The cataclysmic binary TT Arietis has been classified over the last years as an anti-dwarf nova (or VY Scl system, Ritter 1990). Some of the problems encountered in the investigation of the star, as is the case with most of the cataclysmic variables, are associated with finding reliable orbital parameters which are difficult to determine because of the complicated structure of the circumstellar matter, resulting in a great diversity of observational manifestations. Thus the questions about the TT Ari long-term behaviour of the 20-min, 3.2-hour and 4-day photometric periods, are still open in spite of the numerous contributions to the investigation of the brightness variability of the star.
Cowley et al. (1975) and Thorstensen et al. (1985) determined the spectroscopic orbital period of TT Ari to be . Smak & Stepien (1969) found regular brightness variations with a period in the high state and reported quasi-periodic variations with a time scale from 14 to 20 min.
The star became an object of intensive investigation after 1980, when its brightness decreased to and the transition to its first registered low state () begun. Until then, only irregular variations between and had been observed (Hudec et al. 1984). Udalski (1988) found an increase of the photometric period by about 0.15% from 1985 to 1986. Observations of Volpi et al. (1988), carried out in October 1986, are in favour of the period of for these modulations but the authors could not completely exclude the period . Hollander & van Paradijs (1992) established quasi-periodic brightness modulations with a period in their 1988 observing runs and confirmed the rapid period decrease, found by Semeniuk et al. (1987). They discussed the known accretion disc instability models and concluded that none of them could entirely explain this trend of the oscillations in TT Ari.
In this paper we present our photoelectric observations of TT Ari that provide information on the light-curve behaviour in the last ten years.