发表机构
University of Palermo; INAF – Osservatorio Astronomico di Palermo; University of Michigan; University of Warwick; ESO - European Southern Observatory; INAF – Osservatorio Astronomico di Roma（巴勒莫大学; 意大利国家天体物理研究所–巴勒莫天文台; 密歇根大学; 华威大学; 欧洲南方天文台; 意大利国家天体物理研究所–罗马天文台）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过结合HARPS-N、HARPS、K2和TESS数据，修正了年轻系统K2-233中三颗凌星行星的质量，发现其质量依赖于活动建模策略，并预测K2-233 d将经历显著大气损失，演化为次海王星或裸核超级地球。
AI 中文摘要
理解系外行星的物理性质对于表征其大气和内部组成至关重要。精确的行星质量对于约束体密度和内部结构必不可少，尤其是在拥有位于或接近半径谷内行星的年轻系统中，在那里大气质量损失可能强烈地塑造其演化。在此，我们修正了围绕K2-233（一颗年轻的（约400 Myr）活跃K型恒星）运行的三颗凌星行星的质量。我们将来自GAPS/ArMS大型计划的70次HARPS-N观测与124次档案HARPS观测、K2光变曲线以及在我们的径向速度监测期间获得的TESS测光数据相结合。我们探索了几种Multi-GP配置以减轻强烈的恒星活动，并发现推断的行星质量显著依赖于所采用的活动建模策略，产生了多个物理上可行的解，而非唯一优选解。我们对K2-233 d的长期大气演化进行了建模，并发现了显著的大气质量损失。取决于其内部组成和大气性质，该行星预计将在Gyr时间尺度上演化为保留薄包层的低质量次海王星（Rp约1.71-1.84 R⊕）或裸核超级地球（Rp约1.95 R⊕）。我们的内部结构模型表明，K2-233 b和c可能以铁为主，而K2-233 d保留了大量的H/He大气。
英文摘要
Understanding exoplanet physical properties is crucial for characterising their atmospheres and internal composition. Precise planetary masses are essential for constraining bulk densities and interiors, particularly in young systems hosting planets within or near the radius valley, where atmospheric mass loss may strongly shape their evolution. Here we revise the masses of the three transiting planets orbiting K2-233, a young ($\sim 400$ Myr) active K-type star. We combine 70 HARPS-N observations from the GAPS/ArMS Large Programme with 124 archival HARPS observations, K2 light curves, and TESS photometry obtained during our radial-velocity monitoring. We explore several Multi-GP configurations to mitigate the strong stellar activity and find that the inferred planetary masses depend significantly on the adopted activity-modelling strategy, yielding several physically viable solutions rather than a uniquely preferred one. We model the long-term atmospheric evolution of K2-233 d and find significant atmospheric mass loss. Depending on its internal composition and atmospheric properties, the planet is expected to evolve towards either a low-mass sub-Neptune retaining a thin envelope ($R_p \sim 1.71$-$1.84\ R_{\oplus}$) or a bare-core super-Earth ($R_p \sim 1.95\ R_{\oplus}$) on Gyr timescales. Our interior-structure models suggest that K2-233 b and c are likely iron-dominated, while K2-233 d retains a substantial H/He atmosphere.
Comments20 pages, 14 figures, 5 tables, A&A accepted
