Subtraction of the confusion foreground and parameter uncertainty of resolvable galactic binaries on the networks of space-based gravitational-wave detectors

Abstract

There are tens of millions of compact binary systems in the Milky Way, called galactic binaries (GBs), most of which are unresolved, and the gravitational waves (GWs) emitted overlap to form confusion foreground. By simulating such a confusion foreground, we have studied how LISA, Taiji and TianQin, including their alternative orbital configurations, subtract resolvable GBs when they combine as some networks. The results of our research indicate that the order of the detected number for a single detector from high to low is Taiji-m, Taiji-p (c), LISA, TianQin I, and TianQin II. For detector combinations on the network, the confusion foreground is effectively reduced as the number of detectors grows, and the optimal combinations with different numbers are Taiji-m, $\mathrm{LISA}+\mathrm{Taiji}\text{\ensuremath{-}}\mathrm{m}$, $\mathrm{LISA}+\mathrm{Taiji}\text{\ensuremath{-}}\mathrm{m}+\mathrm{TianQin}\text{ }\mathrm{I}$, and $\mathrm{LISA}+\mathrm{Taiji}\text{\ensuremath{-}}\mathrm{m}+\mathrm{TianQin}\text{ }\mathrm{I}+\text{II}$. The sensitivity curve is optimized as the number of detectors increases, which renders it possible to detect other gravitational-wave sources more precisely and decrease the resolvable GB parameter uncertainty. Based on this, we discuss the parameter uncertainty of resolvable GBs detected by the combinations above and find that GW detection can promote electromagnetic (EM) detection. On the contrary, we discovered that by utilizing EM detection, determining the inclination angle can reduce the uncertainty of GW strain amplitude by $\ensuremath{\sim}93%$, and determining the sky position can reduce the uncertainty of the phase by $\ensuremath{\sim}30%$, further strengthening the connection between GW detection and EM detection, and contributing to the research of multimessenger astronomy.