2002/12/11 by P. Marigo, Marigo, P.
Physics and Astronomy · #Astrophysics (astro-ph) #FOS: Physical sciences #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/0212261
6 pages, 5 postscript figures, proceedings of contributed talk at the St. Luc conference ``CNO in the Universe'', eds. C. Charbonnel, D. Schaerer, & G. Meynet, to be published in the ASP Conference Series
arxiv created 2002/12/11 · arxiv updated 2009/12/01
This study calls attention to the importance of properly coupling the molecular opacities to the actual surface abundances of TP-AGB stars that experience the third dredge-up and/or hot-bottom burning, i.e. with surface abundances of carbon and oxygen varying with time. New TP-AGB calculations with variable opacities -- replacing the usually adopted solar-scaled opacity tables -- have proven to reproduce, for the first time, basic observables of carbon stars, like their effective temperatures, C/O ratios, and near-infrared colours. Moreover, it turns out that the effect of envelope cooling -- due to the increase in molecular opacities -- may cause other important effects, namely: i) shortening of the C-star phase; ii) possible reduction or shut-down of the third dredge-up in low-mass carbon stars; and iii) weakening or even extinction of hot-bottom burning in intermediate-mass stars.