[seminar] Astro Journal Club on 1 June

[Oskari Miettinen]

Dear all,

Our Astro Journal Club will be held next Wednesday at 3:00 pm (sharp) in
the seminar room F-201 of the Physics Department. This time we will
discuss about a nearby ultracool dwarf star orbited by three Earth-sized
planets.

Presenter: Lovro Basioli
Paper title: Strong XUV irradiation of the Earth-sized exoplanets orbiting
the ultra cool dwarf TRAPPIST-1
Authors: Wheatley, P. J., Louden, T., Bourrier, V., et al.
Paper status: Submitted to MNRAS Letters

Summary:
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
Lx/Lbol=2-4x1e-4, with the total XUV emission in the range
Lxuv/Lbol=6-9x1e-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.

Link to the paper: http://adsabs.harvard.edu/abs/2016arXiv160501564W

See you all on Wednesday!

Cheers,
Oskari