Extracting the Central Sound Speed of Neutron Stars through Intrinsic Stellar Structure Scaling with Reduced Equation-of-State Model Dependence
Abstract
Inferring neutron star (NS) core properties remains sensitive to the assumed equation of state (EOS). Using a nonlinear Walecka model with generalized ω-meson self-interactions, we construct six EOS families, each containing 103 samples subject to identical nuclear and astrophysical constraints. Despite satisfying these constraints, the families predict markedly different high-density behavior and core properties; higher-order ω interactions can also generate interior sound-speed peaks within purely nucleonic matter. To reduce this model dependence, we use the intrinsic and perturbative analysis of the dimensionless Tolman--Oppenheimer--Volkoff equations (IPAD-TOV) to derive an EOS-independent estimator Θ(X,Ψ) of the central squared sound speed sc2, where X=Pc/εc is the central EOS-parameter and Ψ characterizes the stellar-mass response to central energy density. For canonical 1.4 M⊙ NSs, Θ correlates linearly with sc2 across the families (R2≈0.94-$0.99$). The family-dependent relations converge toward a common optimum: minimizing their dispersion yields sc2≈ 0.523±0.044 and X≈ 0.173+0.020−0.018 for all six families, or sc2≈ 0.496±0.092 and X≈ 0.167+0.030−0.029 when the family without ω self-interaction is excluded. The corresponding radii are 11.73+1.08−0.92 and 11.92+1.76−1.28 km, respectively, with 95% confidence intervals. A unified scaling fitted to all EOS samples supports both extractions. These results show how common stellar-structure relations can constrain NS core properties with reduced EOS-model dependence, even when existing observations cannot distinguish among the underlying EOS descriptions.
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BibTeX
@misc{shi2026extracting,
title = {{Extracting the Central Sound Speed of Neutron Stars through Intrinsic Stellar Structure Scaling with Reduced Equation-of-State Model Dependence}},
author = {Jian-Hao Shi and Bao-Jun Cai and Yu-Gang Ma},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.21806},
eprint = {2610.21806},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.21806},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Extracting the Central Sound Speed of Neutron Stars through Intrinsic Stellar Structure Scaling with Reduced Equation-of-State Model Dependence
AU - Jian-Hao Shi
AU - Bao-Jun Cai
AU - Yu-Gang Ma
PY - 2026
DA - 2026/10/15
PB - arXiv
DO - 10.48550/arxiv.2610.21806
UR - https://arxiv.org/abs/2610.21806
AB - Inferring neutron star (NS) core properties remains sensitive to the assumed equation of state (EOS). Using a nonlinear Walecka model with generalized ω-meson self-interactions, we construct six EOS families, each containing 10^3 samples subject to identical nuclear and astrophysical constraints. Despite satisfying these constraints, the families predict markedly different high-density behavior and core properties; higher-order ω interactions can also generate interior sound-speed peaks within purely nucleonic matter. To reduce this model dependence, we use the intrinsic and perturbative analysis of the dimensionless Tolman--Oppenheimer--Volkoff equations (IPAD-TOV) to derive an EOS-independent estimator Θ(X,Ψ) of the central squared sound speed s_c^2, where X=P_c/ε_c is the central EOS-parameter and Ψ characterizes the stellar-mass response to central energy density. For canonical 1.4 M_⊙ NSs, Θ correlates linearly with s_c^2 across the families (R^2≈0.94-$0.99$). The family-dependent relations converge toward a common optimum: minimizing their dispersion yields s_c^2≈ 0.523±0.044 and X≈ 0.173^+0.020_−0.018 for all six families, or s_c^2≈ 0.496±0.092 and X≈ 0.167^+0.030_−0.029 when the family without ω self-interaction is excluded. The corresponding radii are 11.73^+1.08_−0.92 and 11.92^+1.76_−1.28 km, respectively, with 95% confidence intervals. A unified scaling fitted to all EOS samples supports both extractions. These results show how common stellar-structure relations can constrain NS core properties with reduced EOS-model dependence, even when existing observations cannot distinguish among the underlying EOS descriptions.
ER -