# A dark asteroid family in the Phocaea region

## TL;DR

This paper reports the discovery of a new dark asteroid family in the Phocaea region, analyzes its properties, estimates its age, and explores its potential impact on Earth.

## Contribution

It identifies and characterizes the Tamara family, a dark asteroid group in the Phocaea region, using physical data and dynamical simulations, revealing new insights into small asteroid composition and evolution.

## Key findings

- The Tamara family has a steeper magnitude distribution slope than the overall Phocaea region.
- Sub-kilometer dark Phocaeas are as numerous as bright S-type asteroids.
- Estimated age of the Tamara family is approximately 264 million years.

## Abstract

We report the discovery of a new asteroid family among the dark asteroids residing in the Phocaea region the Tamara family. We make use of available physical data to separate asteroids in the region according to their surface reflectance properties, and establish the membership of the family. We determine the slope of the cumulative magnitude distribution of the family, and find it to be significantly steeper than the corresponding slope of all the asteroids in the Phocaea region. This implies that sub-kilometer dark Phocaeas are comparable in number to bright S-type objects, shedding light on an entirely new aspect of the composition of small Phocaea asteroids. We then use the Yarkovsky V-shape based method and estimate the age of the family to be 264$\pm$43 Myr. Finally, we carry out numerical simulations of the dynamical evolution of the Tamara family. The results suggest that up to 50 Tamara members with absolute magnitude H<19.4 may currently be found in the near-Earth region. Despite their relatively small number in the near-Earth space, the rate of Earth impacts by small, dark Phocaeas is non-negligible.