{
  "abstract": "The observation of orbital eccentricity in compact binary coalescences would provide a direct signature of dynamical formation environments. Previous matched-filter searches for eccentric neutron star-black hole (NSBH) binaries have been severely limited by computational constraints, necessitating the use of simplified waveform models that capture secular dephasing but omit apsidal precession and inter-orbit harmonics. Including these physical features increases the sensitive search volume for systems with $0.2 \\le e_{20} \\le 0.28$ by $\\sim 25\\%$ to $30\\%$. We present a rapid matched-filter search methodology that makes the direct use of time-domain effective-one-body waveforms computationally feasible. By multibanding and high-frequency ratio-filtering, our pipeline achieves a $\\sim 20\\times$ reduction in computational cost. This allows a bank of 88.6 million effective-one-body templates, fifteen times larger than prior eccentric analyses, to search O4a and O4b Advanced LIGO data. We recover the known low-mass mergers GW230518_125908 and GW230529_181500 with parameters consistent with zero eccentricity. Finding no new gravitational-wave events with orbital eccentricity ($e_{20} \\ge 0.05$), we place $90\\%$ credible upper limits on the local merger rate density of eccentric NSBH systems across the search space of $\\mathcal{R}_{90\\%} \\le 7.5\\text{-}57\\ \\mathrm{Gpc}^{-3}\\ \\mathrm{yr}^{-1}$, up to a factor of $\\sim 4$ improvement over previous observational bounds. At the parameters of GW200105_162426, this non-detection establishes an upper limit of $\\mathcal{R}_{90\\%} \\le 12.1\\ \\mathrm{Gpc}^{-3}\\ \\mathrm{yr}^{-1}$. Alternatively, if GW200105_162426 is treated as an eccentric detection, the lack of subsequent detections in O4 updates the inferred local merger rate density of this population to $\\mathcal{R} = 6.6^{+6.3}_{-3.8}\\ \\mathrm{Gpc}^{-3}\\ \\mathrm{yr}^{-1}$.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.37997",
  "author_total": 4,
  "authors": [
    {
      "name": "Aleyna Akyüz"
    },
    {
      "name": "Keisi Kacanja"
    },
    {
      "name": "Rahul Dhurkunde"
    },
    {
      "name": "Alexander H. Nitz"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/a4rpffkprwq0k.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.37997",
  "fulltext_url": null,
  "id": "a4rpffkprwq0k",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.37997",
  "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"
    ],
    [
      "arxiv",
      "gr-qc"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.37997",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-27",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/a4rpffkprwq0k.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:23Z",
      "native_id": "2610.37997",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.37997"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "physics",
      "origin": "arxiv:gr-qc",
      "subfield": "gravitation"
    }
  ],
  "title": "Search for Eccentric Neutron Star-Black Hole Binaries in Advanced LIGO's Fourth Observing Run using Effective-One-Body Waveforms",
  "title_text": "Search for Eccentric Neutron Star-Black Hole Binaries in Advanced LIGO's Fourth Observing Run using Effective-One-Body Waveforms",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:44Z",
  "url": "https://research.draconitic.com/paper/a4rpffkprwq0k",
  "venue": "arXiv",
  "versions": []
}