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.