Instability window calculation at t≃ 40 ms after merger. From the angular frequency (Ω) we computed its gradient (s₀) and mask those points where s₀ > 0, namely those for which the standard MRI would be inactive. Then we evaluated the updated instability criterion, considering at once the two cases f > 0 and f < 0. In the right panel, blue points are unstable according to the updated MRI criterion, and red are those for which the magnetic gradients are large enough to switch off the instability; all coloured points are MRI-unstable according to the standard criterion.