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The Initial-Final Mass Relation among White Dwarfs in Wide Binaries
We present the initial-final mass relation derived from 10 white dwarfsin wide binaries that consist of a main-sequence star and a white dwarf.The temperature and gravity of each white dwarf were measured by fittingtheoretical model atmospheres to the observed spectrum using aχ2 fitting algorithm. The cooling time and mass wereobtained using theoretical cooling tracks. The total age of each binarywas estimated from the chromospheric activity of its main-sequencecomponent to an uncertainty of about 0.17 dex in log t. The differencebetween the total age and white dwarf cooling time is taken as themain-sequence lifetime of each white dwarf. The initial mass of eachwhite dwarf was then determined using stellar evolution tracks with acorresponding metallicity derived from spectra of their main-sequencecompanions, thus yielding the initial-final mass relation. Most of theinitial masses of the white dwarf components are between 1 and 2 M&sun;. Our results suggest a correlation between themetallicity of a white dwarf's progenitor and the amount ofpost-main-sequence mass loss it experiences—at least amongprogenitors with masses in the range of 1-2 M &sun;. Acomparison of our observations to theoretical models suggests thatlow-mass stars preferentially lose mass on the red giant branch.
| Toward Precise Ages for Single Stars in the Field. Gyrochronology Constraints at Several Gyr Using Wide Binaries. I. Ages for Initial Sample
We present a program designed to obtain age-rotation measurements ofsolar-type dwarfs to be used in the calibration of gyrochronologyrelations at ages of several Gyr. This is a region of parameter spacecrucial for the large-scale study of the Milky Way, and where the onlyconstraint available today is that provided by the Sun. Our programtakes advantage of a set of wide binaries selected so that one componentis an evolved star and the other is a main-sequence star of FGK type. Inthis way, we obtain the age of the system from the evolved star, whilethe rotational properties of the main-sequence component provide theinformation relevant for gyrochronology regarding the spin-down ofsolar-type stars. By mining currently available catalogs of widebinaries, we assemble a sample of 37 pairs well positioned for ourpurposes: 19 with turnoff or subgiant primaries and 18 with white dwarfcomponents. Using high-resolution optical spectroscopy, we measureprecise stellar parameters for a subset of 15 of the pairs withturnoff/subgiant components and use these to derive isochronal ages forthe corresponding systems. Ages for 16 of the 18 pairs with white dwarfcomponents are taken from the literature. The ages of this initialsample of 31 wide binaries range from 1 to 9 Gyr, with precisions betterthan ~20% for almost half of these systems. When combined withmeasurements of the rotation period of their main-sequence components,these wide binary systems would potentially provide a similar number ofpoints useful for the calibration of gyrochronology relations at veryold ages.
| Time evolution of high-energy emissions of low-mass stars. I. Age determination using stellar chronology with white dwarfs in wide binaries
Context. Stellar ages are extremely difficult to determine and oftensubject to large uncertainties, especially for field low-mass stars. Weplan to carry out a calibration of the decrease in high-energy emissionsof low-mass GKM stars with time, and therefore precise age determinationis a key ingredient. The overall goal of our research is to study thetime evolution of these high-energy emissions as an essential input tostudying exoplanetary atmospheres. Aims: We propose to determinestellar ages with a methodology based on wide binaries. We areinterested in systems composed of a low-mass star and a white dwarf(WD), where the latter serves as a stellar chronometer for the system.We aim at obtaining reliable ages for a sample of late-type stars olderthan 1 Gyr. Methods: We selected a sample of wide binariescomposed by a DA type WD and a GKM companion. High signal-to-noise,low-resolution spectroscopic observations were obtained for most of theWD members of the sample. Atmospheric parameters were determined byfitting the spectroscopic data to appropiate WD models. The total agesof the systems were derived by using cooling sequences, an initial-finalmass relationship and evolutionary tracks, to account for the progenitorlife. Results: The spectroscopic observations have allowed us todetermine ages for the binary systems using WDs as cosmochronometers. Weobtained reliable ages for 27 stars between 1 and 5 Gyr, which is arange where age determination becomes difficult for field objects.Roughly half of these systems have cooling ages that contribute at least30% the total age. We select those for further study since their ageestimate should be less prone to systematic errors coming from theinitial-final mass relationship. Conclusions: We have determinedrobust ages for a sizeable sample of GKM stars that can be subsequentlyused to study the time evolution of their emissions associated tostellar magnetic activity.Based on observations collected at the Centro Astronómico HispanoAlemán (CAHA) at Calar Alto, operated jointly by the Max-PlanckInstitut für Astronomie and the Instituto de Astrofísica deAndalucía (CSIC).Based on observations made with the WHT (WilliamHerschel Telescope) operated on the island of La Palma by the IsaacNewton Group in the Spanish Observatorio del Roque de los Muchachos ofthe Instituto de Astrofísica de Canarias.
