Establishing a universal relation between gravitational waves and black hole lensing

Understand

Black hole lensing and gravitational waves are, respectively, closely dependent of the property of the lens and radiation source.

• In this letter, a universal relation between them is established for a rotating black hole acting simultaneously as a lens and a gravitational wave source, in an asymptotically flat spacetime.
• The relation only relies on the lens geometry and observable, while is independent of the specific nature of the black hole.
• Therefore, the possible gravitational wave sources could be located with modern astronomical instrument from the side of the lensing without knowing the specific nature of the black hole lens.