Radial Oscillations and Stability of Neutron Stars with Antikaon Condensates

TL;DR

This study explores how antikaon condensates influence neutron star stability and oscillation modes, revealing their significant impact on the stars' maximum mass, stability, and potential observational signatures.

Contribution

It introduces detailed modeling of neutron star oscillations considering antikaon condensates using relativistic mean-field frameworks, highlighting their effects on stability and observable properties.

Findings

Antikaon optical potential depth affects oscillation frequencies.

Antikaon condensation reduces neutron star maximum mass.

Radial oscillation spectra can constrain internal composition.

Abstract

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 with 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 $\bar{K}^0$) 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.