Reprocessing and Variable Cold Absorption in the Broad-Line Radio Galaxy 3C390.3

TL;DR

This study reports the first detection of both a 6.4 keV iron line and a reflection hump in the broad-line radio galaxy 3C390.3, suggesting a complex structure of the X-ray emitting and absorbing regions.

Contribution

It provides new observational evidence of cold reflection features in 3C390.3 and discusses the implications for AGN models, including the origin of the X-ray continuum and absorber variability.

Findings

Detection of iron line and reflection hump in 3C390.3

X-ray continuum modeled by absorbed power law with reflection

Time-variable line-of-sight absorption unrelated to primary continuum

Abstract

A BeppoSAX observation of the BLRG 3C390.3 is reported. For the first time, both the 6.4 keV iron line and a strong reflection hump, produced by the illumination of the primary X-ray emission on cold matter, are detected in this source. The 0.1-100 keV continuum is modeled by an absorbed power law (\Gamma~ 1.8) reflected at high energies by material with a fairly large covering factor (\Omega/2\pi~1). The iron line is intrinsically narrow ($\sigma=73(+207,-73) eV) and has an equivalent width of ~140$ eV. We discuss the results in the context of current models for AGNs and suggest that the primary X-ray power law continuum is probably produced by a hot inner flow, while the reprocessed radiation comes from an outer cold thin disk, and/or from a thick torus at even larger radii. Further observations with BeppoSAX could distinguish between the latter two cases. Beamed radiation associated to the radio jet is unlikely to contribute significantly to the X-ray emission. Finally, an historical study of the column density NH, also reported here, shows that the absorption along the line of sight changes in time. The NH time variability, which is not correlated with that of the primary continuum, seems to imply variations of the geometry of the absorber rather than variations in the ionization state of the gas.