从XRISM对铁族元素的高分辨率光谱看3C 397的前身星和爆发机制
Progenitor and Explosion Mechanism of 3C 397 Indicated from XRISM High-resolution Spectroscopy of Fe-group Elements
AI总结：
研究通过XRISM对3C 397遗迹的观测，利用NEI等离子体模型建模其光谱，分析元素质量比，揭示东南区域元素比由电子俘获核合成解释，确定不同爆炸模型的中心密度限制，还发现视场中镍/铁质量比增强有额外中子化机制。
AI中文摘要：
我们展示了Ia型超新星遗迹3C 397的空间分辨X射线光谱，它是最有希望起源于接近钱德拉塞卡极限质量白矮星的候选者之一。在X射线成像和光谱任务（XRISM）的性能验证阶段对该遗迹进行了观测，将分辨量热计阵列的视场置于遗迹东半部。我们将分辨视场分为东南和东北区域，从每个区域为分辨和扩展探测器提取光谱。分辨光谱的特征是有来自硅、硫、氩和钙等中等质量元素（IME）的窄K壳发射线，以及来自铬、锰、铁和镍等铁族元素（IGE）的较宽K壳发射线。还检测到钛和铬的K壳发射线，且如先前观测报道的那样在东南区域局部增强。我们用具有多个温度和电离态的非平衡电离（NEI）等离子体模型同时对分辨和扩展探测器的光谱进行建模。东南区域观测到的钛/铁和铬/铁质量比只能由爆炸白矮星最内层电子俘获反应产生的富中子环境中的核合成来解释。通过将观测质量比与核合成模型预测的质量比进行比较，对于爆燃到爆轰转变模型，我们将中心密度限制为≥4.0×10^9克/立方厘米，对于纯湍流爆燃模型，限制为≥6.0×10^9克/立方厘米。另一方面，观测到的镍/铁质量比在整个视场中整体增强，这表明除电子俘获反应外还有额外的中子化机制，如更高的前身星金属丰度。
英文摘要：
We present spatially resolved X-ray spectroscopy of the Type Ia supernova remnant 3C 397, one of the most promising candidates to have originated from a white dwarf with a mass close to the Chandrasekhar limit. The remnant was observed during the performance verification phase of the X-ray Imaging and Spectroscopy Mission (XRISM), with the field of view of the Resolve calorimeter array positioned on the eastern half of the remnant. We divide the Resolve field of view into southeastern and northeastern regions and extract spectra from each region for both Resolve and Xtend. The Resolve spectra are characterized by narrow K-shell emission lines from intermediate-mass elements (IMEs) such as Si, S, Ar, and Ca, and by broader K-shell emission lines from iron-group elements (IGEs) such as Cr, Mn, Fe, and Ni. K-shell emission lines from Ti and Cr are also detected, and are found to be locally enhanced in the southeastern region, as reported in previous observations. We model the Resolve and Xtend spectra simultaneously by a non-equilibrium ionization (NEI) plasma model with multiple temperatures and ionization states. The observed mass ratios of Ti/Fe and Cr/Fe in the southeastern region can only be explained by nucleosynthesis in a neutron-rich environment produced by electron-capture reactions in the innermost layers of the exploding white dwarf. By comparing the observed mass ratios with those predicted by nucleosynthesis models, we constrain the central density to be >= 4.0 x 10^9 g cm^{-3} for the deflagration-to-detonation transition model and >= 6.0 x 10^9 g cm^{-3} for the pure turbulent deflagration model. On the other hand, the observed Ni/Fe mass ratio is globally enhanced across the field of view, suggesting an additional neutronization mechanism beyond electron-capture reactions, such as a higher progenitor metallicity.
