The supernova remnant (SNR) 3C 397 is thought to originate from a Type Ia supernova (SN Ia) explosion of a near-Chandrasekhar-mass (M _Ch) progenitor, based on the enhanced abundances of Mn and Ni revealed by previous X-ray study with Suzaku. Here we report follow-up XMM-Newton observations of this SNR, conducted with the aim of investigating the detailed spatial distribution of the Fe-peak elements. We have discovered an ejecta clump with extremely high abundances of Ti and Cr, in addition to Mn, Fe, and Ni, in the southern part of the SNR. The Fe mass of this ejecta clump is estimated to be ∼0.06 M _⊙, under the assumption of a typical Fe yield for SNe Ia (i.e., ∼0.8 M _⊙). The observed mass ratios among the Fe-peak elements and Ti require substantial neutronization that is achieved only in the innermost regions of a near-M _Ch SN Ia with a central density of ρ _c ∼ 5 10⁹ g cm⁻³, significantly higher than typically assumed for standard near-M _Ch SNe Ia (ρ _c ∼ 2 10⁹ g cm⁻³). The overproduction of the neutron-rich isotopes (e.g., ⁵⁰Ti and ⁵⁴Cr) is significant in such high-ρ _c SNe Ia, with respect to the solar composition. Therefore, if 3C 397 is a typical high-ρ _c near-M _Ch SN Ia remnant, the solar abundances of these isotopes could be reproduced by the mixture of the high- and low-ρ _c near-M _Ch and sub-M _Ch Type Ia events, with ≲20% being high-ρ _c near-M _Ch.

超新星遗迹 (SNR) 3C 397 被认为起源于近钱德拉塞卡质量 ( M _Ch ) 祖先的Ia 型超新星 (SN Ia) 爆炸，基于先前 X 射线显示的锰和镍丰度的增加跟着朱雀学习。在这里，我们报告了对该 SNR 的后续 XMM-牛顿观测，旨在研究 Fe 峰元素的详细空间分布。除了 Mn、Fe 和 Ni 之外，我们还在 SNR 的南部发现了一个具有极高丰度的 Ti 和 Cr 的喷射物团块。这个喷出物丛中的Fe的质量被估计为~0.06中号 _⊙，典型的产率的Fe的假设为Ia型超新星下（即，〜0.8中号 _⊙）。观察到的 Fe 峰元素和 Ti 之间的质量比需要大量中子化，这仅在中心密度为ρ _c ∼ 5 10 ⁹ g cm ^-3的近M _Ch SN Ia的最内部区域实现，显着高于通常假定为标准近M _Ch SNe Ia ( ρ _c ∼ 2 10 ⁹ g cm ^-3 )。富中子同位素（例如⁵⁰ Ti 和⁵⁴ Cr）的过量生产在如此高的ρ _c SNe Ia 中是显着的，相对于太阳组成而言。因此，如果 3C 397 是典型的高 ρ _c near -M _Ch SN Ia 残余物，这些同位素的太阳丰度可以通过高低- ρ _c near -M _Ch和亚M _Ch Ia 型事件的混合再现，其中≲20% 为高- ρ _c接近- M _Ch。