Hot subdwarf stars in close-up view IV. Helium abundances and the 3He isotopic anomaly of subdwarf B stars
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Date
2013
Journal Title
Journal ISSN
Volume Title
Publisher
EDP Sciences
Abstract
Atmospheric parameters and helium abundances of 44 bright subdwarf B stars have been determined. More than half of our sample
consists of newly discovered stars from the Edinburgh Cape survey. We showed that effective temperatures and surface gravities can
be derived from high resolution echelle spectra with sufficient accuracy. Systematic uncertainties have been determined by comparing
the parameters derived from the high resolution data with the ones derived from medium resolution spectra. Helium abundances have
been measured with high accuracy. Besides the known correlation of helium abundance with temperature, two distinct sequences in
helium abundance have been confirmed. Significant isotopic shifts of helium lines due to an enrichment in 3He have been found in
the spectra of 8 subluminous B stars (sdBs). Most of these stars cluster in a small temperature range between 27 000K and 31 000K
very similar to the known 3He-rich main sequence B stars, which also cluster in such a small strip, but at different temperatures. Both
the helium sequences and the isotopic anomaly are discussed.
Description
Keywords
Stars, Astronomy, Atmospheres, Helium, Subdwarf stars
Citation
Geier, S. et al (2013). Hot subdwarf stars in close-up view: IV. Helium abundances and the 3He isotopic anomaly of subdwarf B stars. Astronomy & Astrophysics, 557: A122