The Origin of Subluminous O Stars
The Origin of Subluminous O Stars
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亚光度O星的起源
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
H. Hirsch
中科院分区：
文献类型：
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作者：
U. Heber;H. Hirsch
Amongst the hot subdwarf stars, the helium enriched sdOs still remain a mystery. Rivalling scenarios for their origin include mergers of He white dwarfs, first proposed by Ron Webbink, and the so‐called “late hot flasher” where a star undergoes a delayed helium flash long after leaving the RGB. Recent NLTE spectral analyses revealed that an evolutionary link between sdO stars and their cooler cousins, the sdB stars, is plausible only for the helium‐deficient sdO stars, i.e. they are the likely successors to sdB stars. A large sample of sdO stars has recently been analysed using NLTE model atmospheres to derive carbon and nitrogen abundances. The stars are generally speaking either C‐rich or N‐rich—a few are both. The N‐rich stars are on average significantly cooler than the C‐rich, whereas both subsample have the same mean surface gravity. The surface composition of N‐rich He‐sdOs are best explained by the merger of two helium white dwarfs or of a helium white dwarf with a post‐sdB star. Only the late fla...
