{
  "bibcode": "2018GCN.22837....1S",
  "body": "B. Sbarufatti (INAF-OAB/PSU), D.N. Burrows (PSU), K.L. Page (U.\nLeicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester),\nV. D'Elia (ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), A.\nTohuvavohu (PSU) and S.L. Gibson report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 10 ks of XRT data for GRB 180624A (Gibson et al. GCN\nCirc. 22832), from 118 s to 23.6 ks after the  BAT trigger. The data\ncomprise 538 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Goad et al. (GCN Circ. 22835).\n\nThe late-time light curve (from T0+3.9 ks) can be modelled with a\npower-law decay with a decay index of alpha=0.84 (+0.12, -0.11).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.472 (+/-0.025). The\nbest-fitting absorption column is  1.53 (+/-0.11) x 10^21 cm^-2, in\nexcess of the Galactic value of 4.6 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.08 (+0.19, -0.18)\nand a best-fitting absorption column of 1.3 (+/-0.5) x 10^21 cm^-2. The\ncounts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.2 x 10^-11 (4.2 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     1.3 (+/-0.5) x 10^21 cm^-2\nGalactic foreground: 4.6 x 10^20 cm^-2\nExcess significance: 3.0 sigma\nPhoton index:\t     2.08 (+0.19, -0.18)\n\nIf the light curve continues to decay with a power-law decay index of\n0.84, the count rate at T+24 hours will be 0.013 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.2 x\n10^-13 (5.5 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/00844192.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 22837,
  "createdOn": 1529885426000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 180624A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 180624A"
}