PEPSI调查、检索与众多巨型大气图谱（PIRANGA）. IV. KELT-20 b超热木星的高分辨率相位解析光谱
PEPSI Investigation, Retrieval, and Atlas of Numerous Giant Atmospheres (PIRANGA). IV. High-Resolution Phased-Resolved Spectroscopy of The Ultra Hot Jupiter KELT-20 b
AI总结：
利用PEPSI光谱仪对KELT-20 b进行高分辨率相位解析光谱研究，确定其大气丰度比及热结构，发现Ni/Fe比值与太阳一致，Ca/Fe比值较低，且丰度比在不同相位下保持稳定。
摘要：
我们利用PEPSI光谱仪呈现了五组KELT-20 b超热木星的高分辨率光学发射光谱数据。利用贝叶斯检索框架，我们约束了其昼面的压力-温度剖面以及Fe、Ni和Ca的丰度，提供了KELT-20 b首次的Ni和Ca发射测量。我们分别检索了前和后掩星数据集（分别对应傍晚和早晨面），并比较了它们的热结构和化学丰度的约束。我们发现前掩星数据集的丰度比后掩星数据集更低。我们利用平衡化学模型解释这些结果，该模型表明refractory丰度约为太阳的~10-30倍。由于绝对丰度与连续体不透明度之间存在众所周知的退化性，丰度比是更精确的行星丰度探测器。因此，我们测量了这些数据集中的Ni/Fe和Ca/Fe丰度比，并发现它们在1-sigma范围内一致。我们约束Ni/Fe比值与太阳一致，误差在2-sigma范围内，而Ca/Fe比值为0.001-0.01倍太阳，不考虑电离。我们比较了这些丰度比与KELT-20 b的传输光谱文献结果，并发现它们在2-sigma范围内一致，表明尽管丰度随相位显著变化，但这些物种的丰度比保持相对恒定。我们发现热反转型顶温度差约100 K，表明傍晚面比早晨面更热，强调在研究超热木星时考虑三维效应的重要性。
英文摘要：
We present five datasets of high-resolution optical emission spectra of the ultra-hot Jupiter KELT-20 b with the PEPSI spectrograph. Using a Bayesian retrieval framework, we constrain its dayside pressure-temperature profile and abundances of Fe, Ni, and Ca, providing the first measurements for Ni and Ca for KELT-20 b in emission. We retrieve the pre- and post-eclipse datasets separately (corresponding to the evening and morning sides, respectively), and compare the constraints on their thermal structures and chemical abundances. We constrain lower abundances in the pre-eclipse datasets compared to the post-eclipse datasets. We interpret these results with an equilibrium chemistry model which suggests ~10-30x supersolar refractory abundances. Due to the well-known degeneracy between absolute abundances and continuum opacities, the abundance ratios are more precise probes of the planetary abundances. Therefore we measure the abundance ratios [Ni/Fe] and [Ca/Fe] across these datasets and find they agree within 1-sigma. We constrain [Ni/Fe] to be consistent with solar within 2-sigma, and [Ca/Fe] to be 0.001-0.01x solar, not accounting for ionization. We compare these abundance ratios with literature results for KELT-20 b in transmission, and find they agree within 2-sigma, suggesting that even though the abundances vary significantly as a function of phase, the abundance ratios of these species remain relatively constant. We find a ~100 K difference in temperature at the top of the thermal inversion, suggesting a hotter evening side than morning side and underscoring the importance of considering 3D effects when studying ultra-hot Jupiters.
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