We analyse the CoRoT and V-passband ground-based light curves of the interacting close binary AU Mon, assuming that there is a geometrically and optically thick accretion disc around the hotter and more massive star, as inferred from the photometric and spectroscopic characteristics of the binary. Our model fits the observations very well and provides estimates for the orbital elements and physical parameters of the components and of the accretion disc.

No abstract

Abstract. We present a solution for the long standing problem concerning the "chromospheric" behaviour of the Mn i 5395/5432Å lines in the solar spectrum using multi-line/multi-species NLTE modelling. Using comprehensive spectral line formation modelling, we show that the Mn i lines are very sensitive to optical pumping in a transition which overlaps with Mg ii k. It therefore follows that one has to be careful with the choice of lines as temperature indicators and for the determination of the Mn abundances although on the other hand, due to the formation process of these lines they may be useful as a solar and stellar activity diagnostic.

The UBVR light curves of the massive eclipsing binary RY Sct, obtained at the Maidanak Observatory from 1979 to 1992, have been re-analyzed in order to prove the hypothesis of the presence of an accretion disk in the system. This hypothesis is supported by a new spectroscopic study of Grundstrom et al., and by a specific light-curve shape exhibiting a slight asymmetry around the secondary minima and a small difference in the height of the successive maxima. The light-curve analysis was performed using a Roche model of a binary containing a geometrically and optically thick accretion disk around the more massive primary star. By solving the inverse problem, the orbital elements and the physical parameters of the system components and of the accretion disk were estimated for all the individual UBVR light curves. The model gives a consistent solution for the RY Sct binary system and supports the hypothesis of the existence of an optically thick disk around the massive component. Our results suggest a mass exchange between the components and a mass loss from the system. This could be considered as a possible mechanism of the formation of the accretion disk around the more massive component and of the circumbinary envelope of toroidal form in the orbital plane of the system.

No abstract