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Understanding The Disconnect between UV and White-Light Flares in Low-Mass M Stars

Presentation #203.01 in the session Habitability.

Published onJun 20, 2022
Understanding The Disconnect between UV and White-Light Flares in Low-Mass M Stars

Stellar flares are explosive phenomena that release radiation across the entire electromagnetic spectrum. The far-UV emission from flares can dissociate atmospheric species and exacerbate atmospheric erosion. Yet, the near-UV flux may be necessary for the emergence of life on rocky planets around low-mass stars such as Proxima Centauri, LHS 3384 and TRAPPIST-1. A detailed knowledge of the UV energies and rates of flares is therefore essential for our understanding of the habitability of M dwarf systems. However, measurements of UV flare rates can require expensive campaigns with space-based instruments, limiting such measurements to individual active stars. To get around this, habitability studies instead often use UV rates based on extrapolations from white-light studies with TESS. Despite their use in contemporary habitability studies, such extrapolations are untested and as such their accuracy remains unconstrained. To this end, we have combined TESS white-light and archival GALEX UV photometry for main sequence M dwarfs from TESS cycles 1 to 3 to test the UV predictions of habitability studies. We will show how white-light flare studies underestimate the UV rates of flares, what this tells us about the UV properties of flares from low-mass stars, and the impact our results have on our current understanding of the UV environments and habitability of terrestrial exoplanets around low-mass stars.

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