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Paper: Helium Abundances and the Helium Isotope Anomaly of sdB Stars
Volume: 452, Fifth Meeting on Hot Subdwarf Stars and Related Objects
Page: 57
Authors: Geier, S.; Heber, U.; Edelmann, H.; Morales-Rueda, L.; Kilkenny, D.; O'Donoghue, D.; Marsh, T. R.; Copperwheat, C.
Abstract: 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 3He to be strongly enriched in 8 of our programme stars. Most of these stars cluster in a small temperature range between 27,000 K and 31,000 K very similar to the known 3He-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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