2019RAA....19..107W

TZ Eri and TU Her are both classic Algol-type systems (Algols). By observing and collecting times of minimum light, we constructed the O - C curves for the two systems. The long-time upward and downward parabolas shown in these diagrams are considered to be the result of the combination of mass transfer and angular momentum loss. The secular orbital period change rates are dP/dt = 4.74(±0.12) x 10^–7 d yr ^–1 and dP/dt = -2.33(±0.01) x 10^–6 d yr^–1, respectively. There are also cyclic variations in their O - C curves which might be caused by the light-travel time effect (LTTE). A circumbinary star may exist in the TZ Eri system with a mass of at least 1.34 M_☉, while there are possibly two celestial bodies almost run in a 2 : 1 resonance orbit around the TU Her binary pair. Their masses are at least 2.43 M_☉ and 1.27 M_☉.