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מאמרים קשורים
Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants
We present the parameters of 891 stars, mostly clump giants, includingatmospheric parameters, distances, absolute magnitudes, spatialvelocities, galactic orbits and ages. One part of this sample consistsof local giants, within 100 pc, with atmospheric parameters eitherestimated from our spectroscopic observations at high resolution andhigh signal-to-noise ratio, or retrieved from the literature. The otherpart of the sample includes 523 distant stars, spanning distances up to1 kpc in the direction of the North Galactic Pole, for which we haveestimated atmospheric parameters from high resolution but lowsignal-to-noise Echelle spectra. This new sample is kinematicallyunbiased, with well-defined boundaries in magnitude and colours. Werevisit the basic properties of the Galactic thin disk as traced byclump giants. We find the metallicity distribution to be different fromthat of dwarfs, with fewer metal-rich stars. We find evidence for avertical metallicity gradient of -0.31 dex kpc-1 and for atransition at ~4-5 Gyr in both the metallicity and velocities. Theage-metallicity relation (AMR), which exhibits a very low dispersion,increases smoothly from 10 to 4 Gyr, with a steeper increase for youngerstars. The age-velocity relation (AVR) is characterized by thesaturation of the V and W dispersions at 5 Gyr, and continuous heatingin U.
| Pulkovo compilation of radial velocities for 35495 stars in a common system.
Not Available
| Can Life Develop in the Expanded Habitable Zones around Red Giant Stars?
We present some new ideas about the possibility of life developingaround subgiant and red giant stars. Our study concerns the temporalevolution of the habitable zone. The distance between the star and thehabitable zone, as well as its width, increases with time as aconsequence of stellar evolution. The habitable zone moves outward afterthe star leaves the main sequence, sweeping a wider range of distancesfrom the star until the star reaches the tip of the asymptotic giantbranch. Currently there is no clear evidence as to when life actuallyformed on the Earth, but recent isotopic data suggest life existed atleast as early as 7×108 yr after the Earth was formed.Thus, if life could form and evolve over time intervals from5×108 to 109 yr, then there could behabitable planets with life around red giant stars. For a 1Msolar star at the first stages of its post-main-sequenceevolution, the temporal transit of the habitable zone is estimated to beseveral times 109 yr at 2 AU and around 108 yr at9 AU. Under these circumstances life could develop at distances in therange 2-9 AU in the environment of subgiant or giant stars, and in thefar distant future in the environment of our own solar system. After astar completes its first ascent along the red giant branch and the Heflash takes place, there is an additional stable period of quiescent Hecore burning during which there is another opportunity for life todevelop. For a 1 Msolar star there is an additional109 yr with a stable habitable zone in the region from 7 to22 AU. Space astronomy missions, such as proposed for the TerrestrialPlanet Finder (TPF) and Darwin, that focus on searches for signatures oflife on extrasolar planets, should also consider the environments ofsubgiants and red giant stars as potentially interesting sites forunderstanding the development of life. We performed a preliminaryevaluation of the difficulty of interferometric observations of planetsaround red giant stars compared to a main-sequence star environment. Weshow that pathfinder missions for TPF and Darwin, such as Eclipse andFKSI, have sufficient angular resolution and sensitivity to search forhabitable planets around some of the closest evolved stars of thesubgiant and red giant class.
| Identification of a complete sample of northern ROSAT All-Sky Survey X-ray sources. VIII. The late-type stellar component
We present results of an investigation of the X-ray properties, agedistribution, and kinematical characteristics of a high-galacticlatitude sample of late-type field stars selected from the ROSAT All-SkySurvey (RASS). The sample comprises 254 RASS sources with opticalcounterparts of spectral types F to M distributed over six study areaslocated at |b| 20 °, and Dec ≥ -9 °. A detailed studywas carried out for the subsample of ~200 G, K, and M stars. Lithiumabundances were determined for 179 G-M stars. Radial velocities weremeasured for most of the 141 G and K type stars of the sample. Combinedwith proper motions these data were used to study the age distributionand the kinematical properties of the sample. Based on the lithiumabundances half of the G-K stars were found to be younger than theHyades (660 Myr). About 25% are comparable in age to the Pleiades (100Myr). A small subsample of 10 stars is younger than the Pleiades. Theyare therefore most likely pre-main sequence stars. Kinematically the PMSand Pleiades-type stars appear to form a group with space velocitiesclose to the Castor moving group but clearly distinct from the LocalAssociation.Based on observations collected at the German-Spanish AstronomicalCentre, Calar Alto, operated by the Max-Planck-Institut fürAstronomie, Heidelberg, jointly with the Spanish National Commission forAstronomy, and at the European Southern Observatory, La Silla, Chile.Tables A2-A4 are only available in electronic form athttp://www.edpsciences.org
| 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.
| Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I.
