{
  "submittedHow": "web",
  "bibcode": "2025GCN.42209....1S",
  "format": "text/plain",
  "createdOn": 1760284611552,
  "eventId": "GRB 251011B",
  "body": "M. H. Siegel (PSU) and A. D'Ai (INAF-IASFPA)\nreport on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 251011B 107 s after the BAT trigger (D'Ai et al., GCN Circ. 42197). No optical afterglow consistent with the XRT position (Evans et al., GCN Circ. 42201) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (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           107          257          147         >20.9\nwhite              107          257          147         >20.9\nu                  320          463          141         >20.4\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.017 in the direction of the burst\n(Schlegel et al. 1998).",
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "circularId": 42209,
  "subject": "GRB 251011B: Swift/UVOT Upper Limits"
}