(a) -ray (black) and optical (colour) light curves of GRB 061007 all decaying with a steep power-law index from 137 seconds to 106 seconds. Despite its optical brightness (R~ 10.3 mag at 137 seconds), a reverse-shock optical flash is ruled out (adapted from [23, 60]). (b) Early-time (200–400 seconds) broad-band optical to -ray SED fitted with single absorbed power law (opt-X-) = 1.02 0.05 and rest-frame extinction mag (from [60]).
