Orbital eccentricity can make neutron star g-mode resonances observable with current gravitational-wave detectors

TL;DR

This paper shows that neutron star g-mode resonances, usually hard to detect, become observable with current gravitational-wave detectors when binary neutron stars have moderate eccentricities, due to enhanced phase shifts from higher harmonics and resonances.

Contribution

It introduces the idea that orbital eccentricity significantly boosts the detectability of neutron star g-mode tides in gravitational-wave signals, enabling constraints on NS matter properties.

Findings

Detectability of g-mode tides increases by over an order of magnitude for eccentricities 0.2-0.4.

Eccentric harmonics and epicyclic resonances amplify phase shifts in GW signals.

Current detectors can constrain g-mode properties with eccentric binary neutron stars.

Abstract

Dynamical tides can provide us vital information about the properties of neutron star (NS) matter. This is particularly true for g-modes, whose frequency and tidal coupling are highly sensitive to the composition of NSs, especially in their centers, where microphysical models are the least reliable. However, due to their weak coupling to external tidal fields, their effect on the gravitational-wave (GW) signal of binary inspirals can be difficult to observe. Here we show that the detectability of these tides can be significantly enhanced by binary NSs with moderate eccentricities. This is primarily due to higher eccentric harmonics in the early phase of the binary evolution experiencing larger phase shifts, which they transport to the sensitive band of GW detectors. In addition, g-mode tides in eccentric binaries undergo several epicyclic resonances, which also amplify the total phase shift. We demonstrate that these effects increase the detectability of g-mode dynamical tides by more than an order of magnitude for eccentricities of $e_\mathrm{10Hz}\sim0.2-0.4$, making it possible to put robust constraints on g-mode properties using current GW detectors, while all relevant models could potentially be constrained with eccentric binary NSs with Einstein Telescope.