On the covering fraction variability in an EUV mini-BAL outflow from PG 1206+459
On the covering fraction variability in an EUV mini-BAL outflow from PG 1206+459
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DOI：
10.1093/mnras/stw132
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发表时间：
2015-09
影响因子：
4.8
通讯作者：
S. Muzahid;R. Srianand;J. Charlton;M. Eracleous
中科院分区：
文献类型：
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作者：
S. Muzahid;R. Srianand;J. Charlton;M. Eracleous
我们报告了在类星体PG 1206+459光谱中NeVIII 770，780小宽吸收线（mini-BAL）的极紫外（EUV）吸收变化的第一次检测。在类星体的静止坐标系中，观测到的NeVIII双星的等效宽度（EW）在2.8个月的时间尺度上显示出约4 σ的变化。NeVIII双峰的两个成员都表现出非黑色饱和度，表明连续谱源的部分覆盖。在同一时期内，NeVIII覆盖分数从f_c = 0.59pm ~（0.05）增加到0.72pm ~（0.03）。NeVIII曲线太过饱和，以至于对吸收气体电离状态的变化不敏感。事实上，我们没有观察到任何显着的变化，在EW和/或柱密度校正后的光谱部分覆盖。因此，我们提出吸收气体的横向运动是所观察到的变化的原因。使用一个简单的过境云模型，我们估计的横向速度约为1800公里/秒。对于开普勒运动，这对应于吸收体和中央发动机之间的距离约为1.3 pc，这将吸收体置于BLR区域之外。我们进一步估计其密度约为5 × 10^6 cm^（-3），动力学光度约为10^43 - 10^44 erg/s。如此大的动力学功率表明，通过EUV线检测到的外流是活动星系核反馈的潜在主要贡献者。
We report on the first detection of extreme-ultraviolet (EUV) absorption variability in the NeVIII 770,780 mini-broad absorption line (mini-BAL) in the spectrum of the quasar (QSO) PG 1206+459. The observed equivalent width (EW) of the NeVIII doublet show a ~4 sigma variation over a timescale of 2.8 months in the QSO's rest-frame. Both members of the NeVIII doublet exhibit non-black saturation, indicating partial coverage of the continuum source. An increase in the NeVIII covering fraction from f_c = 0.59\pm0.05 to 0.72\pm0.03 is observed over the same period. The NeVIII profiles are too highly saturated to be susceptible to changes in the ionization state of the absorbing gas. In fact, we do not observe any significant variation in the EW and/or column density after correcting the spectra for partial coverage. We, thus, propose transverse motions of the absorbing gas being the cause of the observed variability. Using a simple model of a transiting cloud we estimate a transverse speed of ~1800 km/s. For Keplerian motion, this corresponds to a distance between the absorber and the central engine of ~1.3 pc, which places the absorber just outside the BLR region. We further estimate a density of ~5\times10^6 cm^(-3) and a kinetic luminosity of ~10^43 - 10^44 erg/s. Such large kinetic powers suggest that outflows detected via EUV lines are potentially major contributors to AGN feedback.