The analysis of 3C 47 has resolved a longstanding conundrum dating back to the 1990s: the CIVλ1549 broad- line profile in the UV spectra of radio galaxies often appeared as narrow as or narrower than the Hβ line. The interpretation provided by 3C 47, involving an accretion disk and a failed wind, offers an explanation. In many cases, the disk contribution could be completely masked. The “double-peakers,” which are most frequently found at the extremum of the Eddington ratio (minimum radiative output per unit mass) on the quasar main sequence, may all be due to the trimming of the emitting region by a second black hole. Accretion disk and wind emission in the Population B, jetted quasar 3C 47 Paola Marziani1, Shimeles Terefe Mengistue2,3,4, A. del Olmo5, M. Povic5,6, J. Perea5, and A. Deconto Machado5 1National Inst. for Astrophysics (INAF), Oss. Astron. di Padova, Padova, Italy; 2Space Science and Geospatial Inst. (SSGI), Addis Ababa, Ethiopia; 3Addis Ababa Univ., Addis Ababa, Ethiopia; 4Jimma Univ., Jimma, Ethiopia; 5IAA (CSIC), Granada Spain; 6Mbarara Univ. of Science and Technology (MUST), Mbarara, Uganda An optically thick, geometrically thin accretion disk around a supermassive black hole might contribute to broad line emission in type-1 active galactic nuclei (AGN). We show that the double-peaked profiles of the strongest low-ionization lines (LILs) in the 3C 47 optical spectrum can be explained by a relativistic Keplerian accretion disk model. The profiles of prototypical high ionization lines (HILs) such as CIVλ1549 were also modeled by the contribution of the accretion disk, but required an additional component, possibly due to a failed wind. The observations of 3C 47 suggest an intriguing hypothesis for the origin of the “double-peakers,” sources found at the low end of radiative power per unit black hole mass along the quasar main sequence. Intriguing profile variability Conclusion A binary black hole, after all? Relativistic accretion disk plus a failed wind? 𝛺 𝛺 30 kpc Orbital plane of the secondary Equatorial plane of the primary Reference 3C47 The double-peaked profile of Balmer lines is modeled using a relativistic AD emission profile, following the approach of Chen & Halpern (1989, ApJ, 344, 115), and using a fully Bayesian technique. The single-peaked CIVλ1549 profile can be attributed to the AD plus a strong central feature. The flat spectral energy distribution of 3C 47, dominated by synchrotron and synchrotron-self-Compton emission, results in the over-ionization of the gas. This over-ionization leads to a lower force multiplier, which may contribute to the formation of a failed wind. Force multiplier 3C 47 Typical AGN The available observations, though sparse, reveal intriguing variability patterns and changes in peak shift amplitude. The periods inferred from these shift variations suggest masses exceeding that of the primary black hole. The hypothesis that the double-peaked structure is due to two black holes, each with its own broad line region giving rise to an almost Gaussian component, is not favored. The VLA radio map (Fernini et al. 1991, ApJ, 381, 63) shows an intriguing misalignment between the hot spot and the lobe- counter-lobe axis. The geodetic precession period can be shorter than, or comparable to, the dynamical timescale of the radio source, if precession is induced by a second, smaller- mass black hole between the outer disk edge (r ~ 103 rg) and the torus inner edge(r ~ 104 rg), with an orbital plane inclined by 15o with respect to the equatorial plane of the primary. AD AD+failed wind Ionization structure MBH ~ 7 109 M⦿ tdyn ~ 6 107yr