HD 83443c: A highly eccentric giant planet on a 22-year orbit

TL;DR

This paper reports the discovery and characterization of a highly eccentric, long-period giant planet orbiting HD 83443, combining radial velocity data and Gaia/Hipparcos astrometry to analyze system stability and potential additional planets.

Contribution

It presents the first detailed dynamical analysis of HD 83443's planetary system, revealing a highly eccentric outer planet and possible stable regions for additional planets.

Findings

Discovered a giant planet with eccentricity 0.76 on a 22-year orbit.

Derived a dynamical mass of approximately 1.5 Jupiter masses.

Identified stable regions that could host additional planets, including within the habitable zone.

Abstract

We report the discovery of a highly eccentric long-period Jovian planet orbiting the hot-Jupiter host HD\,83443. By combining radial velocity data from four instruments (AAT/UCLES, Keck/HIRES, HARPS, Minerva-Australis) spanning more than two decades, we find evidence for a planet with m~sin~$i=1.35^{+0.07}_{-0.06}$\,\mj, moving on an orbit with $a=8.0\pm$0.8\,au and eccentricity $e=0.76\pm$0.05. We combine our radial velocity analysis with \textit{Gaia} eDR3 /\textit{Hipparcos} proper motion anomalies and derive a dynamical mass of $1.5^{+0.5}_{-0.2} M_{\rm Jup}$. We perform a detailed dynamical simulation that reveals locations of stability within the system that may harbor additional planets, including stable regions within the habitable zone of the host star. HD\,83443 is a rare example of a system hosting a hot Jupiter and an exterior planetary companion. The high eccentricity of HD\,83443c suggests that a scattering event may have sent the hot Jupiter to its close orbit while leaving the outer planet on a wide and eccentric path.