Modeling Direct Waves in Binary Black Hole Ringdowns

Code accompanying the paper:

Modeling Direct Waves in Binary Black Hole Ringdowns Richard Dyer, Adrian Ka-Wai Chung, and Christopher J. Moore arXiv:2606.25021

@article{Dyer:2026:DirectWaves,
    author        = {Dyer, Richard and Chung, Adrian Ka-Wai and Moore, Christopher J.},
    title         = {Modeling Direct Waves in Binary Black Hole Ringdowns},
    year          = {2026},
    eprint        = {2606.25021},
    archivePrefix = {arXiv},
    primaryClass  = {gr-qc},
    doi           = {10.48550/arXiv.2606.25021},
}

Overview

This repository contains the code for identifying and characterising direct wave (DW) contributions in the gravitational wave ringdown signal from binary black hole mergers in numerical relativity simulations.

Dependencies

• bgp_qnm_fits (v2.0)
• qnmfits

Data

Waveforms must be downloaded separately from the SXS catalog. We use the Cauchy-characteristic extracted (CCE) simulations 0001-0013, Bondi news, Lev 5 resolution. The scripts expect bgp_qnm_fits to handle loading via bgp.SXS_CCE(sxs_id, type="news", lev="Lev5", radius="R2"). See https://arxiv.org/pdf/2510.11783 for more details on processing the waveforms.

Generated intermediate data (mode content JSON files) are included in mode_content_files/. MCMC posterior samples are not tracked by git and must be regenerated with 3_free_frequency.py. For 10,000 steps this takes ~40 minutes.

Other simulations

The main paper focuses on simulation 0004. The mode content for the other simulations can be found in diagnostic_figs/mode_content/.

License

This project is licensed under the terms of the MIT License. See LICENSE for details.