GW231123: Binary black hole merger or cosmic string?

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 + 22 M ⊙ and 103 − 52 + 20 M ⊙ (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.