TITLE: GCN CIRCULAR NUMBER: 14384 SUBJECT: GRB 130418A: Swift/UVOT Detection and request for continuing coverage DATE: 13/04/19 01:19:37 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin and M. De_Pasquale (UCL-MSSL) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 130418A 138 s after the BAT trigger (De_Pasquale et al., GCN Circ. 14377). A source consistent with the XRT position (De Pasquale et al. GCN Circ. 14377) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 09:56:08.88 = 149.03700 (deg.) Dec (J2000) = +13:40:02.7 = 13.66741 (deg.) with an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence). Preliminary detections 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 138 288 146 14.85 +/- 0.05 u 296 353 56 14.71 +/- 0.04 v 5634 5834 197 17.69 +/- 0.08 b 3567 3766 197 17.41 +/- 0.05 w1 6044 6124 78 17.25 +/- 0.11 m2 5839 6039 197 17.61 +/- 0.11 w2 5430 5630 197 18.08 +/- 0.11 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.03 in the direction of the burst (Schlegel et al. 1998). Due to a Moon constraint, Swift observations will stop for now. Continuing acquisition of ground-based data, including ubv photometry will be useful at this time.