Comparative white light flare activity of young and old planet hosting M dwarfs: AU Mic and Proxima Centauri

ABSTRACT

We present a comparative study of the white light flare activity of the young planet hosting M dwarf AU Mic and the old, fully convective planet hosting M dwarf Proxima Cen using Transiting Exoplanet Survey Satellite (TESS) photometry. We identified 249 flare events on AU Mic and 276 flare events on Proxima Cen. The relation between flare equivalent duration and total flare duration was modelled by the one-phase exponential association (OPEA) formalism. The OPEA parameters reveal a variability in both targets, while AU Mic shows higher Plateaus, which are calculated with both flare equivalent duration and flare energy, and a more persistently high flare frequency than Proxima Cen. As a secondary test, we searched for possible planet related modulation by examining the orbital phase dependence of flare occurrence rate, total equivalent duration rate, and median equivalent duration. After accounting for the TESS observing window and stellar rotational modulation, we find no robust enhancement of either the total flare occurrence or the total equivalent duration rates at the orbital phases of the known planets. The median equivalent duration distributions show phase-dependent signals at the adopted AU Mic d and Proxima Cen d periods; however, because these signals are not accompanied by enhancements in either the flare occurrence rate or the total equivalent duration rate, we regard them as suggestive rather than conclusive evidence for planet-related modulation.