Observational evidence for helium production in stars - The helium abundance of hot subdwarfs, central stars of planetary nebulae, very massive O-stars and OBN-stars

Details Observational evidence for helium production in stars - The helium abundance of hot subdwarfs, central stars of planetary nebulae, very massive O-stars and OBN-stars Observational evidence for helium production in stars - The helium abundance of hot subdwarfs, central stars of planetary nebulae, very massive O-stars and OBN-stars

Feb 1983

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1983prhe.work..189k&link_type=abstract

IN: ESO Workshop on Primordial Helium, Garching, West Germany, February 2, 3, 1983, Proceedings (A83-50030 24-90). Garching, Wes

Computer Science

3

Abundance, Helium, Nuclear Fusion, O Stars, Photosphere, Stellar Evolution, Hot Stars, Planetary Nebulae, Stellar Atmospheres, Stellar Spectra, Subdwarf Stars

Scientific paper

The determination of helium abundances in the photospheres of O stars is discussed. A method is presented consisting of detailed analyses of high resolution visual and UV spectra using a complete non-LTE technique. A grid on non-LTE model atmospheres is computed and used for additional line formation calculations for He I and He II. A fit of the observed profiles of the hydrogen and helium lines yields the effective temperature, the gravity log, and the helium abundance. A final non-LTE model for these parameters is computed and used for detailed multilevel calculations for different metal ions to determine metal abundances by comparison of calculated and observed line strengths. Results are obtained for SdO stars, central stars of planetary nebulae, and very massive O and OBN stars. Evidence for stellar processing of helium is found for all these classes of objects.

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