Vol. 551
In section 10. Planets and planetary systems

Do Slivan states exist in the Flora family? II. Fingerprints of the Yarkovsky and YORP effects

by A. Kryszczynska, A&A 551, A102


Asteroids may drift inward or outward depending on their spin direction. This is caused by the slight phase lag between the absorption and reemission of solar irradiation, the so-called Yarkovsky effect. Similarly, they may be spun up or down through the YORP effect. Through the combination of these and a resonance with Saturn, they may find themselves with rotation rates and spin axis orientation clustered around specific values, in a so-called Slivan state. The author examines the results of a detailed survey of the Flora asteroid family (Kryszczynska et al., Paper I) to examine these mechanisms at work. The drift of prograde and retrograde asteroids in different directions is detected for the first time. Furthermore, prograde members of the Flora family appear to be in a Slivan state, contrary to theoretical predictions according to which this could occur only for asteroids in the outer main belt. Further work is therefore needed to understand the orbital evolution of asteroids.