Strong-gravity precession resonances for binary systems orbiting a Schwarzschild black hole

Binary systems of compact objects in close orbit around a supermassive black hole (SMBH) may form in galactic nuclei, providing a unique environment to probe strong-gravity tidal effects on the binary’s dynamics. In this work, we investigate precession resonances arising between the periastron precession frequency of a binary system and its orbital frequencies around the SMBH. By modeling the SMBH as a Schwarzschild black hole, we find that relativistic effects in the tidal field give rise to a significantly richer resonance spectrum compared to the Newtonian case. This result is supported by both perturbative and numerical analyses of the quadrupolar tidal interaction in the strong-gravity regime. Our results reveal new signatures for strong-gravity effects in such triple systems, with potential implications for gravitational-wave astronomy.