Pulsations in M dwarf stars

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 0.1–0.5 M⊙. We find the fundamental radial mode to be unstable due to an ε mechanism, caused by deuterium (D) burning for the young 0.1 and 0.2 M⊙ models, by non-equilibrium He3 burning for the 0.2 and 0.25 M⊙ models of 104 Myr and by a flux-blocking mechanism for the partially convective 0.4 and 0.5 M⊙ models once they reach the age of 500 Myr. The periods of the overstable modes excited by the D burning are in the range 4.2–5.2 h for the 0.1 M⊙ models and is of the order of 8.4 h for the 0.2 M⊙ models. The periods of the modes excited by He3 burning and flux blocking are in the range 23–40 min. 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.

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