Top panel: luminosity computed in the isothermal evolution L_isot for different values of the kick velocity for model L.00 and for a polytropic index γ = 4/3. Note the presence of a peak at about  ~20d after the merger, of a binary with total mass M ≃ 10⁶   M_⊙ and of a persistent luminosity for several days at values which are a factor of a few smaller. Bottom panel: comparison of L_isot for model L.00 when computed with a polytropic index γ = 4/3 (thick lines) or γ = 5/3 (thin lines). The comparison is made for two reference recoil velocities and shows that the results are very similar, although a stiffer EOS leads to slightly larger luminosities.