Time-frequency Imprints of Extreme Mass-Ratio Inspirals in Confusion Gravitational Wave Background

TL;DR

This paper proposes a novel time-frequency spectrum method to analyze extreme-mass-ratio inspirals (EMRIs) in gravitational wave backgrounds, enabling population parameter estimation without detailed waveform templates.

Contribution

It introduces an analytical approach to use time-frequency spectra for EMRI detection and population analysis, offering an alternative to matched-filtering techniques.

Findings

Method can distinguish EMRIs from white dwarf binaries

Population parameters can be estimated with several percent accuracy

Effective even when EMRI signals are weaker than white dwarf background

Abstract

Detecting individual extreme-mass-ratio inspirals (EMRIs) is a major science goal of future space-based gravitational wave observatories such as Laser Interferometer Space Antenna (LISA) and TianQin. However, matched-filtering can be challenging as waveform templates are required to be accurate over tens of thousands of orbits. We introduce the time-frequency spectrum as an alternative observable that can be exploited to reveal the chirping of EMRIs at the population level. We analytically calculate this spectrum and its correlators for parameterized populations of slowly chirping sources on quasi-circular orbits, assuming a simplified model of the antenna response for a proof of concept. We then exploit this observable to distinguish between Galactic white dwarf binaries and a possible EMRI population, and quantify the precision at which EMRI population parameters can be determined through a Fisher analysis. We explore several scenarios of EMRI populations and find that this new method may allow us to determine EMRI population parameters at an accuracy level of several percent. Since white dwarf binaries have much longer chirping timescales than the EMRIs do, EMRI population properties can still be determined even if their stochastic gravitational wave background has a power spectrum two orders of magnitude weaker than that of the Galactic white dwarf binaries.