Gravitational-wave Radiation of Double Degenerates with Extremely Low-mass White Dwarf Companions
Zhenwei Li, Xuefei Chen, Hailiang Chen, Jiao Li, Shenghua Yu, Zhanwen Han
Abstract
Abstract Double degenerate (DD) systems are supposed to be significant gravitational-wave (GW) sources for future space-based GW detectors, e.g., the Laser Interferometer Space Antenna (LISA). Recently, one type of DD system with extremely low-mass WD (ELM WD; ≲ 0.30 M ☉ ) companions was found in the ELM Survey. These companions have very short orbital periods and are therefore important sources for LISA detection. Further, due to the thick envelope of ELM WDs compared with massive WDs (e.g., CO WDs), they are much easier to find through the combination of electromagnetic (EM) and GW observations. In this paper, we first obtain the population of ELM WDs in DDs by considering the detailed evolutionary tracks of ELM WDs and then analyzing the GW radiation of these systems. We found that about 6 × 10 3 sources could be solely detected by LISA, including ∼2 × 10 3 chirping sources, and ∼13 (∼107) more sources are expected to be detected by both LISA and the ELM Survey (Gaia).