{
  "body": "P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A.\nWilliams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.\nLeicester), M.G. Bernardini (INAF-OAB), E. Ambrosi  (INAF-IASFPA)  and\nP.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:\n\nWe have analysed 5.0 ks of XRT data for GRB 250610B, from 2.9 ks to\n105.7 ks after the  SVOM/ECLAIRs trigger. The data are entirely in\nPhoton Counting (PC) mode. Using 2013 s of PC mode data and 2 UVOT\nimages, we find an enhanced XRT position (using the XRT-UVOT alignment\nand matching UVOT field sources to the USNO-B1 catalogue): RA, Dec =\n200.17991, +31.10477 which is equivalent to:\n\nRA (J2000): 13h 20m 43.18s\nDec(J2000): +31d 06' 17.2\"\n\nwith an uncertainty of 2.8 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=0.68 (+0.12, -0.10).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.86 (+0.33, -0.25). The\nbest-fitting absorption column is  3.1 (+7.7, -2.0) x 10^20 cm^-2,\nconsistent with the Galactic value of 1.1 x 10^20 cm^-2 (Willingale et\nal. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux\nconversion factor deduced from this spectrum  is 3.5 x 10^-11 (3.7 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     3.1 (+7.7, -2.0) x 10^20 cm^-2\nGalactic foreground: 1.1 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.86 (+0.33, -0.25)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00019863.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "subject": "GRB 250610B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "bibcode": "2025GCN.40705....1D",
  "createdOn": 1749741081101,
  "eventId": "GRB 250610B",
  "submittedHow": "email",
  "circularId": 40705
}