Fizik Bölümü / Department of Physics

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Browsing Fizik Bölümü / Department of Physics by Author "Adelman, Saul J."

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    Elemental Abundance Analyses With DAO Spectrograms - XXV. The Superficially Normal B and A Stars Alpha Ddraconis, Tau Herculis, Gamma Lyrae, and HR 7926
    (2001-06) Adelman, Saul J.; Çalışkan, H.; Koçer, Dursun; Kablan, H.; Yüce, K.; Engin, S.
    Elemental abundances analyses of the superfically normal B and A stars alpha Dra (A0 III), tau Her (B5 IV), gamma Lyr (B9 III), and HR 7926 (B8 II-III) are performed consistent with previous studies of this series using spectrograms obtained with Reticon and CCD detectors. Comparisons of the first two analyses with those of the same stars performed earlier in this series which used mostly coadded photographic plates show the general consistency of the derived elemental abundances. A slight increase in the adopted effective temperature produces a corresponding increase in the derived abundances. In these stars the He/H ratios are found to be close to solar. Except for Lyr the metals show for the most part marginally subsolar abundance values. But this star has Al, Ca, Sc, and Sr abundances that are substantially underabundant as well as other underabundant values.
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    Elemental abundance analyses with DAO spectrograms. XXXIX. The am stars 2 UMa and 15 Vul
    (Iop Publishing Ltd, Temple Circus, Temple Way, Bristol Bs1 6Be, England, 2016-05) Çay, İpek; Teker Yelkenci, Ayşegül; Adelman, Saul J.; 123099
    We derived the elemental abundances of the metallic-line stars 2 UMa (=HR 3354; spectral type A2m) and 15 Vul (=HR 7653; spectral type A4 III), using high-dispersion, high signal-to-noise ratio (>= 200) optical region spectrograms obtained with CCD detectors at the long Coude camera of the 1.22 m telescope of the Dominion Astrophysical Observatory (DAO) and Kurucz's ATLAS9 and WIDTH9 programs. The star 2 UMa has not been the subject of a modern detailed elemental abundances analysis. It is relatively sharp-lined and sufficiently hot (T-eff = 8050 K) that the continuum placement is not a major problem in the optical region. Comparison of the results of this new study of 15 Vul with the last complete study shows a 0.15 dex mean increase in the derived abundances and a reduction in the standard deviations of the mean values. The abundance anomalies of 2 UMa are usually larger than those of 15 Vul. The greater spectral coverage of 15 Vul compared with 2 UMa results in a larger number of abundances being derived. The abundances of 2 UMa are typical for those of classical Am stars that have similar effective temperatures and surface gravities. 15 Vul, characterized by a similar effective temperature and smaller surface gravity, is a more evolved star.