Upper panel: dipole (ℓ = 1) average of the computed period spacings, , assessed in a range of periods that includes the periods observed in NGC 6905, shown as solid (dashed) curves corresponding to stages before (after) the maximum T_eff for different stellar masses. The location of NGC 6905 when we use the effective temperature derived by Ciardullo & Bond (1996), T_eff = 141 000  ±  10 000 K, and the period spacing Δ Π = 11.9693 ± 0.0988 s derived in Sect. 3.3 and assumed to be associated with ℓ = 1 modes, is highlighted with a magenta circle. The stellar mass derived from linear extrapolation is M_⋆ ∼ 0.818 M_⊙ if the star is before the maximum T_eff, and it is M_⋆ ∼ 0.861 M_⊙ if the star is after the maximum T_eff. Lower panel: same as in upper panel, but for the case in which the period spacing is assumed to be associated with ℓ = 2 modes (Δ Π = 11.9693 ± 0.0988 s). In this case, the stellar mass is M_⋆ = 0.596  ±  0.09 M_⊙ and M_⋆ = 0.590  ±  0.007 M_⊙ if the star is before or after the evolutionary knee, respectively.