Recently, a graduate student from the Optical Astronomy and Technology Application Research Division at Xinjiang Astronomical Observatory (XAO) of the Chinese Academy of Sciences (CAS), under the guidance of Prof. LIU Jinzhong, conducted an in-depth analysis of ultracompact X-ray binaries (UCXBs) evolved through the low-mass main-sequence companion channel and explored the detection feasibility of these gravitational wave sources by space-based gravitational wave detectors.

The related research findings were published in The Astrophysical Journal (2025, ApJ, 981, 175).

Ultracompact X-ray binaries represent a special class of X-ray binary systems characterized by extremely short orbital periods (typically less than 1 hour), resulting in remarkably small binary separations. These systems serve as key observational targets for space-based gravitational wave detectors and typically consist of a compact object (neutron star or black hole) and an evolved companion (e.g., a white dwarf), producing intense X-ray radiation through mass accretion.

In this study, the researchers used a large-sample rapid stellar evolution method to simulate the evolutionary trajectories of millions of binary systems. Revealing how low-mass companions form UCXBs through specific evolutionary channels, with the simulation results align with the physical parameters of known observational samples.

Using noise-signal coupling analysis, they quantified the signal-to-noise ratio (SNR) distribution and detectable numbers of UCXB gravitational wave signals for different space-based detectors (e.g., LISA, Taiji, TianQin).  

The results showed that UCXBs formed through the low-mass main-sequence companion channel emit gravitational wave signals with frequencies closely matching the sensitive band of Taiji space-based gravitational wave detector, making them potential key targets for such detectors. 

This study has identified a new formation channel for UCXB gravitational wave sources and provides quantitative foundations for evaluating the performance thresholds of space-based detectors, laying solid foundation for further observational strategy development .

The research was supported by the National Natural Science Foundation of China,the Tianshan Talent Training Program,and other funding sources.

    Figure 1: Comparison of gravitational wave signals from UCXBs and sensitivity curves of different gravitational wave detectors