Modeled flux ratio at 70 (blue) and 160 μm (red dots) for different burst energies, all featuring the mean setting. Solid lines are linear fits. The dashed horizontal lines are the observations with confidence intervals (overlapping colored areas). The vertical black line indicates the best burst energy E_acc for both wavelengths. The 1σ-confidence interval is indicated. We use a χ²-minimization to determine E_acc, where we use linear fits (colored solid lines) as model values for both wavelengths. We take into account the observational errors and uncertainties of the modeled ratios, where the contribution of the latter is minor.