论文标题
甲烷作为可居住区亚北极k2-18 b中的主要吸收剂
Methane as a dominant absorber in the habitable-zone sub-Neptune K2-18 b
论文作者
论文摘要
Tsiaras等人在信中。报道了在K2-18 B大气中检测到水蒸气，这是位于M-Dwarf恒星宜居区的7至10个地球质量的系外行星。该检测基于与哈勃太空望远镜/宽场摄像头3的观测，以1.4 $ $ m的吸收特征观察到，我们已经模拟了使用辐射相位识别平衡模型的K2-18b的平均温度结构和组成，并在这里介绍了相应的转运光谱谱图。我们认为，据报道的吸收很可能是由于甲烷所致，甲烷预计在冷颈氢气大气中有望丰富。更普遍地，我们表明，在过境光谱中看到的1.4- $ $ m的吸收并不是诊断为有效温度小于600 k的亚北极的水蒸气的诊断，并且仅在较大的温度下，水蒸气在该波长下在甲烷上占主导地位。
In their Letter, Tsiaras et al. reported the detection of water vapour in the atmosphere of K2-18 b, an exoplanet of 7 to 10 Earth masses located in the habitable zone of an M-dwarf star. The detection is based on an absorption feature seen at 1.4 $μ$m in observations of the transiting exoplanet with the Hubble Space Telescope/Wide Field Camera 3. We have simulated the mean temperature structure and composition of K2-18b using a radiative-convective equilibrium model and we present here the corresponding transit spectroscopy calculations. We argue that the reported absorption is most likely due to methane, a gas expected to be abundant in the hydrogen-helium atmosphere of cold sub-Neptunes. More generally, we show that the 1.4-$μ$m absorption seen in transit spectra is not diagnostic of the presence of water vapour for sub-Neptunes having an effective temperature less than 600 K and that water vapour dominates over methane at this wavelength only at larger temperatures.
