目录
图像
上传图像
DSS Images Other Images
相关文章
The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics
Context: Ages, chemical compositions, velocity vectors, and Galacticorbits for stars in the solar neighbourhood are fundamental test datafor models of Galactic evolution. The Geneva-Copenhagen Survey of theSolar Neighbourhood (Nordström et al. 2004; GCS), amagnitude-complete, kinematically unbiased sample of 16 682 nearby F andG dwarfs, is the largest available sample with complete data for starswith ages spanning that of the disk. Aims: We aim to improve theaccuracy of the GCS data by implementing the recent revision of theHipparcos parallaxes. Methods: The new parallaxes yield improvedastrometric distances for 12 506 stars in the GCS. We also use theparallaxes to verify the distance calibration for uvby? photometryby Holmberg et al. (2007, A&A, 475, 519; GCS II). We add newselection criteria to exclude evolved cool stars giving unreliableresults and derive distances for 3580 stars with large parallax errorsor not observed by Hipparcos. We also check the GCS II scales of T_effand [Fe/H] and find no need for change. Results: Introducing thenew distances, we recompute MV for 16 086 stars, and U, V, W,and Galactic orbital parameters for the 13 520 stars that also haveradial-velocity measurements. We also recompute stellar ages from thePadova stellar evolution models used in GCS I-II, using the new valuesof M_V, and compare them with ages from the Yale-Yonsei andVictoria-Regina models. Finally, we compare the observed age-velocityrelation in W with three simulated disk heating scenarios to show thepotential of the data. Conclusions: With these revisions, thebasic data for the GCS stars should now be as reliable as is possiblewith existing techniques. Further improvement must await consolidationof the T_eff scale from angular diameters and fluxes, and the Gaiatrigonometric parallaxes. We discuss the conditions for improvingcomputed stellar ages from new input data, and for distinguishingdifferent disk heating scenarios from data sets of the size andprecision of the GCS.Full Table 1 is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/501/941
| Long-wavelength observations of debris discs around sun-like stars
Context: Tracing the evolution of debris discs is essential for ourunderstanding of the architecture of planetary system. Even though theevolution of their inner discs has been recently studied with theSpitzer Space Telescope at mid- to far-infrared wavelengths, the outerdiscs are best characterised by sensitive millimetre observations. Aims: The goal of our study is to understand the evolution timescaleof circumstellar debris discs, and the physical mechanisms responsiblefor such evolution around solar-type stars. In addition, we make adetailed characterisation of the detected debris discs. Methods:Two deep surveys of circumstellar discs around solar-type stars atdifferent ages were carried out at 350 ?m with the CSO and at 1.2 mmwith the IRAM 30-m telescope. The dust disc masses were computed fromthe millimetre emission, where the discs are optically thin.Theoretically, the mass of the disc is expected to decrease with time.To test this hypothesis, we performed the generalised Kendall's taucorrelation and three different two-sample tests. A characterisation ofthe detected debris discs has been obtained by computing the collisionand Poynting-Robertson timescales and by modelling the spectral energydistribution. Results: The Kendall's tau correlation yields aprobability of 76% that the mass of debris discs and their age arecorrelated. Similarly, the three two-sample tests give a probabilitybetween 70 and 83% that younger and older debris systems belong todifferent parent populations in terms of dust mass. We detectedsubmillimetre/millimetre emission from six debris discs, enabling adetailed SED modelling. Conclusions: Our results on thecorrelation and evolution of dust mass as a function of age areconditioned by the sensitivity limit of our survey. Deeper millimetreobservations are needed to confirm the evolution of debris materialaround solar-like stars. In the case of the detected discs, thecomparison between collision and Poynting-Robertson timescales supportsthe hypothesis that these discs are dominated by collisions. Alldetected debris disc systems show the inner part evacuated from smallmicron-sized grains.This work is based on observations made with the IRAM (Institut deRadioastonomie Millimétrique) 30-m telescope and the CSO (CaltechSubmillimetre Observatory) 10-m telescope. IRAM is supported byINSU/CNRS (France), MPG (Germany), and IGN (Spain).
