Stellar flares and habitability

How do stellar flares impact habitability?

Why care about flares? Because flares can impact habitability - they may erode exoplanets' atmospheres, but might also trigger the genesis of life. And all of this is especially important around M-dwarfs! To model flares, we use our public allesfitter code (Günther&Daylan, in prep.). It not only models exoplanets&binaries and red noise (with GPs), but also robustly selects the appropriate model for potentially complex flares via Bayesian evidence. Using Nested Sampling, we can compute the Bayes factors of diffferent models - pure noise, 1 flare, 2 flares, and so on. So what do we find? From the sample of 25,000 TESS objects we find 1200 flaring stars, 700 of which are M-dwarfs. Especially the mid M-dwarfs are `flary'. And one of the coolest (no pun intended) things: TESS explores so many bright early to late M-dwarfs! Of course, thanks to Kepler/K2/NGTS/MEarth/EVRYSCOPE and others we already learned some things about their flares - but TESS truly opens up new avenues here. Moreover, we find that fast rotating M-dwarfs are the most likely to flare, solidifying previous findings by other studies. And one of my personal favorites: the large amplitude flare on an M4.5 dwarf, raising the stellar brightness by a factor of 16! This goliath is even preceeded by a series of `warm-up' flares. Finally, we link all this flaring to prebiotic chemistry, coronal mass ejections, and ozone depletion. See Günther, M.N. et al., 2020.