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| Paper: |
HST/STIS Observations of sdBV Stars: Testing Diffusion and Pulsation Theory |
| Volume: |
310, Variable Stars in the Local Group (IAU Colloquium 193) |
| Page: |
234 |
| Authors: |
O'Toole, S.J.; Heber, U.; Chayer, P.; Fontaine, G.; O'Donoghue, D.; Charpinet, S. |
| Abstract: |
We present the initial results of an abundance analysis of echelle UV spectra of 5 hot subdwarf B (sdB) stars, which form part of a study to test pulsation and diffusion calculations. SdB stars have ben identified as core helium-burning objects on the extreme Horizontal Branch. Around 5% of sdB stars show short-period acoustic mode oscillations, which models predict are due to an opacity bump caused by the ionization of iron group elements. The necessary metal abundance has to be maintained by diffusive equilibrium between gravitational settling and radiative levitation. However, analyses of high resolution optical spectra has revealed that we cannot discriminate between pulsating and non-pulsating sdB stars on the basis of the surfaceiron abundance. Our initial analysis of HST/STIS observations of 3 pulsators and 2 non-pulsators in the near and far UV suggests this may also be the case for other iron group elements, although further work will be needed to verify this. |
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