Spectral analysis of the high-gravity extreme helium star LS IV+6o2

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.