TITLE: GCN CIRCULAR NUMBER: 8262 SUBJECT: GRB 080916C: Swift UVOT Refined Analysis DATE: 08/09/17 17:59:31 GMT FROM: Erik Hoversten at Swift/Penn State E. A. Hoversten (PSU), P. Schady (MSSL-UCL), and M. Perri (ASDC) report on behalf of the Swift UVOT team: The Swift/UVOT began observations of the field of GRB 080916C 17.0 hours after the Fermi GBM dectection (Goldstein & van der Horst, GCN 8245). No afterglow is detected within the XRT error circle (Evans, et al., GCN 8255) in any of the observed UVOT filters. UVOT magnitude 3-sigma upper limits are reported in the following table: Filter T_start T_stop Exp(s) Mag (3-sigma upper limit) ------------------------------------------------------------- v 101253 101857 590 > 19.75 u 96469 97132 645 > 19.99 uvw1 66675 67517 829 > 20.34 uvw1 95562 96462 886 > 20.38 uvm2 61130 66667 1090 > 20.31 uvm2 94655 95555 886 > 20.20 uvw2 100347 101246 886 > 20.43 The quoted upper limits have not been corrected for the large expected Galactic extinction along the line of sight of E_{B-V} = 0.32 mag (Schlegel et al., 1998). All photometry is on the UVOT flight system described in Poole et al. (2008, MNRAS, 383, 627).