Fate of twin stars on the unstable branch: Implications for the formation of twin stars
Fate of twin stars on the unstable branch: Implications for the formation of twin stars
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DOI：
10.1103/physrevd.105.043014
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发表时间：
2021-05
影响因子：
5
通讯作者：
P. Espino;V. Paschalidis
中科院分区：
文献类型：
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作者：
P. Espino;V. Paschalidis
产生第三个稳定致密星族的混合强子-夸克状态方程已被证明与 LIGO-Virgo 事件 GW170817 兼容。第三族中的稳定构型称为混合强子-夸克星。平衡稳定杂化强子-夸克星分支被稳定中子星分支与不稳定杂化强子夸克星分支分开。这些不稳定构型的最终状态尚未被研究，它可能对双星的形成和存在产生影响——双星是与中子星质量相同但半径不同的混合星。我们用一阶相变修改现有的混合强子-夸克状态方程，以保证广义相对论流体动力学方程的适定初值问题，并通过完全广义相对论的三维模拟研究非旋转或旋转不稳定双星的动力学。我们发现不稳定的双星自然会向强子分支迁移。在进入强子状态之前，这些恒星在动态时间尺度上经历（准）径向振荡，而核心在两个阶段之间弹跳。我们的研究表明，如果相变在能量密度大幅跃升的情况下持续下去，可能很难形成稳定的双星，因此天体物理混合强子-夸克星的质量更有可能高于双星状态。我们还研究了混合星的最小质量不稳定性，发现这些结构不会爆炸，这与中子星的最小质量不稳定性不同。此外，我们的结果表明，两个量子色动力学阶段之间的振荡可以提供与核心塌缩超新星和白矮星中子星合并中的此类相变相关的引力波信号。
Hybrid hadron-quark equations of state that give rise a third family of stable compact stars have been shown to be compatible with the LIGO-Virgo event GW170817. Stable configurations in the third family are called hybrid hadron-quark stars. The equilibrium stable hybrid hadron-quark star branch is separated by the stable neutron star branch with a branch of unstable hybrid hadronquark stars. The end-state of these unstable configurations has not been studied, yet, and it could have implications for the formation and existence of twin stars – hybrid stars with the same mass as neutron stars but different radii. We modify existing hybrid hadron-quark equations of state with a first-order phase transition in order to guarantee a well-posed initial value problem of the equations of general relativistic hydrodynamics, and study the dynamics of non-rotating or rotating unstable twin stars via 3-dimensional simulations in full general relativity. We find that unstable twin stars naturally migrate toward the hadronic branch. Before settling into the hadronic regime, these stars undergo (quasi)radial oscillations on a dynamical timescale while the core bounces between the two phases. Our study suggests that it may be difficult to form stable twin stars if the phase transition is sustained over a large jump in energy density, and hence it may be more likely that astrophysical hybrid hadron-quark stars have masses above the twin star regime. We also study the minimum-mass instability for hybrid stars, and find that these configurations do not explode, unlike the minimummass instability for neutron stars. Additionally, our results suggest that oscillations between the two Quantum Chromodynamic phases could provide gravitational wave signals associated with such phase transitions in core-collapse supernovae and white dwarf-neutron star mergers.