{
  "submittedHow": "email",
  "eventId": "GRB 250313A",
  "body": "M. A. Williams (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAR), T.\nSbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), S. Dichiara (PSU), J.A.\nKennea (PSU) and P.A. Evans (U. Leicester) reports on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nFermi/LAT-detected burst GRB 250313A, collecting  6.3 ks of Photon\nCounting (PC) mode data between T0+30.7 ks and T0+82.7 ks. \n\nSeven uncatalogued X-ray sources have been detected, 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):  278.5986  =  18:34:23.66\n  Dec (J2000.0): +53.8117  =  +53:48:42.1\n  Error: 5.7 arcsec (radius, 90% conf.)\n  Count-rate: (3.20 [+1.07, -0.89])e-3 ct s^-1\t \n  Distance: 360 arcsec from Fermi/LAT position.\n  Flux: (1.13 [+0.38, -0.32])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 2:\n  RA (J2000.0):  278.4773  =  18:33:54.54\n  Dec (J2000.0): +53.6792  =  +53:40:45.1\n  Error: 5.9 arcsec (radius, 90% conf.)\n  Count-rate: (1.23 [+0.71, -0.54])e-3 ct s^-1\t \n  Distance: 184 arcsec from Fermi/LAT position.\n  Flux: (5.1 [+2.9, -2.2])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 3:\n  RA (J2000.0):  278.7435  =  18:34:58.45\n  Dec (J2000.0): +53.8112  =  +53:48:40.2\n  Error: 6.1 arcsec (radius, 90% conf.)\n  Count-rate: (1.19 [+0.90, -0.67])e-3 ct s^-1\t \n  Distance: 560 arcsec from Fermi/LAT position.\n  Flux: (2.6 [+2.0, -1.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 4:\n  RA (J2000.0):  278.7131  =  18:34:51.13\n  Dec (J2000.0): +53.8208  =  +53:49:14.7\n  Error: 6.9 arcsec (radius, 90% conf.)\n  Count-rate: (2.16 [+0.95, -0.76])e-3 ct s^-1\t \n  Distance: 532 arcsec from Fermi/LAT position.\n  Flux: (2.38 [+1.04, -0.83])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 5:\n  RA (J2000.0):  278.5290  =  18:34:6.96\n  Dec (J2000.0): +53.8678  =  +53:52:04.2\n  Error: 8.1 arcsec (radius, 90% conf.)\n  Count-rate: (1.57 [+0.84, -0.65])e-3 ct s^-1\t \n  Distance: 532 arcsec from Fermi/LAT position.\n  Flux: (6.4 [+3.4, -2.6])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 6:\n  RA (J2000.0):  278.5496  =  18:34:11.90\n  Dec (J2000.0): +53.7202  =  +53:43:12.8\n  Error: 5.7 arcsec (radius, 90% conf.)\n  Count-rate: (1.35 [+0.73, -0.55])e-3 ct s^-1\t \n  Distance: 41 arcsec from Fermi/LAT position.\n  Flux: (8.6 [+4.7, -3.5])e-14 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 7:\n  RA (J2000.0):  278.6648  =  18:34:39.55\n  Dec (J2000.0): +53.6612  =  +53:39:40.2\n  Error: 7.4 arcsec (radius, 90% conf.)\n  Count-rate: (7.5 [+6.0, -4.6])e-4 ct s^-1   \n  Distance: 356 arcsec from Fermi/LAT position.\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/00021822.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "createdOn": 1741993585574,
  "subject": "GRB 250313A: Swift-XRT observations",
  "bibcode": "2025GCN.39723....1W",
  "circularId": 39723,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>"
}