Ia型超新星中的丰度分层——VIII. 03fg-like SN 2012dn：双简并并合解释
Abundance Stratification in Type Ia Supernovae -- VIII. The 03fg-like SN\,2012dn: a double-degenerate merger interpretation
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中文总结 AI 辅助
通过丰度层析研究特殊Ia型超新星SN 2012dn，发现其总抛射物质量1.66倍太阳质量且含氧，支持双简并CO–CO白矮星并合解释，并可能由弱相互作用补充光度。
中文摘要 AI 辅助
本文对特殊Ia型超新星SN 2012dn进行了详细的丰度层析研究。尽管其峰值光度正常，但它保留了早期超钱德拉塞卡（03fg-like）特征：弱的Fe III、窄的中等质量元素（IME）、持续存在的碳，以及缺乏高速Ca II特征。其星云谱异常微弱，这是由于从最大光度后约60天开始出现的灰暗化效应，并显示出在Ia型超新星中罕见的[O I]发射。虽然钱德拉塞卡质量密度分布能重现光球阶段，但在晚期失效。[O I]发射需要额外的低速质量，这意味着总抛射物质量为1.66倍太阳质量，其中包括0.33倍太阳质量的氧（其中0.1倍太阳质量位于核心）。56Ni质量估计为0.45–0.49倍太阳质量，该范围由星云阶段应用的灰消光校正的不确定性决定，且其本身不足以解释峰值光度。稳定铁局限于中间层，在核心和外层抛射物中均不存在，后者表明前身星金属丰度低于太阳。硅和硫遍布整个抛射物，而碳延伸至速度约6000 km/s处。这些性质支持双简并CO–CO白矮星并合情景。剩余的光度不足可能由与低质量、富碳星周壳层的弱相互作用提供的额外能量输入来解释。
英文摘要
A detailed study using abundance tomography of SN 2012dn, a peculiar Type Ia supernova, is presented. Despite exhibiting a normal peak luminosity, it retains early-phase super-Chandrasekhar (03fg-like) characteristics: weak Fe III, narrow intermediate-mass element (IME), persistent carbon, and the absence of high-velocity Ca II features. Its nebular spectrum is unusually faint due to grey dimming beginning $\sim$60 days after maximum and shows [O I] emission, rare in SNe Ia. While a Chandrasekhar-mass density profile reproduces the photospheric phase, it fails at late times. The [O I] emission requires additional low-velocity mass, implying a total ejecta mass of $1.66$ $M_\odot$, including $0.33$ $M_\odot$ of oxygen (with $0.1$ $M_\odot$ in the core). The $^{56}$Ni mass is estimated to be $0.45$--$0.49$ $M_\odot$, a range set by uncertainties in the grey-extinction correction applied at the nebular phase, and is insufficient on its own to account for the peak luminosity. Stable iron is confined to intermediate layers and absent from both the core and outer ejecta, the latter indicating sub-solar progenitor metallicity. Silicon and sulfur span the full ejecta, while carbon extends down to $v \sim 6000$ ${\rm km,s^{-1}}$. These properties favour a double-degenerate CO--CO white dwarf merger scenario. The remaining luminosity deficit may be explained by additional energy input from a weak interaction with a low-mass, carbon-rich circumstellar shell.
发表机构
- Astrophysics Research Institute, Liverpool John Moores University（利物浦约翰摩尔斯大学天体物理研究所）
- Max-Planck Institut für Astrophysik（马克斯·普朗克天体物理研究所）
- Leibniz Supercomputing Centre (LRZ) of the BAdW（巴伐利亚科学院莱布尼茨超级计算中心）
- Institute for Astronomy, University of Hawai’i at Manoa（夏威夷大学马诺阿分校天文学研究所）
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