Probing the efficiency of tidal synchronization in outspiralling double white dwarf binaries with LISA

TL;DR

This paper investigates how LISA can use gravitational-wave observations of double white dwarf binaries to understand tidal interactions and the behavior of electron-degenerate matter through population analysis.

Contribution

It introduces a method to infer tidal synchronization timescales in DWD systems using hierarchical Bayesian analysis of LISA data.

Findings

Tidal coupling influences the distribution of GW frequencies in DWDs.

LISA can constrain the strength of tidal interactions through population measurements.

The study links GW observations to the physics of electron-degenerate matter.

Abstract

Compact-object binaries including a white dwarf component are unique among gravitational-wave sources because their evolution is governed not just by general relativity and tides, but also by mass transfer. While the black hole and neutron star binaries observed with ground-based gravitational-wave detectors are driven to inspiral due to the emission of gravitational radiation--manifesting as a "chirp-like" gravitational-wave signal--the astrophysical processes at work in double white dwarf (DWD) systems can cause the inspiral to stall and even reverse into an outspiral. The dynamics of the DWD outspiral thus encode information about tides, which tell us about the behaviour of electron-degenerate matter. We carry out a population study to determine the effect of the strength of tides on the distributions of the DWD binary parameters that the Laser Interferometer Space Antenna (LISA) will be able to constrain. We find that the strength of tidal coupling parameterized via the tidal synchronization timescale at the onset of mass transfer affects the distribution of gravitational-wave frequencies and frequency derivatives for detectably mass-transferring DWD systems. Using a hierarchical Bayesian framework informed by binary population synthesis simulations, we demonstrate how this parameter can be inferred using LISA observations. By measuring the population properties of DWDs, LISA will be able to probe the behavior of electron-degenerate matter.