X-ray irradiation and mass-loss of the hot Jupiter WASP-43 b

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 approximate to 130 M-circle plus, yielding a heavy-element mass-fraction of 20%. From an 18 ks long XMM-Newton observation, we derive an X-ray luminosity of 6.7(-3.3)(+3.5) x 10(27) ergs s(-1), 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) x 10(3) erg cm(-2) s(-1) 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 approximate to 10(12) g s(-1) 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.