Heat capacity of the neutron star inner crust within an extended nuclear statistical equilibrium model
Heat capacity of the neutron star inner crust within an extended nuclear statistical equilibrium model
复制标题
扩展核统计平衡模型中中子星内壳的热容
DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
A. Raduta
中科院分区：
文献类型：
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作者：
S. Burrello;F. Gulminelli;F. Aymard;M. Colonna;A. Raduta
背景：地壳中的超流性是原中子星冷却特性的关键因素。目前的理论计算采用准粒子平均场Hartree-Fock-Bogoliubov理论，准粒子态的占据数随温度变化。
目的：有限温度恒星物质以不同核种的整体分布为特征。我们想要评估这种分布在计算地壳内的热容量方面的重要性。
方法：根据最近的一项工作，将Wigner-Seitz胞元映射成具有簇自由度的模型。有限的温度分布由Wigner-Seitz胞格的统计集合给出。此外，我们还在局域密度BCS近似中引入了配对关联，无论是在均匀的非束缚中子组分中，还是在团簇与中子的界面区域中。
结果：在100keV~2 MeV的温度范围内，计算了对应于地壳内部不同重子密度条件下的热容。我们发现，在中等密度下，考虑星团分布的影响很小，但它对靠近外壳和靠近核心的热容有很大影响。此外，我们还指出，考虑质子组分的温度演化对于定量可靠地估计热容量是非常重要的。
结论：我们给出了第一个同时包含有限温度下星团统计分布的恒星物质的模型化，以及在非束缚中子成分中的配对关联。在未来的中子星冷却曲线计算中，可以很容易地考虑核分布对超流体性质的影响。在高温下观察到共振布居对热容的强烈影响，这一点值得在更微观的计算中进一步研究。
Background: Superfluidity in the crust is a key ingredient for the cooling properties of proto-neutron stars. Present theoretical calculations employ the quasiparticle mean-field Hartree-Fock-Bogoliubov theory with temperature-dependent occupation numbers for the quasiparticle states.
Purpose: Finite temperature stellar matter is characterized by a whole distribution of different nuclear species. We want to assess the importance of this distribution on the calculation of heat capacity in the inner crust.
Method: Following a recent work, the Wigner-Seitz cell is mapped into a model with cluster degrees of freedom. The finite temperature distribution is then given by a statistical collection of Wigner-Seitz cells. We additionally introduce pairing correlations in the local density BCS approximation both in the homogeneous unbound neutron component, and in the interface region between clusters and neutrons.
Results: The heat capacity is calculated in the different baryonic density conditions corresponding to the inner crust, and in a temperature range varying from 100 KeV to 2 MeV. We show that accounting for the cluster distribution has a small effect at intermediate densities, but it considerably affects the heat capacity both close to the outer crust and close to the core. We additionally show that it is very important to consider the temperature evolution of the proton fraction for a quantitatively reliable estimation of the heat capacity.
Conclusions: We present the first modelization of stellar matter containing at the same time a statistical distribution of clusters at finite temperature, and pairing correlations in the unbound neutron component. The effect of the nuclear distribution on the superfluid properties can be easily added in future calculations of the neutron star cooling curves. A strong influence of resonance population on the heat capacity at high temperature is observed, which deserves to be further studied within more microscopic calculations.