AU, which is consistent with the results of more sophisticated gas-kinetic models, extrapolation from previous observations of OH in comets with Q(sub H2O) greater than 10(exp 29)/s , and direct radio measurements of the outer coma Hale-Bopp OH velocity. The most probable source of this acceleration is thermalization of the excess energy of dissociation of H2O and OH over an extended collisional coma. When the coma is broken down by quadrants in position angle, we find an azimuthal asymmetry in the radial distribution that is characterized by an increase in the spatial extent of OH in the region between the orbit-trailing and anti-sunward directions. Model fits specific to this area and comparison with radio OH measurements suggest greater acceleration here, with V(sub OH

  3. Rayleigh Scattering Diagnostic for Measurement of Velocity and Density Fluctuation Spectra

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Panda, Jayanta; Elam, Kristie A.

    2002-01-01

    A new molecular Rayleigh scattering based flow diagnostic is used for the first time to measure the power spectrum of gas density and radial velocity component in the plumes of high speed jets. The technique is based on analyzing the Rayleigh scattered light with a Fabry-Perot interferometer used in the static, imaging mode. The PC based data acquisition system is capable of simultaneous sampling of velocity and density at rates to 100 kHz and data record lengths to 10 million. Velocity and density power spectra and velocity-density cross spectra are presented for a subsonic jet, an underexpanded screeching jet, and for Mach 1.4 and Mach 1.8 supersonic jets. Software and hardware interfaces were developed to allow computer control of all aspects of the experiment and data acquisition.

  4. The CARMENES search for exoplanets around M dwarfs. Radial-velocity variations of active stars in visual-channel spectra

    NASA Astrophysics Data System (ADS)

    Tal-Or, L.; Zechmeister, M.; Reiners, A.; Jeffers, S. V.; Schöfer, P.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Caballero, J. A.; Aceituno, J.; Bauer, F. F.; Béjar, V. J. S.; Czesla, S.; Dreizler, S.; Fuhrmeister, B.; Hatzes, A. P.; Johnson, E. N.; Kürster, M.; Lafarga, M.; Montes, D.; Morales, J. C.; Reffert, S.; Sadegi, S.; Seifert, W.; Shulyak, D.

    2018-06-01

    Context. Previous simulations predicted the activity-induced radial-velocity (RV) variations of M dwarfs to range from 1 cm s-1 to 1 km s-1, depending on various stellar and activity parameters. Aims: We investigate the observed relations between RVs, stellar activity, and stellar parameters of M dwarfs by analyzing CARMENES high-resolution visual-channel spectra (0.5-1μm), which were taken within the CARMENES RV planet survey during its first 20 months of operation. Methods: During this time, 287 of the CARMENES-sample stars were observed at least five times. From each spectrum we derived a relative RV and a measure of chromospheric Hα emission. In addition, we estimated the chromatic index (CRX) of each spectrum, which is a measure of the RV wavelength dependence. Results: Despite having a median number of only 11 measurements per star, we show that the RV variations of the stars with RV scatter of >10 m s-1 and a projected rotation velocity v sin i > 2 km s-1 are caused mainly by activity. We name these stars "active RV-loud stars" and find their occurrence to increase with spectral type: from 3% for early-type M dwarfs (M0.0-2.5 V) through 30% for mid-type M dwarfs (M3.0-5.5 V) to >50% for late-type M dwarfs (M6.0-9.0 V). Their RV-scatter amplitude is found to be correlated mainly with v sin i. For about half of the stars, we also find a linear RV-CRX anticorrelation, which indicates that their activity-induced RV scatter is lower at longer wavelengths. For most of them we can exclude a linear correlation between RV and Hα emission. Conclusions: Our results are in agreement with simulated activity-induced RV variations in M dwarfs. The RV variations of most active RV-loud M dwarfs are likely to be caused by dark spots on their surfaces, which move in and out of view as the stars rotate. The data presented in Figs. 5 and A.1 are only available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http

  5. Core radial electric field and transport in Wendelstein 7-X plasmas

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

    Pablant, N. A.; Langenberg, A.; Alonso, A.

    The results from the investigation of neoclassical core transport and the role of the radial electric field profile (E r) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the E r profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u ⊥) through the force balance equation. This allows the radial electric fieldmore » to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu ⊥~ 5 km/s (ΔE r ~12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred E r profiles are compared to initial neoclassical calculations based on measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. Finally, these comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.« less

  6. Core radial electric field and transport in Wendelstein 7-X plasmas

    NASA Astrophysics Data System (ADS)

    Pablant, N. A.; Langenberg, A.; Alonso, A.; Beidler, C. D.; Bitter, M.; Bozhenkov, S.; Burhenn, R.; Beurskens, M.; Delgado-Aparicio, L.; Dinklage, A.; Fuchert, G.; Gates, D.; Geiger, J.; Hill, K. W.; Höfel, U.; Hirsch, M.; Knauer, J.; Krämer-Flecken, A.; Landreman, M.; Lazerson, S.; Maaßberg, H.; Marchuk, O.; Massidda, S.; Neilson, G. H.; Pasch, E.; Satake, S.; Svennson, J.; Traverso, P.; Turkin, Y.; Valson, P.; Velasco, J. L.; Weir, G.; Windisch, T.; Wolf, R. C.; Yokoyama, M.; Zhang, D.; W7-X Team

    2018-02-01

    The results from the investigation of neoclassical core transport and the role of the radial electric field profile (Er) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the Er profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u⊥) through the force balance equation. This allows the radial electric field to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu⊥˜ 5 km/s (ΔEr ˜ 12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred Er profiles are compared to initial neoclassical calculations based on measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. These comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.

  7. Biomechanical models for radial distance determination by the rat vibrissal system.

    PubMed

    Birdwell, J Alexander; Solomon, Joseph H; Thajchayapong, Montakan; Taylor, Michael A; Cheely, Matthew; Towal, R Blythe; Conradt, Jorg; Hartmann, Mitra J Z

    2007-10-01

    Rats use active, rhythmic movements of their whiskers to acquire tactile information about three-dimensional object features. There are no receptors along the length of the whisker; therefore all tactile information must be mechanically transduced back to receptors at the whisker base. This raises the question: how might the rat determine the radial contact position of an object along the whisker? We developed two complementary biomechanical models that show that the rat could determine radial object distance by monitoring the rate of change of moment (or equivalently, the rate of change of curvature) at the whisker base. The first model is used to explore the effects of taper and inherent whisker curvature on whisker deformation and used to predict the shapes of real rat whiskers during deflections at different radial distances. Predicted shapes closely matched experimental measurements. The second model describes the relationship between radial object distance and the rate of change of moment at the base of a tapered, inherently curved whisker. Together, these models can account for recent recordings showing that some trigeminal ganglion (Vg) neurons encode closer radial distances with increased firing rates. The models also suggest that four and only four physical variables at the whisker base -- angular position, angular velocity, moment, and rate of change of moment -- are needed to describe the dynamic state of a whisker. We interpret these results in the context of our evolving hypothesis that neural responses in Vg can be represented using a state-encoding scheme that includes combinations of these four variables.

  8. Core radial electric field and transport in Wendelstein 7-X plasmas

    DOE PAGES

    Pablant, N. A.; Langenberg, A.; Alonso, A.; ...

    2018-02-12

    The results from the investigation of neoclassical core transport and the role of the radial electric field profile (E r) in the first operational phase of the Wendelstein 7-X (W7-X) stellarator are presented. In stellarator plasmas, the details of the E r profile are expected to have a strong effect on both the particle and heat fluxes. Investigation of the radial electric field is important in understanding neoclassical transport and in validation of neoclassical calculations. The radial electric field is closely related to the perpendicular plasma flow (u ⊥) through the force balance equation. This allows the radial electric fieldmore » to be inferred from measurements of the perpendicular flow velocity, which can be measured using the x-ray imaging crystal spectrometer and correlation reflectometry diagnostics. Large changes in the perpendicular rotation, on the order of Δu ⊥~ 5 km/s (ΔE r ~12 kV/m), have been observed within a set of experiments where the heating power was stepped down from 2 MW to 0.6 MW. These experiments are examined in detail to explore the relationship between heating power temperature, and density profiles and the radial electric field. Finally, the inferred E r profiles are compared to initial neoclassical calculations based on measured plasma profiles. The results from several neoclassical codes, sfincs, fortec-3d, and dkes, are compared both with each other and the measurements. Finally, these comparisons show good agreement, giving confidence in the applicability of the neoclassical calculations to the W7-X configuration.« less

  9. True-triaxial experimental seismic velocities linked to an in situ 3D seismic velocity structure

    NASA Astrophysics Data System (ADS)

    Tibbo, M.; Young, R. P.

    2017-12-01

    Upscaling from laboratory seismic velocities to in situ field seismic velocities is a fundamental problem in rock physics. This study presents a unique situation where a 3D velocity structure of comparable frequency ranges is available both in situ and experimentally. The in situ data comes from the Underground Research Laboratory (URL) located in Manitoba, Canada. The velocity survey and oriented, cubic rock sample, are from the 420m level of the mine, where the geology is a homogeneous and isotropic granite. The triaxial in situ stress field at this level was determined and the Mine-by tunnel was excavated horizontally to maximize borehole break out. Ultrasonic velocity measurements for P-, S1-,and S2-waves were done in the tunnel sidewall, ceiling and far-field rock mass.The geophysical imaging cell (GIC) used in this study allows for true triaxial stress (σ1 > σ2 > σ3). Velocity surveys for P-, S1-, and S2-wave can be acquired along all three axes, and therefore the effects of σ1, σ2, σ3 on the velocity-stress relationship is obtained along all 3 axes. The cubic (80 mm) granite sample was prepared oriented to the in situ principle stress axis in the field. The stress path of the sample extraction from in situ stress was modeled in FLAC 3D (by Itasca inc ), and then reapplied in the GIC to obtain the laboratory velocities at in situ stress. Both laboratory and field velocities conclude the same maximum velocity axis, within error, to be along σ2 at 5880±60 m/s for P-wave. This deviation from the expected fast axis being σ1, is believed to be caused by an aligned microcrack fabric. The theory of acoustoelasticity, the dependence of acoustic wave velocity on stresses in the propagating isotropic medium, is applied to the borehole hoop and radial stresses produced by the Mine-by tunnel. The acoustoelastic effect involves determining the linear (second-order) and nonlinear (third-order) elastic constants, which are derived from the velocity-stress slopes

  10. The Milky Way's Circular Velocity Curve and Its Constraint on the Galactic Mass with RR Lyrae Stars

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

    Ablimit, Iminhaji; Zhao, Gang, E-mail: iminhaji@nao.cas.cn, E-mail: gzhao@nao.cas.cn

    We present a sample of 1148 ab-type RR Lyrae (RRLab) variables identified from Catalina Surveys Data Release 1, combined with SDSS DR8 and LAMOST DR4 spectral data. We first use a large sample of 860 Galactic halo RRLab stars and derive the circular velocity distributions for the stellar halo. With the precise distances and carefully determined radial velocities (the center-of-mass radial velocities) and by considering the pulsation of the RRLab stars in our sample, we can obtain a reliable and comparable stellar halo circular velocity curve. We follow two different prescriptions for the velocity anisotropy parameter β in the Jeansmore » equation to study the circular velocity curve and mass profile. Additionally, we test two different solar peculiar motions in our calculation. The best result we obtained with the adopted solar peculiar motion 1 of ( U , V , W ) = (11.1, 12, 7.2) km s{sup −1} is that the enclosed mass of the Milky Way within 50 kpc is (3.75 ± 1.33) × 10{sup 11} M {sub ⊙} based on β = 0 and the circular velocity 180 ± 31.92 (km s{sup −1}) at 50 kpc. This result is consistent with dynamical model results, and it is also comparable to the results of previous similar works.« less

  11. Quasi-radial wall jets as a new concept in boundary layer flow control

    NASA Astrophysics Data System (ADS)

    Javadi, Khodayar; Hajipour, Majid

    2018-01-01

    This work aims to introduce a novel concept of wall jets wherein the flow is radially injected into a medium through a sector of a cylinder, called quasi-radial (QR) wall jets. The results revealed that fluid dynamics of the QR wall jet flow differs from that of conventional wall jets. Indeed, lateral and normal propagations of a conventional three-dimensional wall jet are via shear stresses. While, lateral propagation of a QR wall jet is due to mean lateral component of the velocity field. Moreover, discharged Arrays of conventional three-dimensional wall jets in quiescent air lead to formation of a combined wall jet at large distant from the nozzles, while QR wall jet immediately spread in lateral direction, meet each other and merge together very quickly in a short distance downstream of the jet nozzles. Furthermore, in discharging the conventional jets into an external flow, there is no strong interaction between them as they are moving parallel. While, in QR wall jets the lateral components of the velocity field strongly interact with boundary layer of the external flow and create strong helical vortices acting as vortex generators.

  12. Misconceptions in recent papers on special relativity and absolute space theories

    NASA Technical Reports Server (NTRS)

    Torr, D. G.; Kolen, P.

