GW231123: A Binary Black Hole Merger with Total Mass 190–265 M⊙
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Abac, A. G., I. Abouelfettouh, F. Acernese, et al. “GW231123: A Binary Black Hole Merger with Total Mass 190–265 M⊙” The Astrophysical Journal Letters 993, no. 1 (2025): L25. https://doi.org/10.3847/2041-8213/ae0c9c.
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This work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.
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Abstract
On 2023 November 23, the two LIGO observatories both detected GW231123, a gravitational-wave signal consistent with the merger of two black holes with masses 137⁺²³₋₁₈M⊙ and 101⁺²²₋₅₀M⊙(90% credible intervals), at a luminosity distance of 0.7–4.1 Gpc, a redshift of 0.40⁺⁰˙²⁷₋₀.₂₅, and with a network signal-to-noise ratio of ∼20.7. Both black holes exhibit high spins— 0.90⁺⁰˙¹⁰₋₀.₁₉and 0.80⁺⁰˙²⁰₋₀.₅₂, respectively. A massive black hole remnant is supported by an independent ringdown analysis. Some properties of GW231123 are subject to large systematic uncertainties, as indicated by differences in the inferred parameters between signal models. The primary black hole lies within or above the theorized mass gap where black holes between 60–130 M⊙ should be rare, due to pair-instability mechanisms, while the secondary spans the gap. The observation of GW231123 therefore suggests the formation of black holes from channels beyond standard stellar collapse and that intermediate-mass black holes of mass ∼200M⊙ form through gravitational-wave-driven mergers.