Publication date: n/a 2008
Abstract:
Using known frequencies of the accretion disc twin peak quasiperiodic
oscillations (QPOs) and the known mass of the central black hole, the
black hole dimensionless spin a can be determined, assuming a concrete
version of the orbital resonance model. However, because of large range
of observationally limited values of the black holemass, its spin can be
estimated with a low precision only. Higher precision of the black hole
spin measurement is possible in the framework of multi-resonance model
of QPOs inspired by complex high-frequency QPO patterns observed in some
black hole and neutron star systems. In the simple orbital resonance
models we determine the spin and mass dependence of the twin peak
frequencies for non-linear resonances of oscillations with the epicyclic
and Keplerian frequencies or their combinations in the case of a general
rational frequency ratio n : m, n ˜ m. In the multi-resonant
model, the twin peak resonances are combined properly to give the
observed frequency set. The multiresonant model is proposed in three
distinct versions. In the first one, related probably to the neutron
star binary systems, more instances of one resonance occur at more
specific radii. In the second case, more resonances are sharing one
specific radius, allowing for "cooperative" resonant phenomena in the
field of black holes with a specific value of spin. In the third
("ugly") case, more resonances occur at more specific radii; we restrict
our attention to the case of two such resonant radii. For special values
of the spin, only triple-set of frequencies is observed because of
coincidence of some frequencies, allowing determination of the spin from
the triple frequency ratio set. The spin is determined precisely, but
not uniquely as the same frequency set could be relevant formore than
one concrete spin and combination of resonant oscillations.
Authors:
Stuchlik, Zdenek; Kotrlova, Andrea; Török, Gabriel;