| The Chromospheric Activity, Age, Metallicity, and Space Motions of 36 Wide Binaries
We present the chromospheric activity (CA) levels, metallicities, andfull space motions for 41 F, G, K, and M dwarf stars in 36 wide binarysystems. Thirty-one of the binaries contain a white dwarf (WD)component. In such binaries, the total age can be estimated by addingthe cooling age of the WD to an estimate of the progenitor'smain-sequence lifetime. To better understand how CA correlates tostellar age, 14 cluster member stars were also observed. Ourobservations demonstrate for the first time that, in general, CA decayswith age from 50 Myr to at least 8 Gyr for stars with 1.0 <= V - I<= 2.4. However, little change occurs in the CA level for stars withV - I < 1.0 between 1 Gyr and 5 Gyr, consistent with the results ofPace et al. Our sample also exhibits a negative correlation between thestellar age and metallicity, a positive correlation between the stellarage and W space velocity component, and the W velocity dispersionincreases with age. Finally, the population membership of these widebinaries is examined based upon their U, V, W kinematics, metallicity,and CA. We conclude that wide binaries are similar to field and clusterstars in these respects. More importantly, they span a much morecontinuous range in age and metallicity than is afforded by nearbyclusters.
| Bayesian inference of stellar parameters and interstellar extinction using parallaxes and multiband photometry
Astrometric surveys provide the opportunity to measure the absolutemagnitudes of large numbers of stars, but only if the individualline-of-sight extinctions are known. Unfortunately, extinction is highlydegenerate with stellar effective temperature when estimated frombroad-band optical/infrared photometry. To address this problem, Iintroduce a Bayesian method for estimating the intrinsic parameters of astar and its line-of-sight extinction. It uses both photometry andparallaxes in a self-consistent manner in order to provide anon-parametric posterior probability distribution over the parameters.The method makes explicit use of domain knowledge by employing theHertzsprung-Russell Diagram (HRD) to constrain solutions and to ensurethat they respect stellar physics. I first demonstrate this method byusing it to estimate effective temperature and extinction from BVJHKdata for a set of artificially reddened Hipparcos stars, for whichaccurate effective temperatures have been estimated from high-resolutionspectroscopy. Using just the four colours, we see the expected strongdegeneracy (positive correlation) between the temperature andextinction. Introducing the parallax, apparent magnitude and the HRDreduces this degeneracy and improves both the precision (reduces theerror bars) and the accuracy of the parameter estimates, the latter byabout 35 per cent. The resulting accuracy is about 200 K in temperatureand 0.2 mag in extinction. I then apply the method to estimate theseparameters and absolute magnitudes for some 47 000 F, G, K Hipparcosstars which have been cross-matched with Two-Micron All-Sky Survey(2MASS). The method can easily be extended to incorporate the estimationof other parameters, in particular metallicity and surface gravity,making it particularly suitable for the analysis of the 109stars from Gaia.
| New Distant Companions to Known Nearby Stars. II. Faint Companions of Hipparcos Stars and the Frequency of Wide Binary Systems
We perform a search for faint, common proper motion companions ofHipparcos stars using the recently published Lépine-Shara ProperMotion-North catalog of stars with proper motionμ>0.15'' yr-1. Our survey uncovers a totalof 521 systems with angular separations3''<Δθ<1500'', with 15 triplesand 1 quadruple. Our new list of wide systems with Hipparcos primariesincludes 130 systems identified here for the first time, including 44 inwhich the secondary star has V>15.0. Our census is statisticallycomplete for secondaries with angular separations20''<Δθ<300'' and apparentmagnitudes V<19.0. Overall, we find that at least 9.5% of nearby(d<100 pc) Hipparcos stars have distant stellar companions withprojected orbital separations s>1000 AU. We observe that thedistribution in orbital separations is consistent with Öpik's law,f(s)ds~s-1ds, only up to a separation s~4000 AU, beyond whichit follows a more steeply decreasing power law f(s)ds~s-ldswith l=1.6+/-0.1. We also find that the luminosity function of thesecondaries is significantly different from that of the single stars'field population, showing a relative deficiency in low-luminosity(8
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| 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.
| Completeness of USNO-B for High Proper Motion Stars
I test the completeness of USNO-B detections of high proper motion(μ>180 mas yr-1) stars and the accuracy of itsmeasurements by comparing them to the revised New Luyten Two-Tenthscatalog of Salim & Gould. For 14.5~20 mas yr-1) may actuallyhave still larger errors than tabulated.
| 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.
