Rotating Black Holes as Central Engines of Long Gamma-Ray Bursts : Faster is Better
Rotating Black Holes as Central Engines of Long Gamma-Ray Bursts : Faster is Better
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DOI：
10.1093/pasj/63.6.1243
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发表时间：
2010-10
影响因子：
2.3
通讯作者：
S. Nagataki
中科院分区：
文献类型：
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作者：
S. Nagataki
我们使用不同的克尔参数 a = 0、0.5、0.9 和 0.95 进行了塌缩星的模拟。结果表明，旋转速度更快的黑洞正在驱动能量更高的喷流。对于史瓦西黑洞来说，没有看到喷流，而对于快速旋转的克尔黑洞来说，喷流的总能量高达 10 50 erg (a = 0.95)。为了解释伽马射线暴的高光度，得出的结论是快速旋转的黑洞更受青睐（“越快越好”）。我们还发现，在a = 0.95的情况下，（i）在喷流区域中明显发现了停滞区域，（ii）在喷流中看到了有序的极向场线，（iii）喷流区域被“壁状”结构包围，该结构的压力比喷流区域更高，并且包含强垂直磁场，（iv）喷流是由来自黑洞外地平线的传出坡印廷通量（布兰德福德-兹纳耶克效应）引发的。射流的体积洛伦兹因子仍然处于单位量级。然而，电磁场的能量密度主要由射流中的静止质量的能量密度决定。可以预期，如果我们进行较长时间尺度（10-100 秒量级）的模拟，将会看到相对论性喷流。
We performed simulations of collapsars with different Kerr parameters of a = 0, 0.5, 0.9, and 0.95. It was shown that a more rapidly rotating black hole is driving a more energetic jet. No jet is seen for the case of the Schwartzschild black-hole case, while the total energy of the jet is as large as 10 50 erg for a rapidly rotating Kerr black-hole case (a = 0.95). In order to explain the high luminosity of a gamma-ray burst, it is concluded that a rapidly rotating black hole is favored (‘faster is better’). We also find that in the case of a = 0.95, (i) a stagnation region is clearly found in the jet region, (ii) ordered poloidal field lines are seen in the jet, (iii) the jet region is surrounded by a ‘wall-like’ structure that has a higher pressure than the jet region, and contains strong vertical magnetic fields, and (iv) the jet is initiated by an outgoing Poynting flux from the outer horizon of the black hole (Blandford–Znajek effect). The bulk Lorentz factor of the jet is still on the order of unity. However, the energy density of electro-magnetic fields is dominated by the one of rest-mass in the jet. It can be expected that a relativistic jet will be seen if we perform a simulation for a longer time scale (of the order of 10–100 s).