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The Brightest Carbon Stars

Cheryl Frost, Robert Cannon, John Lattanzio, Peter Wood, Manuel Forestini

astro-pharXiv:astro-ph/9710054

Abstract

It is currently accepted that Hot-Bottom-Burning (HBB) in intermediate-mass asymptotic giant branch (AGB) stars prevents the formation of C~stars. Nevertheless, we present in this paper the results of some detailed evolutionary calculations which show that even with HBB we obtain C~stars at the highest luminosities reached on the AGB. This is due to mass-loss reducing the envelope mass so that HBB ceases but dredge-up continues. The high mass-loss rate produces an optically thick wind before the star reaches C/O>1. This is consistent with the recent results of van Loon et al. (1997a,b) who find obscured C~stars in the Magellanic Clouds at luminosities up to Mbol = -6.8.

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