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tokens: Zr The neutron-capture element Zr is predominately produced by AGB stars and is a first s -process peak element. The s -process contribution to Zr in the Solar system is 80percent (e.g. Simmerer etal. 2004 ; Sneden, Cowan Gallino 2008 ; Bisterzo etal. 2014 ). By determining the abundance of Zr, we expand on the measurements of Y, another first s-process peak element whose abundances were previously obtained by NS11 . Fig. 3 (a) shows [Zr/Fe] as a function of [Fe/H]. The dispersion in [Zr/Fe] is 0.12dex, which is larger than the error of 0.04dex. When considering the two populations, the scatter in [Zr/Fe] is smaller for the low- stars with a dispersion of 0.06dex compared to a dispersion of 0.13dex when combining the high- and TD stars. In addition to the difference in the dispersion of [Zr/Fe], the low- stars have a systematically lower [Zr/Fe] abundance compared to the high- and TD stars. Figure 3. Four s -process elements (Zr, La, Ce and Nd) versus [Fe/H]. The red circles indicate low- stars, the blue open circles indicate high- stars and the plus signs indicate TD stars. The 1 error is shown in the bottom left of each plot. This possible separation in the high- and low- populations is in agreement with the slight separation in abundance measurements of [Y/Fe] for the two populations seen in NS11 . As Zr and Y are both first-peak s -process elements, they are expected to follow the same trend. Fig. 4 demonstrates the difference in the Zr abundance for a low- star (HD 194598) and a high- star (HD 111980) at nearly the same metallicity (see Table 1 ). The low- star has a weaker Zr ii line than the high- star. While the effective temperature differs between these two stars by approximately 150K, all other lines in this region exhibit very similar strengths. Figure 4. MIKE spectra around the Zr line at 4208.98 for a low- star (HD 194598) and a high- star (HD 111980). A comparison between [Y/Fe] as measured by NS11 and [Zr/Fe] is presented in Fig. 5 . The abundance of Zr follows the abundance of Y, which is expected if Y and Zr have a common origin. While there is a systematic offset between [Y/Fe] and [Zr/Fe] that may be due to errors in the gf values of the lines, the important point is that the slope of the data is close to 1. The high- stars have a tighter correlation between [Y/Fe] and [Zr/Fe] compared to the low- stars. Figure 5. Comparison of [Y/Fe] (taken from NS11 ) and [Zr/Fe]. The red circles indicate low- stars, the blue open circles indicate high- stars and the plus signs indicate TD stars. The dashed line shows the one-to-one correspondence line. The 1 error is shown in the top left. 3.2 La, Ce and Nd We extend upon the Ba measurements of NS11 by determining abundances for other elements belonging to the second s -process peak, namely La, Ce and Nd. The s -process contribution to La in the Solar system is 75percent and there are a number of advantages with using La as an s -process indicator compared to Ba (e.g. Simmerer etal.