{
  "abstract": "We analyze the mass-ratio and effective-spin ($χ_{\\rm eff}$) distributions of binary black hole mergers in the latest gravitational-wave catalog, GWTC-5, as a function of primary mass. Using hierarchical Bayesian inference with flexible Gaussian-process population models, we identify four distinct mass regions separated by sharp transitions in both mass-ratio and spin properties. Below $\\sim15~M_{\\odot}$, the population strongly favors equal-mass binaries and exhibits a narrow $χ_{\\rm eff}$ distribution peaked at positive values. In the range $18$-$30\\,M_{\\odot}$, the mass-ratio distribution becomes substantially flatter, while the $χ_{\\rm eff}$ distribution broadens, shifts to a peak consistent with zero, and shows tentative--but not statistically required--evidence for positive skewness. The region associated with the feature near $\\simeq35~M_{\\odot}$ returns to a narrow $χ_{\\rm eff}$ distribution consistent with symmetry at zero and strongly favors equal-mass binaries. Above $\\simeq 45~M_{\\odot}$, both the mass-ratio and $χ_{\\rm eff}$ distributions broaden significantly. The inferred support of the spin distribution converges toward the range expected for binaries containing remnants of previous black hole mergers, making the highest-mass region fully consistent with a star cluster population of hierarchical mergers. The close correspondence between transitions in mass ratio and effective spin suggests that different primary-mass ranges trace distinct formation channels, with isolated binary or triple evolution likely dominating the lower-mass population and dynamical assembly becoming increasingly important at higher masses.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2606.14472",
  "author_total": 7,
  "authors": [
    {
      "name": "Elizabeth Flanagan"
    },
    {
      "name": "Fabio Antonini"
    },
    {
      "name": "Thomas Callister"
    },
    {
      "name": "Debatri Chattopadhyay"
    },
    {
      "name": "Fani Dosopoulou"
    },
    {
      "name": "Isobel Romero-Shaw"
    },
    {
      "name": "Jakob Stegmann"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/6e8v18g6a4ajc.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2606.14472",
  "fulltext_url": null,
  "id": "6e8v18g6a4ajc",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2606.14472",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "openalex",
      "3103|Pulsars and Gravitational Waves Research"
    ]
  ],
  "openalex": "W7164838662",
  "pdf_url": "https://arxiv.org/pdf/2606.14472",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-07",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/6e8v18g6a4ajc.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:27:37Z",
      "native_id": "2606.14472",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2606.14472"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Transitions in the Mass-ratio and Spin Properties of Binary Black Holes in GWTC-5",
  "title_text": "Transitions in the Mass-ratio and Spin Properties of Binary Black Holes in GWTC-5",
  "type": "preprint",
  "updated_at": "2026-10-30T12:27:37Z",
  "url": "https://research.draconitic.com/paper/6e8v18g6a4ajc",
  "venue": "arXiv",
  "versions": []
}