{
  "bibcode": "2021GCN.30208....1G",
  "body": "J. D. Gropp (PSU), P.A. Evans (U. Leicester), J.P. Osborne (U.\nLeicester), P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E.\nAmbrosi  (INAF-IASFPA) , J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto)\nand K.L. Page report on behalf of the Swift-XRT team:\n\nWe have analysed 5.8 ks of XRT data for GRB 210610B (Page et al. GCN\nCirc. 30170), from 87 s to 81.7 ks after the  BAT trigger. The data\ncomprise 1.3 ks 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. 30189).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=1.13 (+0.23, -0.34). At T+133 s  the decay\nsteepens to an alpha of 1.86 (+0.06, -0.05). The light curve breaks\nagain at T+397 s to a decay with alpha=0.77 (+0.06, -0.05),  before a\nfinal break at T+1153 s s after which the decay index is 1.105 (+0.023,\n-0.022).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.847 (+/-0.022). The\nbest-fitting absorption column is  4.4 (+/-2.5) x 10^20 cm^-2, at a\nredshift of 1.13, in addition to the Galactic value of 3.9 x 10^20\ncm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index\nof 1.92 (+/-0.12) and a best-fitting absorption column of 1.1 (+1.4,\n-1.1) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV\nflux conversion factor deduced from this spectrum  is 3.4 x 10^-11 (3.9\nx 10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nGalactic foreground: 3.9 x 10^20 cm^-2\nIntrinsic column:    1.1 (+1.4, -1.1) x 10^21 cm^-2 at z=1.13\nPhoton index:\t     1.92 (+/-0.12)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/01054681.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 30208,
  "createdOn": 1623444508000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 210610B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 210610B"
}