天鹅座圈东北缘的钱德拉观测
Chandra Observations of the Northeastern Rim of the Cygnus Loop
摘要：
我们目前的结果从空间分辨光谱分析的东北（NE）边缘的天鹅座圈超新星遗迹（SNR）的基础上两个钱德拉观测。一个指向包括最近的朱雀观测发现的北部最外层丰度增强的区域，而另一个指向位于天鹅座环东北边缘的“正常”丰度区域。钱德拉优越的空间分辨能力使我们能够揭示丰度增强区集中在激波阵面后面约200”厚的区域。我们确认绝对金属丰度（即，相对于H）以及金属之间的丰度比与太阳值的丰度比在约2倍内一致。此外，我们发现，在该地区的排放措施逐渐减少的冲击波前。这些功能与船帆座SNR周围的喷出物碎片，这使我们相信，丰富的增强是不太可能由于富含金属的喷出物形成对比。我们认为该区域的等离子体起源于星际介质。在“正常”的丰度区域，我们确认，丰度耗尽太阳值的一个因素约为5，这是不预期的ISM天鹅座圈周围。在我们的模型拟合中引入非热辐射并不能自然地解决丰度-贫化问题。枯竭的起源仍然是一个悬而未决的问题。
英文摘要：
We present results from spatially resolved spectral analyses of the northeastern (NE) rim of the Cygnus Loop supernova remnant (SNR) based on two Chandra observations. One pointing includes northern outermost abundance-enhanced regions discovered by recent Suzaku observations, while the other pointing is located on regions with "normal" abundances in the NE rim of the Cygnus Loop. The superior spatial resolving power of Chandra allows us to reveal that the abundance-enhanced region is concentrated in an about 200"-thickness region behind the shock front. We confirm absolute metal abundances (i.e., relative to H) as well as abundance ratios between metals are consistent with those of the solar values within a factor of about 2. Also, we find that the emission measure in the region gradually decreases toward the shock front. These features are in contrast with those of the ejecta fragments around the Vela SNR, which leads us to believe that the abundance enhancements are not likely due to metal-rich ejecta. We suggest that the origin of the plasma in this region is the interstellar medium (ISM). In the "normal" abundance regions, we confirm that abundances are depleted to the solar values by a factor of about 5 that is not expected in the ISM around the Cygnus Loop. Introduction of non-thermal emission in our model fitting can not naturally resolve the abundance-depletion problem. The origin of the depletion still remains as an open question.
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