{
  "body": "A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB),\nS. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U.\nLeicester), A.P. Beardmore (U. Leicester) and P.A. Evans (U. Leicester)\nreports on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nSwift/BAT-detected burst GRB 250331D, collecting  5.3 ks of Photon\nCounting (PC) mode data between T0+45.2 ks and T0+68.1 ks. \n\nTwo uncatalogued X-ray sources have been detected within the estimated\n3-sigma Swift/BAT error region (493 arcsec), however none of them is\nabove the RASS limit or shows definitive signs of fading. Therefore, at\nthe present time we cannot identify which, if any, is the afterglow.\nDetails of these sources are given below:\n\nSource 2:\n  RA (J2000.0):  48.6572  =  03:14:37.72\n  Dec (J2000.0): +62.2833  =  +62:16:59.7\n  Error: 3.5 arcsec (radius, 90% conf. [Enhanced position])\n  Count-rate: (7.4 [+1.6, -1.4])e-3 ct s^-1   \n  Distance: 235 arcsec from Swift/BAT position.\n  Flux: (3.18 [+0.67, -0.61])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nSource 4:\n  RA (J2000.0):  48.7705  =  03:15:4.93\n  Dec (J2000.0): +62.3734  =  +62:22:24.1\n  Error: 5.9 arcsec (radius, 90% conf.)\n  Count-rate: (1.77 [+0.95, -0.72])e-3 ct s^-1\t \n  Distance: 476 arcsec from Swift/BAT position.\n  Flux: (1.19 [+0.64, -0.49])e-10 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\nA catalogued source was also detected within the estimated 3-sigma\nSwift/BAT error region (493 arcsec).\n\nTwo 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/ToO_GRBs/00021825.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "circularId": 39998,
  "bibcode": "2025GCN.39998....1M",
  "eventId": "GRB 250331D",
  "createdOn": 1743497982200,
  "subject": "GRB 250331D: Swift-XRT observations",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "submittedHow": "email"
}