Variability on all time scales between seconds and decades is typical for cataclysmic variables ( CVs ) .
One of the brightest and best studied CVs is TT Ari , a nova-like variable which belongs to the VY Scl subclass , characterized by occasional low states in their light curves .
It is also known as a permanent superhumper at high state , revealing “ positive ” ( P _ { S } > P _ { 0 } ) as well as “ negative ” ( P _ { S } < P _ { 0 } ) superhumps , where P _ { S } is the period of the superhump and P _ { 0 } the orbital period .
TT Ari was observed by the Canadian space telescope MOST for about 230 hours nearly continuously in 2007 , with a time resolution of 48 seconds .
Here we analyze these data , obtaining a dominant “ negative ” superhump signal with a period P _ { S } = 0.1331 days and a mean amplitude of 0.09 mag .
Strong flickering with amplitudes up to 0.2 mag and peak-to-peak time scales of 15–20 minutes is superimposed on the periodic variations .
We found no indications for significant quasi-periodic oscillations with periods around 15 minutes , reported by other authors .
We discuss the known superhump behaviour of TT Ari during the last five decades and conclude that our period value is at the upper limit of all hitherto determined “ negative ” superhump periods of TT Ari , before and after the MOST run .