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Elemental abundances in the atmosphere of clump giants
Aims.The aim of this paper is to provide the fundamental parameters andabundances for a large sample of local clump giants with a highaccuracy. This study is a part of a big project, in which the verticaldistribution of the stars in the Galactic disc and the chemical anddynamical evolution of the Galaxy are being investigated. Methods:.The selection of clump stars for the sample group was made applying acolour-absolute magnitude window to nearby Hipparcos stars. Theeffective temperatures were estimated by the line depth ratio method.The surface gravities (log {g}) were determined by two methods (thefirst one was the method based on the ionization balance of iron and thesecond one was the method based on fitting of the wings of the Ca I6162.17 Å line). The abundances of carbon and nitrogen wereobtained from the molecular synthetic spectrum, and the Mg and Naabundances were derived using the non-LTE approximation. The "classical"models of stellar evolution without atomic diffusion androtation-induced mixing were employed. Results: .The atmosphericparameters ({T_eff}, log {g}, [Fe/H], {Vt}) and Li, C, N, O,Na, Mg, Si, Ca, and Ni abundances in 177 clump giants of the Galacticdisc were determined. The underabundance of carbon, overabundance ofnitrogen, and "normal" abundance of oxygen were detected. A small sodiumoverabundance was found. A possibility of a selection of the clumpgiants based on their chemical composition and the evolutionary trackswas explored. Conclusions: .The theoretical predictions based onthe classical stellar evolution models are in good agreement with theobserved surface variations of the carbon and nitrogen just after thefirst dredge-up episode. The giants show the same behaviour of thedependencies of O, Mg, Ca, and Si (α-elements) and Ni (iron-peakelement) abundances vs. [Fe/H] as dwarfs do. This allows us to use suchabundance ratios to study the chemical and dynamical evolution of theGalaxy.
| 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.
| Chemical composition of red horizontal branch stars in the thick disk of the Galaxy
High-resolution spectra of 13 core helium-burning stars in the thickdisk of the Galaxy have been obtained with the SOFIN spectrograph on theNordic Optical Telescope to investigate abundances of up to 22 chemicalelements. Abundances of carbon were studied using the C2 Swan(0, 1) band head at 5635.5 Å. The wavelength interval 7980-8130Å with strong CN features was analysed in order to determinenitrogen abundances and 12C/13C isotope ratios.The oxygen abundances were determined from the [O I] line at 6300Å. Abundances in the investigated stars suggest that carbon isdepleted by about 0.3 dex, nitrogen is enhanced by more than 0.4 dex andoxygen is unaltered. The 12C/13C ratios arelowered and lie between values 3 and 7 which is in agreement with ``coolbottom processing'' predictions (Boothroyd & Sackmann 1999). The C/Nratios in the investigated stars are lowered to values between 0.7 and1.2 which is less than present day theoretical predictions and call forfurther studies of stellar mixing processes. Abundance ratios of O, Mg,Eu and other heavy chemical elements to iron in the investigated starsshow a pattern characteristic of thick disk stars. The results provideevidence that the thick disk population has a distinct chemical historyfrom the thin disk. The onset of the bulk of SN Ia is suggested toappear at [Fe/H] ~ -0.6 dex. Based on observations obtained at theNordic Optical Telescope, La Palma. Table 1 is only available inelectronic at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp:/cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/380/578
| Classification of Population II Stars in the Vilnius Photometric System. II. Results
The results of photometric classification of 848 true and suspectedPopulation II stars, some of which were found to belong to Population I,are presented. The stars were classified using a new calibrationdescribed in Paper I (Bartkevicius & Lazauskaite 1996). We combinethese results with our results from Paper I and discuss in greaterdetail the following groups of stars: UU Herculis-type stars and otherhigh-galactic-latitude supergiants, field red horizontal-branch stars,metal-deficient visual binaries, metal-deficient subgiants, stars fromthe Catalogue of Metal-deficient F--M Stars Classified Photometrically(MDPH; Bartkevicius 1993) and stars from one of the HIPPARCOS programs(Bartkevicius 1994a). It is confirmed that high galactic latitudesupergiants from the Bartaya (1979) catalog are giants or even dwarfs.Some stars, identified by Rose (1985) and Tautvaisiene (1996a) as fieldRHB stars, appear to be ordinary giants according to our classification.Some of the visual binaries studied can be considered as physical pairs.Quite a large fraction of stars from the MDPH catalog are found to havesolar metallicity. A number of new possible UU Herculis-type stars, RHBstars and metal-deficient subgiants are identified.
| Chemical abundances in 10 red horizontal branch stars located in the galactic field
High-dispersion spectra of 10 red horizontal branch (RHB) stars of thegalactic field were obtained on the 6-m Special AstrophysicalObservatory (SAO) telescope to investigate abundances of up to 22chemical elements. This constitutes the largest single high-resolutionabundance study of RHB stars located in the galactic field. Abundancetrends in the range of -1.9<=[Fe/H]<=-0.2 are compared withresults for dwarfs and red giants, as well as with theoretical trends.For five metal-deficient stars of the sample, a slight overabundance ofoxygen is revealed. The results for alpha-process elements matchtheoretical predictions; only [Mg/Fe], for almost all stars, is belowthe theoretical trend. Almost all stars of the sample closely follow thesolar [Na/Fe] ratio; only for the two most metal-abundant stars issodium overabundant by 0.2-0.3dex. A comparison of the availableabundances of atmospheres for the RHB stars with those for giants anddwarfs shows a good fit for the iron group elements and for otherheavier elements; thus, RHB stars may also serve for Galactic chemicalevolution studies.
