{
  "bibcode": "2012GCN.14016....1S",
  "body": "G. Stratta (ASDC), D.N. Burrows (PSU), J.A. Kennea (PSU), M.C. Stroh\n(PSU), O.M. Littlejohns (U. Leicester), J.P. Osborne (U. Leicester),\nK.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and\nS.R. Oates report on behalf of the Swift-XRT team:\n\nWe have analysed 12 ks of XRT data for GRB 121128A (Oates  et al. GCN\nCirc. 14007), from 66 s to 41.5 ks after the  BAT trigger. The data\ncomprise 108 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 Osborne et\nal. (GCN. Circ 14015).\n\nThe late-time light curve (from T0+6.9 ks) can be modelled with  a\npower-law decay with a decay index of alpha=1.67 (+0.16, -0.15).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.43 (+/-0.11). The\nbest-fitting absorption column is  1.2 (+/-0.4) x 10^22 cm^-2, at a\nredshift of 2.2, in addition to the Galactic value of 2.1 x 10^21 cm^-2\n(Kalberla et al. 2005). The PC mode spectrum has a photon index of 1.99\n(+0.10, -0.09) and a best-fitting absorption column of 1.1 (+0.5, -0.4)\nx 10^22 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 4.1 x 10^-11 (6.4 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nGalactic foreground: 2.1 x 10^21 cm^-2\nIntrinsic column:    1.1 (+0.5, -0.4) x 10^22 cm^-2 at z=2.2\nPhoton index:\t     1.99 (+0.10, -0.09)\n\nIf the light curve continues to decay with a power-law decay index of\n1.59, the count rate at T+24 hours will be 3.2 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.3 x\n10^-13 (2.1 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/00539866.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 14016,
  "createdOn": 1354137484000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 121128A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 121128A"
}