Abstract
The EUV (200–911 Å), FUV (912–1750 Å), and NUV (1750–3200 Å) spectral energy distribution of exoplanet host stars has a profound influence on the atmospheres of Earth-like planets in the habitable zone. The stellar EUV radiation drives atmospheric heating, while the FUV (in particular, Lyα) and NUV radiation fields regulate the atmospheric chemistry: the dissociation of H2O and CO2, the production of O2 and O3, and may determine the ultimate habitability of these worlds. Despite the importance of this information for atmospheric modeling of exoplanetary systems, the EUV/FUV/NUV radiation fields of cool (K and M dwarf) exoplanet host stars are almost completely unconstrained by observation or theory. We present observational results from a Hubble Space Telescope survey of M dwarf exoplanet host stars, highlighting the importance of realistic UV radiation fields for the formation of potential biomarker molecules, O2 and O3. We conclude by describing preliminary results on the characterization of the UV time variability of these sources.
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Acknowledgements
KF thanks Tom Ayres for assistance with STIS echelle spectra and enjoyable discussions about cool star spectroscopy. The data presented here were obtained as part of the HST Guest Observing program #12464 and the COS Science Team Guaranteed Time programs #12034 and #12035. fWe have enjoyed discussions with collaborators from the International Group with Astronomical Direction (IGwAD) organization. This work was supported by NASA grants HST-GO-12464.01 and NNX08AC146. We also thank the organizers of the “Challenges in UV Astronomy” meeting for an enjoyable conference.
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France, K., Linsky, J.L. & Parke Loyd, R.O. The ultraviolet radiation environment in the habitable zones around low-mass exoplanet host stars. Astrophys Space Sci 354, 3–7 (2014). https://doi.org/10.1007/s10509-014-1947-2
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DOI: https://doi.org/10.1007/s10509-014-1947-2