Contour map of the inverse of the quality function, 1/χ², showing the goodness of the fits in the plane Ω_S − Ω_C, considering all the observed rotational splittings associated with ℓ = 1, 2. We assume GD 278 rotates following a linear profile. The dashed green line indicates the corresponding solutions according to rigid rotation. The best-fitting solution is indicated with a black dot.