Implications of Dramatic Broad Absorption Line Variability in the Quasar FBQS J1408+3054
Patrick B. Hall, Konstantin Anosov, R. L. White, W. N. Brandt, M. D. Gregg, R. R. Gibson, R. H. Becker, D. P. Schneider
备注：
Final version to appear in MNRAS: references added and factor of 2 underestimate of accretion disk size corrected, resulting in absorber constrained to be somewhat closer to the black hole. For an animated gif showing the spectral evolution of the broad absorption line troughs in this quasar, see http://www.yorku.ca/phall/film19952009.gif
We have observed a dramatic change in the spectrum of the formerly heavily absorbed `overlapping-trough' iron low-ionization broad absorption line (FeLoBAL) quasar FBQS J1408+3054. Over a time span of between 0.6 to 5 rest-frame years, the Mg II trough outflowing at 12,000 km/s decreased in equivalent width by a factor of two and the Fe II troughs at the same velocity disappeared. The most likely explanation for the variability is that a structure in the BAL outflow moved out of our line of sight to the ultraviolet continuum emitting region of the quasar's accretion disk. Given the size of that region, this structure must have a transverse velocity of between 2600 km/s and 22,000 km/s. In the context of a simple outflow model, we show that this BAL structure is located between approximately 5800 and 46,000 Schwarzschild radii from the black hole. That distance corresponds to 1.7 to 14 pc, 11 to 88 times farther from the black hole than the H-beta broad-line region. The high velocities and the parsec-scale distance for at least this one FeLoBAL outflow mean that not all FeLoBAL outflows can be associated with galaxy-scale outflows in ultraluminous infrared galaxies transitioning to unobscured quasars. The change of FBQS J1408+3054 from an FeLoBAL to a LoBAL quasar also means that if (some) FeLoBAL quasars have multiwavelength properties which distinguish them from HiBAL quasars, then some LoBAL quasars will share those properties. Finally, we extend previous work on how multiple-epoch spectroscopy of BAL and non-BAL quasars can be used to constrain the average lifetime of BAL episodes (currently >60 rest-frame years at 90% confidence).
Strong Variability of Overlapping Iron Broad Absorption Lines in Five Radio-selected Quasars
利用首次亮类星体巡天（FBQS）和斯隆数字巡天（SDSS）的存档数据以及我们自己获得的数据，研究了28个均匀射电选择的宽吸收线（BALs）在类星体静止坐标系中的变化，时间尺度为$\sim 1-10$年。令人惊讶的是，5个表现出强烈变化的类星体都属于重叠铁低电离BAL（OFeLoBAL）类星体的一个特殊子类，而其他4个非重叠铁低电离BAL（non-OFeLoBALs）类星体除了1个光学深度变化较弱的情况外，其余都是不变的。同时，我们还发现了该BAL类星体中高电离和低电离BALs的6种典型变化。光电离模型表明，OFeLoBALs形成在一个相对密集的（$n_e>10^6$ cm $^{-3}$）流出的距离从subparsec到几十秒差距的连续源。它们与那些非OFeLoBALs不同，后者可能是由低密度气体产生的，位于数百到数千秒差距的距离。因此，OFeLoBAL和非OFeLoBAL，即，具有或不具有强BAL变化的FeLoBALs可能代表了Fe II吸收的双峰性，前者位于活动星系核环境中，而不是宿主星系。我们认为，高密度和小距离是OFeLoBALs产生的必要条件。正如文献中所建议的，强BAL变化可能是由于BAL区域的覆盖因子的变化引起的云过境视线，而不是电离变化。
On time variability and other complications in studying the UV broad absorption lines of quasars: results from numerical simulations of radiation driven disk winds
HST Spectral Observations near the He II Ly-alpha Break: Implications for He II Reionization
能够研究IGM He II的类星体非常罕见，因为它们必须沿着没有大量氢吸收的视线处于高红移，但最近的工作显着扩大了已知的此类类星体的数量。我们分析了24个来自HST的高红移（z=3.1-3.9）低分辨率He II类星体的光谱，发现它们的He II Gunn-Peterson槽表明排除了非常早和非常晚的再电离模型，支持z~3的再电离红移。虽然数据的质量是不足以揭示细节，如预期的红移演变的氦不透明度，我们得到的第一个合奏措施的氦不透明度在高红移平均在许多视线：τ =4.90在z~3.3。我们还发现，从He II再电离开始观察IGM红翼吸收是非常困难的，但取决于再电离的红移和电离区的大小，用当前一代的紫外光谱仪在某些物体中可能这样做。
我们提出了多个分光偏振观测附近的Ia型超新星SN 2011 fe在M101，获得之前，期间和之后的最大视亮度的时间。SN 2011 fe在连续谱线和强吸收线上都表现出随时间变化的极化。在所有的历元，红色波长表现出0.2%-0.4%的连续偏振度，可能表明电子散射光球的持久不对称性。然而，跨Si II 6355吸收线的偏振度从一个时期到另一个时期变化很大。在最大值之前，Si II 6355在与偏振连续区相同的位置角（PA）处显示出增强的偏振。然而，在接近最大值的两个时期，Si II 6355的吸收具有较低的偏振度，其PA与连续谱相差90度。在最大值之后，吸收特征具有与相邻连续谱相同的偏振度和PA。蓝色的另一个吸收特征（Si II 5051或与Fe II线的混合物）显示出定性的类似变化，尽管这些变化在时间上转移到更早的时期。这种行为类似于宽吸收线类星体中的现象，在宽吸收线类星体中，吸收特征中的偏振被解释为吸收一些非偏振连续通量的线。这种行为，随着90度的偏移的偏振PA随时间的推移，意味着一个时间依赖的大尺度的不对称性的爆炸。