    1982-01-01

    Several recent papers which purport to substantiate or negate arguments in favor of certain theories of absolute space have been based on fallacious principles. This paper discusses three related instances, indicating where misconceptions have arisen. It is established, contrary to popular belief, that the classical Lorentz ether theory accounts for all the experimental evidence which supports the special theory of relativity. It is demonstrated that the ether theory predicts the null results obtained from pulsar timing and Moessbauer experiments. It is concluded that a measurement of the one-way velocity of light has physical meaning within the context of the Lorentz theory, and it is argued that an adequately designed experiment to measure the one-way velocity of light should be attempted.

  13. Breakdown of Burton Prim Slichter approach and lateral solute segregation in radially converging flows

    NASA Astrophysics Data System (ADS)

    Priede, J.; Gerbeth, G.

    2005-11-01

    A theoretical study is presented of the effect of a radially converging melt flow, which is directed away from the solidification front, on the radial solute segregation in simple solidification models. We show that the classical Burton-Prim-Slichter (BPS) solution describing the effect of a diverging flow on the solute incorporation into the solidifying material breaks down for the flows converging along the solidification front. The breakdown is caused by a divergence of the integral defining the effective boundary layer thickness which is the basic concept of the BPS theory. Although such a divergence can formally be avoided by restricting the axial extension of the melt to a layer of finite height, radially uniform solute distributions are possible only for weak melt flows with an axial velocity away from the solidification front comparable to the growth rate. There is a critical melt velocity for each growth rate at which the solution passes through a singularity and becomes physically inconsistent for stronger melt flows. To resolve these inconsistencies we consider a solidification front presented by a disk of finite radius R0 subject to a strong converging melt flow and obtain an analytic solution showing that the radial solute concentration depends on the radius r as ˜ln(R0/r) and ˜ln(R0/r) close to the rim and at large distances from it. The logarithmic increase of concentration is limited in the vicinity of the symmetry axis by the diffusion becoming effective at a distance comparable to the characteristic thickness of the solute boundary layer. The converging flow causes a solute pile-up forming a logarithmic concentration peak at the symmetry axis which might be an undesirable feature for crystal growth processes.

  14. Velocity-induced collapses of stable neutron stars

    NASA Astrophysics Data System (ADS)

    Novak, J.

    2001-09-01

    The collapse of spherical neutron stars is studied in General Relativity. The initial state is a stable neutron star to which an inward radial kinetic energy has been added through some velocity profile. For two different equations of state and two different shapes of velocity profiles, it is found that neutron stars can collapse to black holes for high enough inward velocities, provided that their masses are higher than some minimal value, depending on the equation of state. For a polytropic equation of state of the form p=Krho gamma, with gamma = 2 it is found to be 1.16 ( (K)/(0.1) right )0.5 Msun, whereas for a more realistic one (described in Pons et al. \\cite{PonREPL00}), it is 0.36 Msun . In some cases of collapse forming a black hole, part of the matter composing the initial neutron star can be ejected through a shock, leaving only a fraction of the initial mass to form a black hole. Therefore, black holes of very small masses can be formed and, in particular, the mass scaling relation, as a function of initial velocity, takes the form discovered by Choptuik (\\cite{Cho93}) for critical collapses.

  15. CO emission tracing a warp or radial flow within ≲100 au in the HD 100546 protoplanetary disk

    NASA Astrophysics Data System (ADS)

    Walsh, Catherine; Daley, Cail; Facchini, Stefano; Juhász, Attila

    2017-11-01

    We present spatially resolved Atacama Large Millimeter/submillimeter Array (ALMA) images of 12CO J = 3-2 emission from the protoplanetary disk around the Herbig Ae star, HD 100546. We expand upon earlier analyses of this data and model the spatially-resolved kinematic structure of the CO emission. Assuming a velocity profile which prescribes a flat or flared emitting surface in Keplerian rotation, we uncover significant residuals with a peak of ≈7δv, where δv = 0.21 km s-1 is the width of a single spectral resolution element. The shape and extent of the residuals reveal the possible presence of a severely warped and twisted inner disk extending to at most 100 au. Adapting the model to include a misaligned inner gas disk with (I) an inclination almost edge-on to the line of sight, and (II) a position angle almost orthogonal to that of the outer disk reduces the residuals to <3δv. However, these findings are contrasted by recent VLT/SPHERE, MagAO/GPI, and VLTI/PIONIER observations of HD 100546 that show no evidence of a severely misaligned inner dust disk down to spatial scales of 1 au. An alternative explanation for the observed kinematics are fast radial flows mediated by (proto)planets. Inclusion of a radial velocity component at close to free-fall speeds and inwards of ≈50 au results in residuals of ≈4δv. Hence, the model including a radial velocity component only does not reproduce the data as well as that including a twisted and misaligned inner gas disk. Molecular emission data at a higher spatial resolution (of order 10 au) are required to further constrain the kinematics within ≲100 au. HD 100546 joins several other protoplanetary disks for which high spectral resolution molecular emission shows that the gas velocity structure cannot be described by a purely Keplerian velocity profile with a universal inclination and position angle. Regardless of the process, the most likely cause is the presence of an unseen planetary companion.

  16. Three dimensional LDV flow measurements and theoretical investigation in a radial inflow turbine scroll

    NASA Technical Reports Server (NTRS)

    Malak, Malak Fouad; Hamed, Awatef; Tabakoff, Widen

    1990-01-01

    A two-color LDV system was used in the measurement of three orthogonal velocity components at 758 points located throughout the scroll and the unvaned portion of the nozzle of a radial inflow turbine scroll. The cold flow experimental results are presented for the velocity field at the scroll tongue. In addition, a total pressure loss of 3.5 percent for the scroll is revealed from the velocity measurements combined with the static pressure readings. Moreover, the measurement of the three normal stresses of the turbulence has showed that the flow is anisotropic. Furthermore, the mean velocity components are compared with a numerical solution of the potential flow field using the finite element technique. The theoretical prediction of the exit flow angle variation agrees well with the experimental results. This variation leads to a higher scroll pattern factor which can be avoided by controlling the scroll cross sectional area distribution.

  17. OFF-DESIGN PERFORMANCE OF RADIAL INFLOW TURBINES

    NASA Technical Reports Server (NTRS)

    Wasserbauer, C. A.

    1994-01-01

    This program calculates off design performance of radial inflow turbines. The program uses a one dimensional solution of flow conditions through the turbine along the main streamline. The loss model accounts for stator, rotor, incidence, and exit losses. Program features include consideration of stator and rotor trailing edge blockage and computation of performance to limiting load. Stator loss (loss in kinetic energy across the stator) is proportional to the average kinetic energy in the blade row and is represented in the program by an equation which includes a stator loss coefficient determined from design point performance and then assumed to be constant for the off design calculations. Minimum incidence loss does not occur at zero incidence angle with respect to the rotor blade, but at some optimum flow angle. At high pressure ratios the level of rotor inlet velocity seemed to have an excessive influence on the loss. Using the component of velocity in the direction of the optimum flow angle gave better correlations with experimental results. Overall turbine geometry and design point values of efficiency, pressure ratio, and mass flow are needed as input information. The output includes performance and velocity diagram parameters for any number of given speeds over a range of turbine pressure ratio. The program has been implemented on the IBM 7094 and operates in batch mode.

  18. Vection: the contributions of absolute and relative visual motion.

    PubMed

    Howard, I P; Howard, A

    1994-01-01

    Inspection of a visual scene rotating about the vertical body axis induces a compelling sense of self rotation, or circular vection. Circular vection is suppressed by stationary objects seen beyond the moving display but not by stationary objects in the foreground. We hypothesised that stationary objects in the foreground facilitate vection because they introduce a relative-motion signal into what would otherwise be an absolute-motion signal. Vection latency and magnitude were measured with a full-field moving display and with stationary objects of various sizes and at various positions in the visual field. The results confirmed the hypothesis. Vection latency was longer when there were no stationary objects in view than when stationary objects were in view. The effect of stationary objects was particularly evident at low stimulus velocities. At low velocities a small stationary point significantly increased vection magnitude in spite of the fact that, at higher stimulus velocities and with other stationary objects in view, fixation on a stationary point, if anything, reduced vection. Changing the position of the stationary objects in the field of view did not affect vection latencies or magnitudes.

  19. Synthetic Seismogram Calculations for Two-Dimensional Velocity Models.

    DTIC Science & Technology

    1983-05-20

    vertical and radial component displacements. The seismograms have been convolved with a seismograph response function corresponding to a short period...phase velocity is a measure of the degree of numerical dispersion present in the calculation for a variety of grid spacings. The value of 1/G of 0.1...method is an approximate technique and is some what restricted in its application, its efficiency and accuracy make it suitable for routine modeling of

  20. A simulation study of radial expansion of an electron beam injected into an ionospheric plasma

    NASA Technical Reports Server (NTRS)

    Koga, J.; Lin, C. S.

    1994-01-01

    Injections of nonrelativistic electron beams from a finite equipotential conductor into an ionospheric plasma have been simulated using a two-dimensional electrostatic particle code. The purpose of the study is to survey the simulation parameters for understanding the dependence of beam radius on physical variables. The conductor is charged to a high potential when the background plasma density is less than the beam density. Beam electrons attracted by the charged conductor are decelerated to zero velocity near the stagnation point, which is at a few Debye lengths from the conductor. The simulations suggest that the beam electrons at the stagnation point receive a large transverse kick and the beam expands radially thereafter. The buildup of beam electrons at the stagnation point produces a large electrostatic force responsible for the transverse kick. However, for the weak charging cases where the background plasma density is larger than the beam density, the radial expansion mechanism is different; the beam plasma instability is found to be responsible for the radial expansion. The simulations show that the electron beam radius for high spacecraft charging cases is of the order of the beam gyroradius, defined as the beam velocity divided by the gyrofrequency. In the weak charging cases, the beam radius is only a fraction of the beam gyroradius. The parameter survey indicates that the beam radius increases with beam density and decreases with magnetic field and beam velocity. The beam radius normalized by the beam gyroradius is found to scale according to the ratio of the beam electron Debye length to the ambient electron Debye length. The parameter dependence deduced would be useful for interpreting the beam radius and beam density of electron beam injection experiments conducted from rockets and the space shuttle.

  1. Copernicus observations of Iota Herculis velocity variations

    NASA Technical Reports Server (NTRS)

    Rogerson, J. B., Jr.

    1984-01-01

    Observations of Iota Her at 109.61-109.67 nm obtained with the U1 channel of the Copernicus spectrophotometer at resolution 5 pm during 3.6 days in May, 1979, are reported. Radial-velocity variations are detected and analyzed as the sum of two sinusoids with frequencies 0.660 and 0.618 cycles/day and amplitudes 9.18 and 8.11 km/s, respectively. Weak evidence supporting the 13.9-h periodicity seen in line-profile variations by Smith (1978) is found.

  2. Image stitching and image reconstruction of intestines captured using radial imaging capsule endoscope

    NASA Astrophysics Data System (ADS)

    Ou-Yang, Mang; Jeng, Wei-De; Wu, Yin-Yi; Dung, Lan-Rong; Wu, Hsien-Ming; Weng, Ping-Kuo; Huang, Ker-Jer; Chiu, Luan-Jiau

    2012-05-01

    This study investigates image processing using the radial imaging capsule endoscope (RICE) system. First, an experimental environment is established in which a simulated object has a shape that is similar to a cylinder, such that a triaxial platform can be used to push the RICE into the sample and capture radial images. Then four algorithms (mean absolute error, mean square error, Pearson correlation coefficient, and deformation processing) are used to stitch the images together. The Pearson correlation coefficient method is the most effective algorithm because it yields the highest peak signal-to-noise ratio, higher than 80.69 compared to the original image. Furthermore, a living animal experiment is carried out. Finally, the Pearson correlation coefficient method and vector deformation processing are used to stitch the images that were captured in the living animal experiment. This method is very attractive because unlike the other methods, in which two lenses are required to reconstruct the geometrical image, RICE uses only one lens and one mirror.

  3. The effect of the charge exchange source on the velocity and 'temperature' distributions and their anisotropies in the earth's exosphere

    NASA Technical Reports Server (NTRS)

    Hodges, R. R., Jr.; Rohrbaugh, R. P.; Tinsley, B. A.

    1981-01-01

    The velocity distribution of atomic hydrogen in the earth's exosphere is calculated as a function of altitude and direction taking into account both the classic exobase source and the higher-altitude plasmaspheric charge exchange source. Calculations are performed on the basis of a Monte Carlo technique in which random ballistic trajectories of individual atoms are traced through a three-dimensional grid of audit zones, at which relative concentrations and momentum or energy fluxes are obtained. In the case of the classical exobase source alone, the slope of the velocity distribution is constant only for the upward radial velocity component and increases dramatically with altitude for the incoming radial and transverse velocity components, resulting in a temperature decrease. The charge exchange source, which produces the satellite hydrogen component and the hot ballistic and escape components of the exosphere, is found to enhance the wings of the velocity distributions, however this effect is not sufficient to overcome the temperature decreases at altitudes above one earth radius. The resulting global model of the hydrogen exosphere may be used as a realistic basis for radiative transfer calculations.

