UV flare statistics of Proxima Centauri

ODERT, P.; ABREVAYA, X.C.; LEITZINGER, M.

Krakow

Congreso; European Astronomical Society Annual Meeting (EAS 2023); 2023

European Astronomical Society

Proxima Centauri is an active flare star of spectraltype M5.5Ve which hosts an Earth-mass planet inits habitable zone. Stellar magnetic activity mayhave severe consequences for planets, as it inducesatmospheric loss processes, alters the atmosphericchemistry, and may affect the possibleorigin and evolution of life. Ultraviolet (UV)radiation is of special importance, not just becauseit is the main driver of photochemistry inthe atmosphere, but also because of its likely biologicaleffects (for instance, on simple life formssuch as microorganisms), as significant amountsof flux can reach the planetary surface even inthe presence of an atmosphere. Thus, to assessthe potential habitability of a planet, the hoststar’s UV emission, including flares, needs to bewell constrained. During stellar flares, UV emissionscan be enhanced by several orders of magnitude.Here we present UV flare statistics ofProxima Centauri from about 60 hours of observationsby XMM-Newton’s Optical Monitor (OM)instrument. The observations were conducted inthe U-band and were taken in fast mode with atime resolution of ten seconds. We detect about50 flares with peak flux enhancements larger than50% in these data. As the U-band filter approximatelycovers the UVA (300-400 nm) range, weextrapolate the peak fluxes and flare energies tothe UVC (200-280 nm) range using simple blackbodyflare models, as UVC radiation is of biologicalrelevance given that these wavelengths areparticularly harmful to life. Finally, we compareour results with published flare statistics in otherwavelength ranges.