X-ray temporal index vs. spectral index during the post-plateau phase. The solid lines are for the decelerating phase of the coasting-in-wind model. Note that for a decelerating blast wave with max (ν _m , ν _c ) < ν and 2 < p, α is independent of k. The data in open circles (magenta color) are for the inconsistent sub-sample. The thick dotted line (blue color) is the prediction for phase 2 of the coasting-in-wind model considering the radiative loss of blast wave energy (requiring ν _c < ν _m when p > 2, and assuming _e = 0.3); it should be taken as an upper limit of α _{X, 2} for a given β _{X, 2} within this model because of the high _e value assumed. The exceptional burst that shows a spectral evolution is labeled.