# High accuracy simulations of black hole binaries:spins anti-aligned with the orbital angular momentum

## TL;DR

This paper presents high-accuracy simulations of equal-mass binary black holes with anti-aligned spins, achieving precise gravitational waveforms and analyzing the effects of different constraint damping parameters.

## Contribution

It introduces highly accurate binary black hole simulations with anti-aligned spins, improving waveform extraction and phase accuracy without phase shifts.

## Key findings

- Waveforms have phase errors less than 0.1 radians without shifts.
- Extrapolated waveforms differ by up to 0.13 radians in phase from finite-radius extraction.
- Constraint damping choices significantly reduce junk radiation and improve waveform quality.

## Abstract

High-accuracy binary black hole simulations are presented for black holes with spins anti-aligned with the orbital angular momentum. The particular case studied represents an equal-mass binary with spins of equal magnitude S/m^2=0.43757 \pm 0.00001. The system has initial orbital eccentricity ~4e-5, and is evolved through 10.6 orbits plus merger and ringdown. The remnant mass and spin are M_f=(0.961109 \pm 0.000003)M and S_f/M_f^2=0.54781 \pm 0.00001, respectively, where M is the mass during early inspiral. The gravitational waveforms have accumulated numerical phase errors of <~ 0.1 radians without any time or phase shifts, and <~ 0.01 radians when the waveforms are aligned with suitable time and phase shifts. The waveform is extrapolated to infinity using a procedure accurate to <~ 0.01 radians in phase, and the extrapolated waveform differs by up to 0.13 radians in phase and about one percent in amplitude from the waveform extracted at finite radius r=350M. The simulations employ different choices for the constraint damping parameters in the wave zone; this greatly reduces the effects of junk radiation, allowing the extraction of a clean gravitational wave signal even very early in the simulation.