Detecting atmospheres around planets with a radius below 1.6 R _⊕, commonly referred to as rocky planets, has proven to be challenging. However, rocky planets orbiting M dwarfs are ideal candidates due to their favorable planet-to-star radius ratio. Here, we present one transit observation of the Super-Earth L98-59 d (1.58 R _⊕ and 2.31 M _⊕), at the limit of rocky/gas-rich, using the JWST NIRSpec G395H mode covering the 2.8–5.1 μm wavelength range. The extracted transit spectrum from a single transit observation deviates from a flat line by 2.6σ–5.6σ, depending on the data reduction and retrieval setup. The hints of an atmospheric detection are driven by a large absorption feature between 3.3 and 4.8 μm. A stellar contamination retrieval analysis rejected the source of this feature as being due to stellar inhomogeneities, making the best fit an atmospheric model including sulfur-bearing species, suggesting that the atmosphere of L98-59 d may not be at equilibrium. This result will need to be confirmed by the analysis of the second NIRSpec G395H visit in addition to the NIRISS SOSS transit observation.

中文翻译：

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1.6 R ⊕ Super-Earth L98-59 d 周围富硫大气的迹象，来自 JWST NIRspec G395H 透射光谱


事实证明，探测半径低于 1.6 R_⊕ 的行星（通常称为岩石行星）周围的大气层具有挑战性。然而，围绕 M 矮星运行的岩石行星是理想的候选者，因为它们具有良好的行星与恒星半径比。在这里，我们展示了一次超级地球 L98-59 d（1.58 R_⊕ 和 2.31 M_⊕）凌日观测，使用覆盖 2.8–5.1 μm 波长范围的 JWST NIRSpec G395H 模式，在岩石/富含气体的极限下。从单个凌日观测中提取的凌日光谱与平线的偏差为 2.6σ–5.6σ，具体取决于数据缩减和检索设置。大气探测的提示是由 3.3 至 4.8 μm 之间的大吸收特征驱动的。恒星污染反演分析拒绝了这一特征的来源，认为这是由于恒星不均匀性造成的，使包括含硫物质在内的大气模型成为最佳拟合，这表明 L98-59 d 的大气可能并不处于平衡状态。除了 NIRISS SOSS 凌日观测之外，还需要通过对第二次 NIRSpec G395H 访问的分析来确认这一结果。