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 M_{bol} = -6.8.
@article{arxiv.astro-ph/9710054,
title = {The Brightest Carbon Stars},
author = {Cheryl Frost and Robert Cannon and John Lattanzio and Peter Wood and Manuel Forestini},
journal= {arXiv preprint arXiv:astro-ph/9710054},
year = {2007}
}
Comments
4 pages, 2 figures included. Note that these are quality-reduced figures for net transmission. If you want best quality figures, these are available from http://www.maths.monash.edu.au/~johnl/preprints/preprints.html