GCN Circular 10314
R. Filgas, F. Olivares, J. Greiner, T. Kruehler (all MPE Garching) and S. Klose (Tautenburg Observatory) report on behalf of the GROND team: We observed the field of GRB 100103A (INTEGRAL trigger #5970; Gotz et al., GCN #10307) simultaneously in g'r'i'z'JHK with GROND (Greiner et al. 2008, PASP, 120, 405) mounted at the 2.2 m ESO/MPI telescope at La Silla Observatory (Chile). Observations started on January 4, 2010 at 00:48 UT, 7.1 hours after the GRB trigger. They were performed at variable seeing of 2-3" and at an average airmass of 1.4. No source is found within the 1.7" XRT error circle (Page et al., GCN #10312). Comparison to the Digital Sky Survey and 2MASS also reveals no new sources within a 10 arcsec surrounding. Co-added images of 24.6 min of integration time in g'r'i'z' and 20 min in JHK, centered at 01:29 UT yield the following specific upper limits (AB system): g' > 24.9 r' > 24.2 i' > 23.6 z' > 23.8 J > 21.2 H > 20.6 K > 19.2 calibrated against USNO and 2MASS field stars. No correction for the Galactic foreground extinction was made, which correspond to a reddening of E(B-V)=0.29 mag in the direction of the burst (Schlegel et al. 1998).