2021ApJ...908..178N

In this work, we report a radio galaxy with precessing jets, double-peaked emission lines and the presence of two compact radio components with a projected separation of ∼6 parsec in very long baseline interferometry (VLBI) observations. The emission-line peak separations could be suggesting the presence of a supermassive binary black hole (BBH) with a separation of 6.3 parsec, matching the VLBI results. The kinematic jet precession model applied to the jets of J1328+2752 indicates that if it is a BBH, the accretion disk of the primary black hole is not coplanar with the binary system orbit, making its jet precess under the effect of the torque produced by the secondary black hole. However, we find that the Bardeen-Petterson effect can also provide precession timescales compatible with the jet precession period inferred in this source. This source has previously been identified as a restarted double-double radio galaxy (DDRG). Our findings therefore have important ramifications for the nature of DDRGs in general.