Surface Radioactivity or Interactions? Multiple Origins of Early-excess Type Ia Supernovae and Associated Subclasses
Surface Radioactivity or Interactions? Multiple Origins of Early-excess Type Ia Supernovae and Associated Subclasses
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DOI：
10.3847/1538-4357/aadb9a
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发表时间：
2018-08
期刊：
影响因子：
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通讯作者：
Jiachen Jiang;M. Doi;K. Maeda;T. Shigeyama
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文献类型：
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作者：
Jiachen Jiang;M. Doi;K. Maeda;T. Shigeyama
早期Ia型超新星（SNe Ia），特别是那些在爆炸最初几天内光度增强的超新星（“早期过量SNe Ia”），对于解决长期存在的SNe Ia前身和爆炸问题发挥着不可替代的作用。在本文中，我们系统地研究了从亚发光到发光亚类的 11 个早期过量超新星 Ia。其中8个是从23个具有极早相光学光变曲线的超新星Ia（“黄金”早期超新星Ia）中选出的，其中3个是从40个具有早相UV/NUV光变曲线的超新星Ia（包括14个黄金样本）中选出的。我们发现之前发现的早期过量 SNe Ia 对特定的 SN Ia 子类表现出明显的偏好。特别是，所有六个发光（91T 和 99aa 类）SNe Ia 中显示的早期过量特征与伴随喷射物相互作用场景预测的视角依赖性相冲突。相反，如此高的早期过量分数可能与发光超新星 Ia 的爆炸物理有关；也就是说，发光超新星 Ia 的前体中发生的更有效的爆炸可能因此解释了由富含 56Ni 的外层辐射提供动力的早期过量特征。不同 SN Ia 亚类中显示的早期过量特征的多样性表明所发现的早期过量 SNe Ia 的多个起源，挑战了它们作为稳健祖细胞指标的适用性。对早期过剩多样性的进一步了解不仅依赖于单个早期过剩超新星 Ia 的多波段光度测量和即时响应光谱，而且还依赖于对每个超新星 Ia 子类的一般早期阶段光曲线行为的研究，这可以通过在不久的将来正在进行/即将进行的瞬态调查项目来实现。
Early-phase Type Ia supernovae (SNe Ia), especially those with luminosity enhancement within the first few days of explosions (“early-excess SNe Ia”), play an irreplaceable role in addressing the long-standing progenitor and explosion issue of SNe Ia. In this paper, we systematically investigate 11 early-excess SNe Ia from subluminous to luminous subclasses. Eight of them are selected from 23 SNe Ia with extremely early-phase optical light curves (“golden” early-phase SNe Ia), and three of them are selected from 40 SNe Ia (including 14 golden samples) with early-phase UV/NUV light curves. We found that previously discovered early-excess SNe Ia show a clear preference for specific SN Ia subclasses. In particular, the early-excess feature shown in all six luminous (91T- and 99aa-like) SNe Ia is in conflict with the viewing angle dependence predicted by the companion-ejecta interaction scenario. Instead, such a high early-excess fraction is likely related to the explosion physics of luminous SNe Ia; i.e., a more efficient detonation happening in the progenitor of luminous SNe Ia may consequently account for the early-excess feature powered by the radiation from a 56Ni-abundant outer layer. The diversity of early-excess features shown in different SN Ia subclasses suggests multiple origins of the discovered early-excess SNe Ia, challenging their applicability as a robust progenitor indicator. Further understanding of the early-excess diversity relies not only on multiband photometry and prompt-response spectroscopy of individual early-excess SNe Ia but also on investigations of the general early-phase light-curve behavior of each SN Ia subclass, which can be realized through ongoing/forthcoming transient survey projects in the near future.