Evidence of an Untruncated Accretion Disk in the Broad-Line Radio Galaxy 4C 74.26

Abstract

We present evidence of a broad ionized Fe Kα line in the XMM-Newton spectrum of the broad-line radio galaxy (BLRG) 4C 74.26. This is the first indication that the innermost regions of the accretion flow in BLRGs contain thin, radiatively efficient disks. Analysis of the 35 ks XMM-Newton observation finds a broad line with an inner radius close to the innermost stable circular orbit for a maximally spinning black hole. The outer radius of the relativistic line is also found to be within 10 gravitational radii. The Fe Kα line profile gives an inclination angle of ~40°, consistent with the radio limit. There are two narrow components to the Fe Kα complex: one at 6.4 keV from neutral Fe and one at 6.2 keV. These may form the blue and red horns of a diskline from farther out on the disk, but a longer observation is required to confirm this hypothesis. We discuss the implications of this observation for models of jet production and suggest that BLRGs and radio-loud quasars will have larger-than-average black hole masses, thus resulting in thicker accretion flows close to the black hole.