Revisiting the proposed planetary system orbiting the eclipsing polar HU Aquarii

TL;DR

This study re-analyzes eclipse timing data of HU Aquarii, finding that proposed planets are dynamically unstable and suggesting intrinsic stellar properties may explain observed signals rather than planets.

Contribution

It provides a detailed re-analysis of eclipse timings and dynamical stability, challenging previous planetary claims around HU Aquarii and proposing alternative explanations.

Findings

Proposed planets are dynamically unstable within 10^4 years.

Eclipse timing variations may result from stellar properties, not planets.

A stable two-planet solution can fit the data without additional bodies.

Abstract

It has recently been proposed, on the basis of eclipse-timing data, that the eclipsing polar cataclysmic variable HU Aquarii is host to at least two giant planets. However, that result has been called into question based upon the dynamical stability of the proposed planets. In this work, we present a detailed re-analysis of all eclipse timing data available for the HU Aquarii system, making use of standard techniques used to fit orbits to radial-velocity data. We find that the eclipse timings can be used to obtain a two-planet solution that does not require the presence of additional bodies within the system. We then perform a highly detailed dynamical analysis of the proposed planetary system. We show that the improved orbital parameters we have derived correspond to planets that are dynamically unstable on unfeasibly short timescales (of order 10^4 years or less). Given these results, we discuss briefly how the observed signal might in fact be the result of the intrinsic properties of the eclipsing polar, rather than being evidence of dynamically improbable planets. Taken in concert, our results highlight the need for caution in interpreting such timing variations as being planetary in nature.