Temporal Evolution of the High-energy Irradiation and Water Content of TRAPPIST-1 Exoplanets

@article{Bourrier2017TemporalEO,
  title={Temporal Evolution of the High-energy Irradiation and Water Content of TRAPPIST-1 Exoplanets},
  author={Vincent Bourrier and Julien de Wit and {\'E}meline Bolmont and Vlada Stamenkovi{\'c} and Peter J. Wheatley and Adam J. Burgasser and Laetitia Delrez and B-O. Demory and David Ehrenreich and Micha{\"e}l Gillon and Emmanuel Jehin and J{\'e}r{\'e}my Leconte and Susan M. Lederer and Nikole Lewis and A. H. M. J. Triaud and Val{\'e}rie Van Grootel},
  journal={The Astronomical Journal},
  year={2017},
  volume={154}
}
The ultracool dwarf star TRAPPIST-1 hosts seven Earth-size transiting planets, some of which could harbor liquid water on their surfaces. Ultraviolet observations are essential to measuring their high-energy irradiation and searching for photodissociated water escaping from their putative atmospheres. Our new observations of the TRAPPIST-1 Lyα line during the transit of TRAPPIST-1c show an evolution of the star emission over three months, preventing us from assessing the presence of an extended… 
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Observations of the combined transmission spectrum of the two inner planets during their simultaneous transits on 4 May 2016 rule out cloud-free hydrogen-dominated atmospheres for each planet at ≥10σ levels; TRAPPIST-1 b and c are therefore unlikely to have an extended gas envelope as they occupy a region of parameter space in which high-altitude cloud/haze formation is not expected to be significant for hydrogen- dominated atmospheres.
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