Comparison of predicted SEDs for a 1 Myr old population with and without VMS. Left panel: The standard BPASS model with M_up = 100 M_⊙ is shown in gray (stellar emission only) and in black (including nebular continuum emission). Blue and red lines show the model extending up to 400 M_⊙, the former including only stellar emission, the latter the total continuum (stellar plus nebular continuum). Right panel: zoom on the UV domain, comparison the standard BPASS model with a population including only VMS (from 100 to 400 M_⊙). The dotted line shows the nebular continuum emission of the VMS-only-400 population.