EDP Sciences
Free access
Volume 418, Number 3, May II 2004
Page(s) 907 - 911
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20035724

A&A 418, 907-911 (2004)
DOI: 10.1051/0004-6361:20035724

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

P. Grandi, L. Foschini, N. Masetti and E. Palazzi

Istituto di Astrofisica Spaziale e Fisica Cosmica (IASF) del CNR, Sezione di Bologna, via Gobetti 101, 40129 Bologna, Italy
(Received 21 November 2003 / Accepted 30 January 2004 )

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 spectrum is well represented by a power law ( $\Gamma=2.5$) plus a black body component ( kT = 117 eV) absorbed by Galactic $N{\rm _H}$. About  $80\%$ of the X-ray flux ( $F_{0.2-10~\rm keV} \sim
3$   $\times$ 10-13 erg cm -2 s -1) is emitted below 2 keV. The 0.2-2 keV flux 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 H $_\beta$ and the flux ratio [O III]/H $_\beta$ 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 ( $L_{\rm bol} \ge 3$  $\times$ 1045 erg s -1) implying, for accretion rates close to the Eddington limit, a black hole mass $M_{\rm BH} \ge 2$  $\times$ $10^{7}~M_{\odot}$.

Key words: galaxies: quasars: individual: 1WGA J2223.7-0206 -- X-rays: galaxies

Offprint request: P. Grandi, grandi@bo.iasf.cnr.it

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