1WGA J2223.7-0206: A Narrow-Line Quasi-Stellar Object in the XMM-Newton field of view of 3C 445

We report the discovery of a Narrow Line QSO located at about 1.3 � from the Broad Line Radio Galaxy 3C 445. The source, 1WGA J2223.7-0206, although already revealed by ROSAT, has never been optically identified previously. An XMM-Newton observation of 3C 445 has allowed, for the first time, an accurate X-ray spectral study of 1WGA J2223.7-0206, revealing an ultra-soft spectrum and fast flux variations typical of Narrow Line AGN. The 0.2-10 keV spec- trum is well represented by a power law ( Γ= 2.5) plus a black body component (kT = 117 eV) absorbed by Galactic NH. About 80% of the X-ray flux (F0.2−10 keV ∼ 3 × 10 −13 erg cm −2 s −1 ) is emitted below 2 keV. The 0.2− 2k eV fl ux is observed to decrease by about a factor 1.6 in about 5000 s. The optical observations, triggered by the X-ray study, confirm the Narrow Line AGN nature of this source. The continuum is blue with typical AGN emission lines, pointing to a redshift z = 0.46. The full width half maximum of Hβ and the flux ratio (O )/Hβ are 2000 km s −1 and 0.21, respectively. The optical luminosity (MR = −23.2) and the point-like appearance in the optical images identify 1WGA J2223.7-0206 as a Narrow Line QSO. From the optical-UV-X-ray Spectral Energy Distribution we obtain a lower limit of the bolometric luminosity of 1WGA J2223.7-0206 (Lbol ≥ 3 × 10 45 erg s −1 ) implying, for accretion rates close to the Eddington limit, a black hole mass MBH ≥ 2 × 10 7 M� .