2024ApJ...972...34L

Based on the magnetization, an accretion disk with a large-scale magnetic field can be separated into either standard and normal evolution or magnetically arrested disk (MAD), which are difficult to identify from observations. It is still unclear whether all the radio-loud active galactic nuclei (RLAGNs) with a thin disk and strong radio emissions contain a MAD. We investigate this issue by utilizing the 3CRR catalog. We compile a sample of 35 quasars and 14 high-excitation radio galaxies powered by a thin accretion disk. In order to consistently compare with the MAD sample given by Li et al., the optical-UV emissions of our sample are all detected by the Hubble Space Telescope. It is found that the average X-ray luminosity (L_X) of our sample is about 5.0 times higher than that of radio-quiet active galactic nuclei with matching optical-UV luminosity (L_UV), in general accord with the factor of 4.5 times in MAD sample within the uncertainty. The relationship between radio (5 GHz) and X-ray (2 keV) luminosities in the 3CRR sources is also found to be consistent with the MAD sample. Furthermore, the jet efficiencies of 3CRR sources are consistent with those from the GRMHD simulations of MAD. Therefore, we suggest that probably all the quasars and at least a fraction of high-excitation radio galaxies in the 3CRR catalog, and perhaps all the RLAGNs with strong radio emissions contain a MAD.