Influence of Non-geodesic Effects on Black Hole Spin Estimations Obtained from QPO Models

One of the popular ways for obtaining estimations of black hole spin is a method related to models for high-frequency quasi-periodic oscillations (QPOs). In the past, estimations for three microquasars GRS 1915+105, GRO J1655-40, and XTE J1550-564 were carried out based on several QPO models assuming a geodesic accretion flow. In this work we assume a non-geodesic accretion flow described by the model of a pressure-supported perfect fluid torus and explore the influence of the pressure forces on the spin predictions calculated for the geodesic flow. Our results indicate that in some cases, e.g. for the so-called "vertical precession resonance" model, the presence of pressure forces may have a major influence on the predicted ranges of spin. On the other hand, in other cases, e.g. for the so-called "Keplerian resonance" model, the predicted "non-geodesic" spin intervals do not much vary from those corresponding to geodesic calculations.