发表机构
Kapteyn Astronomical Institute, University of Groningen; Earth and Planets Laboratory, Carnegie Institution for Science; The Observatories of the Carnegie Institution for Science; Institute of Astronomy, University of Cambridge; School of Physics & Astronomy, University of Birmingham; Waterloo Centre for Astrophysics and Department of Physics and Astronomy, University of Waterloo（格罗宁根大学卡佩恩天文研究所; 卡内基科学机构地球与行星实验室; 卡内基科学机构天文台; 剑桥大学天文学研究所; 伯明翰大学物理与天文学院; 滑铁卢大学天体物理学中心及物理与天文学系）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用PROTEUS框架探究熔岩行星TOI-561 b的大气留存演化，明确其需满足的挥发分、地幔、逃逸等条件，识别出CO₂与SO₂主导的两种大气原型，揭示内部-大气耦合对受辐射岩质行星大气留存的控制作用。
AI 中文摘要
岩质行星通过内部与大气之间的挥发分交换发生演化，这种相互作用的观测约束仍十分有限。值得注意的是，受强辐射的超短周期（USP）系外行星或许为这种交换过程提供了研究窗口——部分此类行星保留了较低的整体密度，与岩质内部周围包裹富挥发分包层的情况相符，暗示可能存在次生大气。TOI-561 b就是一个典型例子，其整体密度为4.3±0.4 g cm⁻³，近期詹姆斯·韦布空间望远镜（JWST）的观测结果支持其昼侧岩浆洋之上存在浓厚的挥发分大气。本研究利用PROTEUS内部-大气耦合框架，探究TOI-561 b在数十亿年间保留大量大气的演化路径，研究了不同核半径占比、邦德反照率、大气逃逸效率、地幔氧化态以及初始C-H-O-N-S挥发分库存，涵盖原位演化和晚期向内迁移两种情况。超过半数的模拟结果显示行星内部裸露，密度过高，无法匹配观测结果。成功匹配观测的情况倾向于：富挥发分起源（氢含量≤200个地球海洋当量，S/H≤10，N/H≤1）、氧化地幔（氧逸度fO₂≥IW+4）、小铁核（核半径占比≤0.40），以及流体动力学逃逸 regime下的低逃逸效率（ε≤10⁻³）。当前TOI-561 b的情况与全球岩浆洋之上存在浓厚（表面压力约10³–10⁴ bar）、平均分子量高（38–60 g mol⁻¹）的大气相符，根据整体硫含量分为两种原型：CO₂主导型和SO₂主导型。迁移是可行的，但并非重现观测结果的必要条件。本研究阐明了内部-大气耦合如何控制受辐射岩质行星的大气留存。
英文摘要
Rocky planets evolve through the exchange of volatiles between their interiors and atmospheres, an interplay still poorly constrained by observations. Remarkably, highly irradiated ultrashort-period (USP) exoplanets may offer a window into this exchange -- some retain low bulk densities compatible with volatile-rich envelopes surrounding rocky interiors, indicating possible secondary atmospheres. TOI-561 b is a prime example, with a bulk density of $4.3\pm0.4$ g cm$^{-3}$ and recent JWST observations favoring a thick volatile atmosphere overlying a dayside magma ocean. Here, we investigate the evolutionary pathways allowing TOI-561 b to retain a substantial atmosphere over gigayears using the PROTEUS coupled interior--atmosphere framework. We explore different core radius fractions, Bond albedos, atmospheric escape efficiencies, mantle redox states, and initial C--H--O--N--S volatile inventories, under in situ evolution and late inward migration. Over half of our simulations leave a bare interior too dense to match observations. Successful cases favor a volatile-rich origin ($\lesssim200$ Earth oceans of hydrogen, S/H $\le10$, and N/H $\le1$), an oxidized mantle ($f$O$_2 \gtrsim \mathrm{IW}+4$), a small iron core ($\le 0.40$ for the core radius fraction), and low escape efficiency ($ε\lesssim 10^{-3}$) in the hydrodynamic escape regime. At present, TOI-561 b is consistent with a global magma ocean beneath a thick (surface pressure $\approx 10^{3}$--$10^{4}$ bar), high mean molecular weight atmosphere ($38$--$60$ g mol$^{-1}$). Two archetypes emerge, differentiated by bulk sulfur content: a CO$_2$-dominated and an SO$_2$-dominated atmosphere. Migration is viable but not required to reproduce the observations. Our study illustrates how interior--atmosphere coupling governs atmospheric retention on irradiated rocky planets.
CommentsSubmitted to ApJ; 26 pages, 6 figures
