Rotational Evolution of Low-Mass Stars

From observational data on rotation periods and ages we deduce the evolution of surface rotational velocity of low-mass main sequence stars from the age of the Pleiades to the solar age. The t1/2 increase of the rotation period is shown to apply to stars of man between 1.1 and 0.5 solar masses with a rate larger for smaller masses. It is shown that time scale of the solar wind braking action is consistent with an angular momentum transport from the radiative core to envelope but with a rate not sufficient to justify the internal rotation deduced from solar oscillations.