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arXiv · 2608.23310

Binary Neutron Star Merger Simulations with Microphysical Equation of State using Spritz

Fatemeh Hossein Nouri·Jay V. Kalinani·Bruno Giacomazzo·Riccardo Ciolfi·Albino Perego
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Abstract

We present the first binary neutron star merger simulations performed with the general-relativistic magnetohydrodynamics (GRMHD) Spritz code employing a finite-temperature tabulated equation of state. Two magnetized binaries with the LS220 equation of state and a GW170817-like chirp mass, differing only in their mass ratios ($q=1$ and $q=0.7$), are evolved from the late inspiral through merger, hypermassive neutron-star (HMNS) formation, and delayed collapse to a black hole (BH). We investigate how the binary mass ratio influences the postmerger evolution, jet-launching conditions, and matter ejection. We find that the equal-mass binary forms a slightly longer-lived HMNS, allowing more efficient magnetic-field amplification during the post-merger evolution. As a result, it accumulates larger magnetic fluxes, develops a magnetically dominated funnel, and launches a collimated magnetically driven polar outflow. In contrast, the unequal-mass binary ejects approximately 50% more mass but exhibits weaker magnetic-field amplification, with the polar region remaining turbulent and baryon loaded throughout our simulation, suggesting that the development of a magnetically dominated funnel is likely delayed.

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Fatemeh Hossein Nouri, Jay V. Kalinani, Bruno Giacomazzo, Riccardo Ciolfi, Albino Perego. 2026-08-24. Binary Neutron Star Merger Simulations with Microphysical Equation of State using Spritz. https://arxiv.org/abs/2608.23310

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