On the coupling between helium settling and rotation-induced mixing in stellar radiative zones.: III.: Applications to light elements in population I main-sequence stars

In the two previous papers of this series, we have discussed the importance of the mu-gradients due to helium settling in rotation-induced mixing, first in an approximate analytical way, second in a two-dimensional numerical simulation. We have found that, for slowly rotating low-mass stars, a process of creeping paralysis,'' in which the circulation and the diffusion are nearly frozen, may take place below the convective zone. Here we apply this theory to the case of lithium and beryllium in Galactic clusters, especially the Hyades. We take into account the rotational braking with rotation velocities adjusted to the present observations. We find that two different cells of meridional circulation appear on the hot side of the lithium dip'' and that the creeping paralysis process occurs, not directly below the convective zone, but deeper inside the radiative zone, at the top of the second cell. As a consequence, the two cells are disconnected, which may be the basic reason for the lithium increase with effective temperature on this side of the dip. On the cool side, there is just one cell of circulation, and the paralysis has not yet set in at the age of the Hyades; the same modeling accounts nicely for the beryllium observations as well as for the lithium ones.