{
  "bibcode": "2017GCN.20919....1B",
  "body": "A. A. Breeveld (UCL-MSSL) and A. Cholden-Brown (PSU)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 170318B\n84 s after the BAT trigger (Cholden-Brown et al., GCN Circ. 20908).\nNo optical afterglow consistent with the XRT position (Goad et al. GCN \nCirc. 20910) is 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            84          234          147         >20.4\nu_FC               296          546          246         >19.8\nwhite               84         6145          530         >21.0\nv                  626         6557          432         >19.4\nb                  552         5940          236         >20.0\nu                  296         7172          659         >20.2\nw1                 675         6967          432         >19.9\nm2                5123         5323          197         >19.3\nw2                 601         6352          216         >19.6\n\nThe magnitudes in the table are not corrected for the Galactic \nextinction due to the reddening of E(B-V) = 4.51 in the direction of the \nburst (Schlegel et al. 1998).",
  "circularId": 20919,
  "createdOn": 1489913796000,
  "email": "a.breeveld@ucl.ac.uk",
  "subject": "GRB 170318B: Swift/UVOT Upper Limits",
  "submitter": "Alice Breeveld at MSSL-UCL  <a.breeveld@ucl.ac.uk>",
  "eventId": "GRB 170318B"
}