Membership of stars in faint galactic open clusters

Abstract

Low-dispersion spectra of the order of 1000 Å mm-1 have been obtained for stars in several faint galactic clusters with a transmission grating placed in front of the photographic plate at the Cassegrain focus of the Kavalur 102-cm telescope. The intensity distribution in the shorter wavelengths has been taken as the principal criterion for the spectral classification of the individual stars in the area covered by the photographic plate. The uncertainty in this procedure has been found to be about two spectral subclasses. A combination of these spectral classes with the visual magnitudes derived from the image diameters on the POSS charts provide the HR diagrams for each cluster area. These diagrams are adequate to establish the cluster membership of any star to a first approximation. This technique has been tested on six galactic open clusters, four of which are well-studied. We find good agreement both in terms of the ages of the clusters and individual stellar membership.