The solar-exoplanet-host-star connection: measurements, reconstruction, and estimates of the UV, Lyman-alpha, and EUV radiation emitted by exoplanet host stars
Abstract
One of the important ways in which host stars influence their exoplanets is through photochemistry in their atmospheres. For example, the photodissociation of such important molecules in exoplanet atmospheres as H2O, CO2, and CH4 is primarily controlled by Lymanalpha and FUV radiation from the host stars.
Photochemistry of oxygen and ozone is controlled by NUV radiation. EUV radiation photoionizes H and other atoms, heats the outer atmospheres, and thereby drives mass loss from exoplanets. Photodissociation of H2O and CO2 liberates oxygen without the need for life forms and thus complicates the use of oxygen and ozone as biosignatures. The COS instrument on HST has now obtained UV spectra of a number of M dwarfs host stars. The Lyman-alpha line, which is important for G stars but completely dominates the UV emission of M dwarfs, is attenuated by interstellar absorption. I will present techniques for reconstructing or estimating the stellar emission in this line. The EUV emission can be estimated by comparison with Lymanalpha and other emission lines. These recent developments now make it feasible to evaluate the radiation received by exoplanets and to compute realistic models of the chemistry of exoplanet atmospheres.- Publication:
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Search for Life Beyond the Solar System. Exoplanets, Biosignatures & Instruments
- Pub Date:
- March 2014
- Bibcode:
- 2014ebi..confP2.35L