A python package for extracting quasinormal modes from black-hole ringdown simulations.

Key Features • Installation • Usage • Paper Results • How to Cite • License

Key Features

• Fit ringdown waveforms with quasinormal modes (QNMs) using fixed frequencies, free frequencies, or mixed setups
• JAX-accelerated nonlinear least-squares fitting with variable projection (VARPRO) and Optimistix-based optimization
• Flexible QNM model fitting for remnant-parameter inference (M, a) and custom parametric models
• Custom mode and model framework for user-defined mode content beyond standard Kerr QNMs
• Agnostic mode identification and stability-based mode selection across varying fit start times
• Save/reuse fit outputs with pickle, and visualize amplitudes/phases with built-in plotting tools
• Call hyperfit polynomials to approximate QNM amplitudes in the ringdown of binary black hole (BBH) mergers

Installation

pip install jaxqualin

Usage

Basic usage examples can be found under the Examples tab on the package homepage.

Paper Results

Interactive plots of the methods paper results can be found under the Results tab on the package homepage.

How to Cite

Please cite the methods paper if you used our package to produce results in your publication. Here is the BibTeX entry:

@article{Cheung:2023vki,
    author = "Cheung, Mark Ho-Yeuk and Berti, Emanuele and Baibhav, Vishal and Cotesta, Roberto",
    title = "{Extracting linear and nonlinear quasinormal modes from black hole merger simulations}",
    eprint = "2310.04489",
    archivePrefix = "arXiv",
    primaryClass = "gr-qc",
    doi = "10.1103/PhysRevD.109.044069",
    journal = "Phys. Rev. D",
    volume = "109",
    number = "4",
    pages = "044069",
    year = "2024",
    note = "[Erratum: Phys.Rev.D 110, 049902 (2024), Erratum: Phys.Rev.D 112, 049901 (2025)]"
}

License

MIT

GitHub @mhycheung