$\texttt{GR-Athena++}$ Simulations of Spinning Binary Black Hole Mergers

Abstract

We present the second release of the $\texttt{GR-Athena++}$ waveform catalog, comprising four new quasi-circular, non-precessing, spinning binary black hole simulations. These simulations are performed at high resolutions and represent a step toward generating high-fidelity gravitational waveforms that can eventually meet the accuracy requirements of upcoming next-generation detectors, including LISA, Cosmic Explorer, and Einstein Telescope. Gravitational waves are extracted at future null infinity ( $\mathscr{I}^{+}$) using both Cauchy characteristic extraction and finite-radius extraction. For each simulation, we provide strain data across multiple resolutions and analyze waveform accuracy via convergence studies and self-mismatch analyses. The absolute phase and relative amplitude differences reach their largest values near the merger, while the smallest errors are of order $\mathscr{O}(10^{-2})$ and $\mathscr{O}(10^{-3})$, respectively. A self-mismatch analysis of the dominant $(2,2)$ mode yields mismatches between $\mathscr{O}(10^{-5})$ and $\mathscr{O}(10^{-7})$ for a total binary mass of $10^{6}$ $M_{\odot}$ over the frequency range $[0.002, 0.1]$ Hz using LISA noise curve. All waveforms are publicly available via $\texttt{ScholarSphere}$.