Transit Timing Variations of TrES-2: a combined analysis of ground- and space-based photometry

TrES-2 is one of the few exoplanets, which offer the matchless possibility to combine long-term ground-based observations with continuous satellite data. TrES-2 is a target of our "Transit Timing Variations @ YETI" (TTV@YETI) project which is dedicated to detect and characterize signals of transit timing variations. We observed 43 ground-based light curves of 30 individual transit events of TrES-2. We used seven 0.2 - 2.2m telescopes located at five observatories in Germany and Spain. In addition, we analyzed 16 quarters (Q0-Q15) of observational data from NASA's space telescope Kepler including 424 individual transit events. The continuous monitoring of Kepler allows to determine the system parameters of each of the 424 transits and search for possible changes of these quantities. Here we present a first indication of an increasing stellar activity of the TrES-2 host star and provide new limits on possible transit timing variations.

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