Contour plot of the best-fit parameters: the photon index Γ, defined as Γ = β_o + 1, and the break energy. The contours correspond to regions of 68%, 90%, and 99% confidence level for two parameters. The χ² values for the different levels are shown in the figure.

Top: normalised spectrum of galaxy G1 (Fig. 9; Table 6) obtained with GTC/OSIRIS 3.6 days after the GRB. Several emission lines are detected at z = 0.2828. Hα is partly blended with a sky emission line. The error spectrum is shown in orange. The positions of telluric bands are highlighted by grey-shaded areas. Bottom: spectral energy distribution from 1600 to 24 000 Å (similar to Fig. 8). The solid line displays the best-fit model obtained with Le Phare (χ² = 3.1, number of filters = 4). The beige open squares represent the model predicted magnitudes. Upper limits are displayed as triangles.

Same as Fig. D.1 but for galaxy G2 (Fig. 9; Table 6). The fit statistics are χ² = 14.8 for eight filters. The redshift was set to z = 0.283 from the tuneable filters.

Same as Fig. D.1 but for galaxy G3 (Table 6). The fit statistics are χ² = 18 for nine filters.

X-shooter spectrum of GRB 120422A’s afterglow obtained 0.716 days after the burst. The top panel shows the combined UVB- and VIS-arm spectrum from 3150 to 10 000 Å. The absolute flux-calibrated spectrum is corrected for heliocentric motion and Galactic reddening. The spectral data are shown in black, and the corresponding noise level in grey. For illustrative purposes, we rebinned the spectrum to 2 Å bins. The positions of absorption lines that are typically associated with GRB absorbers are indicated by red lines (dotted if detected and dashed if a feature evaded detection). Nebular lines are shown in blue. The panels below zoom-in on each absorption and emission line (wavelength binning 0.15 Å). Table 4 summarises the fluxes and equivalent widths for each line. Regions that are heavily affected by atmospheric absorption (transparency: <20%) are indicated by the grey shaded areas.

Same as Fig. E.1 but for the host galaxy’s nucleus. Absorption lines are omitted since none was detected.