{
  "bibcode": "2025GCN.41449....1S",
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "eventId": "GRB 250813B",
  "submittedHow": "web",
  "format": "text/plain",
  "subject": "GRB 250813B: Swift/UVOT Upper Limit",
  "createdOn": 1755703044645,
  "circularId": 41449,
  "body": "M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:\n\nThe Swift/UVOT began settled observations of the field of GRB 250813B 9.6 ks after the SVOM/ECLAIRs trigger (Xie et al., GCN Circ. 41352). We do not detect any afterglow consistent with the XRT position (Page et al., GCN Circ. 41359) or optical position (Jelinek et al., GCN Circ. 41355).\n\nPreliminary detections and 3-sigma upper limits using the UVOT photometric system\n(Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: \n\nFilter         T_start(s)   T_stop(s)      Exp(s)           Mag\n\nu                 9599        16347         1576           >21.07\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.072 in the direction of the burst\n(Schlegel et al. 1998)."
}