Publication date: Dec 2004
In all four microquasars which show twin peak kHz QPOs, the ratio of the
two frequencies is 3:2. This rather strongly supports the suggestion by
Abramowicz, M. A. and Kluzniak [W. Abramowicz, M. A. and Kluzniak, W.,
(2001). A precise determination of black hole spin in GRO J1655-40.
Astronomy and Astrophysics, 374:L19] that twin peak kHz QPOs are due to
a resonance between some modes of accretion disk oscillations. Detailed
studies of this suggestion revealed that several such non-linear
resonances are present in nearly Keplerian disks in strong gravity.
Here, we fit to observations predictions of the resonance hypothesis for
two particular types of non-linear resonances between vertical and
radial epicyclic frequencies. For three microquasars with known masses,
the fits give an accurate estimate of the spin.
Abramowicz, Marek A.; Kluzniak, Włodek; Stuchlík, Zdeněk; Török, Gabriel;