Gravitational lensing signatures in gravitational waves from binary black hole mergers

Abstract

The growing network of gravitational-wave (GW) detectors is expected to probe more exotic astrophysical phenomena in the coming years, including the observation of gravitationally lensed GWs. Similar to light, the trajectory of a GW may curve when propagating near massive astrophysical objects causing gravitational lensing and detection of multiple images with varied amplitudes. In this work, we study the gravitational lensing signatures of GWs in a lens system composed of a galaxy modeled as a singular isothermal ellipsoid (SIE) with an embedded point mass lens (PML). We analyze the beating patterns in the lensed waveforms and show that for the configurations considered, the combined effect of strong lensing by the SIE and microlensing by the PML translates to an effective PML mass, i.e., the mass if it were in the pure microlensing scenario, which is 2 to 3 orders of magnitude larger than the actual PML mass. In future work, the analysis can be extended to a suite of lens systems to study effects of galaxy mass, PML mass, and configurations on the combined lensing signatures.