Dynamics of the Flows Accreting onto a Magnetized Neutron Star

Abstract

Non-stationary column accretion onto a surface of a magnetized neutron star is studied with a numerical code based on modified first-order Godunov method with splitting. Formation and evolution of shocks in the column is modeled for accretion rates ranging from 10^{15} g/s to 10^{16} g/s and surface magnetic fields ranging from 5*10^{11} G to 10^{13} G. Non-stationary solutions with plasma deceleration at collisionless oscillating shocks are found. The kinetic energy of the accreting flow efficiently transforms into a cyclotron radiation field. Collisionless stopping of the flow allows a substantial part of accreting CNO nuclei to avoid spallation and reach the surface. The nuclei survival fraction depends on the surface magnetic field, being higher at lower magnetic fields.