Stability of additional planets in and around the habitable zone of the HD 47186 Planetary System

TL;DR

This study investigates the potential for additional terrestrial-like planets within the habitable zone of the HD 47186 system, using dynamical simulations to identify stable regions where such planets could exist.

Contribution

It provides the first detailed dynamical analysis of the stability of potential additional planets in the HD 47186 system, especially within the habitable zone.

Findings

Much of the habitable zone can host a 10 Earth-mass planet.

A 10 Earth-mass planet at 0.8 AU could be detectable with current radial-velocity methods.

Two 10 Earth-mass planets could coexist if their eccentricities are below 0.3.

Abstract

We study the dynamical stability of an additional, potentially habitable planet in the HD 47186 planetary system. Two planets are currently known in this system: a "hot Neptune" with a period of 4.08 days and a Saturn-mass planet with a period of 3.7 years. Here we consider the possibility that one or more undetected planets exist between the two known planets and possibly within the habitable zone in this system. Given the relatively low masses of the known planets, additional planets could have masses $\lsim 10 \mearth$, and hence be terrestrial-like and further improving potential habitability. We perform $N$-body simulations to identify the stable zone between planets $b$ and $c$ and find that much of the inner habitable zone can harbor a $10 \mearth$ planet. With the current radial-velocity threshold of $\sim 1$ m/s, an additional planet should be detectable if it lies at the inner edge of the habitable zone at 0.8 AU. We also show that the stable zone could contain two additional planets of $10 \mearth$ each if their eccentricities are lower than $\sim 0.3$.