We present nebular spectra of the Type Ia supernova (SN Ia) SN 2019yvq, which had a bright flash of blue and ultraviolet light after exploding, followed by a rise similar to other SNe Ia. Although SN 2019yvq displayed several other rare characteristics, such as persistent high ejecta velocity near peak brightness, it was not especially peculiar, and if the early “excess” emission were not observed, it would likely be included in cosmological samples. The excess flux can be explained by several different physical models linked to the details of the progenitor system and explosion mechanism. Each has unique predictions for the optically thin emission at late times. In our nebular spectra, we detect strong [Ca ii ] λλ 7291, 7324 and Ca near-IR triplet emission, consistent with a double-detonation explosion. We do not detect H, He, or [O i ] emission, predictions for some single-degenerate progenitor systems and violent white dwa...

中文翻译：

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强烈的钙排放表明紫外线闪烁的SN Ia 2019yvq是次钱德拉色卡质量双爆轰爆炸的结果

我们展示了Ia型超新星（SN Ia）SN 2019yvq的星云光谱，爆炸后具有蓝色和紫外光的明亮闪烁，随后出现了类似于其他SNe Ia的上升。尽管SN 2019yvq显示了其他几个罕见的特征，例如在峰值亮度附近持续的高喷射速度，但并不是特别奇怪，如果未观察到早期的“过量”发射，则很可能会被包含在宇宙样本中。过剩的通量可以通过与祖细胞系统和爆炸机制的细节相关的几种不同的物理模型来解释。每个人对于后期光学稀薄发射都有独特的预测。在我们的星云光谱中，我们检测到强[Ca ii]λλ7291、7324和Ca近红外三重态发射，与双爆轰爆炸一致。我们没有检测到H，He或[O i]发射，