Astron. Astrophys. 319, 648-654 (1997)

Dust formation in winds of long-period variables

IV. Atmospheric dynamics and mass loss

S. Höfner and E.A. Dorfi

Institut für Astronomie der Universität Wien, Türkenschanzstraße 17, A-1180 Wien, Austria

Received 28 May 1996 / Accepted 21 August 1996

Abstract

We have calculated radiation-hydrodynamical models of the atmosphere and circumstellar dust shell of C-rich long-period variables which include a detailed description of the dust formation process. We discuss the time-dependent behaviour of the circumstellar envelope (e.g. multiperiodicity) and its relevance for observational properties like near-IR light curves and investigate the time-averaged mass loss characteristics of a sample of models satisfying radius-luminosity-mass and period-luminosity relations. The results can be summarized as follows: The dependence of the mass loss rate on stellar parameters predicts a strong increase of mass loss as stars evolve along the AGB. The models presented agree reasonably well with mean mass loss-period relations deduced from observations of Mira stars and the observed scatter of mass loss rates for a given period can be understood in terms of pulsation amplitude or non-linearities of the wind mechanism. The wind velocities show a good correlation with the quantity which characterizes the strength of radiation pressure on dust relative to gravitation.

Key words: stars: AGB and post-AGB stars: mass-loss stars: circumstellar matter stars: carbon hydrodynamics

Send offprint requests to: S. Höfner, Internet: hoefner@astro.ast.univie.ac.at

Contents

• 1. Introduction
• 2. Modelling method and parameters
• 3. Dynamics and periodicity
  • 3.1. Prototype models
  • 3.2. A random sample
  • 3.3. Influence on light curves
• 4. Mass loss
  • 4.1. Parameter dependence
  • 4.2. Comparison with observations
• 5. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998
helpdesk@link.springer.de