Speaker
Description
Mergers of compact binaries, such as black holes and neutron stars, emit gravitational waves (GWs) that can be detected by the LIGO–Virgo–KAGRA (LVK) Collaboration. As these waves travel cosmological distances, they may encounter massive astrophysical objects that act as lenses, bending their trajectories and distorting their signals. This effect, known as gravitational lensing of gravitational waves, has not yet been observed, but is expected to be within reach of current and upcoming detectors. Near caustics, lensing produces multiple highly magnified images whose signals can overlap in time, requiring accurate modeling beyond Geometrical Optics. In this poster, we present a framework to describe GW diffraction near fold caustics in binary lenses using the Uniform Approximation (UA). This approach avoids the high computational cost of full-wave methods while providing accurate, globally valid solutions. It has enabled us to characterize the caustic width, $d_c$, the scale over which diffraction significantly affects propagation. We find a universal scaling $d_c\sim \lambda^{2/3}$ and $d_c \sim M_{Lz}^{-2/3}$, and show that the amplification near the fold grows as $d_c^{-1/4}$. This enhanced magnification could substantially boost the detectability of lensed gravitational waves in the vicinity of caustics.
