{
  "bibcode": "2023GCN.33584....1E",
  "body": "P.A. Evans (U. Leicester), T. Sbarrato (INAF-OAB), P. D'Avanzo\n(INAF-OAB), M.G. Bernardini (INAF-OAB), A. Tohuvavohu (U. Toronto),\nD.N. Burrows (PSU), J. D. Gropp (PSU), J.P. Osborne (U. Leicester) and\nK.L. Page report on behalf of the Swift-XRT team:\n\nWe have analysed 6.5 ks of XRT data for GRB 230405B (Page et al. GCN\nCirc. 33571), from 54 s to 75.0 ks after the  BAT trigger. The data\ncomprise 246 s in Windowed Timing (WT) mode (the first 10 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. The enhanced XRT position for this burst was given by Beardmore\net al. (GCN Circ. 33572).\n\nThe light curve can be modelled with an initial power-law decay with an\nindex of alpha=0.88 (+/-0.04), followed by a break at T+937 s to an\nalpha of 1.14 (+0.16, -0.05).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.10 (+0.12, -0.11). The\nbest-fitting absorption column is  4.0 (+0.6, -0.5) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.6 x 10^21 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.95 (+0.17, -0.16)\nand a best-fitting absorption column of 5.4 (+1.1, -1.0) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 4.2 x 10^-11 (6.8 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     5.4 (+1.1, -1.0) x 10^21 cm^-2\nGalactic foreground: 1.6 x 10^21 cm^-2\nExcess significance: 6.2 sigma\nPhoton index:\t     1.95 (+0.17, -0.16)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01163119.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 33584,
  "createdOn": 1680832874000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 230405B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 230405B"
}