Overview of the evolution of the protostar. (a) Kippenhahn diagram showing deuterium and hydrogen burning, with the red line being the total instantaneous stellar mass and the shadowed regions indicate convection. An element is considered to be burning when the energy generation rate is at least 10² erg g s⁻¹. The dotted lines indicate the limits of the region where the corresponding element is burned, and the solid lines indicate the center of the burning region for each element (colors). (b) Evolution of the stellar radius. (c) Internal distribution of the stellar angular velocity for different times (expressed as instant stellar masses). (d) Hertzsprung–Russell diagram of the accreting protostar (the bottom right corresponds to the initial time).