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Stellar evolution models of B-type stars are still uncertain in terms ofinternal mixing properties, notably in the area between the convective core andthe radiative envelope. This impacts age determination of such stars inaddition to the computation of chemical yields produced at the end of theirlife. We investigated the thermal and chemical structure and rotation rate inthe near-core boundary layer of the double-lined B-type binary KIC4930889 fromits four-year Kepler light curve, ground-based spectroscopy, and Gaiaastrometry. We computed grids of 1D stellar structure and evolution models fordifferent mixing profiles and prescriptions of the temperature gradient in thenear-core region. We examined the preferred prescription and the near-corerotation rate using 22 prograde dipole modes detected by Kepler photometry. Weemployed a Mahalanobis distance merit function and considered various nestedstellar model grids, rewarding goodness of fit but penalising model complexity.Furthermore, we found a preference for either an exponentially decaying mixingprofile in the near-core region or absence of additional near-core mixing, butfound no preference for the temperature gradient in this region. The frequency(co)variances of our theoretical predictions are much larger than the errors onthe observed frequencies. This forms the main limitation on furtherconstraining the individual parameters of our models. Additionally,non-adiabatic pulsation computations of our best models indicate a need foropacity enhancements to accurately reproduce the observed mode excitation. Theeccentric close binary system KIC4930889 proves to be a promising target toinvestigate additional physics in close binaries by developing new modellingmethods with the capacity to include the effect of tidal interactions for fullexploitation of all detected oscillation modes.

Probing the physics in the core boundary layers of the double-lined B-type binary KIC4930889 from its gravito-inertial modes