{
  "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 Einstein Probe/WXT-detected\nsource EP251124a, collecting 2.5 ks of Photon Counting (PC) mode data between T0+5.1\nks and T0+11 ks after the trigger. The field is full of extended emission due to a\ncluster of galaxies. We have detected 3 sources.  These have been automatically\nclassified as follows:\n  * 0 likely counterparts\n  * 0 candidate counterparts\n  * 3 uncatalogued X-ray sources\n  * 0 known X-ray sources\n\nUncatalogued X-ray sources\n--------------------------\n\n  Source 2 (SWIFT J025449.9+413724):\n  ==================================\n    RA (J2000.0):   43.7081  =\t02 54 49.94\n    Dec (J2000.0):  +41.6234  =  +41 37 24.2\n    Error:\t    5.4 (arcsec, radius, 90% confidence).\n    Detect flag:    GOOD\n    Distance:\t    3.0 arcmin from the Einstein Probe/WXT position.\n    Mean rate:\t    (-1.0 +/- -1.0)e0 ct s^-1\n    Mean flux:\t    (-2.1 +/- -2.1)e-11 erg cm^-2 s^-1\n    Peak rate:\t    (8.5 [+3.4, -3.0])e-3 ct s^-1\n    Peak flux:\t    (1.80 [+0.71, -0.63])e-13 erg cm^-2 s^-1\n    ECF:\t    2.12e-11 erg cm^-2 ct^-1\n\t\t      assuming NH=2.22e+22 cm^-2, gamma=5.93\n\t\t      determined from a spectral fit.\n    LSXPS UL:\t    1.0e-02 ct/sec, (0.3-10 keV)\n\t\t      so the source is not above this 3-sigma upper limit.\n    There is no evidence for fading.\n    A SIMBAD object `2MASX J02544959+4137278' is 5.1\" away.\n    There is 1 2MASS object within the source's 3-sigma error radius.\n\n  Source 3 (SWIFT J025510.5+413444):\n  ==================================\n    RA (J2000.0):   43.7940  =\t02 55 10.56\n    Dec (J2000.0):  +41.5789  =  +41 34 44.0\n    Error:\t    5.7 (arcsec, radius, 90% confidence).\n    Detect flag:    POOR\n    Distance:\t    2.8 arcmin from the Einstein Probe/WXT position.\n    Mean rate:\t    (-1.0 +/- -1.0)e0 ct s^-1\n    Mean flux:\t    (-1.6 +/- -1.6)e-10 erg cm^-2 s^-1\n    Peak rate:\t    (3.8 [+2.5, -2.2])e-3 ct s^-1\n    Peak flux:\t    (6.0 [+4.0, -3.4])e-13 erg cm^-2 s^-1\n    ECF:\t    1.57e-10 erg cm^-2 ct^-1\n\t\t      assuming NH=2.84e+21 cm^-2, gamma=0.31\n\t\t      determined from a spectral fit.\n    LSXPS UL:\t    1.6e-02 ct/sec, (0.3-10 keV)\n\t\t      so the source is not above this 3-sigma upper limit.\n    There is no evidence for fading.\n\n  Source 6 (SWIFT J025445.0+413429):\n  ==================================\n    RA (J2000.0):   43.6876  =\t02 54 45.02\n    Dec (J2000.0):  +41.5749  =  +41 34 29.6\n    Error:\t    5.4 (arcsec, radius, 90% confidence).\n    Detect flag:    POOR\n    Distance:\t    2.0 arcmin from the Einstein Probe/WXT position.\n    Mean rate:\t    0.0245 [+0.0084, -0.0071] ct s^-1\n    Mean flux:\t    (8.9 [+3.1, -2.6])e-13 erg cm^-2 s^-1\n    Peak rate:\t    0.043 [+0.022, -0.018] ct s^-1\n    Peak flux:\t    (1.56 [+0.81, -0.66])e-12 erg cm^-2 s^-1\n    ECF:\t    3.63e-11 erg cm^-2 ct^-1\n\t\t      assuming NH=1.20e+21 cm^-2, gamma=1.87\n\t\t      determined from a spectral fit.\n    LSXPS UL:\t    3.2e-02 ct/sec, (0.3-10 keV)\n\t\t      so the source is not above this 3-sigma upper limit.\n    There is no evidence for fading.\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/EP_FIELD00083.\n\nThis circular is an official product of the Swift-XRT team.\n\n\n",
  "subject": "EP251124a: Swift-XRT observations",
  "submittedHow": "email",
  "circularId": 42827,
  "createdOn": 1764005808511,
  "submitter": "Phil Evans at U of Leicester <pae9@star.le.ac.uk>",
  "eventId": "EP251124a",
  "bibcode": "2025GCN.42827....1E"
}