Red versus Blue: Early Observations of Thermonuclear Supernovae Reveal Two Distinct Populations?
Red versus Blue: Early Observations of Thermonuclear Supernovae Reveal Two Distinct Populations?
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DOI：
10.3847/2041-8213/aadd46
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发表时间：
2018-07
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通讯作者：
M. Stritzinger;B. Shappee;A. Piro;C. Ashall;E. Baron;P. Hoeflich;S. Holmbo;T. Holoien;M. Phillips;C. Burns;C. Contreras;N. Morrell;M. Tucker
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作者：
M. Stritzinger;B. Shappee;A. Piro;C. Ashall;E. Baron;P. Hoeflich;S. Holmbo;T. Holoien;M. Phillips;C. Burns;C. Contreras;N. Morrell;M. Tucker
我们研究了在推断的第一次发光时间（tfirst）的三天内发现的十几个超新星Ia的早期阶段内在（B − V）0颜色演化，并在tfirst的五天内开始具有（B − V）0颜色信息。样本表明有两个不同的早期种群。第一种是表现出缓慢进化的蓝色的种群，第二种是表现出红色的种群，进化得更快。我们发现，早期的蓝色事件都是1991 T/1999 aa的类似与更明亮，缓慢下降的光变曲线比那些表现出早期的红色。将第一个样本放置在分支图上（即，Si ii λλ5972，6355伪等效宽度的比率）表明，所有蓝色天体都属于分支浅硅（SS）光谱类型，而除了类似2000 Cx的SN 2012 fr之外，所有早期红色事件都属于分支核正常（CN）或冷却（CL）类型。一些潜在的过程有助于早期排放的探索，我们发现，在一般情况下，在同伴碰撞模型中固有的视角依赖性是不一致的所有的SS对象与早期的观测是蓝色的，并表现出过剩。我们警告说，在解释早期相位光变曲线时必须非常小心，因为可能有各种各样的物理过程可能在起作用，而且重要的理论工作仍有待完成。
We examine the early phase intrinsic (B − V)0 color evolution of a dozen SNe Ia discovered within three days of the inferred time of first light (tfirst) and have (B − V)0 color information beginning within five days of tfirst. The sample indicates there are two distinct early populations. The first is a population exhibiting blue colors that slowly evolve, and the second population exhibits red colors and evolves more rapidly. We find that the early blue events are all 1991T/1999aa-like with more luminous, slower declining light curves than those exhibiting early red colors. Placing the first sample on the Branch diagram (i.e., ratio of Si ii λλ5972, 6355 pseudo-Equivalent widths) indicates that all blue objects are of the Branch shallow silicon (SS) spectral type, while all early red events except for the 2000cx-like SN 2012fr are of the Branch Core Normal (CN) or CooL (CL) type. A number of potential processes contributing to the early emission are explored, and we find that, in general, the viewing-angle dependance inherent in the companion collision model is inconsistent with all of the SS objects with early-time observations being blue and exhibiting an excess. We caution that great care must be taken when interpreting early phase light curves as there may be a variety of physical processes that are possibly at play and significant theoretical work remains to be done.