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Convective cores are the hydrogen reservoirs of main sequence stars that aremore massive than around 1.2 solar masses. The characteristics of the coreshave a strong impact on the evolution and structure of the star. However, suchresults rely on stellar evolution codes, in which simplistic assumptions areoften made on the physics in the core. Indeed, mixing is commonly considered tobe instantaneous and the most basic nuclear networks assume beryllium at itsequilibrium abundance. Those assumptions lead to significant differences in thecentral composition of the elements for which the timescale to reach nuclearequilibrium is lower than the convective timescale. In this work, we show thatthose discrepancies impact the nuclear energy production and, therefore, thesize of convective cores in models computed with overshoot. We find that corescomputed with instantaneous mixing are up to 30% bigger than those computedwith diffusive mixing. Similar differences are found when using basic nuclearnetworks. Additionally, we observed an extension of the duration of the mainsequence due to those core size differences. We then investigated the impact ofthose structural differences on the seismic modeling of solar-like oscillators.Modeling two stars observed by Kepler, we find that the overshoot parameter ofthe best models computed with a basic nuclear network is significantly lower,compared to models computed with a full nuclear network. This work is anecessary step in improving the modeling of convective cores, which is key todetermining accurate ages in the framework of future space missions such asPlato.

Impact of central mixing scheme and nuclear reaction network on the extent of convective cores