10.4 m GTC multi-band optical light curves (in flux density) of GRB 190829A/SN 2019oyw between 0.32 and 40.3 d post burst. The data are corrected for Galactic and host extinction, as discussed above. The i-band light curve of SN 2019oyw peaks around 20 d after the burst which appears to match with the late-time bump in the 10 keV Swift/XRT light curve (in red). The shaded vertical bars (in cyan) show the four epochs used to create the SED of the GRB 190829A afterglow. For comparison, the X-ray light curve (at 10 keV) of GRB 180728A (in grey) is also plotted; it has similar temporal features (including temporal decay indices, light-curve variability, late-time bump) to the X-ray light curve of GRB 190829A. Bottom panel: evolution of the XRT photon indices (Γ_XRT) of the two GRBs discussed. The horizontal black dashed line shows Γ_XRT equal to 2. The evolution of Γ_XRT indicates late-time softening during the ‘SN phase’, and demands a detailed investigation using a larger subset of such events.