{
  "bibcode": "2013GCN.15542....1E",
  "body": "P.A. Evans (U. Leicester), B.P. Gompertz (U. Leicester), A. Melandri\n(INAF-OAB), B. Sbarufatti (INAF-OAB/PSU), P. D'Avanzo (INAF-OAB), D.N.\nBurrows (PSU), J.A. Kennea (PSU), V. Mangano (PSU), J.P. Osborne (U.\nLeicester) and E. Sonbas report on behalf of the Swift-XRT team:\n\nWe have analysed 7.6 ks of XRT data for GRB 131128A (Sonbas  et al. GCN\nCirc. 15533),  from 72 s to 40.8 ks after the  BAT trigger. The data\ncomprise 7 s in Windowed Timing (WT) mode (taken while Swift was\nslewing), with the remainder in Photon Counting (PC) mode. The enhanced\nXRT position for this burst was given by Goad et al. (GCN. Circ 15538).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=1.9 (+/-0.4). At T+423 s  the decay\nflattens to an alpha of 0.38 (+0.08, -0.14) before breaking again at\nT+16.0 ks to a final decay with index alpha=1.7 (+0.7, -0.6).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.53 (+0.18, -0.12). The\nbest-fitting absorption column is  5.8 (+4.6, -0.7) x 10^20 cm^-2,\nconsistent with the Galactic value of 5.2 x 10^20 cm^-2 (Kalberla et\nal. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 4.6 x 10^-11 (5.0 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     5.8 (+4.6, -0.7) x 10^20 cm^-2\nGalactic foreground: 5.2 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.53 (+0.18, -0.12)\n\nIf the light curve continues to decay with a power-law decay index of\n1.7, the count rate at T+24 hours will be 3.8 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.7 x\n10^-13 (1.9 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/00579683.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 15542,
  "createdOn": 1385709724000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 131128A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 131128A"
}