Exploring the parameter space of hierarchical triple black hole systems

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Hauptverfasser: Attia, M., Sibony, Y.
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Veröffentlicht: 2025
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author Attia, M.
Sibony, Y.
author_facet Attia, M.
Sibony, Y.
contents We present a comprehensive exploration of hierarchical triple black hole (BH) systems to address the "initial separation" problem in gravitational wave astrophysics. This problem arises because isolated BH binaries must have extremely small initial separations to merge within a Hubble time via gravitational wave (GW) emission alone, separations at which their stellar progenitors would have merged prematurely. Using a modified JADE secular code incorporating GW energy loss, we systematically investigate a seven-dimensional parameter space: masses of three BHs (5-100 $M_\odot$ inner binary, 1-200 $M_\odot$ tertiary), inner/outer semimajor axes (1-200 AU and 100-10,000 AU), outer orbit eccentricity (0-0.9), and mutual inclination (40°-80°). We employed an adaptive MCMC approach sampling the merger/nonmerger transition boundary across nearly 15 million simulations. Results reveal merger-conducive regions correspond to asymmetric inner binary masses, large inner separations where von Zeipel-Lidov-Kozai (ZLK) mechanism operates effectively without relativistic precession suppression, small outer separations providing stronger perturbations, and large outer eccentricities bringing the tertiary closer at pericenter. Merger probability correlates positively with mutual inclination. We developed a classification scheme for nonmerging systems based on GW emission and ZLK oscillations. A trained neural network predicts merger outcomes with 99% ROC score and 95% accuracy (99.7% for high-confidence predictions), enabling rapid population synthesis. Validation against N-body integrations showed 87% qualitative agreement, confirming our methodology captures essential triple BH dynamics while enabling unprecedented-scale exploration of configurations resolving the initial separation problem.
format Preprint
id arxiv_https___arxiv_org_abs_2506_22519
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Exploring the parameter space of hierarchical triple black hole systems
Attia, M.
Sibony, Y.
High Energy Astrophysical Phenomena
Astrophysics of Galaxies
Solar and Stellar Astrophysics
General Relativity and Quantum Cosmology
We present a comprehensive exploration of hierarchical triple black hole (BH) systems to address the "initial separation" problem in gravitational wave astrophysics. This problem arises because isolated BH binaries must have extremely small initial separations to merge within a Hubble time via gravitational wave (GW) emission alone, separations at which their stellar progenitors would have merged prematurely. Using a modified JADE secular code incorporating GW energy loss, we systematically investigate a seven-dimensional parameter space: masses of three BHs (5-100 $M_\odot$ inner binary, 1-200 $M_\odot$ tertiary), inner/outer semimajor axes (1-200 AU and 100-10,000 AU), outer orbit eccentricity (0-0.9), and mutual inclination (40°-80°). We employed an adaptive MCMC approach sampling the merger/nonmerger transition boundary across nearly 15 million simulations. Results reveal merger-conducive regions correspond to asymmetric inner binary masses, large inner separations where von Zeipel-Lidov-Kozai (ZLK) mechanism operates effectively without relativistic precession suppression, small outer separations providing stronger perturbations, and large outer eccentricities bringing the tertiary closer at pericenter. Merger probability correlates positively with mutual inclination. We developed a classification scheme for nonmerging systems based on GW emission and ZLK oscillations. A trained neural network predicts merger outcomes with 99% ROC score and 95% accuracy (99.7% for high-confidence predictions), enabling rapid population synthesis. Validation against N-body integrations showed 87% qualitative agreement, confirming our methodology captures essential triple BH dynamics while enabling unprecedented-scale exploration of configurations resolving the initial separation problem.
title Exploring the parameter space of hierarchical triple black hole systems
topic High Energy Astrophysical Phenomena
Astrophysics of Galaxies
Solar and Stellar Astrophysics
General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2506.22519