Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2009-06-19
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
6 pages, 2 figures. To appear in "Hot And Cool: Bridging Gaps in Massive Star Evolution", C. Leitherer, Ph. D. Bennett, P. W.
Scientific paper
Massive stars can develop into tepid supergiants at several stages of their post main-sequence evolution, prior to core He-burning, on a blue loop, or close to the final supernova explosion. We discuss observational constraints on models of massive star evolution obtained from the analysis of a sample of Galactic supergiants and put them in the context of the cosmic abundance standard as recently proposed from the study of their OB-type progenitors (Z=0.014 for stars in the solar neighbourhood). High-precision abundance analyses for He and CNO, with uncertainties as low as ~10-20%, trace the transport efficiency of nuclear-processed material to the stellar surface, either by rotational mixing or during the first dredge-up. A mixing efficiency higher by a factor ~2 than predicted by current evolution models for rotating stars is indicated, implying that additional effects need to be considered in evolutionary models like e.g. the interplay of circulation and magnetic fields. Blue loops are suggested to extend to higher masses and to higher Teff than predicted by the current generation of stellar evolution models.
Firnstein Markus
Nieva Maria-Fernanda
Przybilla Norbert
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