两个碰撞稀薄前星子的angular momentum和双星的形成
The angular momentum of two collided rarefied preplanetesimals and the formation of binaries
摘要：
本文研究了两个天体在行星形成早期碰撞时的平均角动量。主要关注的是在圆形日心轨道上的两个稀薄的前行星体（RPP）的情况。理论结果被用来开发模型的二进制或多个系统的形成从RPP，并解释了观察到的一个更大的部分二进制起源更远离太阳。在RPP阶段，小天体卫星可以通过两种方式形成：RPP之间的合并可以有两个收缩中心，或者从围绕主星或副星的圆盘形成卫星。盘的形成可能是由于合并形成的RPP的角动量大于固体的临界角动量。一个或几个主要的卫星（主要在低偏心率轨道上运动）可以在小于希尔半径的任何距离上从这个圆盘形成。第一种情况可以解释像2001 QW 322这样的系统，其中两个组件具有相似的质量，但相隔很远。通常，相互轨道的偏心率和倾角的任何值都是可能的。在已发现的双星中，观测到的角动量小于具有与已发现的双星相同总质量且在圆形日心轨道上相遇的相同RPP的典型角动量。这表明，在合并变得普遍之前，RPP的数量经历了一些收缩。
英文摘要：
This paper studies the mean angular momentum associated with the collision of two celestial objects in the earliest stages of planet formation. Of primary concern is the scenario of two rarefied preplanetesimals (RPPs) in circular heliocentric orbits. The theoretical results are used to develop models of binary or multiple system formation from RPPs, and explain the observation that a greater fraction of binaries originated farther from the Sun. At the stage of RPPs, small-body satellites can form in two ways: a merger between RPPs can have two centers of contraction, or the formation of satellites from a disc around the primary or the secondary. Formation of the disc can be caused by that the angular momentum of the RPP formed by the merger is greater than the critical angular momentum for a solid body. One or several satellites of the primary (moving mainly in low-eccentricity orbits) can be formed from this disc at any separation less than the Hill radius. The first scenario can explain a system such as 2001 QW322 where the two components have similar masses but are separated by a great distance. In general, any values for the eccentricity and inclination of the mutual orbit are possible. Among discovered binaries, the observed angular momenta are smaller than the typical angular momenta expected for identical RPPs having the same total mass as the discovered binary and encountering each other in circular heliocentric orbits. This suggests that the population of RPPs underwent some contraction before mergers became common.
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