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Massive Stars as Cosmic Engines Through the Ages

Published online by Cambridge University Press:  01 December 2007

André Maeder ,
Georges Meynet ,
Sylvia Ekström ,
Raphael Hirschi  and
Cyril Georgy
André Maeder
Affiliation:
Geneva Observatory, University of Geneva, CH–1290 Sauverny, Switzerland email: andre.maeder@obs.unige.ch, georges.meynet@obs.unige.ch, sylvia.ekstrom@obs.unige.ch, cyril.georgy@obs.unige.ch
Georges Meynet
Affiliation:
Geneva Observatory, University of Geneva, CH–1290 Sauverny, Switzerland email: andre.maeder@obs.unige.ch, georges.meynet@obs.unige.ch, sylvia.ekstrom@obs.unige.ch, cyril.georgy@obs.unige.ch
Sylvia Ekström
Affiliation:
Geneva Observatory, University of Geneva, CH–1290 Sauverny, Switzerland email: andre.maeder@obs.unige.ch, georges.meynet@obs.unige.ch, sylvia.ekstrom@obs.unige.ch, cyril.georgy@obs.unige.ch
Raphael Hirschi
Affiliation:
Astrophysics, EPSAM, University of Keele email: r.hirschi@epsam.keele.ac.uk
Cyril Georgy
Affiliation:
Geneva Observatory, University of Geneva, CH–1290 Sauverny, Switzerland email: andre.maeder@obs.unige.ch, georges.meynet@obs.unige.ch, sylvia.ekstrom@obs.unige.ch, cyril.georgy@obs.unige.ch
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Abstract

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Some useful developments in the model physics are briefly presented, followed by model results on chemical enrichments and WR stars. We discuss the expected rotation velocities of WR stars. We emphasize that the (C+O)/He ratio is a better chemical indicator of evolution for WC stars than the C/He ratios. With or without rotation, at a given luminosity the (C+O)/He ratios should be higher in regions of lower metallicity Z. Also, for a given (C+O)/He ratio the WC stars in lower Z regions have higher luminosities. The WO stars, which are likely the progenitors of supernovae SNIc and of some GRBs, should preferentially be found in regions of low Z and be the descendants of very high initial masses. Finally, we emphasize the physical reasons why massive rotating low Z stars may also experience heavy mass loss.

Keywords

stars: early-type – stars: Wolf-Rayet – stars: rotation – stars: mass loss
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S250: Massive Stars as Cosmic Engines , December 2007 , pp. 3 - 16
Copyright
Copyright © International Astronomical Union 2008

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