TITLE: GCN CIRCULAR NUMBER: 7495 SUBJECT: GRB 080319A: UVOT Observations DATE: 08/03/21 11:33:57 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and C. Pagani (PSU) report on behalf of the Swift/UVOT team: The Swift/UVOT observed the field of GRB 080319A starting 542 s after the BAT trigger (Pagani et al., GCN Circ. 7426). We detect the optical afterglow in the white filter at the location of the P60 source (Cenko, 2008, GCN Circ. 7429). Magnitudes and upper limits are reported below. Filter T_start (s) T_stop Exposure Mag Err Comment v 669 1544 432 >20.7 3-sigma UL b 767 1480 29 >19.8 3-sigma UL u 743 1618 58 >19.9 3-sigma UL white 562 662 98 21.1 0.3 875 975 98 >21.4 3-sigma UL 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). No early-time upper limits are available for the uvw1, uvm2, and uvw2 filters due to the lack of data resulting from the slew to GRB 080319B, which occurred 25 minutes after GRB 080319A.