Veritas Asteroid Family: Remarkable Spectral Differences Inside a Primitive Parent Body

Abstract

In this paper we report first optical reflectance spectra in the wavelength range 3800–9000 Å for seven members of the Veritas asteroid family, as determined by V. Zappalà, A. Cellino, P. Farinella, and A. Milani (1994, Astron. J.116, 291–314). The observed asteroids are 490 Veritas, 844 Leontina, 1086 Nata, 2428 Kamenyar, 2934 Aristophanes, 5592 Oshima, and 1985 TQ 1. In addition, we also observed the object 5107 1987 DS 6, which joins the Veritas family when a slightly more relaxed criterion of selection is adopted. The obtained spectra show a surprising slope gradient spanning from 0 to about 8%, a range that includes the slopes characteristics of all the low-albedo, primitive bodies (from C to D type). Taking into account the very compact structure of the family—the probability of finding interlopers inside the defined clustering is practically zero—this result seems to confirm the suggestion by F. Vilas and M. V. Sykes (1996, Icarus,124, 483–489) about the presence of thermally altered large asteroids inside the outer belt population; however, the hypothesis of possible space weathering processes cannot be completely ruled out. A tentative representation of the postimpact velocity field has been also obtained, showing a possible peculiar ejection of the fragments.