标题： 地狱中的气候变化：蒸发行星K2-22b凌日的长期变化 显示英文标题

标题： Climate Change in Hell: Long-Term Variation in Transits of the Evaporating Planet K2-22b

摘要： 上下文：位于超短周期轨道上的岩石行星可能拥有表面熔岩海洋和岩石蒸汽大气，在其中尘埃可以凝结。对这些尘埃的观测可以提供关于这些天体的组成和表面条件的信息。目标：我们限制“蒸发”行星K2-22b的转移尘埃云的特性和长期（十年）行为。方法：我们使用MuSCAT地面多光学通道成像仪在40次预测的凌日事件中观测了K2-22b，并利用地面ATLAS（2018-2024）和空间TESS（2021-2023）调查的长期监测数据来补充这些数据。结果：我们在7次凌日事件中检测到了信号，其中没有一次显示出显著的波长依赖性。预计MuSCAT检测到的凌日次数大于等于22次，表明自2014年K2发现观测以来平均凌日深度有所下降。结论：缺乏显著的波长依赖性表明尘埃颗粒较大或云层光学厚度较大。深度的长期趋势可能是由于主星的磁周期或行星白天面熔岩海洋的翻转所致。K2-22b完全消失的可能性被排除，因为凌日历法的稳定性不受非引力因素影响，这限制了其质量至少与谷神星相当。 显示英文摘要

摘要： Context: Rocky planets on ultra-short period orbits can have surface magma oceans and rock-vapour atmospheres in which dust can condense. Observations of that dust can inform about the composition surface conditions on these objects. Aims: We constrain the properties and long-term (decade) behaviour of the transiting dust cloud from the "evaporating" planet K2-22b. Methods: We observed K2-22b around 40 predicted transits with MuSCAT ground-based multi-optical channel imagers, and complemented these data with long-term monitoring by the ground-based ATLAS (2018-2024) and space-based TESS (2021-2023) surveys. Results: We detected signals during 7 transits, none of which showed significant wavelength dependence. The expected number of MuSCAT-detected transits is >=22, indicating a decline in mean transit depth since the K2 discovery observations in 2014. Conclusions: Lack of significant wavelength dependence indicates that dust grains are large or the cloud is optically thick. Long-term trends of depth could be due to a magnetic cycle on the host star or overturn of the planet's dayside surface magma ocean. The possibility that K2-22b is disappearing altogether is ruled out by the stability of the transit ephemeris against non-gravitational forces, which constrains the mass to be at least comparable to Ceres.