Synthetic Lick Indices and Detection of α‐enhanced Stars. II. F, G, and K Stars in the −1.0 < [Fe/H] < +0.50 Range
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We present an analysis of 402 F, G, and K solar neighborhood stars, with accurate estimates of [Fe/H] in the range -1.0 to +0.5 dex, aimed at the detection of α-enhanced stars and at the investigation of their kinematical properties. The analysis is based on the comparison of 571 sets of spectral indices in the Lick/IDS system, coming from four different observational data sets, with synthetic indices computed with solar-scaled abundances and with α-element enhancement. We use selected combinations of indices to single out α-enhanced stars without requiring previous knowledge of their main atmospheric parameters. By applying this approach to the total data set, we obtain a list of 60 bona fide α-enhanced stars and of 146 stars with solar-scaled abundances. The properties of the detected α-enhanced and solar-scaled abundance stars with respect to their [Fe/H] values and kinematics are presented. A clear kinematic distinction between solar-scaled and α-enhanced stars was found, although a one-to-one correspondence to "thin disk" and "thick disk" components cannot be supported with the present data.The paper attempts to put together the spectroscopic definitions used in the literature for different groups of peculiar objects linked with abundance anomalies. The groups discussed are: O-type subdwarfs CNO stars He-strong stars He-weak stars B-type subdwarfs Ap stars Am stars λ Boo stars δ Del stars Fm stars A-F-G stars with weak metal lines Stars with CN anomalies Stars with CH anomalies Ba stars In each case the useful range in dispersion is quoted and bibliographic references are provided.
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Anomalous ionization (C IV and Si IV is seen in IUE spectra of Be stars as late as B8, and occurs also in standard stars of similar spectral type. Asymmetrical lines suggesting mass loass are present in all the Be stars and several of the standard stars as well, with no obvious correlation with v sin i. Emission shoulders are present in the Mg II lines of two B5e stars but not in Be stars of later type. No correlation is found with v sin i. The A-F shell stars show rich Fe iI absorption spectra in the ultraviolet, in one case with velocity structure.
Ultraviolet
O-type star
Flare star
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We have known for more than 40 years (Morgan 1933) that a group of stars having abnormal spectra exists among the main sequence stars included between B5 and F2. They represent at least 15% of the normal stars with the same color and luminosity. They can be divided in two large groups and their properties are summarized in Tables 1 and 2. They are the Ap stars (including the various subgroups, Mn stars, Si stars, Sr-Cr-Euor cool Ap stars) and the Am, Fm stars.
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view Abstract Citations (45) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Abundance of Gallium in B-Type Chemically Peculiar Stars Takada-Hidai, M. ; Sadakane, K. ; Jugaku, J. Abstract Quantitative analyses of the Ga abundances in 27 Hg-Mn stars, 11 Si (magnetic) stars, eight He-weak stars, and seven normal stars are made with the resonance lines of Ga II at 1414 A and Ga III at 1495 A in International Ultraviolet Explorer (IUE) spectra. The Ga overabundances are confirmed as a genuine anomaly in many peculiar stars. Only upper limits of the Ga abundance can be obtained for some stars. However, these upper limits are much lower than those inferred from visual spectra. Among the 27 Hg-Mn stars, 17 stars are distributed in a range of 2.0-3.8 dex of overabundances of Ga. Ten other stars show upper limits of less than 2.1 dex. Fifteen of the 20 hotter Hg-Mn stars, with Teff greater than 11,000 K, show high overabundances in a narrow range of 2.6-3.8 dex, while among seven cooler Hg-Mn stars, only the star HR 7775 shows the same overabundance as in the hotter 15 stars. Of 11 Si stars, nine stars have Ga overabundances ranging from 1.9 to 3.2 dex. Gallium is overabundant in five out of eight He-weak stars in the range of 1.7-3.2 dex, while in the three other stars the upper limits are less than 1.3 dex. The Ga abundances in normal stars are all upper limits which roughly correspond to the solar value. Publication: The Astrophysical Journal Pub Date: May 1986 DOI: 10.1086/164177 Bibcode: 1986ApJ...304..425T Keywords: Abundance; B Stars; Gallium; Peculiar Stars; Stellar Composition; A Stars; Astronomical Catalogs; Cosmochemistry; Iue; Resonance Lines; Astrophysics; STARS: ABUNDANCES; STARS: PECULIAR A; ULTRAVIOLET: SPECTRA full text sources ADS | data products SIMBAD (55) MAST (1) INES (1) Related Materials (1) Addendum: 1987ApJ...320..437T
