Binary Neutron Star Merger Simulations with a Calibrated Turbulence Model

TL;DR

This paper introduces a calibrated subgrid turbulence model for neutron star merger simulations, enabling more accurate predictions of their evolution and signals despite computational limitations.

Contribution

It extends the large-eddy simulation method to general relativity and calibrates it with high-resolution data, allowing turbulence effects to be included in moderate-resolution simulations.

Findings

Turbulence impacts gravitational wave signals quantitatively.

Turbulence influences the outflows in neutron star mergers.

The model provides a way to quantify turbulence uncertainties.

Abstract

Magnetohydrodynamic (MHD) turbulence in neutron star (NS) merger remnants can impact their evolution and multimessenger signatures, complicating the interpretation of present and future observations. Due to the high Reynolds numbers and the large computational costs of numerical relativity simulations, resolving all the relevant scales of the turbulence will be impossible for the foreseeable future. Here, we adopt a method to include subgrid-scale turbulence in moderate resolution simulations by extending the large-eddy simulation (LES) method to general relativity (GR). We calibrate our subgrid turbulence model with results from very-high-resolution GRMHD simulations, and we use it to perform NS merger simulations and study the impact of turbulence. We find that turbulence has a quantitative, but not qualitative impact on the evolution of NS merger remnants, on their gravitational wave signatures, and on the outflows generated in binary NS mergers. Our approach provides a viable path to quantify uncertainties due to turbulence in NS mergers.