出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：Kilohertz Quasi-Periodic Oscillations (QPOs) have been detected in many accreting X-ray binaries.
It has been suggested that the kHz QPO frequencies observed in the modulation of the
X-ray flux reflect a non-linear resonance between two modes of accreting disk oscillations. A 3:2
resonant ratio of frequencies has been clearly recognized in the black-hole QPO data supporting
the non-linear resonance hypothesis. It is often discussed whether the same 3:2 ratio appears in
case of the neutron star QPOs as well. For an individual neutron star source, the relation between
the observed lower and upper (nL and nU) kHz QPO frequency is well approximated by a linear
relation with the slope A and the shift B, i.e., nU = AnL +B. It was recognized only recently that
for a group of twelve neutron star sources the value of the individual coefficients A,B is anticorrelated,
obeying the condition A = 3/2 − 0.0016B. It was also shown that such an anticorrelation is
predicted by the theory of weakly coupled nonlinear oscillators, and one can argue that it indeed
pose the evidence for a 3:2 resonant ratio. Here, stressing the latest progress, we discuss some of
the links between the QPO observation and the resonance model, and summarize the appropriate
references.
Except the slightly updated list of references, the content of next four pages fully correspond to
the A0 poster we exhibited at the VI Microquasar Workshop. The poster itself is available at the
http://www.physics.cz/research (section Conferences).
