2010A&A...522A..29L

Repeated observations of exoplanet transits allow us to refine the planetary parameters and probe them for any time dependent variations. In particular deviations of the period from a strictly linear ephemeris, transit timing variations (TTVs), can indicate the presence of additional bodies in the planetary system. Our goal was to reexamine the largely unstudied OGLE2-TR-L9 system with high cadence, multi-color photometry in order to refine the planetary parameters and probe the system for TTVs. We observed five full transits of OGLE2-TR-L9 with the GROND instrument at the ESO/MPG 2.2m telescope at La Silla Observatory. GROND is a multichannel imager that allowed us to gather simultaneous light curves in the g', r', i', and z' filters. From our analysis we find that the semi-major axis and the inclination differ from the previously published values. With the newly observed transits, we were able to refine the ephemeris to 2454492.80008(±0.00014)+2.48553417(±6.4x10^–7)E. The newly derived parameters are a=0.0418±0.0015AU, r_p=1.67±0.05R_j, and inc=82.47°±0.12, differing significantly in a and inc from the previously published values. Within our data, we find indications for TTVs.