On the nature of the hard X-ray source IGR J2018+4043

Abstract

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 . A 5 ks 11 2 1 (1.4 0.4) # 10 ergs cm s Swift observation of the IGR J2018 4043 field revealed a hard pointlike source with an observed 0.5–10 keV flux of ergs cm2 s 1 (90% confidence level) at , (with a 4 .2 0.7 12 hms 3.40.8 # 10 a p 20 18 38.55 d p 4041 00 .4 uncertainty). The combined Swift-INTEGRAL spectrum can be described by an absorbed power-law model with photon index and cm2 . In archival optical and infrared data we found a slightly 3.2 22 G p 1.3 0.2 NH p 6.12.2 # 10 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 g-ray source GEV J2020 4023 detected by COS B and CGRO EGRET.