TITLE: GCN CIRCULAR NUMBER: 7941 SUBJECT: GRB 080703: UVOT Follow-Up Observation DATE: 08/07/04 11:15:48 GMT FROM: Paul Ward at MSSL P. Ward (MSSL-UCL) and H. Ziaeepour (UCL-MSSL) report on behalf of the Swift/UVOT team: The Swift Ultra-Violet/Optical Telescope (UVOT) started observing GRB 080703 (Rykoff et al. GCN 7935, Ziaeepour et. al, GCN 7936) ~100 seconds after the trigger. A quickly fading candidate afterglow is found in the UVOT White and V filters. The preliminary Swift/UVOT position of the optical afterglow candidate is: RA(J2000) = 06:47:12.639 = 101.8027 DEC(J2000) = -63:13:08.96 = -63.2192 with a 1-sigma error radius of about 0.5 arcsec. The following table gives the measured magnitudes: Filter T_start T_stop Exp Mag White 101 200 99.8 17.40 +/- 0.03 White 857 956 99.8 20.27 +/- 0.35 White 5905 6102 196.6 21.29 +/- 0.49 White 5905 19222 869.5 > 21.77 (1.9-sigma) V 207 606 399.8 18.02 +/- 0.10 V 963 1362 399.8 19.06 +/- 0.27 V 6315 6512 196.6 > 19.65 (0.2-sigma) V 6315 12021 1081.7 > 20.83 (0.9-sigma) B 687 1788 78.9 > 19.48 (1.8-sigma) B 663 1764 99.0 > 19.33 (1.5-sigma) UVW1 638 1885 99.9 > 19.55 (0.1-sigma) UVM2 613 1878 118.7 > 19.67 (1.7-sigma) UVW2 718 1829 79.1 > 19.55 (0.9-sigma) The values quoted above are in the UVOT photometric system (Poole et al. 2008, MNRAS, 383, 627). No correction has been made for the expected extinction corresponding to E(B-V) of 0.071 mag in the direction of the burst (Schlegel et al. 1998).