Short-term stellar activity in dM stars

We selected a volume-limited sample of M dwarfs within 10pc from Earth from the Gaia DR3 catalog. We analyzed TESS light curves using an iterative Gaussian process fitting technique to remove long-term stellar activity signals, enabling the identification and characterization of impulsive flare events. For each flare, we derived the amplitudes, timescales, and total energy emitted.

We analyzed 173 stars and detected 17229 flares, with 0 to 76 flares per TESS sector. We examined the frequency and energy distribution of stellar flares using three representative stars to illustrate the diversity in flare activity. We observed flares with a minimum energy of ~10^29^erg and typical durations ranging from 2 to 8000 seconds.

We modeled the cumulative flare energy distribution using one-slope and two-slope fits, yielding average slopes of -0.79+/-0.64 and -1.23+/-1.32, respectively. We defined the Flare Energy Index (GF.01) to characterize the flare frequency and revealed two distinct populations. Fainter stars exhibited fewer high-energy flares, whereas brighter stars exhibited more frequent low-energy flares.

We analyzed two highly active stars with the largest number of TESS sectors, G 227-22 and G 258-33, were analyzed over a long time baseline to explore their flare properties and energy distributions.