Left panel: averaged 10-pc M-dwarf spectrum with different models. All the models are labelled in the legend, where names follow the XSPEC convention, and the letter G stands for the Gaussian components used to fit single emission lines (dotted lines). Right panel: temperature versus line ratio assuming a single thermal component. The dark red and navy lines show the expected O VIII/OVII and NeX/NeIX ratios from AtomDB. Vertical dashed and dotted lines mark ratios derived from Gaussian normalisations in Table 2.