Observable signature of magnetic tidal coupling in hierarchical triple systems

TL;DR

This paper investigates how magnetic tidal interactions in hierarchical triple systems involving a compact binary and a supermassive black hole can cause new resonances, alter orbital evolution, and produce observable gravitational wave signatures.

Contribution

It introduces the role of quadrupolar magnetic tidal moments at 0.5 post-Newtonian order, revealing new resonances and their effects on binary dynamics near SMBHs.

Findings

Magnetic tides create new resonances absent at lower order.

Resonances lead to increased eccentricity and faster mergers.

Distinct gravitational wave signatures could be observed by LISA.

Abstract

We study hierarchical triple systems formed by a compact binary orbiting a supermassive black hole (SMBH), focusing on the role of relativistic magnetic tidal interactions. Extending previous analyses of precession resonances to 0.5 post-Newtonian order, we incorporate quadrupolar magnetic tidal moments, which have no Newtonian counterpart. We find that magnetic tides introduce new resonances absent at lower order, leading to additional eccentricity excitations and significantly modifying the binary's long-term evolution. Numerical solutions of the Lagrange Planetary Equations confirm these analytical predictions and reveal how resonance strength depends on orbital eccentricity and inclination. The resulting dynamics accelerates the binary merger and imprints distinctive signatures on gravitational waves, potentially observable by LISA. Our findings identify magnetic tidal coupling as a novel strong-gravity effect and establish its importance for the resonant dynamics of compact-object binaries near SMBHs.