Tidal Disruption Disks Formed and Fed by Stream-Stream and Stream-Disk
  Interactions in Global GRHD Simulations
  When a star passes close to a supermassive black hole (BH), the BH's tidal
forces rip it apart into a thin stream, leading to a tidal disruption event
(TDE). In this work, we study the post-disruption phase of TDEs in general
relativistic hydrodynamics (GRHD) using our GPU-accelerated code H-AMR. We
carry out the first grid-based simulation of a deep-penetration TDE ($\beta$=7)
with realistic system parameters: a black-hole-to-star mass ratio of $10^6$, a
parabolic stellar trajectory, and a nonzero BH spin. We also carry out a
simulation of a tilted TDE whose stellar orbit is inclined relative to the BH
midplane. We show that for our aligned TDE, an accretion disk forms due to the
dissipation of orbital energy with $\sim$20 percent of the infalling material
reaching the BH. The dissipation is initially dominated by violent
self-intersections and later by stream-disk interactions near the pericenter.
The self-intersections completely disrupt the incoming stream, resulting in
five distinct self-intersection events separated by approximately 12 hours and
a flaring in the accretion rate. We also find that the disk is eccentric with
mean eccentricity e$\approx$0.88. For our tilted TDE, we find only partial
self-intersections due to nodal precession near pericenter. Although these
partial intersections eject gas out of the orbital plane, an accretion disk
still forms with a similar accreted fraction of the material to the aligned
case. These results have important implications for disk formation in realistic
tidal disruptions. For instance, the periodicity in accretion rate induced by
the complete stream disruption may explain the flaring events from Swift
J1644+57.
