Pulsations driven by the ɛ-mechanism in post-merger remnants: First results
1 Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, 1900 La Plata, Argentina
2 CONICET, Paseo del Bosque s/n, 1900 La Plata, Argentina
3 Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, 85748 Garching, Germany
4 Armagh Observatory, College Hill, Armagh BT61 9DG, UK
5 School of Physics, Trinity College Dublin, Dublin 2, Ireland
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Helium-rich subdwarfs are a rare subclass of hot subdwarf stars which constitute a small and inhomogeneous group showing varying degrees of helium enrichment. Only one star, LS IV °14 116 has been found to show multiperiodic luminosity variations. The variability of LS IV °14 116 has been explained as the consequence of nonradial g-mode oscillations, whose excitation is difficult to understand within the frame of the standard κ-mechanism driving pulsations in sdBV stars. In a recent study, we have proposed that the pulsations of LS IV °14 116 might be driven through the ɛ-mechanism acting in unstable He-burning zones in the interior of the star, that appear before the quiescent He-burning phase. One of the few accepted scenarios for the formation of He-rich subdwarfs is the merger of two He-core white dwarfs. As part of this project, we present a study of the ɛ-mechanism in post-merger remnants, and discuss the results in the light of the pulsations exhibited by LS IV °14 116.
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