Coordinated X-Ray and Optical Observations of Star-Planet Interaction in HD 17156
Scandariato, G.; Pagano, I.; Sozzetti, A.; Lanza, A. F.; Maldonado, J.; Piotto, G.; Borsa, F.; Micela, G.; Sciortino, S.; Bonomo, A. S.; Claudi, R.; Desidera, S.; Cosentino, R.; Gratton, R.; Pillitteri, I.; Covino, E.; Maggio, A.
Italy, United States, Spain
Abstract
The large number of close-in Jupiter-size exoplanets prompts the question whether star-planet interaction (SPI) effects can be detected. We focused our attention on the system HD 17156, having a Jupiter-mass planet in a very eccentric orbit. Here we present results of the XMM-Newton observations and of a five month coordinated optical campaign with the HARPS-N spectrograph.10 We observed HD 17156 with XMM-Newton when the planet was approaching the apoastron and then at the following periastron passage, quasi-simultaneously with HARPS-N. We obtained a clear (≈ 5.5σ ) X-ray detection only at the periastron visit, accompanied by a significant increase of the {R}{HK}\prime chromospheric index. We discuss two possible scenarios for the activity enhancement: magnetic reconnection and flaring or accretion onto the star of material tidally stripped from the planet. In any case, this is possibly the first evidence of a magnetic SPI effect caught in action.