晚型星近UV带的非LTE模拟
Non-LTE modeling of the near UV band of late-type stars
摘要：
我们调查LTE和非LTE模型的能力，以适应近紫外波段的绝对流量分布和个人谱线配置文件的三个标准的恒星，高品质的分光光度计和高分辨率光谱：太阳（G2 V），大角星（K2 III），南河三（F5 IV-V）。我们研究了1）原子线列表的选择对NLTE模型拟合近紫外波段通量水平的能力的影响，2）允许NLTE模型拟合观测所需的假设连续热吸收消光源的量，以及3）用NLTE模型和标准连续近紫外消光拟合观测所需的半经验温度结构。我们发现，所有的模型计算与高质量的原子线列表预测太多的流量在近紫外波段的大角星，但适合较温暖的恒星。在近紫外线的太阳辐照度的独立测量之间的差异是足够大的，我们不能肯定地得出结论，模型预测太多的近紫外线通量，与其他最近的结果。我们推测，目前的大气模型的K巨星在近紫外波段的不足是最好的解决，假设仍然缺少连续的热消光，和失踪的近紫外消光变得更加重要，降低有效温度的光谱类晚于早期G，这表明分子起源。
英文摘要：
We investigate the ability of both LTE and Non-LTE models to fit the near UV band absolute flux distribution and individual spectral line profiles of three standard stars for which high quality spectrophotometry and high resolution spectroscopy are available: The Sun (G2 V), Arcturus (K2 III), and Procyon (F5 IV-V). We investigate 1) the effect of the choice of atomic line list on the ability of NLTE models to fit the near UV band flux level, 2) the amount of a hypothesized continuous thermal absorption extinction source required to allow NLTE models to fit the observations, and 3) the semi-empirical temperature structure required to fit the observations with NLTE models and standard continuous near UV extinction. We find that all models that are computed with high quality atomic line lists predict too much flux in the near UV band for Arcturus, but fit the warmer stars well. The variance among independent measurements of the solar irradiance in the near UV is sufficiently large that we cannot definitely conclude that models predict too much near UV flux, in contrast to other recent results. We surmise that the inadequacy of current atmospheric models of K giants in the near UV band is best addressed by hypothesizing that there is still missing continuous thermal extinction, and that the missing near UV extinction becomes more important with decreasing effective temperature for spectral classes later than early G, suggesting a molecular origin.
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