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מאמרים קשורים
Galactic model parameters for field giants separated from field dwarfs by their 2MASS and V apparent magnitudes
We present a method which separates field dwarfs and field giants bytheir 2MASS and V apparent magnitudes. This method is based onspectroscopically selected standards and is hence reliable. We appliedit to stars in two fields, SA 54 and SA 82, and we estimated a full setof Galactic model parameters for giants including their total localspace density. Our results are in agreement with the ones given in therecent literature.
| The Indo-US Library of Coudé Feed Stellar Spectra
We have obtained spectra for 1273 stars using the 0.9 m coudéfeed telescope at Kitt Peak National Observatory. This telescope feedsthe coudé spectrograph of the 2.1 m telescope. The spectra havebeen obtained with the no. 5 camera of the coudé spectrograph anda Loral 3K×1K CCD. Two gratings have been used to provide spectralcoverage from 3460 to 9464 Å, at a resolution of ~1 Å FWHMand at an original dispersion of 0.44 Å pixel-1. For885 stars we have complete spectra over the entire 3460 to 9464 Åwavelength region (neglecting small gaps of less than 50 Å), andpartial spectral coverage for the remaining stars. The 1273 stars havebeen selected to provide broad coverage of the atmospheric parametersTeff, logg, and [Fe/H], as well as spectral type. The goal ofthe project is to provide a comprehensive library of stellar spectra foruse in the automated classification of stellar and galaxy spectra and ingalaxy population synthesis. In this paper we discuss thecharacteristics of the spectral library, viz., details of theobservations, data reduction procedures, and selection of stars. We alsopresent a few illustrations of the quality and information available inthe spectra. The first version of the complete spectral library is nowpublicly available from the National Optical Astronomy Observatory(NOAO) via ftp and http.
| 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
| 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.
| Near-IR features in late type stars - Their relation with stellar atmosphere parameters
CCD spectroscopic observations for a sample of 106 late type stars plusthree galactic globular clusters in the near-IR are presented. The mostprominent features in that spectral region, the IR Ca-II triplet (8498,8542, 8662A) and the Mg-I line at 8807 A, are measured and theirdependence on the stellar atmosphere parameters (surface gravity,effective temperature and metal content) is analyzed. In agreement withwhat is found in previous studies, the Ca-II triplet strength showsbiparametrical behavior with surface gravity and metal abundance. The IRMg-I line strength is also biparametric, depending mainly on metalabundance and effective temperature. Principal component analysistechniques allow the prediction of the metal abundance and surfacegravity as a function of three observables: the IR Ca-II tripletstrength, the strength of the IR Mg-I line and the (R-I) color.
| S-process deficiencies in low-mass supergiant variables
Abundance analyses of four low-mass supergiant variable stars and twoPopulation I Cepheids have been carried out. The Population I Cepheidsshow normal, solar element ratios, and the low-mass variables showmetallicities ranging from solar down to (Fe/H) values typical ofthick-disk and, in a few cases, of halo stars. Most low-mass variablesshow a systematic underabundance of the heavy s- and r-process elements.The heavy-element underabundances correlate with second ionizationpotential in a manner suggesting that they are a non-LTE phenomenonarising from overionization by Lyman-continuum photons. Several low-massvariables, including RU Cen and V553 Cen, show carbon enhancements andsolar s-process abundances. Relative to the majority of the type IIvariables, these stars are s-process enhanced, and it is argued thatthey are related to the Ba II and CH stars.
| A survey of F-type stars
The results of a spectroscopic survey of 350 F-type stars at adispersion of 80 A/mm are presented. Twenty-two percent of the starsshow degree of metal line weakening; this result parallels that ofphotometric investigations in the uvby Beta system. The line weakeningparameter introduced correlates strongly with photometric indices andwith abundance anomalies established by theoreticians of stellaratmospheres. The classification can thus be used to easily select starswith underabundances stronger than a factor four with respect to thesun.
| Extremely metal-deficient red giants. IV - Equivalent widths for 36 halo giants
Further work on a study of 36 metal-poor field red giants is reported.Chemical abundances previously determined were based on model stellaratmosphere analyses of equivalent widths from photographic image-tubeechelle spectrograms obtained with with 4-m reflectors at Kitt Peak andCerro Tololo. A tabulation of the equivalent-width data (a total of 18,275 equivalent widths) is presented.
| Extremely metal-deficient red giants. III - Chemical abundance patterns in field halo giants
The chemical compositions of 36 metal-poor red giants are determined,using model-stellar-atmosphere analysis techniques, and discussed on thebasis of image-tube echelle spectrograms obtained with the 4-mtelescopes at Kitt Peak National Observatory and Cerro TololoInter-American Observatory. By forcing Fe I and Fe II to yield the sameiron abundances, the spectroscopic stellar-surface gravities are found.The resulting gravities are about 0.25 dex lower than expected for 0.7solar-mass stars with the luminosities of red giants in metal-deficientglobular clusters like M92. The well-known overall enhancements of thelight metals (Na through Ti, except for Sc), and the deficiencies of theheavy s-process elements (Sr, Y, Zr, and Ba) in iron-poor stars areconfirmed by abundance analyses. The abundance trends revealed by theobservational material are described, and the implications fornucleosynthesis during halo formation are discussed.
| A catalogue of Fe/H determinations, 1984 edition
The present version of the Cayrel de Strobel et al. (1981) catalog ofFe/H abundance ratio determinations contains 1921 values for 1035 stars,which represents an augmentation over the previous publication of 48 and47 percent, respectively. In addition, the literature search conductedis complete up to December, 1983. Stellar metal abundance, effectivetemperature, spectroscopic gravity, spectral type, and photometricindices are covered.
| Nickel overabundances in extremely metal-deficient red giants
Local thermodynamic equilibrium model-atmosphere abundance analyses of37 metal-poor (the Fe/H abundance ratio being between -3.0 and -6.0)field red-giant stars are carried out on the basis of high-dispersionechelle spectrograms. Nickel has been found to be overabundant in allstars with an abundance ratio less than -1.8; for the mostmetal-deficient star in the sample, the Ni/Fe abundance ratio is equalto +0.8. The elements in extreme Population II stars were probablysynthesized in very massive Type II supernovae. Therefore, the resultsimply that such supernovae eject material with a much higher Ni/Fe ratiothan do the less massive and more typical supernovae that made theelements in the solar system and young stars.
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | אריה קטן |
| התרוממות ימנית: | 10h47m55.53s |
| סירוב: | +23°20'07.0" |
| גודל גלוי: | 8.702 |
| מרחק: | 289.855 פארסק |
| תנועה נכונה: | 31.8 |
| תנועה נכונה: | -77.5 |
| B-T magnitude: | 9.528 |
| V-T magnitude: | 8.771 |
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