{
  "bibcode": "2021GCN.29449....1P",
  "body": "M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai\n(INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A. Kennea\n(PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P.\nOsborne (U. Leicester) and S. Laha report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 6.3 ks of XRT data for GRB 210209A (Laha et al. GCN\nCirc. 29442), from 122 s to 24.0 ks after the  BAT trigger. The data\ncomprise 139 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Evans et al. (GCN Circ. 29443).\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=0.88 (+/-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 1.81 (+0.07, -0.04). The\nbest-fitting absorption column is  consistent with the Galactic value\nof 3.7 x 10^21 cm^-2 (Willingale et al. 2013). The PC mode spectrum has\na photon index of 1.91 (+0.07, -0.05) and a best-fitting absorption\ncolumn consistent with the Galactic value. The counts to observed\n(unabsorbed) 0.3-10 keV flux conversion factor deduced from this\nspectrum  is 4.0 x 10^-11 (5.6 x 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.67 (+0.14, -0.00) x 10^21 cm^-2\nGalactic foreground: 3.7 x 10^21 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.91 (+0.07, -0.05)\n\nIf the light curve continues to decay with a power-law decay index of\n0.88, the count rate at T+24 hours will be 0.046 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.9 x\n10^-12 (2.6 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01031636.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 29449,
  "createdOn": 1612944813000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 210209A: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 210209A"
}