Unveiling the merger structure of black hole binaries in generic planar orbits

Gregorio Carullo, Simone Albanesi, Alessandro Nagar, Rossella Gamba, Sebastiano Bernuzzi, Tomas Andrade, Juan Trenado
General Relativity and Quantum Cosmology, General Relativity and Quantum Cosmology (gr-qc), High Energy Astrophysical Phenomena (astro-ph.HE)
2023-09-12 16:00:00
The precise modeling of binary black hole coalescences in generic planar orbits is a crucial step to disentangle dynamical and isolated binary formation channels through gravitational-wave observations. The merger regime of such coalescences exhibits a significantly higher complexity compared to the quasicircular case, and cannot be readily described through standard parameterizations in terms of eccentricity and anomaly. In the spirit of the Effective One Body formalism, we build on the study of the test-mass limit, and show how gauge-invariant combinations of the binary energy and angular momentum, such as a dynamical "impact parameter" at merger, overcome this challenge. These variables reveal simple "quasi-universal" structures of the pivotal merger parameters, allowing to build an accurate analytical representation of generic (bounded and dynamically-bounded) orbital configurations. We demonstrate the validity of these analytical relations using 255 numerical simulations of bounded noncircular binaries with nonspinning progenitors from the RIT and SXS catalogs, together with a custom dataset of dynamical captures generated using the Einstein Toolkit, and test-mass data in bound orbits. Our modeling strategy lays the foundations of accurate and complete waveform models for systems in arbitrary orbits, bolstering observational explorations of dynamical formation scenarios and the discovery of new classes of gravitational wave sources.
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