{
  "bibcode": "2018GCN.22560....1M",
  "body": "A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), V. D'Elia (ASDC), S. J.\nLaPorte (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU), A.P.\nBeardmore (U. Leicester), P.A. Evans (U. Leicester), S.L. Gibson (U.\nLeicester) and J.L. Racusin report on behalf of the Swift-XRT team:\n\nWe have analysed 7.4 ks of XRT data for GRB 180329B (Racusin et al. GCN\nCirc. 22558), from 109 s to 17.7 ks after the  BAT trigger. The data\ncomprise 260 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. 22559).\n\nThe late-time light curve (from T0+4.6 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.14 (+/-0.12).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.54 (+/-0.04). The\nbest-fitting absorption column is  7.5 (+1.4, -1.3) x 10^20 cm^-2, in\nexcess of the Galactic value of 2.5 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.86 (+/-0.11) and a\nbest-fitting absorption column of 6.5 (+2.8, -2.6) x 10^20 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.5 x 10^-11 (4.0 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     6.5 (+2.8, -2.6) x 10^20 cm^-2\nGalactic foreground: 2.5 x 10^20 cm^-2\nExcess significance: 2.6 sigma\nPhoton index:\t     1.86 (+/-0.11)\n\nIf the light curve continues to decay with a power-law decay index of\n1.14, the count rate at T+24 hours will be 0.012 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.4 x\n10^-13 (5.0 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/00819490.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 22560,
  "createdOn": 1522358088000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 180329B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 180329B"
}