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Astron. Astrophys. 323, L5-L8 (1997)
Letter to the Editor
Rotational splitting effect in neutron star QPOs
L. Titarchuk 1, 2 and
A. Muslimov 1
1 Laboratory for High Energy Astrophysics, Goddard Space
Flight Center, Greenbelt, MD 20771, USA
2 George Mason University/CSI,
Fairfax, VA 22030, USA
Received 24 April 1997 / Accepted 6 May 1997
Abstract
We explain the peak spacing in the power spectra of millisecond
variability detected by the Rossi X-ray Timing Explorer (RXTE) in the
X-ray emission from the LMXBs (Sco X-1, 4U1728-34, 4U1608-522,
4U1636-536, etc) in terms of the rotational splitting of an intrinsic
frequency (which is of order of the local Keplerian frequency) caused
by an accretion disk. We calculate this effect and demonstrate that
there is a striking agreement with the observational data. We show
that the observed discrete frequencies ranging from 200 to 1200 Hz can
be described by a whole set of overtones. For higher overtones (lower
frequencies, ![[FORMULA]](img1.gif)
100 Hz) the ratio between
frequencies is determined by the quantum numbers alone. We suggest
that a similar phenomena should be observed in Black Hole (BH) systems
for which the QPO (quasi-periodic oscillation) frequency should be
inversely proportional to the mass of the compact object. For BH
systems the characteristic frequency of oscillations should therefore
be a factor of 5-10 less than for a neutron star system.
Key words: Accretion:
disk 
binaries: LMXBs
X-Rays: QPOs
Send offprint requests to: L. Titarchuk
Contents
- 1. Introduction
- 2. The Effect of Rotational Splitting by an Accretion Disk
- 3. Explanation of QPO Frequencies in Terms of Rotational Splitting
- 4. Summary
- Acknowledgements
- References
© European Southern Observatory (ESO) 1997
Online publication: June 5, 1998
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