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INTEGRAL source IGR J16562-3301 --- a new BL Lac object

ATEL # 1270; R. Burenin, M. Revnivtsev, A. Mescheryakov, I. Bikmaev, M. Pavlinsky, R. Sunyaev (IKI, Moscow, Russia; MPA, Garching, Germany; KSU, Kazan, Russia)
on 11 Nov 2007; 13:47 UT
Password Certification: Rodion Burenin (

Subjects: Radio, Infra-Red, Optical, X-ray, Gamma Ray, AGN, Black Holes, Quasars

The accurate position of the hard X-ray source IGR J16562-3301/SWIFT J1656.3-3302 (Okajima et al. 2006, ATel #799, Krivonos et al. 2007, astro-ph/0701836) was determined earlier by Tueller et al. (2006, ATEL #835) using SWIFT/XRT observation of this field. We found that more accurate position of this source can be derived from the same data when the systematics of SWIFT/XRT astrometry is corrected using the other two bright X-ray sources identified with relatively bright optical stars. From these data we found the following RA,Dec for IGR J16562-3301/SWIFT J1656.3-3302: 16:56:16.82 -33:02:12.5 (J2000), with ~1.5'' uncertainty, which now should be almost purely statistical (astrometry is based on UCAC2 catalog). Near this improved error circle we found a very bright (~0.4Jy at 1.4GHz) radio source NVSS J165616-330211. This field was also observed with Russian-Turkish 1.5-m telescope (RTT-150, Bakirlitepe, TUBITAK National Observatory, Turkey). The centroid of the only optical source consistent with both improved SWIFT/XRT position and NVSS J165616-330211 coordinates is at RA,Dec: 16:56:16.77 -33:02:12.8 (J2000), which is also coincide with IR source 2MASS 16561677-3302127. In the optical spectrum of this source we identified no obvious spectral lines. All these data strongly suggests that the hard X-ray source IGR J16562-3301/SWIFT J1656.3-3302 is a BL Lac object. In order to determine its redshift the optical spectrum with significantly higher signal to noise ratio is needed.

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