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Wind anisotropy and stellar evolution

Published online by Cambridge University Press:  01 June 2008

Cyril Georgy ,
Georges Meynet  and
André Maeder
Cyril Georgy
Affiliation:
Geneva Observatory, University of Geneva, Maillettes 51 - CH 1290 Sauverny, Switzerland
Georges Meynet
Affiliation:
Geneva Observatory, University of Geneva, Maillettes 51 - CH 1290 Sauverny, Switzerland
André Maeder
Affiliation:
Geneva Observatory, University of Geneva, Maillettes 51 - CH 1290 Sauverny, Switzerland
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Abstract

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Mass loss is a determinant factor which strongly affects the evolution and the fate of massive stars. At low metallicity, stars are supposed to rotate faster than at the solar one. This favors the existence of stars near the critical velocity. In this rotation regime, the deformation of the stellar surface becomes important, and wind anisotropy develops. Polar winds are expected to be dominant for fast rotating hot stars.

These polar winds allow the star to lose large quantities of mass and still retain a high angular momentum, and they modify the evolution of the surface velocity and the final angular momentum retained in the star's core. We show here how these winds affect the final stages of massive stars, according to our knowledge about Gamma Ray Bursts. Computation of theoretical Gamma Ray Bursts rate indicates that our models have too fast rotating cores, and that we need to include an additional effect to spin them down. Magnetic fields in stars act in this direction, and we show how they modify the evolution of massive star up to the final stages.

Keywords

stars: evolutionstars: magnetic fieldsstars: mass lossgamma rays: bursts
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 4 , Issue S255: Low-Metallicity Star Formation: From the First Stars to Dwarf Galaxies , June 2008 , pp. 199 - 203
Copyright
Copyright © International Astronomical Union 2008

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