TITLE: GCN CIRCULAR NUMBER: 22881 SUBJECT: GRB 180630A: Swift/UVOT Detection DATE: 18/07/02 01:46:46 GMT FROM: Sam LaPorte at PSU GRB 180630A: Swift/UVOT Detection S. J. LaPorte (PSU) and P. D'Avanzo (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180630A 88 s after the BAT trigger (D'Avanzo et al., GCN Circ. 22872). A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 22873) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 03:15:55.74 = 48.98224 (deg.) Dec (J2000) = -87:28:42.3 = -87.47842 (deg.) with an estimated uncertainty of 0.43 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 88 237 148 17.49 +/- 0.04 white 6384 6584 196 19.50 +/- 0.11 v 629 1597 117 18.56 +/- 0.20 b 555 748 39 18.76 +/- 0.19 u 300 549 246 17.76 +/- 0.06 w1 678 7392 510 19.42 +/- 0.17 m2 654 7187 452 20.16 +/- 0.33 w2 605 6777 255 >19.9 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.13 in the direction of the burst (Schlegel et al. 1998).