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Oxygen line formation in late-F through early-K disk/halo stars. Infrared O I triplet and [O I] lines
In order to investigate the formation of O I 7771-5 and [O I] 6300/6363lines, extensive non-LTE calculations for neutral atomic oxygen werecarried out for wide ranges of model atmosphere parameters, which areapplicable to early-K through late-F halo/disk stars of variousevolutionary stages.The formation of the triplet O I lines was found to be well described bythe classical two-level-atom scattering model, and the non-LTEcorrection is practically determined by the parameters of theline-transition itself without any significant relevance to the detailsof the oxygen atomic model. This simplifies the problem in the sensethat the non-LTE abundance correction is essentially determined only bythe line-strength (Wlambda ), if the atmospheric parametersof Teff, log g, and xi are given, without any explicitdependence of the metallicity; thus allowing a useful analytical formulawith tabulated numerical coefficients. On the other hand, ourcalculations lead to the robust conclusion that LTE is totally valid forthe forbidden [O I] lines.An extensive reanalysis of published equivalent-width data of O I 7771-5and [O I] 6300/6363 taken from various literature resulted in theconclusion that, while a reasonable consistency of O I and [O I]abundances was observed for disk stars (-1 <~ [Fe/H] <~ 0), theexistence of a systematic abundance discrepancy was confirmed between OI and [O I] lines in conspicuously metal-poor halo stars (-3 <~[Fe/H] <~ -1) without being removed by our non-LTE corrections, i.e.,the former being larger by ~ 0.3 dex at -3 <~ [Fe/H] <~ -2.An inspection of the parameter-dependence of this discordance indicatesthat the extent of the discrepancy tends to be comparatively lessenedfor higher Teff/log g stars, suggesting the preference ofdwarf (or subgiant) stars for studying the oxygen abundances ofmetal-poor stars.Tables 2, 5, and 7 are 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/402/343 and Table\ref{tab3} is only available in electronic form athttp://www.edpsciences.org
| Catalogs of temperatures and [Fe/H] averages for evolved G and K stars
A catalog of mean values of [Fe/H] for evolved G and K stars isdescribed. The zero point for the catalog entries has been establishedby using differential analyses. Literature sources for those entries areincluded in the catalog. The mean values are given with rms errors andnumbers of degrees of freedom, and a simple example of the use of thesestatistical data is given. For a number of the stars with entries in thecatalog, temperatures have been determined. A separate catalogcontaining those data is briefly described. Catalog only available atthe CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Lithium abundance and mass
Observations of cool giants have shown that there exists a large rangein their lithium abundances even for apparently similar stars. Thedepletions are large in a majority of them, far in excess of thepredictions of the standard stellar evolution models. In order toexplore whether the large spread in Li abundances observed in giants canbe interpreted in terms of mass, moderately high resolution CCD spectraof the Li I line at 6707.8 Ä have been obtained in 65 subgiants,giants and supergiants and the lithium abundances derived. Theirabsolute magnitudes have been estimated from the Hipparcos data.Absolute magnitudes have also been determined for another 802 starswhose lithium abundances are already known from the availableliterature. All these stars have been plotted on the HR diagram andcompared with the theoretical evolutionary tracks of Bressan et al.(1993) with initial masses ranging from 1 M_sun to 9 M_sun for achemical composition typical of the solar neighbourhood: X=0.70, Y=0.28,Z=0.02. The stars of low mass of this sample, (<2M_sun), span a widerange in evolution (unmixed warm subgiants and mixed giants) andtherefore, show a correspondingly wide range of Li abundances, perhapsreminiscent of the large range in abundances observed on the mainsequence. The spread is further augmented by the effects of increasingdilution and mixing as the stars evolve to the right and up the redgiant branch. Higher mass stars show a different behaviour. Many of thegiants of masses between 2.5 and 4.0 M_sun observed in the present studyhave Li abundances close to what is predicted by the standard stellarmodels. On the other hand, there are several high mass giants (>2.5M_sun) cooler than Teff = 5000 K with Li abundances as low asthose of low mass stars of similar effective temperature. There must beparameters other than mass and evolutionary status, as implied by thestandard evolution model of a star, that control its Li abundance.
| The central depth of the Ca II triplet lines as a discriminant of chromospheric activity in late type stars
Not Available
| Chromospheric activity in cool stars and the lithium abundance
A detailed analysis of the Ca II triplet lines lkern -4.1ptlower2ptchar19 kern -0.8ptambdalkern -4.1ptlower2pt char19 kern -0.8ptambda8498,8542, 8662 in 146 cool stars of all luminosities spanning a large rangein metallicity has revealed that stars with similar temperature,luminosity and metallicity have different Ca II central depths due todifferent degrees of their chromospheric activity. Based on this idea,14 stars in the sample have been identified as chromospherically moreactive than their counterparts with similar values of atmosphericparameters. In order to explore the interdependence betweenchromospheric activity, age and lithium abundance, CCD echelle spectraof the Li I line at 6707.8 Angstroms have been obtained at a spectralresolution of 0.35 Angstroms in these 14 active stars, 18 relativelyinactive stars and another 17 stars randomly selected from the abovesample. The analysis shows that although a few of the active stars areLi-rich, there does not exist a one-to-one correlation between Liabundance and chromospheric activity. There is almost an equal number ofinactive stars which are Li rich. Otherwise, lithium depletions arelarge and there is a large spread in Li abundances in both active andinactive stars especially among giants and supergiants. For most ofthem, the abundance log N(Li) lies roughly between -0.3 to +0.7. Asimilar large range in Li abundances is found for giants not selected onthe basis of chromospheric activity. The above observations suggestthere are parameters besides the activity related ones controlling thelithium abundance in these stars.
