X-ray irradiation Peter Wheatley and evaporation University of - PowerPoint PPT Presentation

X-ray irradiation Peter Wheatley and evaporation University of Warwick Contributors: Tom Louden, Vincent Bourrier, David Ehrenreich, Alain Lecavalier des Etangs

Exoplanet evaporation HD209458 Ly-alpha Vidal-Madjar et al 2003 HD189733 Lecavalier des Etangs et al 2010 Mass loss ~ 10 10 g s -1

Lammer et al. 2003 L x <= 10 -3 L bol

Energy-limited evaporation Lecavalier des Etangs 2007

Stellar X-ray emission Pizzolato ¡et ¡al ¡2003 ¡ ¡

Stellar X-ray emission Pizzolato ¡et ¡al ¡2003 ¡ ¡ Jackson, Davis & Wheatley 2012

Evaporation influencing giant planet evolution? Jackson, Davis & Wheatley 2012 Mass loss rate: Planet destruction limits:

Evolved giant planets

How efficient is the evaporation? Ehrenreich & Desert 2011

HD 209458b with XMM-Newton Kashyap ¡et ¡al ¡2008 ¡ Sanz-­‑Forcada ¡et ¡al ¡2011 ¡ Penz ¡et ¡al ¡2008 ¡

EUV flux via high-excitation lines in the UV HST COS spectrum of HD209458 Linsky et al 2010 EUV emission similar to quiet Sun L EUV = 9 x 10 27 erg/s X-ray emission is lower than quiet Sun L X < 3 x 10 26 erg/s Energy limited mass loss = 10 x 10 10 g/s at 100% efficiency c.f. 8 x 10 10 g/s lower limit from the same COS data

Evaporation efficiency of GJ436b Ehrenreich, ¡Bourrier, ¡Wheatley ¡et ¡al, ¡2015 ¡ 1 MK + 8 MK XMM and Chandra spectra Mark Garlick/Warwick

Evaporation efficiency of GJ436b Ehrenreich, ¡Bourrier, ¡Wheatley ¡et ¡al, ¡2015 ¡ Mass loss ~ 5 x 10 8 g/s XMM Chandra Requires only ~1% 1 MK (EUV/X-ray) efficiency (assuming EUV scaling of Chadney+15) 1 MK + 8 MK During 1 Gyr of saturated 8 MK (X-rays) X-ray emission may have XMM and Chandra spectra lost 10% of initial mass Mark Garlick/Warwick

HD189733b: variable atmospheric escape Lecavelier des Etangs, Bourier, Wheatley et al, 2012 April 2010 Sept2011 HST Mass loss ~ 10 9 g s -1 Swift XRT Sept 2011

X-ray transit observations with Chandra & XMM-Newton Poppenhaeger, Schmitt & Wolk 2013

Poppenhaeger, Schmitt, & Wolk 2013

Summary • Many hot Earths are probably evolved giant planets • Very different evaporation efficiencies in different planets – HD209458b highly efficient, >80% – GJ436b much less efficient, ~1% – Both are simultaneous measurements of irradiation and mass loss • HD189733b – mass loss is episodic – appears to be influenced by stellar flares – X-ray coverage helps disentangle activity from absorption • X-ray transit of HD189733b not yet confirmed Mark Garlick/Warwick