Earth, Moon, Sun, and Cv Accretion Disks

Abstract

Net tidal torque by the secondary on a misaligned accretion disk, like the net tidal torque by the Moon and the Sun on the equatorial bulge of the spinning and tilted Earth, is suggested by others to be a source to retrograde precession in non-magnetic, accreting Cataclysmic Variable (CV) Dwarf Novae systems that show negative superhumps in their light curves. We investigate this idea in this work.We generate a generic theoretical expression for retrograde precession in spinning disks that are misaligned with the orbital plane. Our generic theoretical expression matches that which describes the retrograde precession of Earths' equinoxes. By making appropriate assumptions, we reduce our generic theoretical expression to those generated by others, or to those used by others, to describe retrograde precession in protostellar, protoplanetary, X-ray binary, non-magnetic CV DN, quasar and black hole systems.We find that spinning, tilted CV DN systems cannot be described by a precessing ring or by a precessing rigid disk. We find that differential rotation and effects on the disk by the accretion stream must be addressed. Our analysis indicates that the best description of a retrogradely precessing spinning, tilted, CV DN accretion disk is a differentially rotating, tilted disk with an attached rotating, tilted ring located near the innermost disk annuli. In agreement with observations and numerical simulations by others, we find that our numerically simulated CV DN accretion disks retrogradely precess as a unit. Our final, reduced expression for retrograde precession agrees well with our numerical simulation results and with selective observational systems that seem to have main sequence secondaries.Our results suggest that a major source to retrograde precession is tidal torques like that by the Moon and the Sun on the Earth. In addition, these tidal torques should be common to a variety of systems where one member is spinning and tilted, regardless if accretion disks are present or not. Our results suggest that the accretion disk's geometric shape directly affects the disk's precession rate.

Tilt, Warp, and Simultaneous Precessions in Disks

“…The two waves are asymmetric. When compared with the control group of artificially tilted disks (Montgomery 2009b), the nodal superhump fundamental and higher-order harmonic frequencies (see Table 1 for this simulations' values) agree within the uncertainties. However, the amplitude of the signals do not agree, indicating that the disk tilt in this simulation is less than 4…”

Brown dwarfs in retrogradely precessing cataclysmic variables?

“…We use the numerical simulation results presented in Montgomery [2] for non-magnetic CV retrogradely precessing tilted spinning accretion disks that have 0.8 solar mass primaries and secondary-to-primary mass ratios within the range 0.35-0.55. The secondary stars are assigned masses above the upper brown dwarf mass limit and are main sequence stars.…”

“…The secondary stars are assigned masses above the upper brown dwarf mass limit and are main sequence stars. We use theory on retrograde precession of accretion disks [1,2]. The dash-dot line and the dash line could explain the majority of CV DN systems if we assume that the secondary ahs lost half its mass and three-fourth its mass, respectively.…”

“…presented in Montgomery [1] that is based on the retrograde precession of Earth via tidal torques by the Moon and the Sun. The observational data used in comparisons with the numerical simulations and with the theory is given in Montgomery [1,2].…”

“…In Figure 1, the observational data (stars) and theory (solid line) for white dwarf primaries with main sequence secondary stars are from Montgomery [2]. The numerical simulations (triangles) are from Montgomery [1].…”