Equivalent widths in mÅ of the barium line for typical red giants as a function of temperature. The coloured lines show equal metallicities (blue for [Fe/H] = −1.0, orange for [Fe/H] = −0.5, green for [Fe/H] = 0.0, and red for [Fe/H] = +0.5). The size of the symbols indicates the surface gravities corresponding to a given T_eff and [Fe/H] according to a typical isochrone. The sizes go from largest being log g = 1.7 to the smallest being log g = 0.0. The equivalent width of the Ba line is relatively insensitive to the surface gravity (a change of 1 dex in log g changes the equivalent width by less than 3%.).