Orbital phase dependence of the turn-on times of Hercules X-1
A ring of matter at a given radius in an accretion disk in a binary system will precess if it is tilted relative to the binary orbital plane. When the effect of the time variation of the torque due to the companion star is included in the dynamics, the ring orientation is found to undergo a significant periodic perturbatuion with respect to the previously known uniform precession. We find that the ring motion is better described by a vector, normal to the ring plane, whose tip periodically traces out a small ellipse centered on the tip of a uniformly precessing vector. We demonstrate that this disk ''wobble'' can be utilized to explain why the X-ray turn-ons of Hercules X-1 preferentially occur around orbital orbital phases 0.2 and 0.7. If the slaved disk model for the origin of the 35/sup d/ cycle is valid, then the accretion disk around Her X-1 may be large enough for the forced precession period of matter near the disk edge to be significantly smaller than 35/sup d/. In this case the presence of periodic mass transfer, together with the difference in factor in the orbital phase dependence of the turn-on times. We find that it is not necessary to invoke circulating structure on the disk rim, as proposed by Crosa and Boynton, to explain the turn-on orbital phase dependence.
- Research Organization:
- Center for Space Research and Department of Physics, Massachusetts Institute of Technology
- OSTI ID:
- 6427127
- Journal Information:
- Astrophys. J.; (United States), Vol. 262:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
BINARY STARS
STAR ACCRETION
STAR MODELS
COSMIC X-RAY SOURCES
ORBITS
PRECESSION
TORQUE
TWO-BODY PROBLEM
COSMIC RAY SOURCES
MANY-BODY PROBLEM
MATHEMATICAL MODELS
STAR EVOLUTION
STARS
640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar
Radio & X-Ray Sources