SIMBAD references

A study of chemical composition for 23 A-type stars in four nearby open clusters (Pleiades, Coma, Hyades and Praesepe) has derived detailed abundances for Mg, Ca, Sc, Cr, Fe, and Ni from high resolution spectroscopy. These results are discussed using the microscopic diffusion model, which yields time-dependent element stratifications as in the case of Am stars. For the Pleiades, the youngest cluster, we find several atypical abundance patterns, which may be transient phases of the Am phenomenon. The members of the older clusters show globally more classical patterns.