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

Abstract

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 (  ), a measure of the deviation from uniform spacings, appears to differ (p ≲ 0.02) between those with an outer giant planet ( 50 M ⊕ ≤ M p sin i ≤ 13 M 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 (  > 0.32 ) than 79% (19/24) of the inner systems without any outer giants (median  ≃ 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.

The Metallicity Dimension of the Super Earth-cold Jupiter Correlation

“…The current planet sample remains too small to fully establish the correlation between inner small planets and outer giant planets and explore its dependence on properties of the host stars and the planetary systems (see some early attempts by Zhu 2019 andWeiss 2023), making it difficult to test predictions of formation models (e.g., Schlecker et al 2021;Best et al 2024;Bitsch & Izidoro 2023). The ongoing RV follow-up observations of transiting systems (e.g., Bonomo et al 2023;Van Zandt et al 2023;Weiss et al 2024) and upcoming Gaia astrometric detections (e.g., Perryman et al 2014;Espinoza-Retamal et al 2023) aided by careful statistical analysis will be helpful in this regard.…”

Variations in the Radius Distribution of Single- and Compact Multiple-transiting Planets

“…Chance et al (2022) found a larger rate of giant impacts for single-transiting systems, which could produce an offset in the radius between single-and multiple-transiting systems. He & Weiss (2023) quantified an impact upon inner system architecture from the presence of an outer giant planet; potentially the presence of an outer companion could also change planet size as well as planetary spacing. Singletransiting systems may have an unknown outside companion in their system that constrains the growth of the inner transiting planet.…”

Peas-in-a-pod across the Radius Valley: Rocky Systems Are Less Uniform in Mass but More Uniform in Size and Spacing

“…Each of the paradigms thus discussed present comparatively quiescent and lowerentropy dynamical pathways for the assembly of volatile-rich worlds compared to their rocky counterparts, thereby collectively arguing for a greater uniformity in planetary spacing for the former in direct opposition to the trends presented in this work. It has been recently demonstrated that the presence of giant planetary companions can disrupt the spacing uniformity of the inner system (He & Weiss 2023) though such a starkly preferential occurrence of these companions for volatile-rich systems cannot be accurately constrained with regard to our primary samples. As such, it remains to be determined if further analytical frameworks or simulations may successfully recover this surprising dichotomy in spacing uniformity.…”