Left panel: unstable ℓ = 1 mode periods (Π) in terms of the effective temperature, corresponding to the ELM WD model sequence with M_⋆ = 0.1762 M_⊙. Color coding indicates the value of the logarithm of the e-folding time (τ_e) of each unstable mode (right scale). The vertical line indicates the effective temperature of the template model analyzed in Fig. 3. Right panel: same as left panel, but for the case in which the action of the ε mechanism is neglected in the stability computations.