Radiation‐Driven Warping: The Origin of Warps and Precession in Accretion Disks

A geometrically thin, optically thick, warped accretion disk with a centralsource of luminosity is subject to non-axisymmetric forces due to radiationpressure; the resulting torque acts to modify the warp. In a recent paper,\cite{pri96} used a local analysis to show that initially planar accretiondisks are unstable to warping driven by radiation torque. Here we extend thiswork with a global analysis of the stable and unstable modes. We confirmPringle's conclusion that thin centrally-illuminated accretion disks aregenerically unstable to warping via this mechanism; we discuss thetime-evolution and likely steady-state of such systems and show specificallythat this mechanism can explain the warping of the disk of water masers in NGC4258 and the 164-day precession period of the accretion disk in SS 433.Radiation-driven warping and precession provides a robust mechanism forproducing warped, precessing accretion disks in active galactic nuclei andX-ray binary systems.Comment: 16 pages, latex, 3 figure