Identifying Monochromatic Signals in LISA and Taiji via Spectral Split: Gravitational Waves versus Ultralight Dark Matter

TL;DR

This paper proposes a method to distinguish monochromatic signals from gravitational waves and ultralight dark matter in space-based detectors by analyzing spectral splits caused by detector motion, enabling better identification of dark matter signals.

Contribution

It introduces a spectral split analysis technique based on detector motion to differentiate GW signals from ULDM in space-based interferometers like LISA and Taiji.

Findings

Spectral split caused by detector motion can distinguish GWs from ULDM signals.

High-precision parameter inference is possible using Fisher matrix analysis.

The method enhances the scientific capabilities of future space-based GW detectors.

Abstract

The detection of gravitational waves (GWs) has opened a new window to explore the dark Universe. Ultralight dark matter (ULDM), an attractive candidate for dark matter, might induce monochromatic signals in gravitational-wave (GW) laser interferometers. However it is not clear how such signals are disentangled from the GWs emitted by galactic compact binaries. Here we initiate the investigation on the spectral split of monochromatic signals caused by detector's heliocentric motion in space and show the annual modulation can induce distinct structures in the spectral harmonics for GWs and ULDM, which would enable to clearly identify the nature of the signal. We show the physical parameters can be inferred with high precision using the Fisher matrix formalism. Our results provide a practical algorithm for probing ULDM and broaden the scientific objectives of future GW detectors in space, such as LISA and Taiji.