{
  "createdOn": 1734617864278,
  "format": "text/plain",
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "body": "M. H. Siegel (PSU) and M. Williams (PSU) report on behalf of the\nSwift/UVOTteam:\n\nThe Swift/UVOT began settled observations of the field of GRB 241218A\n152 s after the BAT trigger (Williams et al., GCN Circ. 38601).\nNo optical afterglow consistent with the XRT position\n(D'Elia et al., GCN Circ. 38614) 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           152          301          147         >20.7\nu_FC               310          559          246         >19.8\nwhite              152         1014          334         >21.0\nv                  640         1411           97         >18.5\nb                  565         1337           78         >18.7\nu                  310         1312          304         >19.8\nw1                 689          709           19         >21.1\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.024 in the direction of the burst\n(Schlegel et al. 1998).",
  "eventId": "GRB 241218A",
  "subject": "GRB 241218A: Swift/UVOT Upper Limits",
  "circularId": 38634,
  "submittedHow": "web",
  "bibcode": "2024GCN.38634....1S"
}