We have conducted an extensive X-ray spectral variability study of a sample of 20 Compton-thin type II galaxies using broad band spectra from XMM-Newton, Chandra, and Suzaku. The aim is to study the variability of the neutral intrinsic X-ray obscuration along the line of sight and investigate the properties and location of the dominant component of the X-ray-obscuring gas. The observations are sensitive to absorption columns of $N_{\rm H} \sim 10^{20.5-24} {\rm cm^{-2}}$ of fully- and partially-covering neutral and/or lowly-ionized gas on timescales spanning days to well over a decade. We detected variability in the column density of the full-covering absorber in 7/20 sources, on timescales of months-years, indicating a component of compact-scale X-ray-obscuring gas lying along the line of sight of each of these objects. Our results imply that torus models incorporating clouds or overdense regions should account for line of sight column densities as low as $\sim$ a few $\times 10^{21}$ cm$^{-2}$. However, 13/20 sources yielded no detection of significant variability in the full-covering obscurer, with upper limits to ${\Delta}N_{\rm H}$ spanning $10^{21-23}$ cm$^{-2}$. The dominant absorbing media in these systems could be distant, such as kpc-scale dusty structures associated with the host galaxy, or a homogeneous medium along the line of sight. Thus, we find that overall, strong variability in full-covering obscurers is not highly prevalent in Compton-thin type IIs, at least for our sample, in contrast to previous results in the literature. Finally, 11/20 sources required a partial-covering, obscuring component in all or some of their observations, consistent with clumpy near-Compton-thick compact-scale gas.

中文翻译：

---

康普顿薄型 II 型活动星系核中的可变和非可变 X 射线吸收器

我们使用 XMM-牛顿、钱德拉和朱雀的宽带光谱对 20 个康普顿薄 II 型星系样本进行了广泛的 X 射线光谱变异性研究。目的是研究沿视线的中性本征 X 射线遮蔽的可变性，并研究 X 射线遮蔽气体的主要成分的性质和位置。观察结果对完全覆盖和部分覆盖的中性和/或低电离气体的 $N_{\rm H} \sim 10^{20.5-24} {\rm cm^{-2}}$ 的吸收柱敏感在跨越几天到十多年的时间尺度上。我们检测到 7/20 源中全覆盖吸收器的柱密度的变化，时间尺度为数月-年，表明这些物体中的每一个的视线都存在致密尺度 X 射线遮蔽气体的成分. 我们的结果意味着包含云或过密区域的环面模型应该考虑低至 $\sim$ 几个 $\times 10^{21}$ cm$^{-2}$ 的视线列密度。然而，13/20 来源没有检测到全覆盖模糊器的显着变化，上限为 ${\Delta}N_{\rm H}$ 跨越 $10^{21-23}$ cm$^{-2 }$。这些系统中的主要吸收介质可能是遥远的，例如与宿主星系相关的 kpc 级尘埃结构，或沿视线的均匀介质。因此，我们发现，与之前文献中的结果相比，至少对于我们的样本而言，全覆盖遮蔽物的强烈变异性在康普顿薄型 II 中并不十分普遍。最后，11/20 的来源要求在他们的全部或部分观察中部分覆盖、遮蔽成分，