标题： KELT-9b系外行星大气中的原子铁和钛 显示英文标题

标题： Atomic iron and titanium in the atmosphere of the exoplanet KELT-9b

摘要： 系外行星的化学组成是限制其形成历史的关键因素。铁是最丰富的过渡金属，但由于其高度难熔的性质，在系外行星中从未被直接探测到。KELT-9b（HD 195689b）是超热木星类别的典型代表，这些行星跨越恒星与气态巨行星之间的过渡区域，并因其平衡温度高达4050 ± 180 K而成为研究大气化学的独特实验室。这些特性表明，其大气层是一个紧密约束的化学系统，预计接近化学平衡且无云层覆盖。先前预测，在可见光波段范围内可以检测到铁的光谱线。在如此高温下，铁和几种其他过渡金属不会被限制在分子或云颗粒中，而是以原子形式存在。在这里，我们报告通过应用交叉相关技术于系外行星凌星期间获得的高分辨率光谱，直接探测到了KELT-9b中的中性原子铁（Fe）、单电离铁（Fe+）以及单电离钛（Ti+）。 显示英文摘要

摘要： The chemical composition of an exoplanet is a key ingredient in constraining its formation history. Iron is the most abundant transition metal, but has never been directly detected in an exoplanet due to its highly refractory nature. KELT-9b (HD 195689b) is the archetype of the class of ultra-hot Jupiters that straddle the transition between stars and gas-giant exoplanets and serve as distinctive laboratories for studying atmospheric chemistry, because of its high equilibrium temperature of 4050 +/- 180 K. These properties imply that its atmosphere is a tightly constrained chemical system that is expected to be nearly in chemical equilibrium and cloud-free. It was previously predicted that the spectral lines of iron will be detectable in the visible range of wavelengths. At these high temperatures, iron and several other transition metals are not sequestered in molecules or cloud particles and exist solely in their atomic forms. Here, we report the direct detection of atomic neutral and singly-ionized iron (Fe and Fe+), and singly-ionized titanium (Ti+) in KELT-9b via the cross-correlation technique applied to high-resolution spectra obtained during the primary transit of the exoplanet.