Disk formation at the magnetosphere of wind-fed pulsars : applicationto VELA X-1.
Abstract
The disk formation in a wind-fed, rotating, accreting neutron star is considered in view of the fact that the angular momentum transfer by wind accretion is too small to account for large rates of spin-up and spin-down as observed. Under the assumption that the closed magnetosphere extends to the corotation radius it is shown that a disk will form through the interaction of the spherically accreting matter with the rotating magnetosphere. Long term spin-up and spin-down episodes then become possible due to the difference between the accretion torque transmitted by the disk and the deceleration by the accretion at the magnetosphere surface. Large rates of short-term pulse period change are attributed to the change in the accretion torque transmitted by the disk. Application of this model to the X-ray source Vela X-1 requires a large magnetic moment μ ≡ 1032 Gauss cm3, but once the high value for the magnetic field (1013 Gauss ⪉ B ⪉ 1014 Gauss) is accepted, a variety of observations fit well into the picture.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- August 1987
- Bibcode:
- 1987A&A...182...63B
- Keywords:
-
- Accretion Disks;
- Pulsar Magnetospheres;
- Pulsars;
- Stellar Mass Accretion;
- Stellar Winds;
- X Ray Binaries;
- Angular Momentum;
- Stellar Atmospheres;
- Stellar Magnetic Fields;
- Astrophysics