A period study of the RS CVn-type binary ER Vulpeculae

Many available published times of light minima of the late-type binary system ER Vul have been compiled and analyzed using a new method proposed by Kalimeris et al. (1994). It was shown that the orbital period of the system oscillation with a period of about 30.6 years and an amplitude of 3.2 x 10(-6) days while it undergoes a constant period decrease of about dP/P = 7.84 x 10(-8) day/year. The prospective physical mechanisms that could have modulated the orbital period behaviour (periodic or non-periodic), have been studied. We found that a combination of a magnetic activity cycle mechanism and an enhanced stellar wind could explain satisfactorily the period change.