  4. Teaching Absolute Value Meaningfully

    ERIC Educational Resources Information Center

    Wade, Angela

    2012-01-01

    What is the meaning of absolute value? And why do teachers teach students how to solve absolute value equations? Absolute value is a concept introduced in first-year algebra and then reinforced in later courses. Various authors have suggested instructional methods for teaching absolute value to high school students (Wei 2005; Stallings-Roberts…

  5. The CARMENES search for exoplanets around M dwarfs . First visual-channel radial-velocity measurements and orbital parameter updates of seven M-dwarf planetary systems

    NASA Astrophysics Data System (ADS)

    Trifonov, T.; Kürster, M.; Zechmeister, M.; Tal-Or, L.; Caballero, J. A.; Quirrenbach, A.; Amado, P. J.; Ribas, I.; Reiners, A.; Reffert, S.; Dreizler, S.; Hatzes, A. P.; Kaminski, A.; Launhardt, R.; Henning, Th.; Montes, D.; Béjar, V. J. S.; Mundt, R.; Pavlov, A.; Schmitt, J. H. M. M.; Seifert, W.; Morales, J. C.; Nowak, G.; Jeffers, S. V.; Rodríguez-López, C.; del Burgo, C.; Anglada-Escudé, G.; López-Santiago, J.; Mathar, R. J.; Ammler-von Eiff, M.; Guenther, E. W.; Barrado, D.; González Hernández, J. I.; Mancini, L.; Stürmer, J.; Abril, M.; Aceituno, J.; Alonso-Floriano, F. J.; Antona, R.; Anwand-Heerwart, H.; Arroyo-Torres, B.; Azzaro, M.; Baroch, D.; Bauer, F. F.; Becerril, S.; Benítez, D.; Berdiñas, Z. M.; Bergond, G.; Blümcke, M.; Brinkmöller, M.; Cano, J.; Cárdenas Vázquez, M. C.; Casal, E.; Cifuentes, C.; Claret, A.; Colomé, J.; Cortés-Contreras, M.; Czesla, S.; Díez-Alonso, E.; Feiz, C.; Fernández, M.; Ferro, I. M.; Fuhrmeister, B.; Galadí-Enríquez, D.; Garcia-Piquer, A.; García Vargas, M. L.; Gesa, L.; Gómez Galera, V.; González-Peinado, R.; Grözinger, U.; Grohnert, S.; Guàrdia, J.; Guijarro, A.; de Guindos, E.; Gutiérrez-Soto, J.; Hagen, H.-J.; Hauschildt, P. H.; Hedrosa, R. P.; Helmling, J.; Hermelo, I.; Hernández Arabí, R.; Hernández Castaño, L.; Hernández Hernando, F.; Herrero, E.; Huber, A.; Huke, P.; Johnson, E.; de Juan, E.; Kim, M.; Klein, R.; Klüter, J.; Klutsch, A.; Lafarga, M.; Lampón, M.; Lara, L. M.; Laun, W.; Lemke, U.; Lenzen, R.; López del Fresno, M.; López-González, M. J.; López-Puertas, M.; López Salas, J. F.; Luque, R.; Magán Madinabeitia, H.; Mall, U.; Mandel, H.; Marfil, E.; Marín Molina, J. A.; Maroto Fernández, D.; Martín, E. L.; Martín-Ruiz, S.; Marvin, C. J.; Mirabet, E.; Moya, A.; Moreno-Raya, M. E.; Nagel, E.; Naranjo, V.; Nortmann, L.; Ofir, A.; Oreiro, R.; Pallé, E.; Panduro, J.; Pascual, J.; Passegger, V. M.; Pedraz, S.; Pérez-Calpena, A.; Pérez Medialdea, D.; Perger, M.; Perryman, M. A. C.; Pluto, M.; Rabaza, O.; Ramón, A.; Rebolo, R.; Redondo, P.; Reinhardt, S.; Rhode, P.; Rix, H.-W.; Rodler, F.; Rodríguez, E.; Rodríguez Trinidad, A.; Rohloff, R.-R.; Rosich, A.; Sadegi, S.; Sánchez-Blanco, E.; Sánchez Carrasco, M. A.; Sánchez-López, A.; Sanz-Forcada, J.; Sarkis, P.; Sarmiento, L. F.; Schäfer, S.; Schiller, J.; Schöfer, P.; Schweitzer, A.; Solano, E.; Stahl, O.; Strachan, J. B. P.; Suárez, J. C.; Tabernero, H. M.; Tala, M.; Tulloch, S. M.; Veredas, G.; Vico Linares, J. I.; Vilardell, F.; Wagner, K.; Winkler, J.; Wolthoff, V.; Xu, W.; Yan, F.; Zapatero Osorio, M. R.

    2018-02-01

    Context. The main goal of the CARMENES survey is to find Earth-mass planets around nearby M-dwarf stars. Seven M dwarfs included in the CARMENES sample had been observed before with HIRES and HARPS and either were reported to have one short period planetary companion (GJ 15 A, GJ 176, GJ 436, GJ 536 and GJ 1148) or are multiple planetary systems (GJ 581 and GJ 876). Aims: We aim to report new precise optical radial velocity measurements for these planet hosts and test the overall capabilities of CARMENES. Methods: We combined our CARMENES precise Doppler measurements with those available from HIRES and HARPS and derived new orbital parameters for the systems. Bona-fide single planet systems were fitted with a Keplerian model. The multiple planet systems were analyzed using a self-consistent dynamical model and their best fit orbits were tested for long-term stability. Results: We confirm or provide supportive arguments for planets around all the investigated stars except for GJ 15 A, for which we find that the post-discovery HIRES data and our CARMENES data do not show a signal at 11.4 days. Although we cannot confirm the super-Earth planet GJ 15 Ab, we show evidence for a possible long-period (Pc = 7030-630+970 d) Saturn-mass (mcsini = 51.8M⊕) planet around GJ 15 A. In addition, based on our CARMENES and HIRES data we discover a second planet around GJ 1148, for which we estimate a period Pc = 532.6 days, eccentricity ec = 0.342 and minimum mass mcsini = 68.1M⊕. Conclusions: The CARMENES optical radial velocities have similar precision and overall scatter when compared to the Doppler measurements conducted with HARPS and HIRES. We conclude that CARMENES is an instrument that is up to the challenge of discovering rocky planets around low-mass stars. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programmes 072.C-0488, 072.C-0513, 074.C-0012, 074.C-0364, 075.D-0614, 076.C-0878, 077.C

  6. Measurement of Correlation Between Flow Density, Velocity, and Density*velocity(sup 2) with Far Field Noise in High Speed Jets

    NASA Technical Reports Server (NTRS)

    Panda, Jayanta; Seasholtz, Richard G.; Elam, Kristie A.

    2002-01-01

    To locate noise sources in high-speed jets, the sound pressure fluctuations p', measured at far field locations, were correlated with each of radial velocity v, density rho, and phov(exp 2) fluctuations measured from various points in jet plumes. The experiments follow the cause-and-effect method of sound source identification, where correlation is related to the first, and correlation to the second source terms of Lighthill's equation. Three fully expanded, unheated plumes of Mach number 0.95, 1.4 and 1.8 were studied for this purpose. The velocity and density fluctuations were measured simultaneously using a recently developed, non-intrusive, point measurement technique based on molecular Rayleigh scattering. It was observed that along the jet centerline the density fluctuation spectra S(sub rho) have different shapes than the radial velocity spectra S(sub v), while data obtained from the peripheral shear layer show similarity between the two spectra. Density fluctuations in the jet showed significantly higher correlation, than either rhov(sub 2) or v fluctuations. It is found that a single point correlation from the peak sound emitting region at the end of the potential core can account for nearly 10% of all noise at 30 to the jet axis. The correlation, representing the effectiveness of a longitudinal quadrupole in generating noise 90 to the jet axis, is found to be zero within experimental uncertainty. In contrast rhov(exp 2) fluctuations were better correlated with sound pressure fluctuation at the 30 location. The strongest source of sound is found to lie at the centerline and beyond the end of potential core.

  7. The absolute magnitudes of RR Lyrae stars. II - DX Delphini

    NASA Astrophysics Data System (ADS)

    Skillen, I.; Fernley, J. A.; Jameson, R. F.; Lynas-Gray, A. E.; Longmore, A. J.

    1989-11-01

    UV, IR and visual photometry of the short-period RR Lyrae star DX Del is presented and treated by means of the Blackwell and Shallis (1977) IR Flux Method-based formulation of the Baade-Wesselink method. Upon correcting to common reddening, extinction, and radial-velocity conversion factors, as well as applying the Baade-Wesselink analysis of Burki and Meylan (1986), it proved impossible to reproduce their results. It is suggested that the present methods are inherently more stable than those of Burki and Meylan, given their reliance on optical colors and magnitudes to derive effective temperatures and radii.

  8. Variance associated with walking velocity during force platform gait analysis of a heterogeneous sample of clinically normal dogs.

    PubMed

    Piazza, Alexander M; Binversie, Emily E; Baker, Lauren A; Nemke, Brett; Sample, Susannah J; Muir, Peter

    2017-04-01

    OBJECTIVE To determine whether walking at specific ranges of absolute and relative (V*) velocity would aid efficient capture of gait trial data with low ground reaction force (GRF) variance in a heterogeneous sample of dogs. ANIMALS 17 clinically normal dogs of various breeds, ages, and sexes. PROCEDURES Each dog was walked across a force platform at its preferred velocity, with controlled acceleration within 0.5 m/s 2 . Ranges in V* were created for height at the highest point of the shoulders (withers; WHV*). Variance effects from 8 walking absolute velocity ranges and associated WHV* ranges were examined by means of repeated-measures ANCOVA. RESULTS The individual dog effect provided the greatest contribution to variance. Narrow velocity ranges typically resulted in capture of a smaller percentage of valid trials and were not consistently associated with lower variance. The WHV* range of 0.33 to 0.46 allowed capture of valid trials efficiently, with no significant effects on peak vertical force and vertical impulse. CONCLUSIONS AND CLINICAL RELEVANCE Dogs with severe lameness may be unable to trot or may have a decline in mobility with gait trial repetition. Gait analysis involving evaluation of individual dogs at their preferred absolute velocity, such that dogs are evaluated at a similar V*, may facilitate efficient capture of valid trials without significant effects on GRF. Use of individual velocity ranges derived from a WHV* range of 0.33 to 0.46 can account for heterogeneity and appears suitable for use in clinical trials involving dogs at a walking gait.

  9. Lateral variations in upper-mantle seismic anisotropy in the Pacific from inversion of a surface-wave dispersion dataset

    NASA Astrophysics Data System (ADS)

    Eddy, C. L.; Ekstrom, G.; Nettles, M.; Gaherty, J. B.

    2017-12-01

    We present a three-dimensional model of the anisotropic velocity structure of the Pacific lithosphere and asthenosphere. The presence of seismic anisotropy in the oceanic upper mantle provides information about the geometry of flow in the mantle, the nature of the lithosphere-asthenosphere boundary, and the possible presence of partial melt in the asthenosphere. Our dataset consists of fundamental-mode dispersion for Rayleigh and Love waves measured between 25-250 s with paths crossing the Pacific Ocean. We invert the phase anomaly measurements directly for three-dimensional anisotropic velocity structure. Our models are radially anisotropic and include the full set of elastic parameters that describe azimuthal variations in velocity (e.g. Gc, Gs). We investigate the age dependence of seismic velocity and radial anisotropy and find that there are significant deviations from the velocities predicted by a simple oceanic plate cooling model. We observe strong radial anisotropy with vsh > vsv in the asthenosphere of the central Pacific. We investigate the radial anisotropy in the shallow lithosphere, where previous models have reported conflicting results. There is a contrast in both upper-mantle isotropic velocities and radial anisotropy between the Pacific and Nazca plates, across the East Pacific Rise. We also investigate lateral variations in azimuthal anisotropy throughout the Pacific upper mantle and find that there are large areas over which the anisotropy fast axis does not align with absolute plate motion, suggesting the presence of small-scale convection or pressure-driven flow beneath the base of the oceanic plate.

  10. First absolute wind measurements in the middle atmosphere of Mars

    NASA Astrophysics Data System (ADS)

    Lellouch, Emmanuel; Goldstein, Jeffrey J.; Bougher, Stephen W.; Paubert, Gabriel; Rosenqvist, Jan

    1991-12-01

    The first absolute wind measurements in the middle atmosphere of Mars (40-70 km) were obtained from Doppler shifts in the J = 2-1 CO transition at 230.538 GHz. During the 1988 opposition, this line was observed at 100 kHz resolution with the IRAM 30 m telescope. The 12-arcsec FWHM beam of the facility allowed spatial resolution of the Martian disk (23.8 arcsec). The high S/N of the data allowed measurement of winds with a 1-sigma absolute line-of-sight accuracy of 20 m/s. The measurements, performed during southern summer solstice, stress the Southern Hemisphere and clearly indicate a global easterlies flow. If modeled by a broad easterly jet with a maximum centered at 20 S, and extending 80 deg in latitude, the jet core velocity is found to have a chi-sq minimum at 160 m/s, generally consistent with predictions for broad summer easterly jets near 50 km as proposed by theoretical models. If the flow is modeled instead by a planet-wide solid rotator zonal flow which is restricted to the Southern Hemisphere or equatorial regions, the velocity of the easterlies is nearly the same. These wind measurements, together with the temperature measurements of Deming et al. (1986), provide the first experimental rough picture of the middle atmosphere circulation of Mars, in general agreement with the Jaquin axisymmetric middle atmosphere model and the current Mars GCM model of Pollack et al. (1990).

