Armagh Observatory Preprint Series No. 301

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

Authors: C.S.Jeffery

Journal: 1998, MNRAS 294, 391-398

Abstract. The optical spectrum of the early B hydrogen-deficient star LSIV+6 deg2 has been analysed. With T_eff=31000K, logg=4.05, n_H~10^-4 and n_c~0.1 (relative abundances by number), it is the hottest high-gravity extreme helium star (EHe) yet studied. The Hei spectrum shows all predicted permitted and forbidden transitions in absorption. LSIV+6 deg2 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, LSIV+6 deg2 lies close to the boundary of the helium star pulsation instability finger near T_eff~27000K. Available data indicate that the radial velocity is variable, but give no indication of amplitude or period.

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