Year: 2026
Type: article
Abstract: We present a novel resonance mechanism that can occur in {compact-star} binaries: a spin-orbit resonance. This resonance locks the binary into a unique state where {the spin of one component} evolves alongside the orbit. The resonance requires this component to possess a finite ellipticity $ε$, and we find that the locking probability is proportional to $\sqrtε$. We show that resonance locking and its subsequent breaking produce a characteristic phase signature in the gravitational waveform, opening a new observational channel for probing intrinsic ellipticity in compact-star binaries, including exotic compact objects. In addition, as an illustrative astrophysical scenario, we discuss magnetars, whose strong internal fields can source the required ellipticity and may place the signal in the ground-based low-frequency band, although their abundance at merger remains uncertain. We have also conducted a search in all neutron star binaries up to the O4a gravitational-wave catalog, with no positive event found so far.
DOI: 10.1103/mz9l-z23x
Authors: Zhiqiang Miao, Huan Yang
Institutions: Shanghai Jiao Tong University, Tsinghua University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
Funders: National Science and Technology Council, National Science Foundation, Ministry of Education, Culture, Sports, Science and Technology, National Natural Science Foundation of China, Academia Sinica, China Postdoctoral Science Foundation, National Research Foundation of Korea, Max-Planck-Gesellschaft, Centre National de la Recherche Scientifique, Science and Technology Facilities Council, Australian Research Council, Japan Society for the Promotion of Science, Instituto Nazionale di Fisica Nucleare, National Postdoctoral Program for Innovative Talents
Awards: G2237580232, G2840614319, G8826831918
OpenAlex ID: W7203684925