Abstract
Abstract
It has been observed that many relativistic jets display a kind of cork-screw-like
precession. Numerical simulations has suggested that such kind of precession may originate from
the precession of the disk. In this work, we introduce an analytical model to describe the
precession and split of a tilted, geometrically thin disk. We consider the Lense-Thirring effect
from the central (primary) black hole (BH) and the gravitational effect from the companion
(secondary) BH far away from the center, both of which could induce the precession of the
accretion disk around the spin axis of central black hole. We propose the splitting conditions
that when the rate of viscous diffusion cannot catch up with the dynamical frequency at a certain
layer of fluid, the disk would split into two parts which precess independently. We presume that
the precessions of the inner and outer disks are in accord with the rotation and precession of
jet, respectively. By matching the frequencies of the disks to the observed frequencies of jet in
the cork-screw-like precession and considering the splitting condition, we are allowed to read
four parameters, the innermost radius (r
in), the outermost radius (r
out) of the
disk, the initial splitting radius (r
sp,0), and the inflow speed magnitude (β), of
the disk. We apply this model to OJ 287. Moreover, considering the inward shrinking of the disks,
we find the time variation of the precession angle of jet. This time variation presents a unique
feature of our model, which could be distinguishable in the future observation.