Pulsations driven by the $\epsilon$-mechanism in post-merger remnants: first results

TL;DR

This paper investigates the potential of the $-mechanism to drive pulsations in post-merger helium-rich subdwarf remnants, offering insights into the pulsation behavior of stars like LS IV b014 116.

Contribution

It presents the first study of $$-mechanism driven pulsations in post-merger remnants, linking theoretical models with observed stellar variability.

Findings

$$-mechanism can excite pulsations in post-merger remnants.

Results support the hypothesis that LS IV b014 116's variability is driven by the $$-mechanism.

Post-merger models show potential for explaining helium-rich subdwarf pulsations.

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 $^\circ$14 116 has been found to show multiperiodic luminosity variations. The variability of LS IV $^\circ$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 $\kappa$-mechanism driving pulsations in sdBV stars. In a recent study, we have proposed that the pulsations of LS IV $^\circ$14 116 might be driven through the $\epsilon$-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 $\epsilon$-mechanism in post-merger remnants, and discuss the results in the light of the pulsations exhibited by LS IV $^\circ$14 116.