On the Nature of the Hard X-Ray Source IGR J2018+4043

We found a very likely counterpart to the recently discovered hard X-ray source IGR J2018+4043 in the multiwavelength observations of the source field. The source, originally discovered in the 20-40 keV band, is now confidently detected also in the 40-80 keV band, with a flux of (1.4+/-0.4)×10^-11 ergs cm^-2 s^-1. A 5 ks Swift observation of the IGR J2018+4043 field revealed a hard pointlike source with an observed 0.5-10 keV flux of 3.4^+0.7_-0.8×10^-12 ergs cm^-2 s^-1 (90% confidence level) at α=20^h18^m38.55 s, δ=+40^deg41^'00.4" (with a 4.2" uncertainty). The combined Swift-INTEGRAL spectrum can be described by an absorbed power-law model with photon index Γ=1.3+/-0.2 and N_H=6.1^+3.2_-2.2×10²² cm^-2. In archival optical and infrared data we found a slightly extended and highly absorbed object at the Swift source position. There is also an extended VLA 1.4 GHz source peaked at a beamwidth distance from the optical and X-ray positions. The observed morphology and multiwavelength spectra of IGR J2018+4043 are consistent with those expected for an obscured accreting object, i.e., an AGN or a Galactic X-ray binary. The identification suggests possible connection of IGR J2018+4043 to the bright γ-ray source GEV J2020+4023 detected by COS B and CGRO EGRET.