{
  "bibcode": "2022GCN.31477....1K",
  "body": "J.A. Kennea (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U.\nLeicester), K.L. Page (U. Leicester), P. D'Avanzo (INAF-OAB), M.G.\nBernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA) , A. Tohuvavohu (U.\nToronto), B. Sbarufatti (PSU) and A. Melandri report on behalf of the\nSwift-XRT team:\n\nWe have analysed 7.4 ks of XRT data for GRB 220117A (Melandri et al.\nGCN Circ. 31466), from 142 s to 51.2 ks after the  BAT trigger. The\ndata comprise 98 s in Windowed Timing (WT) mode (the first 8 s were\ntaken while Swift was slewing) with the remainder in Photon Counting\n(PC) mode. The enhanced XRT position for this burst was given by\nBeardmore et al. (GCN Circ. 31472).\n\nThe late-time light curve (from T0+4.3 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.48 (+0.11, -0.10).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.69 (+/-0.10). The\nbest-fitting absorption column is  1.95 (+0.24, -0.23) x 10^21 cm^-2,\nin excess of the Galactic value of 2.6 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.80 (+/-0.11) and a\nbest-fitting absorption column of 4.5 (+2.6, -1.9) 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 (3.8 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     4.5 (+2.6, -1.9) x 10^20 cm^-2\nGalactic foreground: 2.6 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.80 (+/-0.11)\n\nIf the light curve continues to decay with a power-law decay index of\n1.48, the count rate at T+24 hours will be 6.5 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.3 x\n10^-13 (2.5 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/01093592.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 31477,
  "createdOn": 1642496764000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 220117A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 220117A"
}