TITLE: GCN CIRCULAR NUMBER: 8606 SUBJECT: Swift/UVOT detection of GRB081203B DATE: 08/12/04 00:37:27 GMT FROM: Patricia Schady at MSSL/Swift P. Schady (MSSL-UCL), F.E. Marshall (NASA/GSFC) and B. Sbarufatti (INAF-IASF Pa) report on behalf of the Swift/UVOT team: The Swift/UVOT began white band observations of the field of the Swift BAT Slew Survey (BATSS) GRB 081203B 4.6 hrs after the BAT trigger (Copete et al., GCN Circ. 8600, 8602). An uncatalogued, fading source is clearly detected at RA(J2000.0) = 15:15:11.67 (228.79863 deg) DEC(J2000.0) = +44:25:42.9 (44.42859 deg) with an estimated uncertainty of 0.5 arcsec (radius, 90% confidence), consistent with the UVOT-enhanced XRT position (Sbarufatti et al., GCN Circ. 8605). The magnitudes of the first and last UVOT white band observations are reported below: Filter T_mid (s) Exp (s) Magnitude white 16746 154 18.29 +/- 0.04 white 22270 441 18.70 +/- 0.03 indicating a decay rate of alpha~1.0. The above magnitudes are not corrected for the Galactic extinction corresponding to a reddening of E_{B-V} = 0.02 mag (Schlegel et al., 1998, ApJS, 500, 525). The photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383,627).