Space Weather & Heliophysics

Extending Optical Flare Models to the UV: Results from Comparing of TESS and GALEX Flare Observations For M Dwarfs

By Keith Cowing
Press Release
November 1, 2022
Filed under , , , ,
Extending Optical Flare Models to the UV: Results from Comparing of TESS and GALEX Flare Observations For M Dwarfs
The best fitting predicted NUV flare rate for fully convective M stars. This uses an energy correction factor of 6.5 ± 0.7 times the NUV emission predicted by the 9000 K blackbody. The predicted NUV flare rate (in red) shares its slope with the fitted white-light flare rate. As discussed in Sect.4.3.1, the difference in slopes results in the predicted NUV rate underestimating the flare energies above 2 × 1031 erg. — astro-ph.SR

The ultraviolet (UV) emission of stellar flares may have a pivotal role in the habitability of rocky exoplanets around low-mass stars.

Previous studies have used white-light observations to calibrate empirical models which describe the optical and UV flare emission. However, the accuracy of the UV predictions of models have previously not been tested. We combined TESS optical and GALEX UV observations to test the UV predictions of empirical flare models calibrated using optical flare rates of M stars.

We find that the canonical 9000 K blackbody model used by flare studies underestimates the GALEX NUV energies of field age M stars by up to a factor of 6.5±0.7 and the GALEX FUV energies of fully convective field age M stars by 30.6±10.0. We calculated energy correction factors that can be used to bring the UV predictions of flare models closer in line with observations.

We calculated pseudo-continuum flare temperatures that describe both the white-light and GALEX NUV emission. We measured a temperature of 10,700 K for flares from fully convective M stars after accounting for the contribution from UV line emission. We also applied our correction factors to the results of previous studies of the role of flares in abiogenesis. Our results show that M stars do not need to be as active as previously thought in order to provide the NUV flux required for prebiotic chemistry, however we note that flares will also provide more FUV flux than previously modelled.

James A. G. Jackman, Evgenya Shkolnik, Chase Million, Scott Fleming, Tyler Richey-Yowell, Parke Loyd

Comments: 20 pages, 9 figures, 4 tables. Accepted for publication in the Monthly Notices of the Royal Astronomical Society
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2210.15688 [astro-ph.SR] (or arXiv:2210.15688v1 [astro-ph.SR] for this version)
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Submission history
From: James Jackman
[v1] Thu, 27 Oct 2022 18:00:04 UTC (1,345 KB)

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