{
  "subject": "GRB 250917B: Swift-XRT observations",
  "eventId": "GRB 250917B",
  "submittedHow": "email",
  "bibcode": "2025GCN.41851....1K",
  "createdOn": 1758129295591,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "circularId": 41851,
  "body": "J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.\nLeicester), B. Sbarufatti (INAF-OAB), C. Salvaggio (INAF-OAB), M. Ferro\n(INAF-OAB), D.N. Burrows (PSU), S. Lanava (PSU) and P.A. Evans (U.\nLeicester) reports on behalf of the Swift-XRT team:\n\nWe have analysed 5.5 ks of Photon Counting (PC) mode XRT data for GRB\n250917B, collected between T0+142 s and T0+28.4 ks. \n\nThree uncatalogued X-ray sources have been detected within the\nestimated 3-sigma Swift-BAT error region (296 arcsec), however none of\nthem is above the RASS limit or shows definitive signs of fading.\nTherefore, at the present time we cannot identify which, if any, is the\nafterglow. Details of these sources are given below:\n\nSource 1:\n  RA (J2000.0):  291.3458  =  19h 25m 23.00s\n  Dec (J2000.0): +11.1151  =  +11d 06' 54.5\"\n  Error: 5.5 arcsec (radius, 90% conf. [Enhanced position])\n  Count-rate: (5.5 [+1.3, -1.2])e-3 ct s^-1   \n  Distance: 113 arcsec from Swift-BAT position.\n  Flux: (1.26 [+0.30, -0.28])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 5:\n  RA (J2000.0):  291.3929  =  19h 25m 34.30s\n  Dec (J2000.0): +11.0748  =  +11d 04' 29.2\"\n  Error: 7.7 arcsec (radius, 90% conf.)\n  Count-rate: (4.6 [+5.4, -3.9])e-4 ct s^-1   \n  Distance: 147 arcsec from Swift-BAT position.\n\nSource 6:\n  RA (J2000.0):  291.4312  =  19h 25m 43.49s\n  Dec (J2000.0): +11.1014  =  +11d 06' 05.0\"\n  Error: 8.3 arcsec (radius, 90% conf.)\n  Count-rate: (7.4 [+6.4, -4.8])e-4 ct s^-1   \n  Distance: 192 arcsec from Swift-BAT position.\n  Flux: (1.47 [+1.27, -0.95])e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nThree uncatalogued sources were also detected too far from the GRB\nposition to 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/01350381.\n\nThis circular is an official product of the Swift-XRT team.\n\n"
}