GWTC-4.0: Updating the Gravitational-wave Transient Catalog with Observations from the First Part of the Fourth LIGO–Virgo–KAGRA Observing Run
Adrian Abac, I. Abouelfettouh, F. Acernese, K. Ackley, Christian Adamcewicz, S. Adhicary et al. · 2026 · 84 citationsRead the paper
Abstract Version 4.0 of the Gravitational-Wave Transient Catalog (GWTC-4.0) adds new candidates detected by the LIGO, Virgo, and KAGRA observatories through the first part of the fourth observing run (O4a: 2023 May 24 15:00:00 to 2024 January 16 16:00:00 UTC) and a preceding engineering run. In these new data, we find 128 compact binary coalescence candidates that are identified by at least one of our search algorithms with a probability of astrophysical origin p astro ≥ 0.5 and that are not vetoed during event validation. We also provide detailed source property measurements for 86 of these that have a false-alarm rate <1 yr −1 . Based on the inferred component masses, these candidates are consistent with signals from binary black holes (BBHs) and neutron star–black hole binaries (GW230518_125908 and GW230529_181500). Median-inferred component masses of BBHs in the catalog now range from 5.79M⊙ (GW230627_015337) to 137 M ⊙ (GW231123_135430), while GW231123_135430 was probably produced by the most massive binary observed in the catalog. For the first time, we have discovered BBH signals with network signal-to-noise ratio exceeding 30, GW230814_230901 and GW231226_101520, enabling high-fidelity studies of the waveforms and astrophysical properties of these systems. Combined with the 90 candidates included in GWTC-3.0, the catalog now contains 218 candidates with p astro ≥ 0.5 and not otherwise vetoed, more than doubling the size of the catalog and further opening our view of the gravitational-wave Universe.
What the full text shows
Deployed in practice- Total number of compact binary coalescence (CBC) candidates with p_astro ≥ 0.5 in the cumulative catalog — 218 candidates (Cumulative catalog including GWTC-3.0 and O4a data)
- New CBC candidates identified during O4a and preceding engineering run — 128 candidates (p_astro ≥ 0.5 and not vetoed)
- Highest network signal-to-noise ratio (SNR) detected to date (GW230814_230901) — 42.1 SNR (O4a data)
- Most massive binary black hole (BBH) observed (GW231123_135430) — Total mass M = 236 +29/-48 M⊙ (O4a data)
- Range of median-inferred component masses for BBHs in the catalog — 5.79 M⊙ to 137 M⊙ (GWTC-4.0)
- Evidence for missing signal content in CBC models — no strong evidence (Comparison of 23 candidates using BAYESWAVE, CWB-2G, and CWB-BBH pipelines)
- Setup
- Data collected from LIGO Hanford (LHO) and LIGO Livingston (LLO) from 2023 May 24 to 2024 January 16 (O4a), plus a 5-day engineering run.
- How
- The study identifies CBC candidates using four search pipelines and validates them via p_astro and vetoes. Source properties for high-purity events (FAR < 1 yr⁻¹) are estimated using waveform models and minimally modeled reconstruction methods (BAYESWAVE, CWB-2G, CWB-BBH) to test for model systematic errors.
- Limitations
- KAGRA data was excluded from the main analysis due to substantially lower sensitivity than LHO and LLO · Minimally modeled reconstruction pipelines show some level of bias in p-value assessment · Some candidates (e.g., GW231123_135430) show significant systematic differences in inferred mass and spin depending on the waveform model
Summarized by Gemma 4 from the open-access full text · 13 Oct 2026. Read it