{
  "bibcode": "2021GCN.29427....1P",
  "body": "K.L. Page (U. Leicester), M. Capalbi (INAF-IASFPA), M. Perri (SSDC &\nINAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (PSU), D.N.\nBurrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester), P.A.\nEvans (U. Leicester) and A.Y. Lien report on behalf of the Swift-XRT\nteam:\n\nWe have analysed 6.8 ks of XRT data for GRB 210207B (Lien et al. GCN\nCirc. 29420), from 80 s to 45.6 ks after the  BAT trigger. The data\ncomprise 329 s in Windowed Timing (WT) mode with the remainder in\nPhoton Counting (PC) mode. The enhanced XRT position for this burst was\ngiven by Beardmore et al. (GCN Circ. 29422).\n\nThe late-time light curve (from T0+3.9 ks) can be modelled with a\npower-law decay with a decay index of alpha=1.37 (+0.07, -0.06).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.99 (+/-0.04). The\nbest-fitting absorption column is  1.38 (+/-0.13) x 10^21 cm^-2, in\nexcess of the Galactic value of 3.5 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.78 (+0.11, -0.10)\nand a best-fitting absorption column of 7.2 (+2.9, -2.6) x 10^20 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     7.2 (+2.9, -2.6) x 10^20 cm^-2\nGalactic foreground: 3.5 x 10^20 cm^-2\nExcess significance: 2.3 sigma\nPhoton index:\t     1.78 (+0.11, -0.10)\n\nIf the light curve continues to decay with a power-law decay index of\n1.37, the count rate at T+24 hours will be 0.021 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.7 x\n10^-13 (8.7 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/01031297.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 29427,
  "createdOn": 1612791611000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 210207B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 210207B"
}