[en] Symbiotic stars are considered which best of all are described by the binary star model. An analysis of properties of symbiotic stars shows that their hot components should be either carbon-oxygen dwarfs with thin hydrogen-helium envelopes or helium stars with thin mantles. Cold components are red giants losing matter with the rate of 10^-5-10^-6 M/yr over the period of 10⁵-10⁶ years (M is the Sun mass). Such systems can be formed of wide pairs as a result of loss of envelope of an initially more massive star of the system by way of continuous outflow of matter or expulsion due to dynamic instability at the stage of red giant, and also of more close pairs as a result of exchange of matter between the components. It has been shown that hot components of symbiotic stars can accrete 10^-6-10^-9 M/yr and some consequencies of accretion on a C-O dwarf have been considered

[en] Recent data on duplicity and multiplicity for normal main sequence stars and a variety of classes of stars that have abnormal frequencies are discussed and compared. The occurrence of multiplicity among normal stars is assessed and those classes of stars in which different multiplicities have caused their spectroscopic or evolutionary peculiarities are identified. It is shown that the correlations between high or low duplicity and the consequent peculiarities are produced by a variety of dynamical and astrophysical mechanisms. 128 references

[en] A study of the joint evolution of the normal- and neutron-star components of massive binaries opens with a classification scheme and the analytic expressions to be applied in Paper II for computer simulation of the observable properties of such systems

[en] In spite of all observational as well as theoretical efforts no clear picture of the object V1329 Cyg seems to emerge. The only certain fact is that there was an outburst in the year 1966 followed by an ejection of matter. The interpretation of the rest of the data depends critically on the assumption about the binary or single-star nature of the object. The author recapitulates photometric and spectroscopic observations and describes post-delivery studies. He then outlines his binary hypothesis and mentions alternative models proposed by other authors. (Auth./C.F.)

[en] If the companion of a Roche-lobe-filling red supergiant is itself a binary (of short period), the process of accretion onto the companion is likely to be different from the usual situation where the gainer is single. We suggest that the evolution of a triple system like HD 157978/9--(A V + A V, 3/sup d/.86)+G III, 1170/sup d/--may lead it to a state where it could resemble quite closely the enigmtic eclipsing system epsilon Aur (.+FO Iap, 9890/sup d/)

[en] The aim of the Symposium was to make a cross-check of the numerous recent results in ground-based and space observations of galactic and extragalactic stars using evolutionary models. A number of reviews and papers give the present status of these comparisons, whose astrophysical purpose is twofold: firstly, to understand as precisely as possible how stars evolve and die, and secondly, to apply the predictions of stellar evolution theory as a useful tool in a variety of astrophysical fields like chemical evolution of galaxies and cosmology. In addition to the study of various interesting stellar groups like horizontal branch stars, red giants on the asymptotic branch, nuclei of planetary nebulae, massive stars, etc., the book also presents an assessment of the current problems of binarity, pulsation, rotation and mixing in connection with evolution. All this information makes this volume essential in the field of stellar evolution and its relationship with other fields. (orig.)

[en] The paper considers the evolution of the triple system 4 Dra, which now comprises a cataclysmic variable in a P of about 1700d orbit with an M giant. It is found that the requirement of dynamical stability imposes significant restrictions on the precursor system of the CV. 16 refs

[en] Theoretical space densities and frequency distributions of the initial masses of red giants in different evolutionary phases are compared with the available information concerning numbers and absolute and relative masses of different types of peculiar red giants of types Ba, R, S, N (P giants) in order to constrain possible scenarios for mixing. The theoretical results are obtained by combining the semiempirical initial mass function of stars and published stellar lifetimes, and incorporating semiempirical prescriptions for mass loss. The observational data on masses consist of variability types, space distribution, kinematics, and presence in binaries and clusters. The space density of Ba stars is found to be too large to be accounted for by double-shell models, reinforcing the conclusion that most Ba stars have nothing to do with helium-shell flashes. Identification with the helium-core flash requires a few percent of stars which flash to be converted to Ba stars. The space densities of the cooler P giants are poorly known, but do not exceed the expected number of stars in the doule-shell phase. Data on P giants in binary systems and clusters show a large range in initial masses, from 1 M/sub sun/ to > or approx. =10 M/sub sun/, at least for the S, N, and possibly Ba stars. Kinematical data indicate a mean mass of around 1--1.5 M/sub sun/ for all types of P giants, with the lower end applying to the R stars, N- and S-type Miras, and strong Ba stars, and the upper end applying to the weak Ba stars, N and S non-Miras, and SC stars. Information on spatial distributions and variability type is also discussed

[en] The study of the context of different kinds of massive stars (apples and tomatoes) can provide insights on their evolutionary status. Useful constraints on the models can be obtained provided that visual and bolometric magnitudes of the different components are carefully determined. Here, evidence is reviewed that massive stars spend their short lives in tight clusters. Reddening determinations and bolometric corrections for these stars are briefly examined. 15 refs

[en] Evidence is accumulating in favour of a heretofore missing link in the evolution of massive binary stars - a second WR phase in which the companion to the WR star is a neutron star of mass 1-2 solar masses, or in some cases a more massive black hole. The discovery of such objects is also important in assessing the role of duplicity in the formation of WR stars. (Auth.)