HARVARD 20, A CLUSTER CONTAINING A YELLOW SUPERGIANT.

Abstract

ABSTRACT UBV photometry and MK spectral types are presented for stars in the open cluster Harvard 20. Star counts are used to delineate the boundaries of this poorly-populated cluster (diameter = 9 arc min) and ZAMS fitting is used to derive a cluster distance of 1.75 ± 0.08 kpc. The evolutionary age of the cluster is estimated to be ̃6 (± 1) × 107 years, and a nonvariable G5 Ib supergiant, HDE 350801, is found to be a likely member. A comparison is made between Harvard 20 and other poor clusters of similar age which contain cepheid variables.