Difference between equivalent widths measured on the perturbed and unperturbed spectra, Δ(EW) =  [EW_p − EW_u] /EW_u, of the primary star in Spica showing that the effects are ≤1.5%, and thus indicating that the interaction effects have a negligible impact on the spectral classification. Negative residuals indicate that the absorption in the perturbed profiles is weaker than in the unperturbed profiles. The different symbols correspond to: He i λ 4921(open triangles), He i λ 5875 (filled-in triangles), Si iii λ 4552 (stars) and Hβ (squares).