Photoelectric elements of the eclipsing binary XY Cep

The light curve andU, B andV observations of the system XY Cep have been presented. Photoelectric and absolute elements of the system have been determined. It is a semi-detached system.     

Photometric observations and light curve analysis of ST Aquarii

The system of ST Aquarii has been observed inB andV filters at KOTTAMIA Observatory in Egypt. Two light curves have been obtained and new times of minima have been calculated.The light curves have been analysed using the theory of Fourier transform of light changes in frequencydomain, and new geometrical and physical elements have been obtained.     

Photometric study of VZ hydrae

The photoelectric elements of the system VZ Hydrae have been redetermined inU, B andV colours. Our results are at variance from those given earlier by Walker. The colour of the system has also been given. The system is a detached one.     

Photoelectric elements of CD Tau

Photoelectric and absolute elements of the system CD Tau have been determined inU, B andV filters. The system is a detached one.     

Determining the orientation parameters of the ICRS/UCAC2 system using the Kharkov catalog of absolute stellar proper motions

The absolute proper motions of about 275 million stars from the Kharkov XPM catalog have been obtained by comparing their positions in the 2MASS and USNO-A2.0 catalogs with an epoch difference of about 45 yr for northern-hemisphere stars and about 17 yr for southern-hemisphere stars. The zero point of the system of absolute proper motions has been determined using 1.45 million galaxies. The equatorial components of the residual rotation vector of the ICRS/UCAC2 coordinate system relative to the system of extragalactic sources have been determined by comparing the XPM and UCAC2 stellar proper motions: ω _x,y,z = (−0.06, 0.17, −0.84) ± (0.15, 0.14, 0.14) mas yr⁻¹. These parameters have been calculated using about 1 million faintest UCAC2 stars with magnitudes R _UCAC2 > 16 ^m and J > 14 ^m . 7, for which the color and magnitude equation effects are negligible.     

Light variation of the variable star OO Aquilae

PhotoelectricB andV observations of the W UMa-type system OO Aql have been obtained for 11 nights during the period from 22 June–30 July, 1987. A total of 978 observations were obtained in eachB andV filter. All these observations were transformed to theB andV colours of theUBV standard system. Five light curves for primary and secondary eclipses were obtained, its times of minima were determined and a new linear ephemeris was given. The period changes of the system were discussed.     

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 _. ^m 09 and 0 _. ^m 10 in 1978, and, 0 _. ^m 12 and 0 _. ^m 13 in 1979, respectively. The minima of the wave-like distortion have shifted with an amount of 0 _. ^p 40 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.     

The Photometric Observations and the Light Curve Analysis of U Pegasi

The system of U Pegasi was observed photometrically in B and V filtersin 1998 at Birouni Observatory, University of Shiraz, Iran. Two Lightcurves were obtained and have been analyzed separately of Wilson-Devinneycode. New geometrical and physical elements for the system are given. Theabsolute dimensions of the binary have been derived by combining thephotometric solution with spectroscopic data of the system. The lightcurves analysis indicate that U peg is an overcontact W UMa system with Wtype components which fill their corresponding Roche lobe. The resultsobtained in this study indicate that U Peg may be lied on main sequencewith estimated masses of 0.565 M and 0.362 M .     

Photoelectric study of the eclipsing system CD Eridani

Limiting photometric solutions for the system CD Eri inB andV filters have been obtained. The secondary minimum was found to be absent.     

UBV photometry of RT Persei

Photoelectric and absolute elements of the system RT Per have been determined inU, B, andV filters. It is suggested that the primary star may be surrounded by a gaseous disk.     

Photometry of an active Algol-type binary HP Aur

The short period Algol-type binary HP Aur has been studied on the basis ofUBV photometric observations. Its colour indexes were found to be (U-B)=0.14, (B-V)=0.70, and light curves show non-symmetrical and obvious photometric disturbances. Autoregressive spectral analysis and harmonic analysis for its light variations were made. The results indicate its brightness variations have the multiplet quasi-periods and low amplitudes. Its photometric solutions have been obtained using the Wilson-Devinney method. Its mass ratio is 0.5631, orbital inclination is 85.0 and it is a detached system. Its basic model has been discussed briefly.     

