Removing degeneracy and multimodality in gravitational wave source parameters

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

Submitted on 7 July 2022


Quasicircular binary black hole mergers are described by 15 parameters, of which gravitational wave observations can typically constrain only 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 can be measured remarkably well in the presence of orbital precession, and we anticipate that this will shed light on the occurrence of spin-orbit misalignment in nature.


Comment: 16 pages, 13 figures, 1 table

Subjects: General Relativity and Quantum Cosmology; Astrophysics - High Energy Astrophysical Phenomena; Astrophysics - Instrumentation and Methods for Astrophysics