Microlensing of gravitational waves by dark matter structures

Abstract

Gravitational lensing of gravitational waves provides a potential new probe of dark matter structures. In this work, we consider the microlensing effect on gravitational wave signals from black hole binaries induced by low-mass dark matter halos that do not retain enough baryonic matter to hold stars. We clarify systematically when this microlensing effect is relevant and study in detail its detectability by future gravitational wave observatories. We consider lensing by cold dark matter halos and by solitonic cores that reside in fuzzy dark matter halos. Our results show that although the effect can be detectable at relatively large impact parameters, the probability of detecting such lensed events is low. In particular, we find that the expected number of events lensed by cold dark matter halos is 𝒪(0.01) per year for BBO and the expected number of events lensed by solitonic cores inside fuzzy dark matter halos is 𝒪(0.01) per year for ET. In the case that a significant fraction of dark matter consists of 𝒪(100 M ⊙) objects that are relatively compact, R < 𝒪(0.1 pc), we show that the expected number of lensed events per year for ET can be very large, 𝒪(1000).

Testing an exact diffraction formula with gravitational wave source lensed by a supermassive black hole in binary systems

“…It offers a unique opportunity to measure the propagation speed of GWs [10,11], constrain cosmological models [12], and shed light on the origins of stellar binary black holes (BHs) [13]. Furthermore, it provides a powerful tool to explore the nature of dark matter [14][15][16][17][18][19][20][21][22] and even the internal structure of the sun [23,24]. The potential applications of detecting GL of GWs are vast and promising, paving the way for exciting new discoveries in the field of gravitational physics.…”