{
  "bibcode": "2018GCN.22917....1D",
  "body": "A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB),\nB. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), A. Tohuvavohu (PSU),\nJ.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore\n(U. Leicester) and M. Stamatikos report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 6.1 ks of XRT data for GRB 180706A (Stamatikos et al.\nGCN Circ. 22909), from 77 s to 17.9 ks after the  BAT trigger. The data\ncomprise 169 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. 22916).\n\nThe late-time light curve (from T0+5.5 ks) can be modelled with a\npower-law decay with a decay index of alpha=0.58 (+0.21, -0.22).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 3.11 (+/-0.09). The\nbest-fitting absorption column is  1.65 (+/-0.18) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.16 (+0.17, -0.16)\nand a best-fitting absorption column of 6.7 (+3.7, -3.3) x 10^20 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.0 x 10^-11 (3.6 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     6.7 (+3.7, -3.3) x 10^20 cm^-2\nGalactic foreground: 1.4 x 10^20 cm^-2\nExcess significance: 2.6 sigma\nPhoton index:\t     2.16 (+0.17, -0.16)\n\nIf the light curve continues to decay with a power-law decay index of\n0.58, the count rate at T+24 hours will be 0.026 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x\n10^-13 (9.3 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/00846395.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 22917,
  "createdOn": 1530891534000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 180706A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 180706A"
}