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It is very important for the understanding of the Be phenomenon, and particularly for locating a possible Be phase in the evolutionary track of B stars, to accurately determine the proportion of Be stars among all B stars. This type of study was already made several times in the past. Results obtained generally show a maximum Be frequency around spectral type B2 then a decrease towards late spectral types. Actually Be stars do not have the same characteristics as “normal” B stars and we have to take this into account in the determination of the ratio : number of Be stars / number of B stars. We use the Bright Star Catalogue (Hoffleit & Jaschek 1982) and the Supplement to the Bright Star Catalogue (Hoffleit, Saladyga & Wlasuk 1983) containing stars V= 7.10 and brighter. This study needed to be made separately for the different spectral types because: - Physical parameters of B stars are very different from B0 to B9; - Emission characteristics of Be stars vary very much, with a decrease from B0e to B9e. We successively consider three effects which can influence the frequency of Be stars: - The over-luminosity of Be stars as compared with B stars; - Spectral type changes during constant mass evolution; - Spectral type changes due to the fast rotation of Be stars.
Herbig Ae/Be star
Flare star
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Blue straggler
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We have carried out spectroscopic observations and made preliminary classifications of 62 UV‐bright stars identified by H. H. Lanning on plates taken by A. Sandage. The goal was to search for "interesting" objects, such as emission‐line stars, hot subdwarfs, and high‐gravity stars. Our targets were grouped into two samples, a bright (mB<13) sample of 35 stars observed with the Kitt Peak 2.1 m telescope and a faint (13
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A full abundance analysis have been carried out in 12 galactic J-stars. The analysis shows: a) 12 C/ 13 C ratios are low, b) the abundance of s-process and rare-earth elements with respect to the stellar metallicity is nearly-solar, [< heavy > / Fe ] = 0.10 ± 0.11 c) Tc is not present in most of the stars although upper limits are placed in WZ Cas and WX Cyg, probably two SC-type stars, and d) all the stars are Li-rich, log ∈(Li)> 1. The location of J-stars in an empirical H-R diagram when compared with that of the normal N-type carbon stars, suggests that J-stars may be in the early-AGB phase. The different mechanism proposed to be responsible of this Li production are briefly discussed.
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Abstract Quantitative analyses of the Ga abundances in 27 Hg-Mn stars, 11 Si (magnetic) stars, 8 He-weak stars, and 7 normal stars are made with the resonance lines of Ga II at 1414 Å and Ga III at 1495 Å in IUE spectra. The Ga overabundances are confirmed as a genuine anomaly in many peculiar stars. Only upper limits of the Ga abundance can be obtained for some stars. However these upper limits are much lower than those inferred from visual spectra. Among the 27 Hg-Mn stars, 17 stars are distributed in the range of 2.0 – 3.8 dex of overabundances of Ga. Ten other stars show upper limits less than 2.1 dex. Fifteen stars of 20 hotter Hg-Mn stars with T eff > 11000 K show high overabundances in a narrow range of 2.6 – 3.8 dex, while, among 7 cooler Hg-Mn stars, the only star HR 7775 shows the same overabundance as in these 15 stars. Of 11 Si stars, 9 stars have Ga overabundances ranging from 1.9 to 3.2 dex. Gallium is overabundant in 5 out of 8 He-weak stars in the range of 1.7 – 3.2 dex, while in the three other stars the upper limits are less than 1.3 dex. The Ga abundances in normal stars are all upper limits which roughly correspond to the solar value.
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