the red-dashed line is the best-matching synthetic spectrum generated with the parameters listed at the top of each plot, as determined by our methodology and the SSPP. The inset plot in each panel displays how the $\chi^{2}$ values over 4290–4318 Å change with \[C/Fe\] around the adopted \[C/Fe\], the vertical solid line. From inspection, one can see that an excellent match between the synthetic and observed spectra is achieved for these two stars.

Figure \[fig:limit\] shows examples of spectra with a lower limit (left panel) and upper limit (right panel) on [\[C/Fe\]]{} obtained following the technique described above. The spectrum in the left panel is a carbon-enhanced, metal-poor star, while the right panel is a typical thick-disk dwarf star. The layout of the figure is the same as for Figure 1. The inset plots display continuously declining or increasing values of $\chi^{2}$ over [\[C/Fe\]]{}. The solid vertical line in each panel indicates where the lower or upper limit is determined from the above prescription (which is clearly not at the minimum of $\chi^{2}$ values). As seen in the figure, a lower limit of \[C/Fe\] $= +1.20$ for the star in the left panel indicates that it is a highly C-enhanced 