Spectral energy distributions of the afterglow of GRB 151027A. The four epoch data are collected in Table 3. The grey dashed lines represent the prediction of the model with external homogeneous medium density profile. The grey solid lines represent the prediction of the model with wind medium and late prompt. The afterglow component SEDs are shown by the dash-dotted lines (for the wind medium profile), while the late prompt component is shown by the dotted lines. The red long-dashed lines in the second and third panels show the best synchrotron spectrum compatible with the SEDs. The yellow regions show the possible positions of the cooling frequency ν_c.