Quasi-periodic inward shock formation from an accretion disk to a black hole and its application to quasi-periodic oscillations in microquasars

We performed 1.5D general relativistic simulations using a Kerr metric without disk viscosity for a model of high frequency quasi-periodic oscillations (QPOs) in microquasars. We found that quasi-periodic inward shock waves propagate from the accretion disk toward the black hole when we initially inject a disturbance into the disk. The frequency of the shock formation is approximately equal to the maximum epicyclic frequency in the disk (kappa(max)) which is on the order of the frequency of high frequency QPOs in microquasars. kappa(max) depends on the rotation of the black hole, and therefore we can estimate the value of the spin parameter of a black hole candidate (BHC) in a microquasar by comparing the high frequency QPO with kappa(max). We found that such values can be roughly estimated as 0.0 less than or equal to a < 0.4 for GRS 1915+105 and 0.85 < a < 1.0 for GRO J1655-40.