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Astron. Astrophys. 329, 1019-1027 (1998)


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Spectral analysis of the extreme helium star LSS 3184*

J.S. Drilling 1, C.S. Jeffery 2 and U. Heber 3

1 Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
2 Armagh Observatory, College Hill, Armagh BT61 9DG, Northern Ireland
3 Dr. Remeis-Sternwarte, Universität Erlangen-Nürnberg, D-96049 Bamberg, Germany

Received 17 October 1996 / Accepted 14 August 1997

Abstract

LSS 3184 is a hydrogen-deficient, early B-type giant, recently found to pulsate with a period of 2.5 hours. Its photospheric parameters have been derived from optical high-resolution spectra by the method of fine analysis. The principal results are [FORMULA], [FORMULA], [FORMULA], [FORMULA], [FORMULA], and [FORMULA]. Hydrogen is extremely deficient. The effective temperature is consistent with broad-band visual and ultraviolet spectrophotometry and an extinction [FORMULA]. Its previous evolution is reflected in the chemistry of the atmosphere, which contains enriched nitrogen from CNO-cycle hydrogen burning, and carbon from [FORMULA] helium burning. Thus LSS 3184 is a true extreme helium star with a composition similar to BD [FORMULA].

With [FORMULA], [FORMULA], and pulsation properties very similar to the C-poor and N-rich helium star V652 Her, evolutionary mechanisms which can result in very different surface compositions for the two stars must be examined.

Key words: stars: helium – individual (LSS 3184) – abundances – chemically peculiar – emission line: Be

* Based on observations obtained at the European Southern Observatory, La Silla, Chile, and with the IUE satellite retrieved from the IUE archive at the World Data Centre, Rutherford Appleton Laboratory, UK

Send offprint requests to: J.S. Drilling

© European Southern Observatory (ESO) 1998

Online publication: December 16, 1997
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