{
  "circularId": 39856,
  "createdOn": 1742749042894,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "GRB 250321B",
  "bibcode": "2025GCN.39856....1C",
  "submittedHow": "email",
  "body": "M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), S. Dichiara\n(PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester),\nA.P. Beardmore (U. Leicester), V. D'Elia (SSDC & INAF-OAR) and P.A.\nEvans (U. Leicester) reports on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nSVOM/ECLAIRs-detected burst GRB 250321B, collecting  2.7 ks of Photon\nCounting (PC) mode data between T0+81.0 ks and T0+92.8 ks. \n\nNo X-ray sources have been detected. The 3-sigma upper limit in the\nfield ranges from ~0.005 to ~0.006 ct s^-1, corresponding to a 0.3-10\nkeV observed flux of 2.1e-13 to 2.4e-13 erg cm^-2 s^-1 (assuming a\ntypical GRB spectrum).\n\nThe results of the XRT-team automatic analysis of the XRT observations,\nincluding a position-specific upper limit calculator, are available at\nhttps://www.swift.ac.uk/ToO_GRBs/00021824.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "subject": "GRB 250321B: Swift-XRT observations"
}