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  • Letter
  • Open Access

GW231123: Binary black hole merger or cosmic string?

Iuliu Cuceu1,*, Marie Anne Bizouard1,†, Nelson Christensen1,‡, and Mairi Sakellariadou2,1,§

  • *Contact author: icuceu@oca.eu
  • †Contact author: marieanne.bizouard@oca.eu
  • ‡Contact author: nelson.christensen@oca.eu
  • §Contact author: mairi.sakellariadou@kcl.ac.uk
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Phys. Rev. D 113, L021302 – Published 20 January, 2026

DOI: https://doi.org/10.1103/zd8m-tzxd

Abstract

The LIGO-Virgo-KAGRA collaboration recently reported an exceptional gravitational-wave event, GW231123. This gravitational-wave signal was assumed to be generated from the merger of a binary black hole system, with source frame masses of 137−17+22M⊙ and 103−52+20M⊙ (90% credible intervals). As seen by the two LIGO detectors, the signal has only ∼5 cycles, between 30 and 80 Hz, over ∼10  ms. It is of critical importance to confirm the origin of this signal. Here we present the results of a Bayesian model comparison to test whether the gravitational-wave signal was actually generated by a binary black hole merger, or emitted from cusps or kinks on a cosmic string. We find significant evidence for a binary black hole merger origin versus a cosmic string origin of the signal.

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Phys. Rev. D 113, L021302– Published 20 January, 2026
  • Received 29 July 2025
  • Accepted 22 December 2025
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