Roman V. Shcherbakov, Jonathan C. McKinney
High-frequency quasi-periodic oscillations (QPOs) appear in general-relativistic magnetohydrodynamic simulations of magnetically choked accretion flows around rapidly rotating black holes (BHs). We perform polarized radiative transfer calculations with our ASTRORAY code in order to explore the manifestations of these QPOs for Sgr A*. We construct a simulation-based model of a radiatively inefficient accretion flow and find model parameters by fitting the mean observed polarized source spectrum. The simulated QPOs have a total sub-mm flux amplitude of under 5% and a linearly polarized flux amplitude of up to 2%. The oscillation period $T\approx100M\approx35$ min corresponds to the rotation period of the BH magnetosphere that produces a trailing spiral in resolved disk images. The total flux signal is statistically significant over noise for all tested frequencies 87 GHz, 230 GHz, and 857 GHz and inclination angles $10^\circ,$ $37^\circ,$ and $80^\circ$. The non-detection in the 230 GHz Sub-Millimeter Array light curve is consistent with a low signal level and low sampling rate. The possible presence of such magnetospheric QPOs in Sgr A* will be better tested with Atacama Large Millimeter Array.
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http://arxiv.org/abs/1304.7768
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