We present the first detection of atomic emission lines from the atmosphere of an exoplanet. We detect neutral iron lines from the dayside of KELT-9b ( T eq ∼ 4000 K). We combined thousands of spectrally resolved lines observed during one night with the HARPS-N spectrograph ( R ∼ 115,000), mounted at the Telescopio Nazionale Galileo. We introduce a novel statistical approach to extract the planetary parameters from the binary mask cross-correlation analysis. We also adapt the concept of contribution function to the context of high spectral resolution observations, to identify the location in the planetary atmosphere where the detected emission originates. The average planetary line profile intersected by a stellar G2 binary mask was found in emission with a contrast of 84 ± 14 ppm relative to the planetary plus stellar continuum (40% ± 5% relative to the planetary continuum only). This result unambiguously indicates the presence of an atmospheric thermal i...

中文翻译：

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KELT-9b白天的中性铁排放线：TNG XX的采用HARPS-N的GAPS计划

我们提出了从系外行星大气中首次探测原子发射线的方法。我们从KELT-9b（Teq〜4000 K）的白天检测到中性铁线。我们将一晚观察到的数千条光谱分辨谱线与安装在Telescopio Nazionale Galileo上的HARPS-N光谱仪（R约115,000）结合在一起。我们介绍了一种新颖的统计方法，可从二值蒙版互相关分析中提取行星参数。我们还将贡献函数的概念与高光谱分辨率观测的背景相适应，以识别探测到的排放源在行星大气中的位置。在发射中发现了由恒星G2二元掩模相交的平均行星线轮廓，相对于行星加恒星连续体的对比度为84±14 ppm（仅相对于行星连续体的对比度为40％±5％）。该结果明确表明存在大气热辐射。