Journal Article

Spectral analysis of the high-gravity extreme helium star LS IV+6°2

C. Simon Jeffery

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 294, issue 3, pages 391-398
Published in print March 1998 | ISSN: 0035-8711
Published online March 1998 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-8711.1998.01133.x
Spectral analysis of the high-gravity extreme helium star LS IV+6°2

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Abstract

The optical spectrum of the early B hydrogen-deficient star LS IV+6°2 has been analysed. With Teff = 31000 K, log g = 4.05, nH ∼ 10-4 and nc ∼ 0.1 (relative abundances by number), it is the hottest high-gravity extreme helium star (EHe) yet studied. The He i spectrum shows all predicted permitted and forbidden transitions in absorption. LS IV+6°2 is a comparatively metal-rich EHe star; abundances of C, N, O, Ne, Mg, Al and P are typical of other EHes, whilst Si and S are somewhat deficient. With the surface parameters given, LS IV+6°2 lies close to the boundary of the helium star pulsation instability finger near Teff ∼ 27000 K. Available data indicate that the radial velocity is variable, but give no indication of amplitude or period.

Keywords: stars: abundances; stars: atmospheres; stars: chemically peculiar; stars: individual: LS IV+6°2

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Subjects: Astronomy and Astrophysics

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