TITLE: GCN CIRCULAR NUMBER: 8478 SUBJECT: GRB081104: Swift/UVOT Upper Limits DATE: 08/11/04 20:35:43 GMT FROM: Peter Brown at PSU P. J. Brown, C. A. Swenson (PSU), S. T. Holland, and A. M. Parsons (GSFC), on behalf of the Swift/UVOT team. The Swift Ultra-Violet/Optical Telescope (UVOT) began settled observations of GRB 081104 (trigger 333666) 2638 seconds after the BAT trigger (Parsons et al., GCN Circ. 8473). No afterglow is detected at the XRT position (Mangano et al., GCN Circ. 8474) in any filter. The limiting magnitudes (3-sigma in 5" radius apertures) in each of the UVOT filters are as follows: Filter T_start(s) T_stop(s) Exp(s) Mag UL (3sig) white 2638 3882 209 >21.1 v 2794 9582 1082 >20.5 b 3614 3814 197 >20.4 u 3409 3609 197 >20.1 uvw1 3204 3404 197 >19.8 uvm2 2999 9874 479 >20.1 uvw2 2788 5368 197 >19.9 The values quoted above are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627). They are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V)=0.11 mag in the direction of the burst (Schlegel et al. 1998).