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arXiv 2001.01390astro-ph.EP
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关于同步双星小行星的伴星自转

On the Secondary's Rotation in Synchronous Binary Asteroid

Haishuo Wang, Xiyun Hou

摘要:

本文研究了同步双星系统中,次级小行星进入1:1自旋轨道共振时,次级小行星的自转。所使用的模型是由一个球形的主要加上一个三轴椭球次要的平面完整的两体问题。与经典的自旋-轨道方法相比,本文有两个不同之处:(1)考虑了次级粒子转动对相互轨道的影响;(2)采用周期轨道方法代替了哈密顿方法。我们的研究发现:(1)这两族周期轨道的谱系与限制性三体问题中三角平动点附近周期轨道族的谱系相同。(2)在次级质量可以忽略的极限情况下,通过将长周期轨道与自由天平动等价,将短周期轨道与轨道偏心率引起的强迫天平动等价,我们的结果可以简化为经典的自旋轨道理论。然而,当次级质量不可忽略时,两种模型表现出明显的差异。(3)通过对周期轨道稳定性的研究,对于特定的双星系统,我们可以得到双星系统的最大平动振幅(通常小于90 °),以及不破坏双星系统同步状态的最大轨道互偏心率。我们还发现了次级天体的平动振幅与轨道偏心率之间的反相关。并以(65803)Didymos系统为例说明了结果。

英文摘要:

This paper studies the secondary's rotation in a synchronous binary asteroid system in which the secondary enters the 1:1 spin-orbit resonance. The model used is the planar full two-body problem composed of a spherical primary plus a tri-axial ellipsoid secondary. Compared with classical spin-orbit work, there are two differences: (1) Influence on the mutual orbit from the secondary's rotation is considered; (2) Instead of the Hamiltonian approach, the approach of periodic orbits is adopted. Our studies find: (1) Genealogy of the two families of periodic orbits is same as that of the families around triangular libration points in the restricted three-body problem. That is, the long-period family terminates onto a short-period orbit travelling N times; (2) In the limiting case where the secondary's mass is negligible, our results can be reduced to the classical spin-orbit theory, by equating the long-period orbit with the free libration, and by equating the short-period orbit with the forced libration caused by orbit eccentricity. However, the two models show obvious differences when the secondary's mass is non-negligible. (3) By studying the stability of periodic orbits, for a specific binary asteroid system, we are able to obtain the maximum libration amplitude of the secondary (which is usually less than 90 degree), and the maximum mutual orbit eccentricity which does not break the secondary's synchronous state. We also find the anti-correlation between the secondary's libration amplitude and the orbit eccentricity. The (65803) Didymos system is taken as an example to show the results.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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