TITLE: GCN GRB OBSERVATION REPORT NUMBER: 4004 SUBJECT: GRB050916: Swift/UVOT Upper Limits DATE: 05/09/19 19:28:00 GMT FROM: Peter Brown at PSU GRB050916: Swift/UVOT Upper Limits P. J. Brown (PSU), D. Morris (PSU), H. Huckle (UCL-MSSL), B. Hancock (UCL-MSSL), and N. Gehrels (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began observing the field of GRB 050916 (Swift Trigger #155408) on 2005/09/16 at 16:39:20 UT, 207 seconds after the BAT trigger (Morris et al. GCN 3991). No source is detected within the XRT error circle (Morris et al. GCN 3996) in the initial 100 second V-band image down to a 5-sigma upper limit of 17.9, or in summed exposures in any of the UVOT filters down to the following 5-sigma upper limits: Filter T_range (s) Exp (s) 5sigma UL V 207 - 74,597 4455 19.9 B 353 - 65,371 4374 20.7 U 339 - 63,016 4207 20.4 UVW1 325 - 58,536 4152 20.1 UVM2 311 - 53,803 4223 20.0 UVW2 368 - 69,038 3706 20.2 The magnitudes are uncorrected for extinction, which is extremely high as this direction lies in the galactic plane.