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Swift XRT detection of the Integral ISGRI source IGR J2018+4043.

ATel #788; J. Kennea, G. G. Pavlov (PSU), A. M. Bykov, A. M. Krassilchtchikov, Yu. A. Uvarov (Ioffe Inst.), F. Lebrun (CEA-Saclay), H. Bloemen, W. Hermsen, J. Kaastra (SRON)
on 3 Apr 2006; 20:41 UT
Credential Certification: Jamie A. Kennea (kennea@astro.psu.edu)

Subjects: Infra-Red, X-ray, Gamma Ray

Referred to by ATel #: 1497, 1498, 1584, 1595, 1597

We observed the field around the hard X-ray source IGR J2018+4043 (Bykov et al. 2004, A&A, 427, L21) with Swift (total exposure 5 ks) and detected a point-like source in the XRT image at R.A. = 20:18:38.5, decl. = +40:41:00.4 (uncertainty 4.2 arcsec radius at 90% confidence level), consistent with the ISGRI position and possibly with the position of the unidentified CGRO EGRET source 3EG J2020+4017. The observed 0.5-10 keV flux is 3(+/-1)e-12 erg/cm^2/s. A power-law fit of the spectrum gives a photon index Gamma = 0.7(+2.2,-0.2) and hydrogen column density NH = 4(+6/-3)e22 cm^{-2} (90% confidence errors). We found a likely NIR counterpart of the source in the 2MASS catalog centered at R.A. = 20:18:38.73, decl. = +40:41:00.1 (2.6 arcsec from the XRT position), with magnitudes J=14.9, H=12.7, Ks=12.1 (as the 2MASS source shows some evidence of extension, the quoted magnitudes may need to be corrected). The source could be an AGN or a Galactic X-ray binary. Deeper X-ray observations are needed to distinguish between these interpretations.