TITLE: GCN CIRCULAR NUMBER: 27769 SUBJECT: GRB 200519A: Swift/UVOT Detection DATE: 20/05/20 19:09:27 GMT FROM: Mike Siegel at PSU/Swift MOC M. H. Siegel (PSU) and B. Sbarufatti (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 200519A 58 s after the BAT trigger (Sbarufatti et al., GCN Circ. 27756). A source consistent with the XRT position (Sbarufatti et al. GCN Circ. 27756) is detected in the initial UVOT exposures. The preliminary UVOT position is: RA (J2000) = 17:01:20.01 = 255.33337 (deg.) Dec (J2000) = -30:22:41.1 = -30.37808 (deg.) with an estimated uncertainty of 0.42 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 58 208 147 15.43 +/- 0.02 v 599 619 20 16.30 +/- 0.16 b 525 545 19 17.13 +/- 0.13 u 270 519 246 16.27 +/- 0.04 w1 648 840 39 17.46 +/- 0.25 w2 747 766 19 >17.5 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.47 in the direction of the burst (Schlegel et al. 1998).