Properties of Type Iax Supernova 2019muj in the Late Phase: Existence, Nature, and Origin of the Iron-rich Dense Core
Properties of Type Iax Supernova 2019muj in the Late Phase: Existence, Nature, and Origin of the Iron-rich Dense Core
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DOI：
10.3847/1538-4357/ac9df2
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发表时间：
2022-10
期刊：
影响因子：
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通讯作者：
K. Maeda;M. Kawabata
中科院分区：
文献类型：
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作者：
K. Maeda;M. Kawabata
Iax型超新星（SNe Iax）是一类特殊的Ia型超新星，其早期谱线与Ia型超新星具有相同的主谱线，但电离度更高，谱线速度更低。它们的后期行为在许多方面偏离了通常的Ia期；SNe Iax连续100天呈现光球光谱，光度下降非常缓慢。在这项工作中，我们研究了SN Iax 2019muj的后期光谱，包括新发现的约500天的光谱。光谱仍然以允许跃迁为主，但具有较低的电离状态，可能检测到[O i]λλ6300, 6363。通过综合考察允许跃迁（Fe ii， Fe i和Ca ii近红外三重态）和禁止跃迁（[Ca ii]λλ7292, 7324和[O i]）的光谱形成过程，我们定量地约束了最内层区域的性质，并发现它与外部喷射物不同；最内层成分的质量为~ 0.03 M⊙，主要是铁（最初可能是56Ni），膨胀速度为~ 760 km s−1。我们认为内部成分的性质可以用失败/弱白矮星热核爆炸场景来解释。我们认为，一部分最初被束缚在（包络层）内的富含56Ni的物质后来会通过56Ni/Co/Fe衰变的能量输入被喷射出来，形成第二个非束缚的喷射成分，它表现为后期所见的内部致密成分。
Type Iax supernovae (SNe Iax) form a class of peculiar SNe Ia, whose early phase spectra share main spectral line identifications with canonical SNe Ia but with higher ionization and much lower line velocities. Their late-time behaviors deviate from usual SNe Ia in many respects; SNe Iax continue showing photospheric spectra over several 100 days and the luminosity decline is very slow. In this work, we study the late-time spectra of SN Iax 2019muj, including a newly presented spectrum at ∼500 days. The spectrum is still dominated by allowed transitions but with a lower ionization state, with possible detection of [O i]λλ6300, 6363. By comprehensively examining the spectral formation processes of allowed transitions (Fe ii, Fe i, and the Ca ii near-IR triplet) and forbidden transitions ([Ca ii]λλ7292, 7324 and [O i]), we quantitatively constrain the nature of the innermost region and find that it is distinct from the outer ejecta; the mass of the innermost component is ∼0.03 M ⊙ dominated by Fe (which can initially be 56Ni), expanding with a velocity of ∼760 km s−1. We argue that the nature of the inner component is explained by the failed/weak white-dwarf thermonuclear explosion scenario. We suggest that a fraction of the 56Ni-rich materials initially confined in (the envelope of) the bound remnant can later be ejected by the energy input through the 56Ni/Co/Fe decay, forming the second unbound ejecta component which manifests itself as the inner dense component seen in the late phase.