Investigating galactic double white dwarfs for sub-milliHz gravitational wave mission ASTROD-GW

TL;DR

This paper assesses the potential of sub-milliHz gravitational wave missions, like ASTROD-GW, to detect galactic double white dwarf binaries and analyze the confusion noise, advancing understanding of low-frequency GW observations.

Contribution

It evaluates the detectability of galactic DWD binaries and the confusion noise in the sub-mHz GW band for proposed missions beyond LISA.

Findings

Confusion noise from unresolved DWDs could dominate the sub-mHz GW band.

Parameter estimation improves with different detector sensitivities and population models.

Subtraction of the foreground could reduce residual noise by two orders of magnitude.

Abstract

A large number of galactic binary systems emit gravitational waves (GW) continuously with frequencies below $\sim$10 mHz. The LISA mission could identify tens of thousands of binaries over years of observation and will be subject to the confusion noise around 1 mHz yielded by the unresolved sources. Beyond LISA, there are several missions have been proposed to observe GWs in the sub-mHz range where the galactic foreground is expected to be overwhelming the instrumental noises. In this study, we investigate the detectability of sub-mHz GW missions to detect the galactic double white dwarf (DWD) binaries and evaluate the confusion noise produced by the undistinguished DWDs. This confusion noise could also be viewed as a stochastic GW foreground and be effectively observed in the sub-mHz band. The parameter determinations for the modeled foreground are examined by employing different detector sensitivities and population models. By assuming the determined foregrounds could be subtracted from the data, we evaluate the residuals which are expected to have power spectral densities two orders of magnitude lower than the originals data.