Inner Planetary System Gap Complexity is a Predictor of Outer Giant Planets

The connection between inner small planets and outer giant planets is crucial to our understanding of planet formation across a wide range of orbital separations. While Kepler provided a plethora of compact multiplanet systems at short separations (≲1 au), relatively little is known about the occurrence of giant companions at larger separations and how they impact the architectures of the inner systems. Here, we use the catalog of systems from the Kepler Giant Planet Search to study how the architectures of the inner transiting planets correlate with the presence of outer giant planets. We find that for systems with at least three small transiting planets, the distribution of inner-system gap complexity (${ \mathcal C }$), a measure of the deviation from uniform spacings, appears to differ (p ≲ 0.02) between those with an outer giant planet ($50{M}_{\oplus }\leqslant {M}_{p}\sin i\leqslant 13{M}_{\mathrm{Jup}}$) and those without any outer giants. All four inner systems (with three or more transiting planets) with outer giant(s) have a higher gap complexity (${ \mathcal C }\gt 0.32$) than 79% (19/24) of the inner systems without any outer giants (median ${ \mathcal C }\simeq 0.06$). This suggests that one can predict the occurrence of outer giant companions by selecting multitransiting systems with highly irregular spacings. We do not find any correlation between the outer giant occurrence and the size (similarity or ordering) patterns of the inner planets. The higher gap complexities of inner systems with an outer giant hints that massive external planets play an important role in the formation and/or disruption of the inner systems.