Photometric survey of the very small near-Earth asteroids with the SALT telescope II. Discussion of YORP

Abstract

Aims: A possibility of detection of the YORP effect in the population of the very small near-Earth asteroids is discussed. It is probable that due to their significant thermal conductivity, those of the objects which are on low inclination orbits experience a continuous spin-up/spin-down without the typical YORP cycles, and their spin axes are moved towards obliquities of 0° and 180°. Methods: For all rapidly rotating near-Earth asteroids observed with SALT, as well as other such objects for which periods are known, future observing possibilities are identified. A statistically derived, approximate relation for the YORP spin-up/spin-down is then utilized to check which of the considered asteroids can be potentially used to detect this effect. Results :It was found that for two asteroids, 2000 HB24 (if successfully recovered in 2014) and 1998 KY26, rotation period changes due to YORP should be detectable in the future. A determination of obliquities of two other objects, 2001 AV43 and 2006 XY should also be possible. For the latter constraints on its pole position are obtained suggesting a prograde rotation and the spin axis obliquity ε ≤ 50°. © 2010 ESO.