Strong XUV irradiation of the Earth-sized exoplanets orbiting the ultracool dwarf TRAPPIST-1

Peter J. Wheatley, Tom Louden, Vincent Bourrier, David Ehrenreich, Michaël Gillon
(Submitted on 5 May 2016)

We present an XMM-Newton X-ray observation of TRAPPIST-1, which is an ultracool dwarf star recently discovered to host three transiting and temperate Earth-sized planets. We find the star is a relatively strong and variable coronal X-ray source with an X-ray luminosity similar to that of the quiet Sun, despite its much lower bolometric luminosity. We find L_x/L_bol=2-4×10^-4, with the total XUV emission in the range L_xuv/L_bol=6-9×10^-4. Using a simple energy-limited model we show that the relatively close-in Earth-sized planets, which span the classical habitable zone of the star, are subject to sufficient X-ray and EUV irradiation to significantly alter their primary and perhaps secondary atmospheres. Understanding whether this high-energy irradiation makes the planets more or less habitable is a complex question, but our measured fluxes will be an important input to the necessary models of atmospheric evolution.

Comments: 5 pages, submitted as a letter to MNRAS
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1605.01564 [astro-ph.EP] (or arXiv:1605.01564v1 [astro-ph.EP] for this version)
Submission history
From: Peter J. Wheatley
[v1] Thu, 5 May 2016 12:01:30 GMT (44kb)
http://arxiv.org/abs/1605.01564