Two observational campaigns were carried out during the eclipses of EE Cep in 2003 and 2008/9 to verify whether the eclipsing body in the system is indeed a dark disk and to understand the observed changes in the depth and durations of the eclipses.
Multicolour photometric data and spectroscopic observations at both low and high resolution were collected. We numerically modelled the variations in brightness and colour during the eclipses. We tested models with different disk structure. We considered the possibility of disk precession. The complete set of observational data collected during the last three eclipses are made available to the astronomical community. Two blue maxima in the colour indices were detected during these two eclipses, one before and one after the photometric minimum. The first (stronger) blue maximum is simultaneous with a bump that is very clear in all the UBVRI light curves. Variations in the spectral line profiles seem to be recurrent during each cycle. NaI lines always show at least three absorption components during the eclipse minimum and strong absorption is superimposed on the H_alpha emission. These observations confirm that the eclipsing object in EE Cep system is indeed a dark, dusty disk around a low luminosity object. The primary appears to be a rapidly rotating Be star that is strongly darkened at the equator and brightened at the poles. Some of the conclusions of this work require verification in future studies: (i) a complex, possibly multi-ring structure of the disk in EE Cep; (ii) our explanation of the bump observed during the last two eclipses in terms of the different times of obscuration of the hot polar regions of the Be star by the disk; and (iii) our suggested period of the disk precession (~11-12 P_orb) and predicted depth of about 2 mag the forthcoming eclipse in 2014.
The sudden lengthening of orbital period of VV Cep eclipsing binary by about 1% was observed in the last epoch. The mass transfer and/or mass loss are most possible explanations of this event. The photometric behaviour of AZ Cas, the cousin of VV Cep
, suggests that the accretion can occur and could be important in this system, too.
We present our multicolour photometric data of the primary and secondary eclipses of OW Gem that took place in 1995, 2002, and 2006, as well as the new radial-velocity data collected since 1993 by R. F. Griffin and A. Duquennoy. The Wilson-Devinney c
ode was used for the simultaneous solution of both photometric and spectroscopic data. A complete set of orbital and physical parameters of the components was obtained. The pair of values, eccentricity e=0.5286 and argument of periastron omega=140.73 degree, give better compatibility of the moment of the secondary minimum with the observations compared to previous estimates.
