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Title:
Non-LTE Abundance Analyses of Nitrogen and Sulfur in Chemically Peculiar Stars of the Upper Main Sequence
Authors:
Takada-Hidai, Masahide; Takeda, Yoichi
Affiliation:
AA(Research Institute of Civilization, Tokai University, 1117 Kitakaname, Hiratsuka, Kanagawa 259-12 and Dominion Astrophysical Observatory, National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V8H 4M6, Canada), AB(Institute of Astronomy, Faculty of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181})
Publication:
Publ. of the Astronomical Society of Japan, v.48, p.739-752. (PASJ Homepage)
Publication Date:
10/1996
Origin:
PASJ
PASJ Keywords:
SPECTROSCOPY, STARS: ABUNDANCES, STARS: ATMOSPHERES, STARS: CHEMICALLY PECULIAR STARS, STARS: EARLY-TYPE
Bibliographic Code:
1996PASJ...48..739T

Abstract

The LTE and non-LTE abundances of nitrogen (N) and sulfur (S) in chemically peculiar stars of the upper main sequence were derived from the NI and SI lines observed in a near-infrared spectral region. The sample consisted of 11 stars: three HgMn stars, two Am stars, three magnetic Ap (SrCrEu) stars, two weak-lined stars, and one normal star. The following results were obtained: (1) the LTE abundances of N suffer a large non-LTE effect with correction factors of up to -0.6 dex, while those of S suffer a minor non-LTE effect with correction factors of up to -0.2 dex; (2) the non-LTE abundances of N are systematically below solar value among the sample stars. Although the deficiencies of N are mild in the normal and weak-lined stars, they are enhanced by a factor of up to 2 dex in HgMn stars. A star-to-star variation with a range of 1 dex or more in the N deficiency is shown in Am and SrCrEu stars; (3) the non-LTE abundances of S are solar or slightly overabundant among the sample stars, except for SrCrEu stars. S is systematically deficient relative to the Sun by a factor of >~ 0.7 dex in SrCrEu stars.

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