Speaker
Description
Tidal interactions play a fundamental role in shaping binary systems and affect their gravitational-wave (GW) signals, which is crucial for future detectors such as LISA and ET. While tidal effects on binaries are often studied in a weak-field approximation, a fully relativistic description is needed to capture the role of spin and curvature in shaping orbital dynamics and GW emission.
In this work, we present the first explicit metric for a tidally deformed Kerr black hole, valid up to generic quadrupolar tidal deformations. Expressed in terms of electric and magnetic tidal moments, our construction applies to any external vacuum perturbation in the small-tide approximation. The metric is obtained via reconstruction techniques based on the Teukolsky Master Equation and incorporates spin–tidal couplings, providing a relativistic framework to quantify environmental effects around black-hole spacetimes.
Using this solution, we analyze the secular dynamics of a test particle orbiting the tidally deformed Kerr black hole, focusing on the innermost stable circular orbit (ISCO) and the light ring (LR). We compute tidal-induced shifts in their location and frequencies, and show how these are affected by the black hole’s spin.
These effects accumulate over the long inspiral of EMRIs, leading to measurable phase shifts in the GW signal, while also impacting black-hole spin inference and the quasinormal-mode spectrum. Our findings open new observational pathways for detecting environmental effects in strong gravity, offering potential smoking-gun signatures for LISA and other future detectors.
