Gravitational lensing has been extensively observed for electromagnetic
signals, but not yet for gravitational waves (GWs). Detecting lensed GWs will
have many astrophysical and cosmological applications, and becomes more
feasible as the sensitivity of the LIGO-Virgo-KAGRA detectors improves. One of
the missing ingredients to robustly identify lensed GWs is to ensure that the
statistical tests used are robust under the choice of underlying waveform
models. We present the first systematic study of possible waveform systematics
in identifying candidates for strongly lensed GW event pairs, focusing on the
posterior overlap method. To this end, we compare Bayes factors from all
posteriors using different waveforms included in GWTC data releases from the
first three observing runs (O1-O3). We find that waveform choice yields a wide
spread of Bayes factors in some cases. However, it is likely that no event
pairs from O1 to O3 were missed due to waveform choice. We also perform
parameter estimation with additional waveforms for interesting cases, to
understand the observed differences. We also briefly explore if computing the
overlap from different runs for the same event can be a useful metric for
waveform systematics or sampler issues, independent of the lensing scenario.Comment: 29 pages, 5 figures, comments welcom