A new look at spherical accretion in High Mass X-ray Binaries

TL;DR

This paper revisits spherical accretion in High Mass X-ray Binaries, emphasizing the role of magnetic fields in the accreting material, which alters the accretion process and neutron star spin evolution.

Contribution

It introduces a model incorporating the magnetic field of the accreting flow, explaining entry rates and spin changes better than previous non-magnetized models.

Findings

Magnetic fields in accreting material significantly influence accretion dynamics.

Turbulent diffusion can facilitate matter entry into the magnetosphere.

Torque on neutron stars is higher with magnetic flow than in non-magnetized models.

Abstract

Currently used model of spherical accretion onto a magnetized rotating neutron star encounters major difficulties in explaining the entry rate of accreting material into the stellar field and spin evolution of long-period X-ray pulsars. These difficulties can be, however, avoided if the magnetic field of the material captured by the neutron star is incorporated into the model. The magnetic field of the flow itself under certain conditions controls the accretion process and significantly affects the parameters of the accreting material. The mode by which the accretion flow enters the stellar magnetosphere in that case can be associated with Bohm (or turbulent) diffusion and the torque applied to the neutron star appears to be substantially higher than that evaluated in the non-magnetized accretion scenario.