| Formation and Evolution of Planetary Systems: Properties of Debris Dust Around Solar-Type Stars
We present Spitzer photometric (IRAC and MIPS) and spectroscopic (IRSlow resolution) observations for 314 stars in the Formation andEvolution of Planetary Systems Legacy program. These data are used toinvestigate the properties and evolution of circumstellar dust aroundsolar-type stars spanning ages from approximately 3 Myr-3 Gyr.We identify 46 sources that exhibit excess infrared emission above thestellar photosphere at 24 μm, and 21 sources with excesses at 70μm. Five sources with an infrared excess have characteristics ofoptically thick primordial disks, while the remaining sources haveproperties akin to debris systems. The fraction of systems exhibiting a24 μm excess greater than 10.2% above the photosphere is 15% for ages< 300 Myr and declines to 2.7% for older ages. The upper envelope tothe 70 μm fractional luminosity appears to decline over a similar agerange. The characteristic temperature of the debris inferred from theIRS spectra range between 60 and 180 K, with evidence for the presenceof cooler dust to account for the strength of the 70 μm excessemission. No strong correlation is found between dust temperature andstellar age. Comparison of the observational data with disk modelscontaining a power-law distribution of silicate grains suggests that thetypical inner-disk radius is gsim 10 AU. Although the interpretation isnot unique, the lack of excess emission shortward of 16 μm and therelatively flat distribution of the 24 μm excess for ages lsim 300Myr is consistent with steady-state collisional models.
| The Palomar/Keck Adaptive Optics Survey of Young Solar Analogs: Evidence for a Universal Companion Mass Function
We present results from an adaptive optics survey for substellar andstellar companions to Sun-like stars. The survey targeted 266 F5-K5stars in the 3 Myr-3 Gyr age range with distances of 10-190 pc.Results from the survey include the discovery of two brown dwarfcompanions (HD 49197B and HD 203030B), 24 new stellar binaries, and atriple system. We infer that the frequency of 0.012-0.072Msun brown dwarfs in 28-1590 AU orbits around young solaranalogs is 3.2+3.1 -2.7% (2σ limits).The result demonstrates that the deficiency of substellar companions atwide orbital separations from Sun-like stars is less pronounced than inthe radial velocity "brown dwarf desert." We infer that the massdistribution of companions in 28-1590 AU orbits around solar-mass starsfollows a continuous dN/dM 2 vprop M -0.42 relation over the 0.01-1.0 M sun secondary massrange. While this functional form is similar to that for isolatedobjects less than 0.1 M sun, over the entire 0.01-1.0 Msun range, the mass functions of companions and of isolatedobjects differ significantly. Based on this conclusion and on similarresults from other direct imaging and radial velocity companion surveysin the literature, we argue that the companion mass function follows thesame universal form over the entire range between 0 and 1590 AU inorbital semimajor axis and ≈ 0.01-20 M sun in companionmass. In this context, the relative dearth of substellar versus stellarsecondaries at all orbital separations arises naturally from theinferred form of the companion mass function.
| The Formation and Evolution of Planetary Systems: Description of the Spitzer Legacy Science Database
We present the science database produced by the Formation and Evolutionof Planetary Systems (FEPS) Spitzer Legacy program. Data reduction andvalidation procedures for the IRAC, MIPS, and IRS instruments aredescribed in detail. We also derive stellar properties for the FEPSsample from available broadband photometry and spectral types, andpresent an algorithm to normalize Kurucz synthetic spectra to opticaland near-infrared photometry. The final FEPS data products include IRACand MIPS photometry for each star in the FEPS sample and calibrated IRSspectra.
| The Complete Census of 70 μm-bright Debris Disks within ``the Formation and Evolution of Planetary Systems'' Spitzer Legacy Survey of Sun-like Stars
We report detection of cool dust surrounding solar-type stars fromobservations performed as part of the Spitzer Legacy Science ProgramFEPS. From a sample of 328 stars having ages ~0.003-3 Gyr we haveselected sources with 70 μm flux densities indicating excess in theirSEDs above expected photospheric emission. Six strong excess sources arelikely primordial circumstellar disks, remnants of the star formationprocess. Another 25 sources having >=3 σ excesses areassociated with dusty debris disks, generated by collisions withinplanetesimal belts that are possibly stirred by existing planets. Sixadditional sources with >=2 σ excesses require confirmation asdebris disks. In our analysis, most (>80%) 70 μm excess sourceshave >=3 σ excesses at 33 μm as well, while only a minority(<40%) have >=3 σ excesses at 24 μm. The rising SEDstoward (and perhaps beyond) 70 μm imply dust temperatures <45-85 Kfor debris in equilibrium with the stellar radiation field. From fittedsingle-temperature blackbody models we infer bulk dust properties suchas characteristic temperature, location, fractional luminosity, andmass. For >1/3 of the debris sources we find that multipletemperature components are suggested, implying a dust distributionextending over many tens of AU. Because the disks are dominated bycollisional processes, the parent body (planetesimal) belts may beextended as well. Preliminary assessment of the statistics of colddebris around Sun-like stars shows that ~10% of FEPS targets with massesbetween 0.6 and 1.8 Msolar and ages between 30 Myr and 3 Gyrexhibit excess 70 μm emission. We find that fractional excessamplitudes appear higher for younger stars and that there may be a trendin 70 μm excess frequency with stellar mass.
