Eccentricity in disguise? Insights from GW231123 and numerically simulated binary black hole merger signals
6 affiliations
- 1Max Planck Institute for Gravitational Physics (Albert Einstein Institute) , Am Mühlenberg 1, D-14476 Potsdam ,
- 2Institute for Gravitation & the Cosmos, Department of Physics, Penn State University , University Park, PA 16802 ,
- 3Indian Institute of Technology , Bombay, Mumbai-400076 ,
- 4Gran Sasso Science Institute (GSSI) , I-67100 L’Aquila ,
- 5INFN, Laboratori Nazionali del Gran Sasso , I-67100 Assergi ,
- 6School of Physics and Astronomy and Institute for Gravitational Wave Astronomy, University of Birmingham , Edgbaston, Birmingham B15 2TT ,
Abstract
GW231123 is a gravitational-wave signal originating from the merger of a black hole binary with total mass ∼ 250 M⊙ , the largest ever detected by the LIGO–Virgo–Kagra Collaboration. Remarkably, under standard priors, the system features among the fastest spinning binary components confidently measured in binary mergers, χ 1,2 ≳ 0.7 at 90 per cent one-dimensional credibility, according to the most accurate model employed. As typical binary mergers result in remnants with χ ∼ 0.7, such spin values are challenging to obtain even from previous (hierarchical) mergers. These inferred properties rely on waveform models lacking eccentric corrections in the merger-ringdown stage. Here, we show that binaries retaining significant eccentricity up to merger can be misinterpreted as near-extremally spinning when non-circular corrections are neglected. Binary-agnostic ringdown analysis instead provides unbiased estimates of the remnant properties, provided that a robust estimate of the signal peak can be obtained. We re-analyse GW231123 using available eccentric numerical-relativity catalogues, finding that although eccentric templates can provide a good fit to the data, quasi-spherical templates are still favoured. Ringdown analyses confirm a secondary likelihood peak correlated with large eccentricity values, but improved eccentric models will be required to assess the reliability of this interpretation. Finally, analysing GW231123 under population-informed parametric priors confirms the exceptional nature of this event within the current black hole binary population.
Versions
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BibTeX
@article{chandra2026eccentricity,
title = {{Eccentricity in disguise? Insights from GW231123 and numerically simulated binary black hole merger signals}},
author = {Koustav Chandra and Johann Fernandes and Akshita Mittal and Gregorio Carullo},
journal = {Monthly Notices of the Royal Astronomical Society},
year = {2026},
month = oct,
doi = {10.1093/mnras/stag1934},
url = {https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1934/8910744},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Eccentricity in disguise? Insights from GW231123 and numerically simulated binary black hole merger signals
AU - Koustav Chandra
AU - Johann Fernandes
AU - Akshita Mittal
AU - Gregorio Carullo
PY - 2026
DA - 2026/10/12
JO - Monthly Notices of the Royal Astronomical Society
DO - 10.1093/mnras/stag1934
UR - https://academic.oup.com/mnras/article/doi/10.1093/mnras/stag1934/8910744
AB - GW231123 is a gravitational-wave signal originating from the merger of a black hole binary with total mass ∼ 250 M_⊙ , the largest ever detected by the LIGO–Virgo–Kagra Collaboration. Remarkably, under standard priors, the system features among the fastest spinning binary components confidently measured in binary mergers, χ _1,2 ≳ 0.7 at 90 per cent one-dimensional credibility, according to the most accurate model employed. As typical binary mergers result in remnants with χ ∼ 0.7, such spin values are challenging to obtain even from previous (hierarchical) mergers. These inferred properties rely on waveform models lacking eccentric corrections in the merger-ringdown stage. Here, we show that binaries retaining significant eccentricity up to merger can be misinterpreted as near-extremally spinning when non-circular corrections are neglected. Binary-agnostic ringdown analysis instead provides unbiased estimates of the remnant properties, provided that a robust estimate of the signal peak can be obtained. We re-analyse GW231123 using available eccentric numerical-relativity catalogues, finding that although eccentric templates can provide a good fit to the data, quasi-spherical templates are still favoured. Ringdown analyses confirm a secondary likelihood peak correlated with large eccentricity values, but improved eccentric models will be required to assess the reliability of this interpretation. Finally, analysing GW231123 under population-informed parametric priors confirms the exceptional nature of this event within the current black hole binary population.
SN - 0035-8711
SN - 1365-2966
ER -