{
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "body": "S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U.\nLeicester), A.P. Beardmore (U. Leicester), T. Sbarrato (INAF-OAB), P.\nD'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB) and P.A. Evans report\non behalf of the Swift-XRT team:\n\nWe have analysed 7.8 ks of XRT data for GRB 251001B, from 99 s to 40.1\nks after the   trigger. The data comprise 540 s in Windowed Timing (WT)\nmode (the first 10 s were taken while Swift was slewing) with the\nremainder in Photon Counting (PC) mode. \n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.34 (+/-0.06).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.92 (+0.08, -0.07). The\nbest-fitting absorption column is  8.8 (+2.0, -1.9) x 10^20 cm^-2, in\nexcess of the Galactic value of 2.6 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.74 (+0.19, -0.18)\nand a best-fitting absorption column of 8.6 (+5.7, -4.8) x 10^20 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.9 x 10^-11 (4.5 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     8.6 (+5.7, -4.8) x 10^20 cm^-2\nGalactic foreground: 2.6 x 10^20 cm^-2\nExcess significance: 2.1 sigma\nPhoton index:\t     1.74 (+0.19, -0.18)\n\nIf the light curve continues to decay with a power-law decay index of\n1.34, the count rate at T+24 hours will be 9.6 x 10^-4 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.8 x\n10^-14 (4.3 x 10^-14) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01400467.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "circularId": 42052,
  "subject": "GRB 251001B: Swift-XRT refined Analysis",
  "submittedHow": "email",
  "createdOn": 1759391536559,
  "bibcode": "2025GCN.42052....1D",
  "eventId": "GRB 251001B"
}