我们展示了对CD-23 13777视线方向获得的中等高分辨率光谱的分析。CD-23 13777是一颗O9型超巨星，可用于探测与超新星遗迹W28相关的高速星际气体。在朝向CD-23 13777的星际Na I D线和Ca II H、K线中，同时观测到高速正速度和高速负速度的吸收成分。这些高速成分表现出较低的Na I/Ca II比值，表明激波溅射导致了高效的尘埃颗粒破坏。在较低速度成分中观测到的高柱密度CH+以及高CH+/CH比值，可能表明与W28相互作用的云中存在增强的湍流。朝向CD-23 13777的Na I和Ca II吸收中所见成分的最高正速度和负速度意味着，与W28相关的激波波前速度至少为150 km/s，这一数值显著高于此前大多数估计。CD-23 13777的视线非常接近一个著名的超新星遗迹与东北方向分子云的相互作用区域。该东北方向分子云表现出宽分子线发射、来自多个位置的OH脉泽发射，以及明亮的延展GeV和TeV伽马射线发射。因此，CD-23 13777的视线是探测W28与其周围致密分子气体相互作用的独特而有价值的探针。未来在紫外和可见光波段的观测将有助于更好地约束该视线方向上激波气体和宁静气体中的元素丰度、运动学和物理条件。
英文摘要：
We present an analysis of moderately high resolution optical spectra obtained for the sight line to CD-23 13777, an O9 supergiant that probes high velocity interstellar gas associated with the supernova remnant W28. Absorption components at both high positive and high negative velocity are seen in the interstellar Na I D and Ca II H and K lines toward CD-23 13777. The high velocity components exhibit low Na I/Ca II ratios, suggesting efficient grain destruction by shock sputtering. High column densities of CH+, and high CH+/CH ratios, for the components seen at lower velocity may be indicative of enhanced turbulence in the clouds interacting with W28. The highest positive and negative velocities of the components seen in Na I and Ca II absorption toward CD-23 13777 imply that the velocity of the blast wave associated with W28 is at least 150 km/s, a value that is significantly higher than most previous estimates. The line of sight to CD-23 13777 passes very close to a well-known site of interaction between the SNR and a molecular cloud to the northeast. The northeast molecular cloud exhibits broad molecular line emission, OH maser emission from numerous locations, and bright extended GeV and TeV gamma-ray emission. The sight line to CD-23 13777 is thus a unique and valuable probe of the interaction between W28 and dense molecular gas in its environs. Future observations at UV and visible wavelengths will help to better constrain the abundances, kinematics, and physical conditions in the shocked and quiescent gas along this line of sight.
Unveiling Vela -- Variability of Interstellar Lines in the Direction of the Vela Supernova Remnant III. Na D and Ca II K
2017年至2019年，南部非洲大型望远镜在船帆座超新星遗迹的方向上获得了15颗恒星的高分辨率光谱。本文讨论了星际Ca i H、K和Na i D线。特别是，线配置文件进行比较，在1993-1996年获得的Cha和Sembach的光谱分辨率的配置文件。其中10条视线显示了该视线中一个或多个组件的变化。变化包括在两次观测期间之间的二十年间径向速度的微小变化（1-2公里/秒）和（或）等效宽度的增加/减少。Ca-K线的变化比Na-D线的变化更明显。这些变化归因于超新星喷出物和周围星际介质之间相互作用所扰动的气体。典型的时间尺度可以是20-50年。如前所述，遗迹表面线剖面的小尺度变化表明，相互作用的线性尺度是目前遗迹40 pc大小的一小部分。
