Astron. Astrophys. 354, 125-134 (2000)

Mass-loss rates and dust-to-gas ratios for obscured Asymptotic Giant Branch stars of different metallicities ^*

Jacco Th. van Loon

Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, United Kingdom

Received 8 July 1999 / Accepted 1 December 1999

Abstract

The mass-loss rates and dust-to-gas ratios of obscured Asymptotic Giant Branch (AGB) stars are investigated for samples with different initial metallicities: in the Small and Large Magellanic Clouds (SMC & LMC) and in the Milky Way. The properties of their circumstellar envelopes can be explained in a consistent way if, both for obscured M-type AGB stars and for obscured carbon stars, the total (gas+dust) mass-loss rate depends only weakly on initial metallicity whilst the dust-to-gas ratio depends approximately linearly on initial metallicity.

Key words: stars: circumstellar matter stars: mass-loss stars: AGB and post-AGB stars: winds, outflows galaxies: Magellanic Clouds infrared: stars

* This paper is based in part on data obtained at the South-African Astronomical Observatory.

Send offprint requests to: Jacco van Loon (jacco@ast.cam.ac.uk)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Formulae for dust-driven winds
• 3. Samples of obscured AGB stars
• 4. Relative mass-loss rates and dust-to-gas ratios
• 5. Discussion
  • 5.1. Metallicities of obscured AGB stars in the Magellanic Clouds and in the Milky Way
  • 5.2. Mass-loss rates and dust-to-gas ratios
  • 5.3. Obscured M-type AGB stars and carbon stars
• 6. Summary
• Acknowledgements
• Appendices
  • A: new near-IR counterparts of IRAS sources in the LMC
  • B: expansion velocities
• References

© European Southern Observatory (ESO) 2000

Online publication: January 31, 2000
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