GCN Circular 10607

Robert Filgas, Thomas Kruehler and Jochen Greiner (all MPE Garching) 
report on behalf of the GROND team:

We observed the field of GRB 100414A (Fermi GBM/LAT trigger
292904423/100414.097; Takahashi et al., GCN #10594, Foley, GCN #10595) 
simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP 120, 
405) mounted at the 2.2 m MPI/ESO telescope at La Silla Observatory (Chile).

Observations started at 03:11 UT on April 17, 73 hours after the GRB
trigger, and were performed through thick cloud coverage.

We detect the optical afterglow reported by Cucchiara & Fox (GCN #10606) 
in the optical bands. To reiterate the position, we measure

RA (J2000.0) = 12 h 48 m 26.93 s
DEC (J2000.0) = +08d 41' 34.4"

with an uncertainty of 0.5" in each coordinate against SDSS astrometry 
and inside the enhanced XRT error circle reported by Page et al. (GCN 
#10605).

Based on 4 min of total exposure, we estimate preliminary magnitudes 
(all in AB system) of

g' = 21.3 +- 0.1 mag,
r' = 20.9 +- 0.1 mag

Given magnitudes are calibrated against SDSS field stars and are not
corrected for the expected Galactic foreground extinction corresponding 
to a reddening of E_(B-V)=0.03 mag in the direction of the burst 
(Schlegel et al. 1998).