{
  "bibcode": "2016GCN.18830....1M",
  "body": "A. Melandri, P. D'Avanzo (INAF-OAB) and P.A. Evans (U. Leicester)\nreport on behalf of the Swift-XRT team:\n\nWe have analysed 7.5 ks of XRT data for GRB 160104A (Melandri et al.\nGCN Circ. 18815), from 63 s to 36.3 ks after the  BAT trigger. The data\ncomprise 914 s in Windowed Timing (WT) mode (the first 9 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 Beardmore\net al. (GCN Circ. 18821).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=3.1 +/- 0.4, followed by a break at T+269 s to an alpha\nof 0.53 (+0.14, -0.17). Flaring activity is observed between T0+200 s\nand T0+2.0 ks.\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.95 (+0.18, -0.08). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 2.7 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed\n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this\nspectrum is 3.7 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.7 (+/-0.6) x 10^21 cm^-2\nGalactic foreground: 2.7 x 10^21 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.95 (+0.18, -0.08)\n\nIf the light curve continues to decay with a power-law decay index of\n0.53, the count rate at T+24 hours will be 0.01 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.7 x\n10^-13 (5.2 x 10^-13) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00669319.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 18830,
  "createdOn": 1451994304000,
  "email": "andrea.melandri@brera.inaf.it",
  "subject": "GRB 160104A: Swift-XRT refined Analysis",
  "submitter": "Andrea Melandri at INAF-OAB  <andrea.melandri@brera.inaf.it>",
  "eventId": "GRB 160104A"
}