General-relativistic radiation magnetohydrodynamics simulations of binary neutron star mergers: The influence of spin on the multi-messenger picture

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Main Authors: Neuweiler, Anna, Gieg, Henrique, Rose, Henrik, Koehn, Hauke, Markin, Ivan, Schianchi, Federico, Brodie, Liam, Haber, Alexander, Nedora, Vsevolod, Bulla, Mattia, Dietrich, Tim
Format: Preprint
Published: 2025
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author Neuweiler, Anna
Gieg, Henrique
Rose, Henrik
Koehn, Hauke
Markin, Ivan
Schianchi, Federico
Brodie, Liam
Haber, Alexander
Nedora, Vsevolod
Bulla, Mattia
Dietrich, Tim
author_facet Neuweiler, Anna
Gieg, Henrique
Rose, Henrik
Koehn, Hauke
Markin, Ivan
Schianchi, Federico
Brodie, Liam
Haber, Alexander
Nedora, Vsevolod
Bulla, Mattia
Dietrich, Tim
contents The rich phenomenology of binary neutron star mergers offers a unique opportunity to test general relativity, investigate matter at supranuclear densities, and learn more about the origin of heavy elements. As multi-messenger sources, they emit both gravitational waves and electromagnetic radiation across several frequency bands. The interpretation of these signals relies heavily on accurate numerical-relativity simulations that incorporate the relevant microphysical processes. Using the latest updates of the BAM code, we perform general-relativistic radiation magnetohydrodynamic simulations of binary neutron star mergers with two different spin configurations. We adopt a state-of-the-art equation of state based on relativistic mean-field theory developed for dense matter in neutron star mergers. To capture both dynamical ejecta and secular outflows from magnetic and neutrino-driven winds, we evolve the systems up to $\sim 100\ \rm ms$ after the merger at considerably high resolution with a grid spacing of $Δx \approx 93\ \rm m$ across the neutron stars. Our results show that the non-spinning configuration undergoes a more violent merger, producing more ejecta with lower electron fraction and higher velocities, while the spinning configuration forms a larger disk due to its higher angular momentum. Although the initial magnetic field amplification within $\lesssim 10\ \rm ms$ after merger is similar in both systems, the non-spinning system reaches stronger magnetic fields and higher energies at later times. For a detailed view of the multi-messenger observables, we extract the gravitational-wave signal and compute nucleosynthesis yields, the expected kilonova and afterglow light curves from our ejecta profiles.
format Preprint
id arxiv_https___arxiv_org_abs_2510_14850
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle General-relativistic radiation magnetohydrodynamics simulations of binary neutron star mergers: The influence of spin on the multi-messenger picture
Neuweiler, Anna
Gieg, Henrique
Rose, Henrik
Koehn, Hauke
Markin, Ivan
Schianchi, Federico
Brodie, Liam
Haber, Alexander
Nedora, Vsevolod
Bulla, Mattia
Dietrich, Tim
High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
The rich phenomenology of binary neutron star mergers offers a unique opportunity to test general relativity, investigate matter at supranuclear densities, and learn more about the origin of heavy elements. As multi-messenger sources, they emit both gravitational waves and electromagnetic radiation across several frequency bands. The interpretation of these signals relies heavily on accurate numerical-relativity simulations that incorporate the relevant microphysical processes. Using the latest updates of the BAM code, we perform general-relativistic radiation magnetohydrodynamic simulations of binary neutron star mergers with two different spin configurations. We adopt a state-of-the-art equation of state based on relativistic mean-field theory developed for dense matter in neutron star mergers. To capture both dynamical ejecta and secular outflows from magnetic and neutrino-driven winds, we evolve the systems up to $\sim 100\ \rm ms$ after the merger at considerably high resolution with a grid spacing of $Δx \approx 93\ \rm m$ across the neutron stars. Our results show that the non-spinning configuration undergoes a more violent merger, producing more ejecta with lower electron fraction and higher velocities, while the spinning configuration forms a larger disk due to its higher angular momentum. Although the initial magnetic field amplification within $\lesssim 10\ \rm ms$ after merger is similar in both systems, the non-spinning system reaches stronger magnetic fields and higher energies at later times. For a detailed view of the multi-messenger observables, we extract the gravitational-wave signal and compute nucleosynthesis yields, the expected kilonova and afterglow light curves from our ejecta profiles.
title General-relativistic radiation magnetohydrodynamics simulations of binary neutron star mergers: The influence of spin on the multi-messenger picture
topic High Energy Astrophysical Phenomena
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2510.14850