狮子座CN耀斑的日冕爆炸
A coronal explosion on the flare star CN Leonis
摘要：
我们提出了同时高时间和高光谱分辨率观测在光学和软X射线波长附近的耀斑星CN狮子座。在我们的观测活动期间，发生了一次重大耀斑，使恒星的瞬时能量输出提高了近三个数量级。耀斑表现出经常观察到的脉冲行为，在光学上具有快速上升和缓慢衰减，并且在光学耀斑峰值之后约200秒具有宽的软X射线最大值。然而，除了这种通常遇到的耀斑现象，我们发现了一个非常短的（~2秒）软X射线峰，这是非常有可能的热，而不是非热的性质，并在时间上与光学耀斑峰重合。虽然在硬X射线能量下，在耀斑爆发时经常在太阳上观察到非热爆发，但在太阳或恒星背景下从未观察到秒级的热软X射线爆发。这个事件的时间依赖性，一维流体动力学模型需要一个非常短的能量沉积时间尺度的几秒钟，以协调理论与观测，从而表明我们正在目睹CN狮子座日冕爆炸的结果。因此，狮子座CN的耀斑提供了一个机会，可以观测研究长期以来被认为是日冕加热的“微耀斑”的物理学。
英文摘要：
We present simultaneous high-temporal and high-spectral resolution observations at optical and soft X-ray wavelengths of the nearby flare star CN Leo. During our observing campaign a major flare occurred, raising the star's instantaneous energy output by almost three orders of magnitude. The flare shows the often observed impulsive behavior, with a rapid rise and slow decay in the optical and a broad soft X-ray maximum about 200 seconds after the optical flare peak. However, in addition to this usually encountered flare phenomenology we find an extremely short (~2 sec) soft X-ray peak, which is very likely of thermal, rather than non-thermal nature and temporally coincides with the optical flare peak. While at hard X-ray energies non-thermal bursts are routinely observed on the Sun at flare onset, thermal soft X-ray bursts on time scales of seconds have never been observed in a solar nor stellar context. Time-dependent, one-dimensional hydrodynamic modeling of this event requires an extremely short energy deposition time scale of a few seconds to reconcile theory with observations, thus suggesting that we are witnessing the results of a coronal explosion on CN Leo. Thus the flare on CN Leo provides the opportunity to observationally study the physics of the long-sought "micro-flares" thought to be responsible for coronal heating.
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