发表机构
Beihang University; Sun Yat-sen University; Universidad Diego Portales; Planetary Science Institute; Charles University; Lowell Observatory; Northern Arizona University（北京航空航天大学; 中山大学; 迭戈帕托莱斯大学; 行星科学研究所; 查理大学; 洛厄尔天文台; 北亚利桑那大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究结合多望远镜测光数据，确定天问二号目标天体Kamo`oalewa为非主轴旋转的细长型天体，给出最优LAM解及相关周期、角动量坐标，为其动力学与内部结构研究提供约束。
AI 中文摘要
(469219) Kamo`oalewa是最稳定的地球准卫星，也是中国天问二号小行星采样返回任务的目标天体。由于其体积小、旋转速度快，且地面可观测几何条件有限，Kamo`oalewa的许多物理性质仍未得到充分约束，包括旋转状态和形状。我们于2026年4月至5月用北双子座望远镜获取了Kamo`oalewa三个历元的高 cadence、高信噪比测光光变曲线，辅以2026年5月洛厄尔发现望远镜获取的一条光变曲线。分析表明，Kamo`oalewa处于非主轴旋转状态，形状呈细长型，存在四种可能的解，包括长轴模式（LAM）解、短轴模式（SAM）解及其对应的镜像角动量方向。最可取的解为LAM模型，其进动周期$P_\text{φ}=27.65\boxplus\text{min}$，旋转周期$P_\text{ψ}=50.49\boxplus0.08\text{min}$，角动量指向黄道坐标$(λ, β)=(226^\text{o}\boxplus20^\text{o}, -39^\text{o}\boxplus15^\text{o})$；尽管因混叠效应无法排除其他解或相近周期。我们还推导了LAM对应的凸形状反演，其旋转参数一致，但未找到SAM的满意反演结果。非主轴旋转为约束Kamo`oalewa的动力学历史或内部结构提供了额外条件。
英文摘要
(469219) Kamo`oalewa is the most stable Earth quasi-satellite and the target of China's Tianwen-2 asteroid sample return mission. Due to its small size, fast rotation, and the limited observing geometry accessible from the ground, many physical properties of Kamo`oalewa remain poorly constrained, including the rotational state and shape. We obtained three epochs of high-cadence, high signal-to-noise photometric lightcurves of Kamo`oalewa with the Gemini North Telescope from 2026 April to May, supplemented by one lightcurve from the Lowell Discovery Telescope in 2026 May. Our analysis suggests that Kamo`oalewa is in a non-principal-axis rotation with an elongated shape. Four possible solutions exist, including a long-axis mode (LAM) solution and a short-axis mode (SAM) solution, as well as their corresponding mirrored angular momentum directions. The most preferable solution has a LAM model with a precession period $P_ϕ=27.65\pm0.03~\text{min}$ and a rotational period $P_ψ=50.49\pm0.08~\text{min}$, and the angular momentum points to ecliptic coordinates $(λ, β) = (226^\mathrm{o}\pm20^\mathrm{o}, -39^\mathrm{o}\pm20\mathrm{o})$, although we cannot rule out other solutions or other close-by periods due to aliasing. We also derived a convex shape inversion for the LAM models with consistent rotational parameters but could not find a satisfactory inversion for the SAM models. The corresponding angular momentum points to $(λ, β)=(225^\mathrm{o}, -43^\mathrm{o})$, and the periods are $P_ϕ=27.90~\text{min}$ and $P_ψ=49.66~\text{min}$. The non-principal-axis rotation provides additional constraints on the dynamic history or the internal structure of Kamo`oalewa.
CommentsSubmitted to ApJL
