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arXiv · 2608.02463

The $g$-mode frequencies in cold neutron stars and nuclear saturation parameters

Hajime Sotani·Hajime Togashi
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Abstract

Oscillation frequencies excited in neutron stars are crucial for extracting their interior properties. In addition to the fundamental and pressure modes, the gravity ($g$-) modes can be excited even in zero-temperature stellar models due to the composition gradient. In this study, we systematically study the $g$-mode frequencies, focusing on the nucleonic equation of state. Then, we can derive an empirical relation for the 1st $g$-mode frequencies as a function of the stellar compactness and the combination of the nuclear saturation parameters, $\eta_0 \equiv L/K_0$, where $K_0$ and $L$ denote the incompressibility of symmetric nuclear matter and the density dependence of the nuclear symmetry energy, respectively. If an observed 1st $g$-mode frequency significantly deviates from our empirical relation, it may indicate the emergence of additional degrees of freedom or new compositions inside the star.

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Hajime Sotani, Hajime Togashi. 2026-08-03. The $g$-mode frequencies in cold neutron stars and nuclear saturation parameters. https://doi.org/10.1103/c4yl-hdkm

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