Broadband X-Ray Constraints on the Accreting Black Hole in Quasar 4C 74.26

Abstract

X-ray data for quasar 4C 74.26 have previously been modeled with a broad Fe K α emission line and reflection continuum originating in the inner part of the accretion disk around the central supermassive black hole (SMBH), i.e., the strong-gravity regime. We modeled broadband X-ray spectra from Suzaku and NuSTAR with mytorus , self-consistently accounting for Fe K α line emission, as well as direct and reflected continuum emission, from matter with a finite column density. A narrow Fe K α emission line originating in an X-ray reprocessor with solar Fe abundance far from the central SMBH is sufficient to produce excellent fits for all spectra. For the first time, we are able to measure the global column density, out of the line of sight, to be in the range ∼1.5 to ∼ , i.e., in the Compton-thick regime, while the line-of-sight column density is Compton-thin in all observations. The Fe K α emission line is unresolved in all observations but one. The Compton-scattered continuum from distant matter removes the need for relativistic broadening of the Fe K α emission line, which is required for SMBH spin measurements. The resolved line observation can alternatively be modeled with a relativistic model but we do not find evidence for a truncated accretion disk model. We conclude that the X-ray emission in these 4C 74.26 data is unlikely to originate in the inner accretion disk region and thus cannot be used to measure SMBH spin.