Possible detection of two giant extrasolar planets orbiting the eclipsing polar UZ Fornacis

TL;DR

This study analyzes 27 years of eclipse data from UZ For to detect orbital period variations, suggesting two possible giant planets or magnetic cycles as causes, with the planetary hypothesis being more plausible but not definitive.

Contribution

First long-term analysis of eclipse timing variations in UZ For suggesting potential planetary companions or magnetic activity cycles as causes.

Findings

Detected ~60 s deviations from linear/quadratic trends in eclipse timings.

Identified two cyclic variations with periods of approximately 16 and 5.25 years.

Proposed two giant planets or magnetic cycles as possible explanations.

Abstract

We present new high-speed, multi-observatory, multi-instrument photometry of the eclipsing polar UZ For in order to measure precise mid-eclipse times with the aim of detecting any orbital period variations. When combined with published eclipse times and archival data spanning ~27 years, we detect departures from a linear and quadratic trend of ~60 s. The departures are strongly suggestive of two cyclic variations of 16(3) and 5.25(25) years. The two favoured mechanisms to drive the periodicities are either two giant extrasolar planets as companions to the binary (with minimum masses of 6.3(1.5)M(Jupiter) and 7.7(1.2)M(Jupiter)) or a magnetic cycle mechanism (e.g. Applegate's mechanism) of the secondary star. Applegate's mechanism would require the entire radiant energy output of the secondary and would therefore seem to be the least likely of the two, barring any further refinements in the effect of magnetic fieilds (e.g. those of Lanza et al.). The two planet model can provide realistic solutions but it does not quite capture all of the eclipse times measurements. A highly eccentric orbit for the outer planet would fit the data nicely, but we find that such a solution would be unstable. It is also possible that the periodicities are driven by some combination of both mechanisms. Further observations of this system are encouraged.