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Luminous Blue Variables & Mass Loss near the Eddington Limit

Published online by Cambridge University Press:  01 December 2007

Stan Owocki  and
Allard Jan van Marle
Stan Owocki
Affiliation:
Bartol Research Institute, Department of Physics & AstronomyUniversity of Delaware, Newark, DE 19350USA email: owocki@bartol.udel.edu, marle@udel.edu
Allard Jan van Marle
Affiliation:
Bartol Research Institute, Department of Physics & AstronomyUniversity of Delaware, Newark, DE 19350USA email: owocki@bartol.udel.edu, marle@udel.edu
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Abstract

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During the course of their evolution, massive stars lose a substantial fraction of their initial mass, both through steady winds and through relatively brief eruptions during their Luminous Blue Variable (LBV) phase. This talk reviews the dynamical driving of this mass loss, contrasting the line-driving of steady winds to the potential role of continuum driving for eruptions during LBV episodes when the star exceeds the Eddington limit. A key theme is to emphasize the inherent limits that self-shadowing places on line-driven mass loss rates, whereas continuum driving can in principle drive mass up to the “photon-tiring” limit, for which the energy to lift the wind becomes equal to the stellar luminosity. We review how the “porosity” of a highly clumped atmosphere can regulate continuum-driven mass loss, but also discuss recent time-dependent simulations of how base mass flux that exceeds the tiring limit can lead to flow stagnation and a complex, time-dependent combination of inflow and outflow regions. A general result is thus that porosity-mediated continuum driving in super-Eddington phases can explain the large, near tiring-limit mass loss inferred for LBV giant eruptions.

Keywords

stars: early-type – stars: windsoutflows – stars: mass loss – stars: activity
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S250: Massive Stars as Cosmic Engines , December 2007 , pp. 71 - 82
Copyright
Copyright © International Astronomical Union 2008

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