Binary black holes in nuclei of extragalactic radio sources

Abstract

If we assume that nuclei of extragalactic radio sources contain binary black hole systems, the two black holes can eject VLBI components, in which case two families of different VLBI trajectories will be observed. Another important consequence of a binary black hole system is that the VLBI core is associated with one black hole, and if a VLBI component is ejected by the second black hole, one expects to be able to detect the offset of the origin of the VLBI component ejected by the black hole that is not associated with the VLBI core. The ejection of VLBI components is perturbed by the precession of the accretion disk and the motion of the black holes around the center of gravity of the binary black hole system. We modeled the ejection of the component taking into account the two pertubations and present a method to fit the coordinates of a VLBI component and to deduce the characteristics of the binary black hole system. Specifically, this is the ratio T p /T b where T p is the precession period of the accretion disk and T b is the orbital period of the binary black hole system, the mass ratio M 1 /M 2 , and the radius of the binary black hole system R bin . From the variations of the coordinates as a function of time of the ejected VLBI component, we estimated the inclination angle i o and the bulk Lorentz factor γ of the modeled component. We applied the method to component S1 of 1823+568 and to component C5 of 3C 279, which presents a large offset of the space origin from the VLBI core. We found that 1823+568 contains a binary black hole system whose size is R bin ≈ 60 µas (µas is a microarcsecond) and 3C 279 contains a binary black hole system whose size is R bin ≈ 420 µas. We calculated the separation of the two black holes and the coordinates of the second black hole from the VLBI core. This information will be important to link the radio reference-frame system obtained from VLBI observations and the optical reference-frame system obtained from Gaia.

Jet Precession Driven by a Supermassive Black Hole Binary System in the BL Lac Object PG 1553+113

“…2000; Romero et al 2000;Caproni & Abraham 2004a,b;Caproni et al 2006Caproni et al , 2013Roland et al 2013). The parsec-scale jet of PG 1553+113 is assumed to be associated with the primary SMBH.…”

Possible evidence of a supermassive black hole binary with two radio jets in blazar 3C279

“…Roland et al (2013) attempted to explain the different trajectories followed by the knot C5 and knot C10 in terms of a binary black hole system.…”

Structure of the nucleus of 1928+738

“…It has been suggested by Lister & Homan (2005) that the lowest values for the error bars should be ≈beam/5, but Roland et al (2013) showed that the correct lowest values for the error bars adopted at 15 GHz are given by beam/15 ≤ ∆ min ≤ beam/12.…”

“…The possible free parameters of the model (for more details see Roland et al 2013) are -i o the inclination angle; -φ o the phase of the precession at t = 0; -∆Ξ the rotation angle in the plane perpendicular to the line of sight, also the asymptotic direction of the jet; -Ω the opening angle of the precession cone; -R o the maximum amplitude of the perturbation; -T p the precession period of the accretion disk; -T d the characteristic time for the damping of the beam perturbation, -M 1 the mass of the black hole ejecting the radio jet; -M 2 the mass of the secondary black hole; -γ c the bulk Lorentz factor of the VLBI component; -ψ o the phase of the BBH system at t = 0; -T b the period of the BBH system; -t o the time of the origin of the ejection of the VLBI component; -V a the propagation speed of the perturbations; -n rad is the number of steps to describe the extension of the VLBI component along the beam; -∆W and ∆N the possible offsets of the origin of the VLBI component.…”