TITLE: GCN CIRCULAR NUMBER: 7458 SUBJECT: GRB 080319D: Swift/UVOT Refined Analysis of the Fading Optical Afterglow Candidate DATE: 08/03/19 19:54:49 GMT FROM: Stefan Immler at NASA/GSFC S. Immler (CRESST/GSFC/UMD) and P. J. Brown (PSU) report on behalf of the Swift UVOT team: The Swift/UVOT observations of the field of GRB 080319D (trigger 306793) starting 151 seconds after the BAT trigger (Brown, et al., GCN Circ. 7453) reveal a fading optical afterglow candidate. The white and v-filter magnitudes are as follows: Filter T_start (s) T_stop (s) Exp (s) Mag (3-sigma UL) ---------------------------------------------------------------------------------------------- White 151 251 100 19.7+/-0.3 White 866 966 100 20.2+/-0.4 v 257 657 400 >19.5 v 972 1362 400 >19.5 ---------------------------------------------------------------------------------------------- No correction has been made for the expected Galactic extinction corresponding to E(B-V) of 0.19 (Schlegel, et al. 1998). The position of the optical afterglow candidate is RA (2000) = 06h 37m 53.6s Dec (2000) = +23d 56' 34.2" with an uncertainty of 0.5 arcsec, which is 2.2 arcsec offset from the XRT position (Brown, et al., GCN Circ. 7453).