Hubble Space Telescope transmission spectroscopy of the exoplanet HD 189733b: high‐altitude atmospheric haze in the optical and near‐ultraviolet with STIS
Hubble Space Telescope transmission spectroscopy of the exoplanet HD 189733b: high‐altitude atmospheric haze in the optical and near‐ultraviolet with STIS
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DOI：
10.1111/j.1365-2966.2011.19142.x
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发表时间：
2011-02
影响因子：
4.8
通讯作者：
D. Sing;F. Pont;S. Aigrain;D. Charbonneau;J. Désert;N. Gibson;R. Gilliland;W. Hayek;G. Henry;H. Knutson;A. D. Étangs;T. Mazeh;Avi Shporer
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文献类型：
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作者：
D. Sing;F. Pont;S. Aigrain;D. Charbonneau;J. Désert;N. Gibson;R. Gilliland;W. Hayek;G. Henry;H. Knutson;A. D. Étangs;T. Mazeh;Avi Shporer
本文介绍了哈勃太空望远镜（HST）的光学光谱和近紫外透射光谱，这些光谱是由修复后的太空望远镜成像光谱仪（STIS）拍摄的。得到的光谱覆盖范围为2900-5700 A，在500 A带宽内，每次曝光的信噪比水平大于11000。我们利用两次凌日事件期间获得的时间序列光谱来确定行星半径的波长依赖性，并首次测量了系外行星在该波长范围内的大气透射光谱。我们的测量，结合现有的HST光谱，现在提供了一个覆盖全光学区域的宽带传输光谱。STIS的数据还显示了在我们的一次凌日事件中存在一个巨大的掩星黑子的明确证据，我们用它来限制K矮星恒星黑子的特征，估计黑子温度在T ~ 4250 K左右。通过对恒星变异性的同步地面光度监测，我们还测量了恒星活动水平与凌日测量的行星-恒星半径对比之间的相关性，这与预测非常吻合。我们发现行星透射光谱与先前从HST高级巡天相机中发现的高海拔大气雾霾的瑞利散射非常一致。现在发现高空雾霾覆盖了整个光学区，并具有瑞利散射的良好特征。这些发现表明，雾霾可能是地球的一个全球主导的大气特征，它将导致较短光波长的高光学反照率。
We present Hubble Space Telescope (HST) optical and near-ultraviolet transmission spectra of the transiting hot Jupiter HD 189733b, taken with the repaired Space Telescope Imaging Spectrograph (STIS) instrument. The resulting spectra cover the range 2900–5700 A and reach per exposure signal-to-noise ratio levels greater than 11 000 within a 500-A bandwidth. We used time series spectra obtained during two transit events to determine the wavelength dependence of the planetary radius and measure the exoplanet’s atmospheric transmission spectrum for the first time over this wavelength range. Our measurements, in conjunction with existing HST spectra, now provide a broad-band transmission spectrum covering the full optical regime. The STIS data also show unambiguous evidence of a large occulted stellar spot during one of our transit events, which we use to place constraints on the characteristics of the K dwarf’s stellar spots, estimating spot temperatures around T eff ∼ 4250 K. With contemporaneous ground-based photometric monitoring of the stellar variability, we also measure the correlation between the stellar activity level and transit-measured planet-to-star radius contrast, which is in good agreement with predictions. We find a planetary transmission spectrum in good agreement with that of Rayleigh scattering from a high-altitude atmospheric haze as previously found from HST Advanced Camera for Surveys. The high-altitude haze is now found to cover the entire optical regime and is well characterized by Rayleigh scattering. These findings suggest that haze may be a globally dominant atmospheric feature of the planet which would result in a high optical albedo at shorter optical wavelengths.