Simulating binary neutron stars: dynamics and gravitational waves

TL;DR

This paper models binary neutron star mergers, analyzing gravitational waveforms and orbital dynamics, and verifies numerical methods through comparisons with perturbation theory, advancing simulations of such astrophysical events.

Contribution

It introduces a comprehensive 3D simulation framework for binary neutron star mergers, including black hole formation and neutron star remnants, with detailed gravitational waveform extraction and code validation.

Findings

Successful simulation of black hole formation from neutron star mergers

Accurate gravitational waveforms matching theoretical predictions

Validated numerical methods against perturbation theory

Abstract

We model two mergers of orbiting binary neutron stars, the first forming a black hole and the second a differentially rotating neutron star. We extract gravitational waveforms in the wave zone. Comparisons to a post-Newtonian analysis allow us to compute the orbital kinematics, including trajectories and orbital eccentricities. We verify our code by evolving single stars and extracting radial perturbative modes, which compare very well to results from perturbation theory. The Einstein equations are solved in a first order reduction of the generalized harmonic formulation, and the fluid equations are solved using a modified convex essentially non-oscillatory method. All calculations are done in three spatial dimensions without symmetry assumptions. We use the \had computational infrastructure for distributed adaptive mesh refinement.