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The overall evolution of low-mass stars is heavily influenced by theprocesses occurring in the stellar interior. In particular, mixing processes inconvectively unstable zones and overshooting regions affect the resultingobservables and main sequence lifetime. We study the effects of differentconvective boundary definitions and mixing prescriptions in convective cores oflow-mass stars, to discriminate the existence, size, and evolutionary stage ofthe central mixed zone by means of asteroseismology. We implemented the Ledouxcriterion for convection in our stellar evolution code, together with atime-dependent diffusive approach for mixing of elements when semiconvectivezones are present. We compared models with masses ranging from 1 M* to 2 M*computed with two different criteria for convective boundary definition andincluding different mixing prescriptions within and beyond the formal limits ofthe convective regions. Using calculations of adiabatic oscillationsfrequencies for a large set of models, we developed an asteroseismic diagnosisusing only l=0 and l=1 modes based on the ratios of small to large separationsr01 and r10 defined by Roxburgh & Vorontsov (2003). These variables are almostlinear in the expected observable frequency range, and we show that their slopedepends simultaneously on the central hydrogen content, the extent of theconvective core, and the amplitude of the sound-speed discontinuity at the coreboundary. By considering about 25 modes and an accuracy in the frequencydeterminations as expected from the CoRoT and Kepler missions, the technique wepropose allows us to detect the presence of a convective core and todiscriminate the different sizes of the homogeneously mixed central regionwithout the need of a strong a priori for the stellar mass.

Constraining mixing processes in stellar cores using asteroseismology. Impact of semiconvection in low-mass stars