Volumes and bulk densities of forty asteroids from ADAM shape modeling

¹ Centre National d’Études Spatiales, 2 place Maurice Quentin, 75039 Paris Cedex 01, France
e-mail: hanus.home@gmail.com
² Université Côte d’Azur, OCA, CNRS, Lagrange, France
³ Astronomical Institute, Faculty of Mathematics and Physics, Charles University, V Holešovičkách 2, 18000 Prague, Czech Republic
⁴ Department of Mathematics, Tampere University of Technology, PO Box 553, 33101 Tampere, Finland
⁵ SETI Institute, Carl Sagan Center, 189 Bernado Avenue, Mountain View, CA 94043, USA
⁶ RASNZ Occultation Section, 3 Lupin Pl., Murrumbateman, NSW 2582, Australia
⁷ Euraster, 8 route de Soulomes, 46240 Labastide-Murat, France
⁸ JOIN/Japan Occultation Infomation Network, 891-0141 Kagoshima, Japan
⁹ International Occultation Timing Association (IOTA), %SK, SP, BT, DD  
¹⁰ RASNZ Occultation Section, 3 Hughes Street, Waikanae Beach, 5036 Kapiti Coast, New Zealand

Received: 25 October 2016
Accepted: 6 February 2017

Abstract

Context. Disk-integrated photometric data of asteroids do not contain accurate information on shape details or size scale. Additional data such as disk-resolved images or stellar occultation measurements further constrain asteroid shapes and allow size estimates.

Aims. We aim to use all the available disk-resolved images of approximately forty asteroids obtained by the Near-InfraRed Camera (Nirc2) mounted on the W.M. Keck II telescope together with the disk-integrated photometry and stellar occultation measurements to determine their volumes. We can then use the volume, in combination with the known mass, to derive the bulk density.

Methods. We downloaded and processed all the asteroid disk-resolved images obtained by the Nirc2 that are available in the Keck Observatory Archive (KOA). We combined optical disk-integrated data and stellar occultation profiles with the disk-resolved images and use the All-Data Asteroid Modeling (ADAM) algorithm for the shape and size modeling. Our approach provides constraints on the expected uncertainty in the volume and size as well.

Results. We present shape models and volume for 41 asteroids. For 35 of these asteroids, the knowledge of their mass estimates from the literature allowed us to derive their bulk densities. We see a clear trend of lower bulk densities for primitive objects (C-complex) and higher bulk densities for S-complex asteroids. The range of densities in the X-complex is large, suggesting various compositions. We also identified a few objects with rather peculiar bulk densities, which is likely a hint of their poor mass estimates. Asteroid masses determined from the Gaia astrometric observations should further refine most of the density estimates.