arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2004.07727astro-ph.HE
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潮汐破裂事件中的吸积盘风:紫外谱线作为方向指示

Accretion Disc Winds in Tidal Disruption Events: Ultraviolet Spectral Lines as Orientation Indicators

Edward J. Parkinson, Christian Knigge, Knox S. Long, James H. Matthews, Nick Higginbottom, Stuart A. Sim, Henrietta A. Hewitt

摘要:

一些潮汐扰动事件(TDEs)在其静止帧紫外(UV)光谱中表现出蓝移的宽吸收线(BALs),而另一些则表现出宽发射线(BELs)。在类星体和吸积的白矮星中也观察到类似的现象,可以解释为吸积盘风中与线形成相关的取向效应。我们提出了一个国家的最先进的蒙特卡罗电离和辐射转移代码产生的光盘和风托管TDEs的合成紫外光谱。我们的模型涵盖了广泛的盘式风的几何形状和运动学。这样的风自然地复制BALs和BELs。一般来说,视线看向风锥优先产生BALs,而其他方向优先产生BELs。我们还研究了风聚集和hoc处理的丰度对观测光谱的影响。clusterical风往往会产生更强的紫外线发射和吸收线,因为聚集增加了发射措施和相关离子物种的丰度,后者通过减少流出的电离状态。采用hoc处理丰度的主要效应是光谱中C~{ \sc iv}~1550~ CN ~的减弱和N \textsc{v} ~1240~ CN ~的增强。我们的结论是线形成的吸积盘风是一个很有前途的机制,用于解释不同的紫外光谱的TDEs。如果这是正确的,那么BAL和BEL TDE的相对数量可以用于估计流出的覆盖因子。这项工作中的模型可在网上公开获取,并应要求提供。

英文摘要:

Some tidal disruption events (TDEs) exhibit blueshifted broad absorption lines (BALs) in their rest-frame ultraviolet (UV) spectra, while others display broad emission lines (BELs). Similar phenomenology is observed in quasars and accreting white dwarfs, where it can be interpreted as an orientation effect associated with line formation in an accretion disc wind.We propose and explore a similar unification scheme for TDEs. We present synthetic UV spectra for disc and wind-hosting TDEs, produced by a state-of-the-art Monte Carlo ionization and radiative transfer code. Our models cover a wide range of disc wind geometries and kinematics. Such winds naturally reproduce both BALs and BELs. In general, sight lines looking into the wind cone preferentially produce BALs, while other orientations preferentially produce BELs. We also study the effect of wind clumping and CNO-processed abundances on the observed spectra. Clumpy winds tend to produce stronger UV emission and absorption lines, because clumping increases both the emission measure and the abundances of the relevant ionic species, the latter by reducing the ionization state of the outflow. The main effect of adopting CNO-processed abundances is a weakening of C~{\sc iv}~1550~Å~ and an enhancement of N \textsc{v}~1240~Å~ in the spectra. We conclude that line formation in an accretion disc wind is a promising mechanism for explaining the diverse UV spectra of TDEs. If this is correct, the relative number of BAL and BEL TDEs can be used to estimate the covering factor of the outflow. The models in this work are publicly available online and upon request.

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