Detached binary system MQ centauri and its relation with Crux OB1 association

In this thesis, the astrophysical characteristics of eclipsing binary system MQ Cen which is located in the direction of Crux OB1 association were obtained. Observed high resolution (R ~ 48000) spectra and light curves in Strömgren bands were analysed. From the simultaneous light and radial velocity curve solutions, the absolute parameters of the components were determined with high precision for the first time. Component masses and radii were derived as M1 = 5.8 ±0.1 Mʘ, M2 = 5.0 ±0.1 Mʘ and R1 = 7.17 ±0.08 Rʘ, R2 = 6.46 ±0.08 Rʘ. The Fourier disentangling method was applied to the composite spectra of MQ Cen to obtain reconstructed component spectra. Then Kurucz (1993) atmosphere models were fitted to the component spectra and the temperatures of components were determined as T1 = 15000 ±600 °K and T2 = 13900 ±700 °K for primary and secondary stars, respectively. The modeling of the high resolution spectra revealed that the secondary component of MQ Cen rotates slower than the synchronous rotation velocity unlike the primary star which is in synchronous rotation. The photometric distance of 2650 ±150 pc was found to be consistent with the distance given for Crux OB1 associaton (2729 pc) by Kaltcheva and Georgiev (1993). Space velocity of the system support the membership MQ Cen to the Crux OB1 association as well as the derived distance. Age estimation was made by comparing the positions of components on H-R diagram with isochrone curves. Derived age of 75 ±3 Myr for MQ Cen is older than the age determined for Crux OB1 association (8 ±10 Myıl). This result implies that MQ Cen may belong to one of the older subgroups in the Crux OB1 association complex and the stellar formation in the complex started long ago then previously predicted. The positions of the components of MQ Cen on H-R diagram show that both components have reached the final stage of their Main Sequence lifetime and proceed to the Giant Branch.