测试仙后座A中$^{44}$Ti的前超新星贡献
Testing a Pre-Supernova Contribution to $^{44}$Ti in Cassiopeia A
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中文总结 AI 辅助
本研究结合NuSTAR和XRISM观测，检验仙后座A中$^{44}$Ti的前超新星壳层合并贡献，发现其可占总量约一半，表明前超新星核合成与爆炸燃烧共同作用。
中文摘要 AI 辅助
仙后座A中的放射性同位素$^{44}$Ti一直被用作核心坍缩超新星爆炸中最内层抛射物和爆炸不对称性的示踪剂。然而，最近的恒星演化模型表明，在爆炸前氧-碳（O-C）壳层合并过程中也可能合成大量的$^{44}$Ti，这一过程被认为是仙后座A前身星所经历的。我们通过将NuSTAR对$^{44}$Ti空间和运动学分布的测量与X射线和红外抛射物诊断相结合，研究了这一前超新星贡献。低和中等速度的$^{44}$Ti成分与O层示踪剂的关联比与激波加热的富铁物质的关联更紧密。如果与O层示踪剂相关的$^{44}$Ti是在核心坍缩前合成的，其贡献可达约$7\times10^{-5}~M_\odot$，约占总量的二分之一。我们发现，在具有比标准一维恒星演化计算更高的吞噬率和对流速度的O-C壳层合并模型中，可以产生这一数量的$^{44}$Ti。用XRISM测量的稳定Fe族丰度比提供了对爆炸贡献的额外约束，因为具有较大$^{44}$Ti产额的三维模型倾向于预测Ti/Fe和Mn/Cr比值高于观测值。这些结果表明，前超新星壳层合并核合成和爆炸燃烧都对观测到的$^{44}$Ti有贡献。
英文摘要
The radioactive isotope $^{44}$Ti in Cassiopeia A has been used as a tracer of the innermost ejecta and explosion asymmetries in core-collapse supernova explosions. However, recent stellar-evolution models suggest substantial $^{44}$Ti may also be synthesized prior to explosion during oxygen-carbon (O-C) shell mergers, a process proposed for the Cas A progenitor. We investigate this pre-supernova contribution by combining NuSTAR measurements of the spatial and kinematic distribution of $^{44}$Ti with X-ray and infrared ejecta diagnostics. The low- and intermediate-velocity $^{44}$Ti components are more closely associated with O-layer tracers than with shocked Fe-rich material. If the $^{44}$Ti associated with the O-layer tracers was synthesized prior to core collapse, it could contribute up to $\sim7\times10^{-5}~M_\odot$, about half of the total. We find that this amount of $^{44}$Ti can be produced in O-C shell-merger models with ingestion rates and convective velocities higher than those in standard one-dimensional stellar-evolution calculations. Stable Fe-group abundance ratios measured with XRISM provide an additional constraint on the explosive contribution, as three-dimensional models with larger $^{44}$Ti yields tend to predict Ti/Fe and Mn/Cr ratios above the observed values. These results suggest that both pre-supernova shell-merger nucleosynthesis and explosive burning contribute to the observed $^{44}$Ti.
发表机构
- Meiji University（明治大学）
- University of Victoria（维多利亚大学）
- Naval Research Laboratory（海军研究实验室）
- Kyoto University（京都大学）
- The University of Tokyo（东京大学）
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