Can Cold Jupiters Sculpt the Edge-of-the-Multis?

TL;DR

This study investigates whether distant giant planets can explain the observed sharp outer edges of compact multi-planet systems, concluding that such sculpting by giant planets is unlikely based on current detection constraints.

Contribution

The paper provides a dynamical analysis of hypothetical outer giant planets' role in shaping the edges of compact multis, finding they are unlikely to be the primary cause.

Findings

Distant giant planets would need specific parameters to sculpt system edges.

Such planets would be detectable via transit and radial velocity methods.

Current observational constraints make giant planet sculpting unlikely.

Abstract

Compact systems of multiple close-in super-Earths/sub-Neptunes ("compact multis") are a ubiquitous outcome of planet formation. It was recently discovered that the outer edges of compact multis are located at smaller orbital periods than expected from geometric and detection biases alone, suggesting some truncation or transition in the outer architectures. Here we test whether this "edge-of-the-multis" might be explained in any part by distant giant planets in the outer regions ($\gtrsim 1$ AU) of the systems. We investigate the dynamical stability of observed compact multis in the presence of hypothetical giant ($\gtrsim 0.5 \ M_{\mathrm{Jup}}$) perturbing planets. We identify what parameters would be required for hypothetical perturbing planets if they were responsible for dynamically sculpting the outer edges of compact multis. "Edge-sculpting" perturbers are generally in the range $P\sim100-500$ days for the average compact multi, with most between $P\sim200-300$ days. Given the relatively close separation, we explore the detectability of the hypothetical edge-sculpting perturbing planets, finding that they would be readily detectable in transit and radial velocity data. We compare to observational constraints and find it unlikely that dynamical sculpting from distant giant planets contributes significantly to the edge-of-the-multis. However, this conclusion could be strengthened in future work by a more thorough analysis of the detection yields of the perturbing planets.