SUZAKUOBSERVATION OF THE BRIGHTEST BROAD-LINE RADIO GALAXY 4C 50.55 (IGR J21247+5058)

Abstract

We report the results from a deep Suzaku observation of 4C 50.55 (IGR J21247+5058), the brightest broad-line radio galaxy in the hard X-ray (>10 keV) sky. The simultaneous broadband spectra over 1-60 keV can be represented by a cutoff power law with two layers of absorption and a significant reflection component from cold matter with a solid angle of Ω/2π ≈ 0.2. A rapid flux rise by ~20% over 2 × 10⁴ s is detected in the 2-10 keV band. The spectral energy distribution suggests that there is little contribution to the total X-ray emission from jets. Applying a thermal Comptonization model, we find that corona is optically thick (τ_e ≈ 3) and has a relatively low temperature (kT _e ≈ 30 keV). The narrow iron-K emission line is consistent with a picture where the standard disk is truncated and/or its inner part is covered by optically thick Comptonizing corona smearing out relativistic broad-line features. The inferred disk structure may be a common feature of accretion flows onto black holes that produce powerful jets.