Shock oscillation model for quasi-periodic oscillations in stellar mass and supermassive black holes

We numerically examine centrifugally supported shock waves in 2D rotating accretion flows around a stellar mass (10 M) and a supermassive (106 M) black holes over a wide range of input accretion rates of 107 M˙ /M˙ E 10−4. The resultant 2D shocks are unstable with time and the luminosities show quasi-periodic oscillations (QPOs) with modulations of a factor of 2–3 and with periods of a tenth of a second to several hours, depending on the black hole masses. The shock oscillation model may explain the intermediate frequency QPOs with 1– 10 Hz observed in the stellar mass black hole candidates and also suggest the existence of QPOs with the period of hours in active galactic nuclei. When the accretion rate M˙ is low, the luminosity increases in proportion to the accretion rate. However, when M˙ greatly exceeds the Eddington critical rate M˙ E, the luminosity is insensitive to the accretion rate and is kept constantly around ∼3LE. On the other hand, the mass-outflow rate M˙ loss increases in proportion to M˙ and it amounts to about a few per cent of the input mass-flow rate