  11. Simulation of radial solute segregation in vertical Bridgman growth of pyridine-doped benzene, a surrogate for binary organic nonlinear optical materials

    NASA Astrophysics Data System (ADS)

    Lee, Hanjie; Pearlstein, Arne J.

    2000-09-01

    We present steady axisymmetric computations of solute distributions and radial segregation for vertical Bridgman growth of pyridine-doped benzene, a binary aromatic system with anisotropic solid-phase thermal conductivity, that serves as a model of solute transport in crystal growth of organic nonlinear optical materials. The radial variation of solid-phase mass fraction ( Cs) of pyridine, which is rejected at the growing interface, depends strongly on growth conditions. High growth velocities tend to increase Cs near the centerline, the ampoule wall, or both, and low growth velocities give more nearly uniform radial distributions. The maximum ampoule-wall temperature gradient also affects radial segregation, with convex-to-the-liquid interfaces at small temperature gradients being associated with radially monotonic Cs distributions, and ridged interfaces at higher gradients being associated with nonmonotonic distributions having maxima at the centerline and ampoule wall. Nonuniformity is strongly determined by both interface shape and the nature of the flow near the interface. Solute is transported down to the interface by a large toroidal vortex, and swept radially inward to the centerline by a second, flattened toroidal cell. When the interface is depressed at its junction with the ampoule wall, rejected solute accumulates in the overlying liquid, where convection is relatively weak, resulting in local solute enrichment of the solid. Computations at normal and zero gravity show that for two very similar interface shapes, a maximum in the radial solid-phase solute distribution at the ampoule wall is associated with the interface shape, while the maximum on the centerline is associated with sweeping of solute to the centerline by a vortical flow on the interface. We also show that radial solute segregation depends significantly on whether account is taken of the anisotropy of the solid-phase thermal conductivity. Finally, the computations provide guidance as to

  12. Implementation of an anomalous radial transport model for continuum kinetic edge codes

    NASA Astrophysics Data System (ADS)

    Bodi, K.; Krasheninnikov, S. I.; Cohen, R. H.; Rognlien, T. D.

    2007-11-01

    Radial plasma transport in magnetic fusion devices is often dominated by plasma turbulence compared to neoclassical collisional transport. Continuum kinetic edge codes [such as the (2d,2v) transport version of TEMPEST and also EGK] compute the collisional transport directly, but there is a need to model the anomalous transport from turbulence for long-time transport simulations. Such a model is presented and results are shown for its implementation in the TEMPEST gyrokinetic edge code. The model includes velocity-dependent convection and diffusion coefficients expressed as a Hermite polynominals in velocity. The specification of the Hermite coefficients can be set, e.g., by specifying the ratio of particle and energy transport as in fluid transport codes. The anomalous transport terms preserve the property of no particle flux into unphysical regions of velocity space. TEMPEST simulations are presented showing the separate control of particle and energy anomalous transport, and comparisons are made with neoclassical transport also included.

  13. 1998 UBV Light Curves of Eclipsing Binary AI Draconis and Absolute Parameters

    NASA Astrophysics Data System (ADS)

    Jassur, D. M. Z.; Khaledian, M. S.; Kermani, M. H.

    New UBV photometry of Algol-Type eclipsing binary star AI Dra and the absolute physical parameters of this system have been presented. The light curve analysis carried out by the method of differential corrections indicates that both components are inside their Roche-Lobes. From combining the photometric solution with spectroscopic data obtained from velocity curve analysis, it has been found that the system consist of a main sequence primary and an evolved (subgiant) secondary.

  14. Anisotropic S-wave velocity structure from joint inversion of surface wave group velocity dispersion: A case study from India

    NASA Astrophysics Data System (ADS)

    Mitra, S.; Dey, S.; Siddartha, G.; Bhattacharya, S.

    2016-12-01

    We estimate 1-dimensional path average fundamental mode group velocity dispersion curves from regional Rayleigh and Love waves sampling the Indian subcontinent. The path average measurements are combined through a tomographic inversion to obtain 2-dimensional group velocity variation maps between periods of 10 and 80 s. The region of study is parametrised as triangular grids with 1° sides for the tomographic inversion. Rayleigh and Love wave dispersion curves from each node point is subsequently extracted and jointly inverted to obtain a radially anisotropic shear wave velocity model through global optimisation using Genetic Algorithm. The parametrization of the model space is done using three crustal layers and four mantle layers over a half-space with varying VpH , VsV and VsH. The anisotropic parameter (η) is calculated from empirical relations and the density of the layers are taken from PREM. Misfit for the model is calculated as a sum of error-weighted average dispersion curves. The 1-dimensional anisotropic shear wave velocity at each node point is combined using linear interpolation to obtain 3-dimensional structure beneath the region. Synthetic tests are performed to estimate the resolution of the tomographic maps which will be presented with our results. We envision to extend this to a larger dataset in near future to obtain high resolution anisotrpic shear wave velocity structure beneath India, Himalaya and Tibet.

  15. Absolute IGS antenna phase center model igs08.atx: status and potential improvements

    NASA Astrophysics Data System (ADS)

    Schmid, R.; Dach, R.; Collilieux, X.; Jäggi, A.; Schmitz, M.; Dilssner, F.

    2016-04-01

    On 17 April 2011, all analysis centers (ACs) of the International GNSS Service (IGS) adopted the reference frame realization IGS08 and the corresponding absolute antenna phase center model igs08.atx for their routine analyses. The latter consists of an updated set of receiver and satellite antenna phase center offsets and variations (PCOs and PCVs). An update of the model was necessary due to the difference of about 1 ppb in the terrestrial scale between two consecutive realizations of the International Terrestrial Reference Frame (ITRF2008 vs. ITRF2005), as that parameter is highly correlated with the GNSS satellite antenna PCO components in the radial direction.

  16. A catalogue of masses, structural parameters and velocity dispersion profiles of 112 Milky Way globular clusters

    NASA Astrophysics Data System (ADS)

    Baumgardt, H.; Hilker, M.

    2018-05-01

    We have determined masses, stellar mass functions and structural parameters of 112 Milky Way globular clusters by fitting a large set of N-body simulations to their velocity dispersion and surface density profiles. The velocity dispersion profiles were calculated based on a combination of more than 15,000 high-precision radial velocities which we derived from archival ESO/VLT and Keck spectra together with ˜20, 000 published radial velocities from the literature. Our fits also include the stellar mass functions of the globular clusters, which are available for 47 clusters in our sample, allowing us to self-consistently take the effects of mass segregation and ongoing cluster dissolution into account. We confirm the strong correlation between the global mass functions of globular clusters and their relaxation times recently found by Sollima & Baumgardt (2017). We also find a correlation of the escape velocity from the centre of a globular cluster and the fraction of first generation stars (FG) in the cluster recently derived for 57 globular clusters by Milone et al. (2017), but no correlation between the FG star fraction and the global mass function of a globular cluster. This could indicate that the ability of a globular cluster to keep the wind ejecta from the polluting star(s) is the crucial parameter determining the presence and fraction of second generation stars and not its later dynamical mass loss.

  17. Radial arm strike rail

    DOEpatents

    McKeown, Mark H.; Beason, Steven C.

    1991-01-01

    The radial arm strike rail assembly is a system for measurement of bearings, directions, and stereophotography for geologic mapping, particularly where magnetic compasses are not appropriate. The radial arm, pivoting around a shaft axis, provides a reference direction determination for geologic mapping and bearing or direction determination. The centerable and levelable pedestal provide a base for the radial arm strike rail and the telescoping camera pedestal. The telescoping feature of the radial arm strike rail allows positioning the end of the rail for strike direction or bearing measurement with a goniometer.

  18. Easy Absolute Values? Absolutely

    ERIC Educational Resources Information Center

    Taylor, Sharon E.; Mittag, Kathleen Cage

    2015-01-01

    The authors teach a problem-solving course for preservice middle-grades education majors that includes concepts dealing with absolute-value computations, equations, and inequalities. Many of these students like mathematics and plan to teach it, so they are adept at symbolic manipulations. Getting them to think differently about a concept that they…

  19. Shear velocity profiles in the crust and lithospheric mantle across Tibet

    NASA Astrophysics Data System (ADS)

    Agius, M. R.; Lebedev, S.

    2010-12-01

    We constrain variations in the crustal and lithospheric structure across Tibet, using phase velocities of seismic surface waves. The data are seismograms recorded by broadband instruments of permanent and temporary networks within and around the plateau. Phase-velocity measurements are performed in broad period ranges using an elaborate recent implementation of the 2-station method. A combination of the cross-correlation and multimode-waveform-inversion measurements using tens to hundreds of seismograms per station pair produces robust, accurate phase-velocity curves for Rayleigh and Love waves. We use our new measurements to infer phase-velocity variations and to constrain S-velocity profiles in different parts of the plateau, including radial anisotropy and depths of lithospheric discontinuities. We observe a mid-crustal low-velocity zone (LVZ) in the 20-45 km depth range across the plateau, with S-velocities within a 3.2-3.5 km/s range. This LVZ coincides with a low-resistivity layer inferred from magnetotelluric studies, interpreted as evidence for partial melting in the middle crust. Surface-wave data are also consistent with radial anisotropy in this layer, indicative of horizontal flow. At the north-eastern boundary of the plateau, past the Kunlun Fault, the mid-crustal LVZ, in the sense of an S-velocity decrease with depth in the 15-25 km depth range, is not required by the surface-wave data although the velocity is still relatively low. The mantle-lithosphere structure shows a pronounced contrast between the south-western and central-northern parts of the plateau. The south-west is underlain by a thick, high-velocity, craton-like lithospheric mantle. Below central Lhasa the uppermost mantle appears to be close to global average with an increase in velocity between 150 - 250 km depth. Beneath central and northern Tibet, the average S velocity between the Moho and 200 km depth is close to the global continental average (4.5 km/s). In order to investigate the

  20. Triple acting radial seal

    DOEpatents

    Ebert, Todd A [West Palm Beach, FL; Carella, John A [Jupiter, FL

    2012-03-13

    A triple acting radial seal used as an interstage seal assembly in a gas turbine engine, where the seal assembly includes an interstage seal support extending from a stationary inner shroud of a vane ring, the interstage seal support includes a larger annular radial inward facing groove in which an outer annular floating seal assembly is secured for radial displacement, and the outer annular floating seal assembly includes a smaller annular radial inward facing groove in which an inner annular floating seal assembly is secured also for radial displacement. A compliant seal is secured to the inner annular floating seal assembly. The outer annular floating seal assembly encapsulates the inner annular floating seal assembly which is made from a very low alpha material in order to reduce thermal stress.

  1. Absolute Properties of the Pulsating Post-mass Transfer Eclipsing Binary OO Draconis

    NASA Astrophysics Data System (ADS)

    Lee, Jae Woo; Hong, Kyeongsoo; Koo, Jae-Rim; Park, Jang-Ho

    2018-01-01

    OO Dra is a short-period Algol system with a δ Sct-like pulsator. We obtained time-series spectra between 2016 February and May to derive the fundamental parameters of the binary star and to study its evolutionary scenario. The radial velocity (RV) curves for both components were presented, and the effective temperature of the hotter and more massive primary was determined to be {T}{eff,1}=8260+/- 210 K by comparing the disentangling spectrum and the Kurucz models. Our RV measurements were solved with the BV light curves of Zhang et al. using the Wilson-Devinney binary code. The absolute dimensions of each component are determined as follows: M 1 = 2.03 ± 0.06 {M}⊙ , M 2 = 0.19 ± 0.01 {M}⊙ , R 1 = 2.08 ± 0.03 {R}⊙ , R 2 = 1.20 ± 0.02 {R}⊙ , L 1 = 18 ± 2 {L}⊙ , and L 2 = 2.0 ± 0.2 {L}⊙ . Comparison with stellar evolution models indicated that the primary star resides inside the δ Sct instability strip on the main sequence, while the cool secondary component is noticeably overluminous and oversized. We demonstrated that OO Dra is an oscillating post-mass transfer R CMa-type binary; the originally more massive star became the low-mass secondary component through mass loss caused by stellar wind and mass transfer, and the gainer became the pulsating primary as the result of mass accretion. The R CMa stars, such as OO Dra, are thought to have formed by non-conservative binary evolution and ultimately to evolve into EL CVn stars.

  2. FORTRAN program for predicting off-design performance of radial-inflow turbines

    NASA Technical Reports Server (NTRS)

    Wasserbauer, C. A.; Glassman, A. J.

    1975-01-01

    The FORTRAN IV program uses a one-dimensional solution of flow conditions through the turbine along the mean streamline. The program inputs needed are the design-point requirements and turbine geometry. The output includes performance and velocity-diagram parameters over a range of speed and pressure ratio. Computed performance is compared with the experimental data from two radial-inflow turbines and with the performance calculated by a previous computer program. The flow equations, program listing, and input and output for a sample problem are given.

