Spectral energy distributions of the GRB 190829A afterglow using the optical-XRT data. (a) SED at ∼0.37 d (green), (b) SED at ∼2.2 d (magenta), (c) SED at ∼4.34 d (red), and (d) SED at ∼14.3 d (close to the i-band peak) showing the absence of thermal emission at XRT frequencies. In (b) and (c) optical SEDs and fitted BB contributions are also plotted in respective colours as described in Sect. 3.2. The derived values of the spectral indices are provided in Table 4.