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).