{
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of P.A. Evans at U. Leicester <pae9@leicester.ac.uk>",
  "version": 2,
  "body": "J.P. Osborne (U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi \n(INAF-IASFPA) , M. Capalbi (INAF-OAR), D.N. Burrows (PSU), S. Lanava\n(PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A. Evans (U.\nLeicester) reports on behalf of the Swift-XRT team:\n\nSwift-XRT has performed a second epoch of follow-up observations of GRB\n260204A (Pillas et al., GCN Circ. 43613), collecting a further 2.6 ks\nbetween T0+363 ks and T0+458 ks. \"Source 1\" (Evans et al., GCN Circ.\n43622), which corresponds to the fading optical counterpart (Li et al.,\nGCN Circs 43620, 43623), is no longer detected and has faded with\n>3-sigma significance. The upper limit is 6.97e-3 ct/sec, compared to\nthe previous detection level of (2.36 +/- 0.46)e-2 ct/sec, giving a\npower-law decay index of alpha >0.4.\n\nUsing 1659 s of PC mode data and 1 UVOT image, we find an enhanced XRT\nposition (using the XRT-UVOT alignment and matching UVOT field sources\nto the USNO-B1 catalogue): RA, Dec = 205.10623, +1.93075 which is\nequivalent to:\n\nRA (J2000): 13h 40m 25.49s\nDec(J2000): +01d 55' 50.7\"\n\nwith an uncertainty of 4.4 arcsec (radius, 90% confidence). \n\nThe results of the XRT-team automatic analysis are available at\nhttps://www.swift.ac.uk/xrt_products/03000405.\nThe results of the full analysis of the XRT observations are available\nat https://www.swift.ac.uk/SVOM/SVOM_FIELD00057.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "eventId": "GRB 260204A",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "createdOn": 1770712470589,
  "subject": "GRB 260204A: Swift-XRT afterglow detection",
  "circularId": 43678,
  "bibcode": "2026GCN.43678....1O",
  "format": "text/plain",
  "editedOn": 1770741479946,
  "submittedHow": "email"
}