New Potential Ultra-compact X-ray Binaries for Space-based Gravitational Wave Detectors From Low-Mass Main-Sequence Companion Channel

TL;DR

This study models the formation and evolution of ultra-compact X-ray binaries from low-mass main-sequence stars, assessing their detectability as gravitational wave sources for space-based observatories like Taiji and TianQin.

Contribution

It introduces a comprehensive framework combining binary evolution, GW signal simulation, and detectability analysis, highlighting UCXBs as promising GW sources for future space missions.

Findings

Milky Way hosts 7-32 observable UCXBs from the MS channel

Taiji or LISA can detect 1-6 sources over 8 years

TianQin detects 1-4 sources, especially with short orbital periods

Abstract

We investigate the formation and evolution of Ultra-Compact X-ray Binaries (UCXBs) using the COMPAS binary evolution code, starting from the Zero Age Main Sequence (ZAMS). Focusing on the low-mass MS companion channel, we simulate gravitational wave (GW) signals from UCXBs with LEGWORK and evaluate their detectability by space-based observatories such as Taiji and TianQin. By incorporating signal-to-noise ratio (SNR) calculations with a threshold of SNR > 5, we provide a realistic framework to assess the detectability of the GW source. Our analysis suggests that the Milky Way currently hosts 7-32 observable UCXBs from the MS companion channel. Taiji or LISA alone could detect 1-6 sources over an 8-year observation period, while TianQin, due to its high-frequency sensitivity, contributes to detecting systems with extremely short orbital periods and can also detect 1-4 sources. Comparison with sensitivity curves validates UCXBs as detectable GW sources, particularly at greater Galactic distances. This study improves our understanding of the evolution of UCXBs and their role as GW sources. By integrating population synthesis, SNR-based analyses, and observational data, we establish UCXBs as significant targets for GW astronomy, paving the way for future missions and theoretical studies of compact binary systems.