Wind accretion and magnetorotational evolution of neutron stars in binaries

Accretion changes drastically both the magnetic and spin evolution of neutron stars belonging to binary systems. Heating caused by accretion decreases the conductivity of the neutron star crust and accelerates the magnetic field decay if the currents maintaining this field are concentrated in the crust. The present paper considers this mechanism of the accretion-driven field decay in the case of accretion from the stellar wind of a companion. Such type of accretion is characterized by lower accretion rates (10(-12)M./yr greater than or equal to M greater than or equal to 10(-16) M./yr) comparing with accretion due to Roche-lobe overflow. The field decay accompanying the wind accretion is substantially slower but, nevertheless, it can strongly reduce the field strength of the neutron star because in some binaries the duration of the wind accretion phase is as long as similar to 10(9) yr. An influence of the wind on the spin evolution seems to be less pronounced. Our computations show that the neutron star cannot reach periods shorter than similar to 0.5 seven for a long accretion phase.