  Numerical simulations of the disruption of a dwarf companion moving in the
polar plane of a massive galaxy are presented. The constructed model is
compared with observational data on the recently discovered
low-surface-brightness stellar ring around galaxy NGC 5907. Constraints on the
ring lifetime (<=1.5 gyr after the first approach of the galaxies), on the
structure of companion -- the ring presecursor, and on mass of dark halo of the
main galaxy in whose gravitational field the companion moves are provided. The
dark halo mass within 50 kpc of NGC 5907 center cannot exceed 3 or 4 "visible"
masses.
