TITLE: GCN CIRCULAR NUMBER: 33642 SUBJECT: GRB 230414B: Swift/UVOT Detection DATE: 23/04/18 17:05:38 GMT FROM: Sam LaPorte at PSU GRB 230414B: Swift/UVOT Detection S. J. LaPorte (PSU) and A. D'Ai (INAF-IASFPA) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 230414B 133 s after the BAT trigger (D'Ai et al., GCN Circ. 33612). A fading source consistent with the optical position (Pankov et al. GCN Circ. 33615) is detected in the initial UVOT exposures. 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 b 543 735 38 >19.23 m2 1070 1089 19 >17.31 u 287 710 265 >20.09 v 617 1065 58 >18.53 w1 666 859 38 >18.48 w2 766 785 19 >17.72 white_FC 129 1015 481 20.92+-0.22 white 5056 5203 145 >20.64 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.017 in the direction of the burst (Schlegel et al. 1998).