Observational properties of pre-cataclysmic binaries

Pre-cataclysmic variables (Pre-CVs) are detached, close binary systems; these lose angular momentum due to gravitational radiation and magnetic braking due to the stellar wind and evolve into cataclysmic variables (CVs). Previous studies on these kinds of detached binary systems have demonstrated that some of these evolve into semi-detached systems over the galactic age, and that they might evolve into CVs in the future. This study investigates the common envelope evolution stage, the evolutionary stages after common envelope and at the Pre-CV stage, the angular momentum loss process during these stages and the process through which these systems become CVs. In addition, using the telescopes available at Ege University Observatory, four detached, close binary systems that have the possibility of going through common envelope evolution in later evolutionary stages (V402 Lac, V380 Cas, DU Leo, UZ Sge) and one binary system that is at the evolutionary stage following the common envelope evolution (EG UMa) were observed and light curves were obtained. Among these systems, light curve analysis was performed and new minimum times were determined for V402 Lac, V380 Cas, DU Leo and UZ Sge systems. In addition to this, evidence pointing towards a possible third object in V402 Lac system was presented.