[论文解读] An X-Ray Burst from a Magnetar Enlightening the Mechanism of Fast Radio Bursts

M. Tavani, C. Casentini+61 more|arXiv (Cornell University)|May 25, 2020

Pulsars and Gravitational Waves Research参考文献 8被引用 38

一句话总结

论文报告由 AGILE 检测到一枚 X 射线爆发，与银河系磁星 SGR 1935+2154 的一次明亮射电爆发同時发生，从而约束 FRB–磁星连接及能量学。

ABSTRACT

Fast radio bursts (FRBs) are short (millisecond) radio pulses originating from enigmatic sources at extragalactic distances so far lacking a detection in other energy bands. Magnetized neutron stars (magnetars) have been considered as the sources powering the FRBs, but the connection is controversial because of differing energetics and the lack of radio and X-ray detections with similar characteristics in the two classes. We report here the detection by the AGILE satellite on April 28, 2020 of an X-ray burst in coincidence with the very bright radio burst from the Galactic magnetar SGR 1935+2154. The burst detected by AGILE in the hard X-ray band (18-60 keV) lasts about 0.5 seconds, it is spectrally cutoff above 80 keV, and implies an isotropically emitted energy ~ $10^{40}$ erg. This event is remarkable in many ways: it shows for the first time that a magnetar can produce X-ray bursts in coincidence with FRB-like radio bursts; it also suggests that FRBs associated with magnetars may emit X-ray bursts of both magnetospheric and radio-pulse types that may be discovered in nearby sources. Guided by this detection, we discuss SGR 1935+2154 in the context of FRBs, and especially focus on the class of repeating-FRBs. Based on energetics, magnetars with fields B ~ $10^{15}$ G may power the majority of repeating-FRBs. Nearby repeating-FRBs offer a unique occasion to consolidate the FRB-magnetar connection, and we present new data on the X-ray monitoring of nearby FRBs. Our detection enlightens and constrains the physical process leading to FRBs: contrary to previous expectations, high-brightness temperature radio emission coexists with spectrally-cutoff X-ray radiation.

研究动机与目标

• 通过呈现一个协同的 X 射线与射电爆发事件来推动 磁星–FRB 连接。
• 量化 X 射线爆发的属性与能量学，以评估与 FRB 模型的一致性。
• 讨论对重复 FRB 的影响以及场强约为 ~10^15 G 的磁星的作用。

提出的方法

• 报告与分析 AGILE 卫星在 18–60 keV 能带检测到 X 射线爆发。
• 对爆发持续时间（约 0.5 s）和谱截断在 ~80 keV 以上进行特征描述。
• 对 X 射线事件的各向同性发射能量估计为 ~10^40 erg。
• 将 X 射线爆发与来自磁星 SGR 1935+2154 的 FRB-like 射电发射联系起来的背景讨论。

实验结果

研究问题

• RQ1 磁星是否能产生与 FRB-like 射电爆发同现的 X 射线爆发，以及涉及的能量学是什么？
• RQ2 这样的多波段探测对 FRB 的发射机制意味着什么，尤其是对近距离重复 FRB？
• RQ3 基于能量学，场强约为 ~10^15 G 的磁星是否能够为大多数重复 FRB 提供能量？

主要发现

• 在 18–60 keV 能带的 X 射线爆发持续 ~0.5 s，谱在 ~80 keV 以上截断。
• X 射线爆发的各向同性发射能量为 ~10^40 erg。
• 此事件首次证明磁星可以在 FRB-like 射电爆发同时产生 X 射线爆发。
• 检测支持磁星–FRB 连接，并暗示与磁星相关的 FRB 可能同时发出磁层 X 射线爆发和射电脉冲型 X 射线爆发。
• Nearby repeating-FRBs offer a testbed to consolidate the FRB–magnetar link and motivate further X-ray monitoring.