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arXiv 1507.00837nucl-thastro-ph.HEastro-ph.SR
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$^{208}$ Pb核中中子皮厚度固定时中子星性质的变化

Diversities in the properties of neutron stars at a fixed neutron-skin thickness in $^{208}$Pb nucleus

N. Alam, A. Sulaksono, B. K. Agrawal

摘要:

在扩展的相对论平均场(RMF)模型下,研究了不同介子间交叉耦合对中子星性质的影响.为此,我们得到了两个不同族的扩展RMF模型,对应于不同的非线性交叉耦合项的等效拉格朗日密度的等矢量部分。最低阶贡献的$δ$介子也包括在内。同一族内的不同模型是这样获得的,它们产生了$^{208}$ Pb核中的中子皮厚度值的很大变化。利用这些模型计算了中子星的核壳跃迁密度、半径和正则质量红移($1.4M_{\odot}$)、潮汐极化率参数以及通过直接Urca过程增强冷却所需的阈值质量等性质。在$^{208}$ Pb核中,在较小的中子皮厚度($\sim 0.15$ fm)下,对于不同的模型族,所考虑的大多数中子星性质是显著不同的(10%~ 40%)。

英文摘要:

We study the diversities in the properties of the neutron stars arising due to the different choices for the cross-coupling between various mesons which governs the density dependence of the nuclear symmetry energy in the extended relativistic mean-field(RMF) model. For this purpose, we obtain two different families of the extended RMF model corresponding to different non-linear cross-coupling term in the isovector part of the effective Lagrangian density. The lowest order contributions for the $δ$ mesons are also included. The different models within the same family are so obtained that they yield wide variation in the value of neutron-skin thickness in the $^{208}$Pb nucleus. These models are employed to compute the neutron star properties such as, core-crust transition density, radius and red shift at canonical mass ($1.4M_{\odot}$), tidal polarizability parameter, and threshold mass required for the enhanced cooling through direct Urca process. Most of the neutron star properties considered are significantly different(10\%-40\%) for the different families of models at a smaller neutron-skin thickness ($\sim 0.15$ fm) in the $^{208}$Pb nucleus.

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