Impact of disc-outflows in accreting neutron stars

Abstract

In this paper, we propose a model for accreting neutron stars in which the mass outflow driven from the disc plays an important role. We assume a geometrically thin accretion disc surrounding a magnetic neutron star and apply a power-law dependence of radius for the accretion rate due to mass loss rate, $\dot{M}_w\propto r^{\lambda }$. We suppose that the outflows driven from accretion discs extract the mass from the inflow, and the angular momentum of the outflows can be deposited into or taken away from the inflow. We consider the present model in situations that the inner radius of the disc is larger than the neutron star radius and lies within the corotation radius. In such situations, the solutions imply that the disc rotation in the inner transition zone outstandingly changes in the presence of the outflow. The rotation of the inner disc increases (or decreases) and the width of the inner transition zone become narrow (or wide) when the angular momentum of outflow is deposited into (or taken away from) the inflow. In this paper, we also investigate the influences of the disc-outflow on the time rate of the pulsation period of the star ($\dot{P}_*$). The solutions imply that the spin period rate of the star increases in the presence of the outflows driven from the disc.