恒星日冕X射线谱中由于不透明度效应引起的谱线强度增强
Line intensity enhancements in stellar coronal X-ray spectra due to opacity effects
摘要：
上下文在太阳和恒星的X射线谱中，Fe XVII的I（15.01 A）/I（16.78 A）发射线强度比偏离了理论值。这归因于15.01 A线的不透明度，导致其强度降低，并根据发射器和吸收器在空间上不同的几何形状进行解释。目标。本文研究了活动冷矮星EV Lac在耀斑和静止光谱中的I（15.01 A）/I（16.78 A）强度比。方法.这些观测是用XMM-牛顿卫星上的反射光栅分光计获得的。发射测量分布与温度重建技术用于我们的分析。结果我们发现，15.01 A线表现出显着的增强强度超过光学薄的值。据我们所知，这是第一次在如此合理的统计基础上检测到这种增强。我们解释这种增强的几何形状，其中的发射器和吸收器是不是空间上不同的，并且在几何形状是这样的，共振泵浦的上一级有一个更大的影响所观察到的线强度比共振吸收的视线。
英文摘要：
Context. The I(15.01 A)/I(16.78 A) emission line intensity ratio in Fe XVII has been reported to deviate from its theoretical value in solar and stellar X-ray spectra. This is attributed to opacity in the 15.01 A line, leading to a reduction in its intensity, and was interpreted in terms of a geometry in which the emitters and absorbers are spatially distinct. Aims. We study the I(15.01 A)/I(16.78 A) intensity ratio for the active cool dwarf EV Lac, in both flare and quiescent spectra. Methods. The observations were obtained with the Reflection Grating Spectrometer on the XMM-Newton satellite. The emission measure distribution versus temperature reconstruction technique is used for our analysis. Results. We find that the 15.01 A line exhibits a significant enhancement in intensity over the optically thin value. To our knowledge, this is the first time that such an enhancement has been detected on such a sound statistical basis. We interpret this enhancement in terms of a geometry in which the emitters and absorbers are not spatially distinct, and where the geometry is such that resonant pumping of the upper level has a greater effect on the observed line intensity than resonant absorption in the line-of-sight.
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