On the Torque Exerted by a Magnetically Threaded Accretion Disk
Abstract
Simple expressions are derived for the torque exerted by an accretion disk on a rotating, magnetized object (which may, for example, be a neutron star, a white dwarf, or a T Tauri star). In the equilibrium state (for which there is no net torque on the star), the inner edge of the Keplerian disk R0 is located very close to the corotation radius Rc, for physically plausible assumptions about the dissipation time of the wound-up field component; the equilibrium value omega crit of the "fastness parameter" omega ≡ (R0/Rc)3/2 lies in the range 0.875--0.95. Empirical constraints requiring omega crit to be significantly less than unity are thus incompatible with the magnetically threaded disk model.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1995
- DOI:
- 10.1086/309649
- Bibcode:
- 1995ApJ...449L.153W
- Keywords:
-
- ACCRETION;
- ACCRETION DISKS;
- STARS: MAGNETIC FIELDS;
- STARS: ROTATION