ours.

The hydrogen flash. {#mainflash}
-------------------

Our  model is a metal-free one with mass equal to $1\,M_\odot$ and an initial helium abundance $Y_i=0.23$, computed by neglecting both atomic diffusion and possible external pollution. The main properties of this model are listed in the first line of Table \[tab1\]. In this table we report initial conditions, main assumptions which characterize each case, the information whether the HEFM leads to a H-flash, and the final relevant surface abundances at the end of the H resp. He-flash for all the experiments performed (§ \[Hflash\]). The evolution of our standard model in the H-R diagram is shown in Fig. \[fig2\].

[lllccccccrrllc]{} S1$^\dagger$ & 0.23 & 1.0 & 1 & — & no & Saha & solar && 10.11 & 0.477 & 0.0088 & 0.0043 &\
S2$^\dagger$ & 0.235 & 1.0 & 1 & — & no & Saha & solar && 10.06 & 0.478 & 0.0085 & 0.0040 &\
S3 & 0.24 & 1.0 & 1 & — & no & Saha & solar && 10.02 & 0.241 & 0.0 & 0.0 &\
S4 & 0.25 & 1.0 & 1 & — & no & Saha & solar && 9.92 & 0.251 & 0.0 