# TOI-216b and TOI-216c: Two warm, large exoplanets in or slightly wide of the 2:1 orbital resonance

## TL;DR

This paper confirms and characterizes a pair of warm, large exoplanets orbiting TOI-216, exploring their possible resonant configurations and implications for planetary formation theories.

## Contribution

It provides the first detailed analysis of the TOI-216 system, identifying two potential orbital solutions and discussing their formation scenarios and future observational prospects.

## Key findings

- Two families of orbital solutions identified.
- Preference for the Jupiter-Neptune resonance configuration.
- System's eccentricities and inclinations suggest undetected planets.

## Abstract

Warm, large exoplanets with 10-100 day orbital periods pose a major challenge to our understanding of how planetary systems form and evolve. Although high eccentricity tidal migration has been invoked to explain their proximity to their host stars, a handful reside in or near orbital resonance with nearby planets, suggesting a gentler history of in situ formation or disk migration. Here we confirm and characterize a pair of warm, large exoplanets discovered by the TESS Mission orbiting K-dwarf TOI-216. Our analysis includes additional transits and transit exclusion windows observed via ground-based follow-up. We find two families of solutions, one corresponding to a sub-Saturn-mass planet accompanied by a Neptune-mass planet and the other to a Jupiter in resonance with a sub-Saturn-mass planet. We prefer the second solution based on the orbital period ratio, the planet radii, the lower free eccentricities, and libration of the 2:1 resonant argument, but cannot rule out the first. The free eccentricities and mutual inclination are compatible with stirring by other, undetected planets in the system, particularly for the second solution. We discuss prospects for better constraints on the planets' properties and orbits through follow-up, including transits observed from the ground.