Variation of the equivalent width (EW₀) of the absorption component of the N Vλ1240 (middle), C IVλ1550 (bottom) P-Cygni line profiles and the stellar He II 1640 Å emission (top) as a function of age assuming a continuous star formation history (left) and instantaneous burst models (right). Different tracks represent models with different IMF upper mass limits (M_up). Original BPASS models with M_up = 100 M_⊙ and 300 M_⊙ (using the wind prescription from Vink et al. 2001) are shown in red and orange, respectively, while BPASS models with the new VMS template spectra of Martins & Palacios (2022) are shown in yellow, green, blue, pink, and brown for M_up = 175 M_⊙, 225 M_⊙, 275 M_⊙, 325 M_⊙, and 475 M_⊙ respectively.