Fast Quasi-Periodic Pulsations in M Dwarf Flares Observed by TESS

Dozens of hypotheses for the origin of quasi-periodic pulsation (QPP) have been proposed, but limited observational data means that we are not yet able to test those hypotheses. QPPs with periods of seconds or minutes are commonly observed on the Sun, but the vast majority of QPPs observed on other stars have dominant periods in the range of tens to hundreds of minutes.

The TESS 20-second cadence mode, made available in Cycle 3, provides a new opportunity to examine the visible lightcurve morphology of flares at <1 minute resolution. This team requested that a number of nearby M dwarfs be targeted for 20-second coverage in TESS Cycle 3. Fifteen of these were observed in Sector 27, and 85 particularly large flares were found on five of the stars. We have identified 9 quasi-periodic pulsations in this sample with periods between 120 and 520 seconds. A few of the QPP events show rather unexpected behaviour, with either stable or intermittently varying amplitude, although the majority are classic QPP signals with the amplitude smoothly decaying in a few oscillation cycles. These observations suggest that the small number of examples of short-period extrasolar QPPs may be a selection effect of the relatively long observational cadence of previous surveys.