Eclipse timing variation of GK Vir: evidence of a possible Jupiter-like planet in a circumbinary orbit

TL;DR

This study analyzes eclipse timing variations in GK Vir, suggesting the presence of a Jupiter-like circumbinary planet with a ~24-year orbit, based on light travel time effect analysis and orbital stability considerations.

Contribution

It provides the first evidence of a possible Jupiter-like circumbinary planet around GK Vir using eclipse timing variations and LTT effect modeling.

Findings

Detected cyclic orbital period variation in GK Vir.

LTT effect with a circumbinary body best explains the OPV.

Estimated orbital period of the potential planet is ~24 years.

Abstract

Eclipse timing variation analysis has become a powerful method to discover planets around binary systems. We applied this technique to investigate the eclipse times of GK Vir. This system is a post-common envelope binary with an orbital period of 8.26 h. Here, we present 10 new eclipse times obtained between 2013 and 2020. We calculated the O-C diagram using a linear ephemeris and verified a clear orbital period variation (OPV) with a cyclic behavior. We investigated if this variation could be explained by the Applegate mechanism, the apsidal motion, or the light travel time (LTT) effect. We found that the Applegate mechanism would hardly explain the OPV with its current theoretical description. We obtained using different approaches that the apsidal motion is a less likely explanation than the LTT effect. We showed that the LTT effect with one circumbinary body is the most likely cause for the OPV, which was reinforced by the orbital stability of the third body. The LTT best solution provided an orbital period of ~24 yr for the outer body. Under the assumption of coplanarity between the external body and the inner binary, we obtained a Jupiter-like planet around the GK Vir. In this scenario, the planet has one of the longest orbital periods, with a full observational baseline, discovered so far. However, as the observational baseline of GK Vir is smaller than twice the period found in the O-C diagram, the LTT solution must be taken as preliminary.