Pre-Main-Sequence evolution of rotating low-mass stars

The evolutionary behaviour of rotating low-mass stars in the mass range 0.2 and 0.9M has been investigated during the pre-Main-Sequence phase. The angular momentum is conserved locally in radiative regions and totally in convective regions, according to a predetermined angular velocity distribution depending on the structure of the star. As the stars contract toward the zero-age Main Sequence, they spin up under the assumption that the angular momentum is conserved during the evolution of the stars. When the stars have differential rotations, their inner regions rotate faster than the outer regions. The effective temperatures and luminosities of rotating low-mass stars are obtained lower than those of non-rotating stars. They have lower central temperature and density values compared to those of non-rotating stars.