The four stars listed from Yong et al. (2013) were observed with Keck/HIRES at $R=48,000$. The spectra for the three stars from Spite et al. (2013) were collected with VLT/UVES (Dekker et al. 2000) at a resolving power of $R\sim39,000$. Note that, depending on the adopted model atmospheres, abundance scales, and different effective temperature scales in the analyses of the high-resolution spectra, there could be some systematic offsets between these three sets of analyses. However, we expect any such offsets to be small, and therefore do not attempt to correct for them here.

![image](f3.eps)

One limitation of this comparison sample is that, as noted from inspection of the table, the sample consists of mainly main-sequence turnoff stars with [\[Fe/H\]]{} $< -2.0$; hence it does not cover a wide range of [$T_{\rm eff}$]{} and [\[Fe/H\]]{}. Nevertheless, since it is more important to obtain accurate [\[C/Fe\]]{} estimates for metal-poor stars than metal-rich stars, it should still serve as an excellent sample to test how well our method performs in the low-metallicity regime.

Figure \[fig:hicfe\] illustrates a comparison of our measured carbon-abundance ratios with the adopted literature values based on high-resolution abundance analyses. The notation “SSPP” refers to the analysis of the low-resolution 