Search for Eccentric Neutron Star-Black Hole Binaries in Advanced LIGO's Fourth Observing Run using Effective-One-Body Waveforms
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 ≤ e20 ≤ 0.28 by ∼ 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 ∼ 20× 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 (e20 ≥ 0.05), we place 90% credible upper limits on the local merger rate density of eccentric NSBH systems across the search space of ℛ90% ≤ 7.5−57 Gpc−3 yr−1, up to a factor of ∼ 4 improvement over previous observational bounds. At the parameters of GW200105_162426, this non-detection establishes an upper limit of ℛ90% ≤ 12.1 Gpc−3 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 ℛ = 6.6+6.3−3.8 Gpc−3 yr−1.
Related
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BibTeX
@misc{akyuz2026search,
title = {{Search for Eccentric Neutron Star-Black Hole Binaries in Advanced LIGO's Fourth Observing Run using Effective-One-Body Waveforms}},
author = {Aleyna Akyüz and Keisi Kacanja and Rahul Dhurkunde and Alexander H. Nitz},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.37997},
eprint = {2610.37997},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.37997},
}
RIS
TY - UNPB
TI - Search for Eccentric Neutron Star-Black Hole Binaries in Advanced LIGO's Fourth Observing Run using Effective-One-Body Waveforms
AU - Aleyna Akyüz
AU - Keisi Kacanja
AU - Rahul Dhurkunde
AU - Alexander H. Nitz
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2610.37997
UR - https://arxiv.org/abs/2610.37997
AB - 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 ≤ e_20 ≤ 0.28 by ∼ 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 ∼ 20× 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 ≥ 0.05), we place 90% credible upper limits on the local merger rate density of eccentric NSBH systems across the search space of ℛ_90% ≤ 7.5−57 Gpc^−3 yr^−1, up to a factor of ∼ 4 improvement over previous observational bounds. At the parameters of GW200105_162426, this non-detection establishes an upper limit of ℛ_90% ≤ 12.1 Gpc^−3 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 ℛ = 6.6^+6.3_−3.8 Gpc^−3 yr^−1.
ER -