Improved reconstruction of a stochastic gravitational wave background with LISA

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.

Automated summary

A data analysis methodology was proposed for model-independent reconstruction of the spectral shape of a stochastic gravitational wave background with LISA; The improved algorithm includes a complete set of TDI channels, reducing uncertainties, avoiding local extrema in likelihood maximization, and breaking degeneracies between signal and instrumental noise; Testing with case studies showed that additional channels are helpful in various ways for the reconstruction process.