ИСТИНА

We study the rotational evolution of an accreting neutron star (NS), particularly the evolution of its magnetic angle (between the rotational and magnetic axes). The rotational evolution of the star is considered from a mechanical point of view, considering the relevant external torques. We discuss the pulsar losses during accretion, their enhancement due to the additional opening of the magnetic field lines by the disk, and the suppression of the magnetic field by the accreting matter. The basic model shows that if the axis of rotation of the NS does not coincide with the axis of the disk at the initial time, there is a relatively short period (a few thousand years) during which the magnetic angle of the star increases by up to 10-25 degrees. This means that the accretion contributes to the magnetic orthogonality of the star. On the other hand, the amplification of pulsar losses has the opposite effect, significantly decreasing the magnetic angle over the same timescale. After that, the evolution of the angle practically stops. Thus, the two approaches have different observational consequences. In general, the evolution of the angle has been carried out for different combinations of the magnetisation of the star and the accretion rate on it. Finally, an extension of the model used to the case of triaxial precession is also discussed.