AthenaK simulations of the binary black hole merger GW150914

TL;DR

This paper introduces AthenaK, a GPU-accelerated code for simulating binary black hole mergers like GW150914, and demonstrates its accuracy and usefulness in waveform analysis and parameter estimation.

Contribution

The paper presents the first binary black hole simulations of GW150914 using AthenaK, validating its accuracy against established groups and providing tools for reproducible analysis.

Findings

Excellent agreement with SXS and RIT results in remnant properties

Maximum dephasing of 0.35 radians in dominant gravitational-wave mode

Broadly consistent parameter posteriors with semi-analytic waveform models

Abstract

We present new binary black hole simulations targeted to GW150914 using the GPU-accelerated code AthenaK. We compute the properties of the final remnant with the isolated horizon formalism and obtain gravitational-waveforms at future null infinity via Cauchy characteristic extraction. We compare our results with those obtained by the Simulating eXtreme Spacetimes (SXS) and Rochester Institute of Technology (RIT) groups, targeted to the same event. We find excellent agreement with the SXS and RIT results in the remnant mass, spin, and recoil velocity. For the dominant $(\ell,m)=(2,2)$ mode of the gravitational-wave signal we find maximum dephasing of $\Delta \phi \simeq 0.35$ and amplitude difference of $\Delta A/A \simeq 0.4\%$. We use our newly computed waveform to re-analyze the GW150914 data and find posteriors for chirp mass, luminosity distance, and inclination that are broadely consistent with those obtained using semi-analytic waveform models. This work demonstrates the viability of AthenaK for many-orbits binary black hole merger simulations. A step-by-step tutorial, including all necessary input files and analysis scripts to reproduce our results, is available on GitHub.