{
  "subject": "EP#01709177494: Swift-XRT counterpart detection of known source",
  "createdOn": 1748713654858,
  "submittedHow": "email",
  "bibcode": "2025GCN.40592....1E",
  "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-IASFPA), A. D'Ai\n(INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara\n(PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester),\nK.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T.\nSbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf\nof the Swift-XRT team:\n\nSwift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected\nsource EP#01709177494, collecting 2.0 ks of Photon Counting (PC) mode data between\nT0+388 s and T0+6.2 ks after the trigger. A candidate counterpart has been found.\nThe details of this source are:\n\n  Source 1 (SWIFT J170930.3-263917):\n  ==================================\n    RA (J2000.0):  257.3766  =\t17h 09m 30.38s\n    Dec (J2000.0): -26.6548  =\t-26d 39' 17.3\"\n    Error:\t   3.5 (arcsec, radius, 90% confidence).\n    Detect flag:   GOOD\n    Distance:\t   20 arcsec from the Einstein Probe/WXT position.\n    Mean rate:\t   11.35 +/- 0.22 ct s^-1\n    Mean flux:\t   (4.665 +/- 0.088)e-10 erg cm^-2 s^-1\n    Peak rate:\t   18.7 +/- 3.1 ct s^-1\n    Peak flux:\t   (7.7 +/- 1.3)e-10 erg cm^-2 s^-1\n    ECF:\t   4.11e-11 erg cm^-2 ct^-1, assuming NH=4.40e+21 cm^-2,\n\t\t   gamma=1.98; determined from a spectral fit.\n    This matches a catalogued X-ray source LSXPS J170930.1-263918\n    in the LSXPS catalogue. Details:\n      Separation:  3.2\" from the XRT source\n      Cat Rate:    1.2e+00 +/- 9.0e-03 ct s^-1 \n      Cat Flux:    4.7e-11 +/- 3.7e-13 erg cm^-2 s^-1 (0.3-10 keV)\n\t     so the source  is 5.7-sigma above the catalogued flux.\n    There is no evidence for fading.\n    A SIMBAD object `RX J1709.5-2639' is 8.3\" away.\n    There is 1 2MASS object within the source's 3-sigma error radius.\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/EP.\n\nThis circular is an officicial product of the Swift-XRT team.\n\n\n",
  "circularId": 40592,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>"
}