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arXiv 2006.16231astro-ph.HEastro-ph.COastro-ph.SR
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磁星振荡产生的快速射电暴串

Fast Radio Burst Trains from Magnetar Oscillations

Zorawar Wadiasingh, Cecilia Chirenti

摘要:

在磁星巨耀斑尾部出现的准周期振荡最初被解释为中子星(NS)地壳的扭转振荡,最近被描述为全球核+地壳扰动。类似的频率也存在于高信噪比的磁星短爆发中。在磁星中,磁场的扰动强烈耦合到NS地壳,而不管短脉冲的触发机制如何。对于与磁星短暴相关的快速射电暴(FRB)的低空磁星模型,如低扭曲模型,地壳振荡可能与环绕短暴事件中的额外射电暴相关(如最近对SGR 1935+2154的建议)。由于大的河外体积探测宽场无线电瞬变设施,这提供了研究NS地壳利用样本远多于银河系的高能磁星爆发的统计数据的子突发结构或集群列车的FRB的前景。我们探讨了区分NS状态方程模型与越来越大的未来FRB观测集的前景。较低的$l$数本征模(对应于$\sim5-50$ ms的FRB时间间隔)可能比高$l$模更不容易受到与NS地壳物理、磁场和阻尼相关的系统效应的混淆。它们可能在实用性方面更有前途,也可能证实FRB来自成熟磁星的模型。未来对这些信号的观测特征也可以确定它们是否可以作为宇宙学的“标准振荡器”来限制红移,或者当可靠的红移可用时,可以用来限制FRB产生的磁星的质量。

英文摘要:

Quasi-periodic oscillations inferred during rare magnetar giant flare tails were initially interpreted as torsional oscillations of the neutron star (NS) crust, and have been more recently described as global core+crust perturbations. Similar frequencies are also present in high signal-to-noise magnetar short bursts. In magnetars, disturbances of the field are strongly coupled to the NS crust regardless of the triggering mechanism of short bursts. For low-altitude magnetospheric magnetar models of fast radio bursts (FRBs) associated with magnetar short bursts, such as the low-twist model, crustal oscillations may be associated with additional radio bursts in the encompassing short burst event (as recently suggested for SGR 1935+2154). Given the large extragalactic volume probed by wide-field radio transient facilities, this offers the prospect of studying NS crusts leveraging samples far more numerous than galactic high-energy magnetar bursts by studying statistics of sub-burst structure or clustered trains of FRBs. We explore the prospects for distinguishing NS equation of state models with increasingly larger future sets of FRB observations. Lower $l$-number eigenmodes (corresponding to FRB time intervals of $\sim5-50$ ms) are likely less susceptible than high-$l$ modes to confusion by systematic effects associated with the NS crust physics, magnetic field, and damping. They may be more promising in their utility, and also may corroborate models where FRBs arise from mature magnetars. Future observational characterization of such signals can also determine whether they can be employed as cosmological "standard oscillators" to constrain redshift, or can be used to constrain the mass of FRB-producing magnetars when reliable redshifts are available.

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