Comparison between abundances of RGB stars in NGC 6397 and halo field stars. The blue filled squares represent the mean abundances of the NGC 6397 stars assigned to the first generation and the red diamonds the mean of the second generation. The error bars mark the 1σ dispersion. Upper limits are treated as detections for the second generation averages for Al (two stars) and O (one star) when computing the mean and standard deviation. The literature data for halo field stars are assembled as follows; bullets represent Gehren et al. (2006), star symbols represent Andrievsky et al. (2007, 2008, 2010), open triangles Cayrel et al. (2004), and open diamonds Nissen et al. (2002).
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