Relativistic fireball reprise: radio suppression at the onset of short magnetar bursts
Relativistic fireball reprise: radio suppression at the onset of short magnetar bursts
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DOI：
10.1093/mnras/sty3388
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发表时间：
2018-10
影响因子：
4.8
通讯作者：
S. Yamasaki;S. Kisaka;T. Terasawa;T. Enoto
中科院分区：
文献类型：
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作者：
S. Yamasaki;S. Kisaka;T. Terasawa;T. Enoto
越来越多的证据表明，磁星和射电暴之间可能不存在明显的区别，这意味着同时表现出射电脉动和爆发活动的中子星数量可能很大。在这种情况下，通过结合射电脉动的时间行为，可以获得对爆发机制的新见解。我们提出了一个一般模型的相对论性等离子体流出在磁星耀斑爆发的射电抑制。突然向磁层喷射磁能会产生火球等离子体，并迅速以相对论速度膨胀。这将使等离子体截止频率显著高于静止帧射频，导致无线电波的抑制。我们分析表明，任何GHz的无线电发射所产生的磁层被抑制为$\sim 100\ {\rm s}$，这取决于总的火球能量。另一方面，热辐射预计来自恒星表面上的热点（S），该热点由稠密等离子体的流入产生，这可能是短暴的起源。由于我们的假设预测射电抑制与短爆发一致，这可能是一种间接的方法，以限制短爆发在暗端的发生率，仍然没有被X射线探测器检测到。此外，来自火球光球层的超快伽马射线闪光也被认为是一个确凿的证据，尽管由于其持续时间极短，机载探测具有挑战性。最后，我们的模型被应用到无线电脉冲星与类磁星活动，PSR J1119-6127在最近的观测。快速射电爆发和等离子体透镜的可能性的影响也进行了讨论。
There is growing evidence that a clear distinction between magnetars and radio pulsars may not exist, implying the population of neutron stars that exhibit both radio pulsations and bursting activities could be potentially large. In this situation, new insights into the burst mechanism could be gained by combining the temporal behavior of radio pulsations. We present a general model for radio suppression by relativistic $e^{\pm}$ plasma outflows at the onset of magnetar flares. A sudden ejection of magnetic energy into the magnetosphere would generate a fireball plasma, which is promptly driven to expand at relativistic speed. This would make the plasma cutoff frequency significantly higher than the rest frame radio frequency, resulting in the suppression of radio waves. We analytically show that any GHz radio emission arising from the magnetosphere is suppressed for $\sim100\ {\rm s}$, depending on the total fireball energy. On the other hand, thermal radiation is expected from the hot spot(s) on the stellar surface created by an inflow of dense plasma, which could be the origin of short bursts. Since our hypothesis predicts radio suppression in coincidence with short bursts, this could be an indirect method to constrain the occurrence rate of short bursts at the faint end that remain undetected by X-ray detectors. Furthermore, ultra-fast gamma-ray flashes from the fireball photosphere is also expected as a smoking gun, although the onboard detection is challenging due to its extremely short duration $\sim\mu$s. Finally, our model is applied to the radio pulsar with magnetar-like activities, PSR J1119-6127 in light of recent observations. Implications for fast radio bursts and the possibility of plasma lensing are also discussed.