Dynamical Tides in General Relativity: Effective Action and Effective-One-Body Hamiltonian

TL;DR

This paper develops an effective action and Hamiltonian framework to incorporate dynamical tidal effects, especially resonances with neutron star oscillation modes, into models of compact binary inspirals in general relativity, improving gravitational wave predictions.

Contribution

It introduces a novel effective-one-body Hamiltonian that includes dynamical quadrupolar degrees of freedom to model neutron star tides beyond the adiabatic approximation.

Findings

Dynamical tides significantly enhance matter effects in neutron star inspirals.

The model extends tidal descriptions throughout the entire inspiral phase.

Including dynamical tides improves the accuracy of gravitational-wave data analysis.

Abstract

Tidal effects have an important impact on the late inspiral of compact binary systems containing neutron stars. Most current models of tidal deformations of neutron stars assume that the tidal bulge is directly related to the tidal field generated by the companion, with a constant response coefficient. However, if the orbital motion approaches a resonance with one of the internal modes of the neutron star, this adiabatic description of tidal effects starts to break down, and the tides become dynamical. In this paper, we consider dynamical tides in general relativity due to the quadrupolar fundamental oscillation mode of a neutron star. We devise a description of the effects of the neutron star's finite size on the orbital dynamics based on an effective point-particle action augmented by dynamical quadrupolar degrees of freedom. We analyze the post-Newtonian and test-particle approximations of this model and incorporate the results into an effective-one-body Hamiltonian. This enables us to extend the description of dynamical tides over the entire inspiral. We demonstrate that dynamical tides give a significant enhancement of matter effects compared to adiabatic tides, at least for neutron stars with large radii and for low mass-ratio systems, and should therefore be included in accurate models for gravitational-wave data analysis.