Lightcurve observation of small main-belt asteroids

Abstract

Fast Rotating Asteroids (FRAs) which are rotating faster than 2.2 hours or less exist in the group of Near Earth Asteroids (NEAs). Since NEAs originate from MBAs, some of MBAs could be FRAs. However, FRAs have not been discovered in the group of Main-Belt Asteorids (MBAs). It would be because of difficulty of the detection of MBAs less than 1 km in diameter , such dominate in the NEAs population. So, we used the large telescope, 8.2m Subaru telescope, and detected many small MBAs such as having apparent magnitude of 17-25 mag and then examined their lightcurves for searching FRAs in MBAs. As a result, we found the possibility that the MBAs of 20 percent or more are FRAs.