A&A Supplement series, Vol. 122, April I 1997, 123-129
Received February 21; accepted May 31, 1996
Z. Kraicheva, V. Stanishev, L. Iliev, A. Antov, and V. Genkov
Send offprint request: Z. Kraicheva
Institute of Astronomy, Bulgarian Academy of Sciences, 72 Tsarigradsko Shosse Blvd., BG-1784 Sofia, Bulgaria
Results of photoelectric observations of TT Ari during the 1985-1994 interval are presented. Observations were carried out at the Rozhen and Belogradchik observatories as part of our programme for the study of anti-dwarf novae. The long-term light curve in the standard UBV system is constructed and peculiarities of the long-term behaviour of the star in this time interval are discussed. 21 moments of maxima and 14 moments of minima are added to the list of known maxima and minima of 3.2-hour modulations. The period of 3.2-hour modulations during the 1987/1988, 1989/1990 and 1990/1991 seasons is determined. In our 29 observing runs we searched for 20-min quasi-periodic variations, which were detected in 25 of them. Our results show that in 1989, the 20-min modulation mean period reached a local maximum of 19.45 min and declined afterwards. The mean brightness variability analysis during the aforementioned seasons confirmed the reliability of the period suspected by Semeniuk et al. (1987).
keywords: accretion, accretion disks -- stars: TT Ari -- stars: cataclysmic variables -- X-ray: stars