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
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.
