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Tidal Disruption Disks Formed and Fed by Stream-Stream and Stream-Disk Interactions in Global GRHD Simulations

Presentation #206.01 in the session “Theoretical Advances in Tidal Disruption Events”.

Published onApr 01, 2022
Tidal Disruption Disks Formed and Fed by Stream-Stream and Stream-Disk Interactions in Global GRHD Simulations

When a star makes a close pass to a supermassive black hole (SMBH), the enormous tidal forces tear the star apart against its own self-gravity in what is known as a tidal disruption event (TDE). After the initial disruption, the gravitationally bound half of the star falls back onto the BH as a stream of stellar debris. In this work, we study the post-disruption phase of TDEs in general relativistic magnetohydrodynamics (GRMHD) using our GPU-accelerated code H-AMR. We carry out grid-based simulations of deep-penetration (β=7) TDEs with realistic physical parameters: a BH-to-star mass ratio of 106, a parabolic stellar trajectory, and a nonzero BH spin. We run two simulations, one where the stellar orbit lies in the BH midplane and one where the stellar orbit is inclined by 30 degrees. In both simulations, an eccentric (e~0.88) accretion disk forms due to the dissipation of orbital energy with ~20 percent of the infalling material reaching the BH. In the aligned simulation, the dissipation is initially dominated by violent self-intersections of the debris stream and later by stream-disk interactions near the orbital pericenter. The self-intersections completely disrupt the incoming stream, resulting in 5 distinct self-intersection events separated by approximately 12 hours and a flaring in the accretion rate. In the tilted simulation, we find only partial self-intersections due to nodal precession. Disk precession is inhibited by the constant inflow of matter in the orbital plane of the star. These results have important implications for disk formation in realistic tidal disruptions. Specifically, the periodicity in accretion rate induced by the complete stream disruption may explain the flaring events from TDE Swift J1644+57.

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