{
  "circularId": 41661,
  "eventId": "GRB 250901A",
  "subject": "GRB 250901A: Swift/UVOT Upper Limit",
  "createdOn": 1756839412084,
  "submitter": "Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>",
  "bibcode": "2025GCN.41661....1S",
  "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 250901A 2.6 ks after the SVOM/ECLAIRs trigger (Piron et al., GCN Circ. 41634). We do not detect any afterglow consistent with the XRT position (Osborne et al., GCN Circ. 41645) or optical position (Xin et al., GCN Circ. 41646; Malesani et al., GCN Circ. 41649).\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                 2629         4244         1589           >21.01\n\nThe magnitudes in the table are not corrected for the Galactic extinction\ndue to the reddening of E(B-V) = 0.023 in the direction of the burst\n(Schlegel et al. 1998).",
  "format": "text/plain",
  "submittedHow": "web"
}