GCN Circular 8812

F. Olivares (MPE Garching), Andrea Rossi (Tautenburg Obs.), J. Greiner,
A. Yoldas (both MPE Garching), and A. Kupcu Yoldas (ESO) report on behalf
of the GROND team:

We observed the field of GRB 090113 (Swift trigger #339852; Krimm et al.,
GCN #8804) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008,
PASP 120, 405) mounted at the 2.2m MPI/ESO telescope at La Silla
Observatory (Chile).

Observations started at 00:35 UT on January 14th, 2009, about 6.1 hrs after
the GRB trigger, and continued until the GRB location approached the 20 degree
above horizon limit of the telescope, with 8.1 min of total exposures in
g'r'i'z' and 12.0 min in JHK. They were performed at an average seeing of 1.8"
and at an average airmass of 2.6.

We do not detect any object within the 1.7'' Enhanced Swift-XRT error circle
reported by Goad et al. (GCN #8809). Co-added images yield the following
upper limits (all in AB system):

g' >  23.3 mag,
r' >  23.4 mag,
i' >  22.6 mag,
z' >  22.6 mag,
J  >  21.3 mag,
H  >  20.7 mag and
K  >  20.0 mag.

These upper limits are derived based on calibrating the images against the
GROND zeropoints as well as 2MASS field stars.