Speaker
Description
Just like light, gravitational waves may be gravitationally lensed by massive objects along their travel path, however, this has not been observed so far. GW231123 is the most massive binary black-hole merger observed to-date, and standard analyses infer uncommon source properties that are unusually sensitive to the waveform model used. Here we investigate whether gravitational lensing can account for these features. We model the signal as a superposition of multiple overlapping images of the same merger and find support for lensing across four waveform models. The lensing interpretation reduces the support for unusually high spins, bringing both the inferred spins and masses into closer agreement across waveform models. A comparison with a background of unlensed signals gives the lensing interpretation an estimated significance of $3.96^{+0.68}_{-0.30} \sigma$. This makes lensing the most compelling interpretation of this event to-date.