Formation of low-mass binaries with millisecond pulsars

Abstract

The study presents anevolutionary scheme which results in the formation of a low-mass binaryconsisting of a red dwarf mass of less than 0.3 solar mass and a rapidlyrotating neutron star with a spin-period of a few ms and a surfacemagnetic 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 1and 0.5 solar mass, and the orbital period of the system is 9.4 and4.5 h, respectively, are computed. The rotational evolution of aneutron star is presented for the cases when, at the beginning ofaccretion onto the neutron star, the magnetic field is 1 x 10 exp 8, 5x 10 exp 8, or 10 exp 9 G, and has a characteristic decay time ofmore than 10 exp 9 yr. One of the main components of the presentscheme is the stage of evaporation of the mass-losing star whichreduces the duration of the accretion stage to a few times 10 exp 7yr. The stage of evaporation begins when the infalling plasma ispushed out by the magnetodipole radiation of the rapidly rotatingneutron star, and heating of the red dwarf photosphere by hard X-raysand gamma rays generated in a neutron star magnetosphere sets in.