一颗外巨行星激发并约束$\pi$ Mensae d的轨道
An Outer Giant Excites and Constrains the Orbit of $π$ Mensae d
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中文总结 AI 辅助
通过重新分析速度数据和N体模拟，发现外巨行星b可激发候选行星d的高偏心率，并将其轨道约束在顺行或逆行的近共面构型。
中文摘要 AI 辅助
邻近的$\pi$ Mensae系统包含一颗偏心巨行星b，其轨道周期为5.7年，一颗周期为6.27天的凌星亚海王星c，以及一颗位于两者之间、轨道周期为123天的候选行星d。已发表的估计将d的偏心率置于约0.2至0.4之间。我们使用三开普勒拟合重新分析了772个已发表的速度数据，并通过N体积分探索了三维的b-d动力学。当相位或近心点经度先验被放宽时，高偏心率解仍然存在；精确重要性重加权到基于种群信息的Beta偏心率先验给出$e_{d}=0.378^{+0.050}_{-0.049}$。在20千年的积分中，靠近顺行和逆行共面端点的构型中有84.5%存活，而在$60^\circ \leq I_{bd} < 120^\circ$范围内仅有21.3%存活；恒星碰撞主导了失败。b的长期摄动将62个初始$e_{d} \leq 0.1$的百万年存活者中的53个移动到$0.3 \leq e_{d} \leq 0.5$区间。代表性的b+d构型在1亿年内保持可行，而包含c和广义相对论的对照组保留的系统较少。因此，外巨行星可以激发观测到的d的偏心率，同时将其可行轨道约束到顺行或逆行的近共面构型。
英文摘要
The nearby $π$ Mensae system contains the eccentric giant planet b on a 5.7 yr orbit, the 6.27 day transiting sub-Neptune c, and a candidate planet d on a 123 day orbit between them. Published estimates place the eccentricity of d between approximately 0.2 and 0.4. We reanalyze 772 published velocities with three-Keplerian fits and explore three-dimensional b-d dynamics with N-body integrations. The high-eccentricity solution persists when the phase or apsidal prior is widened; exact importance reweighting to a population-informed Beta eccentricity prior gives $e_{d}=0.378^{+0.050}_{-0.049}$. In 20 kyr integrations, 84.5% of configurations near the prograde and retrograde coplanar endpoints survive, compared with 21.3% across $60^\circ \leq I_{bd} < 120^\circ$; stellar collisions dominate the failures. Secular forcing by b moves 53 of 62 one-Myr survivors initialized with $e_{d} \leq 0.1$ into $0.3 \leq e_{d} \leq 0.5$. Representative b+d configurations remain viable for 100 Myr, whereas controls with c and general relativity retain fewer systems. The outer giant can therefore excite the observed eccentricity of d while constraining its viable orbit toward prograde or retrograde near-coplanar configurations.
