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Asteroseismic Constraints on Evolutionary Models of Hot Subdwarfs
Jan-Torge Schindler (Steward Observatory, Department of Astronomy, University of Arizona), Schindler, Jan-Torge (Steward Observatory, Department of Astronomy, University of Arizona), Arnett, W. David (Steward Observatory, Department of Astronomy, University of Arizona), Green, Elisabeth M. (Steward Observatory, Department of Astronomy, University of Arizona)
Hot subwarfs are helium core burning stars with very thin hydrogen envelopes located at the extreme horizontal branch. Many of these hot (Teff =20,000-40,000K) and compact (log g = 5.0-6.2) objects exhibit pressure(p)-mode (100-400s) and/or gravity(g)-mode (2000-14000s or longer) stellar pulsations. Pulsational frequencies in both regimes have been observed using ground-based and space-borne (e.g. CoRot and Kepler) instruments. Asteroseismic analyses of these p- and g-mode pulsations led to strong constraints on surface properties, such as effective temperature, gravitational acceleration and rotation, and inferences on the inner structure, convective core sizes and composition. In my talk I will give a general overview over these results and then focus on a comparison of the inner structure and the convective core with evolutionary models. Especially subdwarf B star convective core sizes inferred from asteroseismology (0.22-0.28 Msun, ~45% of the total mass) challenge our current implementation of convection in standard stellar evolution. On our road to a more accurate treatment of convection we turn towards three-dimensional simulations of turbulent convection in stars for further insight.