2020ApJ...897...47C

We present a study of the central engine in the broad-line radio galaxy 3C 109. To investigate the immediate surrounding of this accreting, supermassive black hole, we perform a multiepoch broadband spectral analysis of a joint NuSTAR/XMM observation (2017), an archival XMM observation (2005) and the 105 month averaged Swift-BAT data. We are able to clearly separate the spectrum into a primary continuum, neutral and ionized absorption, and a reflection component. The photon index of the primary continuum has changed since 2005 (Γ=1.61_–0.01^+0.02→1.54±0.02), while other components remain unchanged, indicative of minimal geometric changes to the central engine. We constrain the high-energy cutoff of 3C 109 (E_cut=49_–5⁺⁷ keV ) for the first time. The reflector is found to be ionized (log ξ = 2.3_–0.2^+0.1) but no relativistic blurring is required by the data. Spectral energy distribution (SED) analysis confirms the super-Eddington nature of 3C 109 initially (λ_Edd > 2.09). However, we do not find any evidence for strong reflection (R = 0.18_–0.03^+0.04) or a steep power-law index, as expected from a super-Eddington source. This puts the existing virial mass estimate of 2 x10⁸M_☉ into question. We explore additional ways of estimating the Eddington ratio, some of which we find to be inconsistent with our initial SED estimate. We obtain a new black hole mass estimate of 9.3 x10⁸M_☉, which brings all Eddington ratio estimates into agreement and does not require 3C 109 to be super-Eddington.