Mick Wright, "Results from the GWTC-4.0 Searches for Gravitationally Lensed Gravitational Wave Signals"

Abstract: Gravitational waves may experience a number of astrophysical phenomena on their path from emission to observation by the current ground-based gravitational wave detector network operated by the LIGO--Virgo--KAGRA (LVK) Scientific Collaborations. One of these phenomena is deflection due to the signal passing through the space-time distortions of massive objects and being deflected in a process qualitatively similar to the lensing of light through a lens. Gravitational lensing has been an important probe of dark matter through electromagnetic observations, and observation in gravitational wave signals may be similarly used, or used to constrain cosmological parameters, perform tests of General Relativity, and for other important scientific applications. This seminar will present the means by which gravitational wave signals are examined by the LVK for signatures of lensing from a broad variety of possible lensing scenarios and present the results from these searches applied to the latest catalog of gravitational wave events (GWTC-4.0). We will in particular discuss the event GW231123 which had the highest support for lensing of any event observed thus far and the difficulties in reaching a definitive conclusion for this event.