http://arxiv.org/abs/2211.07158
Numerical-relativity simulations for seconds-long black hole-neutron star mergers are performed to obtain a self-consistent picture starting from the inspiral and the merger throughout the post-merger stages for a variety of setups. Irrespective of the initial and computational setups, we find qualitatively universal evolution processes: The dynamical mass ejection takes place together with a massive accretion disk formation after the neutron star is tidally disrupted; Subsequently, the magnetic field in the accretion disk is amplified by the magnetic winding, Kelvin-Helmholtz instability, and magnetorotational instability, which establish a turbulent state inducing the dynamo and angular momentum transport; The post-merger mass ejection by the effective viscous effects stemming from the magnetohydrodynamics turbulence sets in at $\sim300$-$500$ ms after the merger and continues for several hundred ms; A magnetosphere near the black-hole spin axis is developed and the collimated strong Poynting flux is generated with its lifetime of $\sim0.5$-$2$ s. The model of no equatorial-plane symmetry shows the reverse of the magnetic-field polarity in the magnetosphere, which is caused by the dynamo associated with the magnetorotational instability in the accretion disk. The model with initially toroidal fields shows the tilt of the disk and magnetosphere in the late post-merger stage because of the anisotropic post-merger mass ejection. These effects could terminate the strong Poynting-luminosity stage within the timescale of $\sim0.5$-$2$ s.
K. Hayashi, K. Kiuchi, K. Kyutoku, et. al.
Tue, 15 Nov 22
46/103
Comments: 29 pages, 19 figures, and 1 table. arXiv admin note: text overlap with arXiv:2111.04621