A simultaneous X-ray and optical study of TT ARIETIS during its active state - X-ray observations and discussion

We present results of X-ray observations of TT Ari with the EXOSAT satellite on August 21/22, 1985. This paper represents the second part of the publication of the results obtained with our extended program of optical monitoring and simultaneous optical and X-ray observations of TT Ari. For the first part, which includes optical results, see Wenzel et al. (1992). Optical photometric and partly spectroscopic data were obtained at more than 10 observatories. The measurements were carried out immediately after the return of TT Ari to its optically active (high) state after being more than 5.5 years in the very low state. The results represent the first detailed simultaneous X-ray and optical study of TT Ari in the high state. The most important results of our analysis are (i) the mean X-ray flux was found to be surprisingly stable over long time intervals, not changing by more than several tens of per cent and not reflecting the large optical intensity changes between the active and inactive states and (ii) absorption dips were detected in the light curve. The results are discussed from the point of view of the model of the system.