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arXiv 1012.2154astro-ph.EP
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2001年SN263和1994年CC近地小行星三重体的轨道：性质、起源和演化

Orbits of Near-Earth Asteroid Triples 2001 SN263 and 1994 CC: Properties, Origin, and Evolution

Julia Fang, Jean-Luc Margot, Marina Brozovic, Michael C. Nolan, Lance A. M. Benner, Patrick A. Taylor

备注：
17 pages, accepted to Astronomical Journal
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摘要：

三体模型与阿雷西博和戈德斯通雷达数据的拟合揭示了两个近地小行星三联体的性质。三颗小行星系统2001 SN 263的特征是一颗质量约为10^13 kg的主小行星，一颗质量约为1%的内卫星以约3个主半径在约0.7天内绕轨道运行，一颗质量约为2.5%的外卫星以约13个主半径在约6.2天内绕轨道运行。1994 CC是一个较小的系统，其主恒星质量约为2.6 \times 10^11 kg，两颗卫星的质量约为主恒星质量的2%和1%，轨道距离约为主恒星半径的5.5和19.5倍。它们的轨道周期分别为~1.2天和~8.4天。共振参数的检查表明，卫星目前没有处于平均运动共振。在两个系统（2001 SN 263内天体：d{ \varpi }/dt ~1.1 deg/day，1994 CC内天体：d{ \varpi }/dt ~ -0.2 deg/day）中都检测到了拱点和节点的岁差，这与相互作用轨道和主扁率引起的长期演化的分析预测相一致。卫星轨道平面之间的非零相互倾角提供了两个系统中数据的最佳拟合（2001 SN 263：~14度，1994 CC：~16度）。我们的最佳拟合轨道是一致的近圆周运动，除了1994年CC的外卫星，它有一个偏心轨道的e ~ 0.19。我们研究了几个过程，可以产生所观察到的偏心率和倾角，包括Kozai和evection共振，过去的平均运动共振交叉，并密切接触类地行星。特别是，我们发现，近距离的行星相遇可以很容易地激发偏心率和相互倾斜的卫星的轨道，目前观察到的值。

英文摘要：

Three-body model fits to Arecibo and Goldstone radar data reveal the nature of two near-Earth asteroid triples. Triple-asteroid system 2001 SN263 is characterized by a primary of ~10^13 kg, an inner satellite ~1% as massive orbiting at ~3 primary radii in ~0.7 days, and an outer satellite ~2.5% as massive orbiting at ~13 primary radii in ~6.2 days. 1994 CC is a smaller system with a primary of mass ~2.6 \times 10^11 kg and two satellites ~2% and ~1% as massive orbiting at distances of ~5.5 and ~19.5 primary radii. Their orbital periods are ~1.2 and ~8.4 days. Examination of resonant arguments shows that the satellites are not currently in a mean-motion resonance. Precession of the apses and nodes are detected in both systems (2001 SN263 inner body: d{\varpi}/dt ~1.1 deg/day, 1994 CC inner body: d{\varpi}/dt ~ -0.2 deg/day), which is in agreement with analytical predictions of the secular evolution due to mutually interacting orbits and primary oblateness. Nonzero mutual inclinations between the orbital planes of the satellites provide the best fits to the data in both systems (2001 SN263: ~14 degrees, 1994 CC: ~16 degrees). Our best-fit orbits are consistent with nearly circular motion, except for 1994 CC's outer satellite which has an eccentric orbit of e ~ 0.19. We examine several processes that can generate the observed eccentricity and inclinations, including the Kozai and evection resonances, past mean-motion resonance crossings, and close encounters with terrestrial planets. In particular, we find that close planetary encounters can easily excite the eccentricities and mutual inclinations of the satellites' orbits to the currently observed values.

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