Some notes concerning open clusters and GAIA DR2 data

Abstract

Issues in applying the Gaia DR2 data to determine the main parameters of open star clusters and the use of a formal, two color diagram for the initial selection of cluster members are discussed. The possibility of using the catalog estimates of interstellar absorption is considered. It has been shown that these estimates correlate with the E(B - V) values; therefore, E(B - V) values known for many clusters can be used to obtain the interstellar absorption and color excesses in the Gaia system. Distance estimates obtained from the averaged trigonometric parallaxes of probable members are reliable up to distance of 1.5 - 2 kpc from the Sun.