The AGN nature of three INTEGRAL sources: IGR J18249–3243, IGR J19443+2117, and IGR J22292+6647^*

¹ INAF/IASF Bologna, via Piero Gobetti 101, 40129 Bologna, Italy e-mail: landi@iasfbo.inaf.it
² Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802, USA
³ INAF/IASF Roma, via Fosso del Cavaliere 100, 00133 Roma, Italy
⁴ School of Physics and Astronomy, University of Southampton, Highfield, SO17 1BJ, UK
⁵ NASA Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received: 2 July 2008
Accepted: 14 November 2008

Abstract

Context. The third INTEGRAL/IBIS survey has revealed several new hard X-ray sources, which are still unidentified or unclassified. To identify these sources, we need to find their counterparts at other wavelengths and then study their nature.

Aims. The aim of this work is to employ the capability of the X-ray telescope (XRT) onboard Swift to localise the sources with a positional accuracy of few arcseconds, thus allowing the search for optical/UV, infrared, and radio counterparts to be more efficient and reliable. A second objective is to provide spectral information over a broad range of frequencies.

Methods. We analysed all XRT observations available for three unidentified INTEGRAL sources, IGR J18249–3243, IGR J19443+2117, and IGR J22292+6647, localised their soft X-ray counterparts, and searched for associations with objects in the radio band. We also combined X-/gamma-ray data, as well as all the available radio, infrared, and optical/UV information, in order to provide a broad-band spectral characterisation of each source and investigate its nature.

Results. In all three cases, XRT observations provided a firm localisation of the X-ray counterpart and information on its optical/UV, infrared, and radio associations. All three sources are found to be bright and repeatedly observed radio objects, although poorly studied. The X-/gamma-ray spectrum of each source is described well by power laws with the photon indices typical of AGN; however, only IGR J19443+2117 may have absorption in excess of the Galactic value, while IGR J22292+6647 is certainly variable at X-ray energies. IGR J18249–3243 has a complex radio morphology and a steep radio spectrum, while the other two sources show flatter radio spectra and a more compact morphology. Overall, their radio, optical/UV, and infrared characteristics, as well as their X-/gamma-ray properties, point to an AGN classification for all three objects.