Metal abundance in the Praesepe and Hyades clusters

Abstract

Calcium K-line photometry is reported for 27 A-type stars in the Praesepe cluster, and the data obtained are compared with previous K-line observations of Hyades stars. It is found that calcium and other metals are generally overabundant in Praesepe relative to field stars and that there is a considerable scatter in metal-abundance indices. Comparison with the Hyades results indicates that the Praesepe stars are as metal-enriched as the Hyades stars. These results are taken as evidence favoring Eggen's (1960) proposal that the Hyades and Praesepe clusters should be regarded as a single group having, on the average, about a factor-of-two higher metal abundance than solar-neighborhood field stars as well as a high internal dispersion in metal-line strengths. The questions of where and how the Praesepe-Hyades stars acquired their high average metal abundances, K-line strengths, and associated dispersions are briefly considered.