The first year of LISA Galactic foreground

TL;DR

This paper analyzes the Galactic white-dwarf binary foreground during the first year of LISA observations, demonstrating effective modeling, robustness, and non-stationarity detection within a month of data.

Contribution

It introduces a global-fit characterization of the Galactic foreground using the bahamas code, accounting for statistical properties and testing robustness against extragalactic signals.

Findings

Consistent results across multiple approaches.

Evidence for a non-stationary Galactic foreground within a month.

Robustness against extragalactic foregrounds.

Abstract

Galactic white-dwarf binaries play a central role in the inference model for the Laser Interferometer Space Antenna. In this manuscript, we employ the $\texttt{bahamas}$ codebase to characterize, in a global-fit fashion, the reconstruction of the Galactic foreground during the first year of observation. To account for its statistical properties, we represent the data in time--frequency domain, and characterize the effectiveness of multiple approaches, e.g. statistically viable likelihoods, sampling schemes, segmentation widths, and gaps density. Our analysis yields consistent results across, with overwhelming evidence in favor of a non-stationary model in less than a month of data. Moreover, we show robustness against the presence of additional extragalactic foregrounds, and test the suitability of our approximations on the more complex simulated data in the $\textit{Yorsh}$ data challenge.