arXiv subjects

Cheryl Frost

Publications and source records attributed to Cheryl Frost.

3 recordsLinked to original sources

arXiv1998

Degenerate thermal pulses in AGB stars

We report on the discovery of a new kind of thermal pulse in intermediate mass AGB stars. Deep dredge-up during normal thermal pulses on the AGB leads to the formation of a long, unburnt tail to the helium profile. Eventually the tail ignites under partially degenerate conditions producing a strong shell flash with very deep subsequent dredge-up. The carbon content of the intershell convective region (X_C ~ 0.6) is substantially higher than in a normal thermal pulse (X_C ~ 0.25) and about 4 times more carbon is dredged-up than in a normal pulse.

astro-ph↗

arXiv1997

The Brightest Carbon Stars

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.

astro-ph↗

arXiv1996

AGB Stars: What Should Be Done ?

We present a review of AGB star evolution, with emphasis on the nucleosynthesis occurring in these stars. In particular, we discuss hot and cool bottom burning, observational constraints, and analysis of meteoritic grains. This paper was presented at the 32nd Liege Colloquium "Stellar Evolution: What Should Be Done ?"

astro-ph↗