2025/06/23 by Ali, Saif, Kesden, Michael, King, Lindsay
#FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc) #High Energy Astrophysical Phenomena (astro-ph.HE) #High Energy Physics - Theory (hep-th)
paper · doi:10.48550/arxiv.2506.18750
Real astrophysical lenses typically lack axisymmetry, necessitating the study of gravitational-wave (GW) lensing by elliptical mass distributions to accurately assess detectability and waveform interpretation. We investigate strong lensing using the singular isothermal ellipsoid (SIE) model, which produces two or four images depending on the source's position relative to lens caustics. Employing a quasi-geometrical optics framework, we determine that the geometrical-optics approximation holds reliably for lens masses above approximately 105 M_\odot at GW frequencies relevant for ground-based detectors (∼ 102 Hz), though wave-optics effects become significant for lower masses or sources near caustics. Our waveform mismatch analysis demonstrates that the use of three-image templates significantly improves our ability to distinguish source signals, reducing mismatches from O(10-1) to O(10-2), typically by factors between 1.5 and 5 compared to the standard two-image template model. At lens masses above 107 M_\odot, diffraction effects become negligible for ground-based detectors, resulting in an additional mismatch reduction by a factor of approximately three. These findings highlight the critical need for multi-image templates in GW searches to enhance detection efficiency and accuracy.