ASKAP observations of multiple rapid scintillators reveal a degrees-long plasma filament
ASKAP observations of multiple rapid scintillators reveal a degrees-long plasma filament
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DOI：
10.1093/mnras/stab139
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发表时间：
2021-01
期刊：
影响因子：
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通讯作者：
Yuanming Wang;A. Tuntsov;T. Murphy;E. Lenc;M. Walker;K. Bannister;D. Kaplan;E. Mahony
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文献类型：
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作者：
Yuanming Wang;A. Tuntsov;T. Murphy;E. Lenc;M. Walker;K. Bannister;D. Kaplan;E. Mahony
我们展示了澳大利亚平方公里阵列探路者在小时时间尺度上搜索无线电变量的结果。我们在一个30°2的区域进行了一次无目标搜索，多次10小时的观察间隔为几天到几个月，中心频率为945 MHz。我们从15分钟减模图像中发现了6个快速闪烁体，灵敏度为~ 200 μJy/beam；其中两个是极端的小时内变量，调制指数高达~ 40%，时间尺度短至数十分钟。其中5个变量在天空中呈角宽~ 1角分、角长~ 2度的线性排列，表明它们前面存在巨大的等离子体灯丝。我们从我们的源的闪烁速率的年调制中导出了这种等离子体的运动学模型，并估计了它可能的物理性质：距离为~ 4 pc，长度为~ 0.1 pc。我们在散射屏上观察到的特征与已发表的关于小时内变率起源的建议不一致，这使我们提出了一种新的观点，即潜在的现象是冷潮流。这是第一次在同一个等离子体屏幕后面检测到多个闪烁体，从而直接了解导致闪烁增强的散射介质的几何形状。
We present the results from an Australian Square Kilometre Array Pathfinder search for radio variables on timescales of hours. We conducted an untargeted search over a 30 deg2 field, with multiple 10-hour observations separated by days to months, at a central frequency of 945 MHz. We discovered six rapid scintillators from 15-minute model-subtracted images with sensitivity of ∼ 200 μJy/beam; two of them are extreme intra-hour variables with modulation indices up to ∼ 40% and timescales as short as tens of minutes. Five of the variables are in a linear arrangement on the sky with angular width ∼ 1 arcmin and length ∼ 2 degrees, revealing the existence of a huge plasma filament in front of them. We derived kinematic models of this plasma from the annual modulation of the scintillation rate of our sources, and we estimated its likely physical properties: a distance of ∼ 4 pc and length of ∼ 0.1 pc. The characteristics we observe for the scattering screen are incompatible with published suggestions for the origin of intra-hour variability leading us to propose a new picture in which the underlying phenomenon is a cold tidal stream. This is the first time that multiple scintillators have been detected behind the same plasma screen, giving direct insight into the geometry of the scattering medium responsible for enhanced scintillation.