{
  "bibcode": "2017GCN.22262....1M",
  "body": "F. E. Marshall (NASA/GSFC) reports on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 171216A\n124 s after the BAT trigger (Marshall et al., GCN Circ. 22256).\nNo optical afterglow consistent with the XRT position\n(Goad et al., GCN Circ. 22257)\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\nwhite_FC           124          274          147         >21.3\nu_FC               282          532          246         >18.4\nv                  613        17562          371         >17.8\nb                  539         6997          359         >19.8\nu                  282         6886          678         >18.6\nw1                 662         6681          452         >19.3\nm2                 637         6476          274         >19.3\nw2                 588        12734          720         >20.1\n\nThese preliminary results may be affected by the presence of\na bright source about 10\" from the XRT position.\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.26 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 22262,
  "createdOn": 1513692729000,
  "email": "marshall@milkyway.gsfc.nasa.gov",
  "subject": "GRB 171216A: Swift/UVOT Upper Limits",
  "submitter": "Frank Marshall at Swift/UVOT  <marshall@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 171216A"
}