Reproduction package for "A strong H− opacity signal in the near-infrared emission spectrum of the ultra-hot Jupiter KELT-9b"

This is a basic reproduction package for the paper "A strong H− opacity signal in the near-infrared emission spectrum of the ultra-hot Jupiter KELT-9b" by [Jacobs, B.; Désert, J. -M.; Pino, L. et al. (2022)](https://doi.org/10.1051/0004-6361/202244533). Abstract: We present the analysis of a spectroscopic secondary eclipse of the hottest transiting exoplanet detected to date, KELT-9b, obtained with the Wide Field Camera 3 aboard the Hubble Space Telescope. We complement these data with literature information on stellar pulsations and Spitzer/Infrared Array Camera and Transiting Exoplanet Survey Satellite eclipse depths of this target to obtain a broadband thermal emission spectrum. Our extracted spectrum exhibits a clear turnoff at 1.4 μm. This points to H− bound-free opacities shaping the spectrum. To interpret the spectrum, we perform grid retrievals of self-consistent 1D equilibrium chemistry forward models, varying the composition and energy budget. The model with solar metallicity and C/O ratio provides a poor fit because the H− signal is stronger than expected, requiring an excess of electrons. This pushes our retrievals toward high atmospheric metallicities ([M/H] = 1.98−0.21+0.19) and a C/O ratio that is subsolar by 2.4σ. We question the viability of forming such a high-metallicity planet, and therefore provide other scenarios to increase the electron density in this atmosphere. We also look at an alternative model in which we quench TiO and VO. This fit results in an atmosphere with a slightly subsolar metallicity and subsolar C/O ratio ([M/H] = −0.22−0.13+0.17, log (C/O) = −0.34−0.34+0.19). However, the required TiO abundances are disputed by recent high-resolution measurements of the same planet.本资源为论文《超热木星KELT-9b近红外发射光谱中的强H⁻不透明度信号》（作者：Jacobs, B.; Désert, J.-M.; Pino, L. 等，2022年，DOI: 10.1051/0004-6361/202244533）的基础复现套件。 摘要： 本研究针对迄今已发现的最热凌星系外行星KELT-9b，利用哈勃空间望远镜（Hubble Space Telescope）搭载的广角相机3（Wide Field Camera 3, WFC3）获取了其光谱型次级食的观测数据并开展分析。我们结合该目标的恒星脉动相关文献数据，以及斯皮策空间望远镜（Spitzer）/红外阵列相机（Infrared Array Camera, IRAC）与凌日系外行星巡天卫星（Transiting Exoplanet Survey Satellite, TESS）的食深度数据对上述光谱数据进行补充，最终得到宽带热发射光谱。我们提取得到的光谱在1.4 μm处呈现明显的光谱截断特征，这表明H⁻的束缚-自由不透明度主导了该光谱的形态。 为解释该光谱特征，我们构建了自洽的一维平衡化学正演模型网格，并通过调整大气成分与能量收支参数开展网格反演。采用太阳金属丰度与太阳碳氧比的模型无法对光谱实现良好拟合，这是因为实测的H⁻信号强度高于预期，需要更高的电子丰度。这使得反演结果指向较高的大气金属丰度（[M/H] = 1.98_{-0.21}^{+0.19}），且碳氧比比太阳值低2.4σ。我们对形成此类高金属丰度行星的可行性提出质疑，并据此提出了若干可提升该大气电子密度的替代情景。 我们还测试了另一种模型：通过淬灭二氧化钛（TiO）与一氧化钒（VO）的丰度来约束大气参数。该拟合结果对应的大气金属丰度略低于太阳值，碳氧比也低于太阳值（[M/H] = -0.22_{-0.13}^{+0.17}，log(C/O) = -0.34_{-0.34}^{+0.19}）。但该模型所需的TiO丰度，与近期对该行星开展的高分辨率观测结果存在冲突。