Disc accretion by magnetized neutron stars : a reassessment of the torque.
Abstract
The torque exerted on a magnetized neutron star undergoing steady, axisymmetric disc accretion is re-evaluated. As in the widely adopted model of Ghosh and Lamb, the magnetospheric field is assumed to thread the disc both inside and outside the radius of corotation, yielding opposing contributions to the net torque from the forward- and backward-swept field lines. It is shown, however, that the particular pitch distribution postulated by Ghosh and Lamb is not consistent, since the resulting magnetic pressure would disrupt their disc beyond the corotation point. By taking the winding rate proportional to the poloidal rather than the toroidal component of the field, the author obtains a more realistic behaviour for the magnetic stresses generated by the rotational shear. He then discusses the results in the light of period-change measurements for several binary X-ray pulsars.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- September 1987
- Bibcode:
- 1987A&A...183..257W
- Keywords:
-
- Accretion Disks;
- Magnetic Stars;
- Neutron Stars;
- Stellar Models;
- Torque;
- X Ray Binaries;
- Magnetohydrodynamic Flow;
- Pulsars;
- Stellar Magnetic Fields;
- Stellar Mass Accretion;
- Stellar Rotation;
- Astrophysics