GCN Circular 21172
M. H. Siegel (PSU) and P. A. Evans (U Leicester) report on behalf of the Swift/UVOT team: UVOT took a finding chart exposure of 150 seconds with the White filter starting 3522 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The coverage of the XRT error circle by the 8'x8' region for the list of sources generated on-board is uncertain because the large number of sources filled the available telemetry. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.09.