Publication date: Apr 2013
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.
Kovar, Jiri; Sramkova, E.; Torok, G.; Bakala, P.; Stuchlik, Z.;