Atmospheric parameters and abundances of sdB stars

Abstract

We summarize recent results of quantitative spectral analyses using NLTE and metal line-blanketed LTE model atmospheres. Temperatures and gravities derived for hundreds of sdB stars are now available and allow us to investigate systematic uncertainties of teff, log g scales and to test the theory of stellar evolution and pulsations. Surface abundance patterns of about two dozen sdB stars are surprisingly homogenous. In particular the iron abundance is almost solar for most sdBs. We highlight one iron deficient and three super metal-rich sdBs, a challenge to diffusion theory. SdB stars are slowly rotating stars unless they are in close binary systems which is hard to understand if the sdB stars were formed in merger events. The only exception is the pulsator PG 1605+072 rotating at v sin i = 39km/s. Signatures of stellar winds from sdB stars have possibly been found.

To appear in "Extreme Horizontal Branch Stars and Related Objects", Astrophysics and Space Science, Kluver Academic Publishers, edited by P.F.L. Maxted

References in corpus (6)

• The origin of sdB stars (II)
• The binary fraction of extreme horizontal branch stars
• Spectral analysis of sdB stars from the Hamburg Quasar Survey
• HS 0705+6700: a new eclipsing sdB binary
• Binaries discovered by the SPY project I. HE 1047-0436: a subdwarf B + white dwarf system
• MSST observations of the pulsating sdB star PG1605+072

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• Hot subdwarf stars in close-up view I. Rotational properties of subdwarf B stars in close binary systems and nature of their unseen companions
• Mass-loss and diffusion in subdwarf B stars and hot white dwarfs: do weak winds exist?
• Hot subdwarf stars in close-up view - III. Metal abundances of subdwarf B stars
• Impact of helium diffusion and helium-flash-induced carbon production on gravity-mode pulsations in subdwarf B stars
• The Remarkable Be Star HD110432
• Gravitational settling in pulsating subdwarf B stars and their progenitors
• Time-series Spectroscopy and Photometry of the Pulsating Subdwarf B Star PG 1219+534 (KY UMa)
• NLTE spectroscopic analysis of the ${}^3$He anomaly in subluminous B-type stars