Binary Neutron Star Merger Simulations with a Calibrated Turbulence Model

David Radice

doi:10.3390/sym12081249

Abstract

Magnetohydrodynamic (MHD) turbulence in neutron star (NS) merger remnants can impact their evolution and multi-messenger 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.

Highlights

Binary neutron star (BNS) mergers are prime targets for the ground-based laser interferometric gravitational-wave (GW) detectors LIGO [1], Virgo [2], and KAGRA [3]
We perform BNS merger simulations with microphysics and compare the results obtained with the newly calibrated turbulence model with those obtained using the prescription we proposed in [81], which was used in several other works [58,61,87,88,89,90], and with those obtained with traditional GRHD simulations having no subgrid model
The merger produced an massive NS (MNS) remnant that collapsed to a black hole (BH) surrounded by a massive accretion torus, typically within the simulation time

Summary

Introduction

Binary neutron star (BNS) mergers are prime targets for the ground-based laser interferometric gravitational-wave (GW) detectors LIGO [1], Virgo [2], and KAGRA [3]. BNS mergers can eject neutron-rich material, which subsequently produces heavy elements, such as gold and uranium, through the r-process [4,13,14,15]. At the time of writing, one more BNS GW event after GW170817 has been announced by the LIGO/Virgo collaboration (LVC): GW190425 [16,17]. Several more candidates have been reported and are currently being analyzed by the LVC [18]. Many more detections are expected in the years as GW observatories improve their sensitives and as more facilities are added to the global network of detectors [19]

Methods

Results

Conclusion