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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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