{
  "bibcode": "2018GCN.22379....1K",
  "body": "N. P. M. Kuin (UCL-MSSL) and K. L. Page (U. Leicester)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 180204A\n92 s after the BAT trigger (Page et al., GCN Circ. 22375). A star is\npresent in the GSC whos position is consistent with the enhanced XRT\nposition (Osborne et al. GCN Circ. 22377).   No optical afterglow above\nthe stellar flux has been 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\nwhite_FC            92          242          147         >20.3\nu_FC               304          554          246         >19.9\nwhite               92        17884         1210         >20.8\nv                  633        10587         1107         >19.0\nb                  560        23622         1840         >20.7\nu                  304        23062         2409         >21.1\nw1                3943        22148         1917         >21.0\nm2                 658        11492         1095         >20.8\nw2                 609         6398          413         >20.1\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.10 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 22379,
  "createdOn": 1517763012000,
  "email": "npkuin@gmail.com",
  "subject": "GRB 180204A: Swift/UVOT Upper Limits",
  "submitter": "Paul Kuin at MSSL  <npkuin@gmail.com>",
  "eventId": "GRB 180204A"
}