The search for continuous gravitational waves represents a significant frontier in astrophysics, and a new study focuses on Sco X-1, a well-known binary system, as a potential source. Gianluca Pagliaro, Maria Alessandra Papa, and Jing Ming, all from the Max Planck Institute for Gravitational Physics and Leibniz Universität Hannover, alongside Devina Misra from the Norwegian University of Science and Technology, modelled the long-term evolution of Sco X-1 to determine the likelihood of detecting gravitational waves emitted from this system. Their work investigates how the neutron star within Sco X-1 spins and how asymmetries, such as magnetic mountains or crustal fractures, contribute to the gravitational wave signal. The team’s simulations, conducted using detailed stellar evolution models, reveal that while current detectors require substantial neutron star deformation for a detection, next-generation instruments dramatically increase the probability of observing gravitational waves from Sco X-1, potentially uncovering a loud signal if the neutron star’s crust undergoes breakage during its active phase.
The team performed detailed simulations, varying parameters like the donor star’s mass, accretion efficiency, and the neutron star’s ellipticity to understand how these factors influence gravitational wave emission. Researchers calculated the expected strength and frequency of gravitational waves based on the simulated neutron star properties, comparing these to the sensitivity of current and future gravitational wave detectors, including LIGO, Virgo, KAGRA, and the planned Cosmic Explorer. The study examined both magnetic confinement and residual ellipticity, demonstrating that the residual ellipticity scenario appears more promising for detection. This involved considering two mechanisms responsible for generating gravitational wave torque: magnetic mountains and crustal breakage. The study also examined the impact of crustal breakage on the neutron star’s spin, finding that if the crust breaks, the resulting emission of continuous gravitational waves provides the torque needed to halt spin-up. The study focused on two mechanisms responsible for generating the non-axisymmetry that drives gravitational wave emission: magnetic mountains on the neutron star and deformation resulting from crustal breakage. The team discovered that a significant magnetic ellipticity is necessary for detection with current instruments, but that the highest detectable frequency increases with accretion efficiency, reaching as high as 360Hz.
With the enhanced sensitivity of third-generation detectors, such as the Cosmic Explorer and Einstein Telescope, neutron stars with significantly smaller ellipticities become detectable. However, the waveform and detectable frequency range are highly dependent on the binary parameters, spanning a broad range of 600-1700Hz, influenced by both accretion efficiency and the mass of the donor star. The team investigated two mechanisms responsible for these asymmetries, magnetic mountains on the neutron star’s surface and deformations resulting from crustal breakage. The frequency of these signals is strongly linked to the system’s characteristics, particularly the mass accretion rate and the mass of the companion star, with detectable frequencies potentially spanning a wide range from 600 to 1700Hz.
👉 More information
🗞 Sco X-1 as a continuous gravitational waves source: modelling the secular evolution using MESA
🧠 ArXiv: https://arxiv.org/abs/2510.21529
