Omer Lutfi Degirmenci

New light curve analysis and period changes of the overcontact binary XY Leonis

Light curves and photometric solutions of the contact binary XY Leo are presented. The UB VRlight curves appear to be almost symmetric. The B and V light curves were analysed with the Wilson-Devinney code and the orbital parameters of the system were obtained and compared with those obtained in previous studies. All the times of minimum light were collected and combined with the new ones obtained in this study. The orbital period of the system oscillates with a period of 19:6 years and a semi-amplitude of 0:023 day. This regular change was analysed under the assumption of the third body hypothesis. The time delay and advance due to the orbit of the eclipsing pair around the third component were computed and subtracted from the original residuals obtained with the linear light elements. The remaining residuals also show a parabolic change. Therefore, we assumed that the orbital period of the system changes with time due to at least two dierent causes. The parabolic change of the period may be attributed to either mass transfer from less massive component to the more massive one, or an additional component bounded to the double binary system with a longer period.

Absolute Properties of the Binary System BB Pegasi

We present ground-based photometry of the low-temperature contact binary BB Peg. We collected all the times of mid-eclipse available in the literature and combined them with those obtained in this study. Analyses of the data indicate a period increase of × 10-8 days yr-1. This period increase of BB Peg can be interpreted in terms of the mass transfer 2.4 × 10-8 M⊙ yr-1 from the less massive to the more massive component. The physical parameters have been determined as Mc = 1.42 M⊙, Mh = 0.53 M⊙, Rc = 1.29 R⊙, Rh = 0.83 R⊙, Lc = 1.86 L⊙, and Lh = 0.94 L⊙ through simultaneous solutions of light and of the radial velocity curves. The orbital parameters of the third body, which orbits the contact system in an eccentric orbit, were obtained from the period variation analysis. The system is compared to the similar binaries in the Hertzsprung-Russell and mass-radius diagrams.

Photometry and Analysis of the Eclipsing Binary IQ Persei

Photoelectric observations of the eclipsing binary IQ Persei have been carried out in B and V colours at Ege University Observatory. The corresponding light curves were analyzed by synthesis techniques. The absolute physical parameters and apsidal motion period (122 yr) of the system were obtained. The results have been compared with theoretical evolutionary models which include both mass loss and convective overshooting. Theoretical evolutionary tracks of the component stars indicate an age of 1.3 × 108 years and an apsidal motion constant of 0.0040 which is greater than its observed value by only about 5%. The A7 secondary of the eclipsing pair is still close to the zero-age main sequence but B7 primary is about halfway through its main sequence life-time.