Analysis and simulations of binary black hole merger spins -- the question of spin-axis tossing at black hole formation

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Autori principali: Larsen, Hans C. G., Pedersen, Casper C., Tauris, Thomas M., Sepas, Ali, Larsen, Claudia, Biscio, Christophe A. N.
Natura: Preprint
Pubblicazione: 2025
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author Larsen, Hans C. G.
Pedersen, Casper C.
Tauris, Thomas M.
Sepas, Ali
Larsen, Claudia
Biscio, Christophe A. N.
author_facet Larsen, Hans C. G.
Pedersen, Casper C.
Tauris, Thomas M.
Sepas, Ali
Larsen, Claudia
Biscio, Christophe A. N.
contents The origin of binary black hole (BH) mergers remains a topic of active debate, with effective spins (chi_eff) measured by the LIGO-Virgo-KAGRA (LVK) Collaboration providing crucial insights. In this study, our objective is to investigate the empirical chi_eff distribution (and constrain individual spin components) of binary BH mergers and compare them with extensive simulations, assuming that they originate purely from isolated binaries or a mixture of formation channels. We explore scenarios using BH kicks with and without the effect of spin-axis tossing during BH formation. We employ simple yet robust Monte Carlo simulations of the final core collapse forming the second-born BH, using minimal assumptions to ensure transparency and reproducibility. The synthetic chi_eff distribution is compared to the empirical data from LVK science runs O1-O3 using functional data analysis, kernel density estimations, and three different statistical tests, accounting for data uncertainties. We find strong indications for spin-axis tossing during BH formation if LVK sources are dominated by the isolated binary channel. Simulations with spin-axis tossing achieve high p-values (up to 0.882) using Kolmogorov-Smirnov, Cramer-von Mises, and Anderson-Darling tests, while without tossing, all p-values drop below 0.001 for isolated binaries. A statistically acceptable solution without tossing, however, emerges if ~72+/-8% of detected binary BH mergers result from dynamical interactions causing random BH spin directions. Finally, for an isolated binary origin, we find a preference for mass reversal in ~30% of the progenitor binaries. Predictions from this study can be tested with LVK O4+O5 data as well as the 3G detectors, Einstein Telescope and Cosmic Explorer, enabling improved constraints on formation channel ratios and the critical question of BH spin-axis tossing.
format Preprint
id arxiv_https___arxiv_org_abs_2508_03809
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Analysis and simulations of binary black hole merger spins -- the question of spin-axis tossing at black hole formation
Larsen, Hans C. G.
Pedersen, Casper C.
Tauris, Thomas M.
Sepas, Ali
Larsen, Claudia
Biscio, Christophe A. N.
High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
The origin of binary black hole (BH) mergers remains a topic of active debate, with effective spins (chi_eff) measured by the LIGO-Virgo-KAGRA (LVK) Collaboration providing crucial insights. In this study, our objective is to investigate the empirical chi_eff distribution (and constrain individual spin components) of binary BH mergers and compare them with extensive simulations, assuming that they originate purely from isolated binaries or a mixture of formation channels. We explore scenarios using BH kicks with and without the effect of spin-axis tossing during BH formation. We employ simple yet robust Monte Carlo simulations of the final core collapse forming the second-born BH, using minimal assumptions to ensure transparency and reproducibility. The synthetic chi_eff distribution is compared to the empirical data from LVK science runs O1-O3 using functional data analysis, kernel density estimations, and three different statistical tests, accounting for data uncertainties. We find strong indications for spin-axis tossing during BH formation if LVK sources are dominated by the isolated binary channel. Simulations with spin-axis tossing achieve high p-values (up to 0.882) using Kolmogorov-Smirnov, Cramer-von Mises, and Anderson-Darling tests, while without tossing, all p-values drop below 0.001 for isolated binaries. A statistically acceptable solution without tossing, however, emerges if ~72+/-8% of detected binary BH mergers result from dynamical interactions causing random BH spin directions. Finally, for an isolated binary origin, we find a preference for mass reversal in ~30% of the progenitor binaries. Predictions from this study can be tested with LVK O4+O5 data as well as the 3G detectors, Einstein Telescope and Cosmic Explorer, enabling improved constraints on formation channel ratios and the critical question of BH spin-axis tossing.
title Analysis and simulations of binary black hole merger spins -- the question of spin-axis tossing at black hole formation
topic High Energy Astrophysical Phenomena
Solar and Stellar Astrophysics
url https://arxiv.org/abs/2508.03809