S320.12.02 — Quiescent and Flaring Lyman-alpha Radiation of Host Stars and Effects on Exoplanet Atmospheres

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Aug 14th at 10:50 AM until 11:02 AM

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Author(s): Jeffrey L Linsky4, Kevin France3, Yamila Miguel2, Lisa Kaltenegger1

Institution(s): 1. Cornell University, 2. Observatoire de la Cote d'Azur, 3. University of Colorado, 4. University ofColorado

Lyman-alpha radiation dominates the ultraviolet spectra of stars with spectral types G, K, and M, and is a major contributor to the photodissociation of important molecules including water, CO2, and CH4 in the upper atmospheres of exoplanets. We obtain intrinsic Lyman-alpha line fluxes for late-type stars by either correcting for interstellar absorption or by scaling from other spectroscopic observables and broadband fluxes. When stars flare, all emission lines brighten by large factors (Parke Loyd & France ApJS 211, 9 (2014)) as shown by HST spectra of G-M dwarf stars. We estimate the enhancement factors in the Lyman-alpha flux during M dwarf flares by scaling from the observed flux in C II and other UV emission lines. We then describe photochemical models of the atmosphere of the miniNeptune GJ 436b (Miguel et al. MNRAS 446, 345 (2015)) that show the effects of flaring Lyman-alpha fluxes on atmospheric chemical abundances.