Helium abundances and the helium isotope anomaly of sdB stars

Details Helium abundances and the helium isotope anomaly of sdB stars Helium abundances and the helium isotope anomaly of sdB stars

2011-12-13

arxiv.org/abs/1112.2918v1

Astronomy and Astrophysics

Astrophysics

Solar and Stellar Astrophysics

7 pages, 4 figures, To appear in ASP Conference Series; Proceedings of the fifth meeting on hot subdwarf stars and related obj

Scientific paper

Helium abundances and atmospheric parameters have been determined from high resolution spectra for a new sample of 46 bright hot subdwarf B (sdB) stars. The helium abundances have been measured with high accuracy. We confirm the correlation of helium abundance with temperature and the existence of two distinct sequences in helium abundance found previously. We focused on isotopic shifts of helium lines and found helium-3 to be strongly enriched in 8 of our programme stars. Most of these stars cluster in a small temperature range between 27000 K and 31000 K very similar to the known helium-3-rich main sequence B stars, which cluster at somewhat lower temperatures. This phenomenon is most probably related to diffusion processes in the atmosphere, but poses a challenge to diffusion models.

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