TITLE: GCN CIRCULAR NUMBER: 11019 SUBJECT: GRB 100727A: Swift/UVOT Upper Limits DATE: 10/07/28 16:14:12 GMT FROM: Stephen Holland at USRA/NASA/GSFC/SSC S. T. Holland (CRESST/GSFC/USRA) and D. C. Morris (GWU/GSFC) report on the behalf of the Swift UVOT team: The Swift/UVOT observed the field of GRB 100727A starting 47 s after the BAT trigger (Morris, et al., 2010, GCN Circ. 10998). Settled observations started at 65 s. We do not find any new source, relative to the DSS, USNO-B1.0, or 2MASS at the position of the XRT afterglow (Osborne, et al. 2010, GCN Circ. 11000). Preliminary 3-sigma upper limits for detecting a source in the finding charts, and in the co-added images, using a 2.5 arcsecond radius circular aperture, are Filter T_start T_stop Exp(s) Mag ------------------------------------------------ white (fc) 65 215 147 >20.8 856 1006 147 >21.2 u (fc) 278 527 246 >20.5 v 609 18,409 1414 >20.9 b 533 24,918 1215 >21.7 u 278 24,189 2335 >21.7 uvw1 658 29,885 2289 >21.9 uvm2 633 28,542 2390 >21.8 uvw2 584 17,496 1415 >21.8 white 65 7075 805 >22.1 ------------------------------------------------ The quoted upper limits have not been corrected for the expected Galactic extinction along the line of sight corresponding to a reddening of E_{B-V} = 0.05 mag (Schlegel, et al., 1998, ApJS, 500, 525). All photometry is on the UVOT photometry system described in Poole et al. (2008, MNRAS, 383, 627).