{
  "circularId": 41720,
  "createdOn": 1757065893023,
  "bibcode": "2025GCN.41720....1S",
  "format": "text/plain",
  "body": "S. P. R. Shilling (Lancaster U.) reports on behalf of the Swift/UVOT team:\n\nSwift/UVOT has performed follow-up observations of the SVOM/ECLAIRs-detected source\nGRB 250903A. Swift/UVOT observed the field of GRB 250903A (Maiolino et al., GCN 41677) for 2.3 ks\nin the U-band starting at 20:57:46 UT, 3.5 hours after the detection by SVOM/ECLAIRs.\n\nA source consistent with the TRT optical counterpart position (An et al., GCN 41679), within\nthe SVOM/ECLAIRs error circle, is detected and is fading. The preliminary detection magnitude\nreported below is calculated using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373).\n\nFilter         T_start(s)   T_stop(s)      Exp(s)        Mag\n\nu              12770        24862          2330          19.71 +/- 0.11",
  "subject": "GRB 250903A: Swift/UVOT detection",
  "eventId": "GRB 250903A",
  "submitter": "s.shilling@lancaster.ac.uk",
  "submittedHow": "web"
}