H1320+551: a type 1.8/1.9 Seyfert galaxy with an unabsorbed X-ray spectrum

Abstract

We present new optical spectroscopic and XMM-Newton X-ray observations of the active galactic nucleus (AGN) H1320+551. The optical data (consistent with but of better quality than a previously published spectrum) show this source to be a type 1.8/1.9 Seyfert galaxy at z = 0.0653. The narrow-line region is significantly reddened, with a Balmer decrement Hα/Hβ ∼ 6, and the broad-line region, with a barely detectable Hβ broad component, shows a much pronounced Balmer decrement (Hα/Hβ > 27). In spite of this, the EPIC pn X-ray spectrum exhibits a power-law continuum with a soft excess that is well fitted by a blackbody, with no photoelectric absorption above the Galactic value. An Fe K emission line is also seen at a rest-frame energy ∼6.5 keV with an equivalent width of ∼400 eV, far too weak for the source to be Compton-thick. Reconciling the optical and X-ray data requires the narrow-line region to be internally reddened but with small covering factor over the nuclear emission, and the Balmer decrement of the broad-line region to be an intrinsic property rather than caused by reddening/absorption. The H1320+551 type 1.8/1.9 Seyfert galaxy is not consistent with being an obscured type 1 Seyfert nucleus, i.e. it does not match the basic AGN unified scheme hypothesis.