The spectroscopic properties of the Lixiaohua family, cradle of Main Belt Comets

Abstract The Lixiaohua collisional family lies in the Outer Main Belt, close to the well characterized Themis primitive class family. It is one of the only three families that host two active asteroids that present cometary-like activity: 313P/Gibbs and 358P/PANSTARRS (P/2012 T1). As a part of the PRIMitive Asteroid Spectroscopy Survey (PRIMASS), we present the results of a spectroscopic program where we acquired 36 objects in visible wavelengths, using the 4.1 m SOAR, and, 17 objects in the near-infrared, using the 3.58 m Telescopio Nazionale Galileo, which provided the characterization of 43 out of the 756 identified Lixiaohua family members. We observed asteroids members of the Lixiaohua family with the aim of: (1) determining the spectral class and spectroscopic properties of the family, (2) estimating the presence of hydrated minerals on their surfaces by studying the 0.7  μ m absorption band and the UV drop of reflectance below 0.5  μ m, (3) analyzing if active asteroids 358P and 313P are probable family members. Our results show that the Lixiaohua family is consistently redder families than the Themis family and present a wide variety of slopes. We have not found an unambiguous trace of aqueous alteration in the spectra of the family members, at the observed wavelengths. Finally, we conclude that the Lixiaohua family is the probable source of the Main-Belt Comets 313P/Gibbs and 358P/PANSTARRS.