{
  "submittedHow": "email",
  "createdOn": 1745050160055,
  "circularId": 40173,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "subject": "GRB 250419A: Swift-XRT refined Analysis",
  "bibcode": "2025GCN.40173....1P",
  "eventId": "GRB 250419A",
  "body": "K.L. Page (U. Leicester), B. Sbarufatti (INAF-OAB), C. Salvaggio\n(INAF-OAB), M. Ferro (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU),\nD.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans (U.\nLeicester) reports on behalf of the Swift-XRT team:\n\nWe have analysed 2.0 ks of XRT data for the SVOM/ECLAIRs-detected burst\nGRB 250419A (SVOM burst-id sb25041901), from 3.8 ks to 9.6 ks after the\n SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC)\nmode.  The light curve is consistent with a constant source of mean\ncount rate 1.1e-01 ct/sec. A power-law fit gives an index of 0.3 (+0.6,\n-0.5). Despite a constant count rate, we are likely detecting the GRB\nafterglow. The source is consistent with the position of the optical\nafterglow detected by the SVOM/COLIBRÍ (FM-GFT) telescope (Lopez et\nal., GCN 40169), SVOM/VT (Xin et al., GCN 40170), KAIT (Zheng et al.,\nGCN 40171), GOTO (Kumar et al., GCN 40172).\n\nA spectrum formed from the PC mode data can be fitted with an absorbed\npower-law with a photon spectral index of 1.9 (+0.4, -0.3). The\nbest-fitting absorption column is  7.7 (+9.9, -5.5) x 10^20 cm^-2,\nconsistent with the Galactic value of 2.2 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 (4.1 x\n10^-11) erg cm^-2 count^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     7.7 (+9.9, -5.5) x 10^20 cm^-2\nGalactic foreground: 2.2 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.9 (+0.4, -0.3)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00019724.\n\nThis circular is an official product of the Swift-XRT team.\n\n"
}