TITLE: GCN CIRCULAR NUMBER: 42827 SUBJECT: EP251124a: Swift-XRT observations DATE: 25/11/24 17:36:48 GMT FROM: Phil Evans at U of Leicester pae9@star.le.ac.uk
P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Einstein Probe/WXT-detected source EP251124a, collecting 2.5 ks of Photon Counting (PC) mode data between T0+5.1 ks and T0+11 ks after the trigger. The field is full of extended emission due to a cluster of galaxies. We have detected 3 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 3 uncatalogued X-ray sources * 0 known X-ray sources
Uncatalogued X-ray sources --------------------------
Source 2 (SWIFT J025449.9+413724): ================================== RA (J2000.0): 43.7081 = 02 54 49.94 Dec (J2000.0): +41.6234 = +41 37 24.2 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.0 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-2.1 +/- -2.1)e-11 erg cm^-2 s^-1 Peak rate: (8.5 [+3.4, -3.0])e-3 ct s^-1 Peak flux: (1.80 [+0.71, -0.63])e-13 erg cm^-2 s^-1 ECF: 2.12e-11 erg cm^-2 ct^-1 assuming NH=2.22e+22 cm^-2, gamma=5.93 determined from a spectral fit. LSXPS UL: 1.0e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `2MASX J02544959+4137278' is 5.1" away. There is 1 2MASS object within the source's 3-sigma error radius.
Source 3 (SWIFT J025510.5+413444): ================================== RA (J2000.0): 43.7940 = 02 55 10.56 Dec (J2000.0): +41.5789 = +41 34 44.0 Error: 5.7 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.8 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-1.6 +/- -1.6)e-10 erg cm^-2 s^-1 Peak rate: (3.8 [+2.5, -2.2])e-3 ct s^-1 Peak flux: (6.0 [+4.0, -3.4])e-13 erg cm^-2 s^-1 ECF: 1.57e-10 erg cm^-2 ct^-1 assuming NH=2.84e+21 cm^-2, gamma=0.31 determined from a spectral fit. LSXPS UL: 1.6e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading.
Source 6 (SWIFT J025445.0+413429): ================================== RA (J2000.0): 43.6876 = 02 54 45.02 Dec (J2000.0): +41.5749 = +41 34 29.6 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.0 arcmin from the Einstein Probe/WXT position. Mean rate: 0.0245 [+0.0084, -0.0071] ct s^-1 Mean flux: (8.9 [+3.1, -2.6])e-13 erg cm^-2 s^-1 Peak rate: 0.043 [+0.022, -0.018] ct s^-1 Peak flux: (1.56 [+0.81, -0.66])e-12 erg cm^-2 s^-1 ECF: 3.63e-11 erg cm^-2 ct^-1 assuming NH=1.20e+21 cm^-2, gamma=1.87 determined from a spectral fit. LSXPS UL: 3.2e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading.
All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.
The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/EP/EP_FIELD00083.
This circular is an official product of the Swift-XRT team.
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