Astron. Astrophys. 327, 224-230 (1997)

Pulsations in red supergiants with high L/M ratio

Implications for the stellar and circumstellar structure
of supernova progenitors

A. Heger ^{1, 2}, L. Jeannin ³, N. Langer ^{1, 4} and I. Baraffe <sup>3

1</sup> Max-Planck-Institut für Astrophysik, D-85740 Garching, Germany
² UCO/LICK Observatory, University of California, Santa Cruz, CA 95064, USA
³ Centre de Recherche Astronomique de Lyon (UMR 5574, CNRS), Ecole Normale Supérieure de Lyon, 46 allée d'Italie, F-69364 Lyon Cedex 07, France
⁴ Institut für Theoretische Physik und Astrophysik, Universität Potsdam, D-14415 Potsdam, Germany

Received 21 March 1997 / Accepted 23 May 1997

Abstract

We investigate the pulsational properties of RSG models - which we evolve from ZAMS masses in the range 10 to - by means of linear and non-linear calculations. We find period and growth rate of the dominant fundamental mode to increase with increasing luminosity-to-mass ratio . Our models obtain relatively large values due to the inclusion of rotation in the evolutionary calculations; however, the largest values are obtained at and beyond central He-exhaustion due to major internal rearrangements of the nuclear burning regions. Our non-linear calculations as well as the behavior of the linear period and growth rate of the pulsations for periods approaching the Kelvin-Helmholtz time scale of the H-rich stellar envelope point towards the possibility of large amplitude pulsations. Such properties are similar to those found in AGB stars and suggest the possibility of a "superwind" to occur before the RSGs explode as supernovae. We conclude that changes in global stellar properties during the last few before core collapse may lead to drastic changes in the pulsational and wind properties of pre-supernova stars, with marked consequences for the immediate pre-supernova structure of the star and the circumstellar medium. We compare our results with observations of long-period OH/IR variables and discuss observational evidence for our scenario from observed supernova light curves, spectra and remnants.

Key words: stars: AGB and post-AGB - stars: oscillations - stars: AGB supernovae - supergiants

Send offprint requests to: A. Heger (ahg@mpa-garching.mpg.de)

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Contents

• 1. Introduction
• 2. Stellar evolutionary models
• 3. Linear stability analysis
• 4. Non-linear computation of the pulsations
• 5. Discussion
• 6. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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