{
  "bibcode": "2021GCN.31317....1S",
  "body": "M. H. Siegel (PSU) 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 211221A\n63 s after the BAT trigger (Page et al., GCN Circ. 31273).\nNo optical afterglow consistent with the XRT position (Evans et al.\nGCN Circ. 31275) 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            63          213          147         >20.7\nu_FC               275          525          246         >20.1\nwhite               63         1010          317         >21.1\nv                  606          799           39         >18.6\nb                  531          724           39         >19.4\nu                  275          872          285         >20.0\nw1                 655          848           39         >18.1\nm2                 631          650           19         >17.8\nw2                 582          774           39         >19.0\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.143 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 31317,
  "createdOn": 1640650448000,
  "email": "mhs18@psu.edu",
  "subject": "GRB 211221A: Swift/UVOT Upper Limits",
  "submitter": "Mike Siegel at PSU/Swift MOC  <mhs18@psu.edu>",
  "eventId": "GRB 211221A"
}