AI 中文总结
研究近距离恒星相遇中行星-卫星抛射，通过数值散射实验量化卫星保留概率和抛射截面，确定有利轨道条件，发现其构成产生FFPMs的可行通道，为抛射历史提供诊断，相关调查或能探测流浪行星周围卫星。
AI 中文摘要
当行星系统经历近距离恒星相遇时，可能会形成自由漂浮的行星-卫星对（FFPMs）。我们量化了行星和行星-卫星系统在近距离恒星相遇时的卫星保留概率和抛射截面，以确定最有利于形成FFPMs的轨道条件。我们进行了广泛的数值散射实验，在行星（$a_p$）和卫星（$a_m$）的轨道间距网格上计算抛射截面，并对所有其他初始参数进行边缘化。模拟跟踪了各种相遇几何形状下行星和卫星的命运。FFPM截面取决于卫星半长轴$a_m$，在$a_m\sim0.45\,R_H$附近下降之前逐渐减小。仅行星的抛射截面则随$a_p$稳步下降。类似木卫一的卫星（$a_m = 0.008\,R_H$）能幸存，但在$0.4\,R_H$以上生存率下降。与行星-行星散射相比，恒星相遇在所有间距下更有效地保留卫星。$a_m\lesssim 0.4\,R_H$的幸存卫星保持近圆形、低倾角轨道，而宽轨道卫星显示出更强的动力学激发。将我们的截面应用于微引力透镜系统MOA-2011-BLG-262Lb表明，对于太阳质量的宿主，可能的前身半长轴在$a_p \sim 1.3$\,au和$\sim 5.9$ au之间。不确定性仍然很大，概率分布是平坦的，但我们倾向于$a_p \sim 5.2$\,au。恒星相遇抛射构成了产生FFPMs的可行通道，其轨道特性不同于行星-行星散射形成的特性。卫星保留和轨道激发为抛射历史提供了有前景的诊断方法。当前和即将进行的微引力透镜和直接成像调查可能能够探测到流浪行星周围的伽利略质量卫星，为动力学形成途径提供新的测试。
英文摘要
Free-floating planet-moon pairs (FFPMs) may form when planetary systems experience close stellar encounters. We quantify moon-retention probabilities and ejection cross sections for planets and planet-moon systems subject to close stellar encounters, and to dentify the orbital conditions most favorable for forming FFPMs. We conducted extensive numerical scattering experiments to compute ejection cross-sections on a grid in the orbital separation of the planet ($a_p$) and the moon ($a_m$), marginalizing over all other initial parameters. The simulations tracked both planetary and lunar fates across a wide range of encounter geometries. FFPM cross-sections depend on the moon semi-major axis $a_m$, decreasing gradually until a drop near $a_m\sim0.45\,R_H$. Planet-only ejection cross-sections instead decline steadily with $a_p$. Io-like moons ($a_m = 0.008\,R_H$) survive, but survival falls beyond $0.4\,R_H$. Compared with planet-planet scattering, stellar encounters preserve moons more effectively across all separations. Surviving moons at $a_m\lesssim 0.4\,R_H$ retain near-circular, low-inclination orbits, while wide-orbit moons show stronger dynamical excitation. Applying our cross-sections to the microlensing system MOA-2011-BLG-262Lb suggests possible progenitor semi-major axes between $a_p \sim 1.3$\,au and $\sim 5.9$ au for a solar-mass host. Uncertainties remain large and the probability distribution is flat but we prefer $a_p \sim 5.2$\,au. Stellar-encounter ejections constitute a viable channel for producing FFPMs whose orbital properties differ from those formed by planet-planet scattering. Moon retention and orbital excitation provide promising diagnostics of ejection history. Current and upcoming microlensing and direct-imaging surveys may be capable of detecting Galilean-mass moons around rogue planets, offering new tests of dynamical formation pathways.
CommentsAccepted for publication in A&A
