Statistical Properties of Quasi-Periodic Pulsations in White-Light Flares Observed With Kepler

TL;DR

This study analyzes quasi-periodic pulsations in white-light stellar flares observed by Kepler, finding that QPPs are likely caused by local processes and scale with decay time, similar to solar MHD oscillations.

Contribution

It provides the first large-scale statistical analysis of QPPs in stellar flares, revealing their independence from stellar parameters and potential link to MHD oscillations.

Findings

56 flares exhibit QPP signatures

QPP period correlates with decay time in Gaussian damping

No correlation between QPP period and stellar temperature or radius

Abstract

We embark on a study of quasi-periodic pulsations (QPPs) in the decay phase of white-light stellar flares observed by Kepler. Out of the 1439 flares on 216 different stars detected in the short-cadence data using an automated search, 56 flares are found to have pronounced QPP-like signatures in the light curve, of which 11 have stable decaying oscillations. No correlation is found between the QPP period and the stellar temperature, radius, rotation period and surface gravity, suggesting that the QPPs are independent of global stellar parameters. Hence they are likely to be the result of processes occurring in the local environment. There is also no significant correlation between the QPP period and flare energy, however there is evidence that the period scales with the QPP decay time for the Gaussian damping scenario, but not to a significant degree for the exponentially damped case. This same scaling has been observed for MHD oscillations on the Sun, suggesting that they could be the cause of the QPPs in those flares. Scaling laws of the flare energy are also investigated, supporting previous reports of a strong correlation between the flare energy and stellar temperature/radius. A negative correlation between the flare energy and stellar surface gravity is also found.