{
  "bibcode": "2011GCN.12157....1H",
  "body": "S. T. Holland (CRESST/USRA/GSFC) and\nJ. R. Cummings (CRESST/UMBC/GSFC)\nreport on behalf of the Swift/UVOT team:\n\n      The Swift/UVOT observed the field of GRB 110709B starting 70 s\nafter the BAT trigger (Cummings et al., 2011, GCNC 12122).  Settled\nobservations started at 91 s.  We do not detect a source at the\nUVOT-enhanced XRT position (Beardmore, et al., 2011, GCNC 12136) in\nany of the UVOT filters.  Preliminary 3-sigma upper limits for\ndetecting a source in the finding charts and in the co-added images,\nare\n\nFilter       TSTART       TSTOP  EXPOSURE       Mag\n---------------------------------------------------\nwhite (FC) &     91 &       241 &     147 &   >21.1\n    u (FC) &    303 &       553 &     246 &   >20.5\nwhite (FC) &    858 &      1008 &     147 &   >21.3\n---------------------------------------------------\n    v     &     633 &    64,817 &    3519 &   >21.5\n    b     &     558 &    54,124 &    3664 &   >22.4\n    u     &     303 &    59,906 &    4680 &   >22.2\n uvw1     &     682 &    59,264 &    4730 &   >22.2\n uvm2     &    1235 &    58,357 &    3732 &   >22.3\n uvw2     &     782 &    64,122 &    3530 &   >22.4\nwhite     &      91 &    30,997 &    3107 &   >23.0\n---------------------------------------------------\n\n     We find weak evidence for variability at the location of the\nUSNO-B1.0 source 3.5 arcsec WNW of the XRT position at the time of the\nsecond BAT trigger (Barthelmy et al. 2011, GCNC 12124).  Preliminary\nphotometry is\n\nFilter       TSTART       TSTOP  EXPOSURE       Mag   Err  Sigma\n----------------------------------------------------------------\nwhite &          91 &       241 &     147 &   >21.1   3-sigma UL\nwhite &         583 &       776 &      39 &    20.08 0.35    3.3\nwhite &         858 &      1008 &     147 &   >21.3   3-sigma UL\nwhite &        1161 &      2047 &     117 &    20.96 0.36    3.1\nwhite &        6245 &      6444 &     197 &   >21.4   3-sigma UL\nwhite &        7679 &    11,397 &     340 &    21.07 0.37    3.1\nwhite &       11401 &    12,005 &     590 &   >21.9   3-sigma UL\nwhite &       17893 &    18,800 &     885 &    20.98 0.16    7.8\nwhite &       30335 &    30,997 &     644 &    21.39 0.23    5.2\n----------------------------------------------------------------\n\nWe note that both the USNO-B1.0 source and the XRT position are\nlocated in the coincidence loss halo of a bright star, which makes\nprecision photometry difficult.  It is not clear if the apparent\nvariability seen at the location of the USNO-B1.0 source is real or\nnot.\n\n     The quoted magnitudes and upper limits have not been corrected\nfor the large, but uncertain, Galactic extinction along the line of\nsight to this burst (E_{B-V} = 0.05 mag, Schlegel et al. 1998, ApJS,\n500, 525).",
  "circularId": 12157,
  "createdOn": 1310731200000,
  "email": "Stephen.T.Holland@nasa.gov",
  "subject": "GRB 110709B: Swift/UVOT Observations",
  "submitter": "Stephen Holland at USRA/NASA/GSFC/SSC  <Stephen.T.Holland@nasa.gov>",
  "eventId": "GRB 110709B"
}