Physical properties of CAI-rich asteroids

Abstract:

Some L-type asteroids (collectively called "Barbarians") are known to exhibit an anomalous polarimetric behavior, whose origin - still to be elucidated - can be related to compositional and/or scattering effects. The fact that these asteroids belong to the same taxonomic class (following the De Meo 2009 classification, including NIR) implies that composition must play a role. Sunshine et al. 2008 showed that these asteroids contain high amounts of CAIs, possibly hinting to a formation in an early proto-planetary environment, very rich in refractory material. On the base of this evidence, we started an observational campaign to increase the data coverage of these objects, by obtaining new NIR spectra, photometric and polarimetric measurements. Our first results show that the peculiar features are not restricted to polarimetry. In particular we show the existence of an anomalous distribution of the rotation periods, and a possible relation between CAI abundance and albedos determined by WISE. We tentatively discuss a possible scenario justifying the different observed features.