GCN Circular 11091
R. Filgas, P. Schady and J. Greiner (MPE Garching) report on behalf of the GROND team: We observed the field of GRB 100814A (Swift trigger 431605; Beardmore et al., GCN #11087) 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 03:57 UT, 7 minutes after the GRB trigger at 03:50 UT, and are continuing. They were performed at an average seeing of 1.2" and at an average airmass of 2. We detect a single point source in all GROND optical (g'r'i'z') and NIR bands (JHK) at a position consistent with the coordinates provided by Schaefer et al. (GCN #11086) and Gronwall et al. (GCN #11088), and consistent with the spectroscopic redshift of z=1.44 (O'Meara et al. GCN #11089). The afterglow decays as a power law with a best-fit index of alpha ~ 0.5, decaying from r' = 18.0 +/- 0.1 at T+25 minutes down to r' = 19.5 +/- 0.1 (all in AB system) by the end of our observations, at T+6 hours. Analysis is on going. Given magnitudes are calibrated against USNO zeropoints and are not corrected for the expected Galactic foreground extinction corresponding to a reddening of E(B-V)=0.02 in the direction of the burst (Schlegel et al. 1998).