Active binary R Arae revisited: Bringing the secondary component to light and physical modelling of the circumstellar material

The spectral lines of the secondary component of the active binary system R Ara were uncovered for the first time, which allowed directly to determine the parameters of the spectroscopic orbit. The mass ratio of the system is updated to a new observational value of M 2/M 1 = 0.305 ± 0.005 which is ∼20 per cent smaller than the literature value (M 2/M 1 = 0.39). Modelling the reconstructed component spectra yielded the equatorial rotational velocities of the components as v rot1 = 202 km s−1 and v rot2 = 73 km s−1 indicating a very fast rotation (∼5 times faster than the synchronous rotation velocity) for the primary and synchronous rotation for the secondary component. The circumstellar material in the system was investigated using the Hipparcossatellite data and the high-resolution (R ∼ 41 000) spectral data. According to our model, there is always material transferring from the secondary component on to the primary causing a hot region on its surface. The structural difference between the spectra taken at the same orbital phase but at different epochs proved that the density and the velocity of the transferring material are variable. There are three main trends in the light curve and spectral line variations suggesting the activity cycles for the system, namely quiescent, moderate and, active cycles. It was estimated that the circumstellar material around could be extended to large distances up to 40 R⊙ from the system.