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Observational constraints on massive star evolution

Published online by Cambridge University Press:  26 May 2016

Philip Massey
Philip Massey*
Affiliation:
Lowell Observatory, 1400 West Mars Hill Rd., Flagstaff, AZ 86001, USA

Abstract

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In this paper, I discuss the observational quantities that are useful for judging the successes and failures of current massive star evolutionary theory. The galaxies of the Local Group can serve as important laboratories for providing these diagnostics, as their metallicities vary by a factor of ten. We find that the evolutionary tracks do a good job of matching the distribution of stars in the H-R diagram during the main-sequence phase. However, none of the models produce RSGs that are as cool and as bright as what is observed. The relative number of WC and WN stars is a strong function of metallicity, and the Padova and Geneva ‘normal mass-loss’ models do a reasonably good job of matching the observations at low metallicities, but predict too few WCs at higher metallicity. The ‘enhanced’ mass-loss models of the Geneva group do not match the observations at all. New data is providing excellent statistics on the number of RSGs in these nearby galaxies, and the number ratio of RSGs to WRs is also an extremely sensitive function of metallicity. None of the models reproduce the trend of the RSG/WR ratio with metallicity.

Type
Part 2. Interiors of Massive Stars
Information
Symposium - International Astronomical Union , Volume 212: A Massive Star Odyssey: From Main Sequence to Supernova , 2003 , pp. 316 - 324
Copyright
Copyright © Astronomical Society of the Pacific 2003 

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