TITLE: GCN CIRCULAR NUMBER: 19134 SUBJECT: GRB 160303A: Swift/UVOT Detection DATE: 16/03/03 20:15:46 GMT FROM: Sam Emery at MSSL-UCL S.W.K. Emery (UCL-MSSL) and A. P. Beardmore (U Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 160303A 109 s after the BAT trigger (Beardmore et al., GCN Circ. 19126). We detect a fading source consistent with the XRT position (Beardmore et al. GCN Circ. 19126) and the RATIR optical and NIR afterglow detections (Butler et al. GCN Circ 19131) in the initial UVOT u filter exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 109 259 147 >21.9 u_FC 321 571 246 20.75 white 109 2061 450 >22.5 b 576 2037 136 >19.9 w1 700 2161 77 >20.5 m2 1426 1445 19 >19.5 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).