Left-hand panel: cooling tail in the F ∝ L/L_Edd vs. K^{− 1 / 4} ∝ f_c plane with 1σ errors presented by black crosses for a hard-state PRE burst from 4U 1724−307 analyzed by Suleimanov et al. (2011b). Best-fit theoretical atmosphere model is shown with the blue curve (SolA001). A PRE burst from the same source (used in the this paper) is also presented with gray crosses and gray curve. Right-hand panel: temperature evolution of the Suleimanov et al. (2011b) burst. Blackbody temperature T_bb is shown for the cooling tail with black crosses. Blue crosses show the color-corrected temperatures T_eff(1 + z)^-1. The straight inclined lines show a powerlaw with an index of 4 corresponding to the F ∝ T⁴ relation.