Ken B. Henisey et al. 2009 ApJ 706 705 doi:10.1088/0004-637X/706/1/705
Ken B. Henisey1, Omer M. Blaes1, P. Chris Fragile2 and Bárbara T. Ferreira3
Show affiliationsWe analyze the time dependence of fluid variables in general relativistic, magnetohydrodynamic simulations of accretion flows onto a black hole with dimensionless spin parameter a/M = 0.9. We consider both the cases where the angular momentum of the accretion material is aligned with the black hole spin axis (an untilted flow) and where it is misaligned by 15° (a tilted flow). In comparison to the untilted simulation, the tilted simulation exhibits a clear excess of inertial variability, that is, variability at frequencies below the local radial epicyclic frequency. We further study the radial structure of this inertial-like power by focusing on a radially extended band at 118(M/10 M ☉)–1 Hz found in each of the three analyzed fluid variables. The three-dimensional density structure at this frequency suggests that the power is a composite oscillation whose dominant components are an over dense clump corotating with the background flow, a low-order inertial wave, and a low-order inertial-acoustic wave. Our results provide preliminary confirmation of earlier suggestions that disk tilt can be an important excitation mechanism for inertial waves.
accretion, accretion disks; black hole physics; MHD; turbulence; waves; X-rays: binaries
Issue 1 (2009 November 20)
Received 2009 May 6, accepted for publication 2009 October 13
Published 2009 November 4
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