Self-gravitating disks around rapidly spinning, tilted black holes: General-relativistic simulations

We perform general-relativistic simulations of self-gravitating black hole disks in which the spin of the black hole is significantly tilted (45° and 90°) with respect to the angular momentum of the disk and the disk-to-black hole mass ratio is 16-28%. The black holes are rapidly spinning with dimensionless spins up to ∼0.97. These are the first self-consistent hydrodynamic simulations of such systems, which can be prime sources for multimessenger astronomy. In particular tilted black-hole-disk systems lead to (i) black hole precession, (ii) disk precession and warping around the black hole, (iii) earlier saturation of the Papaloizou-Pringle instability compared to aligned/antialigned systems, although with a shorter mode growth time scale, (iv) acquisition of a small black-hole kick velocity, (v) significant gravitational-wave emission via various modes beyond, but as strong as, the typical (2,2) mode, and (vi) the possibility of a broad alignment of the angular momentum of the disk with the black hole spin. This alignment is not related to the Bardeen-Petterson effect and resembles a solid body rotation. Our simulations suggest that any electromagnetic luminosity from our models may power relativistic jets, such as those characterizing short gamma-ray bursts. Depending on the black-hole-disk system scale the gravitational waves may be detected by LIGO/Virgo, LISA and/or other laser interferometers.