The study of massive stars with 50 Msun initial mass at different evolutionary stages

We will present results of studies of several massive stars at different evolutionary stages, but with similar values of the initial mass: O-supergiants belonging to association Cyg OB2, unique LBV/post-LBV - Romano's star and two Wolf-Rayet stars - WR156 and FSZ35. All these stars have similar initial mass of about 50 Msun. It allows us to consider them a single star at different moments of life, and it gives an opportunity to track changes in the physical parameters (such as effective temperature, luminosity, mass loss rate, wind velocity) and chemical abundances during the life of a massive star. It is important to test the current evolution theories of such objects.