The Kepler space mission has detected a large number of exoplanets in multiple transiting planet systems. Previous studies found that these Kepler multiple planet systems exhibit an intra-system uniformity, namely planets in the same system have similar sizes and correlated orbital spacings. However, it is important to consider the possible role of selection effects due to observational biases. In this paper, we revisit the orbital spacing aspect of the pattern after taking observational biases into account using a forward modeling method. We find that orbital spacings, in terms of period ratios, of Kepler multiple planet systems are significantly correlated only for those tightly packed systems, and the transition from correlation to non-correlation is abrupt with a boundary at mean period ratio $\overline{PR}$ $\sim 1.5 - 1.7$. In this regard, the pattern of orbital spacing is more like a dichotomy rather than a global correlation. Furthermore, we find that such an apparent orbital spacing dichotomy could be essentially a projection of a dichotomy that related to mean motion resonance (MMR), which we dub as MMR dichotomy, and itself could be a natural result of planet migration and dynamical evolution.

中文翻译：

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关于开普勒多行星系统的轨道间距模式

开普勒太空任务在多个过境行星系统中发现了大量系外行星。先前的研究发现，这些开普勒多行星系统表现出系统内均匀性，即同一系统中的行星具有相似的大小和相关的轨道间距。然而，重要的是要考虑由于观察偏差导致的选择效应的可能作用。在本文中，我们在使用前向建模方法将观测偏差考虑在内后，重新审视了该模式的轨道间距方面。我们发现，就周期比而言，开普勒多行星系统的轨道间距仅与那些紧密堆积的系统显着相关，并且从相关到非相关的过渡是突然的，边界为平均周期比 $\overline{PR }$ $\sim 1.5 - 1.7$。在这方面，轨道间距的模式更像是二分法，而不是全局相关性。此外，我们发现这种明显的轨道间距二分法本质上可能是与平均运动共振 (MMR) 相关的二分法的投影，我们称之为 MMR 二分法，其本身可能是行星迁移和动力演化的自然结果。