| GPM1 - a catalog of absolute proper motions of stars with respect to galaxies
The description of the first version of the General Compiled Catalogueof Absolute Proper Motions (GPM1) for a sample of HIPPARCOS stars,derived with respect to galaxies within the plan called Catalogue ofFaint Stars (KSZ, Deutch 1952), is presented. The principal aim of theGPM1 construction was to provide absolute proper motions of stars todetermine the rotation of the HIPPARCOS system. The GPM1 cataloguecontains 977 HIPPARCOS Input Catalogue stars with V magnitudes $5^m -11^m in 180 fields north of -25 degrees of declination. The accuracy ofthe proper motions is 8 mas/yr (milliarcseconds per year). Comparison ofproper motions of GPM1 with those of the PPM and ACRS was performed andanalyzed with respect to systematic errors caused by spurious rotationof the FK5 system. The standard errors show that the rotation may bedetermined with an accuracy better than 1 mas/yr. Catalog is onlyavailable in electronic form at the CDS via anonymous ftpcdsarc.u-strasbg.fr or ftp 130.79.128.5.
| GPM - compiled catalogue of absolute proper motions of stars in selected areas of sky with galaxies.
Not Available
| Vilnius photometry of the red horizontal branch stars in the galactic thick disk
The photometric observations and three-dimensional classification in theVilnius system have been carried out for 13 of the red horizontal branch(RHB) stars in the Galactic thick disk identified by Rose (1985). Thephotometric spectral types, metallicities [Fe/H], effectivetemperatures, surface gravities and absolute magnitudes are determined.The age of about 10--12 Gyr is evaluated for this group of stars fromcomparison with model isochrones, indicating that the age of the thickdisk is intermediate between the disk globular and the oldest openclusters.
| The integrated spectra of M32 and of 47 Tuc: A comparative study at high spectral resolution
Integrated spectra have been obtained for the elliptical galaxy M32 andfor the 'metal-rich' Galactic globular cluster 47 Tuc. The spectra coverthe wavelength interval lambda lambda 3800-4400 A at a resolution of 2.5A full width at half maximum (FWHM) and S/N ratio of approximately100:1. Similar data have been acquired for a library of 191 individualstars, and, to support the 47 Tuc observations, integrated spectra offour additional metal-rich Galactic globular clusters have beenobtained. These observations are used to compare in detail theintegrated spectra of M32 (the most extensively studied ellipticalgalaxy) and 47 Tuc (the best-studied metal-rich Galactic globularcluster). Although M32 and 47 Tuc have similar optical broadband colorsand overall spectral types, when viewed at 2.5 A resolution spectranumerous subtle differences between their integrated are clearlyvisible. A system of 13 spectral indices, many of them originallydefined in Rose (1984), has been used to quantify these differences.Altogether twelve diagnostic diagrams are presented to illustrate themanner in which the integrated spectrum of M32 differs from that of 47Tuc. These diagrams are used to place several strong constraints on thestellar populations in these two systems.
| Radial velocities for interesting G-type stars at the North Galactic Pole
Radial velocity determinations are presented for 54 G-type stars at theNorth Galactic Pole cataloged by Upgren (1962) and studiedspectroscopically by Rose (1985). The radial velocities of the stars arein complete agreement with the values obtained by Rose, 45 km/s forfield red horizontal-branch stars and 22 km/s for G dwarf stars withabnormally strong metal lines. Velocities for a further 19 stars,including nine G-type subgiants and a barium star, are also presented.
| Red horizontal-branch stars in the galactic disk
A quantitative, three-dimensional spectral classification systemdeveloped by Rose (1984), which uses 2.5-A resolution spectra in theblue, has been used to identify a class of red horizontal branch (RHB)stars in the Galactic disk that are similar to those in the 'metal rich'globular cluster M 71. The RHB are denoted as evolved stars by their SrII 4077 line, and are distinguished from post-main sequence starsevolving through the same region of the HR diagram on the basis of theunique appearance of their CN 3883 and 4216 A bands. The RHB starsconsitute at least 5 percent of the entire giant branch population ofthe disk.
| Spectra of Upgren's unclassified stars.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1972AJ.....77..669S&db_key=AST
| The space distribution of late type stars in a North galactic pole region.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1962AJ.....67...37U&db_key=AST
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Группы:
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Наблюдательные данные и астрометрия
| Созвездие: | Большая Медведица |
| Прямое восхождение: | 12h04m05.21s |
| Склонение: | +37°59'58.9" |
| Видимая звёздная величина: | 9.172 |
| Собственное движение RA: | -54.5 |
| Собственное движение Dec: | -51.3 |
| B-T magnitude: | 10.112 |
| V-T magnitude: | 9.25 |
Каталоги и обозначения:
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