Synthetic gamma-ray light curves of Kerr black hole magnetospheric activity from particle-in-cell simulations
Synthetic gamma-ray light curves of Kerr black hole magnetospheric activity from particle-in-cell simulations
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DOI：
10.1051/0004-6361/202040158
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发表时间：
2020-12
影响因子：
6.5
通讯作者：
B. Crinquand;B. Cerutti;G. Dubus;K. Parfrey;A. Philippov
中科院分区：
文献类型：
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作者：
B. Crinquand;B. Cerutti;G. Dubus;K. Parfrey;A. Philippov
上下文来自活动星系核的极高能量辐射的超快速耀斑的起源仍然难以捉摸。发生在中心黑洞附近的磁层过程可以解释这些耀斑。目标。我们的目标是弥合模拟和观测之间的差距，通过合成伽马射线光变曲线，以表征黑洞磁层的活动，使用动力学模拟。方法.我们进行了全球轴对称的二维广义相对论粒子模拟克尔黑洞磁层。我们包括一个自洽的治疗辐射过程和等离子体供应，以及一个现实的磁配置，一个大规模的赤道电流片。我们将我们的粒子在细胞中的代码与光线跟踪算法相结合，以产生合成光曲线。结果这些模拟显示了一个高度动态的磁层，以及非常有效的耗散磁能。磁通量的外部供应被发现，以维持磁层在一个动态的状态，否则磁层解决在一个准稳定的Wald状配置。耗散的能量大部分转化为伽马射线光子。在低视角（正面）的光变曲线主要跟踪火花隙活动，并表现出高的可变性。另一方面，在高视角（边缘上）没有发现显著的变化，其中主要贡献来自重连电流片。结论.我们观察到具有电流片的黑洞磁层具有很高的辐射效率。在我们的模拟中，耀斑的典型振幅低于在活动星系核中检测到的振幅。这些耀斑可能是由黑洞外部参数的变化引起的。
Context. The origin of ultra-rapid flares of very high-energy radiation from active galactic nuclei remains elusive. Magnetospheric processes, occurring in the close vicinity of the central black hole, could account for these flares. Aims. Our aim is to bridge the gap between simulations and observations by synthesizing gamma-ray light curves in order to characterize the activity of a black hole magnetosphere, using kinetic simulations. Methods. We performed global axisymmetric 2D general-relativistic particle-in-cell simulations of a Kerr black hole magnetosphere. We included a self-consistent treatment of radiative processes and plasma supply, as well as a realistic magnetic configuration, with a large-scale equatorial current sheet. We coupled our particle-in-cell code with a ray-tracing algorithm in order to produce synthetic light curves. Results. These simulations show a highly dynamic magnetosphere, as well as very efficient dissipation of the magnetic energy. An external supply of magnetic flux is found to maintain the magnetosphere in a dynamic state, otherwise the magnetosphere settles in a quasi-steady Wald-like configuration. The dissipated energy is mostly converted to gamma-ray photons. The light curves at low viewing angle (face-on) mainly trace the spark gap activity and exhibit high variability. On the other hand, no significant variability is found at high viewing angle (edge-on), where the main contribution comes from the reconnecting current sheet. Conclusions. We observe that black hole magnetospheres with a current sheet are characterized by a very high radiative efficiency. The typical amplitude of the flares in our simulations is lower than is detected in active galactic nuclei. These flares could result from the variation in parameters external to the black hole.