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arXiv · 2207.03508

Removing degeneracy and multimodality in gravitational wave source parameters

Javier Roulet·Seth Olsen·Jonathan Mushkin·Tousif Islam·Tejaswi Venumadhav·Barak Zackay·Matias Zaldarriaga
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Abstract

Quasicircular binary black hole mergers are described by 15 parameters, of which gravitational wave observations can typically constrain only $\sim 10$ independent combinations to varying degree. In this work, we devise coordinates that remove correlations, and disentangle well- and poorly-measured quantities. Additionally, we identify approximate discrete symmetries in the posterior as the primary cause of multimodality, and design a method to tackle this type of multimodality. The resulting posteriors have little structure and can be sampled efficiently and robustly. We provide a Python package for parameter estimation, cogwheel, that implements these methods together with other algorithms for accelerating the inference process. One of the coordinates we introduce is a spin azimuth that is measured remarkably well in several events. We suggest this might be a sensitive indicator of orbital precession, and we anticipate that it will shed light on the occurrence of spin-orbit misalignment in nature.

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Javier Roulet, Seth Olsen, Jonathan Mushkin, Tousif Islam, Tejaswi Venumadhav, Barak Zackay, Matias Zaldarriaga. 2022-07-07. Removing degeneracy and multimodality in gravitational wave source parameters. https://doi.org/10.1103/physrevd.106.123015

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