Malchenko S. Be stars of the spectral classes B0-B3 in the young open stellar clusters

3. Be phenomenon can be observed in 10-30 % early type stars of spectral classes B0-B3. At this moment there is no concrete and confident explanations of developing of Be phenomenon. The main problem is to determine whether Be phenomenon is manifested at a certain stage in the evolution of each star with a high sufficient angular momentum or it is inherent in some of the stars since their formation. The main goal of the research was to examine the evolutionary status of Be phenomenon. To do this, the research has the following objectives: (1) to obtain and explore the spectra of high and moderate resolution of early stars of spectral types В0-B3 in order to determine their possible binarity and (2) to find new Be stars with weak emission in Нa line. The following results were obtained. Population of Be stars in young open clusters h/chi Per, NGC 457, NGC 659, NGC 6871, NGC6913, NGC 7419 and in Berkeley 86 were analyzed and result are: spectral class and rotation rate were estimated for stars within observed clusters; the famous Be star V622 Per, which is a member of young cluster Per, was identified as a massive binary interacting system; the parameters of the orbit and the evolutionary status of this object were also defined. One (or two) new Be star was detected in the cluster h Per; population of Be stars of early spectral types В0-B3 in the young open clusters was studied. The patterns of Be stars' distribution were also determined which depend on the age of clusters. Maximum percentage of Be stars of spectral types В0-B3 was observed within clusters with the age of 12- 25 million years and decreased with age. This fact supports the hypothesis that Be stars are formed in the final stages of their lives on the main sequence and of leaving it.