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The Evolutionary State of the Cool Hypergiants – Episodic Mass Loss, Convective Activity and Magnetic Fields

Published online by Cambridge University Press:  01 December 2007

Roberta M. Humphreys
Roberta M. Humphreys*
Affiliation:
Astronomy Dept., University of Minnesota, 116 Church St. SE., Minneapolis, MN 55455, USA email: roberta@umn.edu
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Abstract

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The evolved cool stars near the empirical upper luminosity boundary in the HR Diagram all show evidence for considerable instability perhaps due to their proximity to this stability limit and/or their evolutionary state. Recent high resolution imaging and spectroscopy of several of these stars have revealed a subset characterized by complex ejecta and evidence for episodic mass loss driven by convective activity and magnetic fields. This group includes famous stars such as the red supergiants VY CMa, NML Cyg and the post RSG IRC +10420. I will review the observational evidence and discuss the implications for the final stages of these evolved stars, their mass loss mechanism, and evolutionary state.

Keywords

stars: mass loss – stars: magnetic fields – stars: evolution
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 3 , Symposium S250: Massive Stars as Cosmic Engines , December 2007 , pp. 111 - 118
Copyright
Copyright © International Astronomical Union 2008

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