Detection of a planetary system orbiting the eclipsing polar HU Aqr

TL;DR

This study reports the discovery of at least two giant planets orbiting the eclipsing polar HU Aqr, with evidence suggesting a possible third planet, based on precise eclipse timing measurements.

Contribution

First detection of multiple giant planets orbiting an eclipsing polar using eclipse timing variations, revealing potential planetary system architecture around such stars.

Findings

Two giant planets with masses of 5.9 and 4.5 M_Jup detected.

Planetary orbits at 3.6 AU and 5.4 AU with periods of 6.54 and 11.96 years.

Evidence suggests a third planet may be present based on period variations.

Abstract

Using the precise times of mid-egress of the eclipsing polar HU Aqr, we discovered that this polar is orbited by two or more giant planets. The two planets detected so far have masses of at least 5.9 and 4.5\,M_{Jup}. Their respective distances from the polar are 3.6 AU and 5.4 AU with periods of 6.54 and 11.96 years, respectively. The observed rate of period decrease derived from the downward parabolic change in O-C curve is a factor 15 larger than the value expected for gravitational radiation. This indicates that it may be only a part of a long-period cyclic variation, revealing the presence of one more planet. It is interesting to note that the two detected circumbinary planets follow the Titus-Bode law of solar planets with n=5 and 6. We estimate that another 10 years of observations will reveal the presence of the predicted third planet.