The Curious Case of HU Aquarii - Dynamically Testing Proposed Planetary Systems

TL;DR

This paper critically examines proposed planetary systems around HU Aquarii, demonstrating their dynamical instability and emphasizing caution in interpreting eclipse-timing variations as planetary signals.

Contribution

It provides a detailed dynamical stability analysis of proposed planets around HU Aquarii and re-evaluates the data with rigorous methods, challenging previous claims.

Findings

Proposed planetary systems are dynamically unfeasible.

Re-analysis yields different orbital solutions that are also unstable.

Eclipse-timing variations may have alternative explanations.

Abstract

In early 2011, the discovery of two planets moving on surprisingly extreme orbits around the eclipsing polar cataclysmic variable system HU Aquraii was announced based on variations in the timing of mutual eclipses between the two central stars. We perform a detailed dynamical analysis of the stability of the exoplanet system as proposed in that work, revealing that it is simply dynamically unfeasible. We then apply the latest rigorous methods used by the Anglo-Australian Planet Search to analyse radial velocity data to re-examine the data used to make the initial claim. Using that data, we arrive at a significantly different orbital solution for the proposed planets, which we then show through dynamical analysis to be equally unfeasible. Finally, we discuss the need for caution in linking eclipse-timing data for cataclysmic variables to the presence of planets, and suggest a more likely explanation for the observed signal.