Formation of low-mass binaries with millisecond pulsars

The study presents an evolutionary scheme which results in the formation of a low-mass binary consisting of a red dwarf mass of less than 0.3 solar mass and a rapidly rotating neutron star with a spin-period of a few ms and a surface magnetic field of less than 10 exp 9 G. The evolutionary sequences when, at the beginning of mass transfer, the donor star has a mass of 1 and 0.5 solar mass, and the orbital period of the system is 9.4 and 4.5 h, respectively, are computed. The rotational evolution of a neutron star is presented for the cases when, at the beginning of accretion onto the neutron star, the magnetic field is 1 x 10 exp 8, 5 x 10 exp 8, or 10 exp 9 G, and has a characteristic decay time of more than 10 exp 9 yr. One of the main components of the present scheme is the stage of evaporation of the mass-losing star which reduces the duration of the accretion stage to a few times 10 exp 7 yr. The stage of evaporation begins when the infalling plasma is pushed out by the magnetodipole radiation of the rapidly rotating neutron star, and heating of the red dwarf photosphere by hard X-rays and gamma rays generated in a neutron star magnetosphere sets in.