Abundance analyses of three helium-rich sdB stars

Naslim N., Jeffery C. S., Ahmad A., Behara N., ŞAHİN T.

ASTROPHYSICS AND SPACE SCIENCE, vol.329, no.1-2, pp.119-125, 2010 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 329 Issue: 1-2
  • Publication Date: 2010
  • Doi Number: 10.1007/s10509-010-0334-x
  • Journal Name: ASTROPHYSICS AND SPACE SCIENCE
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.119-125
  • Keywords: Helium-rich subdwarfs, Atmospheric parameters, Abundances, Evolution, SUBDWARF-B STARS, IA PROGENITOR SURVEY, DWARF COOLING CURVE, WHITE-DWARF, O-STARS, SUBLUMINOUS STARS, SPECTRAL-ANALYSIS, SPECTROSCOPY, PARAMETERS, PHOTOMETRY
  • Akdeniz University Affiliated: No

Abstract

As part of an extended study of the surface abundances of extremely helium-rich hot subdwarfs, highresolution 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.

As part of an extended study of the surface abundances of extremely helium-rich hot subdwarfs, high-resolution optical ,chelle 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]a parts per thousand a'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.