Source to Accretion Disk Tilt：（源吸积盘倾斜）.pdfVIP

Source to Accretion Disk Tilt M.M. Montgomery1 and E. L. Martin1,2 1 Department of Physics, University of Central Florida, Orlando, FL 32816, USA 2 Centro de Astrobiologia CSIC - INTA, Madrid, Spain 0 Abstract 1 0 Many different system types retrogradely precess, and retrograde precession could be from a tidal 2 torque by the secondary on a misaligned accretion disk. However, a source to cause and maintain disk v tilt is unknown. In this work, we show that accretion disks can tilt due to a force called lift. Lift results o from differing gas stream supersonic speeds over and under an accretion disk. Because lift acts at the N disk’s center of pressure, a torque is applied around a rotation axis passing through the disk’s center of 5 mass. The disk responds to lift by pitching around the disk’s line of nodes. If the gas stream flow ebbs, 1 then lift also ebbs and the disk attempts to return to its original orientation. To first approximation, lift does not depend on magnetic fields or radiation sources but does depend ] R on mass and the surface area of the disk. Also, for disk tilt to be initiated, a minimum mass transfer rate S must be exceeded. For example, a 10−11M⊙ disk around a 0.8M⊙ compact central object requires a mass . transfer rate greater than ∼ 10−13M⊙yr−1, a value well below known mass transfer rates in Cataclysmic h Variable Dwarf Novae systems that retrogradely precess and that exhibit negative superhumps in their p - light curves and a value well below mass transfer rates in protostellar forming systems. o r Keywords: accretion, accretion d