Dark asteroids exhibiting intermediate characteristics between C and X typesOPEN ACCESS
Sunao Hasegawa, Chrysa Avdellidou, Michael Marsset, Ullas Bhat, Marco Delbo, Daisuke Kuroda, Moe Matsuoka, Masateru Ishiguro, Cristina A. Thomas, Francesca E. DeMeo, Pierre Vernazza
Accepted for publication in MNRAS (Letters)
“Large main-belt asteroids with visible geometric albedos below 0.1 are predominantly classified within the C- and X-complex spectroscopic classes. C-type and dark X-type asteroids typically exhibit flat to slightly negative and positive spectral slopes, respectively. They are further distinguished by the presence (for C-types) or absence (for dark X-types) of a shallow absorption feature near 1.0-1.3 micron. We serendipitously discovered that the asteroids 1093 Freda and 1390 Abastumani display spectral characteristics intermediate between these two classes, combining a positive visible-to-near-infrared spectral slope with a shallow absorption band. A search in the literature reveals additional asteroids with similar properties. The existence of such objects, spanning a continuum of spectral shapes between C- and dark X-types, may point to a common genetic origin. Their spectral behavior could be explained by the presence of cronstedtite, an Fe-rich serpentine, on their surfaces.”
