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

A. M. Bykov·A. M. Krassilchtchikov·Yu. A. Uvarov·J. A. Kennea·G. G. Pavlov·G. M. Dubner·E. B. Giacani·H. Bloemen·W. Hermsen·J. Kaastra·F. Lebrun·M. Renaud·R. Terrier·M. DeBecker·G. Rauw·J. -P. Swings
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Abstract

We found a very likely counterpart to the recently discovered hard X-ray source IGR J2018+4043 in the multi-wavelength 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) x 10(-11) erg cm(-2) s(-1). A 5 ks Swift observation of the IGR J2018+4043 field revealed a hard point-like source with the observed 0.5-10 keV flux of 3.4(+0.7)(-0.8) x 10(-12) erg cm(-2) s(-1) (90% confidence level) at alpha = 20h18m38.55s, delta = +40d41m00.4s (with a 4.2" uncertainty). The combined Swift-INTEGRAL spectrum can be described by an absorbed power-law model with photon index gamma = 1.3 +/- 0.2 and N_H = 6.1(+3.2)(-2.2) x 10(22) 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 beam-width 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 gamma-ray source GEV J2020+4023 (3EG J2020+4017) detected by COS B and CGRO EGRET in the gamma-Cygni SNR field.

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A. M. Bykov, A. M. Krassilchtchikov, Yu. A. Uvarov, J. A. Kennea, G. G. Pavlov, G. M. Dubner, E. B. Giacani, H. Bloemen, W. Hermsen, J. Kaastra, F. Lebrun, M. Renaud, R. Terrier, M. DeBecker, G. Rauw, J. -P. Swings. 2006-09-25. On the nature of the hard X-ray source IGR J2018+4043. https://doi.org/10.1086/508327

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