Barium and yttrium abundances as a function of (a) primary mass, (b) eccentricity, (c) period, and (d) Roche-lobe radius of the WD progenitor normalized by the orbital separation. Median error bars are shown in gray. The plotted systems belong to the region M ₂ <0.75 and [Fe/H] < −0.08 (see Figure 3 and text for explanation). Although Y-enriched stars extend to high metallicities, we define the s-process domain as per Ba abundances following the existing convention. Roche-lobe radii are computed using the formula given by P. P. Eggleton (1983), with the initial–final mass relation used to obtain progenitor masses taken from J. D. Cummings et al. (2018).