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Sawtooth-like oscillations of black hole accretion disks

Published online by Cambridge University Press:  01 August 2006

Ryoji Matsumoto  and
Mami Machida
Ryoji Matsumoto
Affiliation:
Department of Physics, Faculty of Science, Chiba University 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522Japan email: [email protected]
Mami Machida
Affiliation:
Division of Theoretical Astronomy, National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo 181-8588, Japan email: [email protected]
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Abstract

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We studied the origin of quasi-periodic oscillations (QPOs) of X-rays in black hole candidates by three-dimensional global resistive magnetohydrodynamic simulations of accretion disks. Initial state is a rotating disk threaded by weak toroidal magnetic fields. General relativistic effects are simulated by using the pseudo-Newtonian potential. When the temperature of the outer disk decreases, the accreting matter accumulates into an inner torus.

We found that the inner torus is deformed into a crescent shape and that it shows sawtooth-like oscillations of magnetic energy with frequency 3-5Hz when the mass of the black hole is 10M⊙. The magnetic energy inside the torus is amplified until magnetic reconnection suddenly releases the accumulated magnetic energy. A new cycle of the oscillation starts when magnetic energy is amplified again. We found that high frequency QPOs with frequency around 100Hz in stellar mass black holes are excited when sawtooth-like oscillation appears in the inner torus.

Keywords

accretionaccretion disks – MHD – QPO
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S238: Black Holes from Stars to Galaxies – Across the Range of Masses , August 2006 , pp. 37 - 42
Copyright
Copyright © International Astronomical Union 2007

References

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Machida, M., Nakamura, K. E., Matsumoto, R. 2006, PASJ, 58, 193CrossRefGoogle Scholar