Daugiaspalvė žvaigždžių fotometrija ir klasifikacija padrikojo spiečiaus NGC 6811 srityje

Abstract

The thesis examines the characteristics of the clusters and their distribution in our Galaxy, the process of development of stars with various masses, the photometry and classification of stars in various photometric systems, and the ways of determination of the distance for the stars and the clusters. The area of the open cluster NGC 6811 in Cygnus is investigated by CCD photometry in the Vilnius seven-color system. Magnitudes and color indices are determined for 337 stars. Photometric spectral types, color excesses, interstellar extinctions and distances are determined for 296 stars down to V = 16 mag in the 17' × 17' area. Using the photometric data [3], the cluster membership for 50 stars was confirmed, as identified by their proper motions [4]. ~ 70 % of the rest of 246 stars are suspected to be photometrical members of the cluster. The suspected cluster stars show a differential interstellar extinction ranging from 0,1 to 0,35 mag. It was refined that the open cluster NGC 6811 is at a mean distance of 1020 ± 56 pc. The mean interstellar extinction in the area of the cluster is 0.22 ± 0.01 mag.