Corona(e) of AR lacertae. I. The temperature and abundance distribution
Corona(e) of AR lacertae. I. The temperature and abundance distribution
复制标题
AR 蝎虎座的日冕(e)。
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
S. Drake
中科院分区：
文献类型：
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作者：
K. Singh;N. White;S. Drake
利用ROSAT PSPC、ASCA SIS和GIS探测器同时观测的RS CVn双星AR Lac的X射线能谱，分析了其日冕温度和丰度分布。光谱与等离子体发射模型共同拟合到以下可能的温度分布：（a）具有离散多温度发射分量的光谱，（B）具有对温度的幂律依赖性的连续发射测量，以及（c）由六阶切比雪夫多项式的和参数化的连续发射分布。我们发现：（i）具有离散或连续发射测量（CEM）分布的太阳丰度等离子体模型被拒绝，（ii）最佳拟合是用两温（2 T）等离子体发射模型获得的，其中元素O，Mg，Si，S，Ar，Ca和Fe的丰度相对于太阳光球值为3-4倍，以及（iii）最佳拟合CEM分布也具有类似降低的丰度，但与2 T模型相比拟合数据较差。这些结果得到证实，即使Fe-L区域，这是受原子物理学的不确定性，被排除在拟合。我们认为光学深度效应不太可能是所观察到的线复合物相对于连续的弱点的解释。在主和次日食的光谱数据的分析表明，在2 T模型的高温组件的排放措施似乎是更多的影响比低温组件的主日食，这表明前者的一部分是集中在空间上更紧凑的结构。
X-ray spectra of the RS CVn binary AR Lac, obtained from simultaneous observations with the ROSAT PSPC and the ASCA SIS and GIS detectors, have been analyzed to study the coronal temperature and abundance distribution. The spectra were jointly fitted with plasma emission models to the following possible temperature distributions: (a) one with discrete multitemperature emission components, (b) a continuous emission measure with a power-law dependence on temperature, and (c) a continuous emission distribution parameterized by the sum of a sixth-order Chebyshev polynomial. We find that (i) solar abundance plasma models with either discrete or continuous emission measure (CEM) distributions are rejected, (ii) the best fit is obtained with a two-temperature (2T) plasma emission model with an underabundance of the elements 0, Mg, Si, S, Ar, Ca, and Fe by a factor of 3-4 relative to the solar photospheric values, and (iii) the best-fit CEM distribution also has similarly reduced abundances but fits the data less well than the 2T model. These results are confirmed even when the Fe-L region, which is subject to uncertainties in the atomic physics, is excluded from the fit. We consider optical depth effects as unlikely to be the explanation for the observed weakness of the line complexes relative to the continuum. Analysis of the spectral data during the primary and secondary eclipses shows that the emission measure of the high-temperature component in the 2T models appears to be more affected by the primary eclipse than the low-temperature component, suggesting that part of the former is concentrated in structures that are spatially more compact.