arXiv 2102.109482021-02nucl-thastro-ph.HE

壳核界面与体中子星性质

Crust-core interface and bulk neutron star properties

Ch. Margaritis, P. S. Koliogiannis, A. Kanakis-Pegios, Ch. C. Moustakidis

备注：: v1: 10 pages, 5 figures, 3 tables; v2: 15 pages, 7 figures, 6 tables, appendix and updated references; accepted for publication in Physical Review C; v3: matched the published version
发表信息：: Phys. Rev. C 104, 025805 (2021)
DOI：: 10.1103/PhysRevC.104.025805

摘要：

核对称能在描述有限核和中子星的性质中起着重要的作用。特别是在重子密度较低的情况下，壳核界面的精确描述强烈依赖于对称能。通常，对称能的定义采用众所周知的抛物近似，但这并不能避免一些缺点。本文应用一类适用于描述中子星内外核的核模型，研究了高阶能量膨胀对壳核跃迁位置的影响。用热力学和动力学方法确定了跃迁密度$n_{\rm t}$和压强$P_{\rm t}$。相应的能量密度泛函被用于研究非自转和慢自转中子星的一些相关性质。我们发现，斜率参数$L$的值越大，展开的收敛速度越慢。此外，利用完全表达式和动力学方法，给出了$n_{\rm t}$和$L$之间的一种普适关系.地壳转动惯量对转捩的位置非常敏感，而对$r$型不稳定性的临界角速度和最小质量位形的影响是缓和的。对潮汐变形能力的影响较小，但不可忽略。在任何情况下，使用抛物线近似都会导致高估$n_{\rm t}$和$P_{\rm t}$，从而导致预测不准确。此外，在某些情况下，甚至在接口处的匹配过程可能会影响相当大的预测，引入与所采用的方法相同数量级的误差。

英文摘要：

The nuclear symmetry energy plays an important role in the description of the properties of finite nuclei as well as neutron stars. Especially, for low values of baryon density, the accurate description of the crust-core interface strongly depends on the symmetry energy. Usually, the well known parabolic approximation is employed for the definition of the symmetry energy without avoiding some drawbacks. In the present paper, a class of nuclear models, suitable for the description of the inner and outer core of neutron stars, is applied in studying the effect of higher orders of the expansion of the energy on the location of the crust-core transition. The thermodynamical and dynamical methods are used for the determination of the transition density $n_{\rm t}$ and pressure $P_{\rm t}$. The corresponding energy density functional is applied for the study of some relevant properties of both nonrotating and slowly rotating neutron stars. We found that the larger the value of the slope parameter $L$, the slower the convergence of the expansion. In addition, a universal relation is presented between $n_{\rm t}$ and $L$, by employing the full expression and dynamical approach. The crustal moment of inertia is very sensitive to the location of the transition while the effects are moderated concerning the critical angular velocity of the $r$-mode instability and minimum mass configuration. The effect on the tidal deformability is less but not negligible. In any case, the use of the parabolic approximation leads to the overestimation of $n_{\rm t}$ and $P_{\rm t}$ and consequently, on inaccurate predictions. Moreover, in some cases, even the matching process at the interface may affect considerably the predictions, introducing errors of the same order with the one due to the employed method.

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