Mutual Orbits, Size, Density, and Interior of Visualized Multiple Asteroids

Since 2001 our team collected Adaptive Optics Observations of high-size ratio multiple asteroids (e.g. 22 Kalliope, 130 Elektra, 624 Hektor) and large similarly-sized binary asteroids (90 Antiope, 617 Patroclus) using 8-10m class telescopes such as Gemini North, VLT-UT4, and W.M. Keck II telescopes and archive data from HST. Using a new genetic-based algorithm, named GENOID (Vachier et al. 2012), we derived the orbital parameters of ~16 multiple asteroids, including 13 main-belt asteroids, 2 Jupiter-trojan asteroids and one Transneptunian asteroid. This efficient algorithm allows us to explore a wide range or orbital solutions without any a priori constrain on the system. Two types of dynamical models, one purely Keplerian and a dynamical one (which fits as well the size and J2/J4 of the primary) can be used. In the last case, we can also infer the distribution of material in the primary. The volume of these asteroids is derived by combining mid-IR observations from Spitzer/IRS, IRAS, WISE or AKARI with lightcurve inversion technique and stellar occultations. The bulk density derived for these asteroids confirmed a relationship between their taxonomic classes and their composition with an average density of ~3.5 g/cc for M-type asteroids, ~1 g/cc for C/P/D-type and ~2 g/cc for S-type. We will present an overview of our analysis emphasizing the most recent results in particular the size, shape and internal structure of (624) Hektor. We will also discuss new directions of investigations using more performant AO systems soon available on 8-10m class telescopes. More accessible multi-user campaigns to observe stellar occultation and also mutual event between the components of the systems aiming at refining the size & shape of the primary and the size of the satellite(s) will be described. GENOID algorithm provides orbital solution directly implemented in the IMCCE ephemerides allowing the predictions of these events and the position of the satellite(s).