Elemental abundance ratios in halo stars provide information on nucleosynthesis, chemical evolution, and accretion of dwarf galaxies at early times in the Milky Way because these ratios depend on the initial mass function (IMF) of core-collapse supernovae (CC, SNe) and on the role of Type Ia, SNe in making the elements. By determining very precise stellar parameters and abundances for a sample of intermediate-metallicity halo stars, we aim to estimate the intrinsic dispersion of various abundance ratios. We determined differential abundances of C, O, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Y, and Zr from high signal-to-noise VLT/UVES spectra for 25 turnoff stars with -2. 4 < < -1. 3. Effective temperatures were obtained from profiles of the Hβ line and surface gravities from Gaia parallaxes. The spectral analysis was based on 1D model atmospheres assuming local thermodynamic equilibrium (LTE), but we applied 3D non-LTE corrections for several elements. The dispersion in linear fits to the - relations is around a factor of two smaller than that found in previous studies. After correction for measurement errors, the 1-σ intrinsic dispersion of at a given metallicity is 0. 09, dex for Y and Zr, 0. 05-0. 07, dex for C, O, and Al, 0. 03-0. 05, dex for Mg, Ca, Sc, Ti, V, Mn, and Zn, and < 0. 03, dex for Cr, Co, and Ni. We find strong correlations between the residuals in the - fits for the α-capture elements (Mg, Al, Ca, Sc, and Ti) and between the residuals for Y and Zr. Correlations between the residuals in the - fits and the effective temperature can be explained by differential atomic diffusion between elements, but its contribution to the scatter of is of minor importance. Both stochastic effects in sampling the IMF of CC, SNe and differences in the Type, Ia to CC, SNe enrichment ratio between star-forming regions are likely required to explain the intrinsic dispersion of.
Nissen et al. (Fri,) studied this question.