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

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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 3

1 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 [FORMULA] - 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 [FORMULA]. Our models obtain relatively large [FORMULA] 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 [FORMULA] 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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© European Southern Observatory (ESO) 1997

Online publication: April 8, 1998
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