{
  "circularId": 42284,
  "eventId": "GRB 251014D",
  "subject": "GRB 251014D: Swift-XRT afterglow detection",
  "createdOn": 1760523616642,
  "body": "K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), S. Campana\n(INAF-OAB), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), S. Dichiara\n(PSU), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans (U.\nLeicester) reports on behalf of the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of GRB 251014D. We\nsearched for X-ray sources in  2.9 ks of Photon Counting (PC) mode\ndata. The total exposure at the position of the afterglow (see below)\nis 5.0 ks, obtained between T0+159.4 s and T0+22.3 ks.\n\nAn uncatalogued X-ray source is detected within the estimated 3-sigma\nSwift-BAT error region (296 arcsec) and is fading with >3-sigma\nsignificance, and is therefore likely the GRB afterglow. Using 1351 s\nof PC mode data and 3 UVOT images, we find an enhanced XRT position\n(using the XRT-UVOT alignment and matching UVOT field sources to the\nUSNO-B1 catalogue): \nRA, Dec = 323.92080, -41.85533 which is equivalent to:\n\nRA (J2000): 21h 35m 40.99s\nDec(J2000): -41d 51' 19.2\"\n\nwith an uncertainty of 3.4 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.71 (+0.12, -0.11).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\t of 1.64 (+/-0.06). The\nbest-fitting absorption column is  9.7 (+1.9, -1.8) x 10^20 cm^-2, in\nexcess of the Galactic value of 2.1 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 4.1 x 10^-11 (4.6 x 10^-11) erg\ncm^-2 count^-1. \n\nA summary of the WT-mode spectrum is thus:\nTotal column:\t     9.7 (+1.9, -1.8) x 10^20 cm^-2\nGalactic foreground: 2.1 x 10^20 cm^-2\nExcess significance: 6.8 sigma\nPhoton index:\t     1.64 (+/-0.06)\n\n\nThe results of the XRT-team automatic analysis are available at\nhttps://www.swift.ac.uk/xrt_products/01404126.\nThe results of the full analysis of the XRT observations are available\nat https://www.swift.ac.uk/ToO_GRBs/01404126.\n\nThis circular is an official product of the Swift-XRT team.\n\n",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "bibcode": "2025GCN.42284....1P",
  "submittedHow": "email"
}