TITLE: GCN CIRCULAR NUMBER: 23323 SUBJECT: GRB 181010A: REM optical and NIR afterglow detection DATE: 18/10/11 11:06:56 GMT FROM: Paolo D'Avanzo at INAF-OAB P. D'Avanzo, S.Covino, D. Fugazza, A. Melandri (INAF-OAB), on behalf of the REM team, report: We observed the optical counterpart of GRB 181010A (Melandri et al. GCN 23309; Gorbovskoy et al. GCN 23310; Martone et al. GCN 23311; Troja et al. GCN 23312; Vielfaure et al. GCN 23315; Emery et al. GCN 23317; D'Avanzo et al. GCN 23319) with the REM 60cm robotic telescope located at the ESO premise of La Silla (Chile). The observations were performed starting on 2018 October 10 at 05:56:52 UT (i.e. 61 seconds after the burst) and were carried simultaneously in the g, r, i, z, and H bands. The GRB afterglow is detected in the first set of optical and NIR images. From preliminary photometry we estimate the following magnitudes: r = 18.2 +/- 0.2 (AB; calibrated against the Pan-STARRS catalogue) H = 14.4 +/- 0.2 (Vega; calibrated against the 2MASS catalogue) at a mean time of 4.1 minutes from the GRB time (Melandri et al. GCN 23309).