超越五个标高：亚海王星的与成分和云相关的Ariel Tier-2要求
Beyond Five Scale Heights: Composition- and Cloud-dependent Ariel Tier-2 Requirements for sub-Neptunes
- Tohoku University（东北大学）
- McGill University（麦吉尔大学）
机构由 AI 辅助整理，请以论文原文为准。
中文总结 AI 辅助
该研究量化成分和云对亚海王星Ariel Tier-2要求的影响，发现多数场景下小型行星探测光谱特征需更多凌星次数，且已识别含亚稳态氦的Ariel目标可关联低层大气与高层大气。
中文摘要 AI 辅助
Ariel任务候选样本（MCS）Tier-2要求假设存在清晰的H₂/He大气和五个标高的透射信号，以此提供通用筛选参考。我们明确指定成分和云时，量化197颗已知行星（1.5≤行星半径/地球半径<4.0）的这些要求变化。评估1倍、10倍、100倍太阳金属丰度下平衡化学透射光谱，分别对应无云大气和理想化1毫巴云盖，归入47个AIRS Tier-2通道，并结合目标特定的MCS校准噪声曲线。对每种大气，计算重复观测中至少90%的情况下，无特征光谱被3σ置信度拒绝所需的凌星次数。1倍太阳金属丰度的无云大气与MCS预测高度吻合；10倍太阳金属丰度下，更强的分子消光通常提升可探测性，而100倍太阳金属丰度下，平均分子量增加占主导，所需凌星次数约翻倍；有云大气遵循相同非单调趋势，但代价显著更高：1倍太阳金属丰度、1毫巴的情况所需凌星次数比MCS预测多近一个数量级，富金属有云情况仍需数倍于MCS预测的凌星次数。总体而言，在多数测试的大气场景中，小型行星探测光谱特征所需凌星次数多于MCS所列数量。文献交叉匹配进一步识别出Ariel已探测到亚稳态氦的目标，其Tier-2分子光谱可连接低层大气成分和云与延伸的逃逸H₂/He高层大气。
英文摘要
The Ariel Mission Candidate Sample (MCS) Tier-2 requirements provide a common screening reference by assuming a clear H$_2$/He atmosphere and a five-scale-height transmission signal. We quantify how those requirements change for 197 known planets with $1.5\leq R_{\rm p}/R_\oplus<4.0$ when composition and clouds are specified explicitly. Equilibrium-chemistry transmission spectra at $1\times$, $10\times$, and $100\times$ solar metallicity are evaluated for clear atmospheres and idealized 1-mbar cloud decks, binned to the 47 AIRS Tier-2 channels, and combined with target-specific MCS-calibrated noise curves. For each atmosphere, we calculate the number of transits required for a featureless spectrum to be rejected at a $3σ$ confidence in at least 90\% of repeated observations. The clear $1\times$-solar atmosphere closely follows the MCS prediction. At $10\times$ solar metallicity, stronger molecular opacity generally improves detectability, whereas at $100\times$ solar metallicity the increased mean molecular weight dominates and roughly doubles the required number of transits. Cloudy atmospheres follow the same non-monotonic trend but at substantially greater cost: the $1\times$-solar, 1-mbar case requires nearly an order of magnitude more transits than the MCS prediction, while the enriched cloudy cases still require several times more. Overall, in most atmospheric scenarios tested, small planets require more transits to robustly detect spectral features than listed in the MCS. A literature crossmatch further identifies Ariel targets with detected metastable helium, for which Tier-2 molecular spectra could connect lower-atmosphere composition and clouds to an extended, escaping H$_2$/He upper atmosphere.
