GCN Circular 4917
F. Marshall (GSFC/NASA) and L. Vetere (ASDC) on behalf of the Swift/UVOT team The Swift/UVOT began taking data on the field of GRB 060323 at 14:37:30 UT on 2006-03-23, approximately 294s after the BAT trigger (Vetere et al., GCN 4904). There are marginal detections at the position of the optical afterglow (Covino et al. GCN 4911; Jensen et al. GCN 4915; Covino et al. GCN 4916) in the White, V, and B filters. The table below provides the results for the initial finding chart exposure using the White filter and for summed exposures. The UVOT on-board detection of a weak source suggested as a possible afterglow by Vetere et al. is not confirmed in ground analysis of the complete finding chart image. Filter T_range(s) Exp(s) 3-sigma UL Possible Detection Mag sigma White 294-393 100 20.0 21.1 1.8 White 486-17446 2171 21.9 V 525-22318 2012 20.6 21.6 2.1 B 473-16535 1308 21.3 22.1 2.6 U 449-6313 453 21.2 UVW1 425-23955 1163 21.3 These magnitudes are uncorrected for the expected Galactic extinction corresponding to E(B-V) = 0.015.