Podrobný výpis o publikaci

Spectral fitting of the spin a = cJ/GM(2) in the microquasar GRS 1915+105 estimate values higher than a = 0.98. However, there are certain doubts about this (nearly) extremal number. Confirming a high value of a > 0.9 would have significant concequencesfor the theory of high-frequency quasiperiodic oscillations (HF QPOs). Here we discuss its possible implications assuming several commonly used orbital models of 3: 2 HF QPOs. We show that the estimate of a > 0.9 is almost inconsistent with two hot-spot(relativistic precession and tidal disruption) models and the warped disc resonance model. In contrast, we demonstrate that the epicyclic resonance and discoseismic models assuming the c-and g-modes are favoured. We extend our discussion to another two microquasars that display the 3: 2 HF QPOs. The frequencies of these QPOs scale roughly inversely to the microquasar masses, and the differences in the individual spins, such as a = 0.9 compared to a = 0.7, represent a generic problem for