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

^a e-mail: mmiller@fcaglp.unlp.edu.ar

Abstract

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.