{
  "bibcode": "2015GCN.18509....1D",
  "body": "V. D'Elia (ASDC), A. D'ai (INAF-IASFPA), A. Maselli  (INAF-IASFPA),\nL.M. McCauley (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),\nC. Pagani (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U.\nLeicester) and T.N. Ukwatta report on behalf of the Swift-XRT team:\n\nWe have analysed 12 ks of XRT data for GRB 151027B (Ukwatta et al. GCN\nCirc. 18499), from 191 s to 32.5 ks after the  BAT trigger. The data\ncomprise 61 s in Windowed Timing (WT) mode (the first 8 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. 18504).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=5.7 (+/-0.6), followed by a break at T+332 s to an alpha\nof 0.66 (+0.05, -0.06).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.81 (+0.14, -0.13). The\nbest-fitting absorption column is  4.1 (+2.5, -2.2) x 10^22 cm^-2, at a\nredshift of 4.063, in addition to the Galactic value of 9.4 x 10^20\ncm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed)\n0.3-10 keV flux conversion factor deduced from this spectrum  is 3.8 x\n10^-11 (4.8 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nGalactic foreground: 9.4 x 10^20 cm^-2\nIntrinsic column:    4.1 (+2.5, -2.2) x 10^22 cm^-2 at z=4.063\nPhoton index:\t     1.81 (+0.14, -0.13)\n\nIf the light curve continues to decay with a power-law decay index of\n0.66, the count rate at T+24 hours will be 0.026 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 9.9 x\n10^-13 (1.2 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/00661869.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 18509,
  "createdOn": 1446029829000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 151027B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 151027B"
}