SN 2017hcc和SN 2023usc的比较光谱研究：I型IIn超新星
SN 2017hcc and SN 2023usc a comparative spectroscopic study of type IIn supernovae
AI总结：
通过对SN 2017hcc和SN 2023usc的光谱研究，发现I型IIn超新星中窄线的出现可能表明新的爆炸机制，且高扩展CSM的前身较为罕见。
摘要：
我们报告了利用希马拉雅钱德拉望远镜（HCT）获得的数据，对明亮且邻近的I型IIn超新星SN 2017hcc和SN 2023usc进行光谱研究。SN 2017hcc是一个研究充分的事件，我们的采样覆盖了7个时期，从爆炸后+14天开始，持续到恒星风阶段，即+411天。I型IIn事件SN 2023usc在爆炸后+12天到+155天期间采样了5个时期。SN 2023usc在晚期（+62天之后）的光谱几乎无特征（除了Hα），这表明该I型IIn事件可能有新的爆炸途径。假设由多时期抛射物质形成的CSM模型，我们在此对这两个事件与其他几种I型IIn/相互作用超新星进行了比较研究，这些超新星的前身具有持续的CSM特征。我们发现，真正的窄线（v << 1000 km/s）仅在少数事件（SN 2017hcc、SN 2023usc和SN 2010jl）的早期（约+10天）光谱中出现，这些事件在我们的样本中最初被分类为I型IIn。在大多数情况下，即使在非常早期的时期，线速度也停留在约1000 km/s。CSM线速度表明其范围和不透明度，这表明具有高度扩展的CSM且其外层区域光学透明的前身可能相对罕见。
英文摘要：
We report on a spectroscopic study of the bright, nearby type-IIn supernova SN 2017hcc, and SN 2023usc using data obtained from the Himalayan Chandra Telescope (HCT). SN 2017hcc is well-studied event, and our sampling covers 7 epochs, starting from +14\,d post explosion, and continuing into the nebular stage, at +411\,d. The type-IIn event SN 2023usc was sampled over 5 epochs from +12\,d to +155\,d post explosion. The nearly featureless (except H$α$) late time (+62\,d onward) spectra of SN 2023usc, suggests a novel explosion route for this type-IIn event. Assuming a CSM model created by multi-epoch ejection of material from the pre-explosion progenitor, we present here a comparative study of both events with several other type-IIn / interacting supernovae in progenitors with persistent signatures of a CSM. We find that true narrow lines ($v \ll 1000$\,km\,s$^{-1}$) emerge in the early ($\sim$ +10\,d) spectra only in few events (SN 2017hcc, SN 2023usc and SN 2010jl) initially classified as type-IIn in our sample -- in most cases the line velocity hovers at $\sim 1000$\,km\,s$^{-1}$ even in the very early epochs. CSM line velocity being indicative of its extent and opacity, this suggests that progenitors with a highly extended CSMs, which are also optically transparent in their outer regions may be relatively rare.
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