New parameters and transit timing studies for OGLE2-TR-L9 b*

Context. 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. Aims. 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. Methods. We observed five full transits of OGLE2-TR-L9 with the GROND instrument at the ESO/MPG 2.2 m 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. Results. 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 2 454 492.80008(±0.00014)+ 2.48553417(±6.4× 10−7 )E. The newly derived parameters are a = 0.0418± 0.0015 AU, rp = 1.67± 0.05 Rj, 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.