# A new non-convex model of the binary asteroid (809) Lundia obtained with the SAGE modelling technique

## TL;DR

This paper introduces a novel non-convex model of asteroid (809) Lundia using the SAGE technique, providing refined physical parameters, orbit details, and insights into its origin and evolution.

## Contribution

It presents the first non-convex shape model of Lundia derived solely from photometry, improving previous pole solutions and orbital parameters.

## Key findings

- Refined orbit pole coordinates and period.
- Estimated density and porosity of the asteroid.
- Enhanced shape model revealing features related to origin.

## Abstract

We present a new non-convex model of the binary asteroid (809) Lundia. A SAGE (Shaping Asteroids with Genetic Evolution) method using disc-integrated photometry only was used for deriving physical parameters of this binary system. The model of (809) Lundia improves former system's pole solution and gives the ecliptic coordinates of the orbit pole - $\lambda=122^{\circ}$, $\beta=22^{\circ}$, $\sigma=\pm5^{\circ}$ - and the orbital period of $15.41574 \pm 0.00001$ h. For scaling our results we used effective diameter of $D_{eff} = 9.6 \pm 1.1$ km obtained from Spitzer observations. The non-convex shape description of the components permitted a refined calculation of the components' volumes, leading to a density estimation of $2.5\pm0.2$ g/cm$^3$ and macroporosity of 13-23\%. The intermediate-scale features of the model may also offer new clues on the components' origin and evolution.