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HD49330 is a Be star that underwent an outburst during its five-monthobservation with the CoRoT satellite. An analysis of its light curve revealedseveral independent p and g pulsation modes, in addition to showing that theamplitude of the modes is directly correlated with the outburst. We modelledthe results obtained with CoRoT. We modelled the flattening of the structure ofthe star due to rapid rotation in two ways: Chandrasekhar-Milne's expansion and2D structure computed with ROTORC. We then modelled kappa-driven pulsations. Wealso adapted the formalism of the excitation and amplitude of stochasticallyexcited gravito-inertial modes to rapidly rotating stars, and we modelled thosepulsations as well. We find that while pulsation p modes are excited by thekappa mechanism, the observed g modes are a result of stochastic excitation. Incontrast, g and r waves are stochastically excited in the convective core andtransport angular momentum to the surface, increasing its rotation rate. Thisdestabilises the external layers of the star, which then emits transientstochastically excited g waves. These transient waves produce most of thelow-frequency signal detected in the CoRoT data and ignite the outburst. Duringthis unstable phase, p modes disappear at the surface because their cavity isbroken. Following the outburst and ejection of the surface layer, relaxationoccurs, making the transient g waves disappear and p modes reappear. This workincludes the first coherent model of stochastically excited gravito-inertialpulsation modes in a rapidly rotating Be star. It provides an explanation forthe correlation between the variation in the amplitude of frequencies detectedin the CoRoT data and the occurrence of an outburst. This scenario could applyto other pulsating Be stars, providing an explanation to the long-standingquestions surrounding Be outbursts and disks.

Transport of angular momentum by stochastically excited waves as an explanation for the outburst of the rapidly rotating Be star HD49330