{
  "bibcode": "2014GCN.15920....1M",
  "body": "F. E. Marshall (NASA/GSFC) and P. A. Evans (U. Leicester)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 140304A\n138 s after the BAT trigger (Evans et al., GCN Circ. 15915).\nNo optical afterglow consistent with the optical position\n(Gorbovskoy et al. GCN Circ. 15914)\nis detected in the initial UVOT exposures.\nPreliminary 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first\nfinding chart (FC) exposure and subsequent exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)         Mag\n\nu_FC               138          388          246         >20.4\nv                  420         1561          165         >19.5\nu                  138         1519          529         >20.9\nw1                 469         1495          156         >19.7\nm2                 570         1470          117         >20.1\nw2                 396         1546          156         >20.0\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.08 in the direction of the burst\n(Schlegel et al. 1998).\n\nIn view of the bright (16.5 mag) afterglow reported by\nGorbovskoy et al., it is likely that the GRB has large\nintrinsic extinction or is at a redshift greater than\nabout 3.5.",
  "circularId": 15920,
  "createdOn": 1393969195000,
  "email": "femarsha@khamseen.gsfc.nasa.gov",
  "subject": "GRB 140304A: Swift/UVOT Upper Limits",
  "submitter": "Frank Marshall at GSFC  <femarsha@khamseen.gsfc.nasa.gov>",
  "eventId": "GRB 140304A"
}