ANALYSIS OF THE ROTATIONAL PROPERTIES OF KUIPER BELT OBJECTS

We use optical data on 10 Kuiper Belt objects (KBOs) to investigate their rotational properties. Of the 10, 3 (30%) exhibit light variations with amplitude (delta) m => 0.15 mag, and 1 out of 10 (10%) has (delta)m => 0.40 mag, which is in good agreement with previous surveys. These data, in combination with the existing database, are used to discuss the rotational periods, shapes, and densities of KBOs. We find that, in the sampled size range, KBOs have a higher fraction of low-amplitude light curves and rotate slower than main-belt asteroids. The data also show that the rotational properties and the shapes of KBOs depend on size. If we split the database of KBO rotational properties into two size ranges with diameters larger and smaller than 400 km, we find that (1) the mean light-curve amplitudes of the two groups are different with 98.5% confidence, (2) the corresponding power-law shape distributions seem to be different, although the existing data are too sparse to render this difference significant, and (3) the two groups occupy different regions on a spin period–versus–light-curve amplitude diagram. These differences are interpreted in the context of KBO collisional evolution.