Interacting binary stars with Be component

In this thesis, photometric and spectroscopic study of three emission line stars, R Ara, V716 Cen and EM Cep, which are known to be binaries or candidates binaries with Be type components were carried out. New spectroscopic and/or photometric data of each system chosen were obtained. In addition to basic parameters of the systems, which were obtained from the analysis of observational data, emission features in the spectra due to the existence of Be type components were also studied. The relationship between the emission structures and the systems? binarity were investigated and the results were discussed. Due to insufficient spectroscopic data of R Ara in literature, its high resolution spectra were obtained and the secondary component was identified in the spectra for the first time. From the simultaneous solution of light and radial velocity curves, masses were determined as M1=5,40 M and M2=1,72 M and radii as R1=4,13 R and R2=6,18 R for the primary and secondary component respectively. Conservative mass transfer rate from the secondary to the more massive primary was determined to be 5,23×10?7M/yr from the O-C data constructed by using newly obtained and old times of minima. The mass transfer rate of R Ara was found rather high in comparison to the average mass transfer rate ( M ~ 10?11 ?10?7 M/yıl) determined for this type of binary stars. This high mass transfer rate support the strong emission features in spectra. The emission features are visible especially in Balmer and Helium lines and even in some metallic lines. To investigate these emission features, difference profiles of H? lines were constructed and the relationship of the emission with the orbital motion was studied. V716 Cen was observed spectroscopically and spectral lines of the secondary component were determined for the first time. From the simultaneous solution of light and radial velocity curves, masses of the components were determined as M1=5,93 M and M2=2,51 M and radii of the components as R1=4,14 R and R2=3,41 R. The system is composed of two main sequence stars with spectral types ix B5.5 and A3. The photometric distance of the system (340±10 pc) is consistent with the Hipparcos distance (337±72 pc). According to model atmosphere fitting to He I 4471 Å and Mg II 4481 Å lines, temperatures and projected rotational velocities of the components were found to be Te1=15500±50 K, Te1=9500±350 K, (vdönmesini)1=130±2 km/s and (vdönmesini)2=110±3 km/s for primary and secondary, respectively. Thus, observed rotational velocities imply synchronized rotation of components. In order to investigate the existence of circumstellar matter, the difference spectra of V716 Cen were constructed from the disentangled spectra which were obtained by using KOREL. The difference profiles of spectra show no detectable deviation from zero. Therefore, it is fair to conclude that there is no clear evidence for circumstellar matter in or around V716 Cen. In order to investigate the mechanisms proposed for EM Cep in the literature to explain the nature of the system, the absolute parameter were determined. Since EM Cep is member of a cluster, its distance (760 pc) is well known. From the colors, the spectral type of the system was determined as B2III (IV, V) . In this spectral type, stars, irrespective of their luminosity class, have radius and mass of 7R and 11M. EM Cep exhibits sometimes weak, sometimes strong line variations in Hydrogen and Helium lines, and rather complicated moving structures H? spectral line. The line variations determined from spectroscopic analysis do not support photometric period. However, the variations of emission and absorption features in spectra are clear. These structures and the sudden changes in the photometric light curve of the system imply a co-rotating gas clouds around the system. Key words: Interacting Binary Stars, Be Stars, Emission Structures, Spectroscopy, Absolute Parameters of Stars.