{
  "circularId": 39750,
  "createdOn": 1742171745535,
  "eventId": "GRB 250316A",
  "subject": "GRB 250316A: Swift-XRT observations",
  "submittedHow": "email",
  "bibcode": "2025GCN.39750....1K",
  "body": "J.A. Kennea (PSU), A.P. Beardmore (U. Leicester), P. D'Avanzo\n(INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) ,\nD.N. Burrows (PSU), M. A. Williams (PSU), J.P. Osborne (U. Leicester)\nand P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the Swift/BAT\nGUANO-detected burst GRB 250316A (GCN #39744), collecting  4.3 ks of\nPhoton Counting (PC) mode data between T0+21.5 ks and T0+46.5 ks. \n\nOne uncatalogued X-ray source has been detected within the estimated\n3-sigma Swift/BAT error region (296 arcsec), it is below the RASS limit\nand shows only moderate signs of fading. Therefore, at the present time\nwe cannot confirm this as the afterglow. Details of this source are\ngiven below:\n\nSource 1:\n  RA (J2000.0):  219.5964  =  14:38:23.15\n  Dec (J2000.0): +14.8912  =  +14:53:28.2\n  Error: 3.1 arcsec (radius, 90% conf. [Enhanced position])\n  Count-rate: 0.0180 [+0.0025, -0.0024] ct s^-1   \n  Distance: 118 arcsec from Swift/BAT position.\n  Flux: (5.29 [+0.72, -0.70])e-13 erg cm^-2 s^-1 (observed, 0.3-10 keV)\n\n\nFour 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/00021823.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>"
}