A SURVEY OF ALKALI LINE ABSORPTION IN EXOPLANETARY ATMOSPHERES
A SURVEY OF ALKALI LINE ABSORPTION IN EXOPLANETARY ATMOSPHERES
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系外行星大气中碱线吸收的调查
DOI：
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发表时间：
2011
期刊：
影响因子：
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通讯作者：
T. Barman
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作者：
A. Jensen;S. Redfield;M. Endl;W. Cochran;L. Koesterke;T. Barman
我们用霍比-埃伯利望远镜对四个系外行星系统进行了超过90小时的光谱观测。观测是在凌日和凌日外进行的，我们分析了差异光谱，即。在λλ5889, 5895的中性钠（Na i）重态和λ7698的中性钾（K i）的波长处检测其吸收。我们使用了Ca i λ6122的透射光谱——它显示出强烈的恒星吸收，但不是碱金属共振线，我们期望在这些大气中显示出显著的吸收——作为控制线来检查我们的测量结果的系统误差。我们使用经验蒙特卡罗方法来量化这些系统误差。在使用独立导出的还原和分析管道对同一数据集进行的再分析中，我们证实了HD 189733b先前看到的Na i吸收水平为（−5.26±1.69）× 10−4（在12 Å积分波段上的平均值与先前作者一致）。此外，我们初步确认了HD 209458b中Na i的吸收（由多个作者独立完成）在（−2.63±0.81）× 10−4的水平上，尽管解释不太清楚。此外，我们发现hd149026b在<3σ处Na i的吸收为（−3.16±2.06）× 10−4；透射光谱中明显的特征与实际吸收一致，表明这可能是未来观测确认的一个很好的目标。没有其他结果（HD 147506b中的Na i和所有四个目标中的Ca i和K i）对大于或等于3σ是显著的，尽管我们观察到一些我们认为主要是人工制品的特征。
We obtained over 90 hr of spectroscopic observations of four exoplanetary systems with the Hobby–Eberly Telescope. Observations were taken in transit and out of transit, and we analyzed the differenced spectra—i.e., the transmission spectra—to inspect it for absorption at the wavelengths of the neutral sodium (Na i) doublet at λλ5889, 5895 and neutral potassium (K i) at λ7698. We used the transmission spectrum at Ca i λ6122—which shows strong stellar absorption but is not an alkali metal resonance line that we expect to show significant absorption in these atmospheres—as a control line to examine our measurements for systematic errors. We use an empirical Monte Carlo method to quantify these systematic errors. In a reanalysis of the same data set using a reduction and analysis pipeline that was derived independently, we confirm the previously seen Na i absorption in HD 189733b at a level of (− 5.26 ± 1.69) × 10−4 (the average value over a 12 Å integration band to be consistent with previous authors). Additionally, we tentatively confirm the Na i absorption seen in HD 209458b (independently by multiple authors) at a level of (− 2.63 ± 0.81) × 10−4, though the interpretation is less clear. Furthermore, we find Na i absorption of (− 3.16 ± 2.06) × 10−4 at <3σ in HD 149026b; features apparent in the transmission spectrum are consistent with real absorption and indicate this may be a good target for future observations to confirm. No other results (Na i in HD 147506b and Ca i and K i in all four targets) are significant to ⩾3σ, although we observe some features that we argue are primarily artifacts.