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GCN Circular 41697

Subject
EP#01709201209: Swift-XRT observations
Date
2025-09-04T13:30:47Z (4 days ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
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 EP#01709201209, collecting 1.4 ks of Photon Counting (PC) mode data between
T0+4.0 ks and T0+15 ks after the trigger. We have detected 1 source inside the
EP/WXT error region. This source coincides with the known source 
1RXS J020013.6-084106 and the burst is likely a stellar flare from this object, as
reported also in GCN 41690Loading...
 
 .

Known X-ray sources
-------------------

  Source 1 (SWIFT J020012.7-084052):
  ==================================
    RA (J2000.0):   30.0530  =	02 00 12.72
    Dec (J2000.0):  -8.6811  =	-08 40 52.0
    Error:	    3.5 (arcsec, radius, 90% confidence).
    Detect flag:    GOOD
    Distance:	    52 arcsec from the Einstein Probe/WXT position.
    Mean rate:	    1.949 +/- 0.079 ct s^-1
    Mean flux:	    (6.57 +/- 0.27)e-11 erg cm^-2 s^-1
    Peak rate:	    5.8 +/- 1.3 ct s^-1
    Peak flux:	    (1.95 +/- 0.44)e-10 erg cm^-2 s^-1
    ECF:	    3.37e-11 erg cm^-2 ct^-1
		      assuming NH=1.53e+21 cm^-2, gamma=2.08
		      determined from a spectral fit.
    This matches a catalogued X-ray source CXO J020012.8-084051
    in the Chandra/2CSC catalogue. Details:
    Separation:     1.1" from the XRT source
    Cat Rate:	    0.0e+00 +/- 0.0e+00 ct s^-1 
    Cat Flux:	    0.0e+00 +/- 0.0e+00 erg cm^-2 s^-1 (0.3-10 keV)
		      so the source is not above the catalogued flux.
    The source IS FADING at the 4.1-sigma level.
    A SIMBAD object `1RXS J020013.6-084106' is 0.7" away.
    There is 1 2MASS object within the source's 3-sigma error radius.

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_FIELD00069.

This circular is an official product of the Swift-XRT team.