TITLE: GCN CIRCULAR NUMBER: 16303 SUBJECT: GRB 140518A: Swift/UVOT Upper Limits DATE: 14/05/18 17:18:01 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (UCL-MSSL) and A. Melandri (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 140518A 77 s after the BAT trigger (Melandri et al., GCN Circ. 16298). No optical afterglow consistent with the XRT position (Melandri et al. GCN Circ. 16298) is detected in the initial UVOT 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 77 226 147 >20.7 u_FC 289 539 246 >20.7 white 77 13719 1583 >22.6 v 619 7499 568 >20.2 b 545 12953 1060 >22.0 u 289 12041 1286 >21.6 w1 668 7910 568 >21.4 m2 1071 7705 413 >21.1 w2 595 7295 510 >21.3 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).