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A New Formation Mechanism for the Hottest Horizontal-Branch Stars

Allen V. Sweigart·Thomas M. Brown·Thierry Lanz·Wayne B. Landsman·Ivan Hubeny
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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.

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Allen V. Sweigart, Thomas M. Brown, Thierry Lanz, Wayne B. Landsman, Ivan Hubeny. 2002-07-16. A New Formation Mechanism for the Hottest Horizontal-Branch Stars. https://arxiv.org/abs/astro-ph/0207343

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