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The Evolution of AGB Stars

Published online by Cambridge University Press:  30 March 2016

P.R. Wood  and
E. Vassiliadis
P.R. Wood
Affiliation:
Mount Stromlo and Siding Spring ObservatoriesPrivate Bag, Weston Creek P.O. Canberra, ACT 2611Australia
E. Vassiliadis
Affiliation:
Mount Stromlo and Siding Spring ObservatoriesPrivate Bag, Weston Creek P.O. Canberra, ACT 2611Australia

Extract

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Computations of AGB stellar evolution which include the effects of mass loss are still relatively rare. However, in order to relate numbers of Mira variables, OH/IR stars and carbon stars to associated stellar populations, it is necessary to understand evolutionary timescales on the AGB.

The dominant factors controlling very late AGB evolution are shell flashes and mass loss, and some quantitative estimate of the latter is needed for stellar evolution calculations. The favoured mechanism for the production of the large mass loss rates observed in late AGB stars such as OH/IR stars and dust-enshrouded carbon stars, which have mass loss rates up to a few times 10−5 M⊙ yr−1 (see van der Veen and Rugers 1989 for a compilation), is a dual process involving the lévitation of matter above the photosphere by large-amplitude radial pulsation followed by the formation of grains on which radiation pressure acts to drive the circumstellar material away from the star (Castor 1981; Holzer and MacGregor 1985; Hearn 1990). The studies by Wood (1979) and Bowen (1988) show that, by themselves, neither pulsation nor radiation pressure acting on grains can produce the very large mass loss rates from AGB stars.

Type
Joint Commission Meetings
Information
Highlights of Astronomy , Volume 9: Highlights of Astronomy. As presented at the XXIst General Assembly of the IAU, 1991 , 1992 , pp. 617 - 619
Copyright
Copyright © Kluwer 1992

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