X-ray activity phased with planet motion in HD 189733?
  We report on the follow-up XMM-Newton observation of the planet-hosting star HD 189733 we obtained in April 2011. We observe a flare just after the secondary transit of the hot Jupiter. This event shares the same phase and many of the characteristics of the flare we observed in 2009. We suggest that a systematic interaction between planet and stellar magnetic fields when the planet passes close to active regions on the star can lead to periodic variability phased with planetary motion. By mean of high resolution X-ray spectroscopy with RGS we determine that the corona of this star is unusually dense. 
I. Pillitteri, H. M. Guenther, S. J. Wolk, V. Kashyap, O. Cohen
astro-ph.SR