Ib型SN 2008 D的早期紫外/光发射
Early UV/Optical Emission of The Type Ib SN 2008D
摘要：
我们提出了另一种解释与X射线瞬变080109相关的SN 2008 D的爆发后发射。对这个天体的观测显示，爆发后不久出现的光变曲线最小值和由于喷出物的放射性加热而产生的主要光度峰值之间的对比度非常小，只有0.35 dex。流体动力学模型表明，一颗受冲击的沃尔夫-拉叶星的冷却导致了更大的差异（> 0.9 dex）。我们提出的方案是，在爆炸过程中产生的喷流沉积在喷出物的外层富含56镍的材料。高速放射性物质的存在使我们能够再现物体的完整光度演化。如果没有外层的56 Ni，假设一颗比沃尔夫-拉叶星更大的恒星的前身，就有可能完全从激波包层的冷却中重现早期的辐射，但是这需要一个与恒星演化模型预测的有很大不同的初始密度结构。冷却阶段的分析模型已经被提出，重现了SN 2008 D的早期发射和扩展的祖先。然而，我们发现，模型的有效性只到1.5天后，只有两个数据的SN 2008 D爆炸。我们还讨论了喷出物与二进制同伴的相互作用的可能性，根据公布的解析表达式。然而，要符合早期的辐射，双星的距离应该小于3 Rsun，这对于包含两颗大质量恒星的系统来说太小了。
英文摘要：
We propose an alternative explanation for the post-breakout emission of SN 2008D associated with the X-ray transient 080109. Observations of this object show a very small contrast of 0.35 dex between the light-curve minimum occurring soon after the breakout, and the main luminosity peak that is due to radioactive heating of the ejecta. Hydrodynamical models show that the cooling of a shocked Wolf-Rayet star leads to a much greater difference (> 0.9 dex). Our proposed scenario is that of a jet produced during the explosion which deposits 56Ni-rich material in the outer layers of the ejecta. The presence of high-velocity radioactive material allows us to reproduce the complete luminosity evolution of the object. Without outer 56Ni it could be possible to reproduce the early emission purely from cooling of the shocked envelope by assuming a larger progenitor than a Wolf-Rayet star, but that would require an initial density structure significantly different from what is predicted by stellar evolution models. Analytic models of the cooling phase have been proposed reproduce the early emission of SN 2008D with an extended progenitor. However, we found that the models are valid only until 1.5 days after the explosion where only two data of SN 2008D are available. We also discuss the possibility of the interaction of the ejecta with a binary companion, based on published analytic expressions. However, the binary separation required to fit the early emission should be < 3 Rsun which is too small for a system containing two massive stars.
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