TITLE: GCN CIRCULAR NUMBER: 7769 SUBJECT: Swift/UVOT observations of GRB 080523 DATE: 08/05/24 12:02:56 GMT FROM: Paul Kuin at MSSL N. P. M. Kuin (MSSL/UCL), and M. C. Stroh (PSU), report on behalf of the Swift UVOT team The Swift UltraViolet/Optical Telescope (UVOT) began observations of GRB 080523, on May 23, 2008, at UT, 112 seconds after the initial Swift BAT trigger (Stroh et al., GCN Circ. 7767). We detect no source at the enhanced Swift XRT position (Osborne, GCN Circ.7768). The 3-sigma limiting magnitudes for GRB080523 are given below for the two initial observations, and for summed observations in each of the UVOT filters: Filter Tstart(s) Tstop(s) Exp(s) Magnitude white 112 211 99.8 > 20.78 v 218 617 399.8 > 19.93 white 112 12001 1211.2 > 21.80 v 218 6037 819.2 > 19.86 uvm2 624 6242 439.2 > 20.15 uvw1 649 6448 439.2 > 20.20 u 673 6649 435.9 > 19.92 b 698 11088 1118.9 > 21.56 uvw2 728 12430 841.6 > 20.77 The values quoted above are on the UVOT Photometric System (Poole et al, 2008, MNRAS 383,627). They are not corrected for the expected galactic reddening of E(B-V) = 0.025 in the direction of the burst (Schlegel et al. 1998).