{
  "bibcode": "2021GCN.30069....1P",
  "body": "M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai\n(INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U.\nToronto), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester)\nand P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nFermi/LAT-detected burst GRB 210520A (Di Lalla et al. GCN Circ. 30062)\nin a series of observations tiled on the sky. The total exposure time\nis 5.6 ks, distributed over 19 tiles; the maximum exposure at a single\nsky location was 649 s. The data were collected between T0+43.1 ks and\nT0+62 ks, and are entirely in Photon Counting (PC) mode. \n\nTwo uncatalogued X-ray sources are detected above the RASS 3-sigma\nupper limit at this position, matching the afterglow criteria. However,\nnone of them shows definitive signs of fading, and both of them are\nconsistent with 2MASS objects within the XRT error circle. Therefore,\nnone of them is likely the afterglow.\n\nDetails of these sources are given below:\n\nSource 2:\n  RA (J2000.0):  122.12040 = 08:08:28.90\n  Dec (J2000.0): -69.7668 = -69:46:00.5\n  Error: 7.7 arcsec (radius, 90% conf.)\n  Count-rate: (1.95 [+1.19, -0.85])e-2 ct s^-1\t \n  Distance: 28.7' from Fermi/LAT position.\n\nSource 3:\n  RA (J2000.0):  124.47176 =  08:17:53.22\n  Dec (J2000.0): -69.2963  =  -69:17:46.8\n  Error: 8.6 arcsec (radius, 90% conf.)\n  Count-rate: (3.0 [+1.6, -1.1])e-2 ct s^-1\t \n  Distance: 31.8' from Fermi/LAT position.\n\nThe results of the full analysis of the tiled XRT observations are\navailable at https://www.swift.ac.uk/xrt_products/TILED_GRB00099.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 30069,
  "createdOn": 1621680444000,
  "email": "paolo.davanzo@inaf.it",
  "subject": "GRB 210520A: Swift-XRT observations",
  "submitter": "Paolo D'Avanzo at INAF - OAB  <paolo.davanzo@inaf.it>",
  "eventId": "GRB 210520A"
}