Shock oscillation model for QPOs in stellar-mass and supermassive black holes

Abstract

We numerically examine centrifugally supported shock waves in 2D rotating accretion flows around a stellar-mass (10M_sun) and a supermassive (10^6M_sun) black holes over a wide range of input accretion rates of 10^7 >\dot M/\dot 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 andwith periods of a tenth seconds 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 AGNs. When the accretion rate is low, the luminosity increases in proportion to the accretion rate. However, when the accretion rate exceeds greatly the Eddington critical rate \dot M_E, the luminosity is insensitive to the accretion rate and is kept constantly around 3 L_E. On the other hand, the mass-outflow rate increases in proportion to the accretion rate and it amounts to about a few percent of theinput mass-flow rate.