Apsidal motion and light-time effect in the eclipsing binaries RU Monocerotis and DR Vulpeculae

We present a period analysis of the two early-type and well-known eccentric eclipsing binaries RU Mon (P = 3.(d)58, e = 0.45) and DR Vul (P = 2.(d)25, e = 0.10). Several new times of minimum light recorded with photoelectric means have been gathered. The O - C diagrams are analyzed using all reliabl e timings found in the literature and new values for the elements of the ap sidal motion and light-time effect are computed. We confirmed the very shor t period of apsidal motion of about 36.3 years for DR Vul. The third bodies have an orbital period of about 73 and 63 years for RU Mon and DR Vul, res pectively.