Orbital Stability in Multiple Stellar Systems: A Case Study of UZ Lyr

Eclipsing binaries provide precise stellar parameters and highly accurate eclipse times, making them valuable laboratories for detecting unseen companions and studying the dynamical architecture of multiple systems. The same timing and dynamical techniques are also widely used in searches for circumbinary planets, creating a direct methodological connection between studies of stellar multiplicity and exoplanetary systems. In particular, eclipse-timing variations constitute one of the most productive methods in terms of the number of circumbinary-planet candidates, making a broader understanding of the physical origins of these variations essential for interpreting potential planetary signals.

As a case study of companion detection and dynamical architecture in eclipsing binaries exhibiting timing variations, we examine UZ Lyr, an Algol-type system for which previous studies have suggested the presence of two additional stellar companions. In this work, we present a new analysis combining light-curve modeling, radial-velocity fitting, and a comprehensive eclipse-timing study. Using all available eclipse times from the literature and from space- and ground-based observations, we update the physical parameters of the binary, investigate the origin of the observed orbital-period variations, and model the timing residuals with two light-travel-time signals having periods of approximately 15 and 168 years. Long-term direct N-body integrations over approximately one billion years, performed with different numerical integrators and orbital geometries, show that the inferred two-companion configuration is dynamically stable.