| A Survey of Proper-Motion Stars. XVI. Orbital Solutions for 171 Single-lined Spectroscopic Binaries
We report 25,563 radial velocity measurements for 1359 single-linedstars in the Carney-Latham sample of 1464 stars selected for high propermotion. For 171 of these, we present spectroscopic orbital solutions. Wefind no obvious difference between the binary characteristics in thehalo and the disk populations. The observed frequency is the same, andthe period distributions are consistent with the hypothesis that the twosets of binaries were drawn from the same parent population. Thissuggests that metallicity in general, and radiative opacities inparticular, have little influence over the fragmentation process thatleads to short-period binaries. All the binaries with periods shorterthan 10 days have nearly circular orbits, while the binaries withperiods longer than 20 days exhibit a wide range of eccentricities and amedian value of 0.37. For the metal-poor high-velocity halo binaries inour sample, the transition from circular to eccentric orbits appears tooccur at about 20 days, supporting the conclusion that tidalcircularization on the main sequence is important for the oldestbinaries in the Galaxy. Some of the results presented here usedobservations made with the Multiple Mirror Telescope, a joint facilityof the Smithsonian Institution and the University of Arizona.
| A survey of proper motion stars. 12: an expanded sample
We report new photometry and radial velocities for almost 500 stars fromthe Lowell Proper Motion Catalog. We combine these results with ourprior sample and rederive stellar temperatures based on the photometry,reddening, metallicities (using chi squared matching of our 22,500 lowSignal to Noise (S/N) high resolution echelle spectra with a grid ofsynthetic spectra), distances, space motions, and Galactic orbitalparameters for 1269 (kinematics) and 1261 (metallicity) of the 1464stars in the complete survey. The frequency of spectroscopic binariesfor the metal-poor ((m/H) less than or equal to -1.2) stars with periodsshorter than 3000 days is at least 15%. The spectroscopic binaryfrequency for metal-rich stars ((m/H) greater than -0.5) appears to belower, about 9%, but this may be a selection effect. We also discussspecial classes of stars, including treatment of the double-linedspectroscopic binaries, and identification of subgiants. Four possiblenew members of the class of field blue stragglers are noted. We pointout the detection of three possible new white dwarfs, six broad-lined(binary) systems, and discuss briefly the three already knownnitrogen-rich halo dwarfs. The primary result of this paper will beavailable on CD-ROM, in the form of a much larger table.
| A survey of proper motion stars. IX - The galactic halo's metallicity gradient
Using data already presented for a survey of proper motion stars and theBahcall, Schmidt, and Soneira (1983) model of the Galaxy, Galacticorbital parameters are computed, including planar and three-dimensionaleccentricities, apo- and perigalacticon distances, and maximum distancesreached above/below the plane, based on extreme values for R and theabsolute value of Z over 15 azimuthal periods. The orbital data are usedto bin the survey's stars by apogalacticon and maximum Z distances. Inan attempt to isolate a halo population sample, analyses are restrictedto those stars that lag behind the local standard of the rest's circularorbital velocity by 50, 100, 150, and 200 km/s. The mean metallicitiesof the stars in a variety of Rapo and Zmax bins are compared .
| UBVRI photoelectric photometry of high proper motion stars
UBVRI photoelectric photometry is presented for 269 late spectral type,high proper motion stars belonging to the 'Lowell Proper Motion Survey'and included in the present version of the Hipparcos Input Catalogue.The observations and data reduction are described. The external errorsobtained by comparison of the results with those obtained in otherstudies are presented.
| A survey of proper-motion stars. III - Reddenings, distances, and metallicities
Further data on the Lowell proper-motion stars surveyed by Carney andLatham (1987) are presented. Both new and published photometry aresummarized for 286 of these stars. Included are R-I data for 64 stars,uvby (or by) data for 221 stars (of which are included new results for152 stars), and JHK (or K) data for 238 stars (of which are included newresults for 180 stars). The procedures used to estimate the reddeningand photometric parallax of each star are discussed. The metallicitiesfor 818 stars, based on 5795 spectra, determined using a new method,described in an earlier paper, which compares synthetic spectra to thelow-signal-to-noise spectra obtained for radial velocities are alsopresented. The reddening, distance, and metallicity are interdependentand have been determined in a self-consistent manner.
| A survey of proper-motion stars. I - UBV photometry and radial velocities
The background, motivation, and goals of a photometric and spectroscopicsurvey of over 900 stars selected from the Lowell Proper Motion Surveywithout any metallicity bias are discussed, and 1225 new UBV measures of867 stars with V = 7-16 mag, and a new mean radial velocities for 914stars based on 5815 high-resolution spectra are presented. Theradial-velocity data indicate the binary fraction of th high-velocitystars probably exceeds 25 percent.
| Spectral classification of high-proper-motion stars
Spectral types have been found for about 900 stars of high proper motioncontained in the Lowell Observatory Northern Hemisphere proper-motionstar survey using all blue-region objective prism plates. The spectralclassification criteria are given. About eighty stars of largetangential velocity have been classified using slit spectrograms takenwith a 36-in. reflector. A new calibration of Luyten's absolutemagnitude vs reduced proper motion relation is made, and its dependenceon spectral type is investigated.
| Emission-Line Stars Associated with the Nebulous Cluster NGC 2264.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1954ApJ...119..483H&db_key=AST
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