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GCN Circular 40711

Subject
sb25061207: Swift-XRT observations
Date
2025-06-12T21:12:28Z (20 hours 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 SVOM/ECLAIRs-detected source
sb25061207, collecting 2.6 ks of Photon Counting (PC) mode data between T0+8.8 ks
and T0+20 ks after the trigger. We have detected 4 sources. These have been
automatically classified as follows:
  * 0 likely counterparts
  * 0 candidate counterparts
  * 4 uncatalogued X-ray sources
  * 0 known X-ray sources

Uncatalogued X-ray sources
--------------------------

  Source 1 (SWIFT J131222.8+000431):
  ==================================
    RA (J2000.0):  198.0954  =	13h 12m 22.90s
    Dec (J2000.0): +0.0753  =  +00d 04' 31.1"
    Error:	   6.4 (arcsec, radius, 90% confidence).
    Detect flag:   GOOD
    Distance:	   7.2 arcmin from the SVOM/ECLAIRs position; 
	 4.6 arcsec from SVOM/VT counterpart (GCN 40707Loading...
 
 ).
    Mean rate:	   0.0133 [+0.0031, -0.0028] ct s^-1
    Mean flux:	   (6.0 [+1.4, -1.3])e-13 erg cm^-2 s^-1
    Peak rate:	   0.0147 +/- 0.0037 ct s^-1
    Peak flux:	   (6.6 +/- 1.7)e-13 erg cm^-2 s^-1
    ECF:	   4.50e-11 erg cm^-2 ct^-1, assuming NH=2.24e+20 cm^-2,
		   gamma=1.42; determined from a spectral fit.
    XMM UL:	   2.7e-12 erg cm^-2 s^-1, (0.3-10 keV)
	 so the source is 12.4-sigma above this 3-sigma upper limit.
    The source may be fading, at the 0.6-sigma level.

  Source 2 (SWIFT J131136.2+000123):
  ==================================
    RA (J2000.0):  197.9010  =	13h 11m 36.24s
    Dec (J2000.0): +0.0233  =  +00d 01' 23.9"
    Error:	   5.9 (arcsec, radius, 90% confidence).
    Detect flag:   GOOD
    Distance:	   5.2 arcmin from the SVOM/ECLAIRs position.
    Mean rate:	   (7.2 +/- 2.1)e-3 ct s^-1
    Mean flux:	   (7.4 +/- 2.1)e-13 erg cm^-2 s^-1
    Peak rate:	   (7.2 +/- 2.1)e-3 ct s^-1
    Peak flux:	   (7.4 +/- 2.1)e-13 erg cm^-2 s^-1
    ECF:	   1.03e-10 erg cm^-2 ct^-1, assuming NH=2.41e+21 cm^-2,
		   gamma=0.47; determined from a spectral fit.
    XMM UL:	   4.4e-12 erg cm^-2 s^-1, (0.3-10 keV)
	 so the source is 17.2-sigma above this 3-sigma upper limit.
    There is no evidence for fading.
    A SIMBAD object `MGC 42939' is 5.7" away.

  Source 3 (SWIFT J131139.2-000814):
  ==================================
    RA (J2000.0):  197.9134  =	13h 11m 39.22s
    Dec (J2000.0): -0.1375  =  -00d 08' 15.0"
    Error:	   7.3 (arcsec, radius, 90% confidence).
    Detect flag:   GOOD
    Distance:	   10.5 arcmin from the SVOM/ECLAIRs position.
    Mean rate:	   (6.3 [+2.4, -1.9])e-3 ct s^-1
    Mean flux:	   (1.36 [+0.52, -0.42])e-18 erg cm^-2 s^-1
    Peak rate:	   (6.3 [+2.4, -1.9])e-3 ct s^-1
    Peak flux:	   (1.36 [+0.52, -0.42])e-18 erg cm^-2 s^-1
    ECF:	   2.14e-16 erg cm^-2 ct^-1, assuming NH=4.37e+21 cm^-2,
		   gamma=96.83; determined from a spectral fit.
    XMM UL:	   2.7e-12 erg cm^-2 s^-1, (0.3-10 keV)
	 so the source is 5817530.8-sigma above this 3-sigma upper limit.
    There is no evidence for fading.

  Source 4 (SWIFT J131140.3-000120):
  ==================================
    RA (J2000.0):  197.9181  =	13h 11m 40.34s
    Dec (J2000.0): -0.0225  =  -00d 01' 21.0"
    Error:	   6.1 (arcsec, radius, 90% confidence).
    Detect flag:   REASONABLE
    Distance:	   4.9 arcmin from the SVOM/ECLAIRs position.
    Mean rate:	   (2.6 [+1.5, -1.2])e-3 ct s^-1
    Mean flux:	   (1.61 [+0.96, -0.73])e-13 erg cm^-2 s^-1
    Peak rate:	   (2.6 [+1.5, -1.2])e-3 ct s^-1
    Peak flux:	   (1.61 [+0.96, -0.73])e-13 erg cm^-2 s^-1
    ECF:	   6.23e-11 erg cm^-2 ct^-1, assuming NH=3.65e+22 cm^-2,
		   gamma=2.45; determined from a spectral fit.
    XMM UL:	   4.8e-12 erg cm^-2 s^-1, (0.3-10 keV)
	 so the source is 55.2-sigma 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/SVOM.

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