{
  "bibcode": "2018GCN.23167....1M",
  "body": "F. E. Marshall (NASA/GSFC) and A. Tohuvavohu (PSU)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 180821A\n219 s after the BAT trigger (Tohuvavohu et al., GCN Circ. 23158).\nNo optical afterglow consistent with the enhanced XRT position\n(Evans et al. GCN Circ. 23162) 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           219          369          147         >21.0\nwhite              219          495          167         >21.1\nv                  526          546           19         >17.7\nv                 4604         6039          393         >20.0\nb                  451          471           19         >19.3\nb                 3988         5624          393         >21.3\nu                  426          446           19         >18.6\nu                 3783         5418          393         >20.5\nw1                 402          421           19         >19.3\nw1                5015        15906          241         >20.5\nm2                4808        10398          812         >20.5\nw2                4399         6034          393         >20.3\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.02 in the direction of the burst\n(Schlegel et al. 1998).",
  "circularId": 23167,
  "createdOn": 1534955073000,
  "email": "marshall@milkyway.gsfc.nasa.gov",
  "subject": "GRB 180821A: Swift/UVOT Upper Limits",
  "submitter": "Frank Marshall at Swift/UVOT  <marshall@milkyway.gsfc.nasa.gov>",
  "eventId": "GRB 180821A"
}