{
  "subject": "GRB 231205B: Swift-XRT refined Analysis",
  "bibcode": "2023GCN.35291....1D",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "submittedHow": "email",
  "createdOn": 1701876396656,
  "eventId": "GRB 231205B",
  "body": "S. Dichiara (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.\nLeicester), E. Ambrosi\t(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M.\nPerri (SSDC & INAF-OAR), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto)\nand P.A. Evans report on behalf of the Swift-XRT team:\n\nWe have analysed 6.5 ks of XRT data for GRB 231205B, from 224 s to 68.4\nks after the  BAT trigger. The data comprise 3 s in Windowed Timing\n(WT) mode (taken while Swift was slewing), with the remainder in Photon\nCounting (PC) mode. \n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=0.27 (+0.04, -0.05), followed by a break at T+6137 s to\nan alpha of 1.32 (+/-0.08).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.06 (+/-0.10). The\nbest-fitting absorption column is  4.5 (+/-0.5) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.8 x 10^-11 (6.2 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     4.5 (+/-0.5) x 10^21 cm^-2\nGalactic foreground: 1.5 x 10^21 cm^-2\nExcess significance: 9.6 sigma\nPhoton index:\t     2.06 (+/-0.10)\n\nIf the light curve continues to decay with a power-law decay index of\n1.32, the count rate at T+24 hours will be 0.063 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x\n10^-12 (3.9 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01200812.\n\nThis circular is an official product of the Swift-XRT team.\n",
  "circularId": 35291
}