Torus formation in neutron star mergers and well-localized short gamma-ray bursts
Torus formation in neutron star mergers and well-localized short gamma-ray bursts
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DOI：
10.1111/j.1365-2966.2006.10238.x
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发表时间：
2005-07
影响因子：
4.8
通讯作者：
R. Oechslin;H. Janka
中科院分区：
文献类型：
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作者：
R. Oechslin;H. Janka
并合中子星（NS）是仍然是神秘的短伽玛射线暴（GRB）源的热门候选者。如果巨大能量释放的中心引擎是这种合并的吸积遗迹黑洞（BH），那么重要的是要了解BH-环面系统的性质，特别是盘质量和致密残留物的质量和旋转速率，与NS双星的特征参数有关。为此，我们提出了相对论光滑粒子流体动力学模拟与共形平坦近似的爱因斯坦场方程和物理，非零温度状态方程。厚盘的形成被强调为一个动力学过程中引起的角动量转移通过潮汐扭矩在合并过程中的非对称系统或在快速旋转的三轴合并后的对象。我们的模拟支持的可能性，第一个良好的本地化短，硬GRB 050509 b，050709，050724，050813起源于NS合并事件，并提供动力的中微子-反中微子湮灭周围的遗迹BH-环面系统。使用模型参数的基础上，这个假设，我们表明，测量的伽玛射线暴的能量和持续时间导致估计的吸积质量和BH质量吸积率是与理论预期兼容。特别是，GRB 050509 b的低能量输出和短持续时间为合并后的时间间隔设定了一个非常严格的上限，即小于100 ms，直到合并残留物坍缩为BH，留下一个只有10.01 M的小质量吸积环。这有利于一个（近）对称的NS+NS二进制与一个典型的质量作为祖先系统。
Merging neutron stars (NSs) are hot candidates for the still enigmatic sources of short gamma-ray bursts (GRBs). If the central engines of the huge energy release are accreting relic black holes (BHs) of such mergers, it is important to understand how the properties of the BH-torus systems, in particular disc masses and mass and rotation rate of the compact remnant, are linked to the characterizing parameters of the NS binaries. For this purpose, we present relativistic smoothed particle hydrodynamic simulations with conformally flat approximation of the Einstein field equations and a physical, non-zero temperature equation of state. Thick disc formation is highlighted as a dynamical process caused by angular momentum transfer through tidal torques during the merging process of asymmetric systems or in the rapidly spinning triaxial post-merger object. Our simulations support the possibility that the first well-localized short and hard GRBs 050509b, 050709, 050724, 050813 have originated from NS merger events and are powered by neutrino-antineutrino annihilation around a relic BH-torus system. Using model parameters based on this assumption, we show that the measured GRB energies and durations lead to estimates for the accreted masses and BH mass accretion rates which are compatible with theoretical expectations. In particular, the low-energy output and short duration of GRB 050509b set a very strict upper limit of less than 100 ms for the time interval after the merging until the merger remnant has collapsed to a BH, leaving an accretion torus with a small mass of only ∼0.01 M ⊙ . This favours a (nearly) symmetric NS+NS binary with a typical mass as progenitor system.