钱德拉与XRISM观测仙后座A中铁抛射物的三维膨胀
Three-Dimensional Expansion of Iron Ejecta in Cassiopeia A with Chandra and XRISM
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中文总结 AI 辅助
本研究结合Chandra与XRISM数据，推导仙后座A铁抛射物三维速度图，发现其整体向外膨胀，东南部速度最高，结果支持富铁与中等质量元素抛射物层反转的结论。
中文摘要 AI 辅助
测量超新星遗迹（SNRs）中抛射物的膨胀结构可为研究其爆发机制提供重要信息。我们结合钱德拉（Chandra）自行测量与XRISM多普勒测量，推导了银河系最年轻的核心坍缩超新星遗迹之一仙后座A（Cas A）中发射铁K线的抛射物的近似区域平均三维速度图。自行测量采用光流法完成。研究发现，发射铁K线的抛射物除西部区域外整体向外膨胀，投影速度最高达约4580 km/s；结合自行与多普勒测量，东南部抛射物的三维速度最高，达5160±320 km/s，该速度超过硅、硫等中等质量元素（IMEs）的测量值，且对应抛射物的视线方向速度弥散相对较小。这些结果与此前提出的富铁和富中等质量元素抛射物层反转的结论大致吻合。西部区域出现的表观向内运动或新铁K线发射成分，可能反映了与周围致密物质的相互作用，但当前数据无法在这些可能性间做出唯一区分，也无法确定其物理起源。
英文摘要
Measurement of the expansion structure of ejecta in supernova remnants (SNRs) provides important information about their explosion mechanism. We combine Chandra proper-motion measurements with XRISM Doppler measurements to derive an approximate, region-averaged three-dimensional velocity map of the Fe-K-emitting ejecta in Cassiopeia A (Cas A), one of the youngest Galactic core-collapse SNRs. Proper motions were measured using the optical flow method. We find that the Fe-K-emitting ejecta expand predominantly outward, except in the western region, with projected velocities of up to ~4580 km/s. The southeastern ejecta exhibit the highest three-dimensional velocity, reaching 5160+-320 km/s, based on the combined proper-motion and Doppler measurements. This velocity exceeds those measured for intermediate-mass elements (IMEs) such as Si and S, and the corresponding ejecta exhibit a relatively small line-of-sight velocity dispersion. These results are broadly consistent with the previously suggested inversion between the Fe-rich and IME-rich ejecta layers. The apparent inward motion or emergence of a new Fe-K emission component in the western region may reflect interaction with dense surrounding material, although the present data do not allow us to distinguish uniquely between these possibilities or to determine their physical origin.
