使用LOFAR的脉冲星闪烁研究：II。PSR J0826 +2637与LOFAR和NenuFAR的双频散射研究
Pulsar Scintillation Studies with LOFAR: II. Dual-frequency scattering study of PSR J0826+2637 with LOFAR and NenuFAR
摘要：
射电脉冲星辐射的星际散射（ISS）可以作为电离星际介质（IISM）的探测器，并在脉冲星计时实验中造成干扰。两种类型的ISS现象（强度闪烁和脉冲展宽）是由小尺度（< 0.01 AU）的电子密度波动引起的。理论预测这些是相关的，并且两者都被广泛用于研究IISM的性质。更大的尺度（$\sim$ 1- 100\，AU）引起可测量的色散变化，这些变化可以与国际空间站的观测结果相关联，以估计非常宽尺度范围内的波动谱。IISM测量通常可以通过具有Kolmogorov（$-11/3$）谱指数的电子密度的均匀幂律空间谱来建模。在这里，我们的目的是测试的有效性使用柯尔莫哥洛夫指数PSR~ J 0826 +2637。我们这样做使用的强度闪烁，脉冲展宽和色散的变化在一个很宽的分数带宽（20 - 180 MHz）的观察。我们提出，在高频带的强度闪烁的频率依赖性匹配的期望的柯尔莫哥洛夫谱指数，但在低频带的脉冲展宽不改变，因为快速预测与此假设。我们表明，这种行为是由于在散射区域的不均匀性，具体地说，散射是由横向尺寸$\sim$ 40\，AU的区域占主导地位。然而，电子密度的功率谱从5 $\times10^{-6}$ \，AU到$\sim$ 100\，AU的空间尺度保持Kolmogorov谱指数。
英文摘要：
Interstellar scattering (ISS) of radio pulsar emission can be used as a probe of the ionised interstellar medium (IISM) and causes corruptions in pulsar timing experiments. Two types of ISS phenomena (intensity scintillation and pulse broadening) are caused by electron density fluctuations on small scales (< 0.01 AU). Theory predicts that these are related, and both have been widely employed to study the properties of the IISM. Larger scales ($\sim$1-100\,AU) cause measurable changes in dispersion and these can be correlated with ISS observations to estimate the fluctuation spectrum over a very wide scale range. IISM measurements can often be modeled by a homogeneous power-law spatial spectrum of electron density with the Kolmogorov ($-11/3$) spectral exponent. Here we aim to test the validity of using the Kolmogorov exponent with PSR~J0826+2637. We do so using observations of intensity scintillation, pulse broadening and dispersion variations across a wide fractional bandwidth (20 -- 180\,MHz). We present that the frequency dependence of the intensity scintillation in the high frequency band matches the expectations of a Kolmogorov spectral exponent but the pulse broadening in the low frequency band does not change as rapidly as predicted with this assumption. We show that this behavior is due to an inhomogeneity in the scattering region, specifically that the scattering is dominated by a region of transverse size $\sim$40\,AU. The power spectrum of the electron density, however, maintains the Kolmogorov spectral exponent from spatial scales of 5$\times10^{-6}$\,AU to $\sim$100\,AU.
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