TITLE: GCN CIRCULAR NUMBER: 21118 SUBJECT: GRB170519A, Swift-UVOT Detection DATE: 17/05/19 23:24:09 GMT FROM: Sam LaPorte at PSU GRB 170519A: Swift/UVOT Detection S. J. LaPorte (PSU) and T. N. Ukwatta (LANL) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 170519A 93 s after the BAT trigger (Ukwatta et al., GCN Circ. 21106). A fading source consistent with the XRT position (Beardmore et al. GCN Circ. 21107) is detected in all initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 10:53:42.45 = 163.42688 (deg.) Dec (J2000) = +25:22:27.5 = 25.37431 (deg.) with an estimated uncertainty of 0.42 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 5315 5515 196 17.22+-0.03 white 582 773 38 16.25+-0.04 white 89 239 147 16.91+-0.03 v 68 5926 421 17.46+-0.08 b 557 6594 282 17.66+-0.05 u 302 552 245 16.00+-0.04 uvw1 680 6337 412 16.76+-0.05 uvm2 5932 6131 196 17.13+-0.11 uvw2 607 627 19 16.45+-0.20 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