Spectral analysis of the high-gravity extreme helium star LS IV+6°2 |
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Authors: | C Simon Jeffery |
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Institution: | Armagh Observatory, College Hill, Armagh BT61 9DG |
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Abstract: | The optical spectrum of the early B hydrogen-deficient star LS IV+6°2 has been analysed. With T eff = 31000 K, log g = 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 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 T eff ~ 27000 K. Available data indicate that the radial velocity is variable, but give no indication of amplitude or period. |
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Keywords: | stars: abundances stars: atmospheres stars: chemically peculiar stars: individual: LS IV+6°2 |
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