SN 2021 zny：早期通量过剩与晚期氧排放相结合表明双白矮星合并事件
SN 2021zny: an early flux excess combined with late-time oxygen emission suggests a double white dwarf merger event
摘要：
我们提出了一个光度和光谱分析的超发光和缓慢发展的03 fg-样Ia型SN 2021 zny。我们的观测活动从爆炸后$\sim5.3$小时开始（使SN 2021 zny成为同类中最早观测到的成员之一），各种地面和空间望远镜的密集多波长覆盖，并在峰值亮度后$\sim10$个月结束星云光谱。SN 2021 zny显示了几个同类的特征，例如峰值亮度（$M_{B}=-19.95$等），缓慢衰减（$Δm_{15}(B) = 0.62$等），蓝色的早期颜色，低喷出物速度和光球上方存在大量未燃烧的物质。然而，在爆炸后的第一个$\sim1.5$天，在四个测光带中观察到通量过剩，使SN 2021 zny成为具有这种独特行为的第三个03 fg事件，而其$+313$ d光谱显示出突出的[O I]线，这是热核SN的一个非常不寻常的特征。早期的通量过剩可以解释为喷出物与$\sim0.04\:\mathrm{M_{\odot}}$的H/He-贫拱星材料在$\sim10^{12}$厘米的距离的相互作用的结果，而低电离状态的后期的时间谱显示稳定的铁峰元素的丰度低。我们所有的观测结果都符合两颗碳/氧白矮星的祖先系统，它们经历了合并事件，在主要的白矮星爆炸之前，被破坏的白矮星喷射出富含碳的星周物质。
英文摘要：
We present a photometric and spectroscopic analysis of the ultra-luminous and slowly evolving 03fg-like Type Ia SN 2021zny. Our observational campaign starts from $\sim5.3$ hours after explosion (making SN 2021zny one of the earliest observed members of its class), with dense multi-wavelength coverage from a variety of ground- and space-based telescopes, and is concluded with a nebular spectrum $\sim10$ months after peak brightness. SN 2021zny displayed several characteristics of its class, such as the peak brightness ($M_{B}=-19.95$ mag), the slow decline ($Δm_{15}(B) = 0.62$ mag), the blue early-time colours, the low ejecta velocities and the presence of significant unburned material above the photosphere. However, a flux excess for the first $\sim1.5$ days after explosion is observed in four photometric bands, making SN 2021zny the third 03fg-like event with this distinct behavior, while its $+313$ d spectrum shows prominent [O I] lines, a very unusual characteristic of thermonuclear SNe. The early flux excess can be explained as the outcome of the interaction of the ejecta with $\sim0.04\:\mathrm{M_{\odot}}$ of H/He-poor circumstellar material at a distance of $\sim10^{12}$ cm, while the low ionization state of the late-time spectrum reveals low abundances of stable iron-peak elements. All our observations are in accordance with a progenitor system of two carbon/oxygen white dwarfs that undergo a merger event, with the disrupted white dwarf ejecting carbon-rich circumstellar material prior to the primary white dwarf detonation.
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