Top panel: average of the posterior PDFs of the temperature kT and bolometric luminosity L_BOL of a redshifted blackbody model ([zashift*bbodyrad] in Xspec) compared to the five spectral slices of each QPE of RX J1301.9+2747. Weak QPEs are plotted with open squares, and strong QPEs with filled circles. The color code during the QPE evolution is the same as in Fig. 10. Lower panel: blackbody radius R_bb for each spectral slice, superimposed to the profiles of the 27 QPEs (gray thick lines) with spectral analysis available.