Strong gravitational lensing of gravitational waves in Einstein Telescope

Abstract

Gravitational wave experiments have entered a newstage which gets us closer to the opening a new observational window on theUniverse. In particular, the Einstein Telescope (ET) is designed to have a fantastic sensitivity thatwill provide with tens or hundreds of thousand NS-NS inspiral events per year up to the redshift z = 2.Some of such events should be gravitationally lensed by intervening galaxies.We explore the prospects of observing gravitationally lensed inspiral NS-NS eventsin the Einstein telescope. Being conservative we consider the lens population of ellipticalgalaxies. It turns out that depending on the local insipral rate ET should detect from one per decadedetection in the pessimistic case to a tens of detections per year for the most optimistic case.The detection of gravitationally lensed source in gravitational wave detectors would be an invaluablesource of information concerning cosmography, complementary to standard ones (like supernovae or BAO) independent ofthe local cosmic distance ladder calibrations.