  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 2454492.80008(+/-
0.00014) + 2.48553417(+/- 6.4) x 10^-7 E. The newly derived parameters are
a=0.0418 (+/- 0.0015) AU, r_p =1.67 (+/- 0.05) R_j, and inc=82.47{\deg} (+/-
0.12), differing significantly in a and inc from the previously published
values. Within our data, we find indications for TTVs.
