TITLE: GCN CIRCULAR NUMBER: 19322 SUBJECT: GRB 160417A: Swift/UVOT Detection DATE: 16/04/17 18:40:24 GMT FROM: Alice Breeveld at MSSL-UCL A. A. Breeveld (UCL-MSSL) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160417A 136 s after the BAT trigger (D'Avanzo et al., GCN Circ. 19316). The source reported for the UVOT in the initial GCN and also by Zheng and Filippenko (GCN Circ. 19317) is found to be fading. The preliminary UVOT position is: RA (J2000) = 08:01:01.64 = 120.25685 (deg.) Dec (J2000) = +07:39:46.4 = 7.66289 (deg.) with an estimated uncertainty of 0.46 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 136 285 147 18.92 ± 0.07 white 870 1020 147 19.14 0.10 v 623 1070 58 18.54 ± 0.31 b 549 1169 58 19.07 ± 0.21 u 294 543 246 18.08 ± 0.08 w1 672 1280 64 >18.9 m2 647 1268 78 >19.1 w2 599 1220 78 >18.8 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.02 in the direction of the burst (Schlegel et al. 1998).