General Relativistic Magnetohydrodynamic Simulations of Collapsars: Rotating Black Hole Cases
General Relativistic Magnetohydrodynamic Simulations of Collapsars: Rotating Black Hole Cases
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DOI：
10.1086/382945
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发表时间：
2003-10
期刊：
影响因子：
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通讯作者：
Y. Mizuno;S. Yamada;S. Koide;K. Shibata
中科院分区：
文献类型：
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作者：
Y. Mizuno;S. Yamada;S. Koide;K. Shibata
我们对包括旋转黑洞在内的塌缩星进行了 2.5 维广义相对论磁流体动力学 (MHD) 模拟。这篇论文是我们之前论文的延伸。目前的计算重点是使用广义相对论磁流体力学和简化的微观物理来研究黑洞旋转的影响；也就是说，我们忽略中微子冷却、物理状态方程和光崩解。最初，我们假设这颗恒星的核心塌陷已经失败。手动将几个太阳质量的旋转黑洞插入计算中。我们考虑两种情况，相对于黑洞旋转的同转情况和反向旋转情况。尽管反向旋转的情况对于塌缩星来说可能不现实，但我们将其视为磁场的最大阻力情况。模拟结果显示了盘状结构的形成以及中心黑洞附近喷射状流出的产生。喷射状流出物随着扭曲磁场向外传播并变得准直。我们发现射流主要是由磁场产生和加速的。旋转黑洞情况下的总射流速度与非旋转黑洞情况相当，约0.3c。当黑洞旋转较快时，由于参考系拖曳效应，磁场会发生强烈扭曲。扭转磁场存储的磁能直接转化为射流的动能，而不是作为阿尔文波传播。因此，随着黑洞的旋转变得更快，射流的极向速度变得更快。在快速旋转的黑洞情况下，即使没有恒星旋转，也只能通过磁场的扭曲，通过框架拖曳效应产生喷射状流出。
We have performed 2.5-dimensional general relativistic magnetohydrodynamic (MHD) simulations of collapsars including a rotating black hole. This paper is an extension of our previous paper. The current calculation focuses on the effect of black hole rotation using general relativistic MHD with simplified microphysics; i.e., we ignore neutrino cooling, physical equation of state, and photodisintegration. Initially, we assume that the core collapse has failed in this star. A rotating black hole of a few solar masses is inserted by hand into the calculation. We consider two cases, a corotating case and a counterrotating case with respect to the black hole rotation. Although the counterrotating case may be unrealistic for collapsars, we perform it as the maximally dragging case of a magnetic field. The simulation results show the formation of a disklike structure and the generation of a jetlike outflow near the central black hole. The jetlike outflow propagates outwardly with the twisted magnetic field and becomes collimated. We have found that the jets are generated and accelerated mainly by the magnetic field. The total jet velocity in the rotating black hole case is comparable to that of the nonrotating black hole case, ~0.3c. When the rotation of the black hole is faster, the magnetic field is twisted strongly owing to the frame-dragging effect. The magnetic energy stored by the twisting magnetic field is directly converted to kinetic energy of the jet rather than propagating as an Alfvén wave. Thus, as the rotation of the black hole becomes faster, the poloidal velocity of the jet becomes faster. In the rapidly rotating black hole case the jetlike outflow can be produced by the frame-dragging effect only through twisting of the magnetic field, even if there is no stellar rotation.