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Accueil > Séminaires > Lyman-alpha and Extreme-Ultraviolet (...)

Lyman-alpha and Extreme-Ultraviolet Emission from Exoplanet Host Stars

Jeff Linsky

The habitability of exoplanets likely depends on the presence of
such molecules as oxygen, ozone, water, methane, and carbon dioxide in
their atmospheres. Photoionization of these molecules is driven by the
far-ultraviolet radiation from host stars. The hydrogen Lyman-alpha
line dominates the far-ultraviolet spectra of solar-like and cooler dwarf
stars, but only a small fraction of the instrinsic stellar Lyman-alpha
radiation is observable from Earth because of interstellar absorption. I
will present several techniques for reconstructing the intrinsic
Lyman-alpha radiation of dwarf stars with spectral types F-M. The
extreme-ultraviolet radiation from host stars photoionizes hydrogen in
the atmospheres of exoplanets, heats the outer atmospheres, and drives
mass loss. Since most of the stellar EUV emission is absorbed by
interstellar gas, I will describe a new approach for estimating the EUV
emission of solar-type and cooler stars.