The soft X-ray light curves of partially eclipsed stellar flares Eclipsing of stellar flares
The soft X-ray light curves of partially eclipsed stellar flares Eclipsing of stellar flares
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部分食恒星耀斑的软 X 射线光变曲线 食恒星耀斑
DOI：
10.1111/j.1365-2966.2011.19666.x
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发表时间：
2012
影响因子：
4.8
通讯作者：
Johnstone C
中科院分区：
文献类型：
--
作者：
Johnstone C
大多数恒星耀斑的软X射线光变曲线具有“典型”的形态，它包括快速上升，然后缓慢的指数衰减。然而，在ChandraOrion超深项目（COUP）期间，对161颗前主序星上216个最亮耀斑的研究表明，许多耀斑的光变曲线偏离了这种典型的形态。虽然这可以归因于多个典型的耀斑的叠加，我们探讨的可能性，其宿主恒星的耀斑的时变日食也可能是一个重要的因素。我们假设每个耀斑包含在一个单一的，均匀的等离子体密度磁回路，并指定耀斑的发射测量随时间的内在变化。我们不仅考虑了由星星本身引起的自转食，而且考虑了由星周盘和与耀斑有关的双折射引起的自转食。基于这个简单的模型，我们产生了一组类似的耀斑COUP数据库中观察到的。许多日食只是减少了耀斑的最大发射量或衰变时间。因此，我们的结论是，日食往往通过未被发现，但通常只有一个温和的影响耀斑发射测量配置文件，因此派生的环长度。我们表明，日食可以很容易地再现所观察到的非典型耀斑形态。然而，非典型模拟耀斑形态的数量远低于COUP样本中发现的数量。大量观察到的非典型耀斑形态，因此，必须归因于其他过程，如多个耀斑环。
Most stellar flares’ soft X-ray light curves possess a ‘typical’ morphology, which consists of a rapid rise followed by a slow exponential decay. However, a study of 216 of the brightest flares on 161 pre-main-sequence stars, observed during theChandraOrion Ultradeep Project (COUP), showed that many flare light curves depart from this typical morphology. While this can be attributed to the superposition of multiple typical flares, we explore the possibility that the time-variable eclipsing of flares by their host stars may also be an important factor. We assume each flare is contained within a single, uniform plasma density magnetic loop and specify the intrinsic variation of the flare’s emission measure with time. We consider rotational eclipse not only by the star itself, but also by circumstellar discs and flare-associated prominences. Based on this simple model, we generate a set of flares similar to those observed in the COUP data base. Many eclipses simply reduce the flare’s maximum emission measure or decay time. We conclude therefore that eclipses often pass undetected, but usually have only a modest influence on the flare emission measure profile and hence the derived loop lengths. We show that eclipsing can easily reproduce the observed atypical flare morphologies. The number of atypical modelled flare morphologies is, however, much less than that found in the COUP sample. The large number of observed atypical flare morphologies, therefore, must be attributed to other processes such as multiple flaring loops.