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Fig. 1


[Sr/Ba] vs. [Ba/Fe] for i) our sample of EMP stars from the Large Program First Stars: filled symbols (blue squares for unmixed giants, Spite et al. 2005, red diamonds for mixed giants, black circles for dwarfs); and ii) green open squares for the CEMP stars in the same range of metallicity gathered from Aoki et al. (2001, 2002), Barbuy et al. (2005), Sivarani et al. (2006), Behara et al. (2010), Spite et al. (2013), and Yong et al. (2013). The dotted line at [Sr/Ba] = –0.5 represents the value of the r-only solar value of this ratio (Mashonkina & Gehren 2001). The EMP stars are all located in the left upper corner of the figure, many CEMP stars are located in the same region (they are CEMP-no), but another group (CEMP-s) has a high abundance of Ba: [ Ba/Fe ] ≳ + 1 associated with a low value of [Sr/Ba] (lower right region). In the left upper corner, the stars are gathered below the dashed line: [ Sr/Ba ] = 0.5−[ Ba/Fe ]. (Color figures are available in the electronic edition.)

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