CHEMICAL HOMOGENEITY IN THE HYADES

We present an abundance analysis of the heavy elements Zr, Ba, La, Ce, and Nd for Hyades FK dwarfs based on high-resolution, high signal-to-noise ratio spectra from Keck HIRES. The derived abundances show the stellar members to be highly uniform, although some elements show a small residual trend with temperature. The rms scatter for each element for the cluster members is as follows: Zr = 0.055, Ba = 0.049, Ce = 0.025, La = 0.025, and Nd = 0.032 dex. This is consistent with the measurement errors and implies that there is little or no intrinsic scatter among the Hyades members. Several stars thought to be nonmembers of the cluster based on their kinematics are found to deviate from the cluster mean abundances by about 2 . Establishing chemical homogeneity in open clusters is the primary requirement for the viability of chemically tagging Galactic disk stars to common formation sites in order to unravel the dissipative history of early disk formation.