{
  "body": "S. Lanava (PSU), J.P. Osborne (U. Leicester), E. Ambrosi  (INAF-IASFPA)\n, M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), S. Dichiara (PSU),\nJ.A. Kennea (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.\nLeicester) and P.A. Evans (U. Leicester) reports on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nSVOM/ECLAIRs-detected burst GRB 260903A, collecting  3.9 ks of Photon\nCounting (PC) mode data between T0+498.4 ks and T0+554.5 ks. \n\nNo X-ray sources have been detected at the position of the optical\nafterglow (Li et al. GCN 45504, Saccardi et al. GCN 45505, Malesani et\nal. GCN 45508, Russeil et al. GCN 45509, Li et al. GCN 45510, Bochenek\net al. GCN 45516). The 3-sigma upper limit in the field is 0.002 ct \ns^-1, corresponding to a 0.3-10 keV observed flux of 8.1e-14 erg cm^-2\ns^-1 (assuming a typical GRB spectrum).\n\nFour uncatalogued sources were detected too far from the GRB position\nto be likely afterglow candidates.\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/00021910.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "createdOn": 1789052225926,
  "submittedHow": "email",
  "subject": "GRB 260903A: Swift-XRT observations",
  "bibcode": "2026GCN.45548....1L",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "circularId": 45548,
  "eventId": "GRB 260903A"
}