Past X-ray observations of the nearby luminous quasar PDS 456 (at $z=0.184$) have revealed a wide angle accretion disk wind (Nardini et al. 2015), with an outflow velocity of $\sim-0.25c$, as observed through observations of its blue-shifted iron K-shell absorption line profile. Here we present three new XMM-Newton observations of PDS 456; one in September 2018 where the quasar was bright and featureless, and two in September 2019, 22 days apart, occurring when the quasar was five times fainter and where strong blue-shifted lines from the wind were present. During the second September 2019 observation, three broad ($\sigma=3000$ km s$^{-1}$) absorption lines were resolved in the high resolution RGS spectrum, which are identified with blue-shifted OVIII Ly$\alpha$, NeIX He$\alpha$ and NeX Ly$\alpha$. The outflow velocity of this soft X-ray absorber was found to be $v/c=-0.258\pm0.003$, fully consistent with iron K absorber with $v/c=-0.261\pm0.007$. The ionization parameter and column density of the soft X-ray component ($\log\xi=3.4$, $N_{\rm H}=2\times10^{21}$ cm$^{-2}$) outflow was lower by about two orders of magnitude, when compared to the high ionization wind at iron K ($\log\xi=5$, $N_{\rm H}=7\times10^{23}$ cm$^{-2}$). Substantial variability was seen in the soft X-ray absorber between the 2019 observations, declining from $N_{\rm H}=10^{23}$ cm$^{-2}$ to $N_{\rm H}=10^{21}$ cm$^{-2}$ over 20 days, while the iron K component was remarkably stable. We conclude that the soft X-ray wind may originate from an inhomogeneous wind streamline passing across the line of sight and which due to its lower ionization, is located further from the black hole, on parsec scales, than the innermost disk wind.

中文翻译：

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解决 PDS 456 中的软 X 射线超快流出

过去对附近发光类星体 PDS 456（在 $z=0.184$）的 X 射线观测揭示了广角吸积盘风（Nardini 等人，2015 年），流出速度为 $\sim-0.25c$，如通过观察其蓝移的铁 K 壳吸收谱线来观察。在这里，我们展示了 PDS 456 的三个新的 XMM-牛顿观测；一次发生在 2018 年 9 月，类星体明亮且没有特征；另一次发生在 2019 年 9 月，相隔 22 天，发生在类星体暗淡五倍并且存在强烈的风蓝移线时。在 2019 年 9 月的第二次观测中，高分辨率 RGS 光谱中解析出三个宽 ($\sigma=3000$ km s$^{-1}$) 吸收线，​​这些吸收线被识别为蓝移的 OVIII Ly$\alpha$ , NeIX He$\alpha$ 和 NeX Ly$\alpha$。发现这种软 X 射线吸收器的流出速度为 $v/c=-0.258\pm0.003$，与铁 K 吸收器完全一致，$v/c=-0.261\pm0.007$。软 X 射线组分 ($\log\xi=3.4$, $N_{\rm H}=2\times10^{21}$ cm$^{-2}$) 流出的电离参数和柱密度为与铁 K 处的高电离风相比降低了大约两个数量级 ($\log\xi=5$, $N_{\rm H}=7\times10^{23}$ cm$^{-2 }$）。在 2019 年的观测之间，软 X 射线吸收体出现了很大的变化，从 $N_{\rm H}=10^{23}$ cm$^{-2}$ 下降到 $N_{\rm H}=10 ^{21}$ cm$^{-2}$ 超过 20 天，而铁 K 组分非常稳定。我们得出结论，软 X 射线风可能源自穿过视线的不均匀风流线，并且由于其较低的电离，