{
  "bibcode": "2025GCN.41300....1E",
  "circularId": 41300,
  "subject": "GRB 250808A: Swift-XRT candidate 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 250808A, collecting 1.7 ks of Photon Counting (PC) mode data between T0+3.7 ks\nand T0+5.6 ks after the trigger. A candidate counterpart has been found. The details\nof this source are:\n\n  Source 1 (SWIFT J041412.2-224923):\n  ==================================\n    RA (J2000.0):   63.5510  =\t04h 14m 12.24s\n    Dec (J2000.0):  -22.8231  =  -22d 49' 23.2\"\n    Error:\t    3.9 (arcsec, radius, 90% confidence).\n    Detect flag:    GOOD\n    Distance:\t    4.9 arcmin from the SVOM/ECLAIRs position.\n    Mean rate:\t    0.140 +/- 0.013 ct s^-1\n    Mean flux:\t    (4.58 +/- 0.43)e-12 erg cm^-2 s^-1\n    Peak rate:\t    0.204 +/- 0.046 ct s^-1\n    Peak flux:\t    (6.7 +/- 1.5)e-12 erg cm^-2 s^-1\n    ECF:\t    3.27e-11 erg cm^-2 ct^-1\n\t\t      assuming NH=1.35e+21 cm^-2, gamma=2.07\n\t\t      determined from a spectral fit.\n    XMM UL:\t    2.2e-12 erg cm^-2 s^-1, (0.3-10 keV)\n\t\t      so the source is 3.0-sigma above this 3-sigma upper limit.\n    The source may be fading, at the 2.1-sigma level.\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_FIELD00027.\n\nThis circular is an official product of the Swift-XRT team.\n\n\n",
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "GRB 250808A",
  "submittedHow": "email",
  "createdOn": 1754730538223
}