TITLE: GCN CIRCULAR NUMBER: 7530 SUBJECT: Swift/UVOT observations of GRB080328 DATE: 08/03/28 17:49:09 GMT FROM: Paul Ward at MSSL P. Ward (MSSL-UCL), P. Schady (MSSL-UCL) and M. Perri (ASDC) report on behalf of the Swift-UVOT team The Swift/UVOT observed the field of GRB 080328 starting 110s after the BAT trigger (Perri et al., GCN 7525). The afterglow is detected at RA: 05h 21m 55.87s DEC: +47d 30' 39.4" only in the white and v filters, with an error radius of 0.6 arcsec (90% confidence). The afterglow is seen to decay in both these filters, and has the following magnitudes and 3-sigma upper limits (in the UVOT photometric system, Poole et al. (2008, MNRAS, 383, 627)). Filter Tstart(s) Exp(s) Magnitude white 110 99.8 17.84 +/- 0.05 white 867 99.8 20.43 +/- 0.27 white 5611 399.8 > 21.60 v 217 399.8 17.90 +/- 0.08 v 973 399.8 19.25 +/- 0.20 v 6023 399.8 > 20.00 The afterglow is not detected in any other filters, perhaps due to the high Galactic extinction value of E(B-V) = 0.58 mag. The following are the 3-sigma upper limits for these filters. Filter Tstart(s) Exp(s) Magnitude b 851 493.6 > 20.96 u 673 338.5 > 20.59 uvw1 648 362.8 > 20.54 uvm2 623 393.2 > 20.38 uvw2 728 498.5 > 20.88 The values quoted above are not corrected for Galactic extinction corresponding to a reddening of E(B-V) = 0.58 mag in the direction of the burst (Schlegel et al. 1998).