Gravitational Waves from Neutron Stars: Detection Prospects and Inferences for Two Distinct Types of Remnants

The detection of gravitational waves from compact binary coalescences is impacting our knowledge of stellar-origin compact objects. In particular, gravitational waves from neutron stars encode key information about the nature of matter at nuclear densities and above. Its gravitational-wave spectrum is linked to neutron star properties and can be used to impose constraints on the equation of state, complementing those obtained by electromagnetic observations or heavy-ion experiments. In turn, those constraints can be used to infer key properties as the masses and radii of neutron stars, their tidal deformability, or their moment of inertia. Numerical simulations of neutron stars, either in compact binary systems or those formed in supernova explosions, are fundamental to assist in the detection of the gravitational waves they emit. Simulations are also essential for understanding their formation in highly dynamical events and assessing the role they play across various fields: relativistic astrophysics (as the central engine of gamma-ray bursts and kilonovae), gravitational physics (as prime sources of gravitational waves), cosmology (as standard sirens), and nuclear physics (to constrain the equation of state). In this article, we review the prospects to detect gravitational waves from two “types” of neutron stars — the hypermassive neutron star resulting from the merger of two neutron stars in a binary system, and the proto-neutron star born after the gravitational collapse of the core of a sufficiently massive progenitor star. Moreover, we also discuss ongoing efforts to infer parameters of the source from the analysis of the gravitational-wave signals and the wealth of physical information that can potentially be extracted. Abstract Published by the Jagiellonian University 2025 authors