Main belt binary asteroidal systems with eccentric mutual orbits

Abstract

ABSTRACTanother S-type asteroid, and should be poorly fractured as well. (379) Huenna seems to display both characteristics: the moonlet orbits far away from the primary in term of stability (20% × R Hill ), but the primary's porosity is significant (30-60%).

Determination of binary asteroid orbits with a genetic-based algorithm

“…Its first satellite was discovered in 2002 using an AO system mounted on the Gemini North telescope. Marchis et al (2008a) attempted to derive the orbital parameters of this 2-km satellite diameter and found a solution with the satellite describing a highly eccentric orbit (e ∼ 0.9 and a ∼ 290 km) around the primary in 60−70 days. More recently, a careful photometric analysis of the lightcurves of Balam suggested that the primary of the system is in fact composed of two components with 6 and 2 km diameters orbiting at 20 km (Marchis et al 2008b).…”

“…More recently, a careful photometric analysis of the lightcurves of Balam suggested that the primary of the system is in fact composed of two components with 6 and 2 km diameters orbiting at 20 km (Marchis et al 2008b). We know that Marchis et al (2008a) solution is flawed since they attempted to fit the position of the satellite when it was closer to its primary, confusing the outer and the inner moon position (the inner moon was unknown at the time of this analysis). Additionally, recently published observations of the triple system in the mid-infrared with Spitzer/IRS by Enriquez et al (2010) were used to derive the equivalent size D eq = 4.68 ± 0.54 km, leading to an unrealistic average density of 8 g/cm 3 based on the orbital solution of Marchis et al (2008a).…”

“…We know that Marchis et al (2008a) solution is flawed since they attempted to fit the position of the satellite when it was closer to its primary, confusing the outer and the inner moon position (the inner moon was unknown at the time of this analysis). Additionally, recently published observations of the triple system in the mid-infrared with Spitzer/IRS by Enriquez et al (2010) were used to derive the equivalent size D eq = 4.68 ± 0.54 km, leading to an unrealistic average density of 8 g/cm 3 based on the orbital solution of Marchis et al (2008a). Vokrouhlický (2009) showed that Balam is a very young system with an age estimated to less than a million years old.…”

“…The green orbit is an intermediate case with J 2 = 0.15. this case we have significantly fewer observations, distributed over 17 months and corresponding to 4−13 periods of revolution. We used the astrometric positions from Marchis et al (2008a), after having removed the astrometric positions which may be related to a marginal detection of the inner satellite. Using Genoid-Kepler we derived a bundle of 10 solutions with Fig.…”

“…From the periods and semi-major axes of the mutual orbits, we derived the corresponding masses and used the radiometric diameter derived by Enriquez et al (2010) to calculate average densities which vary from 1.3 to 3.7 g/cm 3 . In contrast with Marchis et al (2008a), these orbits give a realistic density for the (3749) Balam system, since this asteroid is classified as an S-type asteroid (Marchis et al 2011).…”