Detection of Water Vapor in the Photosphere of Arcturus
Detection of Water Vapor in the Photosphere of Arcturus
复制标题
大角星光球层中水蒸气的探测
DOI：
--
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
J. Lacy
中科院分区：
文献类型：
--
作者：
N. Ryde;D. Lambert;M. Richter;M. Richter;M. Richter;J. Lacy;J. Lacy
我们报道了用高分辨率红外光谱探测到K1.5III红巨星大角星(αBootis)中的OH和H2O的纯旋转线，光谱覆盖了806-822 cm-1(12.2-12.4μm)和884-923 cm-1(10.8-11.3μm)区域。大角星是迄今在其圆盘平均光谱中显示出水蒸气特征的最热恒星。我们认为水汽线起源于光球层，尽管是在外层。与通量恒定、流体静力学的标准τ模型光球相比，在降低光球最外层的温度结构(logMARCS500=-3.8后)后，我们能够令人满意地预测观测到的OH和H2O谱线的强度。我们的新模型从给定的温度结构出发，一致地计算了化学平衡和辐射传递。讨论了光球层最外层温度下降的可能原因，以及经典模式大气代码中假设的失败。
We report detections of pure rotation lines of OH and H2O in the K1.5 III red giant star Arcturus (α Bootis) using high-resolution, infrared spectra covering the regions 806-822 cm-1 (12.2-12.4 μm) and 884-923 cm-1 (10.8-11.3 μm). Arcturus is the hottest star yet to show water vapor features in its disk-averaged spectrum. We argue that the water vapor lines originate from the photosphere, albeit in the outer layers. We are able to predict the observed strengths of OH and H2O lines satisfactorily after lowering the temperature structure of the outermost parts of the photosphere (log τ500 = -3.8 and beyond) compared to a flux-constant, hydrostatic, standard MARCS model photosphere. Our new model is consistently calculated including chemical equilibrium and radiative transfer from the given temperature structure. Possible reasons for a temperature decrease in the outermost parts of the photosphere and the assumed breakdown of the assumptions made in classical model atmosphere codes are discussed.