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Temperature Behavior of Elemental Abundances in the Atmospheres of Magnetic Peculiar Stars
We analyze the temperature dependence of the abundances of the chemicalelements Si, Ca, Cr, and Fe in the atmospheres of normal, metallic-line(Am), magnetic peculiar (Ap), and pulsating magnetic peculiar (roAp)stars in the range 6000 15000 K. The Cr and Fe abundances in theatmospheres of Ap stars increase rapidly as the temperature rises from6000 to 9000 10000 K. Subsequently, the Cr abundance decreases to valuesthat exceed the solar abundance by an order of magnitude, while the Feabundance remains enhanced by approximately +1.0 dex compared to thesolar value. The temperature dependence of the abundances of theseelements in the atmospheres of normal and Am stars is similar in shape,but its maximum is several orders of magnitude lower than that observedfor Ap stars. In the range 6000 9500 K, the observed temperaturedependences for Ap stars are satisfactorily described in terms ofelement diffusion under the combined action of gravitational settlingand radiative acceleration. It may well be that diffusion also takesplace in the atmospheres of normal stars, but its efficiency is very lowdue to the presence of microturbulence. We show that the magnetic fieldhas virtually no effect on the Cr and Fe diffusion in Ap stars in therange of effective temperatures 6000 9500 K. The Ca abundance and itsvariation in the atmospheres of Ap stars can also be explained in termsof the diffusion model if we assume the existence of a stellar wind witha variable moderate rate of (2 4) × 10- 15 M ȯ yr-1.
| The physical properties of normal A stars
Designating a star as of A-type is a result of spectral classification.After separating the peculiar stars from those deemed to be normal usingthe results of a century of stellar astrophysical wisdom, I define thephysical properties of the "normal" stars. The hotter A stars haveatmospheres almost in radiative equilibrium. In the A stars convectivemotions can be found which increase in strength as the temperaturedecreases.
| Non-LTE analyses of strontium abundances in stars. A stars
Not Available
| 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
| Elemental abundances of the B and A stars - III. Gamma Geminorum, HR 1397, HR 2154, HD 60825 and 7 Sextantis
Using ATLAS9 model atmospheres and additional spectroscopic data fromthe Kitt Peak coude-feed telescope obtained with a 3000-pixel-long CCD,camera 5, and grating A, we extend fine analyses of the B and A stars,gammaGem, HD 60825 and 7Sex. In addition, we study two moderatelysharp-lined middle B stars, HR 1397 and 2154, whose elemental abundanceswe find to be generally within the range of values seen forsuperficially normal, main-sequence stars of similar temperatures.
| A catalog of far-ultraviolet point sources detected with the fast FAUST Telescope on ATLAS-1
We list the photometric measurements of point sources made by the FarUltraviolet Space Telescope (FAUST) when it flew on the ATLAS-1 spaceshuttle mission. The list contains 4698 Galactic and extragalacticobjects detected in 22 wide-field images of the sky. At the locationssurveyed, this catalog reaches a limiting magnitude approximately afactor of 10 fainter than the previous UV all-sky survey, TDl. Thecatalog limit is approximately 1 x 10-14 ergs A sq cm/s,although it is not complete to this level. We list for each object theposition, FUV flux, the error in flux, and where possible anidentification from catalogs of nearby stars and galaxies. Thesecatalogs include the Michigan HD (MHD) and HD, SAO, the HIPPARCOS InputCatalog, the Position and Proper Motion Catalog, the TD1 Catalog, theMcCook and Sion Catalog of white dwarfs, and the RC3 Catalog ofGalaxies. We identify 2239 FAUST sources with objects in the stellarcatalogs and 172 with galaxies in the RC3 catalog. We estimate thenumber of sources with incorrect identifications to be less than 2%.
| Elemental abundances of the B and A stars. 2: Gamma Geminorum, HD 60825, 7 Sextantis, HR 4817, and HR 5780
We extend fine analyses of the B and A stars, gamma Geminorum, 7Sextantis, HR 4817, and HR 5780 using additional spectroscopic data fromthe Kitt Peak National Observatory (KPNO) coude feed telescope with a TICCD, camera 5, and grating A, and ATLAS9 model atmospheres. In additionwe study HD 60825, which had colors similar to the FHB A stars, but wasfound to be a Population I star. HD 60825, as is gamma Gem, is asharp-lined early-A star with nearly solar derived abundances. HR 5780and 7 Sex are also examples of stars which for the most part have solarabundances. The newly derived abundances for HR 4817 reveal importantdifferences with respect to 53 Tau, a somewhat similar HgMn star.
| Elemental abundance analyses with DAO spectrograms. XIII. The superficially normal early A-type stars 68 Tauri, 21 Lyncis and alpha Draconis.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.271..355A&db_key=AST
| In-Flight Performance and Preliminary Results from the Far Ultraviolet Space Telescope (Faust) Flown on ATLAS-1
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993ApJ...415..875B&db_key=AST
| Ultraviolet spectra of field horizontal-branch A-type stars. II
The spectra of six additional A-type stars have been obtained at lowresolution between 1200 and 1900 A with the IUE. The energydistributions of four of the stars match that of the field horizontalbranch (FHB) distribution in Huenemoerder et al. (1984) while those ofthe other two do not. Three of the FHB stars fall above a line in theC(19 - V)0 vs. (b-y)0 diagram; however, HD 60825 is anomalously blue forits C(19 - V) color.
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| Takýmyýldýz: | Kucuk Kopek |
| Sað Açýklýk: | 07h36m28.45s |
| Yükselim: | +02°52'03.9" |
| Görünürdeki Parlaklýk: | 7.834 |
| Uzaklýk: | 341.297 parsek |
| özdevim Sað Açýklýk: | -16.2 |
| özdevim Yükselim: | -16.6 |
| B-T magnitude: | 7.903 |
| V-T magnitude: | 7.84 |
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