{
  "bibcode": "2017GCN.20620....1L",
  "body": "S. J. LaPorte (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU),\nS.L. Gibson (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo\n(INAF-OAB) and A.Y. Lien report on behalf of the Swift-XRT team:\n\nWe have analysed 7.4 ks of XRT data for GRB 170206B (Lien et al. GCN\nCirc. 20618), from 88 s to 24.5 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. Using 2057 s\nof PC mode data and 3 UVOT images, we find an enhanced XRT position\n(using the XRT-UVOT alignment and matching UVOT field sources to the\nUSNO-B1 catalogue): RA, Dec = 271.77062, +11.19383 which is equivalent\nto:\n\nRA (J2000): 18h 07m 04.95s\nDec(J2000): +11d 11' 37.8\"\n\nwith an uncertainty of 1.6 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=2.48 (+0.19, -0.20).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.46 (+0.18, -0.17). The\nbest-fitting absorption column is  4.9 (+0.8, -0.7) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.1 x 10^21 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.1 x 10^-11 (6.9 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the WT-mode spectrum is thus:\nTotal column:\t     4.9 (+0.8, -0.7) x 10^21 cm^-2\nGalactic foreground: 1.1 x 10^21 cm^-2\nExcess significance: 8.5 sigma\nPhoton index:\t     2.46 (+0.18, -0.17)\n\nIf the light curve continues to decay with a power-law decay index of\n2.48, the count rate at T+24 hours will be 2.5 x 10^-7 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.8 x\n10^-18 (1.8 x 10^-17) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00737125.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 20620,
  "createdOn": 1486460801000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 170206B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 170206B"
}