{
  "bibcode": "2019GCN.23645....1B",
  "body": "A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), A. D'Ai\n(INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), A.\nTohuvavohu (PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), J.P. Osborne\n(U. Leicester) and J.D. Gropp report on behalf of the Swift-XRT team:\n\nWe have analysed 6.1 ks of XRT data for GRB 190109A (Gropp et al. GCN\nCirc. 23642), from 175 s to 13.0 ks after the  BAT trigger. The data\ncomprise 291 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. 23643).\n\nThe late-time light curve (from T0+4.8 ks) can be modelled with a\npower-law decay with a decay index of alpha=0.8 (+/-0.3).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.87 (+/-0.04). The\nbest-fitting absorption column is  9.5 (+1.3, -1.2) x 10^20 cm^-2, in\nexcess of the Galactic value of 5.1 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.88 (+0.11, -0.09)\nand a best-fitting absorption column consistent with the Galactic\nvalue. The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.5 x 10^-11 (3.8 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     5.1 (+2.1, -0.0) x 10^20 cm^-2\nGalactic foreground: 5.1 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.88 (+0.11, -0.09)\n\nIf the light curve continues to decay with a power-law decay index of\n0.8, 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 3.6 x\n10^-13 (4.0 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/00882747.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 23645,
  "createdOn": 1547033139000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 190109A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 190109A"
}