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Radial and nonradial oscillations of massive supergiants

Published online by Cambridge University Press:  12 July 2011

Hideyuki Saio
Hideyuki Saio*
Affiliation:
Astronomical Institute, Graduate School of Science, Tohoku University, Sendai, Miyagi 980-8578, Japan email: saio@astr.tohoku.ac.jp
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Abstract

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Stability of radial and nonradial oscillations of massive supergiants is discussed. The kappa-mechanism and strange-mode instability excite oscillations having various periods in wide ranges of the upper part of the HR diagram. In addition, in very luminous (log L/L⊙ ≳ 5.9) models, monotonously unstable modes exist, which probably indicates the occurrence of optically thick winds. The instability boundary is not far from the Humphreys-Davidson limit. Furthermore, it is found that there exist low-degree (ℓ = 1, 2) oscillatory convection modes associated with the Fe-opacity peak convection zone, and they can emerge to the stellar surface so that they are very likely observable in a considerable range in the HR diagram. The convection modes have periods similar to g-modes, and their growth-times are comparable to the periods. Theoretical predictions are compared with some of the supergiant variables.

Keywords

stars: oscillations (including pulsations)supergiantsinstabilitiesconvection
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S272: Active OB stars: structure, evolution, mass loss, and critical limits , July 2010 , pp. 468 - 473
Copyright
Copyright © International Astronomical Union 2011

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