Quantity ϵ² as a function of time for our best models with the change on metallicity: E_150_01_Z028 and E_150_03_Z028. The elements represented are the same as in Fig. 1. With a dashed line and a grey area is indicated the value of ϵ² = 0.0485 and the acceptance region we considered for our models. With a black solid line, the value ϵ² = 0 represents the situation where all the parameters modeled are equal to the ones observed simultaneously.