  3. Lithospheric radial anisotropy beneath the Gulf of Mexico

    NASA Astrophysics Data System (ADS)

    Chu, Risheng; Ko, Justin Yen-Ting; Wei, Shengji; Zhan, Zhongwen; Helmberger, Don

    2017-05-01

    The Lithosphere-Asthenosphere Boundary (LAB), where a layer of low viscosity asthenosphere decouples with the upper plate motion, plays an essential role in plate tectonics. Most dynamic modeling assumes that the shear velocity can be used as a surrogate for viscosity which provides key information about mantle flow. Here, we derive a shear velocity model for the LAB structure beneath the Gulf of Mexico allowing a detailed comparison with that beneath the Pacific (PAC) and Atlantic (ATL). Our study takes advantage of the USArray data from the March 25th, 2013 Guatemala earthquake at a depth of 200 km. Such data is unique in that we can observe a direct upward traveling lid arrival which remains the first arrival ahead of the triplications beyond 18°. This extra feature in conjunction with upper-mantle triplication sampling allows good depth control of the LAB and a new upper-mantle seismic model ATM, a modification of ATL, to be developed. ATM has a prominent low velocity zone similar to the structure beneath the western Atlantic. The model contains strong radial anisotropy in the lid where VSH is about 6% faster than VSV. This anisotropic feature ends at the bottom of the lithosphere at about the depth of 175 km in contrast to the Pacific where it extends to over 300 km. Another important feature of ATM is the weaker velocity gradient from the depth of 175 to 350 km compared to Pacific models, which may be related to differences in mantle flow.

  4. Absolutely relative or relatively absolute: violations of value invariance in human decision making.

    PubMed

    Teodorescu, Andrei R; Moran, Rani; Usher, Marius

    2016-02-01

    Making decisions based on relative rather than absolute information processing is tied to choice optimality via the accumulation of evidence differences and to canonical neural processing via accumulation of evidence ratios. These theoretical frameworks predict invariance of decision latencies to absolute intensities that maintain differences and ratios, respectively. While information about the absolute values of the choice alternatives is not necessary for choosing the best alternative, it may nevertheless hold valuable information about the context of the decision. To test the sensitivity of human decision making to absolute values, we manipulated the intensities of brightness stimuli pairs while preserving either their differences or their ratios. Although asked to choose the brighter alternative relative to the other, participants responded faster to higher absolute values. Thus, our results provide empirical evidence for human sensitivity to task irrelevant absolute values indicating a hard-wired mechanism that precedes executive control. Computational investigations of several modelling architectures reveal two alternative accounts for this phenomenon, which combine absolute and relative processing. One account involves accumulation of differences with activation dependent processing noise and the other emerges from accumulation of absolute values subject to the temporal dynamics of lateral inhibition. The potential adaptive role of such choice mechanisms is discussed.

  5. Magellan/PFS Radial Velocities of GJ 9827, a Late K dwarf at 30 pc with Three Transiting Super-Earths

    NASA Astrophysics Data System (ADS)

    Teske, Johanna K.; Wang, Sharon; Wolfgang, Angie; Dai, Fei; Shectman, Stephen A.; Butler, R. Paul; Crane, Jeffrey D.; Thompson, Ian B.

    2018-04-01

    The Kepler mission showed us that planets with sizes between that of Earth and Neptune appear to be the most common type in our Galaxy. These “super-Earths” continue to be of great interest for exoplanet formation, evolution, and composition studies. However, the number of super-Earths with well-constrained mass and radius measurements remains small (40 planets with σ mass < 25%), due in part to the faintness of their host stars causing ground-based mass measurements to be challenging. Recently, three transiting super-Earth planets were detected by the K2 mission around the nearby star GJ 9827/HIP 115752, at only 30 pc away. The radii of the planets span the “radius gap” detected by Fulton et al. (2017), and all orbit within ∼6.5 days, easing follow-up observations. Here, we report radial velocity (RV) observations of GJ 9827, taken between 2010 and 2016 with the Planet Finder Spectrograph on the Magellan II Telescope. We employ two different RV analysis packages, SYSTEMIC and RADVEL, to derive masses and thus densities of the GJ 9827 planets. We also test a Gaussian Process regression analysis but find the correlated stellar noise is not well constrained by the PFS data and that the GP tends to over-fit the RV semi-amplitudes resulting in a lower K value. Our RV observations are not able to place strong mass constraints on the two outer planets (c and d) but do indicate that planet b, at 1.64 R ⊕ and ∼8 M ⊕, is one of the most massive (and dense) super-Earth planets detected to date.

  6. The conjectured S-type retrograde planet in ν Octantis: more evidence including four years of iodine-cell radial velocities

    NASA Astrophysics Data System (ADS)

    Ramm, D. J.; Nelson, B. E.; Endl, M.; Hearnshaw, J. B.; Wittenmyer, R. A.; Gunn, F.; Bergmann, C.; Kilmartin, P.; Brogt, E.

    2016-08-01

    We report 1212 radial-velocity (RV) measurements obtained in the years 2009-2013 using an iodine cell for the spectroscopic binary ν Octantis (K1 III/IV). This system (a_{bin} ˜ 2.6 au, P ˜ 1050 d) is conjectured to have a Jovian planet with a semimajor axis half that of the binary host. The extreme geometry only permits long-term stability if the planet is in a retrograde orbit. Whilst the reality of the planet (P ˜ 415 d) remains uncertain, other scenarios (stellar variability or apsidal motion caused by a yet unobserved third star) continue to appear substantially less credible based on cross-correlation function bisectors, line-depth ratios and many other independent details. If this evidence is validated but the planet is disproved, the claims of other planets using RVs will be seriously challenged. We also describe a significant revision to the previously published RVs and the full set of 1437 RVs now encompasses nearly 13 yr. The sensitive orbital dynamics allow us to constrain the 3D architecture with a broad prior probability distribution on the mutual inclination, which with posterior samples obtained from an N-body Markov chain Monte Carlo is found to be 152.5°±^{0.7}_{0.6}. None of these samples are dynamically stable beyond 106 yr. However, a grid search around the best-fitting solution finds a region that has many models stable for 107 yr, and includes one model within 1σ that is stable for at least 108 yr. The planet's exceptional nature demands robust independent verification and makes the theoretical understanding of its formation a worthy challenge.

  7. SOAP 2.0: a tool to estimate the photometric and radial velocity variations induced by stellar spots and plages

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

    Dumusque, X.; Boisse, I.; Santos, N. C., E-mail: xdumusque@cfa.harvard.edu

    2014-12-01

    This paper presents SOAP 2.0, a new version of the Spot Oscillation And Planet (SOAP) code that estimates in a simple way the photometric and radial velocity (RV) variations induced by active regions. The inhibition of the convective blueshift (CB) inside active regions is considered, as well as the limb brightening effect of plages, a quadratic limb darkening law, and a realistic spot and plage contrast ratio. SOAP 2.0 shows that the activity-induced variation of plages is dominated by the inhibition of the CB effect. For spots, this effect becomes significant only for slow rotators. In addition, in the casemore » of a major active region dominating the activity-induced signal, the ratio between the FWHM and the RV peak-to-peak amplitudes of the cross correlation function can be used to infer the type of active region responsible for the signal for stars with v sin i ≤8 km s{sup –1}. A ratio smaller than three implies a spot, while a larger ratio implies a plage. Using the observation of HD 189733, we show that SOAP 2.0 manages to reproduce the activity variation as well as previous simulations when a spot is dominating the activity-induced variation. In addition, SOAP 2.0 also reproduces the activity variation induced by a plage on the slowly rotating star α Cen B, which is not possible using previous simulations. Following these results, SOAP 2.0 can be used to estimate the signal induced by spots and plages, but also to correct for it when a major active region is dominating the RV variation.« less

  8. Radial heterogeneity of some analytical columns used in high-performance liquid chromatography.

    PubMed

    Abia, Jude A; Mriziq, Khaled S; Guiochon, Georges A

    2009-04-10

    An on-column electrochemical microdetector was used to determine accurately the radial distribution of the mobile phase velocity and of the column efficiency at the exit of three common analytical columns, namely a 100 mm x 4.6mm C18 bonded silica-based monolithic column, a 150 mm x 4.6mm column packed with 2.7 microm porous shell particles of C18 bonded silica (HALO), and a 150 mm x 4.6mm column packed with 3 microm fully porous C18 bonded silica particles (LUNA). The results obtained demonstrate that all three columns are not radially homogeneous. In all three cases, the efficiency was found to be lower in the wall region of the column than in its core region (the central core with a radius of 1/3 the column inner radius). The decrease in local efficiency from the core to the wall regions was lower in the case of the monolith (ca. 25%) than in that of the two particle-packed columns (ca. 35-50%). The mobile phase velocity was found to be ca. 1.5% higher in the wall than in the core region of the monolithic column while, in contrast, it was ca. 2.5-4.0% lower in the wall region for the two particle-packed columns.

  9. Radial evolution of ion distribution functions

    NASA Technical Reports Server (NTRS)

    Marsch, E.

    1983-01-01

    A survey of solar wind ion velocity distributions and derived parameters (temperature, ion differential speed, heat flux, adiabatic invariants) is presented with emphasis on the heliocentric distance range between 0.3 and 1 AU traversed by the Helios solar probe. The radial evolution of nonthermal features are discussed which are observed to be most pronounced at perihelion. Within the framework of quasilinear plasma theory, wave particle interactions that may shape the ion distributions are considered. Some results of a self consistent model calculation are presented accounting for ion acceleration and heating by resonant momentum and energy exchange with ion cyclotron and magnetosonic waves propagating away from the Sun along the interplanetary magnetic field. Another tentative explanation for the occurrence of large perpendicular proton temperatures is offered in terms of heating by Landau damping of lower hybrid waves.

  10. Predictions of Planet Detections with Near-infrared Radial Velocities in the Upcoming SPIRou Legacy Survey-planet Search

    NASA Astrophysics Data System (ADS)

    Cloutier, Ryan; Artigau, Étienne; Delfosse, Xavier; Malo, Lison; Moutou, Claire; Doyon, René; Donati, Jean-Francois; Cumming, Andrew; Dumusque, Xavier; Hébrard, Élodie; Menou, Kristen

    2018-02-01

    The SPIRou near-infrared spectropolarimeter is destined to begin science operations at the Canada–France–Hawaii Telescope in mid-2018. One of the instrument’s primary science goals is to discover the closest exoplanets to the solar system by conducting a three- to five-year long radial velocity survey of nearby M dwarfs at an expected precision of ∼1 m s‑1, the SPIRou Legacy Survey-Planet Search (SLS-PS). In this study, we conduct a detailed Monte Carlo simulation of the SLS-PS using our current understanding of the occurrence rate of M dwarf planetary systems and physical models of stellar activity. From simultaneous modeling of planetary signals and activity, we predict the population of planets to be detected in the SLS-PS. With our fiducial survey strategy and expected instrument performance over a nominal survey length of ∼3 years, we expect SPIRou to detect {85.3}-12.4+29.3 planets including {20.0}-7.2+16.8 habitable-zone planets and {8.1}-3.2+7.6 Earth-like planets from a sample of 100 M1–M8.5 dwarfs out to 11 pc. By studying mid-to-late M dwarfs previously inaccessible to existing optical velocimeters, SPIRou will put meaningful constraints on the occurrence rate of planets around those stars including the value of {η }\\oplus at an expected level of precision of ≲ 45 % . We also predict that a subset of {46.7}-6.0+16.0 planets may be accessible with dedicated high-contrast imagers on the next generation of extremely large telescopes including {4.9}-2.0+4.7 potentially imagable Earth-like planets. Lastly, we compare the results of our fiducial survey strategy to other foreseeable survey versions to quantify which strategy is optimized to reach the SLS-PS science goals. The results of our simulations are made available to the community on GitHub (https://github.com/r-cloutier/SLSPS_Simulations).

