TITLE: GCN CIRCULAR NUMBER: 32063 SUBJECT: GRB 220518A: Swift/UVOT Detection DATE: 22/05/18 15:09:29 GMT FROM: Samantha Oates at MSSL S. R. Oates (U.Birmingham) and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 220518A 129 s after the BAT trigger (Gropp et al., GCN Circ. 32060). A source consistent with the enhanced XRT position (Beardmore et al. GCN Circ. 32062) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 03:41:22.29 = 55.34289 (deg.) Dec (J2000) = -47:35:00.3 = -47.58342 (deg.) with an estimated uncertainty of 0.55 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 (FC) 129 279 147 20.00 +/- 0.25 white 621 1717 334 20.49 +/- 0.23 v 671 1767 136 >19.0 b 597 1861 131 >20.1 u (FC) 341 591 246 >19.7 u 341 1841 324 >19.9 w1 1103 1296 39 >18.4 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.008 in the direction of the burst (Schlegel et al. 1998).