A new non-convex model of the binary asteroid 90 Antiope obtained with the SAGE modelling technique

TL;DR

This paper introduces a novel non-convex model of the binary asteroid 90 Antiope using an advanced SAGE technique, providing detailed shape, size, and density estimates from photometry and occultation data.

Contribution

A new variant of the SAGE algorithm capable of modeling binary asteroid systems from disk-integrated photometry is developed and applied to 90 Antiope.

Findings

Confirmed the asteroid's pole orientation and orbital period.

Derived sizes and separation distance of the binary components.

Estimated the system's total mass and density.

Abstract

We present a new non-convex model of the 90 Antiope binary asteroid, derived with a modified version of the SAGE (Shaping Asteroids with Genetic Evolution) method using disk-integrated photometry only. A new variant of the SAGE algorithm capable of deriving models of binary systems is described. The model of 90 Antiope confirms the system's pole solution ($\lambda=199^{\circ}$, $\beta=38^{\circ}$, $\sigma=\pm5^{\circ}$) and the orbital period ($16.505046 \pm 0.000005$ h). A comparison between the stellar occultation chords obtained during the 2011 occultation and the projected shape solution has been used to scale the model. The resulting scaled model allowed us to obtain the equivalent radii ($R_{1}=40.4\pm0.9$ km and $R_{2}=40.2\pm0.9$ km) and the distance between the two system components ($176\pm4$ km), leading to a total system mass of ($9.14\pm0.62$)$\cdot10^{17}$ kg. The non-convex shape description of the components permitted a refined calculation of the components' volumes, leading to a density estimation of $1.67\pm0.23$ g cm$^{-3}$. The intermediate-scale features of the model may also offer new clues on the components' origin and evolution.