2013/07/23 by S. Geier, U. Heber, H. Edelmann +8 · 1 citation
Physics and Astronomy · #Abundance (ecology) #Astronomy #Astronomy and Astrophysical Research #Astrophysics #Atomic physics #Biology #Gamma-ray bursts and supernovae #Helium #Horizontal branch #Metallicity #O-type star #Physics #Spectral line #Stars #Stellar, planetary, and galactic studies #Subdwarf #Surface gravity #White dwarf #astro-ph.SR
paper · pdf · doi:10.1051/0004-6361/201322057
12 pages, A&A accepted
arxiv created 2013/07/23 · openalex publication_date 2013/09/01 · arxiv updated 2015/06/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/02
Atmospheric parameters and helium abundances of 44 bright subdwarf B stars have been determined. More than half of our sample \nconsists of newly discovered stars from the Edinburgh Cape survey. We showed that effective temperatures and surface gravities can \nbe derived from high resolution echelle spectra with sufficient accuracy. Systematic uncertainties have been determined by comparing \nthe parameters derived from the high resolution data with the ones derived from medium resolution spectra. Helium abundances have \nbeen measured with high accuracy. Besides the known correlation of helium abundance with temperature, two distinct sequences in \nhelium abundance have been confirmed. Significant isotopic shifts of helium lines due to an enrichment in 3He have been found in \nthe spectra of 8 subluminous B stars (sdBs). Most of these stars cluster in a small temperature range between 27 000K and 31 000K \nvery similar to the known 3He-rich main sequence B stars, which also cluster in such a small strip, but at different temperatures. Both \nthe helium sequences and the isotopic anomaly are discussed.