Numerical simulations of super-critical black hole accretion flows in general relativity
Numerical simulations of super-critical black hole accretion flows in general relativity
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DOI：
10.1093/mnras/stt2479
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发表时间：
2013-11
影响因子：
4.8
通讯作者：
A. Sa̧dowski;R. Narayan;J. McKinney;A. Tchekhovskoy
中科院分区：
文献类型：
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作者：
A. Sa̧dowski;R. Narayan;J. McKinney;A. Tchekhovskoy
介绍了一个新的广义相对论辐射磁流体动力学程序KORAL，它采用M1格式来封闭辐射矩方程。该代码已成功地通过了一些测试验证。对非旋转黑洞（a=0.0）和旋转黑洞（a=0.9）的超临界磁化吸积进行了轴对称模拟。两种模型的吸积率为M = 100-200 M_Edd。这些超临界黑洞吸积的第一次广义相对论模拟可能与早期宇宙中的潮汐破裂事件和超吸积超大质量黑洞有关。这两个模拟模型在光学和几何上都很厚，并且有漏斗，能量以相对论气体、坡印亭通量和辐射通量的形式逃逸。喷流在a=0.9的运行中明显更强大。两次运行中的净能量流出率对应于5%（a=0）和33%（a=0.9）的效率，相对于黑洞的质量吸积率进行测量。这些效率与以前的非辐射几何厚盘模拟中测得的结果吻合得很好。此外，在a=0.9的运行中，流出功率似乎起源于旋转的黑洞，这表明相关的物理学在非辐射和超临界吸积流中再次相似。虽然这两个模拟在总能量流出方面是有效的，但两个运行都是辐射效率低下的。它们的亮度只有1-10 L_Edd，对应的辐射效率为0.1%。有趣的是，大部分的辐射亮度都是通过漏斗出现的，漏斗对着一个非常小的立体角。因此，以局部辐射通量来衡量，所发射的辐射是高度超爱丁顿的。
A new general relativistic radiation magnetohydrodynamical code KORAL, is described, which employs the M1 scheme to close the radiation moment equations. The code has been successfully verified against a number of tests. Axisymmetric simulations of super-critical magnetized accretion on a non-rotating black hole (a=0.0) and a spinning black hole (a=0.9) are presented. The accretion rates in the two models are \dot M = 100-200 \dot M_Edd. These first general relativistic simulations of super-critical black hole accretion are potentially relevant to tidal disruption events and hyper-accreting supermassive black holes in the early universe. Both simulated models are optically and geometrically thick, and have funnels through which energy escapes in the form of relativistic gas, Poynting flux and radiative flux. The jet is significantly more powerful in the a=0.9 run. The net energy outflow rate in the two runs correspond to efficiencies of 5% (a=0) and 33% (a=0.9), as measured with respect to the mass accretion rate at the black hole. These efficiencies agree well with those measured in previous simulations of non-radiative geometrically thick disks. Furthermore, in the a=0.9 run, the outflow power appears to originate in the spinning black hole, suggesting that the associated physics is again similar in non-radiative and super-critical accretion flows. While the two simulations are efficient in terms of total energy outflow, both runs are radiatively inefficient. Their luminosities are only \sim 1-10 L_Edd, which corresponds to a radiative efficiency \sim 0.1%. Interestingly, most of the radiative luminosity emerges through the funnels, which subtend a very small solid angle. Therefore, measured in terms of a local radiative flux, the emitted radiation is highly super-Eddington.