The gap in the H-R diagram of open clusters with special reference to NGC 2169, NGC 1778 and TR 1

Abstract

The colour-magnitude diagrams of the open clusters NGC 1778 and Tr I indicate the presence of gaps on the rising branches of the evolving main sequnces. The positions of these gaps are compared with those found in other clusters and the effect of evolution on the position of the gap is discussed. The initial luminosity functions of these clusters as also for NGC 2169, closely fit the respective cluster luminosity functions.