M dwarf search for pulsations within Kepler GO program

TL;DR

This study analyzed four M dwarf stars using Kepler data to detect intrinsic pulsations, but found no evidence of oscillations, suggesting such pulsations are either absent or too faint to observe with current methods.

Contribution

First observational search for M dwarf pulsations using Kepler short cadence data, testing theoretical predictions and setting upper limits on pulsation amplitudes.

Findings

No pulsations detected at a sensitivity of a few ppm.

Results imply pulsations, if present, have very low amplitudes.

Highlights the need for further observations and spectroscopic searches.

Abstract

We present the analysis of four M dwarf stars -plus one M giant that seeped past our selection criteria- observed in Cycle 3 of Kepler Guest Observer program (GO3) in a search for intrinsic pulsations. Stellar oscillations in M dwarfs were theoretically predicted by Rodr\'iguez-L\'opez et al. (2012) to be in the range ~20-40 min and ~4-8 h, depending on the age and the excitation mechanism. We requested Kepler short cadence observations to have an adequate sampling of the oscillations. The targets were chosen on the basis of detectable rotation in the initial Kepler results, biasing towards youth.The analysis reveals no oscillations attributable to pulsations at a detection limit of several parts per million, showing that either the driving mechanisms are not efficient in developing the oscillations to observable amplitudes, or that if pulsations are driven, the amplitudes are very low. The size of the sample, and the possibility that the instability strip is not pure, allowing the coexistence of pulsators and non-pulsators, prevent us from deriving definite conclusions. Inmediate plans include more M dwarfs photometric observations of similar precision with Kepler K2 mission and spectroscopic searches already underway within the Cool Tiny Beats Project (Anglada-Escud\'e et al. 2014, Berdi\~nas et al. 2014) with the high-resolution spectrographs HARPS and HARPS-N.