MG11 
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QPOs due to Centrifugally Supported Shocks around Stellar-Mass and Supermassive Black Holes

We examine centrifugally supported shocks formed in low-angular momentum accretion flows around stellar-mass and supermassive black holes, by 2D-hydrodynamical calculations, while taking account of the cooling and heating of the gas and the radiation transport. With a set of adequate injection parameters, shock waves appear at 5-20 Schwartzschild radii. However, the radiative shocks are unstable with time and oscillate quasi-periodically around the above shock position. The resultant luminosities behave as the quasi-periodic oscillations (QPOs) with modulations of a factor 3 and with quasi-periods of a tenth seconds to several hours, depending on the black hole masses. These shock-oscillation models may not only explain the intermediate frequency QPO with 1–10 Hz observed in the black hole candidate GRS 1915+105 but also suggest the existence of QPOs with the period of hours in AGNs.