{
  "bibcode": "2016GCN.19894....1M",
  "body": "A. Melandri (INAF-OAB), D.N. Burrows (PSU), T.G.R. Roegiers (PSU), L.M.\nMcCauley (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester),\nB. Mingo (U. Leicester), V. D'Elia (ASDC) and P. D'Avanzo report on\nbehalf of the Swift-XRT team:\n\nWe have analysed 7.2 ks of XRT data for GRB 160905A (D'Avanzo et al.\nGCN Circ. 19887), from 50 s to 29.8 ks after the  BAT trigger. The data\ncomprise 2.2 ks in Windowed Timing (WT) mode (the first 6 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. The enhanced XRT position for this burst was given by Osborne et\nal. (GCN Circ. 19891).\n\nThe late-time light curve (from T0+5.6 ks) can be modelled with a\nseries of power-law decays. The initial decay index is alpha=0.5 (+0.6,\n-0.4). At T+7998 s  the decay steepens to an alpha of 7.92 (+0.08,\n-5.15). The light curve breaks again at T+9660 s to a decay with\nalpha=-1.5 (+0.0, -0.4),  before a final break at T+15.0 ks s after\nwhich the decay index is 1.0 (+/-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 1.729 (+/-0.024). The\nbest-fitting absorption column is  4.89 (+0.18, -0.17) x 10^21 cm^-2,\nin excess of the Galactic value of 3.8 x 10^21 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.84 (+0.12, -0.11)\nand a best-fitting absorption column of 5.9 (+0.9, -0.8) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 4.7 x 10^-11 (7.1 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     5.9 (+0.9, -0.8) x 10^21 cm^-2\nGalactic foreground: 3.8 x 10^21 cm^-2\nExcess significance: 4.4 sigma\nPhoton index:\t     1.84 (+0.12, -0.11)\n\nIf the light curve continues to decay with a power-law decay index of\n1.0, the count rate at T+24 hours will be 0.10 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.7 x\n10^-12 (7.1 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/00711084.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 19894,
  "createdOn": 1473120478000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 160905A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 160905A"
}