Effects of inner crusts on $g$-mode oscillations in neutron stars

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Hauptverfasser: Sun, Hao, Niu, Jia-Xing, Li, Hong-Bo, Xia, Cheng-Jun, Zhou, Enping, Ma, Yiqiu, Zhang, Ying-Xun
Format: Preprint
Veröffentlicht: 2025
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author Sun, Hao
Niu, Jia-Xing
Li, Hong-Bo
Xia, Cheng-Jun
Zhou, Enping
Ma, Yiqiu
Zhang, Ying-Xun
author_facet Sun, Hao
Niu, Jia-Xing
Li, Hong-Bo
Xia, Cheng-Jun
Zhou, Enping
Ma, Yiqiu
Zhang, Ying-Xun
contents In this work we investigate the influence of neutron stars' crusts on the non-radial $g$-mode oscillations and examine their correlations with nuclear matter properties fixed by adopting 10 different relativistic density functionals. At subsaturation densities, neutron star matter takes non-uniform structures and form the crusts. We find that the Brunt-Väisälä (BV) frequency increases significantly at densities slightly above the neutron drip density (i.e., neutron stars' inner crusts), which leads to crust $g$-mode oscillations with their frequencies insensitive to the adopted density functional. At larger densities, BV frequency increases as well due to the core-crust transitions and emergence of muons, which lead to core $g$-mode oscillations. It is found that the obtained core $g$-mode frequencies generally increase with the slope of nuclear symmetry energy $L$, which eventually intersect with that of the crust $g$ modes adopting large enough $L$. This leads to the avoid-crossing phenomenon for the global $g$ modes that encompass contributions from both the crust and core. The correlation between the global $g_1$ mode and $L$ is identified for neutron stars with masses $M\gtrsim 1.4\ M_{\odot}$, which enables the measurements of $L$ based on gravitational wave observations. In our future study, the effects of the discontinuities in density or shear modulus should be considered, while the temperature, rotation, magnetic field, and superfluid neutron gas in neutron stars could also play important roles.
format Preprint
id arxiv_https___arxiv_org_abs_2501_07188
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Effects of inner crusts on $g$-mode oscillations in neutron stars
Sun, Hao
Niu, Jia-Xing
Li, Hong-Bo
Xia, Cheng-Jun
Zhou, Enping
Ma, Yiqiu
Zhang, Ying-Xun
High Energy Astrophysical Phenomena
Nuclear Theory
In this work we investigate the influence of neutron stars' crusts on the non-radial $g$-mode oscillations and examine their correlations with nuclear matter properties fixed by adopting 10 different relativistic density functionals. At subsaturation densities, neutron star matter takes non-uniform structures and form the crusts. We find that the Brunt-Väisälä (BV) frequency increases significantly at densities slightly above the neutron drip density (i.e., neutron stars' inner crusts), which leads to crust $g$-mode oscillations with their frequencies insensitive to the adopted density functional. At larger densities, BV frequency increases as well due to the core-crust transitions and emergence of muons, which lead to core $g$-mode oscillations. It is found that the obtained core $g$-mode frequencies generally increase with the slope of nuclear symmetry energy $L$, which eventually intersect with that of the crust $g$ modes adopting large enough $L$. This leads to the avoid-crossing phenomenon for the global $g$ modes that encompass contributions from both the crust and core. The correlation between the global $g_1$ mode and $L$ is identified for neutron stars with masses $M\gtrsim 1.4\ M_{\odot}$, which enables the measurements of $L$ based on gravitational wave observations. In our future study, the effects of the discontinuities in density or shear modulus should be considered, while the temperature, rotation, magnetic field, and superfluid neutron gas in neutron stars could also play important roles.
title Effects of inner crusts on $g$-mode oscillations in neutron stars
topic High Energy Astrophysical Phenomena
Nuclear Theory
url https://arxiv.org/abs/2501.07188