Evolution of the Magnetized, Neutrino-Cooled Accretion Disk in the Aftermath of a Black Hole Neutron Star Binary Merger

Black hole-torus systems from compact binary mergers are possible engines for gamma-ray bursts (GRBs). During the early evolution of the post-merger remnant, the state of the torus is determined by a combination of neutrino cooling and magnetically-driven heating processes, so realistic models must...

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Bibliographic Details
Published in:arXiv.org 2017-10
Main Authors: Fatemeh Hossein Nouri, Duez, Matthew D, Foucart, Francois, Deaton, M Brett, Haas, Roland, Haddadi, Milad, Kidder, Lawrence E, Ott, Christian D, Pfeiffer, Harald P, Scheel, Mark A, Szilagyi, Bela
Format: Article
Language:English
Subjects:
Accretion disks
Angular momentum
Binary stars
Black holes
Computational fluid dynamics
Computer simulation
Cooling effects
Equations of state
Field strength
Gamma ray bursts
Gamma rays
Heating rate
Luminosity
Magnetohydrodynamic turbulence
Mathematical analysis
Mathematical models
Neutrinos
Neutron stars
Numerical relativity
Relativity
Stellar evolution
Stellar system evolution
Temperature effects
Toruses
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Summary:Black hole-torus systems from compact binary mergers are possible engines for gamma-ray bursts (GRBs). During the early evolution of the post-merger remnant, the state of the torus is determined by a combination of neutrino cooling and magnetically-driven heating processes, so realistic models must include both effects. In this paper, we study the post-merger evolution of a magnetized black hole-neutron star binary system using the Spectral Einstein Code (SpEC) from an initial post-merger state provided by previous numerical relativity simulations. We use a finite-temperature nuclear equation of state and incorporate neutrino effects in a leakage approximation. To achieve the needed accuracy, we introduce improvements to SpEC's implementation of general-relativistic magnetohydrodynamics (MHD), including the use of cubed-sphere multipatch grids and an improved method for dealing with supersonic accretion flows where primitive variable recovery is difficult. We find that a seed magnetic field triggers a sustained source of heating, but its thermal effects are largely cancelled by the accretion and spreading of the torus from MHD-related angular momentum transport. The neutrino luminosity peaks at the start of the simulation, and then drops significantly over the first 20\,ms but in roughly the same way for magnetized and nonmagnetized disks. The heating rate and disk's luminosity decrease much more slowly thereafter. These features of the evolution are insensitive to grid structure and resolution, formulation of the MHD equations, and seed field strength, although turbulent effects are not fully converged
ISSN:2331-8422
DOI:10.48550/arxiv.1710.07423