arXiv 1109.18022011-09-08astro-ph.EP

行星际大气中碱线吸收的研究概况

A Survey of Alkali Line Absorption in Exoplanetary Atmospheres

Adam G. Jensen, Seth Redfield, Michael Endl, William D. Cochran, Lars Koesterke, Travis S. Barman

备注：: 38 total pages (preprint format), 9 color figures, 4 tables, accepted for publication in ApJ
DOI：: 10.1088/0004-637X/743/2/203

摘要：

我们用Hobby-Eberly望远镜（HET）对四个系外行星系统进行了超过90小时的光谱观测。观测是在过境和过境，我们分析了不同的光谱-即，透射光谱-检查其在$λ\lambda5889, 5895$处的中性钠（\ion{Na}{1}）双峰和$\lambda7698$处的中性钾（\ion{K}{1}）波长处的吸收。我们使用\ion{Ca}{1} $\lambda6122$的透射光谱-它显示出强烈的恒星吸收，但不是我们期望在这些大气中显示出显著吸收的碱金属共振线-作为控制线来检查我们的测量系统误差。我们使用经验蒙特卡罗方法来量化这些系统误差。在使用独立推导的还原和分析管道对相同数据集进行的再分析中，我们确认了先前在HD 189733 b中观察到的\ion{Na}{1}吸收水平为$(-5.26\pm1.69)\times10^{-4}$（12 μ m积分带的平均值与先前作者一致）。此外，我们初步确认HD 209458 b中观察到的\ion{Na}{1}吸收（多位作者独立）为$(-2.63\pm0.81)\times10^{-4}$水平，尽管解释不太清楚。此外，我们发现\ion{Na}{1}吸收的$(-3.16\pm2.06)\times10^{-4}$在$<3σ$在HD 149026 b;功能明显的透射光谱与真实的吸收是一致的，并表明这可能是一个很好的目标，为未来的观测确认。没有其他结果（HD 147506 b中的\ion{Na}{1}和所有四个靶标中的\ion{Ca}{1}和\ion{K}{1}）对$\geq 3σ$有意义，尽管我们观察到一些我们认为主要是伪影的特征。

英文摘要：

We obtained over 90 hours of spectroscopic observations of four exoplanetary systems with the Hobby-Eberly Telescope (HET). 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 (\ion{Na}{1}) doublet at $λ\lambda5889, 5895$ and neutral potassium (\ion{K}{1}) at $\lambda7698$. We used the transmission spectrum at \ion{Ca}{1} $\lambda6122$---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 quantity these systematic errors. In a reanalysis of the same dataset using a reduction and analysis pipeline that was derived independently, we confirm the previously seen \ion{Na}{1} absorption in HD 189733b at a level of $(-5.26\pm1.69)\times10^{-4}$ (the average value over a 12 Å integration band to be consistent with previous authors). Additionally, we tentatively confirm the \ion{Na}{1} absorption seen in HD 209458b (independently by multiple authors) at a level of $(-2.63\pm0.81)\times10^{-4}$, though the interpretation is less clear. Furthermore, we find \ion{Na}{1} absorption of $(-3.16\pm2.06)\times10^{-4}$ 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 (\ion{Na}{1} in HD 147506b and \ion{Ca}{1} and \ion{K}{1} in all four targets) are significant to $\geq 3σ$, although we observe some features that we argue are primarily artifacts.

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