Journal
ASTRONOMY & ASTROPHYSICS
Volume 531, Issue -, Pages -Publisher
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201015549
Keywords
X-rays: binaries; black hole physics; accretion, accretion disks
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Funding
- SU Opava [MSM 478130590, GACR 202/09/0772, LC 06014]
- FPF [SGS/1,2/2010]
- Swedish Research Council
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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 concequences for 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 most of the discussed geodesic 3:2 QPO models. To explain the observations of all the three microquasars by one unique mechanism, the models would have to accommodate very large non-geodesic corrections.
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