SIMBAD references

Several new times of minima, based on photoelectric observations, have been secured for two bright and well-known eclipsing binaries with eccentric orbits and with very similar orbital periods: HS Her (P=1.637d, e=0.02) and U Oph (P=1.677d, e=0.003). For HS Her, an apsidal motion with a period of 78 years is confirmed and a third body in an eccentric orbit with a period of 85 years is found. An analysis of all available eclipse timings of U Oph has confirmed the presence of an apsidal motion with one of the shortest known periods (20.1yr) and a light-time effect with the improved period of 37.6yr. The corresponding internal structure constants log k₂ were also derived. It is estimated that the tertiaries of both systems are detectable via speckle interferometry.