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arXiv 1503.07165astro-ph.EP
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GTC OSIRIS过境系外行星大气调查：从窄带分光光度法探测HAT-P-1b中的钾

GTC OSIRIS transiting exoplanet atmospheric survey: detection of potassium in HAT-P-1b from narrowband spectrophotometry

P. A. Wilson, D. K Sing, N. Nikolov, A. Lecavelier des Etangs, F. Pont, J. J. Fortney, G. E. Ballester, M. López-Morales, J. -M. Désert, A. Vidal-Madjar

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11 pages, 7 figures
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摘要：

本文介绍了利用光学渡越窄带光度法对HAT-P-1b大气中钾的探测。使用10.4 m Gran Telescopio Canarias（GTC）与OSIRIS仪器在可调谐滤波器成像模式下获得的结果。我们观测到了四次凌日，两次在钾特征之外的连续波长处，分别在6792和8844，另外两次探测线翼中的钾特征，分别在7582.0和7664.9，使用12的滤波器宽度（R~650）。连续谱中的行星-恒星半径比在6792 ° C时为$R_{\rm{pl}}/R_{\star}$ = 0.1176 $\pm$ 0.0013，在8844 ° C时为$R_{\rm{pl}}/R_{\star}$ = 0.1168 $\pm$ 0.0022，明显低于钾谱线中的两个观测值：在7582.0 ° C时，流线翼中的$R_{\rm{pl}}/R_{\star}$ = 0.1248 $\pm$ 0.0014，在7664.9 ° C时，流线核心中的$R_{\rm{pl}}/R_{\star}$ = 0.1268 $\pm$ 0.0012。钾特征以外的观测值的加权平均值$R_{\rm{pl}}/R_{\star}$ = 0.1174 $\pm$ 0.0010，钾被检测为半径比的增加，在7582.0 nm处Δ $R_{\rm{pl}}/R_{\star}$ = 0.0073 $\pm$ 0.0017，在7664.9 nm处Δ $R_{\rm{pl}}/R_{\star}$ = 0.0094 $\pm$ 0.0016（显著性分别为4.3和6.1 $σ$）。我们假设钾的强烈探测是由大尺度高度引起的，这可以用高层大气底部的高温来解释。一个较低的平均分子质量所造成的分子氢解离成原子氢的EUV通量从主恒星也可以部分解释我们的检测幅度。

英文摘要：

We present the detection of potassium in the atmosphere of HAT-P-1b using optical transit narrowband photometry. The results are obtained using the 10.4 m Gran Telescopio Canarias (GTC) together with the OSIRIS instrument in tunable filter imaging mode. We observed four transits, two at continuum wavelengths outside the potassium feature, at 6792 Å and 8844 Å, and two probing the potassium feature in the line wing at 7582.0 Å and the line core at 7664.9 Å using a 12 Å filter width (R~650). The planet-to-star radius ratios in the continuum are found to be $R_{\rm{pl}}/R_{\star}$ = 0.1176 $\pm$ 0.0013 at 6792 Å and $R_{\rm{pl}}/R_{\star}$ = 0.1168 $\pm$ 0.0022 at 8844 Å, significantly lower than the two observations in the potassium line: $R_{\rm{pl}}/R_{\star}$ = 0.1248 $\pm$ 0.0014 in the line wing at 7582.0 Å and $R_{\rm{pl}}/R_{\star}$ = 0.1268 $\pm$ 0.0012 in the line core at 7664.9 Å. With a weighted mean of the observations outside the potassium feature $R_{\rm{pl}}/R_{\star}$ = 0.1174 $\pm$ 0.0010, the potassium is detected as an increase in the radius ratio of Δ$R_{\rm{pl}}/R_{\star}$ = 0.0073 $\pm$ 0.0017 at 7582.0 Å and Δ$R_{\rm{pl}}/R_{\star}$ = 0.0094 $\pm$ 0.0016 at 7664.9 Å (a significance of 4.3 and 6.1 $σ$ respectively). We hypothesise that the strong detection of potassium is caused by a large scale height, which can be explained by a high-temperature at the base of the upper atmosphere. A lower mean molecular mass caused by the dissociation of molecular hydrogen into atomic hydrogen by the EUV flux from the host star may also partly explain the amplitude of our detection.

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