Left panel: combined cooling tail in the F ∝ L/L_Edd vs. K^{− 1 / 4} ∝ f_c plane with 1σ error limits presented by crosses. Gray crosses show the burst evolution before the touchdown. Best-fit theoretical atmosphere models are shown by blue (SolA001) or red (He) curves. Right panel: temperature evolution of the bursts. Blackbody color temperature T_c is shown for each cooling tail with black crosses. Red (He) or blue (SolA001) crosses show the color-corrected temperatures T_eff(1 + z)^-1. Dashed lines show a powerlaw with an index of 4 corresponding to the F ∝ T⁴ relation. Highlighted gray area marks the region of the cooling tail used in the fitting procedures.