TITLE: GCN CIRCULAR NUMBER: 22831 SUBJECT: GRB 180623A: Swift/UVOT Detection DATE: 18/06/24 13:58:14 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180623A 86 s after the BAT trigger (Page et al., GCN Circ. 22828). A source consistent with the XRT position (Evans et al. GCN Circ. 22829) is detected in the initial UVOT exposures. The UVOT refined position is ra, deg = 214.5288,-60.2541 deg which is RA = 14:18:06.9 Dec = -60:15:14.8 with an estimated uncertainty of 1". 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 86 236 150 >20.68 white 878 997 119 20.04 +/- 0.24 v 629 6296 432 >19.2 b 18042 18207 162 19.86 +/- 0.28 u 299 17732 2252 >21.6 w1 678 16819 1318 >20.8 m2 653 6501 432 >20.0 w2 604 6092 432 >20.0 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 7.04 in the direction of the burst (Schlegel et al. 1998).