TITLE: GCN GRB OBSERVATION REPORT NUMBER: 3367 SUBJECT: GRB 050505 UVOT DATE: 05/05/06 08:22:11 GMT FROM: Simon Rosen at MSSL-UCL S. Rosen (MSSL), C. Hurkett (Leicester), W. Landsman (GSFC), P. Roming (PSU), T. Poole (MSSL), N. Gehrels (GSFC), K. Mason (MSSL), J. Nousek (PSU), on behalf of the Swift UVOT team The Swift Ultra-Violet/Optical Telescope (UVOT) began observations of GRB050505 on May 06, 2005 at 00:09:08 UT, ~48 minutes after the initial Swift BAT trigger (Hullinger et al, GCN 3364) (the delay in observations was due to the Earth-limb constraint, which prevented an immediate slew). Initial data is limited to one 100s exposure in each of four filters. We detect no source at the Swift XRT position (Kennea et al, GCN 3365) in any filter. The limiting magnitudes (5-sigma in 6" radius apertures) in each of the UVOT filters are as follows: Filter Lim_Mag Duration (s) T_start (s) V ~17.7 100 T + 2870 U ~18.4 100 T + 3180 UVW1 ~18.9 100 T + 3080 UVM2 ~19.7 100 T + 2970 The magnitudes are based on preliminary zero-points, measured in orbit, and will require refinement with further calibration. This message may be cited.