{
  "bibcode": "2020GCN.27923....1D",
  "body": "A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A.\nTohuvavohu (U. Toronto), A.P. Beardmore (U. Leicester), P.A. Evans (U.\nLeicester), J.P. Osborne (U. Leicester), A. Melandri (INAF-OAB), T.\nSbarrato (INAF-OAB) and E. Sonbas report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 7.4 ks of XRT data for GRB 200612A (Sonbas et al. GCN\nCirc. 27915), from 93 s to 63.5 ks after the  BAT trigger. The data\ncomprise 281 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Osborne et al. (GCN Circ. 27921).\n\nThe late-time light curve (from T0+3.7 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.37 (+/-0.09).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.07 (+/-0.05). The\nbest-fitting absorption column is  9.1 (+2.3, -2.1) x 10^20 cm^-2, in\nexcess of the Galactic value of 3.7 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 2.06 (+0.19, -0.17)\nand a best-fitting absorption column of 5.7 (+4.1, -2.0) x 10^20 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.1 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     5.7 (+4.1, -2.0) x 10^20 cm^-2\nGalactic foreground: 3.7 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     2.06 (+0.19, -0.17)\n\nIf the light curve continues to decay with a power-law decay index of\n1.37, the count rate at T+24 hours will be 0.010 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.2 x\n10^-13 (3.7 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/00977310.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 27923,
  "createdOn": 1592007232000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 200612A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 200612A"
}