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Astron. Astrophys. 317, 178-184 (1997)

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Abundance anomalies in main sequence A stars *

III. Nitrogen and sulphur

Inga Rentzsch-Holm

Institut für Astronomie und Astrophysik, Universität Kiel, D-24098 Kiel, Germany

Received 28 March 1996 / Accepted 3 May 1996

Abstract

Nitrogen and sulphur abundances in 15 sharp-lined `normal' main sequence A stars are determined from new high-resolution CCD spectra. Non-LTE effects are taken into account.

Nitrogen abundances are distributed over an interval of 0.5 dex around the solar value of 8.05. Non-LTE abundance corrections range from -0.2 to -1.2 dex.

Sulphur is overabundant with respect to the sun by 0.1 to 0.6 dex in all program stars. Taking non-LTE effects into account reduces the overabundances, but cannot remove them entirely; non-LTE abundance corrections [FORMULA] are typically -0.1 dex.

Comparison with previously derived carbon abundances reveals that carbon and nitrogen behave very similarly in each star. Thus the anticorrelation of [C/Si] with [Si/H] found by Holweger (1992) is also true for [N/Si]. For sulphur a similar anticorrelation is also possible.

Key words: stars: abundances — stars: early-type — stars: individual: Sirius

* Based on observations obtained at the European Southern Observatory, La Silla, Chile

SIMBAD Objects

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