GW231123: Overlapping Gravitational Wave Signals?
5 affiliations
- 1University of Glasgow
- 2Nikhef—National Institute for Subatomic Physics
- 3Utrecht University
- 4Université Catholique de Louvain
- 5Royal Observatory of Belgium
Abstract
The recently discovered gravitational wave event GW231123 was interpreted as the merger of two black holes with a total mass of 190–265 M ⊙ , making it the heaviest such merger detected to date. While much of the postdiscovery literature has focused on its astrophysical origins, primary analyses have exhibited considerable discrepancies in the measurement of source properties between waveform models, which cannot reliably be reproduced by simulations. Such discrepancies may arise when an unaccounted overlapping signal is present in the data, or from phenomena that produce similar effects, such as gravitational lensing or overlapping noise artifacts. In this work, we analyze GW231123 using a flexible model that allows for two overlapping signals, and find that it is favored over the isolated signal model with Bayes factors of ∼10 2 –10 4 , depending on the waveform model. These values lie within the top few percent of the background distribution. Similar effects are not observed in GW190521, another high-mass event. Under the overlapping signals model, discrepancies in the measurement of source properties between waveform models are largely mitigated. We also find that neglecting an additional signal in overlapping-signal data can lead to discrepancies in the estimated source properties resembling those reported in GW231123. Although the overlapping signal model provides a higher Bayesian evidence, the astrophysical prior probability of two short signals overlapping is low. However, we find that the two recovered sources show similar properties. This, taken with the higher evidence of the two signal model, suggests that gravitational lensing may provide an alternative explanation.
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BibTeX
@article{hu2026gw231123,
title = {{GW231123: Overlapping Gravitational Wave Signals?}},
author = {Qian Hu and Harsh Narola and Jef Heynen and M. Wright and John Veitch and Justin Janquart and Chris Van Den Broeck},
journal = {The Astrophysical Journal},
year = {2026},
month = may,
doi = {10.3847/1538-4357/ae6811},
url = {https://doi.org/10.3847/1538-4357/ae6811},
note = {CC BY},
}
RIS
TY - JOUR
TI - GW231123: Overlapping Gravitational Wave Signals?
AU - Qian Hu
AU - Harsh Narola
AU - Jef Heynen
AU - M. Wright
AU - John Veitch
AU - Justin Janquart
AU - Chris Van Den Broeck
PY - 2026
DA - 2026/05/26
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae6811
UR - https://doi.org/10.3847/1538-4357/ae6811
AB - The recently discovered gravitational wave event GW231123 was interpreted as the merger of two black holes with a total mass of 190–265 M ⊙ , making it the heaviest such merger detected to date. While much of the postdiscovery literature has focused on its astrophysical origins, primary analyses have exhibited considerable discrepancies in the measurement of source properties between waveform models, which cannot reliably be reproduced by simulations. Such discrepancies may arise when an unaccounted overlapping signal is present in the data, or from phenomena that produce similar effects, such as gravitational lensing or overlapping noise artifacts. In this work, we analyze GW231123 using a flexible model that allows for two overlapping signals, and find that it is favored over the isolated signal model with Bayes factors of ∼10 2 –10 4 , depending on the waveform model. These values lie within the top few percent of the background distribution. Similar effects are not observed in GW190521, another high-mass event. Under the overlapping signals model, discrepancies in the measurement of source properties between waveform models are largely mitigated. We also find that neglecting an additional signal in overlapping-signal data can lead to discrepancies in the estimated source properties resembling those reported in GW231123. Although the overlapping signal model provides a higher Bayesian evidence, the astrophysical prior probability of two short signals overlapping is low. However, we find that the two recovered sources show similar properties. This, taken with the higher evidence of the two signal model, suggests that gravitational lensing may provide an alternative explanation.
SN - 0004-637X
SN - 1538-4357
ER -