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Paper: The Pulsating Helium-rich Subluminous B Star LS IV-14°116
Volume: 462, Progress in Solar/Stellar Physics with Helio- and Asteroseismology
Page: 47
Authors: Jeffery, C. S.
Abstract: I review the properties of LS IV–14°116, a subluminous B (sdB) star with unusual pulsation properties and an unusual surface composition. As a low-amplitude variable, its apparent pulsation periods (1900 – 3000 s) are characteristic of g-mode pulsations in normal sdB stars, yet its effective temperature is typical of sdB stars which pulsate in short-period p-modes. In contrast to normal sdB stars, which are helium-deficient, its surface is moderately enriched in helium, and enormously enriched in yttrium, strontium, germanium and zirconium. It has been proposed that LS IV–14°116 is a proto-extended-horizontal-branch star, that the extreme surface composition can be explained by radiatively-driven diffusion sorting the surface chemistry as it evolves from a helium-enriched progenitor to a helium-poor sdB star, and that the g-mode pulsations are associated with an out-of-equilibrium structure caused by helium-shell flashes prior to core-helium burning. Asteroseismology will play a key rôle in testing these hypotheses.
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