{
  "bibcode": "2019GCN.25961....1T",
  "body": "A. Tohuvavohu (U. Toronto), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), E. Ambrosi\t(INAF-IASFPA) , M. Capalbi (INAF-IASFPA), M.\nPerri (ASDC), J.A. Kennea (PSU), B. Sbarufatti (PSU), \n and S.B. Cenko report on behalf of the Swift-XRT team:\n\nWe have analysed 8.6 ks of XRT data for GRB 191004B (Cenko et al. GCN\nCirc. 25947), from 63 s to 102.9 ks after the  BAT trigger. The data\ncomprise 142 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Beardmore et al. (GCN Circ. 25951).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=2.9 (+0.6, -0.7), followed by a break at T+94.6 s to an\nalpha of 1.073 (+0.031, -0.027).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.75 (+0.09, -0.07). The\nbest-fitting absorption column is  1.4 (+6.8, -1.4) x 10^21 cm^-2, at a\nredshift of 3.503, in addition to the Galactic value of 1.9 x 10^20\ncm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index\nof 1.54 (+0.21, -0.14) and a best-fitting absorption column of 2 (+178,\n-2) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 4.2 x 10^-11 (4.3 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nGalactic foreground: 1.9 x 10^20 cm^-2\nIntrinsic column:    2 (+178, -2) x 10^20 cm^-2 at z=3.503\nPhoton index:\t     1.54 (+0.21, -0.14)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00927839.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 25961,
  "createdOn": 1570365704000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 191004B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 191004B"
}