# XMM-Newton slew-survey counterparts to the INTEGRAL sources IGR J18173-2509 and IGR J16426+6536

ATel #1397; * ***A. Ibarra (ESAC), E. Kuulkers (ESAC), R. Saxton (ESAC)**

on **26 Feb 2008; 16:09 UT**

*Credential Certification: Richard Saxton (richard.saxton@sciops.esa.int)*

Subjects: X-ray, Gamma Ray

We report the first X-ray identification of two INTEGRAL sources which were
reported in the 3rd INTEGRAL IBIS/ISGRI soft gamma-ray survey catalog
(Bird et al. 2007, ApJS, 170, 175, see also http://isdc.unige.ch/~rodrigue/html/igrsources.html ).
They were found through a cross-correlation of the 1st XMM-Newton slew survey catalogue (Saxton et al. 2008, A&A in press) and the INTEGRAL survey catalog.

**IGR J18173-2509**
Within the INTEGRAL uncertainty (2.2') we find the XMM-Newton slew source
XMMLS1 J181722.2-250838. This source was detected during two slews on
UT 2003, Sep 23 08:42 and 2004, Sep 25, 10:49, with a statistical
significance of 7-sigma and 5-sigma, respectively.
The XMM-Newton slew source coordinate are: RA, Dec (J2000.0) = 18h17m22s, -25d08'38" (with a 68% confidence error of 8"), i.e., about 1' from the INTEGRAL position.

The 0.2-12 keV EPIC-pn count rates were 1.19 Â± 0.32 and 0.86 Â± 0.33, respectively.
The corresponding fluxes are 3.8 Â± 1.0 and 2.7 Â± 1.0 x 10^{-12} erg/s/cm^{2} (assuming a spectral model of an absorbed power law with a photon index of 1.7 and an absorption column, N_{H} = 3x10^{20} atoms/cm^{2}).

The ROSAT source 1RXS J181723-250831 lies within 0.3' of the XMM-Newton slew source.
1RXS J181723-250831 had a count rate of 0.073+/-0.024 c/s (0.2-2.4 keV), corresponding to an X-ray flux of 2.25 Â± 0.75 x 10^{-12} erg/s/cm^{2} (0.2-12.0 keV), i.e., consistent with that seen for XMMLS1 J181722.2-250838. We suggest that these two sources are associated with each other.

**IGR J16426+6536**
Within the INTEGRAL uncertainty of 4.5' we find the 4-sigma significance
XMM-Newton slew source XMMLS1 J164303.7+653253 with coordinates RA, Dec (J2000.0) =
16h43m04s, +65d32'53" (with a 68% confidence error of 8"). This is 4.2' from the INTEGRAL position.
We estimate that the false detection probability of a random source
within a radius of 4.5' is about 0.5%.
The source was detected on UT 2003 Dec 19 00:37 with an EPIC-pn count rate of
0.36 Â± 0.19 c/s, corresponding to an X-ray flux of 1.1 Â± 0.6 x 10^{-12} erg/s/cm^{2} (0.2-12 keV).

We note that two ROSAT sources also fall within the INTEGRAL error circle,
i.e., 1RXS J164244.8+653628 and 1RXS J164207.3+65384. Based on the position
and uncertainties of the XMM-Newton slew source and the two ROSAT sources,
we do not regard these X-ray sources to be related to each other; we
suggest, however, that one of the three sources may be the INTEGRAL counterpart.

We encourage follow-up at X-ray and other wavelengths to confirm our identification,
and association with the INTEGRAL sources.