Flare frequency in M dwarfs belonging to Young Moving Groups

Abstract

Context. M stars are preferred targets for studying terrestrial exoplanets, for which we hope to obtain their atmosphere spectra in the next decade. However, M dwarfs have long been known for strong magnetic activity and the ability to frequently produce optical, broadband emission flares. Aims. We aim to characterise the flaring behaviour of young M dwarfs in the temporal, spectral, and energetic dimensions, as well as examine the stellar parameters governing this behaviour, in order to improve our understanding of the energy and frequency of the flare events capable of shaping the exoplanet atmosphere. Methods. Young Moving Group (YMG) members provide a unique age-based perspective on stellar activity. By examining their flare behaviour in conjunction with rotation, mass, and H{\alpha} data, we obtain a comprehensive understanding of flare activity drivers in young stars. Results. We demonstrate that young stars sharing similar stellar parameters can exhibit a variety in flare frequency distributions and that the flare behaviour shows indications of difference between optical and far-UV. We propose that the period of rotation, not the age of the star, can be a good proxy for assessing flaring activity. Furthermore, we recommend that instead of a simple power law for describing the flare frequency distribution, a piecewise power law be used to describe mid-size and large flare distributions in young and active M dwarfs. Conclusions. Using known periods of rotation and fine-tuned power laws governing the flare frequency, we can produce a realistic sequence of flare events to study whether the atmosphere of small exoplanets orbiting M dwarf shall withstand such activity until life can emerge.