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Nonlinear Pulsations of Luminous Blue Variables

Published online by Cambridge University Press:  12 April 2016

Ernst A. Dorfl ,
Michael U. Feuchtinger  and
Alfred Gautschy
Ernst A. Dorfl
Affiliation:
Institut für Astronomie, Universität Wien, Türkenschanzstraβe 17, A-1180 Wien, Austria
Michael U. Feuchtinger
Affiliation:
Physics Department, University of Florida, PO Box 118440, Gainesville, 32611, USA
Alfred Gautschy
Affiliation:
Astronomisches Institut der Universität Basel, Venusstrasse 7, CH-4102 Binningen, Switzerland

Abstract

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We present the results of various nonlinear radial pulsation calculations of LBVs with different luminosity to mass ratios. Depending on the stellar parameters, most of these objects undergo strongly non-adiabatic pulsations which can also modify their stellar atmospheres. In some cases part of the kinetic energy of the motions is transferred by shock waves into the atmospheric layers leading to an overall decrease or increase of the stellar radius. This results in different mean density accompanied by a change of the pulsational behavior which can be compared to the results of a linear stability analysis. We also find that regular pulsations can occur around a different equilibrium than the initial configuration which has been determined by stellar evolution calculations. In cases of even higher luminosity to mass ratios the linear stability analysis predicts several unstable modes and the nonlinear computations can exhibit rather irregular light curves. Due to the large non-adiabaticity of the pulsation the corresponding velocity curves still remain more regular, but show increasing amplitudes until the energy stored is released. The pulsations are far from equilibrium conditions and may also lead to a pulsationally driven mass loss for certain stellar parameters.

Type
Part 2. Variability of High-Luminosity Stars
Information
International Astronomical Union Colloquium , Volume 176: The Impact of Large-Scale Surveys on Pulsating Star Research , 2000 , pp. 109 - 112
Copyright
Copyright © Astronomical Society of the Pacific 2000

References

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