The very short period W UMa system V 1022 Ophiuchi

Photoelectric light curves of V1022 Oph inB andV are presented. It has been confirmed that it is a W UMa type eclipsing binary with one of the shortest periods known (P<0.^d25). Some general properties of the system have been derived.Based on observations made at the European Southern Observatory (La Silla/Chile)     

Photometry and analysis of the eclipsing variable GO Cygni

Photoelectric observations of the eclipsing binary GO Cyg have been carried out inB andV colours at the Ege University Observatory. The corresponding light curves were analyzed by the method of Wilson-Devinney. The system was found to be a reverse Algol semi-detached binary. The absolute elements of the system are also deduced.     

Spectrum variability of 25 Sextantis

Vibrational transition probabilities: namely, Franck-Condon factors andr-centroids, have been evaluated using an approximate analytical method for theB-A system of MgO. Morse potential energy curves forB ¹⁺ andA ¹ states of MgO have been constructed by use of the latest spectroscopic data. The value ofr-centroids for the band have been found to decrease linearly with the corresponding wavelength. We show results for six new bands in the umbral spectrum of the Sun.     

Photometric elements of the eclipsing binary DN UMa=HR 4560

A total of 704 previously published photoelectricB colour observations of the multiple system HR 4560 are analyzed by means of the light curve models NDE (Popper and Etzel, 1981) and WINK (Wood, 1972) in an iterative procedure. As a result, we have found that componentC of the multiplpe system ADS 8347 is the most probable origin of the observed eclipses. Some relevant astrophysical parameters of the component stars which indicate a normal Main-Sequence binary star have also been estimated.     

Period study of GH Pegasi

The period study of the eclipsing binary system GH Pegasi has been presented for the first time. A new period (P=2^d.556135) of GH Peg, based on all available times of minima, has been given. O–C diagrams of the system have also been presented for the first time, and the period changes present in the system have been analysed. The period shows changes around the year 1972 and 1981. The total period change in different portions of the O–C diagram, based on the corrected period, ranges from 5.2×10^–6 d to 7.0×10^–5 d. The photoelectric minima show sufficiently large scatter in the system.     

Two-colour photoelectric investigation of SZ Pisces

The RS CVn-type eclipsing binary SZ Psc was observed in two coloursB andV, in 1981. The rate of change of the period was calculated using two different least-squares procedures. The amplitudes of the light variations at outside eclipses are 0 _. ^m 181 and 0 _. ^m 213 inB andV colours, respectively. The light curves of the system have been solved using a new approximation. The radius of the cooler component is only 82% of its Roche-radius and the system is detached one.     

Spectral-luminosity classification,colour variations and suspected beta canis Majoris-type variability in IZ Persei

The colour indices and the spectrum-luminosity classification of the eclipsing binary system IZ Persei have been presented for the first time. The colour indices of the system appear reddened. Applying the interstellar reddening corrections, the spectral-luminosity classes of the primary and the secondary components of IZ Per come out to be B2.5III-V and B5III-V, respectively. The averageB-V andU-B colour excesses come out to be 0 ^m .4 and 0 ^m .2, respectively. The colour indices show continuous variation throughout the cycle, and indicate the presence of intrinsic variability. Tentative analysis suggests that the primary component of IZ Per is a Beta Canis Majoris-type variable. The possibility of a shell has also been discussed.     

Ubv(Ri)C Photometry of the Contact W Uma Binary Bd + 14∘5016

New UBV(RI)_C observations and radial velocities of the W UMa-type system BD + 14^∘5016 were collected. Changes of the properties of a hot spot, located on the surface of the primary component, have been noticed.     

BV observations of the eclipsing binary WX Eridani

Photoelectric observations of WX Eridani inB andV filters have been discussed. The maximum magnitudes of the system areB=9 ^m .70 andV=9 ^m .46. TheB-V colours of the components are 0 ^m .16 and 0 ^m .80 for the primary and the secondary, respectively, while their spectral types are A5+K0. The period has been found to be constant and its revised value is 0^d.823 270 76.