GCN Circular 11781
D. Fugazza, P. D'Avanzo, S. Covino, S.D. Vergani, A. Melandri (INAF-OAB) on behalf of a larger collaboration report: The robotic 60-cm REM telescope located at La Silla (Chile) observed automatically the field of GRB 110305A (Grupe et al. GCN 11773) with the ROSS optical and REMIR near-infrared cameras in imaging mode. Observations started 93s from the GRB time (51s from the trigger time). No counterpart is visible in the optical frames, down to R > 16 (3sigma c.l., calibrated against the USNO B1.0 catalogue) while an object is visible with low significance in the first coadded NIR frames at a position consistent with the one of the optical afterglow (Nicuesa Guelbenzu et al. GCN 11774). Preliminary photometry shows that the source has H = 15.0 +/- 0.3 (calibrated against the 2MASS catalogue) at t-t0 = 4.5 min and is not detected anymore at t-t0 = 26.3 min down to a limiting magnitude H > 16.5 (3sigma c.l.). This implies an early power-law decay with index steeper than 0.8, consistent with the reported X-ray decay (Grupe, GCN 11778).