  11. Bayesian inversion of surface-wave data for radial and azimuthal shear-wave anisotropy, with applications to central Mongolia and west-central Italy

    NASA Astrophysics Data System (ADS)

    Ravenna, Matteo; Lebedev, Sergei

    2018-04-01

    Seismic anisotropy provides important information on the deformation history of the Earth's interior. Rayleigh and Love surface-waves are sensitive to and can be used to determine both radial and azimuthal shear-wave anisotropies at depth, but parameter trade-offs give rise to substantial model non-uniqueness. Here, we explore the trade-offs between isotropic and anisotropic structure parameters and present a suite of methods for the inversion of surface-wave, phase-velocity curves for radial and azimuthal anisotropies. One Markov chain Monte Carlo (McMC) implementation inverts Rayleigh and Love dispersion curves for a radially anisotropic shear velocity profile of the crust and upper mantle. Another McMC implementation inverts Rayleigh phase velocities and their azimuthal anisotropy for profiles of vertically polarized shear velocity and its depth-dependent azimuthal anisotropy. The azimuthal anisotropy inversion is fully non-linear, with the forward problem solved numerically at different azimuths for every model realization, which ensures that any linearization biases are avoided. The computations are performed in parallel, in order to reduce the computing time. The often challenging issue of data noise estimation is addressed by means of a Hierarchical Bayesian approach, with the variance of the noise treated as an unknown during the radial anisotropy inversion. In addition to the McMC inversions, we also present faster, non-linear gradient-search inversions for the same anisotropic structure. The results of the two approaches are mutually consistent; the advantage of the McMC inversions is that they provide a measure of uncertainty of the models. Applying the method to broad-band data from the Baikal-central Mongolia region, we determine radial anisotropy from the crust down to the transition-zone depths. Robust negative anisotropy (Vsh < Vsv) in the asthenosphere, at 100-300 km depths, presents strong new evidence for a vertical component of asthenospheric

  12. Radial polar histogram: obstacle avoidance and path planning for robotic cognition and motion control

    NASA Astrophysics Data System (ADS)

    Wang, Po-Jen; Keyawa, Nicholas R.; Euler, Craig

    2012-01-01

    In order to achieve highly accurate motion control and path planning for a mobile robot, an obstacle avoidance algorithm that provided a desired instantaneous turning radius and velocity was generated. This type of obstacle avoidance algorithm, which has been implemented in California State University Northridge's Intelligent Ground Vehicle (IGV), is known as Radial Polar Histogram (RPH). The RPH algorithm utilizes raw data in the form of a polar histogram that is read from a Laser Range Finder (LRF) and a camera. A desired open block is determined from the raw data utilizing a navigational heading and an elliptical approximation. The left and right most radii are determined from the calculated edges of the open block and provide the range of possible radial paths the IGV can travel through. In addition, the calculated obstacle edge positions allow the IGV to recognize complex obstacle arrangements and to slow down accordingly. A radial path optimization function calculates the best radial path between the left and right most radii and is sent to motion control for speed determination. Overall, the RPH algorithm allows the IGV to autonomously travel at average speeds of 3mph while avoiding all obstacles, with a processing time of approximately 10ms.

  13. Measurement of fast-changing low velocities by photonic Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Song, Hongwei; Wu, Xianqian; Huang, Chenguang; Wei, Yangpeng; Wang, Xi

    2012-07-01

    Despite the increasing popularity of photonic Doppler velocimetry (PDV) in shock wave experiments, its capability of capturing low particle velocities while changing rapidly is still questionable. The paper discusses the performance of short time Fourier transform (STFT) and continuous wavelet transform (CWT) in processing fringe signals of fast-changing low velocities measured by PDV. Two typical experiments are carried out to evaluate the performance. In the laser shock peening test, the CWT gives a better interpretation to the free surface velocity history, where the elastic precursor, main plastic wave, and elastic release wave can be clearly identified. The velocities of stress waves, Hugoniot elastic limit, and the amplitude of shock pressure induced by laser can be obtained from the measurement. In the Kolsky-bar based tests, both methods show validity of processing the longitudinal velocity signal of incident bar, whereas CWT improperly interprets the radial velocity of the shocked sample at the beginning period, indicating the sensitiveness of the CWT to the background noise. STFT is relatively robust in extracting waveforms of low signal-to-noise ratio. Data processing method greatly affects the temporal resolution and velocity resolution of a given fringe signal, usually CWT demonstrates a better local temporal resolution and velocity resolution, due to its adaptability to the local frequency, also due to the finer time-frequency product according to the uncertainty principle.

  14. Measurement of fast-changing low velocities by photonic Doppler velocimetry.

    PubMed

    Song, Hongwei; Wu, Xianqian; Huang, Chenguang; Wei, Yangpeng; Wang, Xi

    2012-07-01

    Despite the increasing popularity of photonic Doppler velocimetry (PDV) in shock wave experiments, its capability of capturing low particle velocities while changing rapidly is still questionable. The paper discusses the performance of short time Fourier transform (STFT) and continuous wavelet transform (CWT) in processing fringe signals of fast-changing low velocities measured by PDV. Two typical experiments are carried out to evaluate the performance. In the laser shock peening test, the CWT gives a better interpretation to the free surface velocity history, where the elastic precursor, main plastic wave, and elastic release wave can be clearly identified. The velocities of stress waves, Hugoniot elastic limit, and the amplitude of shock pressure induced by laser can be obtained from the measurement. In the Kolsky-bar based tests, both methods show validity of processing the longitudinal velocity signal of incident bar, whereas CWT improperly interprets the radial velocity of the shocked sample at the beginning period, indicating the sensitiveness of the CWT to the background noise. STFT is relatively robust in extracting waveforms of low signal-to-noise ratio. Data processing method greatly affects the temporal resolution and velocity resolution of a given fringe signal, usually CWT demonstrates a better local temporal resolution and velocity resolution, due to its adaptability to the local frequency, also due to the finer time-frequency product according to the uncertainty principle.

  15. Measurement of fast-changing low velocities by photonic Doppler velocimetry

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

    Song Hongwei; Wu Xianqian; Huang Chenguang

    2012-07-15

    Despite the increasing popularity of photonic Doppler velocimetry (PDV) in shock wave experiments, its capability of capturing low particle velocities while changing rapidly is still questionable. The paper discusses the performance of short time Fourier transform (STFT) and continuous wavelet transform (CWT) in processing fringe signals of fast-changing low velocities measured by PDV. Two typical experiments are carried out to evaluate the performance. In the laser shock peening test, the CWT gives a better interpretation to the free surface velocity history, where the elastic precursor, main plastic wave, and elastic release wave can be clearly identified. The velocities of stressmore » waves, Hugoniot elastic limit, and the amplitude of shock pressure induced by laser can be obtained from the measurement. In the Kolsky-bar based tests, both methods show validity of processing the longitudinal velocity signal of incident bar, whereas CWT improperly interprets the radial velocity of the shocked sample at the beginning period, indicating the sensitiveness of the CWT to the background noise. STFT is relatively robust in extracting waveforms of low signal-to-noise ratio. Data processing method greatly affects the temporal resolution and velocity resolution of a given fringe signal, usually CWT demonstrates a better local temporal resolution and velocity resolution, due to its adaptability to the local frequency, also due to the finer time-frequency product according to the uncertainty principle.« less

  16. Constraints on radial anisotropy in the central Pacific upper mantle from the NoMelt OBS array

    NASA Astrophysics Data System (ADS)

    Russell, J. B.; Gaherty, J. B.; Lin, P. P.; Zebker, M.

    2016-12-01

    Observations of seismic anisotropy in ocean basins are important for constraining deformation and melting processes in the upper mantle. The NoMelt OBS array was deployed on relatively pristine, 70-Ma seafloor in the central Pacific with the aim of constraining upper-mantle circulation and the evolution of the lithosphere-asthenosphere system. Azimuthal variations in Rayleigh-wave velocity suggest strong anisotropic fabric both in the lithosphere and deep in the asthenosphere, and we aim to evaluate whether radial anisotropy shows a similar pattern. We use a combination of Love waves from earthquakes (20-100 s) as well as high-frequency ambient noise (5-10 s) to estimate VSH in the upper 300 km beneath the NoMelt array. Waveform fitting of the ambient-noise cross spectra provide phase-velocity estimates that are sensitive to the upper 50 km of the mantle. To constrain structure beneath the lid, we employ an array-based approach to measure Love-wave phase velocities across the array using seven shallow-focus events (< 25 km) with high signal-to-noise ratio and diverse azimuthal coverage. The Love wave phase-velocity measurements suggest strong interference of the first overtone for intermediate periods (20-50 s), while longer periods (>60 s) are mostly dominated by fundamental mode energy. Through forward modeling of Love wave Fréchet kernels, we find an extremely strong nonlinearity in individual mode-branch sensitivity that is dependent on the relative velocity difference between the low-velocity zone (LVZ) and the overlying Pacific lid. For the fundamental mode in the presence of a strong LVZ, intermediate periods (20-50 s) have little sensitivity within the lithospheric mantle with peak sensitivity pushed to the base of the low-velocity zone. This peak sensitivity migrates to much shallower depth as the lid/LVZ contrast is reduced. Therefore, we use a Monte Carlo approach to systematically explore the model space and identify the most robust model features

  17. Radial segregation induced by natural convection and melt/solid interface shape in vertical Bridgman growth

    NASA Technical Reports Server (NTRS)

    Chang, C. J.; Brown, R. A.

    1983-01-01

    The roles of natural convection in the melt and the shape of the melt/solid interface on radial dopant segregation are analyzed for a prototype of vertical Bridgman crystal growth system by finite element methods that solve simultaneously for the velocity field in the melt, the shape of the solidification isotherm, and the temperature distribution in both phases. Results are presented for crystal and melt with thermophysical properties similar to those of gallium-doped germanium in Bridgman configurations with melt below (thermally destabilizing) and above (stabilizing) the crystal. Steady axisymmetric flow are classified according to Rayleigh number as either being nearly the growth velocity, having a weak cellular structure or having large amplitude cellular convention. The flows in the two Bridgman configurations are driven by different temperature gradients and are in opposite directions. Finite element calculations for the transport of a dilute dopant by these flow fields reveal radial segregation levels as large as sixty percent of the mean concentration. Segregation is found most severe at an intermediate value of Rayleigh number above which the dopant distribution along the interface levels as the intensity of the flow increases.

  18. Nozzle geometry and forward velocity effects on noise for CTOL engine-over-the-wing concept

    NASA Technical Reports Server (NTRS)

    Vonglahn, U. H.; Goodykoontz, J. H.; Wagner, J. M.

    1973-01-01

    Acoustic shielding benefits for jet noise of engine-over-the-wing for conventional aircraft (CTOL) application were studied with and without forward velocity for various small-scale nozzles. These latter included convergent, bypass and mixer, with and without forward ejector, nozzles. A 13-inch free jet was used to provide forward velocity. Farfield noise data were obtained for subsonic jet velocities from 650 to 980 ft/sec and forward velocities from zero to 360 ft/sec. The studies showed that although shielding benefits were obtained with all nozzles, the greatest benefits were obtained with mixer nozzles. The absolute magnitude of the jet noise shielding benefits with forward velocity was similar to the variation in nozzle-only noise with forward velocity.

  19. The innate origin of radial and vertical gradients in a simulated galaxy disc

    NASA Astrophysics Data System (ADS)

    Navarro, Julio F.; Yozin, Cameron; Loewen, Nic; Benítez-Llambay, Alejandro; Fattahi, Azadeh; Frenk, Carlos S.; Oman, Kyle A.; Schaye, Joop; Theuns, Tom

    2018-05-01

    We examine the origin of radial and vertical gradients in the age/metallicity of the stellar component of a galaxy disc formed in the APOSTLE cosmological hydrodynamical simulations. Some of these gradients resemble those in the Milky Way, where they have sometimes been interpreted as due to internal evolution, such as scattering off giant molecular clouds, radial migration driven by spiral patterns, or orbital resonances with a bar. Secular processes play a minor role in the simulated galaxy, which lacks strong spiral or bar patterns, and where such gradients arise as a result of the gradual enrichment of a gaseous disc that is born thick but thins as it turns into stars and settles into centrifugal equilibrium. The settling is controlled by the feedback of young stars; which links the star formation, enrichment, and equilibration time-scales, inducing radial and vertical gradients in the gaseous disc and its descendent stars. The kinematics of coeval stars evolve little after birth and provide a faithful snapshot of the gaseous disc structure at the time of their formation. In this interpretation, the age-velocity dispersion relation would reflect the gradual thinning of the disc rather than the importance of secular orbit scattering; the outward flaring of stars would result from the gas disc flare rather than from radial migration; and vertical gradients would arise because the gas disc gradually thinned as it enriched. Such radial and vertical trends might just reflect the evolving properties of the parent gaseous disc, and are not necessarily the result of secular evolutionary processes.

  20. Relative differences in strength and power from slow to fast isokinetic velocities may reflect dynapenia.

    PubMed

    Jenkins, Nathaniel D M; Housh, Terry J; Palmer, Ty B; Cochrane, Kristen C; Bergstrom, Haley C; Johnson, Glen O; Schmidt, Richard J; Cramer, Joel T

    2015-07-01

    We compared absolute and normalized values for peak torque (PT), mean power (MP), rate of velocity development, and electromyography (EMG) amplitude during maximal isometric and concentric isokinetic leg extension muscle actions, as well as the %decrease in PT and %increase in MP from 1.05 to 3.14 rad·s(-1) in younger versus older men. Measurements were performed twice for reliability. Isokinetic measurements were normalized to the isometric muscle actions. Absolute isometric PT, isokinetic PT and MP, and EMG amplitudes at 1.05 and 3.14 rad·s(-1) were greater in the younger men, although normalizing to isometric PT eliminated the age differences. The older men exhibited greater %decrease in PT (37.2% vs. 31.3%) and lower %increase in MP (87.6% vs. 126.4%) regardless of normalization. Normalization eliminated absolute differences in isokinetic strength and power, but the relative differences from slow to fast velocities may reflect dynapenia characterized by age-related decreases in fast-twitch fiber function. © 2014 Wiley Periodicals, Inc.

