Asteroid migration due to the Yarkovsky effect and the distribution of the Eos family

Based on a linearized model of the Yarkovsky effect, we investigate in this paper the dependence of the semimajor axis drift Delta a of a celestial body on its size, spinning obliquity, initial orbit, and thermal parameters on its surface, With appropriate simplification and approximation, we obtain the analytical solutions to the perturbation equations for the motion of asteroids influenced by the Yarkovsky effect, and they are then verified by numerical simulations of the full equations of motion, These solutions present explicitly the dependences of Delta a on the thermal and dynamical parameters of the asteroid. With these analytical formulae for Delta a, we investigate the combined seasonal and diurnal Yarkovsky effects, The critical points where the migration direction reverses are calculated and the consequent selective effects according to the size and rotation state of asteroids are discussed. Finally, we apply the analytical formulae to calculate the migration of Eos family members. The space distribution of asteroids is well reproduced. Our calculations suggest that statistically the orientations of spin axes of family members satisfy a random-obliquity distribution, and the rotation rate omega(rot) of an asteroid depends on its size R by omega(rot) proportional to R-1.