| Evolution of Mid-Infrared Excess around Sun-like Stars: Constraints on Models of Terrestrial Planet Formation
We report observations from the Spitzer Space Telescope regarding thefrequency of 24 μm excess emission toward Sun-like stars. Ourunbiased sample is composed of 309 stars with masses 0.7-2.2Msolar and ages from <3 Myr to >3 Gyr that lack excessemission at wavelengths <=8 μm. We identify 30 stars that exhibitclear evidence of excess emission from the observed 24 μm/8 μmflux ratio. The implied 24 μm excesses of these candidate debris disksystems range from 13% (the minimum detectable) to more than 100%compared to the expected photospheric emission. The frequency of systemswith evidence for dust debris emitting at 24 μm ranges from 8.5%-19%at ages <300 Myr to <4% for older stars. The results suggest thatmany, perhaps most, Sun-like stars might form terrestrial planets.
| High-Dispersion Optical Spectra of Nearby Stars Younger Than the Sun
We present high-dispersion (R~16,000) optical (3900-8700 Å)spectra of 390 stars obtained with the Palomar 60 inch telescope. Themajority of stars observed are part of the Spitzer Legacy ScienceProgram ``The Formation and Evolution of Planetary Systems.'' Throughdetailed analysis we determine stellar properties for this sample,including radial and rotational velocities, Li I λ6708 andHα equivalent widths, the chromospheric activity indexR'HK, and temperature- and gravity-sensitive lineratios. Several spectroscopic binaries are also identified. From ourtabulations, we illustrate basic age- and rotation-related correlationsamong measured indices. One novel result is that Ca II chromosphericemission appears to saturate at vsini values above ~30 kms-1, similar to the well-established saturation of X-raysthat originate in the spatially separate coronal region.
| The N2K Consortium. VII. Atmospheric Parameters of 1907 Metal-rich Stars: Finding Planet-Search Targets
We report high-precision atmospheric parameters for 1907 stars in theN2K low-resolution spectroscopic survey, designed to identify metal-richFGK dwarfs likely to harbor detectable planets. Of these stars, 284 arein the ideal temperature range for planet searches,Teff<=6000 K, and have a 10% or greater probability ofhosting planets based on their metallicities. The stars in thelow-resolution spectroscopic survey should eventually yield >60 newplanets, including 8-9 hot Jupiters. Short-period planets have alreadybeen discovered orbiting the survey targets HIP 14810 and HD 149143.
| Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog
We derive detailed theoretical models for 1074 nearby stars from theSPOCS (Spectroscopic Properties of Cool Stars) Catalog. The Californiaand Carnegie Planet Search has obtained high-quality (R~=70,000-90,000,S/N~=300-500) echelle spectra of over 1000 nearby stars taken with theHamilton spectrograph at Lick Observatory, the HIRES spectrograph atKeck, and UCLES at the Anglo Australian Observatory. A uniform analysisof the high-resolution spectra has yielded precise stellar parameters(Teff, logg, vsini, [M/H], and individual elementalabundances for Fe, Ni, Si, Na, and Ti), enabling systematic erroranalyses and accurate theoretical stellar modeling. We have created alarge database of theoretical stellar evolution tracks using the YaleStellar Evolution Code (YREC) to match the observed parameters of theSPOCS stars. Our very dense grids of evolutionary tracks eliminate theneed for interpolation between stellar evolutionary tracks and allowprecise determinations of physical stellar parameters (mass, age,radius, size and mass of the convective zone, surface gravity, etc.).Combining our stellar models with the observed stellar atmosphericparameters and uncertainties, we compute the likelihood for each set ofstellar model parameters separated by uniform time steps along thestellar evolutionary tracks. The computed likelihoods are used for aBayesian analysis to derive posterior probability distribution functionsfor the physical stellar parameters of interest. We provide a catalog ofphysical parameters for 1074 stars that are based on a uniform set ofhigh-quality spectral observations, a uniform spectral reductionprocedure, and a uniform set of stellar evolutionary models. We explorethis catalog for various possible correlations between stellar andplanetary properties, which may help constrain the formation anddynamical histories of other planetary systems.
