Left: distribution of the sample star in the [Ba/Fe]–[Sr/Ba] plane. The solid black line shows the selection boundary, [Sr/Ba] = −0.8[Ba/Fe] − 0.7, and the dashed lines indicate the ±0.2 dex uncertainty band. Right: histogram of the signed offset from the selection boundary, Δ_cut = [Sr/Ba] + 0.8[Ba/Fe] + 0.7. The dashed line marks the adopted division at Δ_cut = 0, separating the low-[Sr/Ba] stars from the rest of the sample.