GR-Athena++: General-relativistic Magnetohydrodynamics Simulations of Neutron Star Spacetimes

Year: 2025

Type: article

Abstract: We present the extension of GR-Athena++ to general-relativistic magnetohydrodynamics (GRMHD) for applications to neutron star spacetimes. The new solver couples the constrained transport implementation of Athena++ to the Z4c formulation of the Einstein equations to simulate dynamical spacetimes with GRMHD using oct-tree adaptive mesh refinement. We consider benchmark problems for isolated and binary neutron star spacetimes demonstrating stable and convergent results at relatively low resolutions and without grid symmetries imposed. The code correctly captures magnetic field instabilities in nonrotating stars with total relative violation of the divergence-free constraint of 10 −16 . It handles evolutions with a microphysical equation of state and black hole formation in the gravitational collapse of a rapidly rotating star. For binaries, we demonstrate correctness of the evolution under the gravitational radiation reaction and show convergence of gravitational waveforms. We showcase the use of adaptive mesh refinement to resolve the Kelvin–Helmholtz instability at the collisional interface in a merger of magnetised binary neutron stars. GR-Athena++ shows strong scaling efficiencies above 80% in excess of 10 5 CPU cores and excellent weak scaling is shown up to ∼5 × 10 5 CPU cores in a realistic production setup. GR-Athena++ allows for the robust simulation of GRMHD flows in strong and dynamical gravity with exa-scale computers.

Source: The Astrophysical Journal Supplement Series

DOI: 10.3847/1538-4365/ad87d4

Authors: William Cook, Boris Daszuta, Jacob Fields, Peter Hammond, Simone Albanesi, Francesco Zappa, Sebastiano Bernuzzi, David Radice

Institutions: Pennsylvania State University, Friedrich Schiller University Jena, Istituto Nazionale di Fisica Nucleare, Sezione di Torino, University of Turin

Language: English

Topic: Pulsars and Gravitational Waves Research

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $4,499

Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Friedrich-Schiller-Universität Jena, Deutsche Forschungsgemeinschaft, Nuclear Safety and Security Commission, Gauss Centre for Supercomputing, Office of Science, Horizon 2020 Framework Programme, Leibniz-Gemeinschaft, Leibniz-Rechenzentrum, Nuclear Physics

OpenAlex ID: W4407389058