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QUASI-PERIODIC OSCILLATIONS AS GLOBAL HYDRODYNAMIC MODES IN THE BOUNDARY LAYERS OF VISCOUS ACCRETION DISKS

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Author
Erkut, M. Hakan
Psaltis, Dimitrios
Alpar, M. Ali
Type
Article
Date
2008-11-10
Language
en_US
Metadata
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Abstract
The observational characteristics of quasi-periodic oscillations (QPOs) from accreting neutron stars strongly indicate the oscillatory modes in the innermost regions of accretion disks as a likely source of the QPOs. The inner regions of accretion disks around neutron stars can harbor very high frequency modes related to the radial epicyclic frequency kappa. The degeneracy of kappa with the orbital frequency Omega is removed in a non-Keplerian boundary or transition zone near the magnetopause between the disk and the compact object. We show, by analyzing the global hydrodynamic modes of long wavelength in the boundary layers of viscous accretion disks, that the fastest growing mode frequencies are associated with frequency bands around kappa and kappa +/- Omega. The maximum growth rates are achieved near the radius where the orbital frequency Omega is maximum. The global hydrodynamic parameters such as the surface density profile and the radial drift velocity determine which modes of free oscillations will grow at a given particular radius in the boundary layer. In accordance with the peak separation between kHz QPOs observed in neutron star sources, the difference frequency between two consecutive bands of the fastest growing modes is always related to the spin frequency of the neutron star. This is a natural outcome of the boundary condition imposed by the rotating magnetosphere on the boundary region of the inner disk.
Subject
accretion
accretion disks
stars: neutron
stars: oscillations
X-rays: stars
x-ray binaries
frequencies
büyüme
toplanma diskleri
yıldız: nötron
yıldız: salınımlar
X-ışınları: yıldız
X-ışın çiftleri
frekansları
URI
http://hdl.handle.net/11413/1149
Collections
  • Makaleler / Articles [209]
  • Scopus Publications [724]
  • WoS Publications [1016]

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İstanbul Kültür University

Hakkında |Politika | Kütüphane | İletişim | Send Feedback | Admin

Istanbul Kültür University, Ataköy Campus E5 Karayolu Üzeri Bakırköy 34158, İstanbul / TURKEY
Copyright © İstanbul Kültür University

Creative Commons Lisansı
IKU Institutional Repository, Creative Commons Alıntı-GayriTicari-Türetilemez 4.0 Uluslararası Lisansı ile lisanslanmıştır.

Designed by  UNIREPOS