The broad-band X-ray spectrum of the Seyfert 1 galaxy, MCG+8-11-11

TL;DR

This study presents a broad-band X-ray analysis of Seyfert 1 galaxy MCG+8-11-11, revealing that all reprocessing components are linked to the accretion disc with no evidence of a classical torus, challenging traditional AGN models.

Contribution

First comprehensive broadband X-ray spectral analysis of MCG+8-11-11 showing reprocessing components originate from the accretion disc, not a torus, with implications for AGN structure models.

Findings

Relativistic iron line detected when including high-energy data.

Reflection component linked to the accretion disc, not a torus.

No evidence for a classical pc-scale torus in MCG+8-11-11.

Abstract

We present a long (100 ks) Suzaku observation of one of the X-ray brightest AGN, MCG+8-11-11. These data were complemented with the 54-month Swift BAT spectrum, allowing us to perform a broad-band fit in the 0.6-150 keV range. The fits performed in the 0.6-10 keV band give consistent results with respect to a previous XMM-Newton observation, i.e. the lack of a soft excess, warm absorption along the line of sight, a large Compton reflection component (R~1) and the absence of a relativistic component of the neutral iron K$\alpha$ emission line. However, when the PIN and Swift BAT data are included, the reflection amount drops significantly (R~0.2-0.3), and a relativistic iron line is required, the latter confirmed by a phenomenological analysis in a restricted energy band (3-10 keV). When a self-consistent model is applied to the whole broadband data, the observed reflection component appears to be all associated to the relativistic component of the iron K$\alpha$ line. The resulting scenario, though strongly model-dependent, requires that all the reprocessing spectral components from Compton-thick material must be associated to the accretion disc, and no evidence for the classical pc-scale torus is found. The narrow core of the neutral iron K$\alpha$ line is therefore produced in a Compton-thin material, like the BLR, similarly to what found in another Seyfert galaxy, NGC7213, but with the notable difference that MCG+8-11-11 presents spectral signatures from an accretion disc. The very low accretion rate of NGC7213 could explain the lack of relativistic signatures in its spectrum, but the absence of the torus in both sources is more difficult to explain, since their luminosities are comparable, and their accretion rates are completely different.