Improved reconstruction of a stochastic gravitational wave background with LISA

TL;DR

This paper introduces an enhanced, model-independent method for reconstructing the spectral shape of a stochastic gravitational wave background with LISA, utilizing multiple TDI channels to improve accuracy and robustness.

Contribution

The paper extends previous algorithms by incorporating all TDI channels, significantly improving the reconstruction of the gravitational wave background's spectral shape.

Findings

Including all TDI channels reduces uncertainties in the reconstruction.

The improved method is more robust against local extrema in likelihood maximization.

Additional channels help break degeneracies between signals and noise.

Abstract

We present a data analysis methodology for a model-independent reconstruction of the spectral shape of a stochastic gravitational wave background with LISA. We improve a previously proposed reconstruction algorithm that relied on a single Time-Delay-Interferometry (TDI) channel by including a complete set of TDI channels. As in the earlier work, we assume an idealized equilateral configuration. We test the improved algorithm with a number of case studies, including reconstruction in the presence of two different astrophysical foreground signals. We find that including additional channels helps in different ways: it reduces the uncertainties on the reconstruction; it makes the global likelihood maximization less prone to falling into local extrema; and it efficiently breaks degeneracies between the signal and the instrumental noise.