2006A&A...448..547M

We present new results from our optical spectrophotometric campaign ongoing at the Astronomical Observatory of Bologna in Loiano (Italy) on hard X-ray sources detected by INTEGRAL. We have observed spectroscopically the putative optical counterparts of four more INTEGRAL sources, IGR J12391-1610, IGR J18406-0539, 2E 1853.7+1534 and IGR J19473+4452. These data have allowed us to determine their nature, finding that IGR J12391-1610 (=LEDA 170194) and IGR J19473+4452 are Seyfert 2 galaxies at redshifts z=0.036 and z=0.053, respectively, IGR J18406-0539 (=SS 406) is a Be massive X-ray binary located at ∼1.1kpc from Earth, and 2E 1853.7+1534 is a type 1 Seyfert galaxy with z=0.084. Physical parameters for these objects are also evaluated by collecting and discussing the available multiwavelength information. The determination of the extragalactic nature of a substantial fraction of sources inside the INTEGRAL surveys underlines the importance of hard X-ray observations for the study of background Active Galactic Nuclei located beyond the ``Zone of Avoidance'' of the Galactic Plane.