MWC 656 has been reported as classical Be star with a black hole companion. Revisited spectral variability properties render this unlikely, with a hot subdwarf more probable.

The advantage of analysis of observed data using their fit with theoretical model of the directly observed quantities is shown as well as the need for simultaneous solution of all available data. Some particular problems of disentangling of stellar spectra and model atmospheres of component stars of multiple systems are discussed.

Spectroscopy and photometry of eclipsing binaries and Cepheids (using the Baade–Wesselink method) yield primary distance markers applicable to the Local Group of galaxies. The technique of disentangling spectra has proved helpful in resolving stellar physical parameters. Our method also allows us to disentangle interstellar absorption lines and, thus, to complement the radial-velocity structure of the interstellar medium with an (otherwise unattainable) upper limit to its distance. The mapping of the spatial and kinematic structure of the stellar and interstellar components of the Magellanic Clouds and Stream enables constraining their tidal evolution and, thus, of the mass of the Galaxy.

The techniques of disentangling were originally developed to separate spectra of individual components from time series of spectra of binaries and, simultaneously, to determine either the corresponding radial velocities or directly to solve for orbital parameters.

Generalizations of the disentangling method enable us to include also intrinsic line-profile variability of the component spectra into the underlying model, and thus to solve for additional physical parameters of the stars (either single or components of multiple systems). Depending on the problem in question, it may also be helpful to constrain the space of separated spectra by templates or to bound the solution in the parameter space by photometry, interferometry or other observational data.

The single-lined 51.420d spectroscopic binary $\alpha$ Dra (HD 123299, Thuban, spectral type A0 III) is a slightly metal poor star. First orbital elements were obtained by Harper in 1907. Mizar A (HD 116656, spectral type A2 V) is a double-lined 20.53 d spectroscopic binary first reported by Pickering in 1890. Its orbital elements were determined by Vogel in 1901. The redetermination of the orbital elements for these two binaries used the spectrum disentangling computer code KOREL (Hadrava 1995, 1997). We present revised orbital elements based on new electronic spectra taken at the Ondřejov Observatory between 1994 and 2003.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

66 Oph is a multiple system with a close binary orbiting the B2Ve primary Be star. The binary parameters were derived by two independent methods and spectra of components BA and BB were separated by Fourier disentangling.

Available spectroscopic evidence of various circumstellar gaseous structures in the well-known binary β Lyr is confronted with the results of 3-D gas-dynamical simulations of mass transfer between the binary components, obtained for the currently best available basic physical properties of the system. It appears that the gas-dynamical model is capable to explain, at least qualitatively, the formation of all basic observed components of the circumstellar matter, including the jet-like structures, recently found from interferometry and polarimetry of the object.

Emission-line profiles from both narrow eccentric rings and an extended disk around a black hole are presented. In both cases, a black-hole signature appears when the inclination of the emitting orbit is larger than 80°.

Since their discovery (by Father Secchi in 1866) until the end of sixties, Be stars were not a subject of any systematic studies of their possible light and colour variations. Already at that time, the astronomical literature contained ample evidence showing that a number of Be stars were light variables. However, almost all such findings resulted as by-products of studies of different or wider groups of objects. Feinstein (1968) was probably the first who pointed out explicitly that many Be stars are light variables. A pioneering study which was aimed at the detection of light variations of a large group of Be stars by means of differential photoelectric photometry was carried out by Haupt & Schroll (1974).

Although KX And (HD 218393, MWC 397) has been observed since the beginning of our century, we have no reliable model of this peculiar emission-line object. Published papers (e.g. Plavec et al. 1982; Kriz and Harmanec 1975 and references therein) indicate that it is a B+K W Ser-type binary with a period of 38.9 days. This paper presents a summary of intensive observations carried out during the last fifteen years.

The observational material used consists of 65 coude spectra obtained with the Ondrejov 2-m telescope, UBV photometry obtained at Hvar Observatory and 28 archival IUE images. The radial-velocity and photometric data are combined with those found in the literature. A PDM period search over the interval 1 to 1000 days unambiguously indicates the 38.9-day period both in RV and photometric data.

Basic information about the star o and (HR 8762, HD 217675-6) is a bright (V=3.55m, B-V=-0.11m U-B=-0.50m) B6 III-Ve star. Its emission-line and shell spectrum is known to come and go on a time scale of years. In fact, the presence of a strong shell spectrum misled the authors of the HD catalogue to assign the star two HD numbers.

o and is a prototype of Be rapid light variables in the sense that it has the longest record of photoelectric monitoring which goes back to 1915! The long history of attempts to understand the variations of this star has recently been summarized by Harmanec (1983). Collecting and analyzing all historical photoelectric observations, Harmanec (1984) concluded that the light variations of o And can be understood as a superposition of a long-term cyclic (8.5y) variation with an amplitude over 0.1m (the star being faintest at the recorded shell maxima) and a rapid periodic variation with a period of 1.571272 days.

The calculation of a gas stream offers two modes of the stream. In any case the stream cannot be detected optically. The calculated line profiles caused by the disc are demonstrated.