Magnetic Field Configurations in Binary Neutron Star Mergers II: Inspiral, Merger and Ejecta

Fuente: arXiv
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Autores principales: Cook, William, Gutiérrez, Eduardo M., Bernuzzi, Sebastiano, Radice, David, Daszuta, Boris, Fields, Jacob, Hammond, Peter, Bandyopadhyay, Harshraj, Jacobi, Maximilian
Formato: Preprint
Publicado: 2025
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author Cook, William
Gutiérrez, Eduardo M.
Bernuzzi, Sebastiano
Radice, David
Daszuta, Boris
Fields, Jacob
Hammond, Peter
Bandyopadhyay, Harshraj
Jacobi, Maximilian
author_facet Cook, William
Gutiérrez, Eduardo M.
Bernuzzi, Sebastiano
Radice, David
Daszuta, Boris
Fields, Jacob
Hammond, Peter
Bandyopadhyay, Harshraj
Jacobi, Maximilian
contents We perform a series of simulations of magnetised Binary Neutron Star mergers, with varying magnetic field topologies in the initial data, as well as varying Equations of State, and mass ratios. In this paper, a companion paper to arXiv:2506.18995, we analyse the impact of the initial field configuration on the gravitational wave signal, the amplification of the magnetic field, and the ejected material. We investigate the dependence of the phase evolution of the gravitational wave in the post-merger on the initial magnetic field, finding that dephasing between the $(\ell=2,m=2)$ mode of the gravitational wave, and the $(2,1)$ and $(3,3)$ modes may be strongly impacted by the numerical reconstruction scheme. The magnetic field amplification during the Kelvin-Helmholtz dominated phase may be considerably enhanced by anti-aligned fields, or suppressed by toroidal fields. The post-merger amplification of the field due to winding may be suppressed by toroidal fields, and enhanced by asymmetries or mixtures of poloidal and toroidal fields. The field strength in the ejecta may be impacted by the initial magnetic field, with configurations which lead to large amplifications and those with mixtures of poloidal and toroidal fields preferentially emitting highly magnetised material in the polar regions, showing a weaker dependence of the magnetic field on the density of the ejecta than in cases that amplify the magnetic field less. We find that the magnetic field is largely randomly oriented in the ejected material, supporting such models used to estimate thermalisation timescales of ejected material. We find that configurations which begin with an initial bitant symmetry break this symmetry uniformly, independent of the initial configuration, when evolved without an enforced symmetry. This behaviour suggests the presence of a spontaneous symmetry breaking bifurcation in the solution.
format Preprint
id arxiv_https___arxiv_org_abs_2508_19342
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Magnetic Field Configurations in Binary Neutron Star Mergers II: Inspiral, Merger and Ejecta
Cook, William
Gutiérrez, Eduardo M.
Bernuzzi, Sebastiano
Radice, David
Daszuta, Boris
Fields, Jacob
Hammond, Peter
Bandyopadhyay, Harshraj
Jacobi, Maximilian
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
We perform a series of simulations of magnetised Binary Neutron Star mergers, with varying magnetic field topologies in the initial data, as well as varying Equations of State, and mass ratios. In this paper, a companion paper to arXiv:2506.18995, we analyse the impact of the initial field configuration on the gravitational wave signal, the amplification of the magnetic field, and the ejected material. We investigate the dependence of the phase evolution of the gravitational wave in the post-merger on the initial magnetic field, finding that dephasing between the $(\ell=2,m=2)$ mode of the gravitational wave, and the $(2,1)$ and $(3,3)$ modes may be strongly impacted by the numerical reconstruction scheme. The magnetic field amplification during the Kelvin-Helmholtz dominated phase may be considerably enhanced by anti-aligned fields, or suppressed by toroidal fields. The post-merger amplification of the field due to winding may be suppressed by toroidal fields, and enhanced by asymmetries or mixtures of poloidal and toroidal fields. The field strength in the ejecta may be impacted by the initial magnetic field, with configurations which lead to large amplifications and those with mixtures of poloidal and toroidal fields preferentially emitting highly magnetised material in the polar regions, showing a weaker dependence of the magnetic field on the density of the ejecta than in cases that amplify the magnetic field less. We find that the magnetic field is largely randomly oriented in the ejected material, supporting such models used to estimate thermalisation timescales of ejected material. We find that configurations which begin with an initial bitant symmetry break this symmetry uniformly, independent of the initial configuration, when evolved without an enforced symmetry. This behaviour suggests the presence of a spontaneous symmetry breaking bifurcation in the solution.
title Magnetic Field Configurations in Binary Neutron Star Mergers II: Inspiral, Merger and Ejecta
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2508.19342