Transit timing variations at TrES-2?

The deviations to both sides of zero could be a first indication of timing anomalies caused by additional planets or moons. We will continue observing TrES-2 to confirm these transit time variations. Therefore, we work on methods to improve the accuracy of our transit times.

Abstract wrote:We report a possible change in the orbit parameters of the TrES-2 exoplanet. With a period of 2.470621 days, the TrES-2 exoplanet exhibits almost "grazing" transits 110.4 minutes duration as measured in 2006 by Holman and collaborators. We observed two transits of TrES-2 in 2008 using the 1.2m Oskar-Luhning telescope (OLT) of Hamburg observatory employing CCD photometry in an i-band and a near to R-band filter. A careful light curve analysis including a re-analysis of the 2006 observations shows that the current transit duration has shortened since 2006 by ~ 3.16 minutes. Although the new observations were taken in a different filter we argue that the observed change in transit duration time cannot be attributed to the treatment of limb darkening. If we assume the stellar and planetary radii to be constant, a change in orbit inclination is the most likely cause of this change in transit duration.

On June 15, 2009 UT the transit of TrES-2b was detected using the University of Arizona's 1.55 meter Kuiper Telescope with 2.0-2.5 millimag RMS accuracy in the I-band. We find a central transit time of T_c = 2454997.76286 +/- 0.00035 HJD, an orbital period of P = 2.4706127 +/- 0.0000009 days, and an inclination angle of i = 83.92 +/- 0.05 degrees, which is consistent with our re-fit of the original I-band light curve of O'Donovan et al. (2006) where we find i = 83.84 +/- 0.05 degrees. We calculate an inclination change of Delta i = -0.08 +/- 0.071 degrees over the last 3 years, and as such, our observations rule out, at the ~11 sigma level, the apparent change of orbital inclination to i_predicted = 83.35 +/- 0.1 degrees as predicted by Mislis & Schmitt (2009) for our epoch. Indeed, we detect no significant changes in any of the orbital parameters of TrES-2b when comparing the original I-band light curve to our recent I-band light curve.