GR-Athena++ simulations of spinning binary black hole mergers

We present the second release of the 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 ( 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 O ( 10 − 2 ) and O ( 10 − 3 ) , respectively. A self-mismatch analysis of the dominant (2, 2) mode yields mismatches between O ( 10 − 5 ) and O ( 10 − 7 ) for a total binary mass of 10 6 M ⊙ over the frequency range f ∈ [ 0.002 , 0.1 ] Hz using LISA’s noise curve. All waveforms are publicly available via ScholarSphere.