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Main Authors: Kobayashi, Kazuya, Iwaya, Masaki, Morisaki, Soichiro, Hotokezaka, Kenta, Kinugawa, Tomoya
Format: Preprint
Published: 2026
Subjects:
Online Access:https://arxiv.org/abs/2602.12509
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author Kobayashi, Kazuya
Iwaya, Masaki
Morisaki, Soichiro
Hotokezaka, Kenta
Kinugawa, Tomoya
author_facet Kobayashi, Kazuya
Iwaya, Masaki
Morisaki, Soichiro
Hotokezaka, Kenta
Kinugawa, Tomoya
contents The spins of merging binary black holes (BBHs) inferred from gravitational-wave (GW) observations provide key insights into their formation channels. However, spin parameters are typically weakly constrained from data, and their inferred values are often strongly influenced by the assumed prior in Bayesian analyses. A commonly used prior, uniform in spin magnitudes and isotropic in spin directions, assigns vanishing probability density to spin-orbit-aligned configurations, potentially biasing inferences for BBH parameters. The prior choice can also affect population-level analyses by degrading the convergence of Monte Carlo integrations used to evaluate the likelihood in hierarchical Bayesian inference. In this work, we propose a novel spin prior that is uniform in the effective spin parameters Xeff and Xp, two spin combinations that can be relatively well measured from GW data, conditioned on the mass ratio. Using simulated BBH populations, we show that the inferred spin population can depend on the choice of prior, and that the proposed prior more accurately recovers the underlying spin population, particularly when the true distribution favors aligned-spin configurations. Because mass and spin measurements are correlated, our prior also enables a more accurate recovery of the underlying mass distribution.
format Preprint
id arxiv_https___arxiv_org_abs_2602_12509
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Impact of Spin Priors on the Population Inference of Merging Binary Black Holes
Kobayashi, Kazuya
Iwaya, Masaki
Morisaki, Soichiro
Hotokezaka, Kenta
Kinugawa, Tomoya
General Relativity and Quantum Cosmology
The spins of merging binary black holes (BBHs) inferred from gravitational-wave (GW) observations provide key insights into their formation channels. However, spin parameters are typically weakly constrained from data, and their inferred values are often strongly influenced by the assumed prior in Bayesian analyses. A commonly used prior, uniform in spin magnitudes and isotropic in spin directions, assigns vanishing probability density to spin-orbit-aligned configurations, potentially biasing inferences for BBH parameters. The prior choice can also affect population-level analyses by degrading the convergence of Monte Carlo integrations used to evaluate the likelihood in hierarchical Bayesian inference. In this work, we propose a novel spin prior that is uniform in the effective spin parameters Xeff and Xp, two spin combinations that can be relatively well measured from GW data, conditioned on the mass ratio. Using simulated BBH populations, we show that the inferred spin population can depend on the choice of prior, and that the proposed prior more accurately recovers the underlying spin population, particularly when the true distribution favors aligned-spin configurations. Because mass and spin measurements are correlated, our prior also enables a more accurate recovery of the underlying mass distribution.
title Impact of Spin Priors on the Population Inference of Merging Binary Black Holes
topic General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2602.12509