ACCESS：来自Magellan/IMACS的WASP-19 b的无特征光透射谱
ACCESS: A featureless optical transmission spectrum for WASP-19b from Magellan/IMACS
摘要：
短周期（$0.94$ -天）凌日系外行星WASP-19 b是透射光谱研究的特殊目标，因为它的大气尺度高度（$\sim 500$ km）和平衡温度（$\sim 2100$ K）相对较大。在这里，我们报告了六个精确的光谱麦哲伦/IMACS观测，其中五个目标的全光学窗口从$0.45-0.9μ$ m和一个目标的$0.4-0.55μ$ m蓝光范围。其中五个数据集是一致的透射光谱没有任何显着的光谱特征，而一个显示了显着的斜率作为波长的函数，我们解释为所产生的光球在恒星的不均匀性。再加上HST/WFC 3红外观测，我们的光学/近红外测量指出，在WASP-19 b的大气中存在高海拔云与以前的研究一致。使用半分析检索方法，考虑到行星和恒星的光谱特征，我们发现水的丰度与太阳WASP-19 b和强有力的证据，如TiO和Na的光吸收剂的太阳下的丰度一致;没有检测到强的光学斜率，这表明，如果有雾霾存在，它们比以前建议的要弱得多。此外，在我们的数据集中观察到两个点交叉事件并进行了分析，其中包括第一个明确检测到的系外行星宿主恒星上的亮点交叉事件。
英文摘要：
The short period ($0.94$-day) transiting exoplanet WASP-19b is an exceptional target for transmission spectroscopy studies, due to its relatively large atmospheric scale-height ($\sim 500$ km) and equilibrium temperature ($\sim 2100$ K). Here we report on six precise spectroscopic Magellan/IMACS observations, five of which target the full optical window from $0.45-0.9μ$m and one targeting the $0.4-0.55μ$m blue-optical range. Five of these datasets are consistent with a transmission spectrum without any significant spectral features, while one shows a significant slope as a function of wavelength, which we interpret as arising from photospheric heterogeneities in the star. Coupled with HST/WFC3 infrared observations, our optical/near-infrared measurements point to the presence of high altitude clouds in WASP-19b's atmosphere in agreement with previous studies. Using a semi-analytical retrieval approach, considering both planetary and stellar spectral features, we find a water abundance consistent with solar for WASP-19b and strong evidence for sub-solar abundances for optical absorbers such as TiO and Na; no strong optical slope is detected, which suggests that if hazes are present, they are much weaker than previously suggested. In addition, two spot-crossing events are observed in our datasets and analyzed, including one of the first unambiguously detected bright spot-crossing events on an exoplanet host star.
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