Nb−Zr plane for CEMP-s and -rs stars with measurable Nb abundances, along with barium stars and intrinsic or extrinsic S-type stars from Karinkuzhi et al. (2018) and Neyskens et al. (2015), respectively. The magenta shaded band indicates the expected location of stars polluted by material resulting from the s-process operating at temperatures between 1.0 (upper line) and 3.0 × 10⁸ K (lower line). These simple predictions assume that the chain of neutron captures along the Zr isotopes is in local equilibrium, as explained in Karinkuzhi et al. (2018).