TITLE: GCN CIRCULAR NUMBER: 7360 SUBJECT: GRB 080303: Swift/UVOT follow-up of afterglow detection DATE: 08/03/03 23:18:28 GMT FROM: Alice Breeveld at MSSL-UCL A.A. Breeevld (MSSL/UCL) and T. Sakamoto (GSFC/UMBC) report on behalf of the Swift UVOT team: The Swift/UVOT observed the burst GRB080303 (Sakamoto et al. GCN circ 7351) starting with the finding chart exposure in white, 81s after the BAT trigger. The afterglow is detected at the enhanced XRT position (Evans et al. GCN circ 7356) in all filters except uvm2. In white it is detectable until at least 6600s after the trigger. The brightness increases until about 700s after the burst, then fades with an estimated temporal slope in the v filter of alpha= 0.9 The initial UVOT magnitudes (in the UVOT photometric system; Breeveld et al. GCN circ 6614) and 3 sigma upper limts from single exposures are as follows: Filter Tstart(s) Tstop(s) Exp(s) Mag error(mags) white 81 180 99.8 18.48 0.08 682 691 9.8 18.19 0.19 836 845 9.8 18.46 0.24 880 979 99.8 18.88 0.11 5195 5394 199.8 20.79 0.38 6632 6831 199.8 20.72 0.35 v 187 586 399.8 18.03 0.08 722 741 19.8 17.74 0.3 987 1095 108.1 19.06 0.3 5607 5806 199.8 19.76 0.38 b 667 676 9.8 18.59 0.36 821 830 9.7 >18.74 (UL) 4991 5190 199.8 >20.86 (UL) 6427 6626 199.8 20.26 0.27 u 642 661 19.8 18.23 0.32 797 816 19.8 17.99 0.26 4785 4984 199.8 19.4 0.22 6221 6420 199.8 20.33 0.41 uvw1 618 637 19.8 >18.1 (UL) 771 790 19.7 17.83 0.38 4581 4780 199.8 19.84 0.43 6016 6215 199.8 >20.18 (UL) uvm2 593 612 19.8 >17.58 (UL) 746 765 19.8 >17.61 (UL) 4375 4574 199.8 > 19.69 (UL) 5811 6010 199.8 >19.76 (UL) uvw2 698 717 19.8 >18.01 (UL) 851 870 19.8 17.82 0.37 5401 5600 199.7 19.76 0.33 6838 6875 37.6 >18.7 (UL) The values quoted above are not corrected for the expected Galactic extinction corresponding to a reddening of E(B-V)=0.192 mag in the direction of the burst (Schlegel et al. 1998).