{
  "bibcode": "2022GCN.32350....1O",
  "body": "J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore\n(U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi\t(INAF-IASFPA) ,\nM. Capalbi (INAF-IASFPA), B. Sbarufatti (PSU), D.N. Burrows (PSU), J.\nD. Gropp (PSU) and P.A. Evans (U. Leicester) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the\nSwift/BAT-GUANO-detected burst GRB 220708B, collecting 1.7 ks of Photon\nCounting (PC) mode data between T0+35.1 ks and T0+36.8 ks. \n\nAn uncatalogued X-ray source is detected and is above the RASS 3-sigma\nupper limit at this position, and is therefore likely the GRB\nafterglow.  The position of this source is RA, Dec=248.5790, +36.3478\nwhich is equivalent to:\n\nRA (J2000): 16:34:18.97\nDec(J2000): +36:20:52.0\n\nwith an uncertainty of 4.0 arcsec (radius, 90% confidence).  This\nposition is 3.6 arcmin from the Swift/BAT-GUANO position.  The light\ncurve is consistent with a constant source of mean count rate 6.5e-02\nct/sec. A power-law fit gives an index of 0.0 (+0.0, -3.3).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 2.3 (+0.6, -0.5). The\nbest-fitting absorption column is  3.2 (+2.2, -1.7) x 10^21 cm^-2, in\nexcess of the Galactic value of 1.4 x 10^20 cm^-2 (Willingale et al.\n2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion\nfactor deduced from this spectrum  is 3.2 x 10^-11 (5.7 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.2 (+2.2, -1.7) x 10^21 cm^-2\nGalactic foreground: 1.4 x 10^20 cm^-2\nExcess significance: 2.9 sigma\nPhoton index:\t     2.3 (+0.6, -0.5)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00021508.\nThe results of the full analysis of the XRT observations are available\nat https://www.swift.ac.uk/ToO_GRBs/00021508.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 32350,
  "createdOn": 1657290451000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 220708B: Swift-XRT afterglow detection",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 220708B"
}