新星中尘埃的快速形成：解释了速度级-形成时间尺度的相关性
Rapid Dust Formation in Novae: The Speed Class - Formation Timescale Correlation Explained
摘要：
观测表明，经典新星中尘埃形成的开始时间强烈依赖于它们的速度等级，在较慢的新星中尘埃通常需要更长的时间才能形成。利用速度等级、光度和喷射速度之间的经验关系，可以表明尘埃形成的时间尺度基本上与速度等级无关。然而，在新星爆发之后，中心热源的光谱会发生变化，在莱曼极限附近发出的辐射比例会增加。频谱演变的速率也取决于速度等级。因此，我们通过假设能量高于莱曼极限的光子被尘埃形成点内部的中性氢气吸收，从而阻止这些光子到达成核点，从而改进了简单模型。通过这种改进，尘埃形成的时间尺度在理论上依赖于速度等级，我们的理论修正结果与观测数据吻合得很好。我们考虑两种类型的碳基尘埃，石墨和无定形碳，这两种类型产生类似的关系。我们的结果可用于预测给定速度级别的新星何时形成尘埃，从而何时应该最佳地进行观测来检测尘埃形成的开始。
英文摘要：
Observations show that the time of onset of dust formation in classical novae depends strongly on their speed class, with dust typically taking longer to form in slower novae. Using empirical relationships between speed class, luminosity and ejection velocity, it can be shown that dust formation timescale is expected to be essentially independent of speed class. However, following a nova outburst the spectrum of the central hot source evolves, with an increasing proportion of the radiation being emitted short-ward of the Lyman limit. The rate at which the spectrum evolves also depends on the speed class. We have therefore refined the simple model by assuming photons at energies higher than the Lyman limit are absorbed by neutral hydrogen gas internal to the dust formation sites, therefore preventing these photons reaching the nucleation sites. With this refinement the dust formation timescale is theoretically dependent on speed class and the results of our theoretical modification agree well with the observational data. We consider two types of carbon-based dust, graphite and amorphous carbon, with both types producing similar relationships. Our results can be used to predict when dust will form in a nova of a given speed class and hence when observations should optimally be taken to detect the onset of dust formation.
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