Temporal decay index α_steep vs. spectral index β_steep of the first segments of Type II (green stars) and Type Ib (pink triangles) light curves of the present sample. Grey symbols refer to the sample of Margutti et al. (2011). The black stars track the positions for the different β(t) of GRB 090618 and GRB 081203A. The grey solid line corresponds to the expectation for the HLE: α = 2 + β. The shaded area corresponds to the expectation for the structured jet (). The blue lines correspond to the expectations for the synchrotron emission from AE ejecta: α = 1.5β + 1.5 for thick ejecta (solid line) and α = 3β + 3 for thin ejecta (dashed line). The red lines correspond to the expectations for the SSC emission from AE ejecta: α = 1.5β + 3.5 for thick ejecta (solid line) and α = 3β + 5 for thin ejecta (dashed line).