{
  "body": "K.L. Page (U. Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC &\nINAF-OAR), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), J.A. Kennea\n(PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans\nreport on behalf of the Swift-XRT team:\n\nWe have analysed 6.2 ks of XRT data for GRB 251126A, from 66 s to 56.7\nks after the   trigger. The data comprise 9 s in Windowed Timing (WT)\nmode (taken while Swift was slewing), with the remainder in Photon\nCounting (PC) mode. \n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=3.5 (+0.6, -0.5). At T+210 s  the decay\nflattens to an alpha of -0.50 (+0.00, -0.17) before breaking again at\nT+1954 s to a final decay with index alpha=1.13 (+0.21, -0.16).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.11 (+0.25, -0.24). The\nbest-fitting absorption column is  1.7 (+0.8, -0.7) x 10^21 cm^-2, in\nexcess of the Galactic value of 9.5 x 10^20 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.3 x 10^-11 (4.6 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.7 (+0.8, -0.7) x 10^21 cm^-2\nGalactic foreground: 9.5 x 10^20 cm^-2\nExcess significance: 1.8 sigma\nPhoton index:\t     2.11 (+0.25, -0.24)\n\nIf the light curve continues to decay with a power-law decay index of\n1.13, the count rate at T+24 hours will be 8.5 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x\n10^-13 (3.9 x 10^-13) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttps://www.swift.ac.uk/xrt_products/01417793.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "subject": "GRB 251126A: Swift-XRT refined Analysis",
  "circularId": 42860,
  "createdOn": 1764248570956,
  "submittedHow": "email",
  "bibcode": "2025GCN.42860....1P",
  "eventId": "GRB 251126A"
}