2013A&A...560A..17C

We report the X-ray detection of the low-mass K7V star WASP-43, which is orbited by a hot Jupiter in one of the closest exoplanet orbits known to date. The high mean density of the planet implies a massive core with ≃130M_⊕, yielding a heavy-element mass-fraction of 20%. From an 18ks long XMM-Newton observation, we derive an X-ray luminosity of 6.7^+3.5_–3.3x10²⁷ergs/s, which puts WASP-43 among the active K-stars, which is compatible with its relatively young age derived in previous studies. The X-ray luminosity translates into a soft X-ray flux of (10.2±5.4)x10³erg/cm2/s at the substellar point. According to our modeling, the combined X-ray and extreme ultraviolet flux may trigger mass-loss at a rate of up to ≃10¹²g/s via energy-limited atmospheric escape. We infer that it is unlikely that the planet has lost more than 2.5% of its current mass through that channel and that activity-induced mass-loss has not substantially altered its evolution.