| The Formation and Evolution of Planetary Systems: Placing Our Solar System in Context with Spitzer
We provide an overview of the Spitzer Legacy Program, Formation andEvolution of Planetary Systems, that was proposed in 2000, begun in2001, and executed aboard the Spitzer Space Telescope between 2003 and2006. This program exploits the sensitivity of Spitzer to carry outmid-infrared spectrophotometric observations of solar-type stars. With asample of ~328 stars ranging in age from ~3 Myr to ~3 Gyr, we trace theevolution of circumstellar gas and dust from primordial planet-buildingstages in young circumstellar disks through to older collisionallygenerated debris disks. When completed, our program will help define thetimescales over which terrestrial and gas giant planets are built,constrain the frequency of planetesimal collisions as a function oftime, and establish the diversity of mature planetary architectures. Inaddition to the observational program, we have coordinated a concomitanttheoretical effort aimed at understanding the dynamics of circumstellardust with and without the effects of embedded planets, dust spectralenergy distributions, and atomic and molecular gas line emission.Together with the observations, these efforts will provide anastronomical context for understanding whether our solar system-and itshabitable planet-is a common or a rare circumstance. Additionalinformation about the FEPS project can be found on the team Web site.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs
We present a uniform catalog of stellar properties for 1040 nearby F, G,and K stars that have been observed by the Keck, Lick, and AAT planetsearch programs. Fitting observed echelle spectra with synthetic spectrayielded effective temperature, surface gravity, metallicity, projectedrotational velocity, and abundances of the elements Na, Si, Ti, Fe, andNi, for every star in the catalog. Combining V-band photometry andHipparcos parallaxes with a bolometric correction based on thespectroscopic results yielded stellar luminosity, radius, and mass.Interpolating Yonsei-Yale isochrones to the luminosity, effectivetemperature, metallicity, and α-element enhancement of each staryielded a theoretical mass, radius, gravity, and age range for moststars in the catalog. Automated tools provide uniform results and makeanalysis of such a large sample practical. Our analysis method differsfrom traditional abundance analyses in that we fit the observed spectrumdirectly, rather than trying to match equivalent widths, and wedetermine effective temperature and surface gravity from the spectrumitself, rather than adopting values based on measured photometry orparallax. As part of our analysis, we determined a new relationshipbetween macroturbulence and effective temperature on the main sequence.Detailed error analysis revealed small systematic offsets with respectto the Sun and spurious abundance trends as a function of effectivetemperature that would be inobvious in smaller samples. We attempted toremove these errors by applying empirical corrections, achieving aprecision per spectrum of 44 K in effective temperature, 0.03 dex inmetallicity, 0.06 dex in the logarithm of gravity, and 0.5 kms-1 in projected rotational velocity. Comparisons withprevious studies show only small discrepancies. Our spectroscopicallydetermined masses have a median fractional precision of 15%, but theyare systematically 10% higher than masses obtained by interpolatingisochrones. Our spectroscopic radii have a median fractional precisionof 3%. Our ages from isochrones have a precision that variesdramatically with location in the Hertzsprung-Russell diagram. We planto extend the catalog by applying our automated analysis technique toother large stellar samples.
| A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)
The LSPM catalog is a comprehensive list of 61,977 stars north of theJ2000 celestial equator that have proper motions larger than 0.15"yr-1 (local-background-stars frame). The catalog has beengenerated primarily as a result of our systematic search for high propermotion stars in the Digitized Sky Surveys using our SUPERBLINK software.At brighter magnitudes, the catalog incorporates stars and data from theTycho-2 Catalogue and also, to a lesser extent, from the All-SkyCompiled Catalogue of 2.5 million stars. The LSPM catalog considerablyexpands over the old Luyten (Luyten Half-Second [LHS] and New LuytenTwo-Tenths [NLTT]) catalogs, superseding them for northern declinations.Positions are given with an accuracy of <~100 mas at the 2000.0epoch, and absolute proper motions are given with an accuracy of ~8 masyr-1. Corrections to the local-background-stars propermotions have been calculated, and absolute proper motions in theextragalactic frame are given. Whenever available, we also give opticalBT and VT magnitudes (from Tycho-2, ASCC-2.5),photographic BJ, RF, and IN magnitudes(from USNO-B1 catalog), and infrared J, H, and Ks magnitudes(from 2MASS). We also provide an estimated V magnitude and V-J color fornearly all catalog entries, useful for initial classification of thestars. The catalog is estimated to be over 99% complete at high Galacticlatitudes (|b|>15deg) and over 90% complete at lowGalactic latitudes (|b|>15deg), down to a magnitudeV=19.0, and has a limiting magnitude V=21.0. All the northern starslisted in the LHS and NLTT catalogs have been reidentified, and theirpositions, proper motions, and magnitudes reevaluated. The catalog alsolists a large number of completely new objects, which promise to expandvery significantly the census of red dwarfs, subdwarfs, and white dwarfsin the vicinity of the Sun.Based on data mining of the Digitized Sky Surveys (DSSs), developed andoperated by the Catalogs and Surveys Branch of the Space TelescopeScience Institute (STScI), Baltimore.Developed with support from the National Science Foundation (NSF), aspart of the NASA/NSF NStars program.
