6 HZ quasiperiodic oscillations from low-mass X-ray binaries - The sound of an accretion disk?
Abstract
Quasiperiodic oscillations (QPOs) at frequencies of 5-8 Hz are a common feature of low-mass X-ray binaries (LMXBs) during their normal branch (NB) spectral states. We propose that this frequency band is essentially a band of rotation frequencies in a thick accretion disk. The high luminosities in the NB state give rise to the thick disk and slow down the dynamical timescales. Density and optical-thickness perturbations in a subsonic region of the disk have the frequency spectrum of sound in a rotating medium. X-rays scattered through the subsonic region are modulated by long wavelength optical-thickness oscillations whose frequencies, determined by the rotation rate and vorticity, are observed as the NB QPOs.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- April 1992
- Bibcode:
- 1992A&A...257..627A
- Keywords:
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- Accretion Disks;
- Stellar Oscillations;
- X Ray Binaries;
- Optical Thickness;
- Stellar Evolution;
- Stellar Mass;
- Stellar Rotation;
- Astrophysics