# In situ formation of hot Jupiters with companion super-Earths

**Authors:** Sanson T. S. Poon, Richard P. Nelson, Gavin A. L. Coleman  
**arXiv:** [2105.08553](https://arxiv.org/abs/2105.08553)  
**Date:** 2021-05-18  
**Summary page:** https://www.summarizepaper.com/en/paper/2105.08553v1/

## Key points

- The study examines the plausibility of in situ formation of multiple-planet systems that include a hot Jupiter and smaller planetary companions.
- Examples of such systems, like WASP-47, Kepler-730, and TOI-1130, have been confirmed through observations.
- $N$-body simulations are used to incorporate realistic treatments of collisions, an evolving protoplanetary disc, and eccentricity/inclination damping of planetary embryos.
- Two different models are used for the core of the giant planet: a 'seed-model' and an 'equal-mass-model'.
- Simulations based on the seed-model reveal that systems containing a hot Jupiter and super-Earths can be formed through four distinct phases: early giant impacts; runaway gas accretion onto the seed protoplanet; disc damping-dominated evolution of the embryos orbiting exterior to the giant planet; and a late chaotic phase after dispersal of the gas disc.
- Approximately 1% of simulations using the equal-mass model result in the formation of a giant planet following the same four-phase evolution.
- Synthetic transit observations from these simulations indicate an occurrence rate of 0.26% for systems with both a hot Jupiter and an inner super Earth.
- Simulated hot Jupiters are rarely detected as single transiting planets, which disagrees with observations.
- Some simulations produce two close-in giants resembling WASP 148 system.
- Overall, this study demonstrates that this particular scenario provides a viable pathway for forming systems with unusual architectures but does not apply to most hot Jupiters.

## Summary

The study examines the plausibility of in situ formation of multiple-planet systems that include a hot Jupiter and smaller planetary companions. The existence of such systems has been confirmed through observations, with examples like WASP-47, Kepler-730, and TOI-1130. The researchers employ $N$-body simulations that incorporate realistic treatments of collisions, an evolving protoplanetary disc, and eccentricity/inclination damping of planetary embryos. Two different models are used for the core of the giant planet: a 'seed-model' and an 'equal-mass-model'. In the seed-model, a more massive protoplanet is placed among multiple small embryos in a compact configuration. On the other hand, the equal-mass model consists only of equal-mass embryos. Simulations based on the seed-model reveal that systems containing a hot Jupiter and super-Earths can be formed. The evolution follows four distinct phases: early giant impacts; runaway gas accretion onto the seed protoplanet; disc damping-dominated evolution of the embryos orbiting exterior to the giant planet; and a late chaotic phase after dispersal of the gas disc. Approximately 1% of simulations using the equal-mass model result in the formation of a giant planet following the same four-phase evolution. Synthetic transit observations from these simulations indicate an occurrence rate of 0.26% for systems with both a hot Jupiter and an inner super Earth. This occurrence rate is similar to that derived from actual transit surveys (0.2%), but simulated hot Jupiters are rarely detected as single transiting planets which disagrees with observations. Additionally some simulations produce two close in giants resembling WASP 148 system. Overall this study demonstrates that this particular scenario provides a viable pathway for forming systems with unusual architectures but does not apply to most hot Jupiters.