Corrigendum to “Searches for continuous gravitational waves from neutron stars: A twenty-year retrospective” [Astropart. Phys. 153 (2023) 102880

Optical transients from non-explosive double white-dwarf mergers: The case of a central neutron star remnant

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Inference of Neutron Star Mass Distributions and the Dense Matter Equation of State from Multimessenger Observations

A NICER and AstroSat view of the neutron star low-mass X-ray binary 1A 1246 - 588

Hadronic Processes, Plasma Evolution, and Neutrino Emission in Magnetic Towers of Neutron Star Merger Remnants

Impact on inferred neutron star equation of state due to nonlinear hydrodynamics, background spin, and relativity

Abstract We present a detailed chemical-abundance and kinematic analysis of four extremely metal-poor (EMP; [Fe/H] ≤ −3.0) stars identified from Gaia BP–RP data in our ongoing search for the most primitive stars. This includes a primary target, Gaia DR3 2563539603865382656 (hereafter G256353), a strongly r -process-enhanced star with [Eu/Fe] = +1.20 and [Ba/Eu] = −0.64. Our results are based on high-resolution, high-signal-to-noise-ratio GHOST spectra from Gemini-South. For the full sample, we statistically match the light-element abundances with those predicted from Population III supernova models. The best-fit model suggests massive progenitors with stellar masses of M ⋆ ∼ 20–30 M ⊙ . In addition, we determine orbital histories for all of the stars. We find that Gaia DR3 2887334237669844480 appears to be kinematically associated with Atari, an accreted structure in the Galactic disk. This star has low abundance ratios of strontium ([Sr/Fe] = −1.09) and barium ([Ba/Fe] = −0.37), which support an accretion origin. For G256353, we determine chemical abundances for 15 neutron-capture elements. We compare the observed heavy-element pattern for G256353 with that of the Sun, HD 222925, and two neutron star merger models. The r -process elements in G256353 align reasonably well with HD 222925, the scaled-solar pattern (except for the first peak), and a recent predicted pattern associated with neutron star mergers. This consistency reinforces the universality of the main r -process across diverse astrophysical environments.

Binary neutron stars from the moon: early warnings and precision science for the Artemis era

Advantages of Kilohertz Detector in Detecting Gravitational Wave from Binary Neutron Star Mergers

A 44-min periodic radio transient in a supernova remnant.

The study of dense matter has been greatly advanced by progress in theoretical high-energy simulations and modern observational astronomy. Neutron stars serve as natural laboratories for probing matter under extreme density and strong gravitational fields. While polytropic equations of state are widely employed, conventional models based on a single polytropic index cannot adequately represent the stratified, layered nature of realistic compact-star interiors. To address this limitation, we develop a composite relativistic polytropic model in which the polytropic index varies smoothly with radius. By coupling the Einstein field equations with a generalized composite polytropic equation of state, we derive the composite Tolman–Oppenheimer–Volkoff (CTOV) system. The resulting nonlinear equations are solved using a Monte Carlo-based numerical integration method, which efficiently handles stiffness while enabling probabilistic exploration of the parameter space and natural uncertainty quantification. Our results demonstrate that increasing the relativistic parameter σ significantly reduces both the Emden function and the enclosed mass function, producing more compact stellar configurations. Sharper core–envelope transitions (ε = 0.01) yield systematically higher compactness than smoother transitions (ε = 0.03). The derived mass–radius relations reproduce the observed diversity of neutron stars, successfully matching both low-mass, large-radius systems such as PSR J0030 + 0451 and high-mass compact pulsars such as PSR J1614–2230. Importantly, the maximum-mass analysis shows that stiff composite configurations (nc = 1, ne = 2, xc = 0.7) can support gravitational masses up to Mmax ≈ 3.47 M_{ odot } for ε = 0.01 and Mmax ≈ 2.71 M_{ odot } for ε = 0.03, with corresponding minimum radii in the range Rmin ≈ 10.6–13.2 km, consistent with current observational constraints. These findings confirm that composite polytropes provide a flexible, physically motivated framework for modeling stratified compact stars and for constraining the dense-matter equation of state.

Anisotropic Ejecta from Binary Neutron Star Mergers: Self-consistent Main Thermal and Late-time Radio Emission of Neutron-star-powered Kilonovae

Chasing Gamma-Ray Signals from Binary Neutron Star Coalescences with the Cherenkov Telescope Array: Prospects and Observing Strategies

Radial oscillations provide a direct probe of the stability and compressibility of neutron stars and are highly sensitive to the equation of state of dense matter. In this work, we investigate the impact of antikaon condensates on the radial oscillation properties of neutron stars. We model neutron star matter using equations of state exploring a wide range of stiffness. For this purpose, both non-linear and density-dependent relativistic mean-field frameworks are employed to develop equations of state that are consistent with current astrophysical constraints. We further consider the emergence of antikaon condensates (K - and K̅ 0) in the stellar core, which modifies the pressure-energy density relation of dense matter. We find that the nature of the transition from nuclear matter to the condensed phase is sensitive to the antikaon optical potential depth and underlying equation of state. We compute the fundamental and higher-order radial oscillation modes for neutron stars containing antikaon condensates over a range of antikaon optical potential depths. Our results demonstrate that the antikaon optical potential depth plays a decisive role in governing the systematic shifts observed in the radial oscillation frequencies, while also significantly reducing the stability limits and maximum masses of neutron stars. These imprints of antikaon condensation on radial oscillation spectra provide a promising avenue for future multi-messenger observations and high-frequency gravitational-wave searches to directly probe and constrain the internal composition and equation of state of neutron stars.

Non-radial oscillations in dark matter admixed neutron stars using a two fluid formalism

Axion effects on the non-radial oscillations of neutron stars

Symmetric and asymmetric properties of neutron star

Dark matter (DM) models with a conserved particle-antiparticle number, n_{χ}-n_{χ[over ˜]}, and the asymmetry in the cosmological abundance n_{χ}≠n_{χ[over ˜]}, are known to be challenged by the existence of old neutron stars (NSs), as the sufficient accumulation of DM will lead to the collapse of NSs into black holes. We demonstrate that the applicability of these constraints is much wider and covers models with symmetric populations of DM, n_{χ}=n_{χ[over ˜]}, as the process of DM capture regulated by a nucleon-DM scattering can be inherently asymmetric, σ_{χn}≠σ_{χ[over ˜]n}. The asymmetry is induced by the interference of different types of χ-n interactions, provided that their combination is odd under charge conjugation in the DM sector, C_{χ}, and even under combined parity P_{χ+n}. We provide a complete analysis of DM-nucleon bilinear χ-n interactions and find that this asymmetry is very generic. Using canonical NS parameters and local DM halo inputs, we exclude spin-averaged scattering cross sections down to σ_{nχ}≳10^{-46} cm^{2} at DM mass m_{χ}≲10^{10} GeV for the maximally asymmetric capture rate and show that the constraints persist down to very small values of the cross-section asymmetry, A=(σ_{χn}-σ_{χ[over ˜]n})/(σ_{χn}+σ_{χ[over ˜]n})≳10^{-5}.

Spectral Energy Distribution and Galactic Kinematic Diagnostics for Dormant Black Hole–Neutron Star Binary Candidates