Testing Gravitational-Wave Signal From Verification Binaries with Space-Based Gravitational-Wave Detectors

Abstract

Space-based gravitational wave (GW) detectors will open the millihertz band to survey ultra-compact binaries (UCBs). \textit{Verification binaries} (VBs) is a key to verifying the performance of space-based GW detectors because its parameters are known from electromagnetic observations and it is expected to be a detectable source of GW. We evaluated 73 VBs, computing their detection prospects and parameter estimation precision for individual GW detectors and networks. Among single detectors, DECIGO shows the highest sensitivity, detecting 71 sources at signal-to-noise ratio $ρ$ $\geq$ 5, compared to 42 for LISA, 32 for Taiji, and 27 for TianQin, while the full TianQin + LISA + Taiji + DECIGO network improves this to 73 detectable sources. For parameter estimation, individual detectors achieve median precisions on the order of $\sim 10^{-2}-10^{-1} \, \text{M}_{\odot}$ for chirp mass, $\sim 1\,\text{kpc}$ for distance, $\sim 1-17\,\text{deg}$ for inclination and $\sim 10^{-4}-10^{-2}\,\text{deg}^2$ for sky localization. The complete TianQin + LISA + Taiji + DECIGO network enhances these constraints substantially, reducing the median uncertainties to approximately $\sim 10^{-2} \, \text{M}_{\odot}$ in chirp mass, $\sim 10^{-2}\,\text{kpc}$ in distance, $\sim 1\,\text{deg}$ in inclination and $\sim 10^{-4}\,\text{deg}^2$ in sky localization. The upcoming space-based GW detectors, especially their networks, have outstanding observational capabilities for UCB, which will advance our research on multi-messenger astronomy and deepen our understanding of UCB in the Milky Way.

Figures (4)

• Figure 1: The sensitivity curves of TianQin, LISA, Taiji and DECIGO. The red solid line, black dash-dot line, magenta dashed line, and blue dotted line correspond to TianQin, LISA, Taiji, and DECIGO respectively, defined in Eqs. (\ref{['eq:S_N_TQ']})-(\ref{['eq:S_N_DECIGO']}).
• Figure 2: The characteristic strain versus sensitivity curve. The red solid line, black dash-dot line, magenta dashed line, and blue dotted line correspond to the sensitivity curve of TianQin, LISA, Taiji and DECIGO, respectively, defined in Eqs. (\ref{['eq:S_N_TQ']})-(\ref{['eq:S_N_DECIGO']}). The blue circle, orange square, green triangle, red diamond and purple star represent AM CVn, DWD, CWDB, sdB and UCXB, respectively.
• Figure 3: The left column shows the results for single detectors (TianQin, LISA, Taiji, DECIGO), while the right column shows the results for multi-detector networks (TL, TD, LD, TLD, TLTD). For each configuration, the distributions of pessimistic (Min), most likely (Med), and optimistic (Max) estimates of the SNR are provided.
• Figure 4: The detectable number ($\rho \geq 5$) of the 73 VB over time. Detectors are distinguished by both line colors and marker shapes: TianQin (blue circle), LISA (orange square), Taiji (green triangle up), DCIGO (red diamond), TL (purple triangle down), TD (brown triangle left), LD (pink triangle right), TLD (gray pentagon), and TLTD (olive star).