Scattering variability detected from the circumsource medium of FRB 20190520B
Scattering variability detected from the circumsource medium of FRB 20190520B
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从 FRB 20190520B 的环境介质中检测到的散射变异性
DOI：
10.1093/mnras/stac3547
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发表时间：
2022
影响因子：
4.8
通讯作者：
Anna-Thomas, Reshma
中科院分区：
文献类型：
--
作者：
Ocker, Stella Koch;Cordes, James M.;Chatterjee, Shami;Li, Di;Niu, Chen-Hui;McKee, James W.;Law, Casey J.;Anna-Thomas, Reshma
快速射电爆发（FRB）是毫秒级的射电瞬变，其起源主要是河外，可能涉及高度磁化的致密天体。快速射电暴会因沿视线的电离气体中亚秒差距尺度的电子密度波动而经历多径传播或散射。散射观测已经定位了 FRB 宿主星系内的等离子体结构，探测了银河系和河外湍流，并限制了 FRB 红移。散射还会抑制 FRB 检测并使观察到的 FRB 群体产生偏差。我们报告了从重复的 FRB 20190520B 中检测到的散射时间，这些时间在几分钟到几天的时间尺度上变化高达 2 倍或更多。在一个值得注意的案例中，在 1.45 GHz 下，散射时间在 2.9 分钟内从 7.9 ± 0.4 毫秒变化到小于 3.1 毫秒（置信度）。爆发之间或与色散和旋转测量变化之间的散射时间似乎不相关。散射变化可归因于环境介质中动态的、不均匀的等离子体，并且在蟹状脉冲星中也观察到了类似的变化。在这种情况下，散射的频率依赖性可能偏离用于测量散射的典型幂律。因此，即使是那些散射不明显的快速射电暴，也可以检测到类似的变化，从而为快速射电暴环境中的小规模过程提供独特的探测。
Fast radio bursts (FRBs) are millisecond-time-scale radio transients, the origins of which are predominantly extragalactic and likely involve highly magnetized compact objects. FRBs undergo multipath propagation, or scattering, from electron density fluctuations on sub-parsec scales in ionized gas along the line of sight. Scattering observations have located plasma structures within FRB host galaxies, probed Galactic and extragalactic turbulence, and constrained FRB redshifts. Scattering also inhibits FRB detection and biases the observed FRB population. We report the detection of scattering times from the repeating FRB 20190520B that vary by up to a factor of 2 or more on minutes to days-long time-scales. In one notable case, the scattering time varied from 7.9 ± 0.4 ms to less than 3.1 ms (confidence) over 2.9 min at 1.45 GHz. The scattering times appear to be uncorrelated between bursts or with dispersion and rotation measure variations. Scattering variations are attributable to dynamic, inhomogeneous plasma in the circumsource medium, and analogous variations have been observed from the Crab pulsar. Under such circumstances, the frequency dependence of scattering can deviate from the typical power law used to measure scattering. Similar variations may therefore be detectable from other FRBs, even those with inconspicuous scattering, providing a unique probe of small-scale processes within FRB environments.