The Eos family halo

TL;DR

This study investigates the origin and age of the Eos asteroid family halo, revealing it results from Yarkovsky-driven escape and resonances, with an estimated age of 1.5 to 1.9 billion years and specific disruption geometry.

Contribution

It provides a dynamical model that estimates the Eos family age and explains the halo's origin through Yarkovsky effects and resonances, refining previous age estimates.

Findings

Halo formed by bodies escaping due to Yarkovsky drift

Estimated family age of 1.5 to 1.9 Gyr

Disruption occurred at true anomaly 120-180 degrees

Abstract

We study K-type asteroids in the broad surroundings of the Eos family because they seem to be intimately related, according to their colours measured by the Sloan Digital Sky Survey. Such `halos' of asteroid families have been rarely used as constraints for dynamical studies to date. We explain its origin as bodies escaping from the family `core' due to the Yarkovsky semimajor-axis drift and interactions with gravitational resonances, mostly with the 9/4 mean-motion resonance with Jupiter at 3.03 AU. Our N-body dynamical model allows us to independently estimate the age of the family 1.5 to 1.9 Gyr. This is approximately in agreement with the previous age estimate by Vokrouhlick\'y et al. (2006) based on a simplified model (which accounts only for changes of semimajor axis). We can also constrain the geometry of the disruption event which had to occur at the true anomaly f =~ 120 to 180 deg.