| Chromospheric Ca II Emission in Nearby F, G, K, and M Stars
We present chromospheric Ca II H and K activity measurements, rotationperiods, and ages for ~1200 F, G, K, and M type main-sequence stars from~18,000 archival spectra taken at Keck and Lick Observatories as a partof the California and Carnegie Planet Search Project. We have calibratedour chromospheric S-values against the Mount Wilson chromosphericactivity data. From these measurements we have calculated medianactivity levels and derived R'HK, stellar ages,and rotation periods from general parameterizations for 1228 stars,~1000 of which have no previously published S-values. We also presentprecise time series of activity measurements for these stars.Based on observations obtained at Lick Observatory, which is operated bythe University of California, and on observations obtained at the W. M.Keck Observatory, which is operated jointly by the University ofCalifornia and the California Institute of Technology. The KeckObservatory was made possible by the generous financial support of theW. M. Keck Foundation.
| The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of 14 000 F and G dwarfs
We present and discuss new determinations of metallicity, rotation, age,kinematics, and Galactic orbits for a complete, magnitude-limited, andkinematically unbiased sample of 16 682 nearby F and G dwarf stars. Our63 000 new, accurate radial-velocity observations for nearly 13 500stars allow identification of most of the binary stars in the sampleand, together with published uvbyβ photometry, Hipparcosparallaxes, Tycho-2 proper motions, and a few earlier radial velocities,complete the kinematic information for 14 139 stars. These high-qualityvelocity data are supplemented by effective temperatures andmetallicities newly derived from recent and/or revised calibrations. Theremaining stars either lack Hipparcos data or have fast rotation. Amajor effort has been devoted to the determination of new isochrone agesfor all stars for which this is possible. Particular attention has beengiven to a realistic treatment of statistical biases and errorestimates, as standard techniques tend to underestimate these effectsand introduce spurious features in the age distributions. Our ages agreewell with those by Edvardsson et al. (\cite{edv93}), despite severalastrophysical and computational improvements since then. We demonstrate,however, how strong observational and theoretical biases cause thedistribution of the observed ages to be very different from that of thetrue age distribution of the sample. Among the many basic relations ofthe Galactic disk that can be reinvestigated from the data presentedhere, we revisit the metallicity distribution of the G dwarfs and theage-metallicity, age-velocity, and metallicity-velocity relations of theSolar neighbourhood. Our first results confirm the lack of metal-poor Gdwarfs relative to closed-box model predictions (the ``G dwarfproblem''), the existence of radial metallicity gradients in the disk,the small change in mean metallicity of the thin disk since itsformation and the substantial scatter in metallicity at all ages, andthe continuing kinematic heating of the thin disk with an efficiencyconsistent with that expected for a combination of spiral arms and giantmolecular clouds. Distinct features in the distribution of the Vcomponent of the space motion are extended in age and metallicity,corresponding to the effects of stochastic spiral waves rather thanclassical moving groups, and may complicate the identification ofthick-disk stars from kinematic criteria. More advanced analyses of thisrich material will require careful simulations of the selection criteriafor the sample and the distribution of observational errors.Based on observations made with the Danish 1.5-m telescope at ESO, LaSilla, Chile, and with the Swiss 1-m telescope at Observatoire deHaute-Provence, France.Complete Tables 1 and 2 are only available in electronic form at the CDSvia anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/418/989
| Improved Astrometry and Photometry for the Luyten Catalog. II. Faint Stars and the Revised Catalog
We complete construction of a catalog containing improved astrometry andnew optical/infrared photometry for the vast majority of NLTT starslying in the overlap of regions covered by POSS I and by the secondincremental Two Micron All Sky Survey (2MASS) release, approximately 44%of the sky. The epoch 2000 positions are typically accurate to 130 mas,the proper motions to 5.5 mas yr-1, and the V-J colors to0.25 mag. Relative proper motions of binary components are measured to 3mas yr-1. The false-identification rate is ~1% for11<~V<~18 and substantially less at brighter magnitudes. Theseimprovements permit the construction of a reduced proper-motion diagramthat, for the first time, allows one to classify NLTT stars intomain-sequence (MS) stars, subdwarfs (SDs), and white dwarfs (WDs). We inturn use this diagram to analyze the properties of both our catalog andthe NLTT catalog on which it is based. In sharp contrast to popularbelief, we find that NLTT incompleteness in the plane is almostcompletely concentrated in MS stars, and that SDs and WDs are detectedalmost uniformly over the sky δ>-33deg. Our catalogwill therefore provide a powerful tool to probe these populationsstatistically, as well as to reliably identify individual SDs and WDs.
