High accuracy binary black hole simulations with an extended wave zone

TL;DR

This paper introduces a new binary black hole simulation code with extended wave zone coverage, achieving high accuracy in waveform phase, amplitude, and ringdown frequencies, confirming the remnant black hole's properties.

Contribution

The paper presents a novel simulation approach combining multiple coordinate patches and adapted grids, significantly improving accuracy and efficiency in binary black hole evolutions.

Findings

Waveform phase accuracy better than 0.010% during inspiral

Waveform amplitude accuracy better than 0.090% during inspiral

Ringdown frequencies match perturbative calculations within 0.01%

Abstract

We present results from a new code for binary black hole evolutions using the moving-puncture approach, implementing finite differences in generalised coordinates, and allowing the spacetime to be covered with multiple communicating non-singular coordinate patches. Here we consider a regular Cartesian near zone, with adapted spherical grids covering the wave zone. The efficiencies resulting from the use of adapted coordinates allow us to maintain sufficient grid resolution to an artificial outer boundary location which is causally disconnected from the measurement. For the well-studied test-case of the inspiral of an equal-mass non-spinning binary (evolved for more than 8 orbits before merger), we determine the phase and amplitude to numerical accuracies better than 0.010% and 0.090% during inspiral, respectively, and 0.003% and 0.153% during merger. The waveforms, including the resolved higher harmonics, are convergent and can be consistently extrapolated to $r\to\infty$ throughout the simulation, including the merger and ringdown. Ringdown frequencies for these modes (to $(\ell,m)=(6,6)$) match perturbative calculations to within 0.01%, providing a strong confirmation that the remnant settles to a Kerr black hole with irreducible mass $M_{\rm irr} = 0.884355\pm20\times10^{-6}$ and spin $S_f/M_f^2 = 0.686923 \pm 10\times10^{-6}$