Joshua C. Dolence, Charles F. Gammie, Hotaka Shiokawa, Scott C. Noble
We report transient quasi-periodic oscillations (QPOs) on minute timescales
in relativistic, radiative models of the galactic center source Sgr A*. The
QPOs result from nonaxisymmetric $m=1$ structure in the accretion flow excited
by MHD turbulence. Near-infrared (NIR) and X-ray power spectra show significant
peaks at frequencies comparable to the orbital frequency at the innermost
stable circular orbit (ISCO) $f_o$. The excess power is associated with inward
propagating magnetic filaments inside the ISCO. The amplitudes of the QPOs are
sensitive to the electron distribution function. We argue that transient QPOs
appear at a range of frequencies in the neighborhood of $f_o$ and that the
power spectra, averaged over long times, likely show a broad bump near $f_o$
rather than distinct, narrow QPO features.
View original:
http://arxiv.org/abs/1201.1917
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