{
  "circularId": 42096,
  "createdOn": 1759508196198,
  "subject": "GRB 251003A: Swift-XRT refined Analysis",
  "submittedHow": "email",
  "body": "D.N. Burrows (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , M.\nCapalbi (INAF-OAR), S. Lanava (PSU), S. Dichiara (PSU) and P.A. Evans\nreport on behalf of the Swift-XRT team:\n\nWe have analysed 6.8 ks of XRT data for GRB 251003A, from 59 s to 34.6\nks after the   trigger. The data comprise 126 s in Windowed Timing (WT)\nmode (the first 8 s were taken while Swift was slewing) with the\nremainder in Photon Counting (PC) mode. \n\nThe late-time light curve (from T0+4.6 ks) can be modelled with a\npower-law decay with a decay index of alpha=0.6 (+0.4, -0.3).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.67 (+0.11, -0.10). The\nbest-fitting absorption column is  1.4 (+3.0, -1.4) x 10^22 cm^-2, at a\nredshift of 4.412, in addition to the Galactic value of 4.4 x 10^21\ncm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed)\n0.3-10 keV flux conversion factor deduced from this spectrum  is 2.8 x\n10^-11 (7.5 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the WT-mode spectrum is thus:\nGalactic foreground: 4.4 x 10^21 cm^-2\nIntrinsic column:    1.4 (+3.0, -1.4) x 10^22 cm^-2 at z=4.412\nPhoton index:\t     2.67 (+0.11, -0.10)\n\nIf the light curve continues to decay with a power-law decay index of\n0.6, the count rate at T+24 hours will be 8.2 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x\n10^-13 (6.1 x 10^-13) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01400964.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "bibcode": "2025GCN.42096....1B",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "GRB 251003A"
}