  1. Experimental viscous fingering in a tapered radial Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Bongrand, Gregoire; Tsai, Peichun Amy; Complex Fludis Group Team

    2017-11-01

    The fluid-fluid displacement in porous media is a common process that finds direct applications in various fields, such as enhanced oil recovery and geological CO2 sequestration. In this work, we experimentally investigate the influence of converging cells on viscous fingering instabilities using a radially-tapered cell. For air displacing oil, in contrast to the classical Saffman-Taylor fingering, our results show that a converging gradient in a radial propagation can provide a stabilizing effect and hinder fingering. For a fixed gap gradient and thickness, with increasing injection rates we find a stable displacement under small flow rates, whereas unstable fingering occurs above a certain threshold. We further investigate this critical flow rate delineating the stable and unstable regimes for different gap gradients. These results reveal that the displacement efficiency not only depends on the fluid properties but also on the interfacial velocity and channel structure. The latter factors provide a useful and convenient control to either trigger or inhibit fingering instability. NSERC Discovery, Accelerator, and CRC programs.

  2. Velocity measurements in the plume of an arcjet engine

    NASA Technical Reports Server (NTRS)

    Pivirotto, T. J.; Deininger, W. D.

    1987-01-01

    A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail.

  3. Light and Velocity Variability in Seven Bright Proto-Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    McGuire, Ryan

    2009-01-01

    Light and Velocity Variability in Seven Bright Proto-Planetary Nebulae R.B. McGuire, C.M. Steele, B.J. Hrivnak, W. Lu, D. Bohlender, C.D. Scarfe We present new contemporaneous light and velocity observations of seven proto-planetary nebulae obtained over the past two years. Proto-planetary nebulae are objects evolving between the AGB and planetary nebula phases. In these seven objects, the central star is bright (V= 7-10), surrounded by a faint nebula. We knew from past monitoring that the light from each of these varied by a few tenths of a magnitude over intervals of 30-150 days and that the velocity varied by 10 km/s. These appear to be due to pulsation. With these new contemporaneous observations, we are able to measure the correlation between the brightness, color, and velocity, which will constrain the pulsation models. This is an ongoing project with the light monitoring being carried out with the Valparaiso University 0.4 m telescope and CCD camera and the radial velocity observations being carried out with the Dominion Astrophysical Observatory 1.8 m telescope and spectrograph. This research is partially supported by NSF grant 0407087 and the Indiana Space Grant Consortium.

  4. Anatomic fit of six different radial head plates: comparison of precontoured low-profile radial head plates.

    PubMed

    Burkhart, Klaus Josef; Nowak, Tobias E; Kim, Yoon-Joo; Rommens, Pol M; Müller, Lars P

    2011-04-01

    Bulky implants may lead to symptomatic soft tissue irritation after open reduction and internal fixation of radial head and neck fractures. The purpose of our study was to compare the anatomic fit of precontoured radial head plates. We stripped 22 embalmed human cadaveric radiuses of soft tissues. We investigated 6 radial head plates: (1) the Medartis radial head buttress plate (MBP), (2) the Medartis radial head rim plate (MRP), (3) the Synthes radial neck plate (SNP), (4) the Synthes radial head plate (SHP), (5) the Acumed radial head plate (AHP), and (6) the Wright radial head plate (WHP). Each plate was applied to each radial head at the place of best fit within the safe zone. We tested 4 parameters of anatomic fit: (1) plate-to-bone distance, (2) plate contact judged by 3 different observers, (3) pin-subchondral zone distance, and (4) plate-to-bone contact after adjustment of the plates. The MBP and MRP showed the lowest profile by objective measurements, the SNP and AHP had a moderate profile, and the SHP and WHP demonstrated the bulkiest profile. The subjective assessments also demonstrated the best fit for the MBP, a good fit for the SNP, a moderate fit for the MRP and AHP, and a poor fit for the SHP and WHP. The MBP, MRP, and AHP could always provide pin-subchondral zone contact, unlike the SHP, SNP, and WHP. After bending, significant improvement of plate-to-bone distance could only be seen for the MBP, MRP, and WHP. The ranking among plates remained the same except for the WHP, which showed a significantly lower plate-to-bone distance than the SHP. Currently available radial head implants are heterogeneous. The MBP and MRP showed the lowest profile and best anatomic fit. Owing to the complex radial head anatomy, to date there is no one radial head plate that perfectly fits all radial heads. Conformance of existing plates to the radial head and neck is not perfect. Careful plate selection and modification, when necessary, may minimize interference of this

  5. A crustal seismic velocity model for the UK, Ireland and surrounding seas

    USGS Publications Warehouse

    Kelly, A.; England, R.W.; Maguire, Peter K.H.

    2007-01-01

    A regional model of the 3-D variation in seismic P-wave velocity structure in the crust of NW Europe has been compiled from wide-angle reflection/refraction profiles. Along each 2-D profile a velocity-depth function has been digitised at 5 km intervals. These 1-D velocity functions were mapped into three dimensions using ordinary kriging with weights determined to minimise the difference between digitised and interpolated values. An analysis of variograms of the digitised data suggested a radial isotropic weighting scheme was most appropriate. Horizontal dimensions of the model cells are optimised at 40 ?? 40 km and the vertical dimension at 1 km. The resulting model provides a higher resolution image of the 3-D variation in seismic velocity structure of the UK, Ireland and surrounding areas than existing models. The construction of the model through kriging allows the uncertainty in the velocity structure to be assessed. This uncertainty indicates the high density of data required to confidently interpolate the crustal velocity structure, and shows that for this region the velocity is poorly constrained for large areas away from the input data. ?? 2007 The Authors Journal compilation ?? 2007 RAS.

  6. Absolute biological needs.

    PubMed

    McLeod, Stephen

    2014-07-01

    Absolute needs (as against instrumental needs) are independent of the ends, goals and purposes of personal agents. Against the view that the only needs are instrumental needs, David Wiggins and Garrett Thomson have defended absolute needs on the grounds that the verb 'need' has instrumental and absolute senses. While remaining neutral about it, this article does not adopt that approach. Instead, it suggests that there are absolute biological needs. The absolute nature of these needs is defended by appeal to: their objectivity (as against mind-dependence); the universality of the phenomenon of needing across the plant and animal kingdoms; the impossibility that biological needs depend wholly upon the exercise of the abilities characteristic of personal agency; the contention that the possession of biological needs is prior to the possession of the abilities characteristic of personal agency. Finally, three philosophical usages of 'normative' are distinguished. On two of these, to describe a phenomenon or claim as 'normative' is to describe it as value-dependent. A description of a phenomenon or claim as 'normative' in the third sense does not entail such value-dependency, though it leaves open the possibility that value depends upon the phenomenon or upon the truth of the claim. It is argued that while survival needs (or claims about them) may well be normative in this third sense, they are normative in neither of the first two. Thus, the idea of absolute need is not inherently normative in either of the first two senses. © 2013 John Wiley & Sons Ltd.

  7. Constraints on radial migration in spiral galaxies - II. Angular momentum distribution and preferential migration

    NASA Astrophysics Data System (ADS)

    Daniel, Kathryne J.; Wyse, Rosemary F. G.

    2018-05-01

    The orbital angular momentum of individual stars in galactic discs can be permanently changed through torques from transient spiral patterns. Interactions at the corotation resonance dominate these changes and have the further property of conserving orbital circularity. We derived in an earlier paper an analytic criterion that an unperturbed stellar orbit must satisfy in order for such an interaction to occur, i.e. for it to be in a trapped orbit around corotation. We here use this criterion in an investigation of how the efficiency of induced radial migration for a population of disc stars varies with the angular momentum distribution of that population. We frame our results in terms of the velocity dispersion of the population, this being an easier observable than is the angular momentum distribution. Specifically, we investigate how the fraction of stars in trapped orbits at corotation varies with the velocity dispersion of the population, for a system with an assumed flat rotation curve. Our analytic results agree with the finding from simulations that radial migration is less effective in populations with `hotter' kinematics. We further quantify the dependence of this trapped fraction on the strength of the spiral pattern, finding a higher trapped fraction for higher amplitude perturbations.

  8. Convective blueshifts in the solar atmosphere. I. Absolute measurements with LARS of the spectral lines at 6302 Å

    NASA Astrophysics Data System (ADS)

    Löhner-Böttcher, J.; Schmidt, W.; Stief, F.; Steinmetz, T.; Holzwarth, R.

    2018-03-01

    Context. The solar convection manifests as granulation and intergranulation at the solar surface. In the photosphere, convective motions induce differential Doppler shifts to spectral lines. The observed convective blueshift varies across the solar disk. Aim. We focus on the impact of solar convection on the atmosphere and aim to resolve its velocity stratification in the photosphere. Methods: We performed high-resolution spectroscopic observations of the solar spectrum in the 6302 Å range with the Laser Absolute Reference Spectrograph at the Vacuum Tower Telescope. A laser frequency comb enabled the calibration of the spectra to an absolute wavelength scale with an accuracy of 1 m s-1. We systematically scanned the quiet Sun from the disk center to the limb at ten selected heliocentric positions. The analysis included 99 time sequences of up to 20 min in length. By means of ephemeris and reference corrections, we translated wavelength shifts into absolute line-of-sight velocities. A bisector analysis on the line profiles yielded the shapes and convective shifts of seven photospheric lines. Results: At the disk center, the bisector profiles of the iron lines feature a pronounced C-shape with maximum convective blueshifts of up to -450 m s-1 in the spectral line wings. Toward the solar limb, the bisectors change into a "\\"-shape with a saturation in the line core at a redshift of +100 m s-1. The center-to-limb variation of the line core velocities shows a slight increase in blueshift when departing the disk center for larger heliocentric angles. This increase in blueshift is more pronounced for the magnetically less active meridian than for the equator. Toward the solar limb, the blueshift decreases and can turn into a redshift. In general, weaker lines exhibit stronger blueshifts. Conclusions: Best spectroscopic measurements enabled the accurate determination of absolute convective shifts in the solar photosphere. We convolved the results to lower spectral

  9. Upper mantle structure of shear-waves velocities and stratification of anisotropy in the Afar Hotspot region

    NASA Astrophysics Data System (ADS)

    Sicilia, D.; Montagner, J.-P.; Cara, M.; Stutzmann, E.; Debayle, E.; Lépine, J.-C.; Lévêque, J.-J.; Beucler, E.; Sebai, A.; Roult, G.; Ayele, A.; Sholan, J. M.

    2008-12-01

    The Afar area is one of the biggest continental hotspots active since about 30 Ma. It may be the surface expression of a mantle "plume" related to the African Superswell. Central Africa is also characterized by extensive intraplate volcanism. Around the same time (30 Ma), volcanic activity re-started in several regions of the African plate and hotspots such as Darfur, Tibesti, Hoggar and Mount Cameroon, characterized by a significant though modest volcanic production. The interactions of mantle upwelling with asthenosphere, lithosphere and crust remain unclear and seismic anisotropy might help in investigating these complex interactions. We used data from the global seismological permanent FDSN networks (GEOSCOPE, IRIS, MedNet, GEO- FON, etc.), from the temporary PASSCAL experiments in Tanzania and Saudi Arabia and a French deployment of 5 portable broadband stations surrounding the Afar Hotspot. A classical two-step tomographic inversion from surface waves performed in the Horn of Africa with selected Rayleigh wave and Love wave seismograms leads to a 3D-model of both S V velocities and azimuthal anisotropy, as well as radial SH/ SV anisotropy, with a lateral resolution of 500 km. The region is characterized by low shear-wave velocities beneath the Afar Hotspot, the Red Sea, the Gulf of Aden and East of the Tanzania Craton to 400 km depth. High velocities are present in the Eastern Arabia and the Tanzania Craton. The results of this study enable us to rule out a possible feeding of the Central Africa hotspots from the "Afar plume" above 150-200 km. The azimuthal anisotropy displays a complex pattern near the Afar Hotspot. Radial anisotropy, although poorly resolved laterally, exhibits S H slower than S V waves down to about 150 km depth, and a reverse pattern below. Both azimuthal and radial anisotropies show a stratification of anisotropy at depth, corresponding to different physical processes. These results suggest that the Afar hotspot has a different and

  10. Observations on the method of determining the velocity of airships

    NASA Technical Reports Server (NTRS)

    Volterra, Vito

    1921-01-01

    To obtain the absolute velocity of an airship by knowing the speed at which two routes are covered, we have only to determine the geographical direction of the routes which we locate from a map, and the angles of routes as given by the compass, after correcting for the variation (the algebraical sum of the local magnetic declination and the deviation).

  11. SOAP 2.0: A Tool to Estimate the Photometric and Radial Velocity Variations Induced by Stellar Spots and Plages

    NASA Astrophysics Data System (ADS)

    Dumusque, X.; Boisse, I.; Santos, N. C.

