Probing dissipation mechanisms in BL Lac jets through X-ray polarimetry
Probing dissipation mechanisms in BL Lac jets through X-ray polarimetry
复制标题
通过 X 射线偏振测定法探测 BL Lac 射流的耗散机制
DOI：
10.1093/mnras/sty1491
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发表时间：
2018
影响因子：
4.8
通讯作者：
Coppi, P
中科院分区：
文献类型：
--
作者：
Tavecchio, F;Landoni, M;Sironi, L;Coppi, P
耀变射流中能量通量的耗散在相对论性粒子的加速中起着关键作用。对于耗散过程，通常考虑两种可能性：磁重联（可能由磁主导射流的不稳定性触发）或冲击（对于弱磁化流）。我们考虑分析最先进的模拟结果的两种场景预期的极化特征。对于磁重联场景，我们使用全局相对论 MHD 模拟的结果得出结论，发射可能发生在具有非结构化磁场的湍流区域，尽管模拟不允许我们得出确切的结论。另一方面，通过局部细胞内粒子模拟，我们表明，对于具有适合粒子加速的磁场几何形状的激波，激波前沿的自生磁场主要与激波法线正交，并在下游变得准平行。基于这一结果，我们开发了一个简化模型来计算与频率相关的偏振度，假设高能粒子在激波和冷却下游注入。我们将我们的结果应用于 HBL，即在紫外软 X 射线能量下同步加速器输出最大的耀变体。虽然在光学波段中预测的偏振度较低，但在 X 射线发射中，理想情况下可以达到 50%，特别是在活动/耀斑状态下。在活动状态下进行的光学和 X 射线波段测量之间的比较（对于计划中的 IXPE 卫星来说是可行的）预计将为耗散和加速过程提供有价值的约束。
The dissipation of energy flux in blazar jets plays a key role in the acceleration of relativistic particles. Two possibilities are commonly considered for the dissipation processes, magnetic reconnection – possibly triggered by instabilities in magnetically dominated jets – or shocks – for weakly magnetized flows. We consider the polarimetric features expected for the two scenarios analyzing the results of state-of-the-art simulations. For the magnetic reconnection scenario we conclude, using results from global relativistic MHD simulations, that the emission likely occurs in turbulent regions with unstructured magnetic fields, although the simulations do not allow us to draw firm conclusions. On the other hand, with local particle-in-cell simulations we show that, for shocks with a magnetic field geometry suitable for particle acceleration, the self-generated magnetic field at the shock front is predominantly orthogonal to the shock normal and becomes quasi-parallel downstream. Based on this result we develop a simplified model to calculate the frequency-dependent degree of polarization, assuming that high-energy particles are injected at the shock and cool downstream. We apply our results to HBLs, blazars with the maximum of their synchrotron output at UV-soft X-ray energies. While in the optical band the predicted degree of polarization is low, in the X-ray emission it can ideally reach 50 per cent, especially during active/flaring states. The comparison between measurements in the optical and in the X-ray band made during active states (feasible with the plannedIXPEsatellite) is expected to provide valuable constraints on the dissipation and acceleration processes.
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影响因子：
4.9
作者：
Begelman, MC
通讯作者：
Begelman, MC
影响因子：
6.5
作者：
Hovatta, T.;Lindfors, E.;Pursimo, T.
通讯作者：
Pursimo, T.
PKS 2155−304 中的粒子加速度和磁场结构：光学偏振观测
DOI：
10.1111/j.1365-2966.2010.17236.x
发表时间：
2010
影响因子：
4.8
作者：
U. D. Almeida;M. Ward;T. Dominici;Z. Abraham;Gabriel A. P. Franco;M. Daniel;P. Chadwick;C. Boisson
通讯作者：
C. Boisson
相对论喷流扭结不稳定性引起的耀变体偏振旋转模型
DOI：
10.3390/galaxies5040064
发表时间：
2017
期刊：
arXiv: High Energy Astrophysical Phenomena
影响因子：
--
作者：
K. Nalewajko
通讯作者：
K. Nalewajko
影响因子：
4.8
作者：
S. Komissarov;S. Falle
通讯作者：
S. Komissarov;S. Falle