{
  "eventId": "GRB 250821A",
  "submitter": "Samantha Oates at University of Birmingham <samantha.oates@alumni.ucl.ac.uk>",
  "bibcode": "2025GCN.41471....1O",
  "createdOn": 1755798904030,
  "submittedHow": "email",
  "subject": "GRB 250821A: Swift/UVOT Upper Limits",
  "body": "S. R. Oates (Lancaster U.) and S. Dichiara (PSU)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 250821A\n147 s after the BAT trigger (Dichiara et al., GCN Circ. 41462).\nNo optical afterglow consistent with the XRT position\n(Evans et al., GCN Circ. 41463)\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/3sigUL\nwhite (FC)        147          297           148           >20.8\n   u (FC)        455          475           19            >18.3\nwhite             147          1715          281           >21.1\n   v             381          1593          136           >19.1\n   b             480          1692          127           >19.9\n   u             455          1667          136           >19.6\nuvw1             431          1643          58            >18.7\nuvm2             406          1618          136           >19.1\nuvw2             357          1569          136           >19.4\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.015 in the direction of the burst\n(Schlegel et al. 1998).\n\n",
  "circularId": 41471
}