Kink instabilities in relativistic jets can drive quasi-periodic radiation signatures
Kink instabilities in relativistic jets can drive quasi-periodic radiation signatures
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DOI：
10.1093/mnras/staa773
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发表时间：
2020-03
影响因子：
4.8
通讯作者：
L. Dong;Haocheng Zhang;D. Giannios
中科院分区：
文献类型：
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作者：
L. Dong;Haocheng Zhang;D. Giannios
相对论喷流是从吸积黑洞中涌出的高度准直的等离子体流。它们发射时带有大量的磁能，这些磁能可以被耗散来加速非热粒子，并在更大范围内产生电磁辐射。扭结不稳定性是引发喷流磁能耗散的有效机制。虽然以前的工作已经研究了相对论喷流中扭结不稳定性增长的条件，但这些不稳定性的辐射特征还没有被详细地研究过。在这篇文章中，我们的目标是自洽地研究相对论喷流中扭结不稳定性的辐射和偏振特征。我们将大尺度相对论磁流体动力学(RMHD)模拟与磁化喷流的偏振辐射传输相结合，磁化喷流从中心引擎出现并通过周围介质传播。我们观察到喷流中央脊部的局域区表现出最强的扭结不稳定性，我们将其识别为喷流发射区。非常有趣的是，我们在发射区的光曲线上发现了准周期振荡(QPO)的特征。此外，偏振度与光曲线中的耀斑似乎是反相关的。我们的分析表明，这些QPO信号本质上是由扭结不稳定性驱动的，其中QPO的周期与扭结增长的时间尺度有关。后者相当于运动装中的几周到几个月的QPO。偏振信号为扭结不稳定性驱动的QPO提供了独特的诊断。
Relativistic jets are highly collimated plasma outflows emerging from accreting black holes. They are launched with a significant amount of magnetic energy, which can be dissipated to accelerate nonthermal particles and give rise to electromagnetic radiation at larger scales. Kink instabilities can be an efficient mechanism to trigger dissipation of jet magnetic energy. While previous works have studied the conditions required for the growth of kink instabilities in relativistic jets, the radiation signatures of these instabilities have not been investigated in detail. In this paper, we aim to self-consistently study radiation and polarization signatures from kink instabilities in relativistic jets. We combine large-scale relativistic magnetohydrodynamic (RMHD) simulations with polarized radiation transfer of a magnetized jet, which emerges from the central engine and propagates through the surrounding medium. We observe that a localized region at the central spine of the jet exhibits the strongest kink instabilities, which we identify as the jet emission region. Very interestingly, we find quasi-periodic oscillation (QPO) signatures in the light curve from the emission region. Additionally, the polarization degree appears to be anti-correlated to flares in the light curves. Our analyses show that these QPO signatures are intrinsically driven by kink instabilities, where the period of the QPOs is associated to the kink growth time scale. The latter corresponds to weeks to months QPOs in blazars. The polarization signatures offer unique diagnostics for QPOs driven by kink instabilities.