The correlated X-ray and optical time variability of TT Arietis

The results of Einstein X-ray observation and simultaneous optical observations of the cataclysmic variable TT Arietis extending over several binary orbits are reported. Evidence is found for correlations between the X-ray and optical variability of TT Ari on three distinct time scales: the 3.3 hour variability that has been associated with the orbital period of the star, the about 1000 s time scale of the irregular flickering activity, and the time scale of quasi-coherent oscillations which have periods of order 10 s. There is a modulation of the X-ray flux with a period consistent with the orbital period of approximately 200 minutes, but there is no apparent modulation of the X-ray spectrum. The optical flux is modulated with a similar period and may lag the X-ray modulation by about 0.1 in phase. The X-ray spectrum is well fitted by a thermal bremsstrahlung plus Gaunt factor model. The results suggest that the hard X-ray emission may be produced in a corona above and below the inner accretion disk.