A New Formation Mechanism for the Hottest Horizontal-Branch Stars
Abstract
Stars with very large mass loss on the red-giant branch can undergo the helium flash while descending the white-dwarf cooling curve. Under these conditions the flash convection zone will mix the hydrogen envelope with the hot helium- burning core. Such ``flash-mixed'' stars will arrive on the extreme horizontal branch (EHB) with helium- and carbon-rich envelopes and will lie at higher temperatures than the hottest canonical (i.e., unmixed) EHB stars. Flash mixing provides a new evolutionary channel for populating the hot end of the EHB and may explain the origin of the high gravity, helium-rich sdO and sdB stars.
Cite
@article{arxiv.astro-ph/0207343,
title = {A New Formation Mechanism for the Hottest Horizontal-Branch Stars},
author = {Allen V. Sweigart and Thomas M. Brown and Thierry Lanz and Wayne B. Landsman and Ivan Hubeny},
journal= {arXiv preprint arXiv:astro-ph/0207343},
year = {2007}
}
Comments
2 pages, Latex, 1 figure. To appear in "New Horizons in Globular Cluster Astronomy", eds. G. Piotto, G. Meylan, G. Djorgovski, & M. Riello, ASP Conference Series