Reference : Reconnaissance of the TRAPPIST-1 exoplanet system in the Lyman-α line
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/212096
Reconnaissance of the TRAPPIST-1 exoplanet system in the Lyman-α line
English
Bourrier, V. mailto [Observatoire de l'Université de Genève, 51 chemin des Maillettes, 1290, Sauverny, Switzerland]
Ehrenreich, D. [Observatoire de l'Université de Genève, 51 chemin des Maillettes, 1290, Sauverny, Switzerland]
Wheatley, P. J. [Department of Physics, University of Warwick, Coventry, CV4 7AL, UK]
Bolmont, E. [Laboratoire AIM Paris-Saclay, CEA/DRF - CNRS - Univ. Paris Diderot - IRFU/SAp, Centre de Saclay, 91191, Gif-sur-Yvette Cedex, France]
Gillon, Michaël mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa) >]
de Wit, J. [Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA]
Burgasser, A. J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA, 92093, USA]
Jehin, Emmanuel mailto [Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa) >]
Queloz, D. [Cavendish Laboratory, J J Thomson Avenue, Cambridge, CB3 0HE, UK; Observatoire de l'Université de Genève, 51 chemin des Maillettes, 1290, Sauverny, Switzerland]
Triaud, A. H. M. J. [Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK)]
1-Mar-2017
Astronomy and Astrophysics
EDP Sciences
599
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] planetary systems ; stars: individual: TRAPPIST-1 ; techniques: spectroscopic
[en] The TRAPPIST-1 system offers the opportunity to characterize terrestrial, potentially habitable planets orbiting a nearby ultracool dwarf star. We performed a four-orbit reconnaissance with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope to study the stellar emission at Lyman-α, to assess the presence of hydrogen exospheres around the two inner planets, and to determine their UV irradiation. We detect the Lyman-α line of TRAPPIST-1, making it the coldest exoplanet host star for which this line has been measured. We reconstruct the intrinsic line profile, showing that it lacks broad wings and is much fainter than expected from the stellar X-ray emission. TRAPPIST-1 has a similar X-ray emission as Proxima Cen but a much lower Ly-α emission. This suggests that TRAPPIST-1 chromosphere is only moderately active compared to its transition region and corona. We estimated the atmospheric mass loss rates for all planets, and found that despite a moderate extreme UV emission the total XUV irradiation could be strong enough to strip the atmospheres of the inner planets in a few billions years. We detect marginal flux decreases at the times of TRAPPIST-1b and c transits, which might originate from stellar activity, but could also hint at the presence of extended hydrogen exospheres. Understanding the origin of these Lyman-α variations will be crucial in assessing the atmospheric stability and potential habitability of the TRAPPIST-1 planets.
http://hdl.handle.net/2268/212096
10.1051/0004-6361/201630238
http://adsabs.harvard.edu/abs/2017A%26A...599L...3B

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