A study of Cybele asteroids II: Optical spectra.

Abstract

We present low-resolution reflectance spectra in the wavelength range 400 to 860 nm of 19 Cybele asteroids. The observed asteroids cover a large range of diameters between 30 und 150 km, with focus on smaller sizes. The spectra were obtained during two nights in 1996 at the 3.5m ESO NTT (La Silla, Chile). The spectra identify most asteroids as D-types and a minor part as P-types. A considerable fraction of the observed asteroids belongs to the intermediate PD- and DP-types. No evidenve of absorption features was found in the spectra of the P- and D-type astoids. The asteroid 3675 Kemstach was identified as a possible S-type, due to a steep slope (12%/100 nm) for wavelengths shorter than 740 nm and a beginning absorption band behind 760 nm.