TITLE: GCN GRB OBSERVATION REPORT NUMBER: 5603 SUBJECT: GRB060923B: Swift/UVOT upper limits DATE: 06/09/24 18:05:41 GMT FROM: Antonino Cucchiara at PSU S. Holland and A. Cucchiara report on behalf of the Swift/UVOT team: The Swift UVOT began observing GRB 060923B (trigger #230702), M. Stamatikos et al., GCN Circ. 5590) 122 seconds after the BAT trigger. No optical afterglow is detected in the XRT refined error circle (M. Capalbi et al., GCN Circ.5602). The 3-sigma limiting magnitudes for the finding chart and the coadded images for the UVOT filters are listed below: Finding chart: Filter T_range (s) Exposure (s) 3sigma UL White 122-220 98 19.42 White 5163-5360 197 19.79 V 225-387 162 18.52 Coadded images: Filter T_range (s) Exposure (s) 3sigma UL V 5572-5768 196 18.61 B 4959-5156 197 19.61 U 4754-4950 197 19.28 W1 4550-6170 386 19.45 M2 4345-5974 394 19.70 W2 5368-5565 197 19.92 T_range is calculated from the time of the burst. No correction has been made for the Galactic reddening of E(B-V) = 0.15 mag (Schlegel et al. 1998) along the line of sight to the burst.