发表机构
Meiji University; Kyoto University（明治大学; 京都大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
利用钱德拉X射线观测和主成分分析，发现仙后座A富氧抛射物成分空间异质，反映前身星晚期壳层燃烧混合的不对称性，且部分结构在爆炸后幸存。
AI 中文摘要
晚期的壳层相互作用，包括壳层合并，可以在核坍缩之前将物质混合穿过相邻的燃烧壳层，并在静水压的富氧层中印刻下化学上不均匀的结构。这种不均匀性是否能在爆炸中幸存下来并在由此产生的超新星残骸中保持可观测性，目前尚不清楚。我们利用钱德拉X射线深场观测研究了仙后座A中富氧抛射物的空间和成分结构。对窄带图像的主成分分析揭示了富氧抛射物跨越一个从富Ne到富NeSi再到富O/Si物质的成分序列。对20个代表性区域的空间分辨光谱证实了Ne和Mg在朝向富O/Si成分方向上的系统性贫化。值得注意的是，富O/Si抛射物在从O到Ca的广泛元素范围内的成分，同时被17-20倍太阳质量的一维前超新星模型中经历了强壳层合并诱发的燃烧和混合的O层物质很好地再现。相比之下，富Ne抛射物保留了显著更高的Ne和Mg丰度，类似于加工程度较低的O壳层物质。这些化学上不同的成分在残骸尺度上空间分离，富Ne抛射物优先集中在北部，而富O/Si抛射物在东南部更为突出。我们的结果表明，仙后座A的前身星中晚期的壳层燃烧和混合在空间上是异质的。具有不同燃烧历史的抛射物在残骸尺度上的分布进一步表明，这种不对称的前超新星结构的一部分可能在爆炸中幸存下来，并仍然印刻在现今的残骸中。
英文摘要
Late-stage shell interactions, including shell mergers, can mix material across adjacent burning shells and imprint chemically inhomogeneous structures in the hydrostatic O-rich layers before core collapse. Whether such inhomogeneities survive the explosion and remain observable in the resulting supernova remnant is not well understood. We investigate the spatial and compositional structure of the O-rich ejecta in Cassiopeia A using deep Chandra X-ray observations. Principal component analysis of narrow-band images reveals O-rich ejecta spanning a compositional sequence from Ne-rich through NeSi-rich to O/Si-rich material. Spatially resolved spectroscopy of 20 representative regions confirms systematic depletion of Ne and Mg toward the O/Si-rich component. Notably, the composition of the O/Si-rich ejecta over a broad elemental range from O to Ca is simultaneously well reproduced by O-layer material in 17-20 $M_\odot$ one-dimensional presupernova models that experienced strong shell-merger-induced burning and mixing. In contrast, the Ne-rich ejecta retain substantially higher Ne and Mg abundances and resemble less strongly processed O-shell material. These chemically distinct components are spatially segregated on remnant-wide scales, with Ne-rich ejecta preferentially concentrated toward the north and O/Si-rich ejecta more prominent in the southeast. Our results suggest that late-stage shell burning and mixing in the progenitor of Cassiopeia A were spatially heterogeneous. The remnant-wide distribution of ejecta with different burning histories further indicates that part of this asymmetric presupernova structure may have survived the explosion and remains imprinted in the present-day remnant.
Comments13 pages, 8 figures; submitted to PASJ