| Late-type members of young stellar kinematic groups - I. Single stars
This is the first paper of a series aimed at studying the properties oflate-type members of young stellar kinematic groups. We concentrate ourstudy on classical young moving groups such as the Local Association(Pleiades moving group, 20-150Myr), IC 2391 supercluster (35Myr), UrsaMajor group (Sirius supercluster, 300Myr), and Hyades supercluster(600Myr), as well as on recently identified groups such as the Castormoving group (200Myr). In this paper we compile a preliminary list ofsingle late-type possible members of some of these young stellarkinematic groups. Stars are selected from previously established membersof stellar kinematic groups based on photometric and kinematicproperties as well as from candidates based on other criteria such astheir level of chromospheric activity, rotation rate and lithiumabundance. Precise measurements of proper motions and parallaxes takenfrom the Hipparcos Catalogue, as well as from the Tycho-2 Catalogue, andpublished radial velocity measurements are used to calculate theGalactic space motions (U, V, W) and to apply Eggen's kinematic criteriain order to determine the membership of the selected stars to thedifferent groups. Additional criteria using age-dating methods forlate-type stars will be applied in forthcoming papers of this series. Afurther study of the list of stars compiled here could lead to a betterunderstanding of the chromospheric activity and their age evolution, aswell as of the star formation history in the solar neighbourhood. Inaddition, these stars are also potential search targets for directimaging detection of substellar companions.
| The Vienna-KPNO search for Doppler-imaging candidate stars. I. A catalog of stellar-activity indicators for 1058 late-type Hipparcos stars
We present the results from a spectroscopic Ca ii H&K survey of 1058late-type stars selected from a color-limited subsample of the Hipparcoscatalog. Out of these 1058 stars, 371 stars were found to showsignificant H&K emission, most of them previously unknown; 23% withstrong emission, 36% with moderate emission, and 41% with weak emission.These spectra are used to determine absolute H&K emission-linefluxes, radial velocities, and equivalent widths of theluminosity-sensitive Sr ii line at 4077 Ä. Red-wavelengthspectroscopic and Strömgren y photometric follow-up observations ofthe 371 stars with H&K emission are used to additionally determinethe absolute Hα -core flux, the lithium abundance from the Li i6708 Å equivalent width, the rotational velocity vsin i, theradial velocity, and the light variations and its periodicity. Thelatter is interpreted as the stellar rotation period due to aninhomogeneous surface brightness distribution. 156 stars were found withphotometric periods between 0.29 and 64 days, 11 additional systemsshowed quasi-periodic variations possibly in excess of ~50 days. Further54 stars had variations but no unique period was found, and four starswere essentially constant. Altogether, 170 new variable stars werediscovered. Additionally, we found 17 new SB1 (plus 16 new candidates)and 19 new SB2 systems, as well as one definite and two possible new SB3systems. Finally, we present a list of 21 stars that we think are mostsuitable candidates for a detailed study with the Doppler-imagingtechnique. Tables A1--A3 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Mesures de vitesses radiales. VII. Accompagnement AU sol DU programme d'observation DU satellite Hipparcos. Radial velocities. VII. Ground based measurements for Hipparcos.
We publish 734 radial velocities of stars distributed in 28 fields of4x4deg. We continue the PPO series (Fehrenbach et al. 1987; Duflot etal. 1990 and 1992), using the Fehrenbach objective prism method.
|
提交文章
相关链接
提交链接
下列团体成员
|
观测天体数据
目录:
|
INHABITED SKY
