TITLE: GCN CIRCULAR NUMBER: 19037 SUBJECT: GRB160220B: Swift/UVOT observations DATE: 16/02/20 21:42:50 GMT FROM: Massimiliano de Pasquale at IASF-Palermo M. De Pasquale (MSSL-UCL) and J. Cummings (GSFC/UMBC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160220B 3.33 ks after the BAT trigger (Cummings et al., GCN Circ. 19029). No optical afterglow consistent with the XRT position (Evans et al. GCN Circ. 19033) is detected in the UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the summed UVOT exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 3735 5370 393 >21.0 v 4145 10454 1082 >20.1 b 3530 5165 393 >20.4 u 4882 16950 451 >20.1 w1 4555 16884 1504 >20.9 m2 4350 11207 933 >20.7 w2 5499 32840 1170 >20.9 We note the presence of an uncatalogued source of magnitude 20.2 +/- 0.20 in white filter, at coordinates RA = 17h 19m 28.07, Dec = -18d 07m 25.5s (J2000), which is 5" from the enhanced XRT position. The magnitudes above are not corrected for the substantial Galactic extinction due to the reddening of E(B-V) = 0.32 in the direction of the burst (Schlegel et al. 1998). -- Dr. Massimiliano De Pasquale Research associate - Swift UVOT scientist Mullard Space Science Laboratory, University College London