{
  "bibcode": "2017GCN.20918....1K",
  "body": "J.A. Kennea (PSU), P.A. Evans (U. Leicester), S.L. Gibson (U.\nLeicester), J.P. Osborne (U. Leicester), V. D'Elia (ASDC), A. D'Ai\n(INAF-IASFPA), A. Melandri (INAF-OAB), B. Sbarufatti (INAF-OAB/PSU),\nD.N. Burrows (PSU) and\treport on behalf of the Swift-XRT team: report\non behalf of the Swift-XRT team:\n\nWe have analysed 7.2 ks of XRT data for GRB 170318B, from 64 s to 41.1\nks after the  BAT trigger. The data comprise 95 s in Windowed Timing\n(WT) mode (the first 8 s were taken while Swift was slewing) with the\nremainder in Photon Counting (PC) mode. \n\nThe light curve can be modelled with an initial rise, with a power-law\nindex of alpha=-0.5 (+0.4, -0.5), followed by a break at T+134 s  to an\nalpha of 2.96 (+0.16, -0.15).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.6 (+/-0.4). The\nbest-fitting absorption column is  6.4 (+1.7, -1.4) x 10^22 cm^-2, in\nexcess of the Galactic value of 1.4 x 10^22 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.3 (+/-0.6) and a\nbest-fitting absorption column of 6.2 (+2.1, -1.7) x 10^22 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 8.0 x 10^-11 (3.5 x 10^-10) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     6.2 (+2.1, -1.7) x 10^22 cm^-2\nGalactic foreground: 1.4 x 10^22 cm^-2\nExcess significance: 4.6 sigma\nPhoton index:\t     2.3 (+/-0.6)\n\nIf the light curve continues to decay with a power-law decay index of\n2.96, the count rate at T+24 hours will be 4.5 x 10^-8 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.6 x\n10^-18 (1.6 x 10^-17) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00743086.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 20918,
  "createdOn": 1489900153000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 170318B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 170318B"
}