TITLE: GCN CIRCULAR NUMBER: 7905 SUBJECT: GRB 080625: Swift/UVOT Detection of an Optical Afterglow DATE: 08/06/26 02:09:08 GMT FROM: Stefan Immler at NASA/GSFC S. Immler (NASA/CRESST/GSFC) reports on behalf of the Swift/UVOT team: The Swift Ultra-Violet/Optical Telescope (UVOT) started observing GRB 080625 (Pacciani et al., GCN Circ. 7903) ~5.0 hours after the AGILE trigger. A candidate afterglow is found in UVOT White, v, and b filter images which cover the entire AGILE error circle. The preliminary Swift/UVOT position of the optical afterglow candidate is: RA(J2000) = 19:53:37.06 = 298.4044 DEC(J2000) = +56:16:40.5 = 56.2779 with a 1-sigma error radius of about 0.5 arcsec. The following table gives the measured magnitudes: Filter T_start [s] T_stop [s] Exp [s] Magnitude White 18769 19567 799 20.3 +/- 0.1 White 24551 25179 1427 20.6 +/- 0.1 V 19575 20350 776 19.6 +/- 0.1 B 17964 18762 799 20.1 +/- 0.1 B 23746 24544 799 20.7 +/- 0.2 U 17880 23741 240 >20.4 (3-sigma UL) 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 0.44 mag in the direction of the burst (Schlegel et al. 1998).