Open AccessOscillation modes of relativistic slender tori
Author(s) -
Blaes O. M.,
Arras P.,
Fragile P. C.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.10370.x
Subject(s) - physics , angular momentum , polytropic process , specific relative angular momentum , torus , oscillation (cell signaling) , classical mechanics , rotational symmetry , instability , accretion (finance) , astrophysics , total angular momentum quantum number , mechanics , angular momentum coupling , geometry , mathematics , biology , genetics
Accretion flows with pressure gradients permit the existence of standing waves which may be responsible for observed quasi‐periodic oscillations (QPO's) in X‐ray binaries. We present a comprehensive treatment of the linear modes of a hydrodynamic, non‐self‐gravitating, polytropic slender torus, with arbitrary specific angular momentum distribution, orbiting in an arbitrary axisymmetric space–time with reflection symmetry. We discuss the physical nature of the modes, present general analytic expressions and illustrations for those which are low order, and show that they can be excited in numerical simulations of relativistic tori. The mode oscillation spectrum simplifies dramatically for near Keplerian angular momentum distributions, which appear to be generic in global simulations of the magnetorotational instability. We discuss our results in light of observations of high frequency QPO's, and point out the existence of a new pair of modes which can be in an approximate 3:2 ratio for arbitrary black hole spins and angular momentum distributions, provided the torus is radiation pressure dominated. This mode pair consists of the axisymmetric vertical epicyclic mode and the lowest order axisymmetric breathing mode.