PHOTOMETRY OF EP LYRAE AND PERIOD CHANGES IN RV TAURI STARS

The RV Tauri variable EP Lyrae was observed between 1985 and 1992 in t he UBV-system. The star, like AC Herculis, has a relatively regular li ght curve. Its period is rather stable during most of the observations , its current value is 83.46(d). EP Lyrae is classified as an RVB vari able, i.e. its mean brightness is supposed to vary. It is shown that t his classification is not correct, the mean brightness of the star is constant. The question of period changes in RV Tauri stars is discusse d and a possible relation between colour and O-C amplitude is found. T he difficulties with the usually assumed post-AGE evolutionary status of these variables are also highlighted.