Gravity Seminar: Exploring the Impact of Wave Effects in the Lensing of Gravitational Waves from Chirping Binaries, Anuj Mishra, Inter-University Centre for Astronomy & Astrophysics, Pune, India

With increasing sensitivities of the current ground-based gravitational wave (GW) detectors, the prospects of detecting a gravitationally lensed GW signal are going to improve in the coming years. Although the lensing of GWs shares similarities with that of electromagnetic waves, their observed effects can exhibit striking differences. When a GW encounters compact objects, such as stars and stellar remnants, there is a possibility of the emergence of wave-optics effects, leading to frequency-dependent modulations of the signal, which we refer to as `microlensing’. In such cases, the geometrical optics approximation breaks down, necessitating the consideration of the wave nature of propagation. Consequently, these frequency-dependent modulations affect the GW strain, which can introduce biases in the inferred parameters if these lensing effects are not accounted for.

In this talk, I will discuss broad aspects of the potential impact of microlensing on GWs. I will first explain why understanding microlensing effects is important, addressing how they can bias fundamental tests using GWs, such as tests of GR. Moreover, I will explore the interplay between microlensing and eccentricity, demonstrating how the presence of eccentricity can bias microlensing searches. Lastly, I will discuss the challenging problem of modeling microlensed waveforms for more complex microlensing scenarios beyond the isolated point-mass lens model.