{
  "bibcode": "2018GCN.22992....1O",
  "body": "S. R. Oates (U. Warwick) and S. J. LaPorte (PSU) report on behalf\nof the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 180720C\n100 s after the BAT trigger (LaPorte et al., GCN Circ. 22982).\nNo optical afterglow consistent with the XRT position (Evans et al., GCN\nCirc. 22987) 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\nwhite (FC)         100         250          147           >20.3\nwhite              100         5490         541           >21.0    \nu (FC)             312         425          111           >19.2\nu                  312         11199       1193           >20.6\nv                  4263        5901         393           >19.1\nb                  3646        11902       1072           >20.8\nuvw1               4674        10285       1133           >20.3\nuvm2               4469        6106         393           >19.7\nuvw2               4058        5696         393           >19.8\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the significant reddening of E(B-V) = 2.11 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 22992,
  "createdOn": 1532162126000,
  "email": "sro@mssl.ucl.ac.uk",
  "subject": "GRB 180720C: Swift/UVOT Upper Limits",
  "submitter": "Samantha Oates at MSSL  <sro@mssl.ucl.ac.uk>",
  "eventId": "GRB 180720C"
}