# Truly eccentric. I. Revisiting eight single-eccentric planetary systems

## TL;DR

This study reanalyzes eight single-eccentric planetary systems using new data and techniques, revealing additional long-period companions in four systems and emphasizing the importance of revisiting known systems to avoid false positives.

## Contribution

It provides new evidence for additional planets in known systems and demonstrates the value of reanalysis with updated data and methods.

## Key findings

- Four systems have new long-period companions.
- HD 65216c is a Jupiter analog with specific orbital parameters.
- Reanalysis can prevent false-positive detections of single eccentric planets.

## Abstract

We examine eight known single-eccentric planetary systems in light of recently released large data archives and new analysis techniques. For four of these systems (HD 7449, HD 65216, HD 89744, HD 92788) we find evidence for additional long-period companions. HD 65216c is a Jupiter analog, with a period of 14.7 yr, $e=0.18$, and m sin $i$ of 2M_Jup, whilst the remaining candidate companions move on as-yet-incomplete orbits. Our results highlight the importance of revisiting the analysis of known exoplanetary systems when new data become available, particularly given the possibility that poorly-sampled data might previously have led to the detection of a 'false-positive' single eccentric planet, when the system in question actually contains two (or more) planets on near-circular orbits.