THE ALGOL SYSTEM SZ HERCULIS: PHYSICAL NATURE AND ORBITAL BEHAVIOR

Multiband CCD photometric observations of SZ Her were obtained between 2008 February and May. The light curve was completely covered and indicated a significant temperature difference between both components. The light-curve synthesis presented in this paper indicates that the eclipsing binary is a classical Algol-type system with parameters of q = 0.472, i = 87.°57, and Δ(T1 – T2) = 2381 K; the primary component fills approximately 77% of its limiting lobe and is slightly larger than the lobe-filling secondary component. More than 1100 times of minimum light spanning more than a century were used to study an orbital behavior of the binary system. It was found that the orbital period of SZ Her varied due to a combination of two periodic variations with cycle lengths of P3 = 85.8 yr and P4 = 42.5 yr and semi-amplitudes of K3 = 0.013 days and K4 = 0.007 days, respectively. The most reasonable explanation for these variations is a pair of light-time effects driven by the possible existence of two M-type companions with minimum masses of M3 = 0.22 M☉ and M4 = 0.19 M☉ that are located close to the 2:1 mean motion resonance. If two additional bodies exist, then the overall dynamics of the multiple system may provide a significant clue to the formation and evolution of the eclipsing pair.