| A catalogue of [Fe/H] determinations: 1996 edition
A fifth Edition of the Catalogue of [Fe/H] determinations is presentedherewith. It contains 5946 determinations for 3247 stars, including 751stars in 84 associations, clusters or galaxies. The literature iscomplete up to December 1995. The 700 bibliographical referencescorrespond to [Fe/H] determinations obtained from high resolutionspectroscopic observations and detailed analyses, most of them carriedout with the help of model-atmospheres. The Catalogue is made up ofthree formatted files: File 1: field stars, File 2: stars in galacticassociations and clusters, and stars in SMC, LMC, M33, File 3: numberedlist of bibliographical references The three files are only available inelectronic form at the Centre de Donnees Stellaires in Strasbourg, viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5), or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| 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.
| A catalogue of Fe/H determinations - 1991 edition
A revised version of the catalog of Fe/H determinations published by G.Cayrel et al. (1985) is presented. The catalog contains 3252 Fe/Hdeterminations for 1676 stars. The literature is complete up to December1990. The catalog includes only Fe/H determinations obtained from highresolution spectroscopic observations based on detailed spectroscopicanalyses, most of them carried out with model atmospheres. The catalogcontains a good number of Fe/H determinations for stars from open andglobular clusters and for some supergiants in the Magellanic Clouds.
| A critical appraisal of published values of (Fe/H) for K II-IV stars
'Primary' (Fe/H) averages are presented for 373 evolved K stars ofluminosity classes II-IV and (Fe/H) values beween -0.9 and +0.21 dex.The data define a 'consensus' zero point with a precision of + or -0.018 dex and have rms errors per datum which are typically 0.08-0.16dex. The primary data base makes recalibration possible for the large(Fe/H) catalogs of Hansen and Kjaergaard (1971) and Brown et al. (1989).A set of (Fe/H) standard stars and a new DDO calibration are given whichhave rms of 0.07 dex or less for the standard star data. For normal Kgiants, CN-based values of (Fe/H) turn out to be more precise than manyhigh-dispersion results. Some zero-point errors in the latter are alsofound and new examples of continuum-placement problems appear. Thushigh-dispersion results are not invariably superior to photometricmetallicities. A review of high-dispersion and related work onsupermetallicity in K III-IV star is also given.
| Oxygen in old and thick disk stars
High resolution Reticon and CCD spectra comprehending the forbidden O I6300.311 line were obtained for old and thick disk stars. The spacevelocities were studied in order to classify the stars in the differentpopulation groups. The present results show that oxygen seems to beoverabundant relative to iron for metallicities Fe/H abundance ratio = -0.8. For metallicities with Fe/H abundance ratios between - 0.8 and -0.5, there seems to be a spread in the O/Fe abundance ratios. Thisspread could be an indication of a thick disk phase in thechemicodynamical evolution of the Galaxy. A difference seems to appearbetween oxygen-to-iron ratios derived from the forbidden and thepermitted lines.
| Population studies. II - Kinematics as a function of abundance and galactocentric position for (Fe/H) of -0.6 or less
A catalog is presented of some 1200 Galactic objects which have radialvelocities and (Fe/H) abundances of -0.6 or less. These data areanalyzed to yield information on the kinematic properties of the olderpopulations of the Galaxy and on the interdependence between kinematicsand abundance. It is found that the kinematics of the availablekinematically selected stars differ from those of the nonkinematicallyselected objects. No evidence is found for any significant difference inthe kinematic properties of the various halo subgroups, nor for anydependence of kinematics on abundance. While the rotation of the halo issmall at about 37 km/s for (Fe/H) of -1.2 or less, it rises quickly forhigher abundances to a value of about 160 km/s at (Fe/H) = 0.6. Objectsin the abundance range -0.9 to -0.6 appear to belong predominantly to apopulation possessing the kinematic characteristics of a thick disk. Theimplications of these findings for the suggestion that globular clustersbelong to the same population as the noncluster objects, for the originof the thick disk, and for the mass of the Galaxy are discussed.
| Spectral Classification and DDO Photometry of a Southern Group of Stars with Common Motions - Part One
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1982PASP...94..304L&db_key=AST
| Intermediate-band photometry of late-type stars. VIII - Nonvariable stars in the halo population near the sun
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1979ApJ...229..158E&db_key=AST
| Kinematical and orbital properties for selected southern high-velocity stars
Using the model of the Galaxy presented by Eggen, Lynden-Bell, andSandage (1962), plane galactic orbits have been calculated for severalsouthern high-velocity stars which possess parallax, proper motion, andradial velocity data. Extensive lists of both raw and computed data forthese stars are included. Published values of U-B and B-V for some ofthese stars were used in plots of each of the orbital parameters versusU-B, B-V, or the ultraviolet excess. Also, a comparison is made betweenthe H-R diagrams for the southern high-velocity star group and that ofM3, a globular cluster, and again for M67, an old open cluster. Thehigh-velocity star group is found to resemble an old open cluster morethan a globular cluster.
| Narrow-Band and Broad-Band Photometry of Red Stars. III. Southern Giants
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1970ApJ...161..199E&db_key=AST
| Fundamental data for southern stars (First list)
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1957MNRAS.117..534E&db_key=AST
| Radial velocities and spectral types in the galactic clusters M 25 and NGC 6087
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1957MNRAS.117..193F&db_key=AST
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Pozíciós és asztrometriai adatok
| Csillagkép: | Kentaur |
| Rektaszcenzió: | 13h47m38.40s |
| Deklináció: | -50°19'16.0" |
| Vizuális fényesség: | 5.45 |
| Távolság: | 139.276 parszek |
| RA sajátmozgás: | -140 |
| Dec sajátmozgás: | -5.7 |
| B-T magnitude: | 7.202 |
| V-T magnitude: | 5.6 |
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