A. Y. Ertan

Two-colour photoelectric investigation of AR Lacertae

The RS CVn-type eclipsing binary AR Lac has been observed in two colours,B andV, in 1978 and 1979. Several times of minima have been obtained during the observations and the new light elements have been calculated. The orbital period of the system was found to be decreasing with an amount of 14.6 s century−1.The light curves of the system obtained inB andV show a significant wave-like distortion outside eclipses. The amplitudes of the wave-like distortion inB andV are about 0.m09 and 0.m10 in 1978, and, 0.m12 and 0.m13 in 1979, respectively. The minima of the wave-like distortion have shifted with an amount of 0.p40 in one year, thus indicating the migration period of the wave-like distortion is about 2.5 yr.A noticeable variation of light during the totality of primary minimum has also been observed. This variation can be attributed to the distortion wave which has been moving towards decreasing phases.

Photoelectric photometry of Z herculis

Two-colour light curves of Z Her were obtained observing the system from 1978 to 1981. The wave-like distortion at outside eclipses were derived. The amplitudes of the wave increase and its minimum migrates towards the decreasing orbital phase with a period of about 1.4 yr. An attempt was made to represent the wave-like distortions with a truncated Fourier series. The representation was found to be unsatisfactory since the distribution of the present observations is not regular but forms separate groups along the time axis. Therefore, further observations to cover the phases evenly in between the minima are needed.

Extensive photometric study of RT lacertae

In this paper we present the observations of the peculiar eclipsing binary RT Lac, which were obtained in 1980 and 1981. Examining the light curves obtained in successive four years we estimate the period of the migrating light curve distortion to be about four years. The orbital period of the system was also found to be decreasing with an amount 34s century−1. The brightnesses both at primary and secondary are changing with the time, which is clearly seen from the last light curves. The variations occurred at primary is three times greater than secondary eclipse. Therefore, we suggest that the star, in front at primary eclipse, is more responsible for the distorted light curves and it should be the earlier spectral type and also the smaller one.

Light curve variations of RT lacertae

The eclipsing variable RT Lac, which is classified as an RS CVn-type binary by Hall, was observed in two colours,B andV, during the summer seasons of 1978 and 1979. The observations made during two successive seasons indicate that, outside eclipses, the system has brightened by about 0.12 and 0.15 magnitudes on average inB andV, respectively. Moreover, RT Lac was even fainter when observed by Milone in 1965. While the total brightness of the system remained unchanged at mid-secondary, it increased at mid-primary and outside eclipses. This may be interpreted as indicating that the cooler component is responsible for the peculiar light variations.

Analysis of the light curves of the eclipsing system V548 Cygni

The eclipsing binary V548 Cygni was observed photoelectrically in yellow and blue light at Ege University Observatory in 1975. A total of 857 observations were obtained of each colour. Three times of minima were obtained and new light elements were derived. The orbital analysis were made by the methods of Kitamura and Wood. The system has a third body whose total luminosity is greater than that of secondary companion.

The light curve variations in AR Lacertae

The eclípsing binary AR Lac has been observed in two colours,B andV, in 1980 and 1981. The new times of minimal obtained during the observatons indicate that the period of the system is still continuing its decrease. The wave-like distortions outside eclipses have two maxima and are very similar in shape in successive two years.

Light variation of LX persei between eclipses

Two-colour photoelectric observations of LX Per carried out at Ege University Observatory in 1981 and 1982 observing seasons are presented. The light curve of the system has a wave-like distortion which migrates towards the decreasing orbital phase. The period of the retrograde migration of the wave-like distortion has been determined as 475 days. The amplitude of the wave appears to change with time periodically.

Photoelectric light curves of RT coronae borealis and their analysis

The first photoelectric light curves of the RS CVn-type eclipsing binary RT CrB are presented. There is no indication about the existence of wave like distortion on its light curve. The light curves were analyzed by using Woods and Nelson, Davis, and Etzels methods. The radii of the components are nearly identical. The solutions indicate that the cooler component has a later spectral type between K0 and K2.

Photoelectric photometry of AR Lac In 1982

In this paper we present the observations of AR Lac, which were obtained in 1982. The variations in the light curves, occurred in the time interval as short as two months, indicated that the system was very active in 1982 like in 1979. The times of the minima obtained in this study indicate that the orbital period of the system continues to decrease. The decrease in the period was recalculated using all the times of minima obtained photoelectrically between 1961 and 1982 and found to be 17.0±1.4 s century−1.