Gravitational Waves from Strongly Magnetized Eccentric Neutron Star Binaries

Abstract We explore the dynamics of neutron star binaries that approach their final inspiral stages with residual eccentricity and strong magnetic fields, features that can arise in systems formed through dynamical capture of relatively young neutron stars. Our analysis focuses on identifying magnetic field imprints on the gravitational-wave signal arising from two mechanisms: magnetic interaction between the neutron stars and electromagnetic radiation from the system’s effective dipole. Using a perturbative approach, we obtain the associated gravitational-wave energy-loss rate and phase evolution, and quantify detectability through cumulative dephasing, horizon distances, and Fisher-matrix analyses. While magnetic effects are intrinsically small, entering at 2 post-Newtonian order, their cumulative influence over extended inspirals will become distinguishable in future detectors owing to enhanced low-frequency sensitivity. For binaries with comparable magnetic fields, we show that 10 14 G systems will be detectable up to ∼10 Mpc with DECIGO and the Einstein Telescope, while 10 15 G fields will be discernible out to several hundred megaparsecs. For extreme fields of 10 16 G, third-generation detectors could probe out to gigaparsec scales. These findings suggest that magnetic effects in compact binaries can indeed become observable with next-generation detectors, offering a potential probe of magnetar-level fields and binary formation pathways.