Icarus 149, 190–197 (2001) doi:10.1006/icar.2000.6507, available online at http://www.idealibrary.com on A Study of Cybele Asteroids I. Spin Properties of Ten Asteroids Claes-Ingvar Lagerkvist Astronomical Observatory, Box 515, S-751 20 Uppsala, Sweden E-mail: classe@astro.uu.se Anders Erikson DLR, Institute of Space Sensor Technology and Planetary Exploration, Rutherfordstrasse 2, D-12489 Berlin, Germany Felix Lahulla Observatorio Astronomico, Alfonso XII 3, 28014 Madrid, Spain Mario De Martino Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy Andreas Nathues DLR, Institute of Space Sensor Technology and Planetary Exploration, Rutherfordstrasse 2, D-12489 Berlin, Germany and Mats Dahlgren Astronomical Observatory, Box 515, S-751 20 Uppsala, Sweden Received January 3, 2000; revised June 14, 2000 As a part of an observational program on Cybele asteroids we have obtained lightcurves of 10 of the largerasteroids. In this paper the results are presented for229 Adelinda, 260 Huberta, 401 Ottilia, 420 Bertholda, 466 Tisiphone, 522 Helga, 570 Kythera, 713 Lus- cinia, 909 Ulla, and 1467 Mashona. Spin properties have been de- termined forthe first time for8 of these asteroids. c  2001 Academic Press 1. INTRODUCTION One of the main objectives in studying asteroids is that they are considered more primitive than the major planets and with composition, size, and other physical properties similar to the planetesimal population from which the planets grew. Since their formation, main belt asteroids (MBA) have undergone an evo- lution due to mutual collisions, which have altered their original physical parameters (spin properties, shape, mass distribution, composition, etc.) and led to the formation of the dynamical families and dust bands, the insertion of meteorites and small asteroids into inner planet-crossing orbits, and the generation of a variety of collisional outcomes (e.g., “rubble-pile” asteroids and binary systems). There is an obvious variation of surface composition with heliocentric distance in the main asteroid belt (Gradie and Tedesco 1982) indicative of evolutionary differ- ences between different regions of the belt. The Cybele, Hilda, and Trojan asteroids are all bodies moving outside the main asteroid belt with semi-major axes a ≥ 3.3 AU. The Cybele asteroids have 3.3 AU ≤ a ≤ 3.6 AU, the Hilda asteroids are found in the 3 : 2 mean motion resonance with Jupiter with a = 4.0 AU, and the two Trojan clouds are found around the Jupiter Lagrangian points L 4 and L 5 . Many of these outer belt asteroids (OBA) have red, dark sur- faces and their spectra show a reddening in the spectral slope with heliocentric distance which implies a change in surface composition. The major taxonomic types found among the dis- tant asteroids are quite rare in the main belt and are currently unrepresented in terrestrial meteorite collections. The OBA may therefore represent a transition region between typical MBA and the comets. Considering this, OBA may yield clues about the physical nature of the planetesimals and provide a reference 190 0019-1035/01 $35.00 Copyright c  2001 by Academic Press All rights of reproduction in any form reserved.