1999AJ....117..574A

Observations of TT Ari obtained at 11 observatories (campaign TT Ari-94) during 258 hr were carried out to study optical variability on timescales from minutes to weeks. The best-fit primary photometric period determined from 16 nights of data obtained at the Dushak-Eregdag station of the Odessa State University is P=0{fd}133160±0{fd}000004 with a mean amplitude of 0.0513±0.0008 mag. This new primary photometric period is larger than that obtained during the TT Ari-88 campaign and is well outside the range of estimates published since 1961. Contrary to previous findings, the ``5-7 hr'' secondary photometric period is not seen. Our observations do show evidence for periods of 2{fd}916 and 0{fd}3040 with amplitudes of 43 and 25 mmag, respectively. The beat period between the spectroscopic and photometric periods is not seen. No coherent oscillations in the range f=10-2500 cycles.day^–1 are found. The highest peaks in the power spectrum cover the wide range of 24-139 cycles.day^–1. In the mean periodogram, the highest peak corresponds to 21 and 30 minutes for the largest sets of observations, i.e., those obtained at Odessa and Krakow Universities, respectively. In the instrumental B system, variations with an amplitude exceeding 0.011 mag occur 8 times (from 33 runs) at 24 minutes. We conclude that quasi-periodic variations occur at a few preferred timescales rather than at a relatively stable period with a secular decrease. In the frequency range 90-900 cycles.day^–1, the power spectrum obeys a power law with a slope ranging from γ=1.3 to 2.6 for different runs.