TITLE: GCN CIRCULAR NUMBER: 22549 SUBJECT: GRB 180325A: Swift/UVOT Detection DATE: 18/03/26 17:07:59 GMT FROM: Frank Marshall at Swift/UVOT F. E. Marshall (NASA/GSFC) and E. Troja (NASA/GSFC/UMCP) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 180325A 82 s after the BAT trigger (Troja et al., GCN Circ. 22532). A fading source consistent with the enhanced XRT position (Osborne et al. GCN Circ. 22539) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 10:29:42.59 = 157.42744 (deg.) Dec (J2000) = +24:27:48.6 = 24.46349 (deg.) with an estimated uncertainty of 0.44 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 82 232 147 18.48 +/- 0.05 white 5039 5239 197 20.75 +/- 0.23 v 5450 5650 197 >18.8 b 4834 6385 309 >20.1 u 295 6265 353 >20.0 w1 5860 6060 197 >20.1 m2 5654 5854 197 >19.4 w2 5245 12343 980 >20.9 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).