The s-process weak component: uncertainties due to convective overshooting

Using a new s-nucleosynthesis code, coupled with the stellar evolution code Star2003, we performed simulations to study the impact of the convection treatment on the s-process during core He-burning of a 25 Msun star (ZAMS mass) with an initial metallicity of Z=0.02. Particular attention was devoted to the impact of the extent of overshooting on the s-process efficiency. The results show enhancements of about a factor 2-3 in s-process efficiency (measured as the average overproduction factor of the 6 s-only nuclear species with $60\lesssim A\lesssim 90$) with overshooting parameter values in the range 0.01-0.035, compared to results obtained with the same model but without overshooting. The impact of these results on the p-process model based on type II supernovae is discussed.