GR-Athena++: Binary Neutron Star Merger Simulations with Neutrino Transport

Fuente: arXiv
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Auteurs principaux: Daszuta, Boris, Bernuzzi, Sebastiano, Jacobi, Maximilian, Gutiérrez, Eduardo M., Hammond, Peter, Cook, William, Radice, David
Format: Preprint
Publié: 2026
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author Daszuta, Boris
Bernuzzi, Sebastiano
Jacobi, Maximilian
Gutiérrez, Eduardo M.
Hammond, Peter
Cook, William
Radice, David
author_facet Daszuta, Boris
Bernuzzi, Sebastiano
Jacobi, Maximilian
Gutiérrez, Eduardo M.
Hammond, Peter
Cook, William
Radice, David
contents We present general-relativistic radiation magnetohydrodynamics simulations of binary neutron star mergers performed with GR-Athena++. Neutrino transport is treated using a moment-based, energy-integrated scheme (M1), augmented by neutrino number density evolution (N0). Our implementation is validated through an extensive suite of standard tests and demonstrated to perform robustly under adaptive mesh refinement. As a first application, we simulate the gravitational collapse of a uniformly rotating, magnetized neutron star, demonstrating stable radiation evolution through apparent-horizon formation using a novel excision technique based on the tapering of state vector evolution inside the horizon. To further test robustness in highly dynamic environments, we apply our code to two demanding binary neutron star merger scenarios. We investigate a long-lived remnant with the DD2 equation of state, evolved with full general-relativistic magnetohydrodynamics and M1 neutrino transport. Following this, a gravitational collapse scenario with the SFHo equation of state is explored. We showcase long-term stable evolution on neutrino cooling time-scales, demonstrating robust handling of excision and stable evolution of the post-collapse accretion phase in three-dimensional mergers with magnetic fields and neutrino radiation.
format Preprint
id arxiv_https___arxiv_org_abs_2602_18290
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle GR-Athena++: Binary Neutron Star Merger Simulations with Neutrino Transport
Daszuta, Boris
Bernuzzi, Sebastiano
Jacobi, Maximilian
Gutiérrez, Eduardo M.
Hammond, Peter
Cook, William
Radice, David
General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
We present general-relativistic radiation magnetohydrodynamics simulations of binary neutron star mergers performed with GR-Athena++. Neutrino transport is treated using a moment-based, energy-integrated scheme (M1), augmented by neutrino number density evolution (N0). Our implementation is validated through an extensive suite of standard tests and demonstrated to perform robustly under adaptive mesh refinement. As a first application, we simulate the gravitational collapse of a uniformly rotating, magnetized neutron star, demonstrating stable radiation evolution through apparent-horizon formation using a novel excision technique based on the tapering of state vector evolution inside the horizon. To further test robustness in highly dynamic environments, we apply our code to two demanding binary neutron star merger scenarios. We investigate a long-lived remnant with the DD2 equation of state, evolved with full general-relativistic magnetohydrodynamics and M1 neutrino transport. Following this, a gravitational collapse scenario with the SFHo equation of state is explored. We showcase long-term stable evolution on neutrino cooling time-scales, demonstrating robust handling of excision and stable evolution of the post-collapse accretion phase in three-dimensional mergers with magnetic fields and neutrino radiation.
title GR-Athena++: Binary Neutron Star Merger Simulations with Neutrino Transport
topic General Relativity and Quantum Cosmology
High Energy Astrophysical Phenomena
url https://arxiv.org/abs/2602.18290