XMM-Newton observations of an absorbed z= 0.67 QSO: no dusty torus?

Abstract

We present XMM-Newton observations of AX J0341.4-4453, a mildly reddened A_V < 7 quasi-stellar object (QSO) at a redshift of z= 0.672. The XMM-Newton spectrum shows a large obscuring column N_H~ 10²³ cm^-2 corresponding to A_V~ 70, in agreement with previous results based on the lower limit of the ASCA hardness ratio. The X-ray spectrum is represented by a `scattering' model with Γ~ 2.0 and where the scattered power-law normalization is a few per cent of the hard component. No FeK line is detected with a 90 per cent upper limit on its equivalent width of ~360 eV. The large discrepancy between the column density observed in X-rays and that inferred from the Balmer decrement can be explained by dust sublimation near the nucleus. Then, the X-ray and the optical obscuration come from two different regions: the X-ray close to the accretion disc, the optical at much larger > 0.25 pc scales.