Lensing of gravitational waves as a probe of compact dark matter

ABSTRACT We study gravitational lensing of gravitational waves from compact object binaries as a probe of compact dark matter (DM) objects such as primordial black holes. Assuming a point mass lens, we perform parameter estimation of lensed gravitational wave signals from compact object binaries to determine the detectability of the lens with ground based laser interferometers. Then, considering binary populations that LIGO-Virgo has been probing, we derive a constraint on the abundance of compact DM from non-observation of lensed events. We find that the LIGO-Virgo observations imply that compact objects heavier than Mₗ = 200\, M cannot constitute all DM and less than 40{\ per\ cent} of DM can be in compact objects heavier than Mₗ = 400\, M. We also show that the DM fraction in compact objects can be probed by LIGO in its final sensitivity for Mₗ 40\, M reaching 2{\ per\ cent} of the DM abundance at Mₗ 200\, M, and by ET for Mₗ 1\, M reaching DM fraction as low as 7 × 10−5 at Mₗ 40\, M.