On a spin-up phase in the evolutionary tracks of AR Scorpii and AE Aquarii

A question about the origin of a pulsar-like white dwarf in the low-mass binary system AR Scorpii is discussed. In our consideration we follow the accretion-driven spin-up scenario previously developed to explain the origin of a strongly magnetized fast rotating white dwarf in AE Aquarii. We find that the origin of AR Scorpii can be explained within this scenario provided the surface magnetic field of the white dwarf during the spin-up epoch was screened by the accreting matter by a factor of 50-100. This finding suggests that the fast rotating strongly magnetized white dwarfs in both systems were formed by a common mechanism.