Multi-wavelength spectral study of asteroids in cometary orbits Original Research Article

We present a preliminary analysis of visible + infrared spectra (0.5–2.4 μm) of 17 asteroids in cometary orbits (ACOs), asteroidal objects with Tisserand parameter T < 3. These objects are part of a larger database of ACOs observed with the Italian 3.56 m “Telescopio Nazionale Galileo” and the 2.5 m “Nordic Optical Telescope” at the “El Roque de los Muchachos” Observatory (La Palma, Spain). The sample includes 3 near-Earth objects (NEOs), objects with q ⩽ 1.3 AU, and 14 objects non-NEO ACOs (objects with q > 1.3 AU). The spectra of the 14 non-NEO ACOs are featureless and no low-level differences are found with respect to normal D-type main belt asteroids. The slope distribution of these objects is also indistinguishable from that of Hilda and Trojan asteroids. Two of the three NEOs in cometary orbits present silicate features typical of S and Q-type asteroids. Considering also that a large fraction (∼30%) of the 16 NEOs in cometary orbits observed by Binzel, R., Rivkin, A. Stuart, J., Harris, A., Bus, S., Burbine, T. [Observed spectral properties of near-Earth objects: results for population distribution, source regions, and space weathering processes. Icarus, 170, 259–294, 2004] are S or Q-type, we conclude that this suggests a different origin of the two populations.