{
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "circularId": 42232,
  "bibcode": "2025GCN.42232....1E",
  "createdOn": 1760394219812,
  "subject": "GRB 251013C: Swift-XRT counterpart detection",
  "body": "P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi  (INAF-IASFPA) , A.P.\nBeardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N.\nBurrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA),\nP. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro\n(INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U.\nLeicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato\n(INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the\nSwift-XRT team:\n\nSwift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source\nGRB 251013C (Rakotondrainibe et al., GCN 42222), collecting 1.8 ks of Photon\nCounting (PC) mode data between T0+344 s and T0+5.5 ks after the trigger. A bright,\nfading counterpart has been found, coincident with the VT optical, fading source\nreported by Palmerio et al. (GCN 42223), which has a redshift of 0.572\n(Martin-Carrillo et al., GCN 42227). Thus, we can conclude that this is the XRT\ncounterpart of GRB 251013C. The details of this source are:\n\n  Source 1 (SWIFT J230320.5-001235):\n  ==================================\n    RA (J2000.0):   345.8358  =  23 03 20.59\n    Dec (J2000.0):  -0.2100  =\t-00 12 36.0\n    Error:\t    3.5 (arcsec, radius, 90% confidence).\n    Detect flag:    GOOD\n    Distance:\t    3.6 arcmin from the SVOM/ECLAIRs position.\n    Mean rate:\t    2.356 +/- 0.081 ct s^-1\n    Mean flux:\t    (8.71 +/- 0.30)e-11 erg cm^-2 s^-1\n    Peak rate:\t    10.2 +/- 1.9 ct s^-1\n    Peak flux:\t    (3.76 +/- 0.69)e-10 erg cm^-2 s^-1\n    ECF:\t    3.70e-11 erg cm^-2 ct^-1\n\t\t      assuming NH=6.48e+20 cm^-2, gamma=1.78\n\t\t      determined from a spectral fit.\n    XMM UL:\t    6.3e-13 erg cm^-2 s^-1, (0.3-10 keV)\n\t\t      so the source is 5.4-sigma above this 3-sigma upper limit.\n\n\nAll fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with\ncatalogues and upper limits  from other missions, we assumed a power-law spectrum\nwith NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.\n\nThe results of the XRT-team automatic analysis of the XRT observations, including a\nposition-specific upper limit calculator, are available at\nhttps://www.swift.ac.uk/SVOM/SVOM_FIELD00041.\n\nThis circular is an official product of the Swift-XRT team.\n\n\n",
  "eventId": "GRB 251013C",
  "submittedHow": "email"
}