Mapping the Landscape of M Dwarf X-ray Flares: New Discoveries in Context

We report the discovery of 11 X-ray flares from 7 M dwarfs previously unknown to exhibit flaring activity, by cross-matching eROSITA observations of bright, nearby M dwarfs with the Chandra telescope archive. To analyze the properties of these flares in a broader context, we compile the sample of all reported X-ray flares from the 15 M dwarfs identified as flaring in the literature. We use this combined sample to derive constraints on the X-ray flare frequency distributions of M0-M6 stars. The average flare occurrence rate we measure is ∼10^−1 ks^−1 (corresponding to ∼9 flares per day). The X-ray flares in this sample span energies from 10^29erg to 10^33erg and exhibit a strong correlation between flare strength and duration. The flare properties we characterize include their durations, flux and temperature enhancements, and temporal asymmetries. Using these results and recent simulations of flare-driven atmospheric escape, we derive an upper limit on the time required for habitable Earth-like planets orbiting these M dwarfs to completely lose their atmospheres: 0.5-30 Myr.