Fig. 15

Spectra of the flashes. Flash name is shown in each panel where only a single frame is bright enough to analyze. For the others: a 161107, b 170201, and f 170204d. Red solid polygonal lines show the spectra for the frames where the flashes first appeared. The blue broken polygonal lines and a black thin polygonal line show the spectra at the 2nd- and 3rd-frames, respectively. Error bars represent one standard deviation of the background fluctuation. We do not show error bars for the 2nd- and 3rd-frames, but they are almost identical to those in the 1st-frame. The fluxes are reliable between 400 and 800 nm in wavelength (the non-shaded area). Blackbody spectra were best fitted to the plots in the non-shaded area and are shown by smooth curves. We show the blackbody temperatures in each panel. The exposure times are equal to the frame intervals and are listed in Table 2