A new model for QPOs in accreting black holes: application to the microquasar GRS 1915+105

In this paper we extend the idea suggested previously by Pétri (Astron. Astrophys. 439:L27, 2005a; 443:777, 2005b) (papers I and II) that the high frequency quasi-periodic oscillations (HF-QPOs) observed in low-mass X-ray binaries (LMXBs) may be explained as a resonant oscillation of the accretion disk with a rotating asymmetric background (gravitational or magnetic) field imposed by the compact object. Here, we apply this general idea to black hole binaries. It is assumed that a test particle experiences a similar parametric resonance mechanism such as the one described in paper I and II but now the resonance is induced by the interaction between a spiral density wave in the accretion disk, excited close to the innermost stable circular orbit, and vertical epicyclic oscillations. We use the Kerr spacetime geometry to deduce the characteristic frequencies of this test particle. The response of the test particle is maximal when the frequency ratio of the two strongest resonances is equal to 3:2 as observed in black hole candidates. Finally, applying our model to the microquasar GRS 1915+105, we reproduce the correct value of several HF-QPOs. Indeed the presence of the 168/113/56/42/28 Hz features in the power spectrum time analysis is predicted. Moreover, based only on the two HF-QPO frequencies, our model is able to constrain the mass M BH and angular momentum a BH of the accreting black hole. We show the relation between M BH and a BH for several black hole binaries. For instance, assuming a black hole weakly or mildly rotating, i.e. a BH≤0.5 G M BH/c 2, we find that for GRS 1915+105 its mass satisfies 13 M ⊙≤M BH≤20 M ⊙. The same model applied to two other well-known BHCs gives for GRO J1655-40 a mass 5 M ⊙≤M BH≤7 M ⊙ and for XTE J1550-564 a mass 8 M ⊙≤M BH≤11 M ⊙. This is consistent with other independent estimations of the black hole mass. Finally for H1743-322, we found the following bounds, 9 M ⊙≤M BH≤13 M ⊙.

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