Extended orbital resonance model with humpinduced oscillations
Abstract
Change of sign of the LNRFvelocity gradient has been found for accretion discs orbiting rapidly rotating Kerr black holes with spin a > 0.9953 for Keplerian discs and a > 0.99979 for marginally stable thick discs. Such a "humpy" LNRFvelocity profiles occur just above the marginally stable circular geodesic and could be related to oscillations of accretion discs. The frequency of such "hump"induced oscillations can be identified with the maximal rate of change of the orbital velocity within the "humpy" profile. Therefore, we introduce an extended orbital resonance model (EXORM) of quasiperiodic oscillations (QPOs) assuming nonlinear resonant phenomena between oscillations with the orbital epicyclic frequencies and the humpy frequency defined in a fully general relativistic way. The EXORM is developed for both Keplerian discs and perfectfluid tori where the approximation of oscillations with epicyclic frequencies is acceptable. Clearly, the EXORM could be applied to the nearextreme Kerr black hole systems exhibiting relatively complex QPO frequency patterns. Assuming a Keplerian disc, it can be shown that in the framework of the EXORM, all the QPOs observed in the microquasar GRS 1915+105 could be explained, while it is not possible in the case of QPOs observed in the Galactic Centre source Sgr A*.
 Publication:

RAGtime 8/9: Workshops on Black Holes and Neutron Stars
 Pub Date:
 December 2007
 Bibcode:
 2007ragt.meet..449S
 Keywords:

 black hole physics;
 accretion;
 accretion disks;
 relativity