Tidal disruptions by rotating black holes: effects of spin and impact parameter
Abstract
We present the results of relativistic smoothed particle hydrodynamics simulations of tidal disruptions of stars by rotating supermassive black holes, for a wide range of impact parameters and black hole spins. For deep encounters, we find that: relativistic precession creates debris geometries impossible to obtain with the Newtonian equations; part of the fluid can be launched on plunging orbits, reducing the fallback rate and the mass of the resulting accretion disc; multiple squeezings and bounces at periapsis may generate distinctive Xray signatures resulting from the associated shock breakout; disruptions can occur inside the marginally bound radius, if the angular momentum spread launches part of the debris on nonplunging orbits. Perhaps surprisingly, we also find relativistic effects important in partial disruptions, where the balance between selfgravity and tidal forces is so precarious that otherwise minor relativistic effects can have decisive consequences on the stellar fate. In between, where the star is fully disrupted but relativistic effects are mild, the difference resides in a gentler rise of the fallback rate, a later and smaller peak, and longer return times. However, relativistic precession always causes thicker debris streams, both in the bound part (speeding up circularization) and in the unbound part (accelerating and enhancing the production of separate transients). We discuss various properties of the disruption (compression at periapsis, shape and spread of the energy distribution) and potential observables (peak fallback rate, times of rise and decay, duration of superEddington fallback) as a function of the impact parameter and the black hole spin.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 August 2019
 DOI:
 10.1093/mnras/stz1530
 arXiv:
 arXiv:1903.09147
 Bibcode:
 2019MNRAS.487.4790G
 Keywords:

 black hole physics;
 hydrodynamics;
 relativistic processes;
 methods: numerical;
 galaxies: nuclei;
 Astrophysics  High Energy Astrophysical Phenomena;
 General Relativity and Quantum Cosmology
 EPrint:
 19 pages, 18 figures