Response and residual plots for each confirmed species in KELT-9 b’s atmosphere. Each panel represents a different species. The order of the species is as follows (left to right): H I, Na I, Mg I, Ca II, Sc II, Ti II, Cr II, Fe I, Fe II, and Y II. Each plot contains a line of best fit plotted through the data of the response plot, spanned by two lines of worst fit. The identity line y = x is plotted to show how closely the model matches the data. The residual plot contains the residuals and the region spanning one standard deviation of the residual data.