发表机构
University of Michigan; Massachusetts Institute of Technology（密歇根大学; 麻省理工学院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究量化了银河系核球中恒星飞掠对行星系统外围的截断效应，发现宽轨道行星在十亿年尺度上被抛射，贡献自由漂浮行星，幸存行星轨道偏心倾斜，为Roman观测提供基线。
AI 中文摘要
最近发射的南希·格雷斯·罗曼太空望远镜（Roman）即将开始观测，有望彻底改变我们对系外行星种群统计的理解。Roman的银河系核球时域巡天（GBTDS）将通过凌星和微引力透镜技术观测银河系核球，为研究热木星以及长周期/自由漂浮系外行星在致密且运动学上炽热的恒星环境中提供独特机会。在本信中，我们量化了重复的、脉冲式的恒星飞掠如何截断核球中行星系统的外围。我们发现，对于低质量主星周围宽轨道（≳250天文单位）的行星，飞掠导致在约十亿年时间尺度上发生抛射。假设这些宽轨道被占据，这些抛射可能对Roman探测到的自由漂浮行星群体有所贡献。在约10天文单位之外幸存的行星被置于偏心且倾斜的轨道上。我们表明，尽管系统经历多次近距离遭遇，但演化由单次最强扰动主导；行星轨道（即使是那些逃避抛射的）经历超扩散（即莱维飞行）。我们评论了我们的结果对适合Roman凌星搜索的热木星起源的影响。我们的工作作为定量基线，未来的动力学研究可以在此基础上更好地理解银河系核球中行星系统的演化。
英文摘要
The recently launched Nancy Grace Roman Space Telescope (\textit{Roman}) will soon begin observations that promise to revolutionize our understanding of exoplanet demographics. \textit{Roman}'s Galactic Bulge Time-Domain Survey (GBTDS) will observe the Galactic Bulge via transit and microlensing techniques, providing a unique opportunity to study hot Jupiters as well as long-period/free-floating exoplanets in a dense and kinematically hot stellar environment. In this Letter, we quantify how repeated, impulsive stellar flybys truncate the outskirts of planetary systems in the Bulge. We find that flybys result in ejections on $\sim$Gyr timescales for wide orbits (${\gtrsim} 250\ \text{au}$) around low-mass hosts. Provided these wide orbits are populated, these ejections likely contribute to the population of free-floating planets probed by \textit{Roman}. Surviving planets outside of ${\sim} 10$ au are placed on eccentric and misaligned orbits. We show that, though systems suffer many close encounters, the evolution is dominated by the single strongest perturbation; planetary orbits (even those that evade ejection) undergo superdiffusion (i.e. a Lévy flight). We comment on the implications of our results for the origin of hot Jupiters amenable to $\textit{Roman}$'s transit search. Our work serves as a quantitative baseline from which future dynamical studies can build to better understand the evolution of planetary systems in the Galactic Bulge.
Comments17 pages, 10 figures. submitted to ApJL