We have embarked on a project, under the aegis of the Nearby Stars(NStars)/Space Interferometry Mission Preparatory Science Program, toobtain spectra, spectral types, and, where feasible, basic physicalparameters for the 3600 dwarf and giant stars earlier than M0 within 40pc of the Sun. In this paper, we report on the results of this projectfor the first 664 stars in the northern hemisphere. These resultsinclude precise, homogeneous spectral types, basic physical parameters(including the effective temperature, surface gravity, and overallmetallicity [M/H]), and measures of the chromospheric activity of ourprogram stars. Observed and derived data presented in this paper arealso available on the project's Web site.
| 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 database of high and medium-resolution stellar spectra
We present a database of 908 spectra of 709 stars obtained with theELODIE spectrograph at the Observatoire de Haute-Provence. 52 orders ofthe echelle spectra have been carefully fitted together to providecontinuous, high-resolution spectra in the wavelength range lambdalambda = 410-680 nm. The archive provides a large coverage of the spaceof atmospheric parameters: T_eff from 3700 K to 13 600 K, log g from0.03 to 5.86 and [Fe/H] from -2.8 to +0.7. At the nominal resolution,R=42 000, the mean signal-to-noise ratio is 150 per pixel. The spectragiven at this resolution are normalized to their pseudo-continuum andare intended to serve for abundance studies, spectral classification andtests of stellar atmosphere models. A lower resolution version of thearchive, at R=10 000, is calibrated in physical flux with a broad-bandphotometric precision of 2.5% and narrow-band precision of 0.5%. It iswell suited to stellar population synthesis of galaxies and clusters,and to kinematical investigations of stellar systems. The archive isdistributed in FITS format through the HYPERCAT and CDS databases. Basedon observations made on the 193 cm telescope at the Haute-ProvenceObservatory, France. Table 1 is 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/cgi-bin/qcat?J/A+A/369/1048
| Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics
The Catalogue, available at the Centre de Données Stellaires deStrasbourg, consists of 13 573 records concerning the results obtainedfrom different methods for 7778 stars, reported in the literature. Thefollowing data are listed for each star: identifications, apparentmagnitude, spectral type, apparent diameter in arcsec, absolute radiusin solar units, method of determination, reference, remarks. Commentsand statistics obtained from CADARS are given. The Catalogue isavailable in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcar?J/A+A/367/521
| Studies of Large-Amplitude delta Scuti Variables. III. DY Pegasi
This is the third in a series of papers on large-amplitude delta Scutiand related stars intended to determine Baade-Wesselink radii andluminosities with precision. The first two papers discussed our methodof analysis and its application to the delta Scuti variables EH Libraeand DY Herculis; in the present paper we discuss the observations andanalysis of the SX Phoenicis variable DY Pegasi. Optical (BVI) andinfrared (JH) photometry and cross-correlated radial velocity data havebeen obtained and analyzed. Fourier representations for the BVIH lightcurves and for the radial velocity curve were used to derive a value forthe minimum radius for each of 22 combinations of flux and color index,from which we obtain a mean value for the minimum radius ofR_min=2.09+/-0.25 R_solar. When combined with effective temperaturesfrom Burki & Meylan, we find a mean bolometric luminosity of=11.34 L_solar and a mean absolute magnitude of=2.11. The radial excursion (R_max-R_min) is 0.073 R_solar.
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| G. P. Kuiper's spectral classifications of proper-motion stars
Spectral classifications are listed for over 3200 stars, mainly of largeproper motion, observed and classified by Kuiper during the years1937-1944 at the Yerkes and McDonald Observatories. While Kuiper himselfpublished many of his types, and while improved classifications are nowavailable for many of these stars, much of value remains. For many ofthe objects, no other spectral data exist.
| The nature of the Giclas +4 stars
Broadband BVRI photometry has been obtained for 130 stars in the LowellObservatory proper motion survey with color class +4. The sample iscomplete for the 75 +4 class stars between RA = 2h31m and RA = 12h20m inthe Northern Hemisphere. The absolute magnitudes and distances of thestars are estimated using the R magnitude-(R-I) relation. Most of thestars are normal late-type dwarf stars. The B-V color distribution forthe +4 class stars is similar to that for +3 class stars, suggestingthere is no significant difference between the two color classes.Several individual stars which may be subluminous or otherwise ofinterest have been identified, as have several stars within 25 pc whichare not included in published catalogs of nearby stars.
| Catalogue of stars with CaII H and K emissions
Not Available
| The luminosity law for late-type main-sequence stars in the solar neighborhood
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1974PASP...86..697E&db_key=AST
| Calcium emission intensities as indicators of stellar age.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970MNRAS.148..463W&db_key=AST
| Radial velocities of dK and dM stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1967AJ.....72..905W&db_key=AST
| Stars with large proper motions in the astrographic zones+ 32° and + 33° (List I)
Not Available
| Photovisual magnitudes of 418 dwarf M stars and 34 parallax stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..219S&db_key=AST
| Dwarf M stars found spectrophotometrically .
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1956AJ.....61..201V&db_key=AST
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| קבוצת-כוכבים: | כלבי ציד |
| התרוממות ימנית: | 13h34m03.24s |
| סירוב: | +33°13'42.2" |
| גודל גלוי: | 9.241 |
| מרחק: | 22.904 פארסק |
| תנועה נכונה: | -259.6 |
| תנועה נכונה: | 324.4 |
| B-T magnitude: | 10.605 |
| V-T magnitude: | 9.354 |
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