2025ApJ...989L..52Z

We present the first detailed chemical abundances for seven GD-1 stream stars from Subaru/High Dispersion Spectrograph spectroscopy. Atmospheric parameters were derived via color calibrations (T_eff) and iterative spectroscopic analysis. LTE abundances for 14 elements (α, odd Z, iron peak, n-capture) were measured. Six stars trace the main orbit; one resides in a “blob.” All exhibit tightly clustered metallicities ([Fe/H] = -2.38; intrinsic dispersion smaller than 0.05 dex; average uncertainty is about 0.13 dex). While one star shows binary mass transfer signatures, the other six display consistent abundance patterns (dispersions < uncertainties). Their iron-peak elements (Sc, Cr, Mn, Ni) match Milky Way halo stars. In contrast, Y and Sr are systematically lower than halo stars of similar [Fe/H]. Significantly, six stars show consistently enhanced [Eu/Fe] ∼ 0.60 (σ = 0.08). A tight Ba-Eu correlation (r = 0.83, p = 0.04) exists, with [Ba/Fe] = -0.03 ± 0.05, indicating a common r-process origin. This extreme chemical homogeneity strongly supports an origin from a single disrupted globular cluster. The lack of light-element anticorrelations may stem from our sample size or the progenitor's low mass.