Pulsations in M dwarf stars

TL;DR

This paper presents the first theoretical study of pulsations in M dwarf stars, identifying mechanisms that excite stellar oscillations and their potential observability based on stellar mass and age.

Contribution

It introduces a novel non-radial non-adiabatic pulsational analysis of M dwarf models, revealing excitation mechanisms and pulsation periods across different masses and ages.

Findings

Deuterium burning causes instability in 0.1-0.2 M_solar models.

He^3 burning excites modes in 0.2-0.25 M_solar models.

Flux blocking excites modes in 0.4-0.5 M_solar models after 500 Myr.

Abstract

We present the results of the first theoretical non-radial non-adiabatic pulsational study of M dwarf stellar models with masses in the range 0.1 to 0.5M_solar. We find the fundamental radial mode to be unstable due to an \epsilon mechanism caused by deuterium (D-) burning for the young 0.1 and 0.2M_solar models, by non-equilibrium He^3 burning for the 0.2 and 0.25M_solar models of 10^4Myr, and by a flux blocking mechanism for the partially convective 0.4 and 0.5M_solar models once they reach the age of 500Myr. The periods of the overstable modes excited by the D-burning are in the range 4.2 to 5.2h for the 0.1M_solar models and is of order 8.4h for the 0.2M_solar models. The periods of the modes excited by He^3 burning and flux blocking are in the range 23 to 40min. The more massive and oldest models are more promising for the observational detection of pulsations, as their ratio of instability e-folding time to age is more favourable.