Yonetoku relation obtained from the single-bin sample. Black stars represent GRBs from the Band subsample, while colored dots represent GRBs from the synchrotron subsample. The color scale is associated with the frequency ratio, ν_m/ν_c, derived from the synchrotron fit. We fit a power law to the whole single-bin sample (left-hand panel) and to the GRBs in the synchrotron subsample in an intermediate cooling regime (right-hand panel). The straight black line represents the best-fit line from the linear fit, and the green-shaded area the relative 3σ scatter region. For comparison, the dashed black line represents the best-fit line from Yonetoku et al. (2004).