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arXiv 2005.12048astro-ph.HE
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与SGR 1935+2154 X射线爆发相关的FRB 200428磁星-小行星碰撞模型

A Magnetar-Asteroid Impact Model for FRB 200428 Associated with an X-ray Burst from SGR 1935+2154

Z. G. Dai

摘要:

最近,一个非常明亮的快速射电暴(FRB)200428与两个亚毫秒脉冲被发现来自银河系磁星SGR 1935+2154的方向,和一个X射线爆发(XRB)的对应物被同时检测到。这些观察有利于基于磁星的走廊驱动模型。在这封信中,我们提出了与SGR 1935+2154的XRB相关的FRB 200428的不同模型,其中具有高固有速度的磁星遇到质量为$\sim10^{20}\,$ g的小行星。这颗在恒星引力场中坠落的小行星首先可能被潮汐分裂成大量半径为$\sim {\rm a\,\,few}$ × $10^{10}\,$ cm的碎片,然后被超强磁场减速到Alfv $\acute{\rm e}$ n半径附近,同时两个质量为$\sim 10^{17}\,$ g的主要碎片穿过磁场线产生两个FRB 200428脉冲。整个小行星最终沿着磁力线吸积到两极,撞击恒星表面,产生一个光子-e $^\pm$对火球,最初被困在恒星磁层中,并进一步导致XRB。我们表明,这种引力供电模型可以解释所有观察到的功能自洽。

英文摘要:

Very recently, an extremely bright fast radio burst (FRB) 200428 with two sub-millisecond pulses was discovered to come from the direction of the Galactic magnetar SGR 1935+2154, and an X-ray burst (XRB) counterpart was detected simultaneously. These observations favor magnetar-based interior-driven models. In this Letter, we propose a different model for FRB 200428 associated with an XRB from SGR 1935+2154, in which a magnetar with high proper velocity encounters an asteroid of mass $\sim10^{20}\,$g. This infalling asteroid in the stellar gravitational field is first possibly disrupted tidally into a great number of fragments at radius $\sim {\rm a\,\,few}$ times $10^{10}\,$cm, and then slowed around the Alfv$\acute{\rm e}$n radius by an ultra-strong magnetic field and in the meantime two major fragments of mass $\sim 10^{17}\,$g that cross magnetic field lines produce two pulses of FRB 200428. The whole asteroid is eventually accreted onto the poles along magnetic field lines, impacting the stellar surface, creating a photon-e$^\pm$ pair fireball trapped initially in the stellar magnetosphere, and further leading to an XRB. We show that this gravitationally-powered model can interpret all of the observed features self-consistently.

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