A. G. Nikiforov, V. D. Bychkov, M. V. Barkov

Using the ssrAp star 33 Lib (HD137949) as an example, we show that magnetic braking caused by the interaction of a strong magnetic field with a stellar wind can play a key role in slowing the rotation of ssrAp stars. Numerical modeling of stellar rotation spin-down in the MESA package, taking into account the evolution of magnetic fields and the stellar wind, shows that stars with rotation periods of up to 80 years and longer can form. Moreover, braking by a magnetized wind makes it possible to estimate the mass-loss rate for stars of moderate mass ($1.25 M_\odot < M < 2 M_\odot$), which is difficult to do by other methods. We introduce the dimensionless parameter $Ξ$, which reflects the spin-down time and the stellar lifetime. Thus, when $Ξ\gg 1$, braking is important, whereas when $Ξ\ll 1$, it is negligible.