Although the majority of the known eclipsing binaries are in systems which consist of only the two eclipsing components, a significant number of them do occur as components of triple star systems or higher order multiple star systems. In this context this term is restricted to those systems whose components are in closed orbits. A recent survey of visual binaries with variable components is that by Proust et al. (1981), which details about 300 systems. Walker (1979) has also prepared a list of variables as components of double star systems, and this includes numerous systems not included in other lists.

AN Tau has been classified as the β Lyrae-type variable. The only visual light curve was published 55 years ago. The star was observed photoelectrically during a few last years at Mt. Suhora and Skalnaté Pleso Observatories. The complete light curve was obtained in B and V band passes. The preliminary physical parameters of the system were obtained using the Wilson-Devinney code. From the period study of AN Tau we derived new period of the system being 1d.6143843, which differs by 0d.00026 from the value obtained earlier. The orbital period of AN Tau seems to be constant.

RY Scuti, the 11-day [Fe III] eclipsing binary, has been reinvestigated on the basis of spectroscopic material secured at the European Southern Observatory (ESO), La Silla, Chile, and at the Cerro Tololo Interamerican Observatory (CTIO), Chile, that cover the regions 3400–5150 Å and 5700–6700 Å, and worked out with the measuring and computing facilities at the ESO Headquarters, Garching bei München, Germany. Ultraviolet observations taken with the IUE satellite were also analyzed.

Spectroscopic observations are presented showing evidence of mass transfer activity in Algol-type eclipsing binaries. Traditional Hα emission line spectroscopy is discussed along with absorption line spectroscopy of the O I 7774 A multiplet. Eclipse effects in both lines are discussed, along with a new non-LTE model for Hydrogen line spectrum synthesis.

A method for estimating representative values of the parameters that characterize the loss of mass and angular momentum occurred during the evolution of a close binary star is considered. Absolute dimensions previous to mass-transfer stage have been obtained for a select group of 43 semidetached systems adopting a grid of values of mass loss, angular momentum loss and initial mass ratio. Our study reveals a highly non-conservative scenario for the evolution towards an Algol-type system.

HD 207739 = V1914 Cyg, a tidally distorted F8 supergiant plus an obscured hot non-degenerate star, is presently in a state of episodic mass dumping onto an accretion shell around the hot component. Unrelated to the 141 day orbital cycle, the obscuration has a 50 day periodicity during which most of the UV flux diminishes rapidly, then gradually brightens. The more evolved yet less massive F supergiant is thus presumably shedding mass due to its pulsation.

The energy distribution of HR 2142 is studied in order to test the hypothesis that this star is an interacting binary with a cool Roche–lobe filling companion. We find that, for any reasonable choice of T eff, the companion should have been detected in the red part of the spectrum. We propose instead that the Be star is the outcome of a case B mass-transfer, which has pun it up. It is now surrounded by a mass-loss disc, rather than an accretion disc and is accompanied by either a helium star (resembling the Φ Per system) or by a white dwarf. If the binary was born spinning rapidly, alternatively the companion may be a solar-type, unevolved main sequence star. In case of a Helium star companion, there may be Helium lines visible (like in Φ Per), or the helium star may be detectable in the XUV, e.g. by the ROSAT XUV instrument. A white dwarf companion may be accreting material from the disc around the Be star and may show low luminosity X-ray emission. This emission may have been seen in the ROSAT PSPC X-Ray Survey.

Preliminary results of an extended multi-wavelength study of bright B- and Be-type stars are presented. This project aims at finding evidence for the existence of white-dwarf companions to Be stars which are predicted as the result of close binary evolution. Comparison of ROSAT all-sky survey data with simultaneous measurements of Hα profiles and infrared photometry suggests that there is no difference in the X-ray behaviour of Be stars with respect to that of normal B stars. The ROSAT X-ray luminosities of B and Be stars range from 10−8 to 10−5 times the bolometric luminosity.

Ultraviolet observations for nine massive Algol systems (DH Her, TU Mon, AU Mon, Z Ori, RY Per, IZ Per, V356 Sgr, RZ Sct and ET Tau) obtained during their primary eclipses with the IUE spacecraft are discussed. Four systems, AU Mon, Z Ori, IZ Per, and RZ Sct, yielded no useful data on the presence of UV emission lines. Four binary systems DH Her, TU Mon, RY Per, and V356 Sgr, displayed a prominent emission spectrum with the notable exception of carbon lines; only one of the studied systems, ET Tau, showed carbon emission. Analysis of these data strongly supports the suggestion that the lack of carbon emission lines in these systems is the product of an inherent carbon deficiency in the transferred material and not due to any ionization effects in the gas. This carbon deficiency is the result of the CNO processed layers of the secondary being exposed as a result of mass transfer. The IUE data on TU Mon also indicates that this system undergoes a total, rather than partial, eclipse.

