During two observational seasons of international campaign of YY Her we secured photometric data which covered the primary as well as the secondary minima and revealed unexpected outburst activity of this system.

SZ Lyncis (=HD 67390) is a high amplitude Delta Scuti star, discovered by Hoffmeister in 1949. Van Genderen (1967) noticed that the residuals in the O-C diagrams followed a sinusoidal variation with a period of Porb = 3.091 years. Several years later, Barnes & Moffett (1975) improved this period to Porb = 3.138 years and suggested that the sinusoidal variations in the O-C diagrams, observed by van Genderen (1967), originate from the light travel time effect, since SZ Lyn is a member of a binary system. This hypothesis was confirmed by Bardin & Imbert (1984) with measurements of radial velocities. Soliman et al. (1986) found the pulsation period to be 0.120534896 days and the orbital period 1173.5 days.

New BVRI CCD observations of the pulsating star SZ Lyn are presented. The light curves are analyzed using Fourier transform techniques and a new period is determined. A new ephemeris, based on recent times of maxima, is proposed. The photometric data collected over the last 40 years are used to determine the pulsational and orbital elements, since SZ Lyncis is a member of a binary system. The results are compared with those found in previous studies.

Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for the eighth set of 10 close binary systems: AB And, V402 Aur, V445 Cep, V2082 Cyg, BX Dra, V918 Her, V502 Oph, V1363 Ori, KP Peg, and V335 Peg. Half of the systems (V445 Cep, V2082 Cyg, V918 Her, V1363 Ori, and V335 Peg) were discovered photometrically by the Hipparcos mission, and all systems are double-lined (SB2) contact binaries. The broadening function method permitted improvement of the orbital elements for AB And and V502 Oph. The other systems have been observed for radial velocity variations for the first time; in this group are five bright (V<7.5) binaries: V445 Cep, V2082 Cyg, V918 Her, KP Peg, and V335 Peg. Several of the studied systems are prime candidates for combined light and radial velocity synthesis solutions. Based on the data obtained at the David Dunlap Observatory, University of Toronto.

The first l VRI CCD photometric observations of the eclipsing binary system OT Cep are presented. The new times of minima, combined with the existing ones, are used to determine a new ephemeris of the system. Our light curves are analyzed with light curve synthesis techniques to derive the first geometric and photometric elements of OT Cep. The possible evolutionary status of the system is also discussed.

New l BVRI CCD observations of the eclipsing binary NSV 223 are described, and a new ephemeris is proposed. The light curves are analyzed using the Wilson-Devinney light curve synthesis code, and the new geometric and photometric elements are derived. These elements, combined with the available spectroscopic data, yield the absolute system parameters, which make it possible to construct a model of the system.

This paper reports new photometric observations of minima of two very long-period eclipsing systems: AZ Cas (P=3402 °}) and EE Cep (P=2050 °). In order to match the observed depth of the primary minimum of AZ Cas we had to introduce a third light component. For EE Cep, the shape of the eclipse can be explained by a model that includes a dark precessing disk in the system.

The paper presents combined spectroscopic and photometric orbital solutions for five close binary systems: V 402Aur, SX Crv, V829 Her, VZ Lib and V753 Mon. The photometric data consist of new complete, multicolor light curves, while the spectroscopy has been recently obtained within the radial velocity program at the David Dunlap Observatory. For one target, SX Crv, new spectroscopic data were obtained using the 6.5 m Magellan telescope. A contact configuration was found through light curve modeling for all targets except V753 Mon. Our solution for V753 Mon resulted in a semidetached configuration with the slightly less massive component filling its Roche lobe.