One, two or three stars? An investigation of an unusual eclipsing binary candidate undergoing dramatic period changes

TL;DR

This study investigates the unusual eclipsing binary candidate 1SWASP J234401.81-212229.1, exploring various models to explain its dramatic period changes and concluding a hierarchical triple system is most probable.

Contribution

It provides a detailed analysis of a peculiar variable star, proposing the most plausible model as a hierarchical triple system based on combined photometric and spectroscopic data.

Findings

Spectroscopic data did not support a normal binary interpretation.

Cyclic period variations suggest complex system dynamics.

Hierarchical triple system model is most consistent with observations.

Abstract

We report our investigation of 1SWASP J234401.81-212229.1, a variable with a 18461.6 s period. After identification in a 2011 search of the SuperWASP archive for main-sequence eclipsing binary candidates near the distribution's short-period limit of approx. 0.20 d, it was measured to be undergoing rapid period decrease in our earlier work, though later observations supported a cyclic variation in period length. Spectroscopic data obtained in 2012 with the Southern African Large Telescope did not, however, support the interpretation of the object as a normal eclipsing binary. Here, we consider three possible explanations consistent with the data: a single-star oblique rotator model in which variability results from stable cool spots on opposite magnetic poles; a two-star model in which the secondary is a brown dwarf; and a three-star model involving a low-mass eclipsing binary in a hierarchical triple system. We conclude that the latter is the most likely model.