Abundance analyses of three helium-rich sdB stars

Authors: N., Naslim¹; Jeffery, C.²; Ahmad, A.²; Behara, N.²; Şahìn, T.²

Source: Astrophysics and Space Science, Volume 329, Numbers 1-2, October 2010 , pp. 119-125(7)

Publisher: Springer

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Abstract:

As part of an extended study of the surface abundances of extremely helium-rich hot subdwarfs, high-resolution optical échelle spectra of the three helium-rich subdwarf B stars LB 1766, SB 21 and BPS 22940-0009 are presented. Opacity-sampled line-blanketed model atmospheres have been used to derive atmospheric properties and surface abundances. All three stars are moderately metal-poor compared with the Sun ([Fe/H]≍−0.4). The first two stars are nitrogen-rich He-sdBs, while the third is a carbon-rich He-sdB. The surface composition and locus of single N-rich He-sdBs are currently best explained by the merger of two helium white dwarfs. C-rich He-sdBs require further investigation.

Keywords: Helium-rich subdwarfs; Atmospheric parameters; Abundances; Evolution

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s10509-010-0334-x

Affiliations: 1: Armagh Observatory, College Hill, Armagh, BT61 9DG, N. Ireland, UK, Email: nas@arm.ac.uk 2: Armagh Observatory, College Hill, Armagh, BT61 9DG, N. Ireland, UK

Publication date: 2010-10-01