Synthesis of the Th region for HD 115444, HD 186478, BD +8 2548, M92 VII‐18, and HD 108577. Left panels show the overall synthesis with the best‐fit Th abundance, as well as the individual contributions of the major contaminants Fe and ¹³CH. Right panels show the best synthesis and the change in the fit if the Th abundance is changed by ±0.10 dex. For HD 108577, the fit to the data would be improved if the Fe I abundance were ~0.5 dex lower than the value adopted from EW analysis. However, the derived Th abundance would not change.