Impact of Magnetic Field Topology on Electromagnetic and Gravitational Waves from Binary Neutron Star Merger Remnants

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Auteurs principaux: Rainho, Inês, Bamber, Jamie, Guerra, Davide, Miravet-Tenés, Miquel, Ruiz, Milton, Tsokaros, Antonios, Shapiro, Stuart L.
Format: Preprint
Publié: 2025
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author Rainho, Inês
Bamber, Jamie
Guerra, Davide
Miravet-Tenés, Miquel
Ruiz, Milton
Tsokaros, Antonios
Shapiro, Stuart L.
author_facet Rainho, Inês
Bamber, Jamie
Guerra, Davide
Miravet-Tenés, Miquel
Ruiz, Milton
Tsokaros, Antonios
Shapiro, Stuart L.
contents We perform general relativistic magnetohydrodynamic (GRMHD) simulations of binary neutron star (BNS) mergers with four distinct magnetic field topologies: (i) a dipole pulsar-like configuration, (ii) a mixed linear superposition of poloidal and toroidal components inside the star, and (iii-iv) two topologies featuring a smooth transition from a confined mixed core to a pulsar-like structure at radii $0.95\,R_{\rm NS}$ and $0.5\,R_{\rm NS}$, with $R_{\rm NS}$ the radius of the star. The latter topologies are explored in BNS merger studies for the first time. We evolve systems with two equations of state (EoS), SLy and WFF1, with ADM masses 2.7 and 2.6, respectively, and include an additional lower-mass SLy binary to probe the behavior of long-lived remnants. We perform an extensive analysis of the emission properties of the systems, both electromagnetic and gravitational waves, and of the properties of the remnants, namely their frequency modes, density eigenfunctions, rotation, temperature, and convective stability. We report three key results: (1) for the first time, we assess the convective stability of magnetized remnants, extending previous unmagnetized analyses; (2) we identify a clear secondary peak in the gravitational-wave spectrum of pulsar-like configurations, consistent with the nonlinear coupling of the $m=0$ and $m=2$ modes, which is absent in other topologies; and (3) the magnetic field topology strongly influences the gravitational wave emission properties to the extent that nearby ($<50\,{\rm Mpc}$) events could allow one to observationally distinguish between different field structures with future gravitational-wave detectors. Across all models, we obtain luminosities compatible with short gamma-ray bursts (sGRBs), with purely poloidal configurations being the most efficient in driving possible relativistic jets.
format Preprint
id arxiv_https___arxiv_org_abs_2510_17511
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Impact of Magnetic Field Topology on Electromagnetic and Gravitational Waves from Binary Neutron Star Merger Remnants
Rainho, Inês
Bamber, Jamie
Guerra, Davide
Miravet-Tenés, Miquel
Ruiz, Milton
Tsokaros, Antonios
Shapiro, Stuart L.
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
We perform general relativistic magnetohydrodynamic (GRMHD) simulations of binary neutron star (BNS) mergers with four distinct magnetic field topologies: (i) a dipole pulsar-like configuration, (ii) a mixed linear superposition of poloidal and toroidal components inside the star, and (iii-iv) two topologies featuring a smooth transition from a confined mixed core to a pulsar-like structure at radii $0.95\,R_{\rm NS}$ and $0.5\,R_{\rm NS}$, with $R_{\rm NS}$ the radius of the star. The latter topologies are explored in BNS merger studies for the first time. We evolve systems with two equations of state (EoS), SLy and WFF1, with ADM masses 2.7 and 2.6, respectively, and include an additional lower-mass SLy binary to probe the behavior of long-lived remnants. We perform an extensive analysis of the emission properties of the systems, both electromagnetic and gravitational waves, and of the properties of the remnants, namely their frequency modes, density eigenfunctions, rotation, temperature, and convective stability. We report three key results: (1) for the first time, we assess the convective stability of magnetized remnants, extending previous unmagnetized analyses; (2) we identify a clear secondary peak in the gravitational-wave spectrum of pulsar-like configurations, consistent with the nonlinear coupling of the $m=0$ and $m=2$ modes, which is absent in other topologies; and (3) the magnetic field topology strongly influences the gravitational wave emission properties to the extent that nearby ($<50\,{\rm Mpc}$) events could allow one to observationally distinguish between different field structures with future gravitational-wave detectors. Across all models, we obtain luminosities compatible with short gamma-ray bursts (sGRBs), with purely poloidal configurations being the most efficient in driving possible relativistic jets.
title Impact of Magnetic Field Topology on Electromagnetic and Gravitational Waves from Binary Neutron Star Merger Remnants
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2510.17511