The surface carbon abundances of Algol secondaries are known to be low compared to field stars of similar type. The C and N anomalies of these G and K subgiants are undoubtedly due to the exposure of CN cycle processed material as mass transfer removes the outer layers of the star. Therefore the carbon abundance is a promising tool for helping fix the evolutionary state of Algols, particularly the amount of mass which has been lost from the secondary. We report here the carbon abundance of 12 Algol secondaries as deduced from the g-band in spectra obtained during photometric totality. We compare the abundances to those from models of single stars of appropriate age and mass. The values of log ∊(C) for this sample fall 0.25–0.75 dex below field G and K giants, and 1.25–1.75 dex above “stripped” single star models. This larger sample supports the conclusions of Parthasarthy et al. regarding mixing and mass loss, which they deduced from a smaller sample of carbon abundances.

We describe some of the observational phenomena associated with colliding stellar winds, focussing especially on close WR+O binaries. In particular, we report some new ultraviolet observations of CQ Cep and V444 Cyg. We also discuss some of the general theory of such wind collisions.

Stars in close binary systems can suffer two kinds of mass change: 1) mass transfer between the stars 2) mass loss completely from the system. Observational estimates indicate that these are of the same order. A simple explanation can be found if the mass loss, by stellar wind, from the Roche-filling star is the driving mechanism behind mass transfer. We find quantitative estimates for the necessary conditions and find that the mass transfer rate and the mass loss rate are indeed similar. We find that the radii of evolved semi-detached systems are more consistent with wind-driven evolution than the traditional nuclear-driven Roche-lobe overflow.

Current light synthesis models of SV Centauri require a highly overcontact system with an 8000K temperature discontinuity between components. Current evolutionary models support the overcontact status, and describe the system as in the final stage of rapid mass transfer prior to mass reversal, calculated to occur within 2500 years. Light synthesis simulation provides a poor fit to the observations, and requires an ad hoc assumption to fit the substantial O'Connell effect.

IUE spectra have been reported to indicate the presence of a 200 000K source of small dimensions in the system. New spectrum synthesis results demonstrate there is no hot spot, but there is extra radiation longwards of 200nm that is unaccounted for by the overcontact model.

Postulated presence of an accretion disk around the mass gainer prospectively overcomes the observational anomalies. Formation of the accretion disk apparently violates the Lubow-Shu criterion. A reasonable scenario nonetheless supports accretion disk formation. Conflict with the theoretical models can be resolved on the postulate that the spherical accretion assumed in those models render them inapplicable to this system.

Five members of the class of near-contact binaries have been investigated in the ultraviolet using the IUE. The spectra have been analyzed to find masses of two of the systems and to indicate the possibility of mass transfer.

The first infrared photometry for the W-UMa system SS Ari is presented. An analysis based on medium resolution spectroscopy presented here shows that SS Ari is a W-type system with a mass ratio of 0.33. It seems certain that the asymmetry in the published light curves and those obtained for this study can be explained by the effect of spots on one or possibly both components of the system. The precise location, size and temperature of these spots require the use of Doppler Imaging techniques in conjunction with high quality multi-band photometry.

Four times of minimum lights from six nights photoelectric observations of YY Eri during the observing seasons from 1983 to 1984 are derived. With these and previously published photoelectric minima, new light elements are determined. A detailed numerical investigation of times of minima shows that the orbital period has changed sinusoidally with a period of about 24 years. These changes of period are investigated in terms of two plausible causes : a light-time effect due to an unseen third body and asymmetries of light curves due to stellar activities of one component or both.

We present light curve analyses of contact binaries and comparisons with previously published cross-correlations radial velocity data. The critical parameter q (mass-ratio) obtained from a grid technique is confronted with the spectroscopic value. For total eclipsing systems, both values are always in a good or reasonable agreement, including some stars with shallow light curves. For partial eclipsing systems, convergent photometric and spectroscopic results are obtained for an important set of stars. Two exceptions are V523 Cas and XY Boo for which some arguments are suggested. We concluded that reliable parameter determinations can be obtained from pure photometric solutions, by means of grid techniques.