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IGR J18027-1455 / USNO-B1.0 0750-0506536 is an AGN

ATel #310; N. Masetti, E. Palazzi, L. Bassani, A. Malizia, J. B. Stephen (IASF/CNR-INAF Bologna Italy)
on 20 Jul 2004; 12:30 UT
Credential Certification: Malizia Angela (malizia@bo.iasf.cnr.it)

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

It has recently been suggested that the radio/near-infrared/optical and soft X-ray sources NVSS J180247-145451, 2MASXi J1802473-145454, USNO-B1.0 0750-0506536 and 1RXS J180245.5-145432 are in fact the same object and this is also considered as the most likely counterpart of the new INTEGRAL/IBIS source IGR J18027-1455 (ATel #229, #246). In order to identify the high energy object and to establish its relation to the other sources, a 20-minute spectrum of USNO-B1.0 0750-0506536 was acquired on July 15, 2004 with BFOSC at the `G.D. Cassini' 1.5m telescope located in Loiano (Italy) under a seeing of 1.5 arcsec. The resulting spectrum, covering the 4000-8500 Angstroms range, is dominated by a strong redshifted line complex corresponding to Halpha and [NII] and shows other emission lines typical of an AGN, likely a type 1 Seyfert. The redshift is estimated to be z=0.036, corresponding to a source distance of 144 Mpc (Ho=75 Km/sec/Mpc). At this distance, the source X-ray luminosity is 2.3 x 10^42 erg/sec and 1 x 10^44 erg/sec in the 0.1-2.4 keV and 20-40 keV band respectively, locating IGR J18027-1255 among the brightest Seyferts detected so far. The absolute B magnitude of the object is about -22. The extragalactic nature is compatible with the extension seen both in the IR and optical wavebands and is likely due to the galaxy surrounding the AGN.