BVRI photometry of 53 unusual asteroids

We present the results of BVRI photometry and classification of 53 unusual asteroids, including 35 near-Earth asteroids (NEAs), 6 high eccentricity/ inclination asteroids, and 12 recently identified asteroid-pair candidates. Most of these asteroids were not classified prior to this work. For the few asteroids that have been previously studied, the results are generally in agreement. In addition to observing and classifying these objects, we merge the results from severalphotometric/spectroscopic surveys to create the largest-ever sample with 449 spectrally classified NEAs for statistical analysis. We identify a "transition point" of the relative number of C/X-like and S-like NEAs at H ∼ 18 ⇔ D ∼ 1 km with confidence level at ∼95% or higher. We find that the C/X-like:S-like ratio for 18 ≤ H < 22 is about twice as high as that of H < 18 (0.33±0.04 versus 0.17 ± 0.02), virtually supporting the hypothesis that smaller NEAs generally have less weathered surfaces (therefore less reddish appearance) due to younger collision ages.© 2011. The American Astronomical Society.