{
  "subject": "GRB 160131A: Swift-XRT refined Analysis",
  "eventId": "GRB 160131A",
  "bibcode": "2016GCN.18963....1G",
  "createdOn": 1454272358000,
  "circularId": 18963,
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "email": "pae9@leicester.ac.uk",
  "body": "S.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri\n(INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), D.N. Burrows\n(PSU), T.G.R. Roegiers (PSU), L.M. McCauley (PSU) and K.L. Page report\non behalf of the Swift-XRT team:\n\nWe have analysed 10 ks of XRT data for GRB 160131A (Page et al. GCN\nCirc. 18951), from 60 s to 23.6 ks after the  BAT trigger. The data\ncomprise 523 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 Goad et al.\n(GCN Circ. 18958).\n\nThe late-time light curve (from T0+3.8 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.09 (+/-0.05).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.44 (+/-0.03). The\nbest-fitting absorption column is  1.76 (+/-0.15) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.10 (+/-0.08) and a\nbest-fitting absorption column of 2.56 (+0.31, -0.29) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.4 x 10^-11 (5.2 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     2.56 (+0.31, -0.29) x 10^21 cm^-2\nGalactic foreground: 1.1 x 10^21 cm^-2\nExcess significance: 7.9 sigma\nPhoton index:\t     2.10 (+/-0.08)\n\nIf the light curve continues to decay with a power-law decay index of\n1.09, the count rate at T+24 hours will be 0.053 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.8 x\n10^-12 (2.8 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/00672236.\n\nThis circular is an official product of the Swift-XRT team."
}