论文标题
在行星NEBULAE NGC 6886和NGC 6881中发现拉曼散布的He II $λ$ 6545
Discovery of Raman-scattered He II $λ$6545 in the Planetary Nebulae NGC 6886 and NGC 6881
论文作者
论文摘要
年轻的行星星云（PNE）保留了大量的中性物质，这些物质在以前的渐近巨型分支阶段被脱落。可以通过照亮遥远的紫外线辐射来有效地探测Young PNE中的厚H I区域，该距离可能散布在光学区域中。拉曼碎片的特征是中性区域的独特光谱示踪剂，可用于研究Young PNE中的质量损失过程。我们使用BOE（Bohyunsan观测台梯形光谱仪）对年轻pne进行高分辨率光谱，并报告发现发现了一个拉曼式的He II特征在NGC 6886和NGC 6881中的6545Å中，Raman Scatered He II在五个PNE中只发现了一个He II的纽约，该特征仅在第一个PNE中发现，并且是该公司的组成部分，该公司是由NG far，and of far，and of the He II，这是一家人，该公司的范围是，这是由far，以及该特征的组成。 6881。在两个pne中，拉曼he ii $λ6545$特征相对于He II $ \ lambda6560 $进行了红移，表明中性区域正在扩大。我们使用基于网格的蒙特卡洛代码“恒星”进行线轮廓分析，假设中性氢区的形状处于部分球形壳的形状。配置文件充满了覆盖因子的模型参数$ cf = 0.3 $，h i列密度$ n _ {\ rm hi} = 5 \ times 10^{20}〜{\ rm cm^{ - 2}} $ 6886和$ cf = 0.6 $，$ n _ {\ rm hi} = 3 \ times 10^{20}〜{\ rm cm^{ - 2}} $，和$ v _ {\ rm exp} = 30 \ rm \ rm \ rm \ rm \ rm \ km〜s^{ - 1} $ for ngc 68881 for ngc 68881，分析。
Young planetary nebulae (PNe) retain a large amount of neutral material that was shed in the previous asymptotic giant branch stage. The thick H I region in young PNe can be effectively probed by illuminating far UV radiation that may be inelastically scattered to appear in the optical region. Raman-scattered features are unique spectroscopic tracers of neutral regions that can be used to investigate the mass-loss process in young PNe. We conduct high resolution spectroscopy of young PNe using BOES (the Bohyunsan Observatory Echelle Spectrograph) and report the discovery of a Raman-scattered He II feature at 6545 Å in NGC 6886 and NGC 6881. The Raman-scattered He II features have been found in only five PNe so far, and, in particular, it is the first direct detection of an H I component in NGC 6881. The Raman He II $λ6545$ features in the two PNe are observed to be redshifted with respect to He II $\lambda6560$, indicating that the neutral regions are expanding. We perform line profile analyses using the grid-based Monte Carlo code 'STaRS' by assuming a neutral hydrogen region in the shape of a partial spherical shell expanding radially. The profiles are well fitted with the model parameters of covering factor $CF=0.3$, H I column density $N_{\rm HI} = 5 \times 10^{20}~{\rm cm^{-2}}$, and expansion speed $v_{\rm exp} = 25~\rm\ km~s^{-1}$ for NGC 6886 and $CF=0.6$, $N_{\rm HI} = 3 \times 10^{20}~{\rm cm^{-2}}$, and $v_{\rm exp} = 30\rm\ km~s^{-1}$ for NGC 6881, respectively.
