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Among more than 450 extra solar planets yet discovered up to now, hot Jupiters class planets are the most interesting to study the interaction of star and planet at distances around 0.1 AU or less. Variations of chromospheric activity phased with the planet orbital period have been discovered in a few systems. The detection of star planet interaction in X-rays is matter of debate with statistical studies of different groups leading to opposite conclusions. I will present results from two observations of the hot Jupiter hosting system HD189733 obtained with XMM-Newton during planetary transits. We detect a softening and a large flare that could be consistent with an X-ray SPI scenario supported by MHD simulations. Furthermore, the non detection of the M-type companion in X-rays put a stringent limit on the age of the system and hint enhancement of X-ray activity in the primary star.