# Evidence for Hidden Nearby Companions to Hot Jupiters

## TL;DR

This study reveals that a significant fraction of hot Jupiters have nearby planetary companions, challenging the high-eccentricity migration model and supporting a quiescent formation scenario involving post-disk dynamical sculpting.

## Contribution

It provides new evidence from Kepler data showing the presence of nearby companions to hot Jupiters, proposing an eccentric migration framework for their formation.

## Key findings

- At least 12±6% of hot Jupiters have nearby companions.
- Over 70% of warm Jupiters have nearby companions.
- Supports a quiescent formation scenario over high-eccentricity migration.

## Abstract

The first discovered extrasolar worlds -- giant, ``hot Jupiter'' planets on short-period orbits -- came as a surprise to solar-system-centric models of planet formation, prompting the development of new theories for planetary system evolution. The near-absence of observed nearby planetary companions to hot Jupiters has been widely quoted as evidence in support of high-eccentricity tidal migration: a framework in which hot Jupiters form further out in their natal protoplanetary disks before being thrown inward with extremely high eccentricities, stripping systems of any close-in planetary companions. In this work, we present new results from a search for transit timing variations across the full four-year Kepler dataset, demonstrating that at least $12\pm6\%$ of hot Jupiters have a nearby planetary companion. This subset of hot Jupiters is expected to have a quiescent dynamical history such that the systems could retain their nearby companions. We also demonstrate a ubiquity of nearby planetary companions to warm Jupiters ($\geq70\pm{16}\%$), indicating that warm Jupiters typically form quiescently. We conclude by combining our results with existing observational constraints to propose an ``eccentric migration'' framework for the formation of short-period giant planets through post-disk dynamical sculpting in compact multi-planet systems. Our framework suggests that hot Jupiters constitute the natural end stage for giant planets spanning a wide range of eccentricities, with orbits that reach small enough periapses -- either from their final orbital configurations in the disk phase, or from eccentricity excitation in the post-disk phase -- to trigger efficient tidal circularization.