Charactering instrumental noises and stochastic gravitational wave signals from combined time-delay interferometry

TL;DR

This paper explores methods to characterize instrumental noises in LISA's TDI data streams, enabling better detection and analysis of stochastic gravitational wave signals by combining different TDI configurations.

Contribution

It introduces a combined approach using first-generation TDI channels to effectively characterize and reconstruct instrumental noises and stochastic GW signals.

Findings

Effective noise characterization in lower frequency band

Successful noise spectrum reconstruction from TDI data

Parameter estimation for modeled stochastic signals

Abstract

LISA will detect gravitational waves (GWs) in the milli-Hz frequency band in space. Time-delay interferometry (TDI) is developed to suppress laser frequency noise beneath the acceleration noise and optical metrology noise. To identify stochastic GW signals, it would be required to characterize these noise components entangled in TDI data streams. In this work, we investigate noises characterization by combining the first-generation TDI channels from Michelson and Relay configurations. The Michelson channels are helpful to characterize acceleration noises in the lower frequency band, and the Relay configuration could effectively resolve optical path noises in the higher frequencies. Synergy could be achieved from their combination to determine these instrumental noises. Based on the characterized noises, we further reconstruct the power spectrum of noise in the selected TDI channel. Two cases are performed to characterize the spectrum shape of a stochastic GW signal. For a modeled signal, its parameter(s) could be directly estimated from the TDI data, and its spectrum could be recovered from the inferred values. And for an unexpected signal, its spectrum may be recognized and retrieved from noise-subtracted residual in which its power spectral density surpasses the noise level.