    2014-12-01

    This paper presents SOAP 2.0, a new version of the Spot Oscillation And Planet (SOAP) code that estimates in a simple way the photometric and radial velocity (RV) variations induced by active regions. The inhibition of the convective blueshift (CB) inside active regions is considered, as well as the limb brightening effect of plages, a quadratic limb darkening law, and a realistic spot and plage contrast ratio. SOAP 2.0 shows that the activity-induced variation of plages is dominated by the inhibition of the CB effect. For spots, this effect becomes significant only for slow rotators. In addition, in the case of a major active region dominating the activity-induced signal, the ratio between the FWHM and the RV peak-to-peak amplitudes of the cross correlation function can be used to infer the type of active region responsible for the signal for stars with v sin i <=8 km s-1. A ratio smaller than three implies a spot, while a larger ratio implies a plage. Using the observation of HD 189733, we show that SOAP 2.0 manages to reproduce the activity variation as well as previous simulations when a spot is dominating the activity-induced variation. In addition, SOAP 2.0 also reproduces the activity variation induced by a plage on the slowly rotating star α Cen B, which is not possible using previous simulations. Following these results, SOAP 2.0 can be used to estimate the signal induced by spots and plages, but also to correct for it when a major active region is dominating the RV variation. . The work in this paper is based on observations made with the MOST satellite, the HARPS instrument on the ESO 3.6 m telescope at La Silla Observatory (Chile), and the SOPHIE instrument at the Observatoire de Haute Provence (France).

  12. New Insights on Planet Formation in WASP-47 from a Simultaneous Analysis of Radial Velocities and Transit Timing Variations

    NASA Astrophysics Data System (ADS)

    Weiss, Lauren M.; Deck, Katherine M.; Sinukoff, Evan; Petigura, Erik A.; Agol, Eric; Lee, Eve J.; Becker, Juliette C.; Howard, Andrew W.; Isaacson, Howard; Crossfield, Ian J. M.; Fulton, Benjamin J.; Hirsch, Lea; Benneke, Björn

    2017-06-01

    Measuring precise planet masses, densities, and orbital dynamics in individual planetary systems is an important pathway toward understanding planet formation. The WASP-47 system has an unusual architecture that motivates a complex formation theory. The system includes a hot Jupiter (“b”) neighbored by interior (“e”) and exterior (“d”) sub-Neptunes, and a long-period eccentric giant planet (“c”). We simultaneously modeled transit times from the Kepler K2 mission and 118 radial velocities to determine the precise masses, densities, and Keplerian orbital elements of the WASP-47 planets. Combining RVs and TTVs provides a better estimate of the mass of planet d (13.6+/- 2.0 {M}\\oplus ) than that obtained with only RVs (12.75+/- 2.70 {M}\\oplus ) or TTVs (16.1+/- 3.8 {M}\\oplus ). Planets e and d have high densities for their size, consistent with a history of photoevaporation and/or formation in a volatile-poor environment. Through our RV and TTV analysis, we find that the planetary orbits have eccentricities similar to the solar system planets. The WASP-47 system has three similarities to our own solar system: (1) the planetary orbits are nearly circular and coplanar, (2) the planets are not trapped in mean motion resonances, and (3) the planets have diverse compositions. None of the current single-process exoplanet formation theories adequately reproduce these three characteristics of the WASP-47 system (or our solar system). We propose that WASP-47, like the solar system, formed in two stages: first, the giant planets formed in a gas-rich disk and migrated to their present locations, and second, the high-density sub-Neptunes formed in situ in a gas-poor environment.

  13. VizieR Online Data Catalog: M4 Core Project with HST. Radial velocities (Malavolta+, 2015)

    NASA Astrophysics Data System (ADS)

    Malavolta, L.; Piotto, G.; Bedin, L. R.; Sneden, C.; Nascimbeni, V.; Sommariva, V.

    2016-07-01

    The spectra for our project were originally used by Sommariva et al. (2009A&A...493..947S) to study the internal velocity dispersion of M4 and to search for spectroscopic binaries. A total of 2771 stars covering colour-magnitude diagram (CMD) positions from the upper RGB to about 1mag fainter than the main-sequence turnoff (TO) luminosity were observed between 2003 and 2009, including 306 new spectra obtained in 2009 and targeting MS stars already observed in the previous epochs. Determination of the M 4 velocity dispersion and binary star fraction were the prime motivators for obtaining these data. Therefore nearly all stars were observed at least twice, and three or more spectra were obtained for nearly 40 per cent of the sample. (2 data files).

  14. High precision pulsar timing and spin frequency second derivatives

    NASA Astrophysics Data System (ADS)

    Liu, X. J.; Bassa, C. G.; Stappers, B. W.

    2018-05-01

    We investigate the impact of intrinsic, kinematic and gravitational effects on high precision pulsar timing. We present an analytical derivation and a numerical computation of the impact of these effects on the first and second derivative of the pulsar spin frequency. In addition, in the presence of white noise, we derive an expression to determine the expected measurement uncertainty of a second derivative of the spin frequency for a given timing precision, observing cadence and timing baseline and find that it strongly depends on the latter (∝t-7/2). We show that for pulsars with significant proper motion, the spin frequency second derivative is dominated by a term dependent on the radial velocity of the pulsar. Considering the data sets from three Pulsar Timing Arrays, we find that for PSR J0437-4715 a detectable spin frequency second derivative will be present if the absolute value of the radial velocity exceeds 33 km s-1. Similarly, at the current timing precision and cadence, continued timing observations of PSR J1909-3744 for about another eleven years, will allow the measurement of its frequency second derivative and determine the radial velocity with an accuracy better than 14 km s-1. With the ever increasing timing precision and observing baselines, the impact of the, largely unknown, radial velocities of pulsars on high precision pulsar timing can not be neglected.

  15. Radial Diffusion Coefficients Using E and B Field Data from the Van Allen Probes: Comparison with the CRRES Study

    NASA Astrophysics Data System (ADS)

    Ali, A.; Elkington, S. R.; Malaspina, D.

    2014-12-01

    The Van Allen radiation belts contain highly energetic particles which interact with a variety of plasma and MHD waves. Waves with frequencies in the ULF range are understood to play an important role in loss and acceleration of energetic particles. We are investigating the contributions from perturbations in both the magnetic and the electric fields in driving radial diffusion of charged particles and wish to probe two unanswered questions about ULF wave driven radial transport. First, how important are the fluctuations in the magnetic field compared with the fluctuations in the electric field in driving radial diffusion? Second, how does ULF wave power distribution in azimuth affect radial diffusion? Analytic treatments of the diffusion coefficients generally assume uniform distribution of power in azimuth but in situ measurements suggest otherwise. We present results from a study using the electric and magnetic field measurements from the Van Allen Probes to estimate the radial diffusion coefficients as a function of L and Kp. During the lifetime of the RBSP mission to date, there has been a dearth of solar activity. This compels us to consider Kp as the only time and activity dependent parameter instead of solar wind velocity and pressure.

  16. Rayleigh Scattering Diagnostic Used to Measure Velocity and Density Fluctuation Spectra

    NASA Technical Reports Server (NTRS)

    Seasholtz, Richard G.; Panda, Jayanta; Elam, Kristie A.

    2003-01-01

    A new, molecular Rayleigh-scattering-based flow diagnostic developed at the NASA Glenn Research Center has been used for the first time to measure the power spectrum of both gas density and radial velocity components in the plumes of high-speed jets. The objective of the work is to develop an unseeded, nonintrusive dynamic measurement technique for studying turbulent flows in NASA test facilities. This technique provides aerothermodynamic data not previously obtainable. It is particularly important for supersonic flows, where hot wire and pitot probes are difficult to use and disturb the flow under study. The effort is part of the nonintrusive instrumentation development program supporting propulsion research at the NASA Glenn Research Center. In particular, this work is measuring fluctuations in flow velocity, density, and temperature for jet noise studies. These data are valuable to researchers studying the correlation of flow fluctuations with far-field noise. One of the main objectives in jet noise research is to identify noise sources in the jet and to determine their contribution to noise generation. The technique is based on analyzing light scattered from molecules within the jet using a Fabry-Perot interferometer operating in a static imaging mode. The PC-based data acquisition system can simultaneously sample velocity and density data at rates to about 100 kHz and can handle up to 10 million data records. We used this system to interrogate three different jet nozzle designs in a Glenn free-jet facility. Each nozzle had a 25.4-mm exit diameter. One was convergent, used for subsonic flow measurements and to produce a screeching underexpanded jet with a fully expanded Mach number of 1.42. The other nozzles (Mach 1.4 and 1.8) were convergent-divergent types. The radial component of velocity and gas density were simultaneously measured in this work.

  17. Application of a quasi-3D inviscid flow and boundary layer analysis to the hub-shroud contouring of a radial turbine

    NASA Technical Reports Server (NTRS)

    Civinskas, K.; Povinelli, L. A.

    1984-01-01

    Application of a quasi-3D approach to the aerodynamic analysis of several radial turbine configurations is described. The objective was to improve the rotor aerodynamic characteristics by hub-shroud contouring. The approach relies on available 2D inviscid methods coupled with boundary layer analysis to calculate profile, mixing, and endwall losses. Windage, tip clearance, incidence, and secondary flow losses are estimated from correlations. To eliminate separation along the hub and blade suction surfaces of a baseline rotor, the analysis was also applied to three alternate hub-shroud geometries. Emphasis was on elimination of an inducer velocity overshoot as well as increasing hub velocities. While separation was never eliminated, the extent of the separated area was progressively reduced. Results are presented in terms of mid-channel and blade surface velocities; kinetic energy loss coefficients; and efficiency. The calculation demonstrates a first step for a systematic approach to radial turbine design that can be used to identify and control aerodynamic characteristics that ultimately determine heat transfer and component life. Experimentation will be required to assess the extent to which flow and boundary layer behavior were predicted correctly.

  18. Application of a quasi-3D inviscid flow and boundary layer analysis to the hub-shroud contouring of a radial turbine

    NASA Technical Reports Server (NTRS)

    Civinskas, K. C.; Povinelli, L. A.

    1984-01-01

    Application of a quasi-3D approach to the aerodynamic analysis of several radial turbine configurations is described. The objective was to improve the rotor aerodynamic characteristics by hub-shroud contouring. The approach relies on available 2D inviscid methods coupled with boundary layer analysis to calculate profile, mixing, and endwall losses. Windage, tip clearance, incidence, and secondary flow losses are estimated from correlations. To eliminate separation along the hub and blade suction surfaces of a baseline rotor, the analysis was also applied to three alternate hub-shroud geometries. Emphasis was on elimination an inducer velocity overshoot as well as increasing hub velocities. While separation was never eliminated, the extent of the separated area was progressively reduced. Results are presented in terms of mid-channel and blade surface velocities; kinetic energy loss coefficients; and efficiency. The calculation demonstrates a first step for a systematic approach to radial turbine design that can be used to identify and control aerodynamic characteristics that ultimately determine heat transfer and component life. Experimentation will be required to assess the extent to which flow and boundary layer behavior were predicted correctly.

  19. Robustness of Global Radial Anisotropy Models of the Upper Mantle

    NASA Astrophysics Data System (ADS)

    Xing, Z.; Beghein, C.; Yuan, K.

    2014-12-01

    Radial anisotropy provides important constraints on mantle deformation. While its presence is well accepted in the uppermost mantle, large discrepancies remain among existing models, even at depths well sampled by seismic data, and its presence at greater depths is highly uncertain. Surface wave phase velocity dispersion measurements are routinely used to constrain lateral variations in mantle S-wave velocity (dlnVS) and radial anisotropy (ξ=VSH2/VSV2). Here, we employed the fundamental and higher mode surface wave phase velocity maps of Visser et al. (2008) that have unprecedented sensitivity to structure down to 800-1000km depth, and we adopted a probabilistic forward modeling approach, the Neighbourhood Algorithm, to quantify posterior model uncertainties and parameter trade-offs. We investigated the effect of prior crustal corrections on 3-D ξ and dlnVS models. To avoid mapping crustal structure onto mantle heterogeneities, it is indeed important to accurately account for 3-D crustal anomalies and variations in Moho depth. One approach is to solve the non-linear problem and simultaneously constrain Moho depth and mantle anomalies (Visser et al., 2008). Another approach, taken here, is to calculate non-linear crustal corrections with an a priori crustal model, which are then applied to the phase velocity maps before inverting the remaining signal for mantle structure. In this work, we also determined laterally varying sensitivity kernels to account for lateral changes in the crust. We compare models obtained using CRUST2.0 (Bassin et al., 2000) and the new CRUST1.0 (Laske et al., 2012) models, which mostly differ under continents. Our preliminary results show strong differences (ΔdlnVS>2%) between the two models in continental dlnVS for the upper 150-200km, and strong changes in x amplitudes in the top 200km (Δξ>2%). Some of the differences in ξ persist down to the transition zone, in particular beneath central Asia and South America. Despite these

  20. Simulation of radial expansion of an electron beam injected into a background plasma

    NASA Technical Reports Server (NTRS)

    Koga, J.; Lin, C. S.

    1989-01-01

    A 2-D electrostatic particle code was used to study the beam radial expansion of a nonrelativistic electron beam injected from an isolated equipotential conductor into a background plasma. The simulations indicate that the beam radius is generally proportional to the beam electron gyroradius when the conductor is charged to a large potential. The simulations also suggest that the charge buildup at the beam stagnation point causes the beam radial expansion. From a survey of the simulation results, it is found that the ratio of the beam radius to the beam electron gyroradius increases with the square root of beam density and decreases inversely with beam injection velocity. This dependence is explained in terms of the ratio of the beam electron Debye length to the ambient electron Debye length. These results are most applicable to the SEPAC electron beam injection experiments from Spacelab 1, where high charging potential was observed.