Spin states of asteroids in the Eos collisional family

TL;DR

This study derives and updates 3D shape models and rotation states for 31 Eos family asteroids, providing insights into their physical properties and the influence of the YORP effect, with implications for collisional evolution models.

Contribution

The paper presents new and revised shape models for 31 Eos family asteroids, expanding the dataset for analyzing asteroid physical properties and evolution.

Findings

Rotation states of smaller asteroids are heavily influenced by YORP effect.

Large asteroids have retained their original rotation states since family formation.

A shape model and bulk density for interloper asteroid (423) Diotima are provided.

Abstract

Eos family was created during a catastrophic impact about 1.3 Gyr ago. Rotation states of individual family members contain information about the history of the whole population. We aim to increase the number of asteroid shape models and rotation states within the Eos collision family, as well as to revise previously published shape models from the literature. Such results can be used to constrain theoretical collisional and evolution models of the family, or to estimate other physical parameters by a thermophysical modeling of the thermal infrared data. We use all available disk-integrated optical data (i.e., classical dense-in-time photometry obtained from public databases and through a large collaboration network as well as sparse-in-time individual measurements from a few sky surveys) as input for the convex inversion method, and derive 3D shape models of asteroids together with their rotation periods and orientations of rotation axes. We present updated shape models for 15 asteroids and new shape model determinations for 16 asteroids. Together with the already published models from the publicly available DAMIT database, we compiled a sample of 56 Eos family members with known shape models that we used in our analysis of physical properties within the family. Rotation states of asteroids smaller than ~20 km are heavily influenced by the YORP effect, whilst the large objects more or less retained their rotation state properties since the family creation. Moreover, we also present a shape model and bulk density of asteroid (423) Diotima, an interloper in the Eos family, based on the disk-resolved data obtained by the Near InfraRed Camera (Nirc2) mounted on the W.M. Keck II telescope.