Tumbling asteroid rotation with the YORP torque and inelastic energy dissipation

Abstract

The Yarkovsky–O'Keefe–Radzievskii–Paddack (YORP) effect and rotational energy dissipation due to inelastic deformations are two key mechanisms affecting rotation of tumbling asteroids in long term. Each of the effects used to be discussed separately. We present the first results concerning a simulation of their joint action. Asteroids (3103) Eger and (99942) Apophis, as well as their scaled variants, are used as test bodies. Plugging in the dissipation destroys limit cycles of the pure YORP, but creates a new asymptotic state of stationary tumbling with a fixed rotation period. The present model does not contradict finding Eger in the principal axis rotation. For Apophis, the model suggests that its current rotation state should be relatively young. In general, the fraction of initial conditions leading to the principal axis rotation is too small, compared to the actual data. The model requires a stronger energy dissipation and weaker YORP components in the nutation angle and obliquity.