{
  "bibcode": "2015GCN.18583....1B",
  "body": "D.N. Burrows (PSU), T.G.R. Roegiers (PSU), S.L. Gibson (U. Leicester),\nJ.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri\n(INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC) and L.M. McCauley\nreport on behalf of the Swift-XRT team:\n\nWe have analysed 16 ks of XRT data for GRB 151111A (McCauley et al. GCN\nCirc. 18578), from 63 s to 45.5 ks after the  BAT trigger. The data\ncomprise 284 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. 18579).\n\nThe late-time light curve (from T0+5.3 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.2 (+/-0.4).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.28 (+/-0.05). The\nbest-fitting absorption column is  3.7 (+1.9, -1.7) x 10^20 cm^-2, in\nexcess of the Galactic value of 1.1 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.74 (+0.19, -0.18)\nand a best-fitting absorption column of 5.0 (+4.8, -3.9) x 10^20 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.7 x 10^-11 (4.1 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     5.0 (+4.8, -3.9) x 10^20 cm^-2\nGalactic foreground: 1.1 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.74 (+0.19, -0.18)\n\nIf the light curve continues to decay with a power-law decay index of\n1.2, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.8 x\n10^-14 (8.4 x 10^-14) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00663074.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 18583,
  "createdOn": 1447287088000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 151111A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 151111A"
}