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 degrees and 90 degrees) 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 similar 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.