Evolving black hole-neutron star binaries in general relativity using pseudospectral and finite difference methods

TL;DR

This paper introduces a hybrid numerical code combining pseudospectral and finite difference methods to simulate black hole-neutron star binaries in general relativity, accurately capturing the inspiral, merger, and gravitational wave emission.

Contribution

The paper presents a novel computational framework that couples pseudospectral and finite difference techniques for simulating relativistic binary systems with high accuracy.

Findings

Successfully evolved equilibrium stars and accretion flows.

Simulated a full inspiral-merger process of a black hole-neutron star binary.

Extracted reliable gravitational waveforms from the simulation.

Abstract

We present a code for solving the coupled Einstein-hydrodynamics equations to evolve relativistic, self-gravitating fluids. The Einstein field equations are solved in generalized harmonic coordinates on one grid using pseudospectral methods, while the fluids are evolved on another grid using shock-capturing finite difference or finite volume techniques. We show that the code accurately evolves equilibrium stars and accretion flows. Then we simulate an equal-mass nonspinning black hole-neutron star binary, evolving through the final four orbits of inspiral, through the merger, to the final stationary black hole. The gravitational waveform can be reliably extracted from the simulation.