TOI-3362b: A Proto-Hot Jupiter Undergoing High-Eccentricity Tidal Migration

TL;DR

This paper reports the discovery of TOI-3362b, a proto-Hot Jupiter with high eccentricity, providing evidence for high-eccentricity tidal migration as a pathway for hot Jupiter formation, and highlights its potential for atmospheric studies.

Contribution

It introduces TOI-3362b as a rare example of a proto-Hot Jupiter undergoing high-eccentricity tidal migration, supporting migration theories and encouraging further observational follow-up.

Findings

TOI-3362b has an eccentricity of 0.815.

The planet's orbit is expected to circularize at 0.051 au.

The system suggests high-eccentricity migration may be common.

Abstract

High-eccentricity tidal migration is a possible way for giant planets to be emplaced in short-period orbits. If it commonly operates, one would expect to catch proto-Hot Jupiters on highly elliptical orbits that are undergoing high-eccentricity tidal migration. As of yet, few such systems have been discovered. Here, we introduce TOI-3362b (TIC-464300749b), an 18.1-day, 5 $M_{\rm Jup}$ planet orbiting a main-sequence F-type star that is likely undergoing high-eccentricity tidal migration. The orbital eccentricity is 0.815$^{+0.023}_{-0.032}$. With a semi-major axis of 0.153$^{+0.002}_{-0.003}$ au, the planet's orbit is expected to shrink to a final orbital radius of 0.051$^{+0.008}_{-0.006}$ au after complete tidal circularization. Several mechanisms could explain the extreme value of the planet's eccentricity, such as planet-planet scattering and secular interactions. Such hypotheses can be tested with follow-up observations of the system, e.g., measuring the stellar obliquity and searching for companions in the system with precise, long-term radial velocity observations. The variation in the planet's equilibrium temperature as it orbits the host star and the tidal heating at periapse make this planet an intriguing target for atmospheric modeling and observation. Because the planet's orbital period of 18.1 days is near the limit of TESS's period sensitivity, even a few such discoveries suggest that proto-Hot Jupiters may be quite common.