Possibility of rapid neutron star cooling with a realistic equation of state
Possibility of rapid neutron star cooling with a realistic equation of state
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DOI：
10.1093/ptep/ptz116
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发表时间：
2019-10
影响因子：
3.5
通讯作者：
Akira Dohi;K. Nakazato;M. Hashimoto;Y. Matsuo;T. Noda
中科院分区：
文献类型：
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作者：
Akira Dohi;K. Nakazato;M. Hashimoto;Y. Matsuo;T. Noda
快速冷却过程的发生与否对中子星的热演化至关重要。特别是，作为快速冷却过程之一的直接URCA过程的阈值是由内部质子分数Y_p或核对称能决定的。由于最近的观测表明中子星的半径很小，所以对称性能量最好是一个较低的值。本文采用三种状态方程(EOS)模型：Togashi、Sheni和LS220状态方程模型对中子星的冷却进行了模拟。Togashi状态方程是最近在有限温度下用真实的核势构造的，并被发现解释了中子星的小半径。结果发现，由于直接的Urca过程是被禁止的，所以使用Togashi状态方程时，中子星的冷却是缓慢的。这是因为Togashi Eos的对称能比其他EOS的对称能低。因此，为了解释使用Togashi状态方程观测到的孤立中子星的年龄和表面温度，无论表面成分如何，都需要其他快速冷却过程。
Whether fast cooling processes occur or not is crucial for the thermal evolution of neutron stars. In particular, the threshold of the direct Urca process, which is one of the fast cooling processes, is determined by the interior proton fraction $Y_p$, or the nuclear symmetry energy. Since recent observations indicate the small radius of neutron stars, a low value is preferred for the symmetry energy. In this study, simulations of neutron star cooling are performed adopting three models for the equation of state (EoS): Togashi, Shen, and LS220 EoSs. The Togashi EoS has been recently constructed with realistic nuclear potentials under finite temperature, and found to account for the small radius of neutron stars. As a result, we find that, since the direct Urca process is forbidden, the neutron star cooling is slow with use of the Togashi EoS. This is because the symmetry energy of Togashi EoS is lower than those of other EoSs. Hence, in order to account for observed age and surface temperature of isolated neutron stars with the use of the Togashi EoS, other fast cooling processes are needed regardless of the surface composition.