Schedule Oct 27, 2011
Evolutionary models for the asteroseismic study of subdwarf B stars
Steven Bloemen (K.U.Leuven)

Subdwarf stars of spectral type B are burning helium in the core and have only a very thin hydrogen layer left at the surface. Their formation is not well understood. We plan to derive stellar parameters for a sample of sdB stars using asteroseismic techniques and compare these to predictions of the various formation channels. Pure period-matching, i.e. simply matching observed periodicities with eigenfrequencies of the stellar models, cannot reveal the true nature of the sdBs under study. Additional information, such as the theoretical instability of the modes or mode identification, can help to break the degeneracy. We give an update on our efforts to compute an evolutionary grid of sdB models and their non-adiabatic oscillation properties. The stellar models include up-to-date input physics, such as OP opacities, atomic diffusion and radiative levitation, which is relevant for the oscillations (Hu et al. 2008, 2009 & 2010). We also use our grids to comment on the recent suggestion by Reed et al. (2011) that mode identification can be achieved by studying period spacings between modes observed by Kepler in a sample of g-mode pulsators.

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