Numerical relativity simulations of binary neutron stars

TL;DR

This paper introduces an advanced numerical relativity code for simulating binary neutron star mergers, incorporating matter dynamics, high-resolution shock capturing, and mesh refinement, validated through standard tests and gravitational wave analysis.

Contribution

The paper presents a new, upgraded numerical relativity code capable of simulating matter-involving binary neutron star systems with improved accuracy and validation methods.

Findings

Validated the code with standard neutron star tests

Simulated late inspiral to merger binary neutron stars

Analyzed gravitational wave emission and convergence

Abstract

We present a new numerical relativity code designed for simulations of compact binaries involving matter. The code is an upgrade of the BAM code to include general relativistic hydrodynamics and implements state-of-the-art high-resolution-shock-capturing schemes on a hierarchy of mesh refined Cartesian grids with moving boxes. We test and validate the code in a series of standard experiments involving single neutron star spacetimes. We present test evolutions of quasi-equilibrium equal-mass irrotational binary neutron star configurations in quasi-circular orbits which describe the late inspiral to merger phases. Neutron star matter is modeled as a zero-temperature fluid; thermal effects can be included by means of a simple ideal-gas prescription. We analyze the impact that the use of different values of damping parameter in the Gamma-driver shift condition has on the dynamics of the system. The use of different reconstruction schemes and their impact in the post-merger dynamics is investigated. We compute and characterize the gravitational radiation emitted by the system. Self-convergence of the waves is tested, and we consistently estimate error-bars on the numerically generated waveforms in the inspiral phase.