Effect of transition region resolution (∆s_min) on the XUV spectra of κ¹ Ceti (left) and EK Dra (right). The top and middle panels display the bin-averaged XUV spectra for varying resolutions, with different colours indicating different resolutions. The bin size definition follows Fig. 3. The bottom panels illustrate the computed X-ray luminosity as a function of ∆s_min . The dotted lines indicate the results obtained using the LTRAC method, where the transition region is artificially broadened. The X-ray luminosity is expected to saturate at this level when computed with adequate resolution.